A Study To Groundwater Pollution And Environmental Behaviors Of Pesticides

Pesticide pollution to groundwater has become a hotspot around the world. The effecting factors on leaching of carbofuran and atrazine, such as soil matrix, water content in soil, rainfall, macropore, and so on, were studied in laboratory. At the same time, the degradation behaviors of hexaconazole and propoxur were studied according to related test guide line from USEPA and OECD. These can provide us an effective way to defend or control the groundwater pollution.The result showed that the proportions of the detected phorate was 34.3% in 102 groundwater samples from Fujian province in July,2004.Its concentration was 0.008 -2.238 μg·L^-1, and 15.7% of them were higher than 0.1 μg·L^-1.Carbofuran and atrazine were detected in 15 samples, the detecting rate were both 14.7%,and their concentration were 0.1 - 9.1 and 0.007 - 0.062 μg·L^-1, respectively.It showed that groundwater in this area was polluted in some degree.Results showed that leaching speed of carbofuran and atrazine was lower in Henan fluvo-aquic soil than in Taihu paddy soils in laboratory. The higher the contents of soil organic matter and clay particles, the stronger the pesticides adsorbed by the soil, the less likely the pesticides get leached with water; and the more soil macropores, the more leachable the pesticides in the soil columns. Moreover, synergy was observed between adjacent macropores. The contents of the pesticides in the leachates from the soil columns inserted with 4 strainght porous glass tubes were 2.7 times as much as those from the soil columns inserted with only 2 straight glass tubes,and 10 times as much as those from the soil columns without glass tubes. When straight glass tubes were replaced by tortuose(60°) glass tubes,more pesticides remained in the soil column due to weakened leachability. The higher the solubility of the pesticide, the more leachable in the same soil column.The photodegradation of hexaconazole follow first-rate equation under 1000 W Xe lamp. Its half-life was 60.8min( 1.01h).Under 25℃,the hydrolysis half-life of hexaconazole was 178d,231d and 346d when its pH value was 5,7 and 9,respectively. But it was 139d, 178d and 277d under 50℃, respectively. The half-life of hexaconazole was 92.4d ,77.0d and 50.9d when the soils were Jiangxi red soil,Henan ehetu and Northern China heitu.