三江平原湿地开垦对地表水中可溶性铁分布特征的影响

Impact of Reclamation Activities on Water-soluble Ionic Iron Distribution of Surface Water in the Sanjiang Plain

选取三江平原湿地开垦前后具有代表性的地表水类型,以空间换时间的方法对比分析了湿地开垦对地表水中可溶性铁(WSIFe)含量与形态分布的影响。结果表明,在田块尺度上,湿地地表积水、排水中WSIFe的含量均值分别为2.20、1.75mg·L-1;开垦为大豆田后地表无积水,排水中降为1.34mg·L-1;开垦为水田后分别增加为2.76、2.38mg·L-1,这与使用铁含量较高的地下水灌溉有关。在区域尺度上,虽然湿地开垦导致沼泽性河流中WSIFe含量降低,但目前含量(均值为0.66mg·L-1)仍高于黑龙江(0.34mg·L-1),是黑龙江WSIFe的重要来源;农田排水干渠中WSIFe含量均值为0.42mg·L-1,也是黑龙江WSIFe的来源之一,但其贡献量低于沼泽性河流;湿地开垦减少了地表水中WSIFe向黑龙江的输出。湿地开垦后地表水中Fe3+的相对含量在田块尺度上出现增加,在区域尺度上有所降低,湿地开垦前后地表水中WSIFe的主要存在形态均为Fe3+。无论是田块尺度还是区域尺度,湿地开垦后地表水中WSIFe含量的季节变化都与灌溉活动有关。

Based on the field investigation and laboratorial analysis, the concentration, distribution of water-soluble ionic iron （WSIFe） in different water environment before and after reclamation in the Sanjiang Plain were studied. The results showed that the mean contents of WSIFe in logging water and outflows of marsh were 2.20 mg·L^-1 and 1.75 mg·L^-1, respectively. When the marsh changed to be the soybean field, there was no logging water, the concentration of WSIFe in outflows decreased to be 1.34 mg·L^-1. After the soybean field converted to be the paddy field, the mean concentration of WSIFe in logging water and outflows increased to be 2.76 mg·L^-1 and 2.38 mg·L^-1, respectively, which contributed to the irrigation with groundwater of high WSIFe concentration. At regional scale, the contents of WSIFe in rivers from marsh decreased with the reclamation development, however, the mean concentration of WSIFe in rivers from marsh（0.66 mg·L^-1） were still higher than agricultural drainages（0.42 mg·L^-1）.Owing to the lower concentration of WSIFe in main Amur river（0.34 mg·L^-1）, rivers from marshes and agricultural drainages can be considered as the important WSIFe sources of the Amur river, but the marsh reclamation decreased the export of WSIFe in surface water. The relative contents of ferric iron in surface water after reclamation increased at field scale, but decreased at the regional scale. After reclamation, the seasonal change of WSIFe in surface water was linked with the irrigation activity both at the field scale and the regional scale.