[Seasonal Variation on Nutrient Limitation for Phytoplankton Growth in a Coastal River-Reservoir System, Southeast China].

A comprehensive analysis was conducted using a dataset obtained from October in 2013 to October in 2014 monitoring in 20 headwater streams of Jiulong River and four reservoirs, situated in such a coastal river-reservoir system in Southeast China suffering from intensive anthropogenic disturbance. In-situ monitoring, GIS and statistical analysis were coupled in this study to identify the spatiotemporal variations of nutrients & phytoplankton abundance and community structure, the differentiation of nitrogen & phosphorus limitation of phytoplankton growth, and the seasonal variations in nutrient limitation of phytoplankton growth. The results showed that there were obvious spatiotemporal variations in terms of nutrients & phytoplankton abundance and community structure in the 20 headwater streams and four reservoirs. The concentration of nitrogen was higher in winter and spring whereas lower in summer and autumn for both 20 headwater streams and four reservoirs. However, the concentration of phosphorus showed an opposite trend. The phytoplankton's abundance was the highest in summer for four reservoirs while it was higher in winter and spring, lower in summer and autumn in the 20 headwater streams. Meanwhile, the main trend in the succession of phytoplankton was from Bacillariophyta in autumn, winter and spring to Chlorophyta in summer in Tingxi reservoir, from Chlorophyta-Cryptophyta in winter and spring to Chlorophyta-Cyanophyta in summer and autumn in Jiangdong reservoir. No obvious trend exhibited in phytoplankton succession in Shidou-Bantou reservoir and 20 headwater streams. The Redundancy analysis (RDA) ordination plots well displayed the phytoplankton's community structure and its relationships with environmental factors. Besides, according to linear regression analysis there was a closer correlation between chlorophyll-a and nutrients in four reservoirs than in 20 headwater streams. In four reservoirs, N limitation was preliminarily observed in autumn whereas P limitation exhibited in winter.

[Study on the linkage between urban built-up land and water quality in the Jiulong River watershed].

Band grouping indices combined with single band characteristic were used to extract urban built-up land based on satellite image in the Jiulong River Watershed. Landscape ecology method and statistical analysis were employed to explore the relationship between urban built-up land and permanganate index, NH4(+) -N, TP concentrations. There were significantly positive correlations between the proportion of urban built-up land and permanganate index, NH4(+) -N, TP (r = 0.701, 0.695, 0.789). It indicates the proportion of urban built-up land areas in the sub-watershed could be an effective indicator of water quality. The largest patch index (LPI) was positively correlated to permanganate index, NH4(+) -N, TP concentrations in the water (r = 0.555, 0.643, 0.722). The landscape shape index(LSI) was positively correlated to permanganate index and TP concentrations in the water (r = 0.564, 0.553). These means the impacts of urban built-up land on water quality are influenced not only by urban built-up land areas but also by spatial patterns. The seasonally linear correlation results show that water quality deteriorates quickly with urban built-up land during the flood season and dry season, and the water is susceptible to eutrophication in both flood and dry seasons. The water quality in most sub-watersheds are impacted by urban built-up land, while the urban built-up land areas of Longmen stream, Su stream and Xiao stream located in headstreams are intensive, which need to be adjusted and controlled to protect the water quality.

[Comparative study on characteristics of urban rainfall runoff from two urban lawn catchments in Macau and Xiamen].

A comparative study on characteristics of stormwater runoff from two urban lawn catchments in Macau (ELH) and Xiamen (PGH) with separated sewer system were conducted. The result obtained shows that COD, TP and NO3- -N are the major pollutants with mean EMC of 165.77-60.48 mg/L, 0.96-0.44 mg/L and 7.16-1.18 mg/L, respectively, and the mean values of pollutants loads of COD, TP and NO3- -N from study lawn catchments are 6.53-0.63 kg/hm2, 0.0375-0.0047 kg/hm2 and 0.0122-0.0128 kg/hm2, respectively. Peak values of major pollutant concentrations usually precede the flow peak. First flush effect of rainfall runoff from two study catchments is no obvious, which can be reflected by the low mean value of FF30 of TSS, COD, TP and NO3- -N, with 36.26%, 26.13%, 28.13% and 39.03%, respectively. Based on multivariate statistical analysis, first flush effect from urban lawn rainfall runoff is greatly influenced by total rainfall amount (Tr) and total runoff volume (V).

[Modelling pollutant loads and management alternatives in Jiulong River watershed with AnnAGNPS].

The modelling package Annualized Agricultural Nonpoint Source Model (AnnAGNPS) was used to predict pollutant loads, and simulate catchment processes and management practices in Jiulong River watershed, a medium-sized mountainous watershed in southeast of China. Four typical sub-watersheds were primarily chosen to calibrate AnnAGNPS model by data collected from storm events during the period of April to September, 2003. The model was further validated in the two biggest branches of Jiulong River watershed, i.e. West river and North river by the data regarding climate, and land using condition in 2002 - 2003. The simulation results show that annual total nitrogen load was 24.76kg/(hm2 x a) and 10.28kg/(hm2 x a) in the West river and North river, respectively, and annual total phosphorus load was 0.67 kg/(hm2 x a) and 0.40 kg/(hm2 x a) in the West river and North river, respectively. With the support of AnnAGNPS model, several management alternatives were separately simulated in the typical sub-watersheds, West river and North river. In the specific cell with cell-ID of 92 in Tianbao and Xiandu sub-watershed, after reforesting in sloping field, runoff surface, sediment yield, total nitrogen load and total phosphorus load cut down with 21.6%, 25.9%, 96% and 79.2%, respectively. In West river, with the cultivation plant changing from banana into rice, the total nitrogen, dissolved nitrogen, total phosphorus and dissolved phosphorus cut down with 23.83%, 25.44%, 9.08% and 19.84%, respectively. In North river, when removing all the hoggerys, nitrogen and dissolved nitrogen cut down with 63.54% and 76.92% , respectively.