Department of Water and Water Structures Engineering, Faculty of Engineering, Zagazig University, Zagazig 44519, Egypt.
Department of Agroecology, Aarhus University, 8830 Tjele, Denmark.
Int J Environ Res Public Health. 2020 Dec 15;17(24):9373. doi: 10.3390/ijerph17249373.
Intensive agriculture requires increasing application of fertilizers in order to sustain food production. Improper use of these substances in combination with increasing seawater intrusion results in long-term and nonpoint soil and groundwater contamination. In this work, a 3-D groundwater and solute transport numerical model was created to simulate the effect of excessive fertilizers application along the Bahr El Baqar drain system, in the eastern Nile Delta, Egypt. The geotechnical properties of the soils, hydrologic parameters, and unconfined compressive strength were determined at different sites and used as input parameters for the model. Model results showed that silty clay soils are able to contain the contaminations and preserve the groundwater quality. Nevertheless, sandy soils primarily located at the beginning of the Bahr El Baqar drain allow leakage of fertilizers to the groundwater. Thus, fertilizer application should be properly managed in the top sandy layers to protect the groundwater and soil, as increasing aquifer by excess irrigation water increased the groundwater contamination in confined layers due to the high value of cumulative salt for the current situation while the unconfined zone decreased groundwater and soil contamination. A mass transport 3-D multi-species (MT3D) model was set to identify the optimal measure to tackle soil and groundwater contamination along the Bahr El-Baqar drain system. A potential increase of the abstraction rates in the study area has a positive impact in reducing the transfer of fertilizer contamination to groundwater while it has a negative impact for soil contamination. The scenario analysis further indicated that the installation of a drainage network decreases the groundwater and soil contamination. Both solutions are potentially effective for protection against nonpoint contamination along the Bahr El Baqar drain system. However, a more sustainable management approach of fertilizer application is needed to adequately protect the receptors located further downstream in the Nile Delta.
集约农业需要增加化肥的应用，以维持粮食生产。这些物质的不当使用加上海水入侵的增加，导致了长期的非点源土壤和地下水污染。在这项工作中，创建了一个三维地下水和溶质运移数值模型，以模拟埃及尼罗河三角洲东部 Bahr El Baqar 排水系统沿线过度施用化肥的影响。不同地点的土壤岩土力学特性、水文参数和无侧限抗压强度被确定，并用作模型的输入参数。模型结果表明，粉质粘土层能够容纳污染物并保持地下水质量。然而，主要位于 Bahr El Baqar 排水系统起点的砂土层允许化肥渗漏到地下水中。因此，应在顶部砂土层中妥善管理化肥的应用，以保护地下水和土壤，因为过量灌溉水增加含水层会导致由于当前情况下累积盐值较高，承压层的地下水污染增加，而无约束区则减少了地下水和土壤污染。建立了一个三维多物质（MT3D）质量传输模型，以确定解决 Bahr El-Baqar 排水系统沿线土壤和地下水污染的最佳措施。研究区域中提取率的潜在增加对减少化肥污染向地下水的转移具有积极影响，而对土壤污染则具有负面影响。情景分析进一步表明，排水网络的安装可以减少地下水和土壤污染。这两种解决方案对于保护尼罗河三角洲下游更远地区的非点源污染都是有效的。然而，需要采取更可持续的化肥应用管理方法，以充分保护位于尼罗河三角洲下游的受体。
