Temporal and spatial variation of nitrogen and phosphorus and eutrophication assessment for a typical arid river—Fuyang River in northern China

Based on water quality surveys over 2 years（July to December,in 2014 and 2015） in a typical arid river in northern China the Xingtai segment of the Fuyang River basin — the variation of nitrogen（N） and phosphorus（P） was analyzed.The extent of water eutrophication of this segment was also assessed using a universal index formula for eutrophic evaluation and a logarithmic power function.The results showed that the average concentration of total N（TN） was 27.2 mg/L（NH3-N,63.5%）,total P（TP） was 2.0 mg/L（solution reactive phosphorus,68.8%）.Temporal and spatial variations of N and P in this segment were observed.Concentrations of N and P in the arid season were higher than those in the rainy season.Spatially,the N and P concentrations followed the same trend;i.e.,higher in the city segment than in the suburbs,and decreasing along the river.The water eutrophication in the studied segment reached extremely high levels at all times（eutrophication index ≥76.3）.Spatially,its trend was clearly linked with N and P.Water shortage,pollution accumulation and a weak self-purification function are the main reasons for the prominent eutrophication in this segment.