Abstract
Given the water scarcity becoming endemic to a large portion of the globe, arid region irrigation has resorted to the use of treated, partially treated, or even untreated wastewaters. Such waters contain a number of pollutants, including surfactants. Applied to agricultural lands, these surfactants could affect the fate and transport of other chemicals in the soil, particularly pesticides. A field lysimeter study was undertaken to investigate the effect of nonionic surfactant, Brij35, on the in-soil fate and transport of a commonly used herbicide, metribuzin [4-amino-6-tert-butyl-3-(methylthio)-1,2,4-triazin-5(4H)-one]. Nine PVC lysimeters, 1.0 m long × 0.45 m diameter, were packed with a sandy soil to a bulk density of 1.35 mg m−3. Antibiotic-free cattle manure was applied (10 mg ha−1) at the surface of the lysimeters. Metribuzin was then applied to the soil surface of all lysimeters at a rate of 1.00 kg a.i. ha−1. Each of three aqueous Brij35 solutions, 0, 0.5 and 5 mg L−1 (i.e., “good”, “poor” and “very poor” quality irrigation water) were each applied to the lysimeters in triplicate. Analysis for metribuzin residues in samples of both soil and leachate, collected over a 90-day period, showed the surfactant Brij35 to have increased the mobility of metribuzin in soil, indicating that continued use of poor quality water could influence pesticide transport in agricultural soils, and increase the risk of groundwater contamination.
Highlights
Water is a very complex and dynamic resource and the estimated amount of the available water on the planet is 140 billion km3, only 3% is fresh water [1]
Results revealed that the amount of metribuzin sorbed was higher in the absence of Brij35; it decreased in the presence of Brij35 at concentrations above critical micelle concentration (CMC)
Understanding the mobility of metribuzin within soil-water-surfactant systems is an important step in evaluating the risk resulting from irrigation with wastewater
Summary
Water is a very complex and dynamic resource and the estimated amount of the available water on the planet is 140 billion km, only 3% is fresh water [1]. Due to the distribution of fresh water resources around the globe, less than 1% of these resources are available for human use. Water scarcity combined with poverty is forcing the reuse of untreated or partially-treated wastewater for irrigation in order to cope with the high food demands of growing populations [2]. A recent survey revealed that the 46 countries, representing 75% of the world’s irrigated land, use polluted water for irrigation [4]. An estimated 20 million ha of land are irrigated with wastewater, and this area is expected to markedly increase in the few years [5]
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