Nutrient Loads Flowing into Coastal Waters from the Main Rivers of China (2006–2012)

Abstract

Based on monthly monitoring data of unfiltered water, the nutrient discharges of the eight main rivers flowing into the coastal waters of China were calculated from 2006 to 2012. In 2012, the total load of NH3-N (calculated in nitrogen), total nitrogen (TN, calculated in nitrogen) and total phosphorus (TP, calculated in phosphorus) was 5.1 × 105, 3.1 × 106 and 2.8 × 105 tons, respectively, while in 2006, the nutrient load was 7.4 × 105, 2.2 × 106 and 1.6 × 105 tons, respectively. The nutrient loading from the eight major rivers into the coastal waters peaked in summer and autumn, probably due to the large water discharge in the wet season. The Yangtze River was the largest riverine nutrient source for the coastal waters, contributing 48% of the NH3-N discharges, 66% of the TN discharges and 84% of the TP discharges of the eight major rivers in 2012. The East China Sea received the majority of the nutrient discharges, i.e. 50% of NH3-N (2.7 × 105 tons), 70% of TN (2.2 × 106 tons) and 87% of TP (2.5 × 105 tons) in 2012. The riverine discharge of TN into the Yellow Sea and Bohai Sea was lower than that from the direct atmospheric deposition, while for the East China Sea, the riverine TN input was larger.

Barriers and Bridges in Abating Coastal Eutrophication

“…Inputs of particulate nitrogen and phosphorus and dissolved silica declined due to damming of rivers, notably the construction of the Three Gorges Dam on the Chang Jiang. As opposed to the recently declining or stable nutrient loads from large rivers in Europe and North America, nitrogen and phosphorus discharges monitored from the eight main rivers flowing into the coastal waters of China increased by 40 and 75%, respectively, from 2006 to 2012 (Tong et al, 2015). While nearly half of the dissolved nitrogen and virtually all of the dissolved phosphorus loads to the Bohai Gulf in 2000 originated from human sewage, almost all of the dissolved nitrogen and nearly half of the dissolved phosphorus inputs to seas to the south emanate from agricultural sources or, in the case of nitrogen, atmospheric deposition (Strokal et al, 2014).…”

River export of nutrients to the coastal waters of China: the MARINA model to assess sources, effects and solutions

“…Inputs of total dissolved N and P to Chinese rivers by source at the sub-basin scale are quantified. Here, the study area covers the six main rivers (Tong et al 2015). These are the Yellow, Hai, Liao, Yangtze, Huai and Pearl ( for the rural population ) and of Morée et al (2013) for the urban population.…”

“…In general, these studies confirm an increase in fluxes of dissolved nutrients by rivers since the 1970s, except for Powers et al (2016) who showed a declining trend in P export by the Yangtze since 1970. Some experimental studies also report on nutrient pollution problems for inland water systems (Huang 2015;Xu et al 2014) and estuaries (Liu et al 2009b;Tong et al 2015). For example, Xu et al (2014) indicate that many Chinese rivers like Huai, Hai, Yellow and river deltas today have concentrations of nutrients at levels that do not allow for human consumption.…”

“…The large Chinese rivers contribute to the nutrient loads to the seas (Tong et al 2015). This may result in coastal eutrophication and thus in blooms of harmful algae.…”

“…This is especially important for Chinese rivers with large drainage areas (e.g., Yangtze, Yellow and Pearl) because they may discharge large amounts of nutrients (e.g., Tong et al 2015). A few sub-basin studies exist for the Yangtze river (Bao et al 2006;Liu et al 2008a;Xiao et al 2007) and for the Pearl River , but they do not account for direct manure discharges.…”