Waldron Susan, Scott E Marian, Soulsby Chris
Scottish Universities Environmental Research Centre, East Kilbride G75 0QF, United Kingdom, Department of Statistics, University of Glasgow, Glasgow G12 8QQ, United Kingdom.
Environ Sci Technol. 2007 Sep 1;41(17):6156-62. doi: 10.1021/es0706089.
River systems draining peaty catchments are considered a source of atmospheric CO2,thus understanding the behavior of the dissolved inorganic carbon pool (DIC) is valuable. The carbon isotopic composition, delta13C(DIC), and concentration, [DIC], of fluvial samples collected diurnally, over 14 months, reveal the DIC pools to be dynamic in range (-22 to -4.9% per hundred, 0.012 to 0.468 mmol L(-1) C), responding predictably to environmental influences such as changing hydrologic conditions or increased levels of primary production. delta(18)O of dissolved oxygen (DO) corroborates the delta(13)C(DIC) interpretation. A nested catchment sampling matrix reveals that similar processes affect the DIC pool and thus delta(13)C(DIC) across catchment sizes. Not so with [DIC]: at high flow, the DIC export converges across catchment size, but at low flow catchments diverge in their DIC load. Contextualizing delta(13)C with discharge reveals that organic soil-waters and groundwaters comprise end-member sources, which in varying proportions constitute the fluvial DIC pool. Discharge and pH describe well [DIC] and delta(13)C(DIC), allowing carbon to be apportioned to each end-member from continuous profiles, demonstrated here for the hydrological year 2003-2004. This approach is powerful for assessing whether the dynamic response exhibited here is ubiquitous in other fluvial systems at the terrestrial-aquatic interface or in larger catchments.
流经泥炭集水区的河流系统被认为是大气中二氧化碳的一个来源,因此了解溶解无机碳库(DIC)的行为很有价值。在14个月的时间里,每天采集的河流样本的碳同位素组成、δ13C(DIC)和浓度[DIC]表明,DIC库的范围是动态的(每千分比为-22至-4.9%,0.012至0.468 mmol L-1 C),对诸如水文条件变化或初级生产力水平提高等环境影响有可预测的响应。溶解氧(DO)的δ18O证实了δ13C(DIC)的解释。一个嵌套的集水区采样矩阵表明,类似的过程会影响DIC库,从而影响不同集水区规模的δ13C(DIC)。[DIC]的情况则不同:在高流量时,DIC输出在不同集水区规模上趋于一致,但在低流量时,集水区的DIC负荷则有所不同。将δ13C与流量情况相结合表明,有机土壤水和地下水构成了端元来源,它们以不同比例构成了河流DIC库。流量和pH值能很好地描述[DIC]和δ13C(DIC),从而可以根据连续剖面将碳分配到每个端元,这里以2003 - 2004水文年为例进行了说明。这种方法对于评估这里所展示出的动态响应在陆地 - 水生界面的其他河流系统或更大集水区中是否普遍存在很有作用。