Runoff characteristics of particulate pesticides in a river from paddy fields

Abstract

Runoff characteristics of particulate pesticides from paddy fields have been intensively observed in the Koise River in Japan. The 8 pesticides that are applied to paddy fields were analyzed in both particulate and dissolved forms. The concentrations and the detection frequencies of particulate pesticides were lower than those of dissolved pesticides. The particulate pesticide concentrations in the river water were evaluated based on the soil sorption coefficient, particulate organic carbon concentration, and dissolved pesticide concentrations. The particulate pesticide concentrations in the river were higher than evaluated concentrations because the paddy soil contained more pesticides than did suspended solids in the river water discharged during rain events, and because the desorption rates of pesticides were slow. In observations made during rains, the particulate pesticide concentrations increased with the increases in both the discharge rate and the concentrations of suspended solids. The particulate loading was slight compared with dissolved loading, but particulate pesticides may be influenced by enclosed areas such as a lake or estuary because under such conditions particulate matter settles vertically and the pesticide decomposition rate in sediment is slow compared with that in water.

High-Frequency Observations of Pesticide Runoff Characteristics in Yodo River with Reference to Three Major Tributaries

“…The prepared sample was measured using GC/MS 5050A (Shimadzu, Japan) with an RTX-5MS column (Restek, USA) after concentration by spraying with N 2 gas (Numabe et al, 1992;Ebise et al, 1993Ebise et al, , 2002Inoue et al, 2002). The pesticide names and their minimum determination limits by quantitative analysis were:…”

Concentration and loading of several pesticides in water, suspended solids and sediment during ordinary water discharge in Sugao marsh, Ibaraki Prefecture, Japan

“…Next, 5 ml of n-hexane/acetone, 1/1 (v/v), was passed through the cartridge and 7 ml of eluate was concentrated to about 1 ml with a rotary evaporator and dried under N 2 . The residue was dissolved in 3 ml (1 ml) of acetone containing 0.05 mg/ml of phenanthrene-d 10 as an internal standard and finally analyzed by GC-MS.…”

“…9,10) So, the behavior of pesticides in suspended solids in rivers and lakes should be investigated not only during rainfall event but also during ordinary water discharge.…”

Simulation Models of Pesticide Fate and Transport in Paddy Environment for Ecological Risk Assessment and Management

“…Pesticide runoff losses from paddy fields range from a few percent to more than 50% of the applied amount depending on the water management 15,27 . Monitoring of pesticide concentrations in river systems in Japan detected a number of herbicides commonly used in paddy fields 9,20,22,27 , and these herbicides may appear to have adverse effects on the aquatic ecosystem 22 . In this paper, two mathematical models developed in Japan, the PADDY and PCPF models for simulating the fate and transport of pesticide in a paddy environment are introduced.…”