Degradation of Fluorotelomer-Based Polymers ... - ACS Publications

Subscriber access provided by UNIV OF CALIFORNIA SAN DIEGO LIBRARIES

Article

The degradation of fluorotelomer-based polymers contributes to the global occurrence of fluorotelomer alcohol and perfluoroalkyl carboxylates: A combined dynamic substance flow and environmental fate modelling analysis Li Li, Jianguo Liu, Jianxin Hu, and Frank Wania Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.6b04021 • Publication Date (Web): 17 Mar 2017 Downloaded from http://pubs.acs.org on March 18, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31

Environmental Science & Technology

1

The degradation of fluorotelomer-based polymers contributes to the global occurrence of fluorotelomer

2

alcohol and perfluoroalkyl carboxylates: A combined dynamic substance flow and environmental fate

3

modelling analysis

4 5

Li Li,1,2,* Jianguo Liu,1,* Jianxin Hu,1 Frank Wania2

6

1. College of Environmental Sciences and Engineering, Peking University, 5 Yiheyuan Road, Beijing,

7

100871, P.R. China

8

2. Department of Physical and Environmental Sciences, University of Toronto Scarborough, 1095

9

Military Trail, Toronto, Ontario M1C 1A4, Canada

10 11

Correspondence to:

12

* L. Li: College of Environmental Sciences and Engineering, Peking University, 5 Yiheyuan Road,

13

Beijing, 100871, P.R. China; E-mail: [email protected], and, [email protected]; Phone: 86

14

10 62753746;

15

** J. Liu: College of Environmental Sciences and Engineering, Peking University, 5 Yiheyuan Road,

16

Beijing, 100871, P.R. China; E-mail: [email protected]; Phone: 86 10 62759075.

17 18

TOC Art

19 20

1

ACS Paragon Plus Environment


Page 2 of 31

21

Abstract

22

Using coupled dynamic substance flow and environmental fate models, CiP-CAFE and BETR-Global,

23

we investigated whether degradation of side-chain fluorotelomer-based polymers (FTPs), mostly in

24

waste stocks (i.e., landfills and dumps), serves as a long-term source of fluorotelomer alcohols (FTOHs)

25

and perfluoroalkyl carboxylates (PFCAs) to the global environment. The modelling results indicate that,

26

in the wake of the worldwide transition from long-chain to short-chain products, in-use stocks of C8

27

FTPs will peak and decline afterwards while the in-use stocks of C6 FTPs and waste stocks of both

28

FTPs will generally grow. FTP degradation in waste stocks is making an increasing contribution to

29

FTOH generation, the bulk of which readily migrates from waste stocks and degrades into PFCAs in the

30

environment; the remaining part of the generated FTOHs degrade in waste stocks, which makes those

31

stocks reservoirs that slowly release PFCAs into the environment over the long run because of the low

32

leaching rate and extreme persistence of PFCAs. Short-chain FTPs have higher relative release rates of

33

PFCAs from waste stocks than long-chain ones. Estimates of in-use and waste stocks of FTPs were

34

more sensitive to the selected lifespan of finished products while those of emissions of FTOHs and

35

PFCAs were more sensitive to the degradation half-life of FTPs in waste stocks. Our preliminary

36

calculations highlight the need for environmentally sound management of obsolete FTP-containing

37

products into the foreseeable future.

2


Page 3 of 31


38

Introduction

39

Constituting almost 80% of the market of fluorotelomer-based substances worldwide,1 side-chain

40

fluorotelomer-based polymers (FTPs) have been applied as durable water repellents (DWRs) on a wide

41

range of finished textiles, fabrics, carpets and garments,2,

42

packaging industries, as well as other miscellaneous applications.3 The FTPs provide continuous water,

43

oil and stain resistances for commercial finished products throughout the product lifespans, during

44

which FTPs might migrate into the environment because of abrasion and weathering. Afterwards, a

45

considerable amount of FTPs enters the waste stream and accumulate in waste stocks such as landfills

46

and dumps where aged FTPs undergo degradation on the time scale of decades or longer to generate

47

various per- and polyfluoroalkyl substances (PFASs).4 Recent experimental studies have demonstrated

48

that this process comprises a series of sequential stepwise transformations, which first form

49

non-polymeric fluorotelomer-based substances like fluorotelomer alcohols (FTOHs), followed by a

50

variety of immediate degradation products such as saturated and unsaturated fluorotelomer carboxylates,

51

and arrive at perfluoroalkyl carboxylates (PFCAs) as ultimate degradation products.5-7 During the

52

degradation, both the intermediate and terminal degradation products may demonstrate adverse

53

environmental effects.8-10

3

as oil/grease repellents in paper and

54

Despite the consensus that FTP degradation contributes to the occurrence of FTOHs and PFCAs

55

worldwide, the magnitude and temporal evolution of the problem have not yet been well elucidated and

56

are thus still being contested.11 Several earlier modelling studies11-14 have attempted to evaluate the

57

future worldwide releases of FTOHs and/or PFCAs from FTP degradation; however, these studies

58

possessed different scopes and relied on distinct assumptions and methodologies. First, there is a lack of

59

consistent, holistic consideration of mass flows of FTPs in both (i) in-use stocks during product service

60

life and (ii) waste stocks (i.e., landfills and dumps) during the waste disposal phase. For instance, Wang

61

et al.11 assumed an immediate end of FTOH releases once in-use stocks of FTPs are depleted, because

62

they postulated that all obsolete FTP-containing finished products will be “properly treated (i.e., safely

63

landfilled or incinerated) and no longer available for degradation”.11 This assumption contrasts with the

3



Page 4 of 31

64

stated expectation that FTP degradation in landfills “potentially constitutes a large long-term

65

environmental load”4 for these compounds. In fact, the potential for degradation of FTPs in waste stocks

66

has been confirmed experimentally,4, 15 and considerable releases of FTOHs and PFCAs via landfill

67

leachates and gases have been observed in a range of field studies.16, 17 Coping with this situation

68

necessitates a better “understanding of the mass flow of side-chain fluorinated polymers during their

69

whole life-cycle, including in landfills”,11 as stated by Wang et al. Second, there are substantial

70

variability and uncertainty associated with important input parameters. For example, (i) the lifespan of

71

finished products [hereafter “product lifespan (LS)”], and (ii) the degradation half-life of FTPs in the

72

environment or waste stocks [hereafter “degradation half-life (HL)”], have been identified as two key

73

parameters determining the contribution of FTP degradation.11 However, the LS adopted in earlier

74

studies ranges from 10 yrs18 to 50 yrs13, while the HL derived from different degradation experiments

75

spans 2 orders of magnitude from 10 – 17 yrs6 to 1200 – 1700 yrs5. How different LS and HL values

76

influence global annual FTOH releases from FTP degradation has been studied previously using

77

empirical emission factors.11 Limited consideration was given to how and why those variables affect

78

processes throughout the product lifecycle (e.g. in-use and waste stocks) and/or in the environment (e.g.,

79

FTP degradation in waste stocks vs. after being released into the environment). In this situation,

80

process-oriented models can contribute to a better mechanistic understanding of the complicated

81

relationship between key parameters and the estimated release of generated FTOHs and PFCAs. Such an

82

approach is also helpful for identifying the most influential parameters requiring accurate quantification

83

in future studies.

84

In this contribution, we combine a dynamic substance flow analysis model, CiP-CAFE, and an

85

environmental fate model, BETR-Global, to mechanistically simulate the temporal evolution of in-use

86

and waste stocks of FTPs, and the environmental releases of FTOHs and PFCAs from the degradation of

87

FTPs. The influence of variations in LSs and HLs on model predictions is explored with four scenarios.

88

We seek to preliminarily characterize the current and future contributions of FTP degradation, in

89

particular during the waste disposal phase, to the releases of FTOHs and PFCAs worldwide. Findings in

4


Page 5 of 31


90

this study may provide a long-term overview of the stocks and mass flows of FTPs throughout the

91

lifecycle, as well as complement the current understanding of sources of FTOHs and PFCAs.

92

Methods

93

Applications, substances and terminology

94

Although fluorotelomer-based substances have found use as ingredients (see terminology in Text S1

95

in the Supporting Information) in a multitude of consumer products, for simplification three major

96

applications (APs) can be roughly categorized based on lifespan characteristics:18, 19 FTPs serve as

97

DWRs

98

fluorotelomer-based derivatives serve as surfactants for treating consumer products (representing all

99

uses with continuous releases throughout lifespan) (AP2) and additives in aqueous film forming foams

100

(AFFFs, representing all uses with both accidental releases at accidents and intensive discharge at the

101

end of shelf life) (AP3). Here we did not consider FTP use in paper and packaging industries due to

102

absence of market statistics. Since technical PFASs are usually present and consumed in above

103

applications as mixtures of homologues with different chain-lengths or derivatives with various

104

functional groups, we defined “equivalents” to collectively describe a series of similar PFASs with the

105

same featured moiety but without considering their differences in molecular weights, physicochemical

106

properties and degradation kinetics. In this study, the following three categories of PFAS-equivalents

107

were considered (Figure 1):

on

finished

textiles,

fabrics,

carpets

and

garments

(AP1),

while

non-polymeric

108

(I) side-chain FTP-equivalents (respective 4:2, 6:2, 8:2, 10:2 and 12:2 homologues were considered

109

in this study), which refer to a collection of side-chain fluorotelomer-based acrylate, methacrylate,

110

urethane and other polymers. FTP-equivalents are used as ingredients in DWRs in AP1 (denoted as

111

FTPs) and have the potential to degrade into FTOHs and further PFCAs;

112

(II) FTOH-equivalents (respective 4:2, 6:2, 8:2, 10:2 and 12:2 homologues), which refer to a

113

collection of (i) FTOHs, and (ii) fluorotelomer-derived non-polymers (e.g., fluorotelomer acrylates,

114

FTA), the degradation of which generates FTOHs as intermediates.20 FTOH-equivalents can be released

115

into the environment as residuals in consumer products in the three APs (denoted as resFTOHs, Figure

5



Page 6 of 31

116

1), and as degradation products from the degradation of FTPs (denoted as degFTOHs, Figure 1) in both

117

waste stocks and the environment;

118

(III) PFCA-equivalents (respective C4 – C12 homologues), which refer to both perfluoroalkyl

119

carboxylic acids and corresponding carboxylates. In this study, we consider releases of

120

PFCA-equivalents into the environment as impurities in consumer products in the three APs (denoted as

121

impPFCAs, Figure 1), and as degradation products from both resFTOHs (denoted as deg-resPFCAs,

122

Figure 1) and degFTOHs (denoted as deg-degPFCAs, Figure 1) in waste stocks and the environment.

123

The main objectives of this study are: (i) to simulate the temporal evolution of in-use and waste

124

stocks of FTPs in AP1, and (ii) to investigate the contribution of FTP degradation to formation/release of

125

degFTOHs and deg-degPFCAs (Figure 1). In addition, we also simulated the direct releases of resFTOH

126

residuals and impPFCA impurities, as well as the formation of deg-resPFCAs, in all three APs for

127

comparison. We recognized that a small amount of FTOHs can also be generated from degradation of

128

non-polymeric FT-based substances, e.g., polyfluoroalkyl phosphate esters (PAPs) in AP2 (Figure 1);21,

129

22

130

market information renders estimating their contribution highly uncertain; and (ii) the release is much

131

lower than degFTOHs and resFTOHs according to our preliminary calculation (Text S2 in SI). There are

132

a number of other PFCA sources (Figure 1),18 such as the intentional uses of PFCAs as processing aid in

133

fluoropolymer production, and the transformation of non-polymeric fluorotelomer-based derivatives

134

(e.g., fluorotelomer sulfonamido betaines and fluorotelomer thioamido sulfonates as ingredients in

135

AFFFs,23 which normally do not transform to FTOHs24). Estimating PFCA releases from these sources

136

is beyond the scope of this work. Meanwhile, the lack of detailed information prevents consideration of

137

the presence and releases of other minor residuals, e.g., perfluoroalkyl iodides and fluorotelomer

138

iodides.25

we did not considered their contribution to the total FTOH release because (i) inadequate available

6


Page 7 of 31


139

Figure 1 Transformation of FTPs, FTOHs and PFCAs in the environment and waste stocks [R' = H or

140

methyl group; R = H or (meth)acrylic group]. Arrows in solid line denote the substance flows quantified

141

in this work: estimating stocks of FTPs, and annual releases of degFTOHs and deg-degPFCAs, are the

142

main objectives (denoted as blue and red shadings); annual releases of resFTOHs, deg-resPFCA and

143

impPFCAs are also calculated for comparison. Arrows in dashed line represent substance flows not

144

quantified. The box “other PFCA sources” includes all PFCAs sources in Wang et al.18 other than the

145

three considered here.

146 147

Overview of modelling strategy

148

Figure 2 summarizes the conceptual modelling strategy adopted in this study. In a first step, the

149

mechanistic anthropospheric fate model, CiP-CAFE, is used to calculate time-variant in-use and waste

150

stocks of FTPs worldwide for the period 1960 to 2040. The rationale for, and description of, the model

151

have been detailed previously26 and are briefly provided in Text S2.1. Here, substance accumulation in

152

the process labeled “in-service (LC5)” in CiP-CAFE is used to describe in-use stocks, while waste 7



Page 8 of 31

153

stocks are represented by substance accumulation in the processes termed “landfill (WD1)” and

154

“dumping and simple landfill (WD3)” (Text S2.1).

155

To feed the CiP-CAFE model, we first calculated the annual production of FTPs on a

156

homologue-basis in individual CiP-CAFE regions. The global annual production of total technical

157

fluorotelomer-based substances (Figure S1)18,

158

non-polymeric substances (for use in APs2 and 3) based on a reported ratio of 80%:20%.1 Furthermore,

159

because technical fluorotelomer-based substances are mixtures of different homologues of ingredients,

160

residuals and impurities, we divided these mixtures according to literature-reported homologue

161

composition (for ingredients) and contents (for residuals and impurities) in long-chain (C8-based) and

162

short-chain (C6-based) products (Table S1). To reflect a worldwide transition from long-chain (C8-based)

163

products to their short-chain (C6-based) alternatives since 2006, we assumed that the fraction of

164

long-chain products in total fluorotelomer-based products decreased linearly from 100% before 2005 to

165

0% after 2016. This simplified assumption could underestimate the amounts of long-chain products in

166

developing countries (e.g., in China27) as domestic production and use of long-chain products are still

167

ongoing in these countries. Those in developed countries can be underestimated as well if they

168

continued importing long-chain products from developing countries; however, the underestimation

169

seems quite moderate, because in most cases the imports are prohibited in developed countries in

170

compliance with their regional or national trade regulations. For example, a sampling campaign in

171

Norway during 2012 – 2013 indicated that “the emissions from consumer products imported from China

172

account for 1.5 per cent of the discharges of PFOA to wastewater influents and 0.3 per cent of the

173

emissions of 8:2 FTOH to air”.28 Our global production estimates on a homologue-basis are believed to

174

be reliable because, for example, the estimate for C8 FTPs for the period 1970 – 2007 (41.4 – 49.7 kt)

175

compares favorably with a previous report of 34.5 kt (32 kt of acrylate5 plus 2.5 kt of urethane12

176

polymers). While the absolute amounts of production volumes are admittedly uncertain, they do not

177

hinder us to arrive at meaningful conclusions in the following because (i) we focus our attention on

178

temporal trends in the relative importance of individual sources, and (ii) both CiP-CAFE and

19, 27

were split into FTPs (for use in AP1) and

8


Page 9 of 31


179

BETR-Global are linear models which enable scaling all absolute outputs to production volumes if

180

updated production information is available in the future. Next, the global annual production of FTPs on

181

a homologue-basis were attributed into the regions defined in CiP-CAFE: ~5% in Western Europe

182

(RE5),29 50% in North America (RE6),30 ~15% in China (RE1, only after 2009),27 and the remainder in

183

Japan/South Korea (RE2) (see the locations of manufacturers in Figure SF-1).

184

CiP-CAFE sketched geographical redistributions of the regional FTP production via international

185

trade among the CiP-CAFE regions, using formulated concentrated DWRs (Table S2) as a surrogate for

186

the FTPs subjected to textile/fabric finishing after “formulation (LC2)”, and clothing (Table S2) as a

187

surrogate for the FTPs in finished textile/fabric products reaching consumers after “processing (LC3)”.

188

Here we assumed that FTPs were imported to or exported from a region in the same proportion as the

189

two respective surrogates, because international statistics enabling discrimination between

190

FTP-containing and FTP-free commercial products were no available. In order to investigate the

191

influence of different product lifespans (LSs) of finished textile/fabric products in AP1 and degradation

192

half-lives (HLs) of FTPs in waste stocks on our model results, we ran CiP-CAFE using four scenarios: (I)

193

LS=10 yrs and HL=75 yrs, (II) LS=10 yrs and HL=1500 yrs, (III) LS=50 yrs and HL=75 yrs, and (IV)

194

LS=50 yrs and HL=1500 yrs. Emission and waste factors used in the CiP-CAFE calculation are

195

tabulated in Table S4. Here, we assumed that FTPs are neither released nor degraded during the

196

product’s lifespan, as there is substantial difference in the observed reduction in oil- and

197

water-repellency or FTP weight among diverse (co)polymer compositions, finishing treatments, and

198

textile surface properties in a multitude of laundering or weathering studies.2, 31-33 While many of the

199

studies reported negligible FTP losses (from not observed to < 2%) in a limited test time,31-33 no

200

information is available for textile/fabric use over a decadal time scale. At the end of their lifespan,

201

obsolete FTP-containing finished textile/fabric products in AP1 enter the waste stream, the distribution

202

between different disposal approaches following the time-variant regional waste disposal ratios

203

(WDRs)26 supplied within CiP-CAFE. Degradation of FTPs in the waste stocks was calculated using the

9



Page 10 of 31

204

four assumed HLs. Emissions of FTPs from the waste stocks were assumed to be negligible because

205

FTPs are neither volatile nor soluble.

206

Figure 2 Schematic of the modelling strategy in this study. Green boxes indicate model outputs while

207

blue boxes indicate data collected from the literature or calculated from model outputs. Red diamonds

208

indicate a calculation using models.

209 10


Page 11 of 31


210

The second step comprises another series of CiP-CAFE runs to estimate the global annual releases

211

of FTOHs from waste stocks during the period 1960 – 2040 (Step 2 in Figure 2). Formation of

212

degFTOHs was calculated from the degradation of (i) FTPs in two waste stocks and (ii) FTPs released

213

into the environment, by assuming that FTOHs are formed from FTPs with the same perfluorinated

214

chain length with a yield of 100%.13 The formed degFTOHs in waste stocks, together with the annual

215

production of resFTOHs in all three APs, served as inputs for the CiP-CAFE calculation. In Step 2,

216

parameters for AP1 were assumed the same as those used in Step 1, and consumer products in APs 2 and

217

3 were assumed to be domestically consumed with fixed product lifespans (Table S3). Table S5 tabulates

218

partitioning coefficients (KAW, KOW) for FTOHs and degradation half-lives of FTOHs in various

219

compartments. Internal energies (∆UOA, ∆UAW, ∆UOW) for adjusting the cited partitioning coefficients to

220

different temperature were calculated based on the method in ref34. Activation energies for adjusting the

221

degradation half-lives to different temperature were default values in CiP-CAFE and BETR-Global (20

222

kJ mol-1 for water and wastewater treatment plant; and 30 kJ mol-1 for soil, landfill, and simple landfill

223

and dumping). Emission and waste factors used in the CiP-CAFE calculation are tabulated in Table S4.

224

Fate and transformation of FTOHs in the waste stocks are calculated by the Model for Organic

225

Chemicals in Landfills (MOCLA) module contained in CiP-CAFE.

226

In order to evaluate the CiP-CAFE results for the different scenarios and to calculate FTOH

227

transformation in the environment, we performed global environmental fate simulations for total FTOHs

228

using the BETR-Global model (Step 3 in Figure 2). This model is described in detail in refs.35, 36 and

229

briefly in Text S2.2. The CiP-CAFE-derived annual releases of FTOHs, and the amounts of FTOHs

230

formed during the degradation of FTPs in the environment, were combined and allocated to the 15° × 15°

231

BETR-Global cells as in ref.26. Time-variant atmospheric concentrations of 8:2 and 6:2 FTOH calculated

232

by BETR-Global for different scenarios were then compared with monitoring data reported in the

233

literature.

234

Then, the annually degraded amounts of resFTOHs and degFTOHs in both waste stocks (calculated

235

by CiP-CAFE) and the environment (calculated by BETR-Global) were fractionally converted into

11



Page 12 of 31

236

deg-resPFCAs and deg-degPFCAs, respectively, based on the median values of the estimated molar

237

yields (mol %) for the transformation of n:2 FTOH to different PFCA homologues: the degradation of

238

n:2FTOH yields 1 mol% for each PFCA homologue with (n-1), (n-2), (n-3) carbons and 5 mol% for

239

each PFCA homologue with n and (n+1) carbons.18 The yields correspond to homologue-specific mass

240

yields of 4.1% – 6% on a FTOH basis, which agree well with those used in previous modelling

241

studies.37-39 Admittedly, the PFCA yields could be somewhat conservative, because we considered

242

neither degradation intermediates of FTOHs (e.g., fluorotelomer aldehydes),38 nor the PFCA formation

243

from FTP degradation intermediates other than FTOHs (e.g., newly identified 7:2 sFTOH

244

[F(CF2)7CH(OH)CH3] in bio-degradation of 8:2 fluorotelomer acrylate),20 due to insufficient

245

information on the multimedia partitioning behavior and degradation kinetics of these intermediates.

246

Meanwhile, we did not consider the PFCA formation in the environment resulted from further

247

transformation of the degradation intermediates released from waste stocks. Finally, the converted

248

deg-resPFCAs and deg-degPFCAs in waste stocks, along with the annual production of impPFCAs in all

249

three APs, served as inputs for a third set of CiP-CAFE calculations (Step 4 in Figure 2) to calculate

250

time-variant emissions of total fluoroteolmer-related PFCAs for the period 1960 – 2040. Parameters for

251

consumer products in three APs are the same as those used in Step 2. Emission and waste factors used

252

are given in Table S4; partitioning coefficients for neutral PFCAs and degradation half-lives of PFCAs

253

in various compartments are tabulated in Table S6.

254

Results and discussion

255

Temporal evolution of estimated stocks and releases

256

Figure 3 presents the calculated time-variant global in-use and waste stocks of FTPs, as well as

257

annual releases of degFTOHs and deg-degPFCAs into the environment, for long-chain C8-compounds

258

(Figures 3a to 3d) and short-chain C6-compounds (Figures 3e to 3h) under the four scenarios.

12


Page 13 of 31


259

Figure 3 Estimated ranges of global in-use stocks (a and e) and waste stocks (b and f) of FTPs, annual

260

releases of degFTOHs (c and g) and deg-degPFCAs (d and h) for C8- (from a to d) and C6-compounds

261

(from e to h) from 1960 – 2040 under the four simulation scenarios: (I) LS=10 yrs and HL=75 yrs, (II)

262

LS=10 yrs and HL=1500 yrs, (III) LS=50 yrs and HL=75 yrs, and (IV) LS=50 yrs and HL=1500 yrs.

263

The global annual releases of resFTOHs are presented in grey shading in panels c and g for comparison.

264 265

Within the given time frame from 1960 to 2040, for both C8 and C6 FTPs, scenarios based on long

266

LS (III and IV) yield larger in-use stocks (Figures 3a and 3e) but smaller waste stocks (Figures 3b and

267

3f), because longer use implies slower transfer to waste; in scenarios with long HL (II and IV), less

268

FTPs are degraded, resulting in larger waste stocks (Figures 3b and 3f). In general, both the in-use and

269

waste stocks peak or plateau when inflows and outflows are similar in magnitude. For example, in-use

270

stocks of C8 FTPs (Figure 3a) peaked at 21 – 25 kt in 2010 (Scenarios I and II) or 49 – 59 kt in 2014

271

(Scenarios III and IV) when increasing rates of discarding matched decreasing rates of new use (the

272

latter a result of the phase-out of C8 FTPs). Likewise, in-use stocks of C6 FTPs (Figure 3d) are expected

273

to level off at 59 – 70 kt after 2027 (Scenario I and II) when the increasing discard rates catch up with

274

the annual rates of new use of C6-based finished products (which is assumed constant according to 13



Page 14 of 31

275

annual production data in ref.18). Furthermore, for both the in-use and waste stocks, the difference in

276

stock size due to a change in LS (i.e., Scenarios I and II vs. Scenarios III and IV) is more notable than

277

that due to a change in HL (i.e., Scenarios I and III vs. Scenarios II and IV). This indicates that, when

278

both are at possibly realistic levels, product lifespan is more crucial than degradation half-life to an

279

accurate description of FTPs stocks.

280

The estimated annual multimedia releases of degFTOHs in Figures 3c and 3g are the sum of

281

degFTOHs (i) released from waste stocks and (ii) transformed from FTPs released in the environment.

282

The releases of degFTOHs via the former route varied over three orders of magnitude among the

283

scenarios, with the calculated cumulative releases of 8:2 degFTOHs ranging from 11.5 – 13.8 t under

284

Scenario IV to 1700 – 2038 t under Scenario I and those of 6:2 degFTOHs ranging from 0.7 – 0.9 t

285

under Scenario IV to 126 – 152 t under Scenario I by 2015. By contrast, the releases of degFTOHs via

286

the latter route were quite similar for the different scenarios, namely 22 – 37 t for 8:2 degFTOHs and 3 –

287

6 t for 6:2 degFTOHs by 2015. Consequently, the relative importance of the two sources of degFTOHs

288

varied considerably between the four scenarios. Furthermore, the atmosphere was predicted to receive

289

the dominant share (97% – 99%) of degFTOHs. Volatilization with landfill gas is the predominant route

290

by which degFTOHs enter the atmosphere. This finding echoes Washington et al.’s assessment that

291

“landfills are not airtight” and “commercial FTPs potentially might be a source of fluorotelomers to the

292

environment even after disposal”.4

293

For both 6:2 and 8:2 degFTOHs, the annual releases in scenarios with short HL (I and III) are

294

almost 1 order of magnitude higher than in those using long HL (II and IV); that is, the estimated annual

295

releases of degFTOHs are affected to a larger extent by a change in HL – which is in contrast to the

296

sensitivity of stocks to LS – when both the HL and LS vary within a realistic range. Annual releases of

297

8:2 degFTOH are anticipated to peak around 2022 in Scenario I and decline afterwards, due to the rapid

298

depletion of C8 FTPs waste stocks in this scenario (Figure 3b); while in other scenarios releases of both

299

8:2 and 6:2 degFTOHs are projected to keep increasing throughout the simulation period.

14


Page 15 of 31


300

The estimated annual multimedia releases of deg-degPFCAs in Figures 3d and 3h are the sum of

301

deg-degPFCAs (i) liberated from waste stocks and (ii) transformed from the degFTOHs released into the

302

environment. The latter is currently dominant, with contributions to cumulative releases of 89% – 95%

303

for deg-degPFOA and 68% – 97% for deg-degPFHxA by 2015 under different scenarios. The dominance

304

of the latter route is understandable as our calculations find that (i) 97% – 99% of degFTOHs volatilize

305

with landfill gas into the atmosphere, where 94% – 97% of them degrade into deg-degPFCAs within a

306

year, (ii) by contrast, less than 3% of the deg-degPFCAs generated from the degFTOHs remaining in

307

waste stocks are annually released via leachate (Table S6). That leaching is not an efficient route for

308

delivering a significant amount of deg-degPFCAs into the environment in the short term, is mostly

309

because the area-specific leachate flow, which equates to the average annual precipitation in a region (~

310

1 m yr-1),26 is too small. Likewise, Yan et al.16 estimated that annually 1.8 ± 3 t of PFOA were leached

311

from landfills across China based on samples collected in 2013, which accounts for a mere ~3% of the

312

annual national emissions of PFOA (< 60 t in 201227) in China. In fact, the inefficiency of leachate

313

releases is also the case for a wider range of soluble compounds such as phenol.40 The above result

314

implies that, due to such a “trickle”, the residence time of deg-degPFCAs generated in waste stocks can

315

reach multiple decades if not centuries, i.e., waste stocks are a reservoir slowly releasing deg-degPFCAs.

316

Figure S2 presents an additional long-term calculation to 2100 of annual releases of deg-degPFOA from

317

the two routes under Scenario I. While the formation of deg-degPFCAs in the environment will

318

moderately decline after 2020 due to the depletion of C8 FTP waste stocks (Figure 3b), the releases of

319

deg-degPFCAs from waste stocks will increase throughout the simulation period. After 2090, the annual

320

releases from the two routes will be comparable.

321

Interestingly, the calculation by the MOCLA module in CiP-CAFE suggests that short-chain PFCA

322

homologues are almost 2 orders of magnitude more likely than long-chain ones to migrate from waste

323

stocks to the hydrosphere (Table S6). This is because short-chain PFCA homologues are more water

324

soluble and adsorb less to landfill organic matter (i.e., lower log KOW in Table S6). If we further take into

325

account the migration of precursors, i.e., short-chain FTOH homologues volatilize more from waste

15



Page 16 of 31

326

stocks to the atmosphere due to their higher vapor pressure,41 we can definitely expect higher relative

327

release rates of short-chain deg-degPFCAs than long-chain deg-degPFCAs. For example, our

328

calculations demonstrate that, during the simulation period 1960 – 2040, the cumulative consumption of

329

C8 FTPs (55 – 66 kt) is estimated to be 25-fold higher than that of C4 FTPs (2.1 -2.5 kt), yet the

330

cumulative releases of deg-degPFOA (280 – 347 t) are only 6-fold higher than those of deg-degPFBA

331

(data not shown in Figure 3). That short-chain deg-degPFCAs are more readily released implies that the

332

use of short-chain FTPs may have a more significant immediate influence on the environment, while

333

long-chain FTPs are more likely to be a long-term threat.

334

Analogous to the sensitivity of degFTOHs above, HL was identified as the factor with the most

335

influence on the annual releases of deg-degPFCAs, as those releases are considerably higher in

336

Scenarios I and III (Figures 3d and 3h). Scenario I led to the highest release of deg-degPFCAs. The

337

annual releases of deg-degPFOA and deg-degPFHxA are predicted to increase throughout the simulation

338

period, except for Scenario I in which releases of deg-degPFOA reach a plateau (Figure 3d).

339

Rising contributions of FTP degradation to global FTOH releases

340

In addition to the amount of FTOHs released as a result of FTP degradation (degFTOHs), the

341

CiP-CAFE model also estimated the amount of FTOHs released as residuals (resFTOHs, grey shading in

342

Figures 3c and 3g). The annual releases of 8:2 resFTOH are estimated to have substantially increased

343

since the 1990s with a peaked around 2007 (the year after the worldwide transition from

344

long-chain-based commercial products to their short-chain alternatives began); those of 6:2 resFTOH

345

have increased steadily until reaching a plateau in 2007. Our estimates agree with earlier studies. For

346

example, our annual 8:2 resFTOH emissions (80 – 320 t yr-1 for the period 2000 – 2004 on average) are

347

generally similar to those reported by Prevedouros et al.19 (~100 t yr-1 for 2002), Wania37 (100 – 200 t

348

yr-1 for 2000 – 2005) and Schenker et al.39 (60 – 155 t yr-1 for 2000 – 2005); they are also within the

349

range of ~0.5 to ~ 300 t yr-1 which can be calculated from the data presented in Wang et al.18

350

The relative contributions of degFTOHs and resFTOHs to the total releases change over time. 8:2

351

resFTOH dominated the annual total emissions of 8:2 FTOH prior to approximately 2010, its

16


Page 17 of 31


352

contribution exceeding that of 8:2 degFTOH by a factor of 2 (Scenario I) to 2 orders of magnitude

353

(Scenario IV). Since 2010, the relative importance of 8:2 degFTOH has been increasing in the wake of

354

the phase-out of long-chain products in most world regions. Such a transition from resFTOH-dominant

355

to degFTOH-dominant releases is also obvious for Scenario I of 6:2 FTOH (Figure 3g), in which the

356

annual releases of 6:2 degFTOH would exceed that of 6:2 resFTOH by approximately 2025. Our finding

357

of the dominance of resFTOHs is consistent with previous studies.11, 13 For instance, van Zelm et al.13

358

calculated that 8:2 resFTOH constituted up to 75% of the total 8:2 FTOH in European air, freshwater

359

and seawater prior to 2025, although their estimated annual releases of 8:2 degFTOH are at least one

360

order of magnitude higher than ours because the authors assumed that, before entering the use phase,

361

one third of historically produced FTPs had been liberated from industrial processes and subjected to

362

degradation.

363

The dominance of resFTOHs before around 2010 also provides justification for the good agreement

364

between measured and modelled FTOH concentrations in a series of earlier modelling studies37, 39, 42

365

which were based on emission estimates of resFTOHs alone. Furthermore, we modelled the atmospheric

366

concentrations of FTOHs using the BETR-Global model and our CiP-CAFE-derived multimedia

367

emission estimates of resFTOH and degFTOH under Scenario I. The modelled concentrations of 8:2 and

368

6:2 FTOHs were then plotted against measured concentrations (Figure 4), which had been reported from

369

large-scale sampling cruises or on-land campaigns1,

370

representative BETR-Global cells (Figure SF-1). Cells covering the territory of mainland China were

371

excluded from the comparison, because the ongoing production and new uses of long-chain products in

372

China could still be a cause for resFTOH releases thus resulting in an underestimation in 8:2FTOH

373

concentrations. Figure 4a and 4b demonstrate good agreement between measured and modelled 8:2

374

FTOH concentrations, whether the releases of 8:2 degFTOH from scenario I are considered or not

375

(Figure 3c). However, including releases of 8:2 degFTOH (Figure 4b) improves model agreement with

376

the more recent measurements, most notably the latest available measurements (at the bottom left)

377

which were sampled between Oct. 2010 and Jan. 2011.44 Such an improvement lends supports to our

43-54

so as to encompass a wide span of

17



Page 18 of 31

378

hypothesis of an increasing contribution of degFTOHs. Compared with Scenario I, the improvements in

379

the other scenarios were less remarkable (data not shown) because the estimated releases of 8:2

380

degFTOH are much smaller than those of 8:2 resFTOH (Figure 3c). It should be noted that, while

381

agreement with measurements is best using Scenario I (Figure 4b), we are reluctant to pronounce one

382

scenario more realistic than another, because (i) the contribution of degFTOHs is rather low at present

383

(Figure 3c) thus being easily drowned out by the considerable uncertainty or variability associated with

384

the measurements (error bars in Figure 4); and (ii) the number of recent (especially since 2011)

385

measured data is limited. In addition, while we believe that the bulk of FTPs degrade during the waste

386

disposal phases, there can be continuous, but currently unquantifiable, losses or degradation of in-use

387

FTPs due to washing, abrasion or weathering.2 Figure S3 indicates that assuming the degradation of an

388

annual loss of 2%, 5% and 40% of in-use stocks of FTPs elevates the annual releases of degFTOHs and

389

deg-degPFCAs (under Scenario I) by a factor of approximately 3, 5 and 15, respectively. This would

390

lead to an overestimation of the observed atmospheric occurrence of total FTOHs, given the good

391

agreements between our modelling results and measurements in Figure 4. Nevertheless, investigations

392

on FTP loss during the use phase are required to allow quantification of this potential source. For 6:2

393

FTOH (Figure 4c and d), while including 6:2 degFTOH releases improves model agreement with the

394

more recent measurements as well, the improvement is too minor to be readily perceived from the figure,

395

because the estimated releases of 6:2 degFTOH are nearly 2 orders of magnitude lower than those of 6:2

396

resFTOH.

397

From a regulatory perspective, our calculation implies that the increasing contribution of FTP

398

degradation has the potential to partially offset the reduction in FTOH residuals in products achieved by

399

the 2010/15 PFOA Stewardship Program and other regulatory efforts. This could partially explain the

400

recent rebound of declining atmospheric concentrations of 8:2 FTOH; for instance, a multiannual trend

401

analysis indicated that 8:2FTOH concentrations in samples from the Global Atmospheric Passive

402

Sampling (GAPS) Network initially declined from 2006 – 2008 (33 – 46 samples each year) but then

403

increased again from 2009 – 2011 (19 – 34 samples each year).55

18


Page 19 of 31


404

Figure 4 Comparison between literature-reported measured and BETR-Global modelled atmospheric

405

concentrations of 8:2 FTOH (a and b) and 6:2 FTOH (c and d) at different sites (see Figure SF-1 for

406

their BETR-Global cells). The BETR-Global simulations were based on the annual releases of

407

resFTOHs alone (a and c), and combined resFTOHs and degFTOHs under the Scenario I (b and d).

408

Diagonal lines represent perfect agreement (solid), and agreement within a factor of 100.5 (dashed) and

409

10 (dotted). Error bars indicate range of the concentrations (i.e., the difference between maximum and

410

minimum).

411 412

FTP degradation in waste stocks as a long-term source of PFCAs

413

We compared the annual releases of deg-degPFCAs estimated above (Figures 3d and 3h) with other

414

PFCAs sources, i.e. impPFCAs and deg-resPFCAs (both liberated from waste stocks and formed in the

415

environment) (Figure S4), which are also related to the uses of fluorotelomer-based substances. Figure

416

S4 shows that, for both PFOA and PFHxA, the annual releases of deg-resPFCAs are nearly 3 orders of

417

magnitude higher than those of impPFCAs. The releases of impPFOA and deg-resPFOA are anticipated

418

to cease within a decade when the service life of non-polymeric C8 fluorotelomer-based substances (e.g.,

419

AFFFs and surfactants) comes to the end. This is in contrast to the release of deg-degPFOAs (Figure 3d),

420

which will last for decades and even centuries. Currently, the deg-degPFOA is estimated to account for 3%

421

(Scenario II and IV) – 30% (Scenario I) of deg-resPFOA. Such a dominance of deg-resPFOA in the total

422

FTP-related PFOA releases has also been reported by Russell et al.,5 who indicated that deg-degPFOA

19



Page 20 of 31

423

had contributed 18% to the PFOA historically released from FTP-related sources by 2007 while

424

deg-resPFOA had contributed 77%, based on the assumed degradation half-life of 1000 – 2000 yrs.

425

A number of other PFCA sources18, 19 exist apart from the three (deg-degPFCAs, deg-resPFCAs and

426

impPFCAs) considered in this work (Figure 1). The most recent reliable estimate of the global total

427

release of PFCAs (C4 – C14) from these sources is approximately 5600 – 13000 t between 1951 and

428

2015 (under the plausible scenario),18 which is nearly 1 order of magnitude higher than the estimated

429

cumulative release of deg-degPFCAs (556 – 591 t, C4 – C12) in our highest-release Scenario I for the

430

same period. Therefore, omitting the contribution from the degradation of FTPs when estimating

431

historical PFCA emissions18, 19, 37 should not lead to a significant underestimation.

432

Nevertheless, the degradation of FTPs in waste stocks can be a significant source of PFCAs in the

433

future, in particular when deliberate uses of (long-chain) PFCAs will terminate. Our estimates suggest

434

that 1323 – 1535 t of deg-degPFCAs (C4 – C12) will be released during 2016 – 2040 in Scenario I (data

435

not shown). This level is in the same order as the projected cumulative release of 10 – 3830 t from

436

intentional uses of PFCAs (C4 – C14) for 2015 – 2030 (worst case assuming no restrictions on PFCAs

437

will be taken in developing countries).18 Meanwhile, our long-term calculation under Scenario I (Figure

438

S2) indicates that, between 2015 and 2100, another 7 times as much will be released as the cumulative

439

emissions of deg-degPFOA up to 2015. Moreover, by 2100, 1170 – 1380 t of deg-degPFOA is estimated

440

to be present in waste stocks (data not shown), which is available for leaching into the environment in

441

the following centuries. Our calculations highlight the need for environmentally sound management of

442

the waste stocks of FTPs into the foreseeable future. On the one hand, instead of being deposited in

443

landfills and dumps, destruction and irreversible transformation techniques (e.g., incineration) should be

444

the preferable disposal options for obsolete FTP-containing finished products; on the other hand, landfill

445

gases and leachates from historical and current landfills and dumps, which are respectively the two

446

major routes liberating degFTOHs and deg-degPFCAs into the environment, should be appropriately

447

treated or remediated.

20


Page 21 of 31


448

Supporting Information

449

Texts describing terms and models used in this study, and generation of FTOHs from degradation of

450

polyfluoroalkyl phosphates; tables detailing homologue composition and contents, international trade

451

and lifespan distribution of consumer products, emission and waste factors, and physicochemical

452

properties of modelled chemicals; and figures depicting global annual production of technical

453

fluorotelomer-based substances, additional release estimates, and illustration of the influence from

454

considering assumed FTP loss during use phase. This material is available free of charge via the Internet

455

at http://pubs.acs.org.

456

Acknowledgment

457

The authors thank Roland Weber for insightful discussion on PFAS leaching from waste stocks. This

458

study was financially supported by the National Natural Science Foundation of China (No.21577002). L.

459

L. acknowledges scholarships from the China Scholarship Council and Shanghai Tongji Gao Tingyao

460

Environmental Science and Technology Development Foundation.

461

Literature cited

462

1.

463 464

USEPA Telomer Research Program Update. Presentation to USEPA-OPPT, November 25, 2002; U.S. Public Docket AR226-1141; 2002.

2.

Holmquist, H.; Schellenberger, S.; van der Veen, I.; Peters, G.; Leonards, P.; Cousins, I., Properties,

465

performance and associated hazards of state-of-the-art durable water repellent (DWR) chemistry for

466

textile finishing. Environ. Int. 2016, 91, 251-264.

467

3.

468 469

OECD OECD/UNEP Global PFC Group, Synthesis Paper on Per- and Polyfluorinated Chemicals (PFCs); Environment, Health and Safety, Environment Directorate, OECD: 2013.

4.

Washington, J. W.; Jenkins, T. M.; Rankin, K.; Naile, J. E., Decades-scale degradation of

470

commercial, side-chain, fluorotelomer-based polymers in soils and water. Environ. Sci. Technol.

471

2015, 49, (2), 915-923.

472 473

5.

Russell, M. H.; Berti, W. R.; Szostek, B.; Buck, R. C., Investigation of the biodegradation potential of a fluoroacrylate polymer product in aerobic soils. Environ. Sci. Technol. 2008, 42, (3), 800-807.

21



474

6.

Page 22 of 31

Washington, J. W.; Ellington, J. J.; Jenkins, T. M.; Evans, J. J.; Yoo, H.; Hafner, S. C., Degradability

475

of an acrylate-linked, fluorotelomer polymer in soil. Environ. Sci. Technol. 2009, 43, (17),

476

6617-6623.

477

7.

Ellis, D. A.; Martin, J. W.; De Silva, A. O.; Mabury, S. A.; Hurley, M. D.; Sulbaek Andersen, M. P.;

478

Wallington, T. J., Degradation of Fluorotelomer Alcohols: A Likely Atmospheric Source of

479

Perfluorinated Carboxylic Acids. Environ. Sci. Technol. 2004, 38, (12), 3316-3321.

480

8.

Phillips, M. M.; Dinglasan-Panlilio, M. J. A.; Mabury, S. A.; Solomon, K. R.; Sibley, P. K.,

481

Fluorotelomer acids are more toxic than perfluorinated acids. Environ. Sci. Technol. 2007, 41, (20),

482

7159-7163.

483

9.

Giesy, J. P.; Naile, J. E.; Khim, J. S.; Jones, P. D.; Newsted, J. L., Aquatic toxicology of

484

perfluorinated chemicals. In Reviews of Environmental Contamination and Toxicology, Whitacre, D.

485

M., Ed. Springer: New York, 2010; Vol. 202, pp 1-52.

486 487

10. Ahrens, L.; Bundschuh, M., Fate and effects of poly- and perfluoroalkyl substances in the aquatic environment: A review. Environ. Toxicol. Chem. 2014, 33, (9), 1921-1929.

488

11. Wang, Z.; Cousins, I. T.; Scheringer, M.; Buck, R. C.; Hungerbühler, K., Global emission

489

inventories for C4–C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, part

490

II: The remaining pieces of the puzzle. Environ. Int. 2014, 69, 166-176.

491

12. Russell, M. H.; Berti, W. R.; Szostek, B.; Wang, N.; Buck, R. C., Evaluation of PFO formation from

492

the biodegradation of a fluorotelomer-based urethane polymer product in aerobic soils. Polym.

493

Degrad. Stab. 2010, 95, (1), 79-85.

494

13. van Zelm, R.; Huijbregts, M. A.; Russell, M. H.; Jager, T.; van de Meent, D., Modeling the

495

environmental fate of perfluorooctanoate and its precursors from global fluorotelomer acrylate

496

polymer use. Environ. Toxicol. Chem. 2008, 27, (11), 2216-2223.

497

14. Washington, J. W.; Jenkins, T. M., Abiotic hydrolysis of fluorotelomer-based polymers as a source

498

of perfluorocarboxylates at the global scale. Environ. Sci. Technol. 2015, 49, (24), 14129-14135.

22


Page 23 of 31


499

15. Lang, J. R.; Allred, B. M.; Peaslee, G. F.; Field, J. A.; Barlaz, M. A., Release of per- and

500

polyfluoroalkyl substances (PFASs) from carpet and clothing in model anaerobic landfill reactors.

501

Environ. Sci. Technol. 2016, 50, (10), 5024-5032.

502

16. Yan, H.; Cousins, I. T.; Zhang, C.; Zhou, Q., Perfluoroalkyl acids in municipal landfill leachates

503

from China: Occurrence, fate during leachate treatment and potential impact on groundwater. Sci.

504

Total Environ. 2015, 524–525, 23-31.

505

17. Ahrens, L.; Shoeib, M.; Harner, T.; Lee, S. C.; Guo, R.; Reiner, E. J., Wastewater treatment plant

506

and landfills as sources of polyfluoroalkyl compounds to the atmosphere. Environ. Sci. Technol.

507

2011, 45, (19), 8098-8105.

508

18. Wang, Z.; Cousins, I. T.; Scheringer, M.; Buck, R. C.; Hungerbühler, K., Global emission

509

inventories for C4–C14 perfluoroalkyl carboxylic acid (PFCA) homologues from 1951 to 2030, Part

510

I: production and emissions from quantifiable sources. Environ. Int. 2014, 70, 62-75.

511 512 513 514 515 516 517 518

19. Prevedouros, K.; Cousins, I. T.; Buck, R. C.; Korzeniowski, S. H., Sources, fate and transport of perfluorocarboxylates. Environ. Sci. Technol. 2006, 40, (1), 32-44. 20. Royer, L. A.; Lee, L. S.; Russell, M. H.; Nies, L. F.; Turco, R. F., Microbial transformation of 8: 2 fluorotelomer acrylate and methacrylate in aerobic soils. Chemosphere 2015, 129, 54-61. 21. Lee, H.; D’eon, J.; Mabury, S. A., Biodegradation of polyfluoroalkyl phosphates as a source of perfluorinated acids to the environment. Environ. Sci. Technol. 2010, 44, (9), 3305-3310. 22. Liu, C.; Liu, J., Aerobic biotransformation of polyfluoroalkyl phosphate esters (PAPs) in soil. Environ. Pollut. 2016, 212, 230-237.

519

23. Backe, W. J.; Day, T. C.; Field, J. A., Zwitterionic, cationic, and anionic fluorinated chemicals in

520

aqueous film forming foam formulations and groundwater from US military bases by nonaqueous

521

large-volume injection HPLC-MS/MS. Environ. Sci. Technol. 2013, 47, (10), 5226-5234.

522 523

24. Butt, C. M.; Muir, D. C. G.; Mabury, S. A., Biotransformation pathways of fluorotelomer compounds. Environ. Toxicol. Chem. 2014, 33, (2), 243-267.

23



Page 24 of 31

524

25. Ruan, T.; Wang, Y.; Wang, T.; Zhang, Q.; Ding, L.; Liu, J.; Wang, C.; Qu, G.; Jiang, G., Presence

525

and partitioning behavior of polyfluorinated iodine alkanes in environmental matrices around a

526

fluorochemical manufacturing plant: Another possible source for perfluorinated carboxylic acids?

527

Environ. Sci. Technol. 2010, 44, (15), 5755-5761.

528 529 530 531 532 533 534 535 536 537

26. Li, L.; Wania, F., Tracking chemicals in products around the world: introduction of a dynamic substance flow analysis model and application to PCBs. Environ. Int. 2016, 94, 674-686. 27. Li, L.; Zhai, Z.; Liu, J.; Hu, J., Estimating industrial and domestic environmental releases of perfluorooctanoic acid and its salt in China. Chemosphere 2015, 129, 100-109. 28. Vestergren, R.; Herzke, D.; Wang, T.; Cousins, I. T., Are imported consumer products an important diffuse source of PFASs to the Norwegian environment? Environ. Pollut. 2015, 198, 223-230. 29. ECHA ANNEX XV Restriction Report Proposal for A Restriction. Perfluorooctanoic Acid (PFOA), PFOA Salts and PFOA-Related Substances; European Chemicals Agency: 2014. 30. USEPA Long-Chain Perfluorinated Chemicals (PFCs) Action Plan; U.S. Environmental Protection Agency: Washington D.C., 2009.

538

31. Castelvetro, V.; Aglietto, M.; Ciardelli, F.; Chiantore, O.; Lazzari, M.; Toniolo, L., Structure control,

539

coating properties, and durability of fluorinated acrylic-based polymers. J. Coating Technol. 2002,

540

74, (928), 57-66.

541

32. DuPont, E. I. Oil- and Water-Repellent Copolymers (EU Patent No. 87300551.6). 1987.

542

33. Watkins, M. H.; Covelli, C. A.; Seals, L. R. Fabric Treated with Durable Stain Repel and Stain

543

Release Finish and Method of Industrial Laundering to Maintain Durability of Finish (US Patent No.

544

2006/0228964 A1). 2006.

545 546

34. MacLeod, M.; Scheringer, M.; Hungerbuhler, K., Estimating enthalpy of vaporization from vapor pressure using Trouton's rule. Environ. Sci. Technol. 2007, 41, (8), 2827-2832.

547

35. MacLeod, M.; von Waldow, H.; Tay, P.; Armitage, J. M.; Wöhrnschimmel, H.; Riley, W. J.; McKone,

548

T. E.; Hungerbühler, K., BETR Global–A geographically-explicit global-scale multimedia

549

contaminant fate model. Environ. Pollut. 2011, 159, (5), 1442-1445.

24


Page 25 of 31


550

36. MacLeod, M.; Riley, W. J.; McKone, T. E., Assessing the influence of climate variability on

551

atmospheric concentrations of polychlorinated biphenyls using a global-scale mass balance model

552

(BETR-Global). Environ. Sci. Technol. 2005, 39, (17), 6749-6756.

553 554

37. Wania, F., A global mass balance analysis of the source of perfluorocarboxylic acids in the Arctic Ocean. Environ. Sci. Technol. 2007, 41, (13), 4529-4535.

555

38. Wallington, T.; Hurley, M.; Xia, J.; Wuebbles, D.; Sillman, S.; Ito, A.; Penner, J.; Ellis, D.; Martin,

556

J.; Mabury, S., Formation of C7F15COOH (PFOA) and other perfluorocarboxylic acids during the

557

atmospheric oxidation of 8: 2 fluorotelomer alcohol. Environ. Sci. Technol. 2006, 40, (3), 924-930.

558

39. Schenker, U.; Scheringer, M.; Macleod, M.; Martin, J. W.; Cousins, I. T.; Hungerbühler, K.,

559

Contribution of volatile precursor substances to the flux of perfluorooctanoate to the Arctic. Environ.

560

Sci. Technol. 2008, 42, (10), 3710-3716.

561 562

40. Kjeldsen, P.; Christensen, T. H., A simple model for the distribution and fate of organic chemicals in a landfill: MOCLA. Waste management & research 2001, 19, (3), 201-216.

563

41. Kim, M.; Li, L. Y.; Grace, J. R.; Yue, C., Selecting reliable physicochemical properties of

564

perfluoroalkyl and polyfluoroalkyl substances (PFASs) based on molecular descriptors. Environ.

565

Pollut. 2015, 196, 462-472.

566

42. Yarwood, G.; Kemball-Cook, S.; Keinath, M.; Waterland, R. L.; Korzeniowski, S. H.; Buck, R. C.;

567

Russell, M. H.; Washburn, S. T., High-resolution atmospheric modeling of fluorotelomer alcohols

568

and perfluorocarboxylic acids in the North American troposphere. Environ. Sci. Technol. 2007, 41,

569

(16), 5756-5762.

570

43. Li, J.; Del Vento, S.; Schuster, J.; Zhang, G.; Chakraborty, P.; Kobara, Y.; Jones, K. C.,

571

Perfluorinated compounds in the Asian atmosphere. Environ. Sci. Technol. 2011, 45, (17),

572

7241-7248.

573

44. Wang, Z.; Xie, Z.; Mi, W.; Möller, A.; Wolschke, H.; Ebinghaus, R., Neutral poly/per-fluoroalkyl

574

substances in air from the Atlantic to the Southern Ocean and in Antarctic snow. Environ. Sci.

575

Technol. 2015, 49, (13), 7770-7775.

25



Page 26 of 31

576

45. Xie, Z.; Zhao, Z.; Möller, A.; Wolschke, H.; Ahrens, L.; Sturm, R.; Ebinghaus, R., Neutral poly-and

577

perfluoroalkyl substances in air and seawater of the North Sea. Environ. Sci. Pollut. Res. 2013, 20,

578

(11), 7988-8000.

579

46. Shoeib, M.; Vlahos, P.; Harner, T.; Peters, A.; Graustein, M.; Narayan, J., Survey of polyfluorinated

580

chemicals (PFCs) in the atmosphere over the northeast Atlantic Ocean. Atmos. Environ. 2010, 44,

581

(24), 2887-2893.

582 583 584 585

47. Shoeib, M.; Harner, T.; Vlahos, P., Perfluorinated chemicals in the Arctic atmosphere. Environ. Sci. Technol. 2006, 40, (24), 7577-7583. 48. Oono, S.; Harada, K. H.; Mahmoud, M. A.; Inoue, K.; Koizumi, A., Current levels of airborne polyfluorinated telomers in Japan. Chemosphere 2008, 73, (6), 932-937.

586

49. Barber, J. L.; Berger, U.; Chaemfa, C.; Huber, S.; Jahnke, A.; Temme, C.; Jones, K. C., Analysis of

587

per-and polyfluorinated alkyl substances in air samples from Northwest Europe. J. Environ. Monitor.

588

2007, 9, (6), 530-541.

589

50. Dreyer, A.; Weinberg, I.; Temme, C.; Ebinghaus, R., Polyfluorinated compounds in the atmosphere

590

of the Atlantic and Southern Oceans: evidence for a global distribution. Environ. Sci. Technol. 2009,

591

43, (17), 6507-6514.

592

51. Cai, M.; Xie, Z.; Möller, A.; Yin, Z.; Huang, P.; Cai, M.; Yang, H.; Sturm, R.; He, J.; Ebinghaus, R.,

593

Polyfluorinated compounds in the atmosphere along a cruise pathway from the Japan Sea to the

594

Arctic Ocean. Chemosphere 2012, 87, (9), 989-997.

595 596 597 598

52. Ahrens, L.; Shoeib, M.; Del Vento, S.; Codling, G.; Halsall, C., Polyfluoroalkyl compounds in the Canadian Arctic atmosphere. Environ. Chem. 2011, 8, (4), 399-406. 53. Xie, Z.; Wang, Z.; Mi, W.; Möller, A.; Wolschke, H.; Ebinghaus, R., Neutral poly-/perfluoroalkyl substances in air and snow from the Arctic. Sci. Rep. 2015, 5, 8912, doi:10.1038/srep08912.

599

54. Vento, S. D.; Halsall, C.; Gioia, R.; Jones, K.; Dachs, J., Volatile per- and polyfluoroalkyl

600

compounds in the remote atmosphere of the western Antarctic Peninsula: an indirect source of

601

perfluoroalkyl acids to Antarctic waters? Atmos. Pollut. Res. 2012, 3, (4), 450-455.

26


Page 27 of 31


602

55. Gawor, A.; Shunthirasingham, C.; Hayward, S.; Lei, Y.; Gouin, T.; Mmereki, B.; Masamba, W.;

603

Ruepert, C.; Castillo, L.; Shoeib, M.; Lee, S. C.; Harner, T.; Wania, F., Neutral polyfluoroalkyl

604

substances in the global atmosphere. Env. Sci. Process. Impact 2014, 16, (3), 404-413.

27



Transformation of FTPs, FTOHs and PFCAs in the environment and waste stocks [R' = H or methyl group; R = H or (meth)acrylic group]. Arrows in solid line denote the substance flows quantified in this work: estimating stocks of FTPs, and annual releases of degFTOHs and deg-degPFCAs, are the main objectives (denoted as blue and red shadings); annual releases of resFTOHs, deg-resPFCA and impPFCAs are also calculated for comparison. Arrows in dashed line represent substance flows not quantified. The box “other PFCA sources” includes all PFCAs sources in Wang et al.18 other than the three considered here. Figure 1


Page 28 of 31

Page 29 of 31


Schematic of the modelling strategy in this study. Green boxes indicate model outputs while blue boxes indicate data collected from the literature or calculated from model outputs. Red diamonds indicate a calculation using models. Figure 2



Estimated ranges of global in-use stocks (a and e) and waste stocks (b and f) of FTPs, annual releases of degFTOHs (c and g) and deg-degPFCAs (d and h) for C8- (from a to d) and C6-compounds (from e to h) from 1960 – 2040 under the four simulation scenarios: (I) LS=10 yrs and HL=75 yrs, (II) LS=10 yrs and HL=1500 yrs, (III) LS=50 yrs and HL=75 yrs, and (IV) LS=50 yrs and HL=1500 yrs. The global annual releases of resFTOHs are presented in grey shading in panels c and g for comparison. Figure 3 85x41mm (300 x 300 DPI)


Page 30 of 31

Page 31 of 31


Comparison between literature-reported measured and BETR-Global modelled atmospheric concentrations of 8:2 FTOH (a and b) and 6:2 FTOH (c and d) at different sites (see Figure SF-1 for their BETR-Global cells). The BETR-Global simulations were based on the annual releases of resFTOHs alone (a and c), and combined resFTOHs and degFTOHs under the Scenario I (b and d). Diagonal lines represent perfect agreement (solid), and agreement within a factor of 10^0.5 (dashed) and 10 (dotted). Error bars indicate range of the concentrations (i.e., the difference between maximum and minimum). Figure 4 177x48mm (300 x 300 DPI)


Degradation of Fluorotelomer-Based Polymers ... - ACS Publications

Recommend Documents