School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia; National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW 2450, Australia.
School of Environment, Science and Engineering, Southern Cross University, Lismore, NSW 2480, Australia; National Marine Science Centre, Southern Cross University, Coffs Harbour, NSW 2450, Australia.
Sci Total Environ. 2017 Jan 1;575:545-563. doi: 10.1016/j.scitotenv.2016.09.020. Epub 2016 Sep 28.
Riverine systems act as important aquatic conduits for carbon transportation between atmospheric, terrestrial and oceanic pools, yet the magnitude of these exports remain poorly constrained. Interconnected creek and river sites (n=28) were sampled on a quarterly basis in three subcatchments of the subtropical Richmond River Catchment (Australia) to investigate spatial and temporal dynamics of dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), carbon dioxide (CO), methane (CH), and carbon stable isotope ratios (δC). The study site is an area of high interest due to potential unconventional gas (coal seam gas or coal bed methane) development. DIC exports were driven by groundwater discharge with a small contribution by in situ DOC remineralization. The DIC exports showed seasonal differences ranging from 0.10 to 0.27mmolmcatchmentd (annual average 0.17mmolmcatchmentd) and peaked during winter when surface water discharge was highest. DOC exports (sourced from terrestrial organic matter) had an annual average 0.07mmolmcatchmentd and were 1 to 2 orders of magnitude higher during winter compared to spring and summer. CO evasion rates (annual average of 347mmolmwater aread) were ~2.5 fold higher during winter compared to spring. Methane was always supersaturated (0.19 to 62.13μM), resulting from groundwater discharge and stream-bed methanogenesis. Methane evasion was highly variable across the seasons with an annual average of 3.05mmolmwater aread. During drier conditions, stable isotopes implied enhanced CH oxidation. Overall, carbon losses from the catchment were dominated by CO evasion (60%) followed by DIC exports (30%), DOC exports (9%) and CH evasion (<1%). Our results demonstrated broad catchment scale spatial and temporal variability in carbon dynamics, and that groundwater discharge and rain events controlled carbon exports.
河流系统作为大气、陆地和海洋碳库之间碳输送的重要水生通道，但这些碳输出的规模仍严重受限。本研究在澳大利亚亚热带里士满河流域的三个子流域中，对相互连接的小溪和河流站点（n=28）进行了季度采样，以调查溶解无机碳（DIC）、溶解有机碳（DOC）、二氧化碳（CO）、甲烷（CH）和碳稳定同位素比值（δC）的时空动态。由于潜在的非常规天然气（煤层气或煤层甲烷）开发，该研究地点具有很高的研究价值。DIC 的输出主要受地下水排泄的驱动，而原地 DOC 再矿化的贡献较小。DIC 的输出表现出季节性差异，范围为 0.10 至 0.27mmolmcatchmentd（年平均值为 0.17mmolmcatchmentd），在冬季地表水排放量最高时达到峰值。DOC 的输出（源自陆地有机物质）的年平均值为 0.07mmolmcatchmentd，且冬季比春季和夏季高出 1 至 2 个数量级。CO 逸出率（年平均值为 347mmolmwater aread）在冬季比春季高约 2.5 倍。由于地下水排泄和河床产甲烷作用，CH 始终处于过饱和状态（0.19 至 62.13μM）。CH 的逸出在整个季节变化很大，年平均值为 3.05mmolmwater aread。在较干燥的条件下，稳定同位素表明 CH 氧化增强。总的来说，碳从集水区的损失主要由 CO 逸出（60%）主导，其次是 DIC 输出（30%）、DOC 输出（9%）和 CH 逸出（<1%）。本研究结果表明，碳动态具有广泛的集水区尺度时空变异性，地下水排泄和降雨事件控制着碳的输出。
