摘要
土壤水稳定同位素组成的时空变化反映了区域降水与前期水分的混合及蒸散发过程。2013年7-9月对鄱阳湖湿地保护区3个断面不同土地覆盖下0-2 m剖面土壤水进行分层采样,以及采集修水和贛江的河水,测定其氢、氧稳定同位素,分析土壤水稳定同位素沿土壤剖面的变化规律、土壤水运动机制及其主要补给来源。研究结果表明,鄱阳湖采样区3个断面土壤水同位素δ^(18)O值变化范围-10.63‰—-1.17‰,其中7月份的土壤水δ^(18)O均值最小,8、9月份土壤水δ^(18)O均值相对较大。表层(0-60 cm)土壤水同位素富集可能因为蒸发作用,深层土壤水同位素组成变化因降水入渗与前期水分混合作用。不同土地覆盖表层土壤水同位素变化较大,随着深度的增加,同位素变化减少。从水分溯源上,断面一的土壤水同位素组成主要受降水的影响,断面二的土壤水同位素组成主要受赣江和降水的影响,而断面三则主要受鄱阳湖水体和降水的影响。
Soil water plays a crucial role in the hydrological cycle by, for example, delivering nutrients to plants, acting as storage to buffer deficiencies in surface water availability, and serving as a medium to transfer suspended and dissolved material. Understanding water balance processes can be aided by knowledge of the relative contributions of soil water source components, which could be a mix of recent precipitation, older groundwater, and water that has been subjected to evapotranspiration. We used stable oxygen isotopes as a geochemical tracer to identify soil water composition in a wetland area of Poyang Lake, the largest freshwater lake in China, which contains the largest single area of habitat for migratory birds. The focus was on characterizing the variation with depth of the stable isotope composition in soil water profiles, understanding the mechanisms of soil water movement, and identifying the main source of soil water recharge. Sampling was undertaken from July to September 2013 in Poyang Lake National Nature Protection Area at three wetland sites with different land cover characteristics and different degrees of proximity to the lake and river environments. Water samples collected from the Xiu and Gan rivers, which flow into the study area, and soil water sampled at 10 cm intervals over the top 200 cm, were analyzed for stable oxygen isotope composition. For all soil water samples, the value of δD relative to δ18O plotted above the global meteoric water line （GMWL） , implying an evaporation level lower than the global average. Theδ18O value of soil water from all samples ranged from -10.63‰ to -1.17‰, with mean values of -3.99‰, -4.99‰, and -5.02‰ for thethree sites. The mean δ18Ovalue of soil water was lowest in July. The stable isotope compositions of soil water were found to be mainly controlled by precipitation and evaporation. The value of δ18O declined with increasing soil depth, with most values of δ18O at depths of 10 to 60 cm ranging from -6‰ to -2‰, at depths of 80 to 150 cm ranging from -8‰ to -3‰, and at a depth of 200 cm ranging from -7‰ to -4‰. The 18O-enrichment of shallow （ 〈60 cm） soil water was probably due to evaporation, while the stable isotope composition of water in deep soil layers suggested it was a mix of recent precipitation and older groundwater. For shallow （ 〈80 cm） soil water, the three sites had a similar pattern of stable isotope composition with depth, but there were differences among sites in absolute values. At one site, stable isotope compositions of soil water were mainly influenced by precipitation ; at another site, by precipitation and Gan River water; and at the third site, by precipitation and Poyang Lake water. This study provided reference data that could make a useful contribution to the assessment of regional groundwater resources in Poyang Lake.
出处
《生态学报》
CAS
CSCD
北大核心
2015年第22期7580-7588,共9页
Acta Ecologica Sinica
基金
国家自然科学基金(51279143
71073115)
关键词
鄱阳湖
土壤水
稳定同位素
Poyang Lake
soil water
stable isotope
