Research On DDT Transport And Transform In Contaminated Soil

The study was combined with the"China's National Implementation Plan for the Stockholm Convention on Persistent Organic Pollutants (POPs)-Inventory Investigation and Disposal Strategy for POPs Waste and Contaminated Sites of China"POPs contaminated site was the source of the POPs ecological harm. According to the requirements of POPs convention article 6, 1 (e) about"endeavour to develop appropriate strategies for identifying sites contaminated by chemicals listed in Annex A, B or C; if remediation of those sites is undertaken it shall be performed in an environmentally sound manner.", all the countries in the world took actions to investigate and dispose POPs contaminated site. China was the great producing country of POPs chemical, the total amount of production reached 800,000 tons in history. DDT as the largest output and most use of POPs production in China has already become the key that POPs contaminated site inventory investigation. Manufacturing enterprise was known for the most serious contaminated site by POPs that also was priority control object of POPs contaminated site environmentally sound management.After analyzed the producing history and site status of POPs manufacturing enterprises in China, three typical DDT manufacturing enterprises were selected for sampling, the DDT spatial distribution in the soil of the selected enterprises were studied, the basic characteristics of contaminated site were analyzed for the further condiation of DDT manufacturing enterprise in China, and the disposal technique selection route for DDT contaminated site was established.The main results of research were shown as follows:(1) Grid sampling interval of 20 meters can satisfy the basic demand of spatial analyse for the meso-scale research of manufacturing sites. DDTs(DDTs= p,p'-DDT+ p,p'-DDD+ o,p'-DDT+ p,p'-DDE) content variation in soil had obvious regularity, mainly relate to some natural factors. The contamination trend followed the regulation which took the production workshop as the center spreading all around, the topsoil polluted more serious than that of subsoil; with the depth increased, and the POPs residue in soil reduced gradually. If taken 50mg/kg (recommended by"Basel Convention") as identification standard, we can concluded that the area of contaminated site in the topsoil was about 1.5 times than the area of the original production workshop, the depth of the contaminated soil was about 5 meters.(2) The detecting rate of four DDT isomers in manufacturing sites was biggish, the relative content of the four DDT isomers in topsoil were p, p'-DDT>p, p'-DDD>o, p'-DDT>p, p'-DDE. The result of DDE/DDD ratio showed that the most topsoil and all subsoil of manufacturing site were in anaerobic environment, which was beneficial for DDT degradation. The result of (DDD+DDE)/DDT ratio showed that the DDT application in existing DDT manufacturing enterprise site and historical non-cleared up site of DDT manufacturing enterprise indicated that they all have the fresh application, but the sites of DDT manufacturing enterprises which cleared up their sites some years age indicated that there have only old application.(3) In addition, after reviewed POPs contaminated sites disposal technologies of foreign countries and contaminated sites disposal technique selection route of USEPA, the paper established the disposal technique selection route for POPs contaminated site of China, it mainly included data collection, contaminated site investigation, disposal target determination, preliminarily technology selection, feasibility research, technology and project determination and so on. It provided the suitable methodology for POPs contaminated site remediation technology selection to our country.