The flux of terrigenous organic carbon through estuaries is an important and changing, yet poorly understood, component of the global carbon cycle. Using dissolved organic carbon (DOC) and fluorescence data from 13 British estuaries draining catchments with highly variable land uses, we show that land use strongly influences the fate of DOC across the land ocean transition via its influence on the composition and lability of the constituent dissolved organic matter (DOM). In estuaries draining peatland-dominated catchments, DOC was highly correlated with biologically refractory “humic-like” terrigenous material which tended to be conservatively transported along the salinity gradient. In contrast, there was a weaker correlation between DOC and DOM components within estuaries draining catchments with a high degree of human impact, that is, relatively larger percentage of arable and (sub)urban land uses. These arable and (sub)urban estuaries contain a high fraction of bioavailable “protein-like” material that behaved nonconservatively, with both DOC removals and additions occurring. In general, estuaries draining catchments with a high percentage of peatland (≥18%) have higher area-specific estuarine exports of DOC (>13 g C m⁻² yr⁻¹) compared to those estuaries draining catchments with a high percentage (≥46%) of arable and (sub)urban land uses (<2.1 g C m⁻² yr⁻¹). Our data indicate that these arable and (sub)urban estuaries tend to export, on average, ∼50% more DOC to coastal areas than they receive from rivers due to net anthropogenic derived organic matter inputs within the estuary.

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来自自然和人类影响景观的溶解有机物的河口加工对比

通过河口的陆源有机碳通量是全球碳循环的一个重要且不断变化但知之甚少的组成部分。使用来自 13 个英国河口排水集水区土地利用变化很大的溶解有机碳 (DOC) 和荧光数据，我们表明土地利用通过其对溶解成分的组成和不稳定性的影响，强烈影响了整个陆地海洋过渡中 DOC 的命运有机质 (DOM)。在排水以泥炭地为主的集水区的河口中，DOC 与生物难降解的“类腐殖质”陆源物质高度相关，这些物质倾向于沿着盐度梯度保守地运输。相比之下，在人类影响程度较高的河口排水流域内，DOC 和 DOM 组分之间的相关性较弱，即，可耕地和（郊区）城市土地使用的比例相对较大。这些可耕地和（郊区）城市河口含有高比例的生物可利用的“类蛋白质”材料，这些材料表现出非保守性，同时发生了 DOC 的去除和添加。一般来说，泥炭地比例高（≥18%）的河口排水口具有较高的特定区域 DOC 出口（>13 g C m^-2  yr ^-1 ) 与那些具有高百分比 (≥46%) 耕地和（郊区）城市土地利用（<2.1 g C m ^-2  yr ^-1）的河口排水集水区相比。我们的数据表明，由于河口内人为来源的有机物质净输入，这些可耕地和（郊区）城市河口向沿海地区输出的 DOC 比从河流中接收的 DOC 平均多约 50%。