School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK; School of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK.
School of Geographical and Earth Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
Sci Total Environ. 2018 Jun 1;626:785-794. doi: 10.1016/j.scitotenv.2018.01.001. Epub 2018 Feb 19.
Assessing whether land use, from activities such as wind farm construction and tree-felling, impacts on terrestrial C delivery to rivers has focused on quantifying the loss of dissolved organic carbon (DOC), and not the composition changes. Here we explore how land use influences DOC composition by considering fluvial DOC concentration, [DOC], and spectrophotometric composition of a river draining a peat-rich catchment. We find that in this 5.7km catchment differences occur in both the concentration and composition of the DOC in its sub-catchments. This is attributed to differences in how land was used: one tributary (D-WF) drains an area with wind farm construction and forestry in the headwaters, and one tributary (D-FF) drains an area with felled plantation trees. Generally, [DOC] in both streams showed similar seasonal variation, and autumn maxima. However, the felled catchment had greater mean [DOC] than the wind farm catchment. The SUVA and E/E indicated DOC in both streams had similar aromaticity and fulvic:humic acid for most of the time, but SUVA and E/E indicated less DOC humification in the felled catchment. This may be due to young DOC from the breakdown of residual branches and roots, or more humification in soils in the wind farm area. During the dry months, DOC composition showed more spatial variation: the D-WF DOC had smaller SUVA (less total aromatic material) and SUVA (fewer humic substances). The decreased E/E in both streams indicated the total aromatic carbon decreased more than humic substances content. Moreover, the larger E/E for D-WF in summer indicated that the humic substances were richer in fulvic acids than humic acids. Soil disturbance associated with forestry-felling likely contributed to the higher [DOC] and release of less-humified material in D-FF. This research indicates drivers of different DOC concentration and composition can exist even in small catchments.
评估土地利用（如风电场建设和砍伐树木等活动）对陆地 C 向河流输送的影响，一直侧重于量化溶解有机碳（DOC）的损失，而不是组成变化。在这里，我们通过考虑富含泥炭的流域中一条河流的 DOC 浓度、DOC 和分光光度组成，来探索土地利用如何影响 DOC 的组成。我们发现，在这个 5.7km 的流域中，其支流的 DOC 浓度和组成都存在差异。这归因于土地利用方式的不同：一条支流（D-WF）流经风电场建设和上游森林的地区，另一条支流（D-FF）流经砍伐人工林的地区。通常，两条溪流的 [DOC] 都表现出相似的季节性变化和秋季最大值。然而，砍伐流域的平均 [DOC] 高于风电场流域。SUVA 和 E/E 表明，两条溪流的 DOC 在大部分时间都具有相似的芳香度和富里酸：腐殖酸，但 SUVA 和 E/E 表明砍伐流域的 DOC 腐殖化程度较低。这可能是由于残留树枝和树根分解产生的年轻 DOC，或者风电场地区土壤中的腐殖化程度较高。在旱季，DOC 组成表现出更多的空间变化：D-WF 的 DOC 具有较小的 SUVA（较少的总芳香物质）和 SUVA（较少的腐殖质）。两条溪流的 E/E 降低表明，总芳香碳减少的程度超过了腐殖质含量。此外，D-WF 在夏季的更大 E/E 表明，腐殖质中的富里酸比腐殖酸更丰富。与林业砍伐相关的土壤干扰可能导致 D-FF 中 [DOC] 升高和腐殖化程度较低的物质释放。本研究表明，即使在小流域中，不同 DOC 浓度和组成的驱动因素也可能存在。
