砂姜黑土区采煤塌陷坡耕地氮磷时空分布与流失特征

Temporal-spatial Distribution and Loss Characteristics of Nitrogen and Phosphorus from Sope Farmland in Coal Mining Subsidence Aeas with Lime Concretion Black Soil

[目的]研究砂姜黑土区采煤塌陷坡耕地动态过程中表层土壤NH＋4—N和有效磷（AP）的时空分布,揭示氮磷随地表径流流失的雨强和坡度变化特征。[方法]选择淮北平原砂姜黑土区两类不同煤矿井工开采方式引发的地表塌陷坡耕地,动态监测表层土壤中NH＋4—N和AP含量,并在实验室应用人工模拟降雨,测定2种雨强和3种坡度处理的地表径流中可溶态及颗粒态NH＋4—N,AP含量。[结果]（1）充填开采地表塌陷坡耕地表层土壤中NH＋4—N含量为16.5~72.0mg/kg,AP为26.0~63.5mg/kg,非充填开采分别为9.08~67.2 mg/kg和22.4~82.1 mg/kg,未塌陷区域为83.5~162 mg/kg和38.7~86.5mg/kg;（2）两种开采方式地表塌陷坡地土壤NH＋4—N和AP含量与未塌陷区域相比,均显著降低（p〈0.05）,NH＋4—N含量自坡顶至坡底逐渐增加。随时间推移,NH＋4—N和AP含量未显著降低,AP含量反而有增加迹象;（3）强降雨时NH＋4—N和AP的流失量是弱降雨的3~5倍,颗粒态NH＋4—N和AP流失量占总流失量的60%以上。坡度越大,NH＋4—N和AP的流失量越多,流失量突变的坡度为5°~10°之间。[结论]砂姜黑土区采煤塌陷坡耕地土壤氮磷流失显著增加,颗粒态NH＋4—N和AP为径流流失的主要形式。

[Objective]Temporal-spatial distribution of ammonium nitrogen（NH＋4—N）and available phosphorus（AP）in surface soil were studied from mining subsidence slope farmland in lime concretion black soil areas.Meanwhile,the loss characteristics of nitrogen and phosphorus from surface runoff was analyzed with respect to rain intensity and slope degree.[Methods]Two surface-subsided slope farmlands resulted from coal mining were selected to sample and measure soil NH＋4—N and AP concentration from lime concretion black soil areas in Huaibei Plain.By simulated rainfall experiments in laboratory,soluble and particulate NH＋4—N and AP concentration from surface runoff were determined under two different rain intensity and three slope conditions.[Results]（1）NH＋4—N and AP concentration in surface soil of slope land for backfill mining were 16.5~72.0mg/kg and 26.0~63.5mg/kg,respectively;and the corresponding values without backfill filling were 9.08~67.2mg/kg and 22.4~82.1mg/kg,respectively.While,NH＋4—N and AP content were 83.5~162mg/kg and 38.7~86.5mg/kg from surface soil in non subsidence areas,respectively;（2）Soil NH＋4—N and AP contents of the two mining-caused subsidence farmlands significantly decreased in contrast to that of the farmland without subsidence（p0.05）.The content of NH＋4—N was found gradually increasing from the top to the bottom of the slope there.After subsidence happened,soil NH＋4—N and AP concentration of the subsidence slope land did not significantly decrease as time went by,and AP content had an increasing instead;（3）NH＋4—N and AP loss under heavy rainfall were 3~5times of that of weakprecipitation,in which,particulate NH＋4—N and AP loss accounted for more than 60% of the total loss.The greater the slope is,the more NH＋4—N and AP would be lost.The inflection gradient of increased loss is 5°~10°.[Conclusion]Mining substance can significantly result in the loss of soil nitrogen and phosphorus on slope lands in lime concretion black soil areas,and particulate NH＋4—N and AP are the main ways of their loss with surface runoff in the region.