山东大沽河溶解性碳的时空分布及影响因素

为认识河流生态系统中的碳动态分布及生物地球化学过程，基于2018—2019年的现场监测与水样分析数据，揭示山东半岛大沽河河流溶解性碳包括溶解性无机碳（DIC）和溶解性有机碳（DOC）]浓度的季节和空间特征；在此基础上，对河流CO₂分压（pCO₂）分布及影响因素进行了初步探讨。结果表明：大沽河DIC浓度分布在2.55~34.08 mg·L^-1之间，均值为（12.97±7.25）mg·L^-1；受流域地质环境、气候水文条件、梯级筑坝等因素的影响，DIC呈明显的时空差异特征（P<0.05），其在冬季最高，自上游至下游呈显著增加趋势。DOC浓度范围为4.22~62.62 mg·L^-1，均值为（15.34±10.24）mg·L^-1，高于DIC含量，因此大沽河溶解性碳总体以DOC为主；受人类活动（土地利用方式、污水排放、河流筑坝等）的强烈影响，DOC未表现出明显的时空差异。大沽河有35%的河流样点表现为大气CO₂的源；pCO₂上游明显高于中下游，夏秋季高于春冬季（P<0.05）。研究表明，大沽河光合作用总体比较强烈，导致水体中DOC浓度较高、pCO₂较低，因此大沽河总体表现为大气CO₂的汇。

Tempo-spatial distribution and its influencing factors of dissolved carbon in the Dagu River, Shandong Province

To understand the dynamic distribution and biogeochemical processes of carbon in rivers, seasonal and spatial characteristics of dissolved carbon(DIC and DOC) concentrations in the Dagu River, Shandong Peninsula, were investigated based on water samplings and analysis from 2018 to 2019. Distribution and its influencing factors of pCO₂ were evaluated. The results showed that:the DIC concentration in the Dagu River ranged from 2.55 mg·L^-1 to 34.08 mg·L^-1 with an average of(12.97±7.25) mg·L^-1. The DIC concentration was affected by geological environment, climatic and hydrological conditions, and cascade damming, which significantly varied over time and space(P<0.05); DIC was highest during winter and increased towards the downstream. The DOC concentration ranged from 4.22 mg·L^-1 to 62.62 mg·L^-1 with an average of(15.34±10.24) mg·L^-1. The DOC concentration exceeded the DIC concentration, indicating that dissolved carbon was dominated by DOC rather than DIC in the Dagu River. Moreover, there was no obvious seasonal and spatial variation for DOC, mainly owing to intense human activities, such as land use type, sewage discharge, and river damming. Thirty-five percent of the samples indicated as a source of atmospheric CO₂. pCO₂ was higher in the upper reaches than in the middle and lower reaches, and higher in summer and autumn than in spring and winter(P<0.05). In general, strong photosynthesis in the Dagu River resulted in high DOC level but low pCO₂. Therefore, the Dagu River generally displayed atmospheric CO₂ sink.