摘要
High anthropogenic N loads and abundant bacteria are characteristic of highly contaminated urban rivers.To better understand the dispersal and accumulation of bacteria, we determined contents and isotopic compositions of suspended particulate organic matter(SPOM) and bacteria in a highly contaminated urban river(the Nanming)and effluents in winter and summer of 2013. Relative to SPOM, bacterial biomass in the river was depleted in ^(13)C and ^(15)N and its C/N ratio was lower(δ^(13)C:-33.2% ± 3.1%; δ^(15)N:-1.5% ± 1.2%; C/N:4.8 ± 0.6), while effluents showed higher ^(13)C and ^(15)N contents and C/N ratios(δ^(13)C:-25% ± 2.1%; δ ^(15)N:-8.5% ± 1.1%; C/N: 8.1 ± 1.2). Source recognition of SPOM was based on carbon isotopes because they are conservative and distinct between end-members(effluent detritus and bacterial biomass). Using a mixing model,bacterial biomass in the river was calculated to account for <20% and <56% of bulk suspended particulate organic nitrogen in winter and summer, respectively. An N budget showed that bacterial N was a small proportion of total nitrogen(<7.4%) in the riverwater.
High anthropogenic N loads and abundant bacteria are characteristic of highly contaminated urban rivers.To better understand the dispersal and accumulation of bacteria, we determined contents and isotopic compositions of suspended particulate organic matter（SPOM） and bacteria in a highly contaminated urban river（the Nanming）and effluents in winter and summer of 2013. Relative to SPOM, bacterial biomass in the river was depleted in 13^C and 15^N and its C/N ratio was lower（δ^13C：-33.2% ± 3.1%; δ^15N：-1.5% ± 1.2%; C/N：4.8 ± 0.6）, while effluents showed higher 13^C and 15^N contents and C/N ratios（δ^13C：-25% ± 2.1%; δ^15N：-8.5% ± 1.1%; C/N： 8.1 ± 1.2）. Source recognition of SPOM was based on carbon isotopes because they are conservative and distinct between end-members（effluent detritus and bacterial biomass）. Using a mixing model,bacterial biomass in the river was calculated to account for 20% and 56% of bulk suspended particulate organic nitrogen in winter and summer, respectively. An N budget showed that bacterial N was a small proportion of total nitrogen（7.4%） in the riverwater.
基金
kindly supported by the National Key Research and Development Program of China through Grant 2016YFA0601000
the National Natural Science Foundation of China through Grant 41425014
