Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of

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Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of European Starlings (Sturnus vulgaris) and Congeneric Gull Species from Locations across Canada Zhe Lu, Pamela A. Martin, Neil M. Burgess, Louise Champoux, John E. Elliott, Enzo Baressi, Amila O. De Silva, Shane de Solla, and Robert J. Letcher Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b03192 • Publication Date (Web): 03 Aug 2017 Downloaded from http://pubs.acs.org on August 11, 2017

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Environmental Science & Technology

1

Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of European Starlings

2

(Sturnus vulgaris) and Congeneric Gull Species from Locations across Canada

3

Zhe Lu,† Pamela A. Martin, #* Neil M. Burgess,∥ Louise Champoux,⊥ John E. Elliott,∇ Enzo Baressi, ◊

4

Amila O. De Silva,† Shane R. de Solla, # Robert J. Letcher ¥*

5 6

†

7

Ontario, L7S 1A1 Canada

8

#

9

Ontario, L7S 1A1 Canada 

Aquatic Contaminants Research Division, Environment and Climate Change Canada, Burlington,

Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Burlington,

10

∥

11

Newfoundland and Labrador, A1N 4T3 Canada

12

⊥

13

Québec, G1J 0C3 Canada

14

∇

15

Wildlife Research Centre, Delta, British Columbia, V4K 3Y3 Canada

16

◊

17

Ontario, L7S 1A1 Canada

18

¥

19

Wildlife Research Centre, Carleton University, Ottawa, Ontario, K1A 0H3 Canada

Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Mount Pearl,

Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Québec City,

Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Pacific

National Laboratory of Environmental Testing, Environment and Climate Change Canada, Burlington,

Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, National

20 21

*

22

Robert J. Letcher (Tel.: +1-613-998-6696; e-mail: [email protected])

23

Pamela Martin (Tel.: +1-905-336-4879; e-mail: [email protected])

Co-corresponding authors:

24 1

ACS Paragon Plus Environment


25

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ABSTRACT

26

Volatile methylsiloxanes (VMSs) and organophosphate esters (OPEs) are two suites of chemicals

27

that are of environmental concern as organic contaminants, but little is known about the exposure of

28

wildlife to these contaminants, particularly in birds, in terrestrial and aquatic ecosystems. The present

29

study investigates the spatial distributions of nine cyclic and linear VMSs and seventeen OPEs in the

30

eggs of European starlings (Sturnus vulgaris), and three congeneric gull species (i.e., herring gull

31

(Larus argentatus), glaucous-winged gull (L. glaucescens) and California gull (L. californicus)) from

32

nesting sites across Canada. ∑VMS concentrations for all bird eggs were dominated by

33

decamethylcyclopentasiloxane

34

octamethylcyclotetrasiloxane (D4). With European starlings, birds breeding adjacent to landfill sites

35

had eggs containing significantly greater ∑VMS concentrations (median: 178 ng g-1 wet weight (ww))

36

compared with those from the urban industrial (20 ng g-1 ww) and rural sites (1.3 ng g-1 ww), indicating

37

that the landfills are important sources of VMSs to Canadian terrestrial environments. In gull eggs, the

38

median ∑VMS concentrations were up to 254 ng g-1 ww and suggested greater detection frequencies

39

and levels of VMSs in aquatic- versus terrestrial-feeding birds in Canada. In contrast, the detection

40

frequency of OPEs in all European starling and gull eggs was lower than 16 %. This suggested low

41

dietary exposure and/or rapid metabolism of accumulated OPEs occurs in aquatic feeding birds and

42

may warrant further investigation to elucidate the reasons for these differences.

(D5),

dodecamethylcyclohexasiloxane

43

2


(D6)

and

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44


INTRODUCTION

45

Volatile methylsiloxanes (VMSs) and organophosphate esters (OPEs) are organic compounds of

46

great environmental concern.1-4 VMSs are produced at up to several million tonnes per year globally1

47

and widely used in the manufacture of consumer and industrial products such as silicone polymers,

48

cosmetics, personal care products, defoamers, adhesives, coatings, dry cleaning solvents and industrial

49

cleaning products.1,5,6 Halogenated and non-halogenated OPEs have been used for several decades in

50

consumer and industrial products such as plastics, textiles, electronics and building materials as flame

51

retardants and plasticizers.2,3 The worldwide production of OPEs in 2007 was estimated to be about

52

341000 tonnes,3 indicating that these compounds are produced and utilized in large volumes. As flame

53

retardants, the production and use of OPEs have increased during recent years to replace the banned

54

polybrominated diphenyl ethers (PBDEs).2,3,7

55

Based on the physicochemical properties (Table S1) and use-pattern of VMSs and OPEs, these

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chemicals may easily enter the environment during manufacture, application, and waste disposal

57

processes. These compounds can volatilize to the atmosphere from VMS-containing solid and liquid

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waste.1,6,8 OPEs can leach into the environment from consumer products because they are usually not

59

chemically bound to the materials.2,9 It has been estimated that about 40 % of tris(2-chloroisopropyl)

60

phosphate (TCIPP) and 10 % of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) can be released into

61

the environment throughout the lifetime of a given product.10,11 As a consequence, OPE and VMS

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contaminants have been detected in many environmental samples such as surface water,12,13

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wastewater,6,13 biosolids,6 sediment13 and air.7,8,14,15

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Organisms may accumulate VMSs and OPEs via respiration, dermal exposure, and ingestion. The

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accumulation of these contaminants may lead to adverse effects in organisms, including endocrine

66

disruption, carcinogenicity, developmental deformity, neurotoxicity, and dermal, liver and reproductive

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toxicities.1-3 In peer-reviewed literature, the occurrence of VMSs and OPEs have been reported for

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some aquatic organisms such as plankton,16,17 invertebrate,16 and fish.4,16-18 However, the propensity for 3



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bioaccumulation of these contaminants in terrestrially foraging wildlife is unknown. It is also not clear

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if there are any differences in contamination patterns of VMSs and OPEs between aquatic and

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terrestrial wildlife. In addition, landfills have been suggested as major sources of brominated flame

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retardants such as PBDEs, to terrestrial ecosystems;19 but landfills as a source of VMS and OPE

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exposure to terrestrial wildlife is unclear. VMSs and OPEs have been detected at much higher

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concentrations than that of PBDEs in some environmental matrices.6,20,21 Thus, it is essential to identify

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the sources of VMSs and OPEs in the environment. It has been estimated that about 26 million tonnes

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(777 kg per capita) of municipal solid waste was generated in 2008 in Canada.19,22 A variety of solid

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waste types such as the containers of personal care products and cosmetics, car polish/wax, as well as

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furniture, plastics and electronics, which have been shown to contain VMSs and OPEs1,2 are disposed

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in landfills. These contaminants may escape from landfill waste and enter the environment via

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volatilization, as leachate and/or via landfill diversion (e.g., biological treatment).

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To better understand the exposure and environmental fate of VMSs and OPEs in wildlife, the

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present study investigated the concentration and composition profiles of these contaminants in

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terrestrial and aquatic bird eggs from nesting locations across Canada. The birds selected for this study

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included European starlings (Sturnus vulgaris), as well as herring gulls (Larus argentatus) and two

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congeneric species, glaucous-winged gulls (L. glaucescens) and California gulls (L. californicus).

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European starlings are terrestrial birds and live in habitats close to human activities (e.g., urban, landfill

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sites and farmland).19,23 They mainly feed on insects, spiders, seeds, grains, fruit, livestock feed and

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food waste.19,23 These properties render them ideal species for monitoring how human activities affect

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contamination by VMSs and OPEs in terrestrial ecosystems.24 As top predators, herring gulls have been

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used for many years in the spatial and temporal monitoring of environmental pollution in aquatic

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ecosystems.25 Recently, glaucous-winged gulls have been shown to be an effective contaminant

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indicator in marine environments.26,27 In the present study, we investigated (1) the concentrations,

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compositions and spatial variations of VMSs and OPEs in bird eggs collected from locations across 4


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Canada; (2) the hypothesis that landfills are an important source of VMSs and OPEs to the terrestrial

95

environment; and (3) the different contamination patterns existing between terrestrial and aquatic birds.

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To our knowledge, the study of VMSs and OPEs in European starling eggs represents the first

97

investigation of these substances in any terrestrial wildlife.

98 99

MATERIALS AND METHODS

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Samples. The bird eggs used in this study were stored and archived in Environment and Climate

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Change Canada’s National Wildlife Specimen Bank (Ottawa, ON, Canada). Fresh European starling

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eggs were collected in April/May in 2013 and 2014 from nest boxes established in 19 sampling sites

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with three different land use types: urban industrial centers (industrial districts in major cities), landfills

104

(adjacent to the major cities), and rural (agricultural) sites located either 10 km (only for OPEs study)

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or 40 km upwind from the major cities26 in Canada. The cities selected for this study included

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Vancouver, British Columbia (BC); Calgary, Alberta (AB); Hamilton, Ontario (ON); Montréal, Québec

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(QC) and Halifax, Nova Scotia (NS) (Figure S1). The reference site was selected to be at Redcliff (AB),

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which is about 300 km from Calgary (AB) (Figure S1). For each location, a maximum of 9 European

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starling eggs was pooled on an equal wet weight (ww) basis of the individual eggs.19 The pools were

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used to create egg homogenates and stored at -40 ºC prior to chemical analysis.19 European starling

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eggs were collected using methods approved by the Environment Canada Animal Care Committee, and

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a total of n = 71 and n = 101 European starling egg homogenate samples were analyzed for VMSs and

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OPEs, respectively.

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Fresh gull eggs were collected from late April to July in 2011 and 2013 from a total of 14 gull

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colonies across Canada (Figure S1). The egg samples were collected from 3 gull species, including

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glaucous-winged gulls from BC, California gull from AB and herring gulls from the remaining

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sampling locations. Gull eggs were collected under Canadian federal scientific permits. The sampling 5



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sites (Figure S1) included: Cleland Island (site BC1), Mitlenatch Island (site BC2) and Mandarte Island

119

(site BC3) from BC; Dalmead (site AB4) from AB; Great Slave Lake (site NT5) from Northwest

120

Territories (NT); Pipestone Rocks (site MB6) from Manitoba (MB); Southampton Island (site NU7)

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from Nunavut (NU); Agawa Rock (site ON8), Hamilton Harbour (site ON9, only analyzed for VMSs)

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and Tommy Thompson Park (site ON10) from ON; Ile Deslauriers (site QC11) and Ile Bellechasse

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(site QC12) from QC; Kent Island (site NB13) from New Brunswick (NB); and Gull Island (site NL14)

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from Newfoundland and Labrador (NL). For each location, a maximum of 10 gull eggs was pooled on

125

an equal ww basis of the individual eggs.25 The pools were used to create egg homogenates and stored

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at -40 ºC prior to chemical analysis. 25 A total of n = 99 and n = 114 gull egg homogenate samples were

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analyzed for VMSs and OPEs, respectively.

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Chemicals and reagents. The structures of target compounds are shown in Figure S2.

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Hexamethylcyclotrisiloxane (D3; CAS# 541-05-9; purity > 98 %), octamethylcyclotetrasiloxane (D4;

130

CAS# 556-67-2; purity > 98 %), decamethylcyclopentasiloxane (D5; CAS# 541-02-6; purity > 98 %),

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dodecamethylcyclohexasiloxane (D6; CAS# 540-97-6; purity > 98 %), Tetrakis(trimethylsiloxy)silane

132

(M4Q; CAS# 3555-47-3; purity > 95 %), hexamethyldisiloxane (L2; CAS# 107-46-0; purity > 99 %),

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octamethyltrisiloxane (L3; CAS# 107-51-7; purity > 97 %), decamethyltetrasiloxane (L4; CAS# 141-

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62-8; purity > 95 %) and dodecamethylpentasiloxane (L5; CAS# 141-63-9; purity > 95 %) were

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purchased from Gelest Inc. (Philadelphia, PA). Isotopically labeled VMS surrogate standards (Table S2)

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were purchased from Moravek (purity > 98 %; Brea, CA., U.S.A). For OPEs, triethyl phosphate (TEP;

137

CAS# 78-40-0; purity > 99%), tris (2-chloroethyl) phosphate (TCEP; CAS#115-96-8; purity > 97%),

138

tripropyl phosphate (TPP; CAS# 513-08-6; purity > 99%), triphenyl phosphate (TPHP; CAS# 115-86-6;

139

purity > 99 %), tris (2,3-dibromopropyl) phosphate (TDBPP; CAS# 126-72-7; purity > 99 %), tributyl

140

phosphate (TNBP; CAS# 126-73-8; purity > 99 %), trimethylphenyl phosphate (TMPP; CAS# 1330-

141

78-5; purity > 98 %), tris (2-butoxyethyl) phosphate (TBOEP; CAS# 78-51-3; purity > 94 %), 2-

142

ethylhexyl-diphenyl phosphate (EHDPP; CAS# 1241-94-7; purity > 98 %) and tris (2-ethylhexyl) 6


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phosphate (TEHP; CAS# 78-42-2; purity > 99%) were purchased from Sigma-Aldrich (Oakville, ON,

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Canada). TCIPP (CAS# 13674-84-5; purity > 99%), TDCIPP (CAS# 13674-87-8; purity > 95%) and

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tris(tribromoneopentyl) phosphate (TTBNPP; CAS# 19186-97-1; purity > 98 %) were purchased from

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Pfaltz & Bauer (Waterbury, CT, USA), TCI America (Portland, OR, USA) and Accustandard (New

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Haven, CT, USA), respectively. Tris (2-bromo-4-methylphenyl) phosphate (T2B4MP), tris (3-bromo-

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4-methylphenyl) phosphate (T3B4MP) and tris (4-bromo-3-methylphenyl) phosphate (T4B3MP) were

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synthesized by GL Chemtec International, (Oakville, ON, Canada) (purity > 98 %). The standard of

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2,2-bis(chloromethyl)propane-1,3-diyl

151

obtained from Dr. Heather Stapleton at Duke University (purity > 97 %). Isotopically labeled OPE

152

surrogate standards (Table S3) were purchased from Wellington Laboratories Inc. (Guelph, ON,

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Canada) (purity > 98 %). Solvents such as hexane, dichloromethane and methanol (CHROMASOLV®

154

Plus grade) were purchased from Sigma-Aldrich. Diatomaceous earth (J.T. Baker, NJ, USA) and

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sodium sulphate (Na2SO4) were heated at 600 ºC overnight in a muffle furnace prior to use. ISOLUTE

156

aminopropyl silica gel was purchased from Biotage (Charlotte, NC, USA).

tetrakis(2-chloroethyl)bis(phosphate)

(BCMP-BCEP)

was

157

Sample preparation and chemical analysis. Egg sample preparation and sample extraction and

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instrumental analysis methods have been extensively described elsewhere.4,25,28,29 However, the

159

procedures are also detailed in the supplemental information (SI). Analysis of VMSs were carried out

160

in the National Laboratory of Environmental Testing (NLET) (ultraclean lab) at the Canada Centre for

161

Inland Waters, Burlington, ON, Canada. All OPE analyses were carried out in the Organics

162

Contaminants Research Laboratory/Letcher Labs at the National Wildlife Research Centre (NWRC),

163

Carleton University, Ottawa, ON, Canada. The instrumental parameters (i.e, gas chromatograph-mass

164

spectrometry (GC-MS) for VMS analysis and liquid chromatograph-tandem mass spectrometry (LC-

165

MS-MS) for OPE analysis) are shown in Tables S2-S5.

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QA/QC. Unlike other biotic tissue or body compartment samples, bird egg contents are protected

167

by the egg shell from any possible field sampling and handling contamination of the contents. In the 7



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Sampling personnel wore clean gloves during egg sample collection and refrained from using personal

169

care products to avoid possible contamination of VMSs. An experiment was conducted to test the

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possible VMS contamination during sample storage and transportation. Organic chicken egg

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homogenates (n = 9, homogenized at 9am (n = 3), noon (n = 3) and 3pm (n = 3)), organic chicken egg

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(n = 3, with shell) and Lake Superior gull egg homogenates (n = 6) (collected in 2012) were stored in

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clean glass containers and shipped from Ottawa (ON, Canada) to Burlington (ON, Canada) (about 500

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km). Then, the egg samples were processed and analyzed in both NWRC and the ultraclean lab in

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NLET. The results showed that there was no significant background contamination occurred during

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storage and transportation for the target VMSs (Details are shown in the SI and Figure S3).

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Glass materials were used in the experiment whenever possible to limit any possible background

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organic contamination. All glassware and aluminum foil was cleaned, solvent rinsed and heated at

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450°C overnight before use to remove any possible background contamination. The outside of the egg

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shell was rinsed by solvent before accessing and retrieving the egg content. Three procedural blanks

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and one spike-recovery sample (known amount of target compounds added to 1 g of homogenized

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chicken egg) were included for the OPE analysis of all European starling eggs (10 batches). For all

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VMS and OPE analysis and measurement in the gull eggs, one procedural blank and one spike-

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recovery sample were included in each sample batch (VMSs: 9 batches for gulls, 7 batches for

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European starlings; OPEs: 8 batches for gulls). The concentrations of target compounds in blanks are

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listed in Tables S6 and S7.

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The recovery of the target compounds in spike-recovery samples were 65 ± 16 % and 73 ± 20 %

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(mean ± standard deviation (SD)) for all VMSs and OPEs, respectively. The recovery of the surrogate

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standards in egg samples were 64 ± 21 % for all VMSs and 79 ± 18 % for all OPEs (mean ± SD). The

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method limits of detection (MLODs) were defined as the concentration which produces a peak with

191

signal-to-noise (S/N) ratio of 3. The method limits of quantification (MLOQs) were based on 3 times of

8


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SD of the procedural blanks. For analytes which were not detectable in the method blanks, standard

193

concentrations producing a signal with 10 times S/N ratio in solvent were used to estimate the MLOQs.

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The MLODs and MLOQs for target compounds are shown in Tables S2, S3 and S5.

195

For VMS analysis in all eggs and OPE analysis in gull eggs, the samples were corrected using the

196

individual blank in each batch. For OPE analysis in European starling eggs, the samples were corrected

197

using the highest concentration of three blanks + 1 standard deviation in each batch. Method

198

performance for VMS was assessed by analyzing a reference material (fish tissue sample) with known

199

concentrations of D4, D5 and D6 (prepared and used in previous studies) in 7 different batches.4,30 In

200

the present study, the measured concentrations of D4, D5 and D6 in the reference material were 75 ±

201

11 %, 77 ± 13 % and 76 ± 13 % (mean ± SD) of the expected values, respectively.

202

Data Analysis. The data was statistically analyzed to determine the existence of possible

203

differences in VMS and OPE levels in eggs collected from difference sites and between difference bird

204

species. The statistical analysis of the was performed using RStudio V 0.99.903 (Boston, MA, USA)

205

and GraphPad Prism 7.0 (La Jolla, CA, USA) software. Statistics for data with censored values (≤ 50 %

206

censoring and detects > 3) were conducted using the robust regression on order statistics (ROS) method

207

in RStudio by the Nondetects and Data Analysis (NADA) package (V1.5-6).31 For the sampling sites

208

with small sample size (n ≤ 4), the censored values were substituted by 1/2 MLOQ when contaminants

209

with detection frequency ≥ 50 %.31 Non-normally distributed data (Shapiro-Wilk test) were

210

logarithmically transformed to approximate a normal distribution before being subjected to statistical

211

analysis. Unpaired two-tailed t-tests with Welch’s correction or one-way ANOVA followed by Tukey’s

212

multiple comparison test were used for the data comparison analysis. Significance level was set as p
herring gull eggs > glaucous-winged gull eggs. For example, the median concentration of

292

∑VMSs in the eggs of California gull, herring gull and glaucous-winged gull in the present study was

293

254, 110 and 56 ng g-1 ww, respectively (Figure S5). Since we do not have the egg samples of different

294

species from same sampling site, it is difficult to interpret this distribution pattern with species. The

295

VMS contamination status of their habitat and differences in feeding ecology and trophic transfer of

296

VMSs are possible factors affecting the observed distribution variations. Glaucous-winged gulls from

297

BC live in the marine environments,26,27 whereas California and herring gulls mainly feed and breed

298

inland. The aquatic birds from marine environment (e.g., seabirds from Europe or glaucous-winged

299

gulls) generally showed lower levels of VMSs compared to inland aquatic birds. Recent studies showed

300

different bioaccumulation results of VMS,16,17 depending on studied locations. For example, the

301

biodilution of VMS in marine food web has been observed in Tokyo Bay (Japan),42 which was in

302

contrast to the biomagnification in inland water foodweb.16,17 While it is also possible that in gulls there

303

are species-specific biotransformation/distribution processes influencing these compounds, such

304

knowledge is not currently available and need to be addressed in future studies.

305

The gull eggs collected from AB (254 ng g-1 ww), NL (184 ng g-1 ww) and QC (162 ng g-1 ww)

306

showed greater median ∑VMS concentrations compared with other provinces (median range: 8 - 118

307

ng g-1 ww) (Table 2, Figure S6). The lowest ∑VMS concentration was detected in the eggs from the

308

NU site which is the most northern and remote site in the present study (Figure 3). Similar spatial

309

distribution pattern was observed for the individual congeners, D5 and D6 (Figure S6). The difference

310

observed in ΣVMS concentrations between herring gull eggs from Gull (NB) and Kent (NL) Islands in

13



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Atlantic Canada (Table 2, Figures 3 and S6) may be related to the use of landfills by breeding gulls.

312

Herring gulls from Gull Island (NL) were found at nearby landfills 30 times more often than herring

313

gulls from Kent Island (NB) in Global Positioning System (GPS) telemetry studies of their movements

314

during breeding seasons from 2014-2016 (K. Shlepr, R. Ronconi & D. Fifield, unpublished data). This

315

supports our findings from European starling eggs that landfills are important sources of VMSs to the

316

Canadian environment.

317

Figure S7 illustrates the comparisons of VMS concentrations in the gull and European starling

318

eggs in BC, AB and ON. In BC, the VMS concentrations decreased in the following order: landfill site

319

European starling eggs > gull eggs > rural site European starling eggs. In contrast, different distribution

320

patterns were observed in AB and ON. That is, the gull eggs show higher or similar concentration

321

compared with the landfill and urban/industrial European starling eggs, but much higher than that of

322

the rural site European starling eggs (Figure S7). Since the sampling site of gull eggs were generally far

323

from point sources (e.g., landfills, urban/industrial area) of the target contaminants, these results

324

suggest

325

contamination/accumulation levels of VMSs compared with the terrestrial birds/ecosystems. The

326

potential biomagnification of VMS in aquatic food web is one possible explanation for the high

327

concentrations of VMS observed in the gull eggs,16,17 while it is also possible that VMSs have different

328

biotransformation and/or maternal transfer processes in gulls and European starlings. The related

329

mechanisms are worth further investigation.

that

the

aquatic

birds/ecosystems

in

Canada

may

experience

greater

330

OPEs contamination in European starling and gull eggs. Tables S9 and S10 present the

331

concentrations of OPEs in European starling and gull eggs from nesting locations across Canada,

332

respectively. The 10 OPEs detected in bird eggs were: TEP (this compound was only detected in gull

333

eggs), TCEP, TCIPP, TPHP, TDCIPP, TNBP, TMPP (this compound was only detected in European

334

starling eggs), TBOEP, EHDPP, and TEHP (this compound was only detected in one European starling

335

egg). However, the detection frequencies were all below 16 % for the 10 detected OPEs in the current 14


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study, indicating low contamination/bioaccumulation potential of these contaminants in Canadian

337

European starlings and gulls. The detection of OPEs have been reported in some aquatic biota samples

338

in Great Lakes (Table S11), 25, 29 with mean concentrations of individual OPE generally lower than 10

339

ng g-1 ww in bird eggs or tissues, which is consistent with the present study. Since OPEs have been

340

frequently detected in abiotic environmental samples with relatively high concentrations (e.g., up to 47

341

µg m-3 in air, 24 mg kg-1 in sediment and 379 ng L-1 in surface water),2 the low levels of OPEs in the

342

present bird eggs may be attributed to the rapid metabolism of OPEs in biota.3,29,43 For example, Farhat

343

et al.9 injected TCIPP and TDCIPP in fertilized chicken (Gallus gallus domesticus) eggs and detected

Volatile Methylsiloxanes and Organophosphate Esters in the Eggs of

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