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 2years (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 27.2mg/L (NH3-N, 63.5%), total P (TP) was 2.0mg/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.