Department of Environmental Planning, Graduate School of Environmental Studies, Seoul National University, Seoul, 08826, Republic of Korea.
Department of Environmental Science, Kangwon National University, Chuncheon, 24341, Republic of Korea.
Environ Pollut. 2021 Mar 1;272:116412. doi: 10.1016/j.envpol.2020.116412. Epub 2020 Dec 30.
Forest and agricultural land use affects the concentration and composition of dissolved organic carbon (DOC) in streams and rivers. To elucidate the impacts of forest and agricultural land use on stream DOC during storm events, we investigated DOC concentration ([DOC]), optical properties of dissolved organic matter (DOM), and ΔC-DOC in both forest- and agriculture-dominated headwater streams in South Korea in the summer of 2012. One forested and five agricultural streams were investigated. During storms, the peak [DOC] of forest stream increased to 5.8 mg L, approximately two times larger than that of the most agricultural stream (3.2 mg L), demonstrating the weaker storm responses of the [DOC] of agricultural streams to hydrological change. Five PARAFAC components were identified, including three terrestrial humic-like substances (C1, C2, C3), one microbial humic substance (C4), and one microbial protein-like substances (C5). The mean (C4+C5)/(C1+C2+C3) of all storm events at the most agricultural stream was 1.5 times larger than that of the most forested stream, suggesting that more protein-like DOM is exported from agricultural watersheds. Whereas a forest stream was primarily composed of terrestrially derived and C-enriched modern DOC, the C-age of the most agricultural stream was up to ∼1000 years old. The results suggest that agricultural practices could decrease the old organic carbon pools from soils. However, how quickly the aged DOC can be degraded to CO in streams is unknown, warranting future investigation on lability of the aged DOC and their effects on CO evasion from rivers and estuaries downstream.
森林和农业土地利用会影响溪流和河流中溶解有机碳（DOC）的浓度和组成。为了阐明森林和农业土地利用对溪流 DOC 在暴雨事件中的影响，我们于 2012 年夏季在韩国的森林和农业主导的源头溪流中调查了 DOC 浓度 ([DOC])、溶解有机质（DOM）的光学特性和 ΔC-DOC。研究了一个森林溪流和五个农业溪流。在暴雨期间，森林溪流的峰值 [DOC] 增加到 5.8mg/L，约为最农业溪流（3.2mg/L）的两倍，表明农业溪流对水文变化的 [DOC] 响应较弱。确定了五个 PARAFAC 组分，包括三种陆地腐殖质样物质（C1、C2、C3）、一种微生物腐殖质物质（C4）和一种微生物蛋白样物质（C5）。在最农业溪流的所有暴雨事件中，（C4+C5）/（C1+C2+C3）的平均值是最森林溪流的 1.5 倍，这表明从农业流域输出的蛋白质样 DOM 更多。虽然森林溪流主要由陆地来源和富含 C 的现代 DOC 组成，但最农业溪流的 C 年龄高达约 1000 年。研究结果表明，农业实践可能会减少土壤中古老的有机碳库。然而，古老的 DOC 可以多快被降解为 CO 在溪流中是未知的，这需要对古老的 DOC 的不稳定性及其对下游河流和河口 CO 逸出的影响进行未来的研究。
