Environmental Behavior And Risk Threshold Of Soil Typical Estrogenic Endocrine Disrupting Chemicals Under Reclaimed Water Irrigation

Estrogenic endocrine disrupting chemicals(e-EDCs)are harmfiul even at concentration as low as ?g/L.The effluent of wastewater treatment plants,as well as the reclaimed water,is considered as the main source of e-EDCs.With the reclaimed water irrigation,e-EDCs could enter into soil and then migrate into crops,causing pollution to soil and risk to human health.Nonyphenol(NP)is one of the typical e-EDCs and have quite high detection frequency and concentrations in reclaimed water.In this thesis,the environmental behavior of the typical e-EDCs(NP)in soil-crop system and soil media under reclaimed water irrigation was studied through pot experiment and soil chamber test.Furthmore,the health risk assessment of NP in soil-crop system and risk threshold of soil NP were studied.The study provides a technical support for risk control of reclaimed water irrigation.Based on these issues and backgruouds,the main researches of this study were as follows:(1)The occurrence and environmental behavior of NP in soil and crops under long-term reclaimed water irrigation was analysed by pot experiment of celery,lettuce and eggplant,which were planted in artificial NP-contaminated soil with different NP concentrations and water contents.(2)The spatial distribution of NP in soil was studied under drip irrigation with reclaimed water containing different NP contents.The mechanism of NP migration and degradation in soil was analysed.(3)The health risk assessment of NP in soil-crop system was carried out,and the soil NP risk threshold based on crop and soil exposure safety was studied.The main results are as follows:(1)For different types of vegetables irrigated with reclaimed water,the NP contents in soil and plant tissues were significantly different.Firstly,the NP residual concentration in celery soil increased with the increase of initial NP concentration after harvest.However,for lettuce and eggplant,the NP residues in the soil treated with high concentration were lower than that in the soil treated with low concentration.The soil NP residue was the lowest under the soil water content of 75%field capacity,when comparing with those under the soil water content of 60%and 90%field capacity.Secondly,the NP concentration in celery root was positively correlated with the initial soil NP concentration.But for celery stem and leaf,lettuce and eggplant,there was no significant difference in NP contents between different tissues with the change of initial soil NP concentration or soil moisture.The accumulation ability of NP in root,stem,leaf and fruit varies with different vegetable types.Thirdly,the distribution of 11 NP isomers in soil and vegetable tissues was different.NP3,NP11 and NP12 were the most abundant isomers in soil.The proportion of deflferent NP isomers in plant tissues varies with vegetable species.(2)The bioaccumulation and trarslocation characteristics of NP in different types of vegetables were different.For celery plant,there was a significant negative power function correlation between the biological concentration factor(BCF)of NP and the initial soil NP concentration.For lettuce and eggplant,the BCF was not significantly affected by the initial soil NP concentration.The NP enrichment of soil with 75%FC was stronger than that with 60%FC and 90%FC.The translocation fector(TF)of vegetable aboveground decreased with the increase of the initial soil NP concentration.(3)NP in soil was mainly degraded by microorganisms and only a very small proportion was absorbed by plants.The presence of plants enhanced the degradation of NP in soil.Under the condition of reclaimed water drip irrigation,the soil NP contents showed a fluctuating decreasing trend with the increase of irrigation times and irrigation amount.(4)Under the extrem pollution load of reclaimed water irrigation,the risk of human exposure to crop NP and soil NP was 10-11-10-9 and 10-14-10-10 orders of magnitude,respectively,which was lower than the acceptable risk level of 10-6 and showed a safe condition.Considering both the crop exposure risk and the soil exposure risk,it is proposed that the risk threshold of NP in celery soil of the study area was 250 mg/kg.