ABSTRACT
Human society during the past several centuries has created a large number of chemical substances that oen nd their way into the environment, either intentionally applied during agricultural practices, unintentionally released from leaking industrial and municipal waste disposal sites, or stemming from research or weapons production related activities. As many of these chemicals represent a signicant health risk when they enter the food chain, contamination of both surface and subsurface water supplies has become a major issue. Modern agriculture uses an unprecedented number of chemicals, both in plant and animal production. A broad range of fertilizers, pesticides and fumigants are now routinely applied to agricultural lands, thus making agriculture one of the most important sources for non-point source pollution. e same is true for salts and toxic trace elements, which are oen an unintended consequence of irrigation in arid and semiarid regions. While many agricultural chemicals are generally benecial in surface soils, their leaching into the deeper vadose zone and groundwater may pose serious problems. us, management processes are being sought to keep fertilizers and pesticides in the root zone and prevent their transport into underlying or down-gradient water resources.
