Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
Sci Total Environ. 2014 Jan 1;466-467:777-87. doi: 10.1016/j.scitotenv.2013.07.076. Epub 2013 Aug 25.
Since the 1960s, the marshes in the Sanjiang Plain, Northeast China, which are an important reservoir for dissolved carbon, have undergone long-term reclamation to farmland, resulting in elevated marsh loss and degradation on a large scale. This study compared the concentrations of dissolved carbon, as well as the chemical characteristics of dissolved organic carbon (DOC), in natural marshes, a degraded marsh, and drainage ditches sampled during the growing seasons between 2008 and 2010 to clarify the temporal-spatial variability of the dissolved carbon in the fluvial system influenced by the long-term reclamation. The results show that the average concentrations of total dissolved carbon (TDC) and DOC are considerably greater in the natural marshes than in the degraded marsh and drainage ditches. The average DOC concentration for the natural marshes, approximately 35.53 ± 5.15 mg L(-1), is approximately 2.39 times that in the degraded marsh (14.84 ± 4.21 mg L(-1)) and 2.77 times the average value in the ditches (12.84 ± 4.49 mg L(-1)). The dissolved inorganic carbon (DIC) exhibits increased trends in the drainage ditches compared with the natural marshes, whereas the hydrophobic fraction of DOC is present at lower concentrations in the degraded marsh and ditches. Fluorescence indices also indicate that the DOC in the degraded marsh and ditches has a simpler humification structure. In total, the long-term reclamation has led to great variability in the DOC concentration and chemical characteristics in the fluvial system. Changes in the DOC production potential and hydrological regimes due to sustained reclamation are deemed the predominant causes of this effect. The continuously decreased DOC concentration and high variability of DOC in the surface fluvial systems are inevitable if reclamation continues in the Sanjiang Plain. More importantly, the presence of tyrosine and tryptophan-like substances in the ditches indicates that there has been extensive agricultural organic pollution in the fluvial systems. This pollution could lead to more unexpected impacts on the downriver aquatic system. To avoid a destructive ecological crisis in the future, adjustment of the reclamation policy and agricultural management measures in the Sanjiang Plain is urgently needed.
自 20 世纪 60 年代以来，中国东北三江平原的沼泽地作为溶解碳的重要水库，经历了长期的开垦为农田，导致大规模的沼泽地丧失和退化。本研究比较了 2008 年至 2010 年生长季节期间在天然沼泽地、退化沼泽地和排水渠中采集的溶解碳浓度以及溶解有机碳（DOC）的化学特性，以阐明受长期开垦影响的河流系统中溶解碳的时空变异性。结果表明，天然沼泽地的总溶解碳（TDC）和 DOC 平均浓度明显高于退化沼泽地和排水渠。天然沼泽地的平均 DOC 浓度约为 35.53±5.15mg/L，约为退化沼泽地（14.84±4.21mg/L）的 2.39 倍，是排水渠（12.84±4.49mg/L）的 2.77 倍。与天然沼泽地相比，排水渠中的溶解无机碳（DIC）呈上升趋势，而退化沼泽地和排水渠中的疏水性 DOC 浓度较低。荧光指数也表明，退化沼泽地和排水渠中的 DOC 具有更简单的腐殖化结构。总的来说，长期开垦导致河流系统中 DOC 浓度和化学特性的巨大变化。由于持续开垦，DOC 产生潜力和水文条件的变化被认为是这种影响的主要原因。如果在三江平原继续开垦，那么地表水系统中 DOC 浓度和 DOC 变异性的不断降低是不可避免的。更重要的是，排水渠中酪氨酸和色氨酸类物质的存在表明河流系统中存在广泛的农业有机污染。这种污染可能会对下游水系统产生更多意想不到的影响。为了避免未来的生态危机，迫切需要调整三江平原的开垦政策和农业管理措施。
