Occurrence,Bioaccumulation,and Trophic Transfer Of Organophosphate Esters In The Marine Food Webs Of Laizhou Bay

Organophosphate esters(OPEs)are emerging synthetic compounds that have been widely used as alternative flame retardants,plasticizer,and antifoaming agents in different industrial and consumer products.As the use and production of these synthetic chemicals increases,so will their discharge into different environmental compartments,especially into freshwater and marine environments over their entire lifetime,including production,usage,transportation,recycling,and disposal processes.As a result,OPEs have been detected in different matrices,the level of OPE congeners in surface water around the world is generally in the range of ng/L to tens of ?g/L,indicating the ubiquity of OPEs.Thus,aquatic organisms are exposed to OPEs and strong bioaccumulation under the environmental concentration was reported.Despite the increase in production,usage,and discharge of OPEs,little information is available about their bioaccumulation and trophic transfer behavior in the marine food web.Therefore,this dissertation research investigated the bioaccumulation potential of OPEs through a serious of laboratory experiments and field-based measurements.Seawater,sediment,and marine organisms from the coastal area of Laizhou Bay,North China,were sampled and analyzed to investigate the levels,bioaccumulation,and trophic transfer of 20 OPEs in a marine food web.The main research contents and results are summarized as follows:(1)Prior to the bioconcentration experiment,the 96 h acute median lethal concentration(i.e.,96-h LC50)of six most frequently reported OPEs to common carp(Cyprinus carpio)was determined,and ranged from 0.40-31.90 mg/L.Following that,the bioconcentration of OPEs in muscle,intestine,liver,and kidney tissues of common carp was studied under controlled laboratory conditions for 48 d.The bioconcentration kinetic parameters,including uptake rates(k1),depuration rates(k2),half-life(t1/2),and bioconcentration factors(BCFs)were evaluated.The BCFs and half-lives in the tissues ranged from 6.54(Tris(2-chloroisopropyl)phosphate,(TCPP))to 528.15(Tris(2-ethylhexyl)phosphate(TEHP)),and 2.25 to 5.78 days,respectively.The tissue-specific concentration of OPEs and BCFs values followed the order of liver>kidney? intestine>>muscle.Chemical structure specific accumulation patterns of OPE congeners group were observed.The finding of this study provides important insight for our further field-based bioaccumulation and biomagnification investigations on this group of chemicals.(2)In the field-based study,seawater,sediment,and marine organisms(10 fish and 9 invertebrate species)collected from Laizhou Bay,North China,were analyzed to investigate the occurrence,bioaccumulation,trophic transfer,and dietary health risks of 20 OPEs.Samples were determined by GC-MS,of 20 OPEs screened for,17 were quantifiable in seawater,sediment,and organisms.The ?OPEs concentrations ranged from 0.2 to 28.4 ng/L in seawater,0.1-96.9 ng/g dry weight in sediment,and 21.1 to 3510 ng/g lipid weight in organisms.Benthic fish accumulated more OPEs than pelagic fish and invertebrates.A linear and significant increase of bioaccumulation factors(BAFs)with increasing lipophilicity of OPEs was observed(R2=0.63,p<0.05),and the biota-sediment accumulation factors(BSAFs)increased with hydrophobicity up to logKow= 4.59 and then decreased with increase in logKow.Trophic magnification factors(TMFs)of OPEs ranged from 1.06 to 2.52,indicating biomagnification potential of OPEs in a marine food web.The estimated daily intake(EDI)of OPEs ranged from 1.7-12.0 and 3.1-22.1 ng/kg bw/d for rural and urban residents,respectively,which are three to five orders of magnitude lower than the available reference dose values(RfD).The hazard quotients(HQs)and hazard index(HIs)of individual OPEs were less than 0.1 for both urban and rural residents.These results showed that the human health risks of OPEs associated with seafood consumption is at low level.(3)In field-based studies,very few findings reported the levels of OPE in different tissues of aquatic biota;most studies focused only on muscle tissue.Hence,we investigated tissue-specific bioaccumulation and distribution of 20 OPEs in 10 wild marine fish species(5 benthic and 5 pelagic fish species)collected from the coastal area of Laizhou Bay.Seventeen OPEs were detected in fish tissues(including liver,kidney,gill,and muscle)with total concentration ranging from 6.6 to 107 ng/g dry weight.Relatively high levels of OPE were detected in liver,and the tissue-specific level followed the order of liver>kidney>gill?muscle for both benthic and pelagic fish.The computed ratios of OPE concentrations in other tissues to liver(OLR)were lower than 0.5 for gill and muscle tissues of all fish(p<0.01),while the OLR values of kidneys were higher than 0.5 in all fish except dotted gizzard shad(Konosirus punctatus).The mean log BAF values of OPEs ranged from 2.8 to 4.4 in livers,2.3-3.8 in muscles,2.5-3.9 in gills,and 2.8-4.4 in kidneys.The log BAF values of OPEs significantly increased with increasing their logKOW values(r=0.55-0.63,p<0.001).The living modes influenced the bioaccumulation of OPEs in the studied wild marine fish species,where benthic fish accumulated more OPEs than pelagic fish(p<0.05).Overall,the findings in this thesis provides important information about the bioaccumulation and biomagnification potential of OPEs and suggest further investigations on this group of chemicals,especially their biotransformation warrants further studies.