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基于一个水文年度的月周期性采样分析,用河流悬浮颗粒物的有机碳(POC)和溶解无机碳(DIC)的同位素信号探讨了桂江径流中碳的生物地球化学循环。桂江悬浮颗粒物中POC含量多介于1.70%～14.27%之间,平均为(4.54±2.94)%;河流POC的△~(14)C值介于-235.8‰～-26.7‰之间,平均为(-135.38±57.27)‰,没有检出“核爆~(14)C”信号,揭示了较为强烈的流域地表扰动和土壤侵蚀状况。桂江POC的稳定同位素组成(δ~(13)C)变化于-29.92‰～-24.71‰之间,平均为(-26.86±1.29)‰,这与以C_3植物为主的流域生态系统的碳同位素组成一致。桂江颗粒有机质的C/N比多介于5.54～11.53之间,平均为7.97,低于全球河流的平均状况。一方面,土壤有机碳、岩石来源的地质碳及藻类生物量的混合比例决定了桂江河流颗粒有机质的C/N比和△~(14)C值;另一方面,微生物群落对水体有机质的代谢分解作用也在一定程度上改变了有机质的元素和同位素比值。桂江河流DIC的δ~(13)C值变化于-17.22‰～-10.65‰之间,平均为(-12.95±1.94)‰。冬半年河流DIC(δ~(13)C值平均为-11.47‰)几乎全部来自碳酸盐矿物的化学风化,夏半年土壤硅酸盐矿物的化学风化对DIC(δ~(13)C值平均为-14.73‰)的贡献达28%。
Based on a monthly periodic sampling analysis of a hydrological year, the biogeochemical cycles of carbon in the runoff from the Guijiang River were discussed using isotopic signals of organic carbon (POC) and dissolved inorganic carbon (DIC) from suspended particulate matter in the river. The POC content of suspended particulate matters in Guijiang River ranged from 1.70% to 14.27%, with an average of (4.54 ± 2.94)%. The △ 14 C values of river POC ranged from -235.8% to -26.7% (-135.38 ± 57.27) ‰, no “Nuclear explosion ~ (14) C” signal was detected, revealing more intense surface disturbances and soil erosion. The stable isotopic composition (δ ~ (13) C) of POC in Guijiang River changed from -29.92 ‰ to -24.71 ‰, with an average of (-26.86 ± 1.29) ‰, which was similar to that of the C_3 plant- Isotopic composition. The C / N ratio of particulate organic matter in Guijiang River ranged from 5.54 to 11.53 with an average of 7.97, lower than the average global river status. On the one hand, the ratio of C / N and △ ~ (14) C of particulate organic matter in Guijiang River is determined by the ratio of soil organic carbon, rock carbonaceous biomass and algal biomass. On the other hand, the ratio of microbial community to organic matter Metabolism also changes the elemental and isotopic ratio of organic matter to a certain extent. The δ ~ (13) C values of DIC in Guijiang River varied from -17.22 ‰ to -10.65 ‰, with an average of (-12.95 ± 1.94) ‰. In the first half of the year, the DIC (δ ~ (13) C value of the river was -11.47 ‰ on average) almost all came from the chemical weathering of carbonate minerals. The chemical weathering of silicate mineral in the first half of the year averaged the DIC (δ ~ (13) For -14.73 ‰) contribution of up to 28%.