Wetlands as Best Management Practices to Mitigate Agricultural Nonpoint Source Pollution

摘要: Technological advances in modern agriculture and the application of nitrogen-based synthetic fertilizers manure to agricultural crops have increased crop yields food production for world's growing population. However, a significant portion applied nitrogen is excess needs. This results leaching nitrate into groundwater eutrophication surface water systems via runoff. Agricultural pesticides are also required maintain high levels production. As result their inherent toxicity, they adverse effects on environment when leave systems. Wetlands been offered as Best Management Practices (BMPs) treatment return flows from irrigated agriculture. To investigate removal kinetics wetlands receiving drainage, field studies were conducted efficiencies determined three wetland sites (Chapter 2). Microcosm supplement data provide insight kinetics. The suggest that constructed purposes wildlife habitat can remove irrigation flows, but typically low, with mass ranging 23% 35% examined this study. Modified areal first-order rate constants (k) varied between 4.0 12.1 cm d-1. used determine saturation which was practically impossible measure field. first order microcosm (12.97 d-1) approximately equal observed k-value Ramona Lake, source sediments microcosm, suggesting value microcosms estimating rates wetlands. Measurement system showed apparent half-saturation constant (Km) maximum (Jmax) 43.8 mg L-1 4.1 g m-2 d-1 respectively, these sediments. Estimates land requirements one watershed indicated less than 3 % area would need be devoted achieve an effluent concentration 0.5 L-1, target limiting growth nuisance algae. Chlorpyrifos most widely organophosphate insecticide California's San Joaquin Valley elsewhere. While several prior evaluated effectiveness different best management practices chlorpyrifos mitigation, mostly focused sorption soils efficiency assessed by measuring inlet outlet concentrations. assess long-term performance wetlands, it important know ultimate fate Specifically, particle-associated stored transported runoff other processes Three phosphoesterase enzymes; phosphomonoesterase, phosphodiesterase phosphotriesterase, involved biotransformation pathway; however, link enzymes had not previously addressed. research presented dissertation demonstrated temporal spatial variation rates, half-lives 1 35 days under aerobic conditions 3). transformation slowed significantly anaerobic conditions, half-life 92 days. Biodegradation decreased Hospital Creek site during 2011 due flooded preceded sample collection. These allowing wet-dry cycle enhance providing dry phase encompass non-irrigation season late fall winter, again spring summer begins. There correlation phosphotriesterase activity relationship varying among sites. Phosphotriesterase activities may useful indicator biodegradation potential reference established site-specific correlations. In addition, kinetic parameters obtained laboratory model non-point pollution River (SJR) using developed quality WARMF (Watershed Analysis Risk Framework) 4). simulations about 1.8% Orestimba could reduce concentrations supporting our Chapter 2. underlined importance strategies rates. scenario enhanced more effective at reducing values below regulatory limits compared 30% use reduction scenario. From perspective view, should implemented together if possible, especially impaired waters. Given difficulty completely eliminating pesticide present crucial efforts keep within limits.