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Environmental Processes
Microplastics as both a Sink and a Source of Bisphenol A in the Marine Environment Xuemin Liu, Huahong Shi, Bing Xie, Dionysios D. Dionysiou, and yaping Zhao Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.9b02834 • Publication Date (Web): 08 Aug 2019 Downloaded from pubs.acs.org on August 10, 2019
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Microplastics as both a Sink and a Source of Bisphenol A in the Marine Environment
2
Xuemin Liu,† Huahong Shi,‡ Bing Xie,† Dionysios D. Dionysiou,§,* and Yaping Zhao†,*
3
†School
4
Process and Eco-Restoration, East China Normal University, Shanghai 200241, China
5
‡State
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200241, China
7
§Environmental
8
Engineering (DChEE), 705 Engineering Research Center, University of Cincinnati, Cincinnati, Ohio, USA
9
ABSTRACT:
of Ecological and Environmental Sciences, Shanghai Key Laboratory for Urban Ecological
Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai,
Engineering and Science Program, Department of Chemical and Environmental
10
Microplastics were demonstrated to be an environmental sink for hydrophobic organic
11
pollutants, while they can also serve as a potential source of such pollutants. In this study, the
12
sorption and release of bisphenol A in marine water was investigated through laboratory
13
experiments. Sorption and desorption isotherms were developed and the results reveal that
14
sorption and desorption depend on the crystallinity, elasticity and hydrophobicity of the
15
polymer concerned. The adsorption and partition of bisphenol A can be quantified using a
16
dual-mode model of the sorption mechanisms. Polyamide and polyurethane were found to
17
exhibit the highest sorption capacity for bisphenol A, and it was almost irreversible, probably
18
due to hydrogen bonding. Polyethylenes and polypropylene exhibited high and reversible
19
sorption without noticeable desorption hysteresis. Glassy polystyrene, polyvinylchloride,
20
polymethyl methacrylate and polyethylene terephthalate exhibited low sorption capacity and
21
only partial reversibility. Low-density polyethylene and polycarbonate microplastic particles
22
were for the first time proved to be a persistent source releasing bisphenol A into aquatic
23
environments. Salinity, pH, co-existing estrogens and water chemistry influence the
24
sorption/desorption behaviors to different degree. Plastic particles can serve as transportation 1
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vectors for bisphenol A, which may constitute an ecological risk.
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Key words: Microplastics, Bisphenol A, sorption, sources, sinks, environmental risks,
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marine pollution
28
INTRODUCTION
29
Plastic debris is widely regarded as a global environmental threat exacerbated by the
30
increasing mass production of waste plastic over the last few decades and its poor
31
management.1, 2 Microplastics (MPs, with diameter of > PS > PEs (LLD, MD and HD) ≈ PP > PMMA ≈ PVC and PET. The
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enrichment factor of BPA on MPs could reach up to 105 and the calculated distribution
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coefficient Kd varied from 0.41 L kg-1 (with PVC) to 76,287 L kg-1 (for PA) (at 0.005 Sw,
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Table S6). The huge differences in BPA’s solid-liquid distribution can be ascribed to the
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different structural properties of the diverse MPs tested.
180
Usually, the sorption of HOCs by organic matter in soil is thermodynamically driven,
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involving specific hydrophobic interactions, hydrogen bonding and π-π interaction.40 Plastics
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can be simplified by analogy with organic matter in soil to study specific MP-HOC
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interactions.15, 41 The static water contact angle is widely used to describe the hydrophobicity
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of MPs (Figure S2, Table S2). A larger contact angle indicates greater hydrophobicity.42, 43 A
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significant positive correlation between sorption capacity for BPA (Qe) and the water contact
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angle of MPs was observed in this study (Table S3, p≤ 0.05 at Ce= 0.005 Sw). The MPs’ BPA
187
sorption capacity was highly dependent on their hydrophobicity. Similarly, about 66% of the
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BPA absorbed by non-woven PP can be attributed to hydrophobic interaction, indicating the
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crucial role of hydrophobic interaction played in BPA sorption.44,
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tested, PA and PU exhibited the largest sorption affinity towards BPA. That should be
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ascribed to the formation of hydrogen bonds between H-bond-donating BPA and the H-bond
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accepting amide groups in PA or PU.47, 48 T-tests confirmed that the BPA sorption capacity
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(Qe) on PA or PU through H-bond interaction was significantly greater than that of the other
194
MPs tested (Table S4, p≤ 0.001 at Ce= 0.005 Sw). PS particles exhibited a medium level of
195
BPA sorption capacity comparing with that of MDPE, PP, PVC, PMMA or PET. That can
196
mainly be ascribed to the contribution of π−π interactions between BPA’s benzene rings and
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those of PS.49, 50 In addition, the benzene ring in PS’s polymeric backbone restricts segmental
45, 46
Among the MPs
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mobility within the chains and increases the distance between adjacent chains, allowing BPA
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to more easily diffuse into a PS matrix.18
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The polymers’ structure consists of highly ordered crystalline domains and less structured
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amorphous domains. Crystallinity can influence the sorption of HOCs because the loosely
202
packed polymer chains in the amorphous domains increase the accessibility of HOCs into the
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inner-space of polymer compared to the crystalline domains.15,
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calorimeter (DSC) data can characterize the abundance of amorphous and crystalline domains
205
in a polymer (Figure S3, Table S2). The data show that crystallinity is significantly correlated
206
with hydrophobicity (r= 0.599, *p≤ 0.05, Table S3), so greater BPA sorption capacity would
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be expected from MPs with higher crystallinity. However, no significant correlation between
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the BPA sorption capacities of the MPs and their crystallinity was observed at Ce= 0.005 Sw
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(Table S3), suggesting that crystallinity has at best a minor effect on MPs’ sorption of BPA.
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Despite the effect of crystallinity, MPs’ hydrophobicity was also affected by other factors,
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such as surface functional groups and surface roughness.51 Therefore, the effect of
212
hydrophobicity derived from crystallinity on MPs’ sorption of BPA might decrease, resulting
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in a weak correlation between Qe and crystallinity.
25
Differential scanning
214
PEs and PP particles with a lower fraction of amorphous domains were found to have
215
greater BPA sorption capacity. This result is consistent with previous reports that the rubbery
216
plastic PE has higher sorption capacity towards phenanthrene and perfluorooctanesulfonates
217
(PFOS) than that of glassy PS and PVC.10,
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domains rather than its glassy domains predominantly determine its BPA sorption capacity.24
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The relatively expanded, flexible structure of rubbery plastics like PEs and PP should thus
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allow greater mobility, diffusivity, and accessibility for BPA than the more condensed and
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less flexible structure of glassy MPs. T-tests confirmed this explanation (at Ce= 0.005 Sw, *p≤
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0.05, Table S5). Similar studies have indicated that rubbery PEs and PP possess a higher free
25
It can be inferred that a polymer’s rubbery
9
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volume of internal cavities in the rubbery domains compared with that of glassy PET and
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PVC, contributing to greater preferential accumulation of PAHs and PCBs in PEs and PP.8, 11,
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52
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The importance or the effect of specific surface area and particle size on the BPA sorption
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by MPs should also be stressed. Smaller particles with greater specific surface area (Sarea)
228
have been shown to have greater sorption capacity of BPA on PP because the larger surface
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area increases the availability of sorption sites.53,
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preferential sorption of tyosin and pyrene on PE compared to PS and PVC is mainly due to
231
PE’s larger specific surface area.55, 56 In this study, however, no significant correlation was
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observed between Sarea or the particle size of the various MPs and their BPA sorption
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capacity (at Ce= 0.005 Sw, Table S3), indicating that the influence of Sarea or particle size was
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negligible compared with that of crystallinity, hydrophobicity and a polymer’s rubbery
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nature. It is obvious, though, that for the same type of polymer (take MDPE as an example),
236
smaller particles and larger specific surface area should indeed contribute to the greater
237
sorption of BPA. This has been confirmed in a previous study.36
238
Sorption Mechanisms.
54
Some researchers have suggested that
239
Sorption of HOCs onto polymers has often been described in terms of a dual-mode
240
polymer sorption model involving both adsorption and partition mechanisms. The adsorption
241
of HOCs in amorphous domains is identified as solid–phase dissolution described using a
242
partition model. In the polymer’s crystalline domains, adsorption and pore–filling better
243
describe the interaction.57 The total sorption is the sum of the two processes, partition and
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adsorption. So
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QT = QA + QP
246
where QT represents the total sorption capacity, QA is the adsorption capacity and QP is the
(1)
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partition capacity.58, 59 The sorption isotherms of BPA on various MPs are well fitted using Freundlich isotherm
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model, thus the total sorption can be described as
250
QT = a Cen
251
where a and n are constants. In this dual-mode model of the interaction, the contribution of
252
adsorption is nonlinear and can reach saturation rapidly depending on the surface area of the
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MPs, while the contribution of partition can increase linearly with time depending on the
254
BPA concentration and the type of MPs. The isotherms should be linear at high
255
concentrations, and the total sorption amount QT′ can then be described as
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QT′= MCe + N
257
where M and N are constants. MCe is the sorption contribution through partition (QP) and N
258
represents the maximum adsorption capacity (QAmax). Therefore, the adsorption capacity (QA)
259
can be calculated as:
260
QA = aCen- MCe
(2)
(3)
(4)
261
Equations 1–4 thus allow quantifying the isotherm parameters QT, QP, and QA (Table S6).
262
The contributions of QP and QA can be quantified by fitting a dual-mode sorption model,
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which depends heavily on the BPA concentrations and the structural properties of MPs
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involved (Figure S4). Within the range of BPA concentrations studied here, the sorption by
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rubbery MDPE, HDPE and PP and by glassy PET was dominated by adsorption at low BPA
266
concentrations (< 200 μg L-1) but then by partition at higher BPA concentrations. For the
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glassy PS, PVC and PMMA polymers and rubbery LLDPE, adsorption was more important
268
than partition at all of the concentrations studied. Given a high enough BPA concentration,
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the sorption of BPA on MPs will eventually be partition-dominated due to hydrophobic
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interaction.60 For glassy PA and PU, the hydrophobic, partition-dominated sorption process is 11
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remarkably strengthened by hydrogen-bond interactions. The hydrogen bond energy values
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(2–40 kJ mol-1) involved are much higher than those of hydrophobic bonds (5 kJ mol-1).61
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The Effects of Water Chemistry on BPA Sorption.
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Polymer particles in aqueous environments can be carried out to sea through river
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networks or be transported back into estuarine habitats from the sea via tidal flow.62 Complex
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interactions between such particles and any BPA present may vary in different water
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environments. The particles’ sorption capacity for BPA with tend to decrease as the pH
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increases from 3.0 to 11.0 (Figure 1b), probably due to BPA’s greater solubility and
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hydrophilicity at higher pH values. In addition, BPA will exist partially as an anion (pKa=
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9.6–10.2) and the surfaces of MPs tend to be negatively charged at high pH values (For
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example, the pHPZC of PE, PP, and PS are at pH 4.30, 4.26 and 3.96, respectively).52 That
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might increase the electrostatic repulsion between BPA and the MPs, decreasing the BPA
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sorption capacity. In natural surface water (6.5< pH< 8.5), MPs will exhibit relatively stable
284
sorption of BPA and can be regarded as potential BPA sinks. Sorption of estrone,
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17β-estradiol and 17α-ethinylestradiol on PA 6 has also been shown to decline drastically
286
with increasing pH (from 2 to 12), especially at pH> 10.5 (the pKa of many
287
endocrine-disrupting compounds).63 However, Wang et al. revealed that the sorption of PFOS
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on PE and PS increased with a decrease in pH (from 7.0 to 3.0), but that pH had no effect on
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the sorption of PFOS on PE or PS.10 Interestingly, Xu et al. have reported that the sorption of
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tetracycline on PE, PP and PS initially increases then decreases as the pH increases from 2.0
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to 12.0 due to the fact that tetracycline is a zwitterionic compound.64
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Usually, high salinity would increase the availability of BPA for sorption onto MPs owing
293
to salting-out. In this study, when salinity was increased from 12 ‰ to 35 ‰, it indeed had a
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slightly negative effect on the sorption capacity of the MPs, except for those of PA and PU
295
(Figure 1c). Higher salinity has also been shown to inhibit the sorption of tetracycline and 12
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musk on MPs.64, 65 However, increased salinity showed no obvious effect on the sorption of
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phenanthrene by PE or PVC. It did, though, decrease the sorption of DDT.13 Increased
298
salinity enhanced the sorption of triclosan but showed only a minor influence on
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4-methylbenzylidene camphor, carbamazepine and 17α-ethinylestradiol sorption on PE.43
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The effects of salinity on sorption may diverge depending on the nature of the adsorbate. In
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this work, the influence of salinity on BPA sorption on MPs can be neglected.
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The BPA sorption capacity was in the sequence of ultrapure water> Yangtze River water>
303
seawater (Figure 1d). The presence of dissolved organic matter (DOM) appears to be the
304
main factor affecting the sorption capacities in different water matrices. The DOM content in
305
the ultrapure water, Yangtze River water and seawater was negatively correlated with the
306
BPA sorption capacity, which might be attributed to enhanced dissolution of BPA through
307
the formation of BPA/DOM complexes. Previous studies have shown that there is negligible
308
interaction between MPs and DOM,43, 64 so it is probably the combination of BPA with DOM
309
that reduces the BPA sorption capacity.
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In water environment, HOCs are likely to be present and may compete for MPs’ sorption
311
sites. The BPA sorption capacity of the various MPs did not seem to change much at E2
312
concentrations ranging from 10 to 100 μg L-1 (Figure 1e). Moreover, the sorption capacity of
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E2 was basically unaffected in binary systems compared with that in single solute systems
314
(Figure 1f). That is to say, E2 will basically not influence the sorption of BPA on MPs except
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LDPE and PC, and vice versa. However, the presence of E2 inhibits the leaking of BPA from
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LDPE and PC with different degree. It has been reported that DDT appears to have an
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antagonistic effect on the sorption of phenanthrene on MPs, because DDT (log Kow of 6.79) is
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more hydrophobic than phenanthrene (log Kow of 4.6).37, 66 The similar hydrophobicity of E2
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(log Kow of 3.94) and BPA (log Kow of 3.32) may also explain why E2 and BPA did not show
320
any synergistic or antagonistic effect on each other’s sorption. 13
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(a)
(b)
20
LDPE HDPE PC PMMA
15
LLDPE PP PVC PET
MDPE PS PA PU
4 2
10
0
5
-2
0
-4 -12
-18 0
200
400 600 -1 Ce g L
(d) 0
0
-1
-1 -1 Ultrapure water 12 ‰ salinity 24 ‰ salinity 35 ‰ salinity
-2 -12 -18
(e)
4
-2
Ultrapure water Yangtze river water Real seawater
-12 -18 (f) 3
BPA
2 0 -2 -12 -18
-1
10g L BPA -1 -1 10 g L BPA-50 g L E2 -1 50 g L BPA -1 -1 50 g L BPA-50 g L E2 -1 100 g L BPA -1 -1 100 g L BPA-50 g L E2
Qe of E2 g g-1)
Qe of BPA g g )
pH= 2.85 pH= 6.90 pH= 7.60 pH= 9.10 pH=11.10
800
(c)
321 322
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-1
50 g L E2 -1 -1 10 g L BPA + 50 g L E2 -1 -1 50 g L BPA + 50 g L E2 -1 -1 100 g L BPA + 50 g L E2
E2
2
1
0
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Figure 1. (a) The sorption isotherms of BPA (100 μg L-1) on MPs, (b) the effect of pH, (c)
324
salinity (10 μg L-1), (d) water chemistry (10 μg L-1), (e) competition of E2, and (f) the effect
325
of competition from BPA on E2 sorption (The order of MPs from left to right is as follows:
326
LDPE, LLDPE, MDPE, HDPE, PP, PS, PC, PVC, PA, PMMA, PET, and PU).
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MPs as Source for BPA.
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Leaching of BPA from Virgin MPs.
329
How likely is it that virgin LDPE and PC might release BPA into an aqueous environment? 14
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The sorption isotherms in Figure 1a suggest that a certain amount of the BPA present in
331
LDPE and PC might be leach out, depending on the BPA concentration. BPA may be present
332
as an additive or as unreacted monomer in plastics manufacture.35 The release of BPA from
333
LDPE and PC in ultrapure water was faster initially and then decreased with time to reach
334
equilibrium within 3 days (Figure 2a). The BPA amount released reached up to 2.68 μg g-1
335
from LDPE and 14.45 μg g-1 from the PC tested. While, the leaching of BPA, phthalates, and
336
citrates from 5×5 mm squares of PE, PS, PET, and PVC to reach equilibrium required 80 days
337
in simulated seawater.67 The smaller plastic particles tested here presumably shortened the
338
diffusion length from the inner part to the outer surface of the MPs in these experiments.
339
LDPE and PC can be persistent sources demonstrated through three consecutive releasing
340
cycles (inset of Figure 2a). The release of BPA into water from plastics bottles has only been
341
observed at temperatures of 80–100 °C.29,
342
sustained release of BPA from LDPE and PC at room temperature, suggesting a potential
343
environmental risk of the release of plastic additives BPA under indoor conditions.
68
But this study has demonstrated a rapid and
344
The amount of BPA released from LDPE increased slightly with increasing pH from 3.0 to
345
11.0, while BPA release from PC increased more dramatically (Figure 2b). Theoretically,
346
alkaline conditions will promote the ionization of BPA molecules and catalyze the hydrolysis
347
of PC, thus increasing solubility of BPA in water leading to its release.35 This has been
348
confirmed in research on the release of BPA from PC baby bottles into water at 80 ℃ .
349
Released BPA attained concentrations reaching up to 20 μg L-1 at pH 6 and 1010 μg L-1 at pH
350
12.30 Higher salinity, by contrast, would be expected to inhibit BPA release through
351
salting-out effect. As the water’s salinity increased from 12 ‰ to 35 ‰, the BPA released
352
capacity decreased from 2.66 to 2.19 μg L-1 on LDPE or from 14.52 to 3.15 μg L-1 on PC
353
(Figure 2c), respectively. Obviously, the inhibiting effect of salinity on BPA release is more
354
significant with PC particles (decreased by 78.2 %) than with LDPE (decreased by 17.5 %). 15
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Figure 2d shows the BPA released from LDPE or PC in different water matrices. The
356
sorption amounts are in the order Yangtze River water> ultrapure water> seawater>
357
simulated seawater> simulated physiological fluid. Considering the water matrices with the
358
same salinity (ultrapure water vs. Yangtze River water; simulated seawater vs. real seawater
359
or simulated physiological fluid), significantly more BPA was released in the real
360
environmental water, presumably due to its higher pH and the presence of DOM.64 Release of
361
BPA from both LDPE and PC was dramatically less in the simulated body fluid. Previous
362
studies reported that the presence of sodium taurocholate in simulated body fluid led to
363
greater desorption of phenanthrene, DDT, and DEHP from PE and PVC, and as much as a
364
20-fold increase in the desorption rate compared with that in seawater.8, 19 This divergence
365
may be ascribed to the fact that phenanthrene, DDT, and DEHP are not pH-sensitive
366
chemicals, whereas BPA will ionize at higher pH. Consequently, low pH (4.0) and high
367
salinity (3.5 ‰) should be responsible for the smaller release of BPA from LDPE and PC in
368
simulated physical conditions. Other factors that maybe lead to inhibit desorption of BPA
369
from MPs in simulated body fluid still need to be explored. 20
(a)
PC
40
LDPE
15 10
Released BPA (g g-1)
10
20
0
5
1st
10
2st 3st
0 0 20
0
100 200 Time (hours)
(c)
15
2 20
PC LDPE
15
10
10
5
5
0 0
370
PC LDPE
(b)
30
10 20 30 Salinity (‰)
40
4
6 pH
8
10
(d)
Ultrapure water Yangtze River water Simulated seawater Real seawater Simulated physical condition
0 LDPE
PC
371
Figure 2. BPA release from LDPE and PC as a function of (a) shaking time (with an inset
372
showing three consecutive releases from the same particles), (b) solution pH, (c) salinity, and 16
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(d) water matrices.
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Desorption of BPA from Adsorbed MPs.
375
MPs have been regarded as transporting vectors for HOCs in marine environments.13
376
Desorption of BPA from BPA/MPs combinations during transport would be expected,
377
depending on the environmental conditions.50 In this study, the BPA desorption from the
378
rubbery PEs and PP was generally greater than from the glassy PVC, PS, PMMA, PET and
379
PU (Figure 3a). It is worth mentioning that no BPA desorption from PA was observed even
380
after 120h in ultrapure water, indicating the irreversible sorption process of BPA due to
381
strong hydrogen bonding. BPA was detected in three consecutive desorption experiments
382
whether in ultrapure water or seawater (Figures 3b and 3c). A large portion of the sorbed
383
BPA (70–90 %) was desorbed from the PEs and PP over 3 cycles of desorption in ultrapure,
384
but only smaller fractions were desorbed from PS, PMMA, and PET particles (0–45 %). BPA
385
desorption was significantly lower in seawater than in ultrapure water (Figure 3c), indicating
386
an obvious salting-out effect. The desorption of BPA from PEs, PP and PVC is therefore to
387
some extent reversible, but less so from PS, PMMA, and PET. Desorption of BPA from MPs
388
in simulated physiological conditions was below the study’s detection limit (0.3 ng L-1).
389
However, a previous study has shown that the desorption of phenanthrene and DDT from PE
390
and PVC under gut conditions could be up to 30 times greater than in seawater.19 This
391
discrepancy may be because BPA is pH-sensitive compared with phenanthrene and DDT,
392
which inhibits its desorption in simulated physiological conditions.
393
To verify these results, sorption-desorption isotherms were plotted and an index of
394
hysteresis was calculated. The index results were in the order PMMA (2.69–3.81)≫ PET
395
(0.64–1.27)> PS (0.32–0.82)> PVC (0.27–0.29)> PEs and PP (0.04–0.20) (Figure S5). That
396
there was no significant desorption hysteresis with the PEs and PP suggests that the
397
desorption processes were essentially reversible. This result further indicates that the sorption 17
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of BPA in flexible, rubbery subdomains of PEs and PP is a reversible process.24 In contrast,
399
the hysteresis loops in the sorption-desorption isotherms of the glassy PVC, PS, PMMA, and
400
PET suggest that desorption was only partially reversible process due to the polymers’ rigid
401
or condensed inner structure.24 That would inhibit desorption of BPA. Irreversible molecular
402
interactions such as π-π bonding will cause such desorption hysteresis.69 Liu, however, found
403
that desorption of BPA from PS nanoparticles was essentially reversible.21 This divergence
404
can presumably be ascribed to the difference in particle sizes, but it still needs to be explored.
40 20 0 50
100
150
Time (h)
Ultrapure water
60
(b)
20
(c)
Seawater
15
40
10
20
5
0
200
25
0
st
1 desorption
LLDPE MDPE HDPE PP PS PVC PA PMMA PET PU
60
0
80
LLDPE MDPE HDPE PP PS PVC PA PMMA PET PU
(a)
LLDPE MDPE HDPE PP PS PVC PA PMMA PET PU
Desorption (%)
80
nd
2 desorption
rd
3 desorption
405 406
Figure 3. (a) Desorption kinetics of BPA from MPs, (b) 3-cycle consecutive desorption of
407
BPA from MPs in ultrapure water, (c) in seawater.
408
These kinetics, recycling and marine water experiments have demonstrated LDPE and PC
409
(Figure 2) and BPA-sorbed MPs (Figure 3) to be persistent BPA release sources in natural
410
aquatic environments. Further, BPA released from LDPE and PC under physiological
411
conditions (Figure 2d) might be an ecological risk for marine organisms. The four typical
412
marine organisms were exposed to BPA released from LDPE, PC or BPA-sorbed MPs using
413
standard exposure doses and procedures using the data provided by literature studies, which
414
did not show noticeable toxicity (Table S7), however.70, 71 With only one exception, the BPA
415
concentrations released were well below the lowest observed effect concentrations (100 ng
416
L-1) found using Japanese medaka fish.72 Overall, the long term risks arising from the release
417
of chemicals from plastic particles are complex and deserve further study.
418
Environmental Implications 18
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Due to gradual increase in the quantity of plastic debris in marine environments,73 plastic
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debris may influence the fate and transport of HOCs and could pose ecological problems. In
421
this study, MPs were verified to be potential sinks and transport vectors for BPA in marine
422
environments. Buoyant plastic pellets easily sorb HOCs and enriched them in a surface water
423
microlayer.1 They may then transport them over long distances and affect the environmental
424
and biological systems. This study has shown that BPA molecules are then continuously
425
released into the surrounding environment. The dual-mode model of sorption nicely explains
426
BPA’s sorption by various polymer particles. It may be extended to predicting the sorption
427
and environmental risks of other related HOCs. These results may therefore facilitate
428
building an improved universal sorption model for HOC sorption which allows better
429
prediction of their transport and fate and any risk they pose to aquatic environments. These
430
results may also provide a foundation for evaluating the transport, fate and potential risk of
431
other plastic additives such as bisphenol sulfonyl and bisphenol fluorine.74 In real
432
environment, the effect of bacteria,22 weathering and fragmentation of MPs, as well as the
433
formation of biofilm on MPs certainly play vital role on the BPA sorption/desorption/release
434
on/from MPs. Therefore, it is important to explore further the mechanisms of BPA
435
sorption/desorption/release on/from MPs under conditions that are as close to the real
436
environment as possible.
437
Graphic abstract
438 439
ASSOCIATED CONTENT 19
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Supporting Information
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The supporting information is available free of charge via the Internet at http://pubs.acs.org.
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BPA detection methods, calculation of hysteresis index (HI), Temporal Patterns of BPA
443
Sorption on MPs, Table S1-Table S7, and Figure S1-Figure S5.
444
■ AUTHOR INFORMATION
445
Corresponding Authors
446
*E-mails:
[email protected] and
[email protected] 447
Note
448
The authors declare that they have no competing financial interest.
449
■ ACKNOWLEDGMENTS
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This work was supported from Shanghai Natural Science Foundation (no. 19ZR1414900) and
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China’s National Key Research and Development Programs (no. 2016YFC1402204). D. D.
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Dionysiou also acknowledges support from the University of Cincinnati through a UNESCO
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co-Chair Professor Position on “Water Access and Sustainability” and the Herman Schneider
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Professorship in the College of Engineering and Applied Sciences. We kindly acknowledge
455
the reviewers and the editor for their comments that helped improve the quality of the MS.
456
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