Effects of Water Table Management on Groundwater Contamination From the Use of Prometryn in Organic Soils

Abstract

In 1990, a two year study was underlaken to determine the effects of water table management on the movement of the herbicide prometryn in an organic soil in southern Qu6bec. Three water table management systems were used: controlled drainage, subsudace irrigation, and subsurface drainage. Results indicate that most of the prometryn movement through soil and into groundwater occurred during the first few months following application. In the subsurlace drainage field, the concentrations of herbicide in groundwater were mostly higher than the drinking water quality standard of 10 pg/L. When subirrigation or controlled drainage was used, the concentration fell significantly below this level, indicating their usefulness in reducing the amount of prometryn reaching the groundwater. The study also demonstrated that, in an organic soil, pesticide movement was affected mainly by the water balance. The negative water balance during dry periods caused the soil water and pesticide to move upwards. This phenomenon was enhanced when the water table was close to the soil surface and the contaminant was positioned higher in the soil profile, which improved the opporlunity for degradation of the chemical before it reached the drains. On the other hand, during high rainfall events and periods of positive water balance, the contaminant was readily leached through the soil profile. R6sum6 En 1990, une 6tude de deux ans visant d d6terminer les effets de la gestion de la nappe phr6atique sur le mouvement des prom6trynes herbicides fut entreprise dans un sol organique du Sud du Qu6bec. Trois systdmes de gestion de la nappe phr6atique furent utilises : drainage control6, l'irrigation souterraine et le drainage souterrain. Les resultats indiquent que le mouvement des prom6trynes dans le sol et dans les eaux souterraines s'est produit au cours des quelques premiers mois qui ont suivi l'application. Dans le champ de drainage souterrain, les concentrations d'herbicide dans les eaux souterraines furent pour la plupart plus 6lev6es que ce que dictent les normes de qualit6 de l'eau potable fix6es d 1o g/1. Lorsqu'on a eu recours d l'irrigation souterraine ou au drainage control6, la concentration est tomb6e consid6rablement au-dessous de ce niveau, ce qui indique qu'a la fois l'irrigation souterraine et le drainage contr0l6 constituent des m6thodes de gestion pratiques pour ce qui est de r6duire les quantit6s de prom6trynes qui parviennent aux eaux souterraines. L 6tude a r6v6l6 6galement que c'est surtout l'equilibre hydrique dans un sol organique qui a influ6 sur le mouvement des pesticides. Lequilibre hydrique n6gatif au cours des p6riodes de s6cheresse a provoqu6 la mont6e vers le haut de l Graduate Student, 2. Professor, 3-Research Associate, 5. Post Doctoral Fellow,

Probabilistic indicators for soil and groundwater contamination risk assessment

“…These instances are driven by particularly dry periods and elevated ET C , which result in high water suction in TOP and RZ from BRZ. Upward fluxes are consistent with previous observations of herbicide transport during capillary driven groundwater rise (Arjoon et al, 1998). This result may raise awareness for pollutants accumulation at soil depths that may be reached during water table fluctuations, where there may be a lack of active biodegraders.…”

ARTIFICIAL NEURAL NETWORKS FOR SUBSURFACE DRAINAGE AND SUBIRRIGATION SYSTEMS IN ONTARIO, CANADA1

“…Water table management systems that provide both subsurface drainage and subirrigation are needed to improve trafficability, increase crop yields, and reduce chemical contamination in undrained and poorly drained soil in humid areas of North America (Shady, 1989;Bengtson et al, 1993;Tan et al, 1993;Drury et al, 1996;Liaghat and Prasher, 1996;Arjoon et al, 1998). Such systems will involve the drainage!…”