排灌系统底泥特征是反映土地利用变化生态影响的重要途径,为此对内蒙古河套灌区永济灌域灌排系统底泥有机碳和总氮含量进行了系统研究。结果表明:灌域内永济给水干渠(简称永济干渠)与四号、五号排水干沟(简称四排干、五排干)表层底泥的有机质(OM)及总氮(TN)含量特征分布有所差异。其中均以五排干上游底泥中含量最高,OM与TN平均值分别为3.60%和0.35%,超出河套地区平均值的4.82倍和2.94倍;其底泥有机指数也达到重污染水平,富营养化程度较高;永济干渠底泥OM与TN含量最低,分别为1.41%和0.03%,属于清洁贫营养化级别;四排干底泥OM与TN含量介于五排干和永济干渠之间,其上游较为清洁,基本接近平均值,C/N平均在17左右。排干底泥有机质与总氮含量之间显著相关,y(TN)=0.141x(OM)-0.180(r=0.978;P<0.001)。
The differences in different land-use patterns result in differences in contents of organic matter and total nitrogen in sediments of irrigation and drainage system, so we analyzed the characteristics in sediments in Yongji Irrigation Sub-District of Hetao Irrigation District in Northern China. The results showed that there was s difference in organic matter and total nitrogen contents between the surface sediments in the Canal and Drains. The highest content of organic matter and total nitrogen was in the upstream of the Fifth Drain and the mean value was 3.60% and 0.35%, respectively. The corresponding value was 4.82 times and 2.94 times higher than the average value of organic matter and total nitrogen. The organic indices showed that the contamination standard in sediments in the Fifth Drain was heavy and implied that eutrophication problem was serious; The lowest value in sediment was found in the Yongji Canal, while the mean value was 1.41% and 0.03% for organic matter and total nitrogen, respectively, which was considered as clean category. The content of organic matter and total nitrogen in the upstream of the Forth Drain was moderate, and close to the background value. Organic matter was significantly correlated to the total nitrogen in sediments: y(TN)=0.141x(OM)-0.180 (r=0.978,P<0.001).
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