Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data
Sources and ages of dissolved organic matter in peatland streams: evidence from chemistry mixture modelling and radiocarbon data
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DOI：
10.1007/s10533-010-9409-6
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发表时间：
2010-02
期刊：
影响因子：
4
通讯作者：
E. Tipping;M. Billett;C. Bryant;S. Buckingham;S. Thacker
中科院分区：
文献类型：
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作者：
E. Tipping;M. Billett;C. Bryant;S. Buckingham;S. Thacker
对1994-2007年期间的监测数据进行了分析，研究对象是英格兰北部摩尔豪斯冰川粘土和富含石灰岩的下层所覆盖的三条溪流(平房山泥炭，RS；鲑鱼贝克，TB)。溶解有机碳浓度[DOC]与流量和钙浓度[Ca]呈现复杂的关系。建立了一个基于[Ca]的模型，通过混合来自浅层泥炭的溶解有机质(DOM)来模拟河流[DOC]，通过测量泥炭孔隙水中的[DOC](L−1)(15-30 mg)来定量，并假设DOM在地下水中以恒定的浓度存在(C5 mg L−1)。需要对测量的孔隙水[DOC]进行基于温度的调整，以考虑到冬季和春季相对较低的流水[DOC]。拟合的模型令人满意地再现了河流水[DOC]的短期变化，特别是由于地下水贡献而引起的RS和Tb的变化。淡水DOM主要来源于表层泥炭，占遥感和TB总DOC通量的96%以上，占CHS总DOC通量的100%以上。模型输出与溪水和孔隙水的DO14C数据相结合，以估计泥炭和地下水中DOM的14C含量，从而估计DOM的年龄。泥炭衍生的DOM平均年龄为5岁，其中大部分是最近形成的。得出的地下水DOM的年龄(8500年)与从泥炭下粘土的水提取物DO14C估计的4000-7000年相当，这表明粘土是地下水DOM的来源。
Monitoring data over the period 1994–2007 were analysed for three streams (Cottage Hill Sike, CHS; Rough Sike, RS; Trout Beck, TB) draining blanket peat underlain by glacial clay and limestone-rich sub-strata at Moor House (Northern England). Dissolved organic carbon concentration, [DOC], showed complex relationships with both discharge and calcium concentration, [Ca]. A model based on [Ca] was constructed to simulate stream [DOC] by mixing dissolved organic matter (DOM) from shallow peat, quantified by measured [DOC] (15–30 mg l−1) in peat porewater, with DOM assumed to be present at a constant concentration (c. 5 mg l−1) in groundwater. A temperature-based adjustment to the measured porewater [DOC] was required to account for relatively low streamwater [DOC] during winter and spring. The fitted model reproduced short-term variation in streamwater [DOC] satisfactorily, in particular variability in RS and TB due to groundwater contributions. Streamwater DOM is largely derived from surface peat, which accounts for more than 96% of the total DOC flux in both RS and TB, and 100% in CHS. Model outputs were combined with streamwater and porewater DO14C data to estimate the14C contents, and thereby the ages, of DOM from peat and groundwater. The peat-derived DOM is 5 years old on average, with most of it very recently formed. The derived age of groundwater DOM (8,500 years) is comparable to the 4,000–7,000 years estimated from the DO14C of water extracts of clay underlying the peat, suggesting that the clay is the source of groundwater DOM.