摘要：This paper presents a comprehensive study of spatial and temporal patterns of water chemistry (1995-2008) in the Yesilirmak River catchment in Northern Turkey. Biological oxygen demand (BOD), dissolved oxygen (DO) and nutrient concentrations (nitrogen and phosphorus) are variable across the catchment because the upland areas are relatively undisturbed, and the lower catchment is dominated by urban, industrial and agricultural inputs. Seasonally, high nutrient concentrations occur in winter possibly due to flushing from the soil zone. Low summer flow and reduced dilution lead to high orthophosphate concentrations. However, denitrification seems to be more significant than dilution processes and this generates low nitrate concentrations in summer. Nutrient levels since 1995 do not show a significant upward trend. The current water quality status indicates that the river system is in poor condition. The majority of sites fall in the Turkish water classification class II-III and more than half fail the EU standards because of high nutrient concentrations. In order to improve the status of water quality to achieve good chemical and ecological status, there is clearly a need to improve pollution control within the river system by installing waste water treatment plants, while keeping the agricultural pollution to a minimum in the system.
关键词：Nutrients; Nitrate; Orthophosphate; Agriculture; Wastewater; Waste Water Treatment Plants
