Studies On POPs Residues In Vegetable Plantation Of Xi'an

In recent years, with the improvement of living standards and China's accession to the WTO, the agricultural pollution problem has aroused the public's growing concern. And domestic and foreign markets have raised a higher demand for the quality of agricultural products. Soil is the nutritional source of plants and some organisms, the contamination state of which determine the quality level of agricultural products. Persistent Organic Pollutants (POPs) is a kind of organic chemicals which is difficult to be degraded in physical, chemical or biological way, and which is natural or synthetic and semi-volatile, with highly toxic. They can long-distance migrate through atmosphere, soil, water and other medium, and can deposit back to earth, even deposit to the Earth's remote Polar Regions, and then accumulate in the body through food chain. They have induced effects to skin, liver, gastrointestinal system, the immune system and so on, and have potentially carcinogenic, teratogenic and mutagenic effects.Currently, at domestic the research about soil organic pesticide residues of POPs main focus on DDT and HCH, and less focus are put on other types of POPs residues in soil. The report about residues of such substances on the base of vegetables in Xi'an has not been seen. Therefore, this paper carried a preliminary study, analysis and assessment on the soil organic pesticides POPs substances on vegetable bases of Xi'an and the relevance to their impact on agricultural residues. Soil samples and tomato samples in uniform points of Xi'an vegetable base are well-distributed and collected; simultaneously some of Hanzhong tea garden soil is collected. POPs content of samples is measured by solid-phase extraction technology and GC-μECD. The research content and results are as follows.-(1) Setup an efficient method for determination organophosphate pesticides of POPs in soils. The POPs were extracted and associated with ultrasonic treatment from soil samples with n-hexane and acetone and cleaned up by Florisil solid-phase extraction column. Then, the extract was separated by big caliber capillary column and detected by GC withμECD detector. Fourteen POPs were separated in 22 minutes. The MDLs are 0.0048～0.0378 ng/g, the average recoveries for spiked standards in samples are 67.9%～124.6%, the relative standard deviations are 2.02%～6.26%. Residual levels of Fourteen POPs in deferent soils were also analyzed. The result shows that fourteen POPs were 100% detected in six samples. DDTs, Endrin and Heptachlor are the main residues. The average levels of DDTs in vegetable base were prominently higher than in tea plantation. The method can meet the needs of determination of trace amount POPs soil. POPs are still potentially pollutants for agricultural environment.(2) Determine POPs in the soils of Xi'an vegetable bases. POPs were detected widely in the soil. The average value of total amount of POPs in soil was 293.7μg/kg , with the primary contaminations DDTs, Endrin, Dieldrin and Aldrin whose total amount of POPs were 19.4～391.4ng/g, with the average value 110.6ng/g. The contents of the else POPs were obviously lower. Compared with the other internal region, the residual level of soil was medium, and some were exceeded the standard.(3) Determine POPs in the tomatoes of Xi'an vegetable bases. The average value of total amount of POPs in tomatoes was 211.3ng/g, with the primary contaminations Dieldrin and Aldrin, DDTs and Chlordane in sequence whose total amount of POPs were 8.0～722.5ng/g, with the average value 103.8ng/g. The contents of the else POPs were obviously lower, and some were exceeded the standard of EEC. Compared with the residual level of soil, that of tomatoes was lower. The relationship of the most POPs residues in soil and tomato were positive correlation.(4) Determine POPs tea garden soil of HanZhong. 10 kinds of POPs were all detected.The average value of total amount of POPs in tea garden soil was 88.5 ng/g, with the primary contaminations Endrin and DDTs in sequence. The contents of the else POPs were obviously lower. Compared with the residual level of DDTs (19.4～391.4ng/g , with the average value 110.6ng/g) and Endrin (22.0～151.1ng/g, with the average value 71.1 ng/g) and other POPs in vegetables soil, that of two pesticides residues (25.5～29.9ng/g, with the average value 27.1ng/g and 18.1～40.9ng/g, with the average value 29.0ng/g) in tea garden soil was lower, and other POPs residue level were similar and lower.