Total phosphorus concentrations in surface water of typical agro- and forest ecosystems in China, 2004–2010

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The concentrations of total phosphorus (TP) from 83 surface water sampling sites in 29 of the Chinese Ecosystem Research Network (CERN) monitored ecosystems, representing typical agro- and forest ecosystems, were assessed using monitoring data collected between 2004 and 2010 from still and flowing surface water. Results showed that, TP concentrations were significantly higher in agro-ecosystems than those in forest ecosystems both for still and flowing surface water. For agroecosystems, TP concentrations in the southern area were significantly higher than those in the northern and northwestern areas for both still and flowing surface water, however no distinct spatial pattern was observed for forest ecosystems. In general, the median values of TP within agro- and forest ecosystems did not exceed the Class V guideline for still (0.2 mg·L−1) or flowing (0.4 mg·L−1) surface water, however, surface water at some agroecosystem sampling sites was frequently polluted by TP. Elevated concentrations were mainly found in still surface water at the Changshu, Fukang, Linze and Naiman monitored ecosystems, where exceedance (>0.2 mg·L−1) frequencies varied from 43% to 78%. For flowing water, elevated TP concentrations were found at the Hailun, Changshu and Shapotou monitored ecosystems, where exceedance (>0.4 mg·L−1) frequencies varied from 29% to 100%. Irrational fertilization, frequent irrigation and livestock manure input might be the main contributors of high TP concentrations in these areas, and reduced fertilizer applications, improvements in irrigation practices and centralized treatment of animal waste are necessary to control P loss in these TP vulnerable zones.