湘西峒河流域水化学特征及无机碳通量计算

为了掌握亚热带季风气候岩溶地区流域水化学变化特征及量化流域内岩石化学风化过程对吸收大气CO2的贡献，文章选取湘西峒河流域作为研究对象，于2016年7—8月对研究区干流和7个子流域进行了水样采集与分析。结果表明:河水pH平均值为8.31，总体呈偏碱性。EC与TDS的变化范围较大，这主要与流域内岩性的分布有关。水中离子以Ca2+、HCO-3为主，水化学类型为HCO3—Ca型，岩性控制水化学的组成。HCO-3、Ca2+和Mg2+主要来源于碳酸盐岩的风化，其余离子来源多受人为活动影响。峒河流域干流的主要离子中，HCO-3、Ca2+和Mg2+浓度从上游至下游总体下降，反映了河流从碳酸盐岩区流向碎屑岩为主地层的过程。NO-3、K+、Na+、F-、Cl-和SO2-4呈增长趋势，说明峒河受人为污染影响较大，反映出人为活动的密集程度。通过子流域的划分可知流域上游主要受灰岩以及白云岩控制，中游以灰岩控制为主，下游受砂岩、泥岩及碎屑岩控制为主。收集流域最终出口吉首观测站一个水文年的数据并运用水化学—径流法估算出峒河流域无机碳通量为60 477.33 tCO2/a，碳汇强度为71.15 tCO2/（km2·a）。

Hydrochemical characteristics and estimation of the dissolved inorganic carbon flux in the Donghe River Basin of western Hunan

In order to examine the hydrochemical characteristics and quantify the contribution of petrochemical weathering processes to the absorption of atmospheric CO2, this paper selects the Donghe River Basin in western Hunan as the study area, and 32 water samples from July, 2016 to August, 2016 were collected and analyzed. The results show that the river water has the pH value of 8.31 and is slightly alkaline. The variation ranges of EC and TDS are large, which are mainly related to the distribution of lithology in the basin. The ions in water are dominated by Ca2+ and HCO-3 and the hydrochemical type is HCO3-Ca type. The hydrochemical compositions of the water samples are affected by lithology. HCO-3, Ca2+ and Mg2+ are mainly derived from the weathering of carbonate rocks, and sources of the other ions are affected by human activities. In the main ions of the water in the Donghe River Basin, HCO-3, Ca2+ and Mg2+ show a decreasing trend from upstream to downstream, reflecting that rivers flow from carbonate rocks to clastic rocks. The growth trend of NO-3, K+, Na+, F-, Cl-and SO2-4 shows that the influence of artificial pollution on the Donghe River is significant and can reflect the intensity of human activities. It is found from the subbasin investigation that hydrochemistry of the upper reaches of the basin is mainly controlled by limestone and dolomite, the middle reaches, by limestone, and the lower reaches, by sandstone, mudstone and other clastic rocks. The observed data of a hydrological year at the Jishou observation station was collected and the hydrochemical-runoff method is used to estimate the amount of inorganic carbon flux in the Donghe River Basin as 60477.33 tCO2/a and the carbon sink intensity as 71.15 tCO2/(km2·a).