| 黑河中游边缘荒漠-绿洲非饱和带土壤质地对土壤氮积累与地下水氮污染的影响 |
| 摘要点击 2357 全文点击 1173 投稿时间：2014-03-18 修订日期：2014-05-08 |
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| 中文关键词 土壤质地 土壤硝态氮积累 氮淋溶 地下水氮污染 荒漠绿洲 |
| 英文关键词 soil texture soil NO3--N accumulation N leaching groundwater NO3--N pollution desert-oasis |
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| 中文摘要 |
| 在灌溉农田生态系统，土壤剖面中硝态氮（NO3--N）的积累、分布、运移及地下水氮污染不仅受灌溉、施肥的影响，也与土壤质地有密切联系. 本研究在黑河流域中游临泽平川绿洲设置了黑河河漫滩-老绿洲农田-新垦绿洲农田-绿洲外围固沙带一个监测断面10个观测井，对地下水NO3--N含量进行连续监测，并对不同景观单元非饱和带土壤质地和NO3--N含量进行了分析，对不同质地土壤NO3--N在剖面的运移变化和氮淋溶损失进行监测. 结果表明老绿洲农田，0~300 cm土层土壤质地的垂向分布为上层砂壤土，下层为壤土和黏壤土；而新垦沙地农田在土壤剖面中也有洪积黏土层出现，但0~300 cm不同土层砂粒含量均在80%以上；绿洲外围固沙带土壤在160 cm以下出现黏土层分布；土壤NO3--N含量与黏粉粒含量呈显著相关，显著程度固沙带>新垦绿洲农田>老绿洲农田. 土壤黏粉粒含量显著影响氮的淋溶. 老绿洲农田区域，地下水NO3--N含量变动在1.01~5.17 mg ·L-1，平均2.65 mg ·L-1；新垦沙地农田区域地下水NO3--N含量变动在6.6~29.5 mg ·L-1，平均20.8 mg ·L-1，2013年5~10月平均含量为26.5 mg ·L-1，较2012年同期平均值上升了9.5 mg ·L-1；绿洲外围固沙带地下水NO3--N含量呈明显的增加趋势. 地下水浅埋区非饱和带土壤质地是土壤NO3--N淋溶损失和地下水NO3--N污染的关键控制因子. 边缘绿洲新垦沙地农田是地下水氮污染的脆弱带和高风险区域，实施有效降低地下水氮污染的种植模式及施肥和灌溉管理是区域生态农业需考虑的问题. |
| 英文摘要 |
| In irrigated agricultural ecosystems, the accumulation, distribution and transfer of nitrate nitrogen (NO3--N) in soil profile and groundwater nitrate pollution were influenced by irrigation and fertilization, and were closely related to soil textural characteristics. In this study, a monitoring section with 10 groundwater observation wells along Heihe River flood land-old oasis croplands-newly cultivated sandy croplands-fixed sandy land outside oasis was established in Pingchuan desert-oasis in Linze county in the middle of Heihe river basin, and groundwater NO3--N concentration was continuously monitored. Soil texture and NO3--N concentration in the unsaturated zone at different landscape locations were determined. The NO3--N transfer change in soil profile, nitrate leaching of soils with different texture and fertility levels in the 0-100 cm layer were analyzed. The results indicated that the vertical distribution of soil texture was sandy loam in the 0-130 cm depth, loam in the 130-190 cm and clay loam in the 190-300 cm for the old oasis croplands. For newly cultivated sandy croplands, sand content was more than 80% in each soil layer of the 0-300 cm profile, although a thin clay layer occurred in the 140-160 cm depth. The clay layer occurred 160 cm below the sand-fixing zone outside oasis. There were significant correlations between soil NO3--N concentration and silt+clay content, and the order of significant degree was the natural soils of sandy lands>the newly cultivated sandy croplands>the old oasis croplands. The loss of N leaching was closely correlated to the silt+caly content in the 0-100 cm soil depth. The groundwater NO3--N concentration varied from 1.01 to 5.17 mg ·L-1, with a mean value of 2.65 mg ·L-1 and from 6.6 to 29.5 mg ·L-1, with an average of 20.8 mg ·L-1 in the area of old oasis croplands and the newly cultivated croplands, respectively. The averaged groundwater NO3--N concentration in the area of newly cultivated sandy croplands during the period of May and October, 2013 was 26.5 mg ·L-1, which was increased by 9.5 mg ·L-1 in comparison with the same period of 2012. There was a clear increasing trend in groundwater NO3--N concentration in the sand-fixing zone outside oasis. The textural characteristics of soil unsaturated zone in the shallow groundwater distribution area was the key determining factor for controlling soil NO3--N leaching and groundwater nitrate pollution. The newly cultivated sandy croplands were the nitrate vulnerable zones and high-risk areas of groundwater nitrate pollution. The implementation of cultivation pattern and irrigation and fertilization management that could effectively reduce groundwater NO3--N pollution should be considered in the development of ecological agriculture. |
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