漓江地表水体有机碳来源

Sources of Organic Carbon in the Surface Water of Lijiang River

科学辨识河流有机碳来源是碳循环研究的关键.本文选取典型岩溶流域漓江流域为研究对象,通过同位素示踪法、相关分析法、端元混合模型,利用碳稳定同位素、C/N对其2016年7~9月有机碳来源进行研究.结果表明:(1)DIC浓度空间分布特征为:岩溶区>岩溶区与非岩溶区的混合区>非岩溶区;干流区DIC浓度从上游到下游递增,主要受控于流域碳酸盐岩的空间分布比例.(2)DOC是构成漓江水体TOC的主体,TOC来源以内源有机碳为主,内源碳浓度空间分布特征为:岩溶区>混合区>非岩溶区,可能与岩溶区水生植物丰茂、碳酸酐酶活性较强有关,TOC中内源碳的浓度介于1.02~5.14 mg·L^(-1),平均为2.54 mg·L^(-1);TOC中内源碳的比例空间分布差异不大,平均为73.07%.(3)POC浓度、POC中内源碳的浓度及POC中内源碳的比例空间分布差异不大,POC来源以外源碳为主,POC中内源有机碳浓度介于0.01~0.16 mg·L^(-1),平均为0.05mg·L^(-1),水生生物量对漓江流域POC贡献平均为17.31%.(4)DOC浓度及内源DOC浓度空间分布均为:岩溶区>混合区>非岩溶区,DOC主要来源于水生生物的初级生产力,DOC中内源碳的浓度介于0.97~5.10 mg·L^(-1),平均为2.48 mg·L^(-1);DOC中内源碳的比例空间分布差异不大,平均为79.51%.研究水生光合生物对流域有机碳的影响,可以为岩溶碳汇稳定性科学问题的解答提供基础.

This study selected a larger typical karst basin, that of Lijiang River, as the research subject and studied the sources of organic carbon in the Lijiang basin in July, August, and September in 2016 by an isotope tracer method, a correlational analysis method, and endmember mixture model, using a stable isotope of carbon and the organic carbon to nitrogen ratio. The results showed the following. ① The spatial distribution characteristics of DIC concentration were as follows： karst area〉 karst and non-karst mixed area〉 non-karst area. The content of DIC downstream was higher than upstream. The spatial distribution of DIC concentration was mainly controlled by the distribution of carbonate rocks in the Lijiang basin. ② DOC was the main part of TOC in the Lijiang basin. TOC was mainly derived from the primary productivity of aquatic organisms. The spatial distribution characteristics of autochthonous organic carbon content were as follows： karst area〉 karst and non-karst mixed area〉 non-karst area, which may be related to more lush aquatic plants in the karst area than in the non-karst area and the carbonic anhydrase activity in the karst area being higher than in the non-karst area. The content of autochthonous organic carbon in the TOC ranged from 1.02 to 5.14 mg·L-1, with an average of 2.54 mg·L-1. There was no significant spatial difference of the proportion of autochthonous organic carbon in the TOC; it ranged from 51.68% to 85.99%, with an average of 73.07%. ③ The POC concentration, the content of autochthonous organic carbon in the POC, and the proportion of autochthonous organic carbon in the POC had no significant spatial differences. The main source of POC was allochthonous organic carbon, and the content of autochthonous organic carbon in the POC ranged from 0.01 to 0.16 mg·L-1, with an average of 0.05 mg·L-1. The proportion of autochthonous organic carbon in the POC ranged from 3.69% to 41.94%, with an average of 17.31%. ④ The spatial distribution of the content of DOC and autochthonous organic carbon in the DOC are as follows： karst area〉karst and non-karst mixed area〉non-karst area. DOC mainly came from the primary productivity of aquatic organisms. The content of autochthonous organic carbon of the DOC ranged from 0.97 to 5.10 mg·L-1, with an average of 2.48 mg·L-1. The spatial distribution of the proportion of autochthonous organic carbon in the DOC had no obvious difference and ranged from 54.43% to 94.69%, with an average of 79.51%. Studying the influence of aquatic photosynthetic organisms on organic carbon in rivers can provide basis for scientific problem solution of the stability of karst carbon sinks.