Determination Of In-situ Toxicity And Identification Of Key Toxicants In Pore Water

As a kind of special places for chemical industrial production,chemical industry park is the area in which relatively more sources of pollution are existed.Chemicals released into the environment continuously,and they can be accumulated in sediments to high levels,bringing great risk to ecological environment and human health in surrounding area.The sediments in chemical industry park became a persistant source of pollution that can't be ignored for a long time.In the sediment system,most pollutants attach on the solid phase particles,but only the dissolved contaminants in the pore water and the rapidly desorbing contaminants are bioaccessible.Therefore,it is necessary for risk assessment and protection of ecological security in chemical industry park to carry out the research of the identification of key toxicants in the pore water.However,the existing method for toxicity identification evaluation(TIE)is limited in identification of organic compounds,and the physical and chemical conditions of sediment can be changed during transportation and storage.Thus,it is needed to establish effective method to provide technical support for the pollution evaluation and comprehensive treatment of sediment and pore water.Firstly,we improved the device of in-situ TIE and realized separation between the part of extraction and organism exposure by adding a pore water extraction device,which resolved the problems of oxygen supply and air tightness.Based on the literature and summary of traditional TIE procdure,the key toxicants in pore water could be classified into ammonia,heavy metal and organic pollutants.Artificial zeolite,metal chelating resin(Lewatit(?)TP 207)and macroporous resin(Dowex Optipore?L-493)were chose to achieve selective adsorption respectively.Daphnia magna was selected as testing organism for its high sensitivity,repeatability and stability,based on toxicity assay of typical pore water using daphnia magna,alge and zebrafish.At last,we optimized the in-situ pore water TIE in aspects of extraction,adsorption and exposure.We verified the similarity of substance in pore water obtained by centrifuged water and pumped water,which was based on spiked sediment method.The filling amount of adsorbent was determined with the rate of adsorption>90%through penetration test.The quality of Daphnia magna meet the standards of toxicity test.Category of toxicant was estimated based on the changes of toxicity before and after the resin adsorption,and toxicant identification method was established.If ammonia or heavy metal were toxicants,we could measure the concentration by Nessler's reagent colorimetry or inductively coupled plasma mass spectrometry(ICP-MS),directly.For organic toxicants,fractionation procedure was used to separate various kinds of chemicals,and protection solution was added in fraction concentration.Targeted and nontargeted screening of toxic fraction using quadrupole time-of-flight mass spectrometry(Q-TOF)were carried out to find key organic toxicants.The method of in-situ toxicity determination and identification of key toxicants in pore water was applied to 7 practical contaminated sites.The in-situ TIE results indicated that only the downstream site of a chemical plant of Jintan show significant toxicity effect,and organic compounds were the main toxicants.The results were consistent with those of traditional TIE in laboratory,verifying the reliability of in-situ TIE.The fractionation method was further applied to separate the organic extract into 15 fractionations,and fraction F-2,F-3,F-5,F-10,F-11 are responsible for the toxicity with Toxic Unit(TU):1.37,3.00,5.79,1.57 and 2.14.Tricyclazole,propiconazole,hexaconazole,tebuconazole and 2-Amino-4-methylbenzothiazole were identified as main toxicants by the targeted and nontargeted screening.Contribution rate of the 5 chemicals was 102.7%to total toxicity.In this study,the method of in-situ toxicity determination and identification of key toxicants in pore water was built and applied to contaminated sites,in which the reliability of in-situ TIE was also proved.Simultaneously,key toxicants were identified in the pore water from the downstreem of Jintan chemical industry park.Our works will provide scientific basis for the formulation of standard method of pore water toxicity identification and the management of sediments in chemical industry park.