Zhang Shurong, Lu X X, Sun Huiguo, Han Jingtai, Higgitt David Laurence
Department of Geography, National University of Singapore, Singapore.
Sci Total Environ. 2009 Jan 1;407(2):815-25. doi: 10.1016/j.scitotenv.2008.09.022. Epub 2008 Nov 11.
This study aims to investigate the state of the riverine organic carbon in the Luodingjiang River under human impacts, such as reforestation, construction of reservoirs and in-stream damming. Seasonal and spatial characteristics of total suspended sediment (TSS), dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as C/N ratios and the stable carbon isotopic signatures of POC (delta(13)C(POC)) were examined based on a one-year study (2005) in the basin-wide scale. More frequent sampling was conducted in the outlet of the river basin at Guanliang hydrological station. DOC and POC concentrations showed flush effects with increasing water discharge and sediment load in the basin-wide scale. Atomic C/N ratio of POC had a positive relationship with TSS in the outlet of the basin, indicating the reduced aquatic sources and enhanced terrestrial sources during the high flood season. However, the similar relationship was not observed in the basin-wide scale mainly due to the spatial distributions of soil organic carbon and TSS. delta(13)C(POC) showed obvious seasonal variations with enriched values in the period with high TSS concentration, reflecting the increased contribution from C(4) plants with enhanced soil erosion. The specific flux of the total organic carbon (2.30 t km(-)(2) year(-1)) was smaller than the global average level. The ratio of DOC to POC was 1.17, which is higher than most rivers under Asian monsoon climate regime. The organic carbon flux was estimated to decline with decreasing sediment load as a result of reforestation, reservoir construction and in-stream damming, which demonstrates the impacts of human disturbances on the global carbon cycle.
本研究旨在调查罗定江在造林、修建水库和河道筑坝等人类活动影响下的河流有机碳状况。基于2005年在全流域尺度上开展的为期一年的研究，对总悬浮泥沙（TSS）、溶解有机碳（DOC）和颗粒有机碳（POC）的季节和空间特征，以及POC的C/N比和稳定碳同位素特征（δ¹³C(POC)）进行了研究。在流域出口的官良水文站进行了更频繁的采样。在全流域尺度上，DOC和POC浓度随流域内流量和泥沙负荷增加呈现出冲刷效应。流域出口处POC的原子C/N比与TSS呈正相关，表明在高洪水季节水生来源减少而陆源增强。然而，在全流域尺度上未观察到类似关系，主要是由于土壤有机碳和TSS的空间分布。δ¹³C(POC)呈现出明显的季节变化，在TSS浓度高的时期值富集，反映出随着土壤侵蚀增强C4植物的贡献增加。总有机碳的比通量（2.30 t km⁻² year⁻¹）小于全球平均水平。DOC与POC的比值为1.17，高于亚洲季风气候区的大多数河流。由于造林、修建水库和河道筑坝导致泥沙负荷减少，估计有机碳通量会下降，这表明了人类干扰对全球碳循环的影响。
