Current Pollution Features,Risk Assessment And Source Analysis Of Persistent Toxic Substances In Typical Intertidal Sediments Of China

Polycyclic aromatic hydrocarbons(PAHs),polybrominated biphenyl ethers(PBDEs)and organochlorine pesticides(OCPs)are three typical types of persistent toxic substances(PTSs),which have been distributed widely in various environmental matrices.Intertidal zone,as an important field that provides comfortable living conditions for organisms,is a sink for anthropogenic pollutants.To better understand the current pollution status of these three types of PTSs in China’s intertidal zone,324 surface sediment samples from 14 typical intertidal zones spanning over 11 coastal provinces and municipalities of China were collected.To better understand the historical deposition features of OCPs in China,a sediment core in intertidal zone of Daliao River Estuary was sampled.What’s more,the distribution features,potential ecological risks,source and fate of PTSs in sediments were further analyzed.The detailed results were presented as following:In surface sediments from 14 typical intertidal zones of China,PAHs concentrations ranged from 2.311 ng/g to 1031.687 ng/g,with 3-and 4-ring PAHs being the major contaminants.From north to south China,the concentrations of PAHs showed significant spatial difference(P<0.05).PAHs concentrations in Jiulongjiang(JLJ)were significantly higher than other 13 intertidal zones(P<0.05).While the differences of PAHs concentrations from the highest tides to the lowest tides and from dry season to wet season were not significant(P>0.05).Compared with two approved sediments quality guidelines,PAHs concentrations in China’s intertidal zone sediments showed only 9% possibility of negative effects to benthonic organisms.PAHs in sediments were mainly from the combustion of coal,oil and biomass together with the leak of oil,and river runoff was a crucial pathway for PAHs to enter the intertidal zone.Sediments properties,climate parameters and anthropogenic parameters all played important roles in the distribution of PAHs in China’s intertidalzone sediments.In surface sediments from 14 typical intertidal zones of China,PBDEs concentrations ranged from 0.022 ng/g to 327.561 ng/g,with BDE209 being the main component.Spatial variations in PBDEs concentrations were also significant,with contamination levels in JLJ and Dongying(DY)observably higher than other 12 intertidal zones(P<0.05).And the differences of PBDEs concentrations from the highest tides to the lowest tides and from dry season to wet season were also not significant.PBDEs in sediments were dominantly sourced from the usage of commercial decabromodiphenyl ether(BDE209),and were positively and strongly correlated with furniture manufacturing industry in provincial and multiple manufacturing industries in river basin,which indicated river runoff was also a crucial pathway for PBDEs to enter the intertidal zone.Similarly,sediments properties,climate parameters and anthropogenic parameters all played important roles in the sources and fates of PBDEs in China’s intertidal zone sediments.In China’s 14 typical intertidal zone surface sediments,OCPs concentrations ranged from 0.051 ng/g to 4141.711 ng/g,with dichlorodiphenyltrichloroethanes(DDTs)and hexachlorocyclohexanes(HCHs)being the dominant pollutants.Similarly,from north to south China,the concentrations of OCPs showed significant spatial variations(P<0.05).OCPs concentrations in JLJ were significantly higher than other13 intertidal zones(P<0.05).And the differences of OCPs concentrations from the highest tides to the lowest tides and from dry season to wet season were also not significant.Compared with two approved sediments quality guidelines,OCPs concentrations in 9 typical intertidal zones showed zero to low risk to benthonic organisms,while OCPs concentrations in other 5 typical intertidal zones showed moderate to high risk.Notably,JLJ was most seriously polluted by OCPs that all sediments samples showed moderate to high risk to benthonic organisms.OCPs in sediments were primarily originated from the historical use of technical DDT and HCH and lindane together with the possible recent usage of technical DDT and HCH.The strong correlations between OCPs concentrations and river based anthropogenic parameters showed that river runoff was a crucial pathway for OCPs to enter the intertidal zone.Sediments properties,climate parameters and anthropogenic parameters also played important roles in the sources and fates of OCPs in China’s intertidal zone sediments.Daliao River Estuary is a typical intertidal zone of China,and OCPs concentrations in sediment core ranged from 0.496 ng/g to 5.072 ng/g,with DDTs and HCHs being the dominant contaminants.A heavy usage of technical DDT in recent20 years was implied.Risk assessment showed that only the concentrations of DDD and total DDTs occassionally(25% ~ 50%)showed negative effect to bentonic organism in the depth of 0~ 44 cm.DDTs and HCHs in sediment core of Daliao River Estuary intertidal zone were mainly from the historical use of technical DDTs and lindane.Noticeably,the transformation from aerobic environment to anaerobic environment after 1971 in Daliao River Estuary intertidal zone sediment indicated the important role anthropogenic activities played in the change.