Hydrolysis of pyridaphenthione and its degradation in soils

The degradation of pyridaphenthione in three different types of soils,black soil of Northeast China,red soil of Jiangxi and yellow-brown soil of Nanjing were investigated,and the effects of temperature,pH and concentrations of surfactant(SDS) on hydrolysis of pyridaphenthione in aqueous solutions were also studied in the laboratory.The results showed that the hydrolytic rate of pyridaphenthione obviously increased with the increasing temperature and pH value.The half life of pyridaphenthione was 216.56 days in pH 7 solution at 15 ℃,while 3.47 days in pH 9 solution at 35 ℃.The average temperature coefficient was 2.98.We also found that SDS could restrain the hydrolysis rates of pyridaphenthione and the restraining degree was enhanced with the increasing concentration of SDS.The degradation rates of pyridaphenthione in three kinds of soils showed the following sequence: yellow-brown soil of Nanjing black soil of northeast red soil of Jiangxi,and the half life was 10.27,78.75 and 105.00 days,respectively.The degradation rate was positively correlated with the pH values of soils.The half life of pyridaphenthione significantly extended under sterilization treatment.Among them,the half life increased by nearly 10 times in the yellow-brown soil of Nanjing,which indicated that pyridaphenthione was degraded mainly by biodegradation in soils.