Distribution And Transport Of Endosulfan In Chinese Soil And Air

Endosulfan has become a global challenge. Due to its properties of persistent organic pollutants (POPs), endosulfan has been listed as candidate substance as new POPs by the" Convention of Stockholm". It is highly possible that endosulfan will be formally added to the list of the POPs by "Convention of Stockholm" in the future.In order to reduce the amount of endosulfan in the environment, it is necessary to study the source, pathway and migration of endosulfan. This paper investigates the space distribution and spread of endosulfan in soil and atmosphere, the paper will:(1) establish gridded usage inventories of endosulfan in China with a high resolution, based on which, the endosulfan inventories of emission/residue and air/soil concentrations in China with the same resolution are established. (2) Set up monitoring sites across China to monitor the concentration of endosulfan in soil and air. (3) Assess the endosulfan inventories with the help of endosulfan soil and air monitoring data. (4) Study the soil-air exchange of endosulfan and discuss the cause of space distribution in depth.The use of endosulfan in China started in 1994, and the total usage was estimated to be approximately 25700 t between 1994 to 2004. With the supporting of usage data, endosulfan usage inventory was allocated to a grid system with 1/4°longitude by 1/6°latitude resolution, which was established from Geographic Information System (GIS) and Access Database System. On the base of usage inventory, SGPERM model was application for developing Chinese emission and residue inventories, and furthermore for Chinese soil and air concentration inventories.A survey of Chinese soil and air concurrently monitoring program was started in 2005 from 141 soil and 92 air sampling sites, in order to monitoring endosulfan in Chinese soil and air. Endosulfan was universal in Chinese soil and air due to heavily and long-term usage, and the higher concentration was always found in the area of endosulfan application. In soil samples, the concentrations ofβ-endosulfan were observed much higher than a-endosulfan, and the results were contrary in air samples, which indicated a-endosulfan is glad to volatile andβ-endosulfan prefer to reside in soil. Significant correlation between endosulfan sulfate and its parent isomers reflected that the presence of endosulfan sulfate is originated from its parent isomers. Based on multiple linear regression model, inventories of endosulfan sulfate in Chinese agricultural soil are established.In order to assess the data derived from inventories and models, comparisons between field measurements and modeling results were performed. Significant correlations were found between the modeled and monitoring endosulfan concentrations, the good agreement lends credibility to modeling results.An exchange flux trend of endosulfan between soil and air in China has been calculated by fugacity model based on measured data and simulated data. The change of exchange flux against time shows thatα-endosulfan is characteristic of primary emission in summer/autumn and secondary emission in winter.β-endosulfan features primary emission during the year. The change of exchange flux against space shows that the soil in central, estern and northeastern China is the major fate of endosulfan.