Annual Behavior of Pesticides in River and Tap Waters in Niigata City

Abstract

Concentrations of sixty-four kinds of pesticides in Shinano and Agano River waters and tap waters produced in Aoyama and Shinanogawa water treatment plants (WTP) in Niigata city were monitored twice a week from April 2007 to April 2008. The maximum and average amounts of each pesticide were made clear. The presence of pesticides in the river water correlated with the time of pesticide application to the fields. The concentrations of pesticides were reduced in the process of the rapid sand filtration systems except dichlorvos (DDVP), though the extent of reduction differed in each pesticide. The concentrations of the pesticides were remarkably decreased by the combination process of the rapid sand filtration and the granular activated carbon absorption process. A study with the same intention and method with that mentioned above was carried out in our laboratory from April 1995 to April 1996. When compared with the 90′s results, both the number and the concentrations of the pesticides were found to be decreased in 2007 and 2008.