Nitrates in Turkish waters: sources, mechanisms, impacts, and mitigation

Intensive technological developments, rapid population growth and urbanization, and excessive use of nitrogen fertilizers have caused water resources to be contaminated substantially by nitrates in Turkey. The accumulated information should be evaluated to draw a nationwide attention to the problem. The aim of this review article was to highlight the importance of nitrate (NO₃) contamination and to discuss the measures to be taken to mitigate the contamination across the nation. Agriculture, especially chemical fertilizers used in irrigated agriculture, was the most important source of NO₃ in groundwater. Also, the industrial and domestic discharges substantially contributed to NO₃ in both groundwater and surface waters in many cases. The most severe and widespread groundwater (e.g., 344 mg NO₃ L^-1 in İzmir, 476 mg L^-1 in Afyon, 477 mg L^-1 in Antalya, and 948.0 mg L^-1 in Konya) and surface water contaminations (e.g., 293.8 mg NO₃ L^-1 in İzmir, 63.3 mg L^-1 in Eskişehir, 89.8 mg L^-1 in Edirne, and 90.6 mg L^-1 in Sakarya) occurred in the regions where intensive agriculture, industrial development, and rapid urbanization were clustered. Well-established irrigation and fertilizer management plans are critical for reducing fertilizer-related NO₃ contaminations in the irrigated agriculture. Special attention should be given to the regions where industrially and domestically contaminated running water bodies are in contact with groundwater. Discharge of wastewaters to the streams, creeks, rivers, and lakes should be prevented. Well-designed studies are needed to evaluate potential health effects, including the risk of cancer, of NO₃ in drinking water.