【作者】 孟庆俊；

【导师】 冯启言；

【作者基本信息】 中国矿业大学 ， 环境科学， 2010， 博士

【摘要】 黄淮海平原煤炭开采造成大面积土地塌陷,在地下水位高的矿区,塌陷造成地表大面积积水,形成采煤塌陷湿地。淮南矿区位于淮河中游两岸,其主体地貌类型是淮河冲积平原,经过几十年的开采,淮南矿区已经形成采煤塌陷区面积超过67 km2,其中积水区面积约为14 km2。采煤塌陷造成矿区土地类型改变、水土流失、土壤退化等生态环境问题,其中土壤营养元素的流失是土壤退化的关键因素。本文以淮南矿区潘北煤矿作为研究区域,通过现场动态监测,研究了潘北矿区采煤塌陷地土壤中氮磷的时空分布特征,分析了采煤塌陷地水体中氮磷季节性变化规律;采用室内模拟实验,探讨了采煤塌陷地土壤淹水后土壤中氮磷元素的释放机理以及土壤对上覆水中氮磷的吸附特征;对潘北煤矿塌陷区的土壤侵蚀量和氮磷流失量进行了估算。主要成果如下:1)分别于2009年4月、7月和12月在潘北矿区采煤塌陷地共采集了72个土壤样品,测定了总氮、硝态氮、氨氮、总磷、可溶性总磷等指标,深入研究了采煤塌陷盆地土壤中氮、磷的时空分布规律,结果表明:土壤中总氮、总磷含量较高,空间变异性较大,平均含量分别为1329.31mg/kg和326.34mg/kg;从塌陷盆地边缘到积水区,氮含量呈明显下降趋势,而磷则下降幅度较小,在季节性积水区,溶出效应使土壤氮含量下降,而干湿交替使磷呈现累积现象;氮、磷含量在垂向随土壤深度的增加而逐渐下降,且丰水期下降幅度大于枯水期。2)采煤塌陷湿地水中氮磷具有明显的季节性变化规律,4月(总氮平均值1.72mg/L,总磷0.10mg/L)和12月(总氮2.09mg/L,总磷0.10 mg/L)水中氮磷含量较高,存在富营养化风险;7月份属丰水期,积水面积较大,稀释作用导致氮、磷不同形态浓度降低(总氮0.90mg/L,总磷0.09 mg/L)。3)通过塌陷地土壤淹水条件模拟实验,研究了总氮、总磷、硝酸盐氮、氨氮、可溶性总磷的释放强度、释放速率和累积释放量的变化规律,结果表明:○1 pH对土壤氮磷释放影响最大,碱性条件下氮磷释放能力最强,酸性条件下稍弱,中性条件下最小,这是因为中性条件下土壤颗粒物中磷相对比较稳定,不易释放到水中;在酸性条件下钙磷的溶解增加了磷的释放量,碱性条件下诱发铝铁结合态磷溶解而促进了可溶性磷的释放;氮释放主要受竞争吸附和有机氮的矿化作用影响,酸性条件下,H+的竞争吸附增大了氨氮的释放,而碱性条件下OH-的竞争吸附促进了土壤中硝态氮的释放;○2溶解氧水平对土壤中氮磷释放有一定影响,厌氧使反硝化作用、氨化作用和有机氮矿化作用加强,氮不同形态释放量超过好氧条件下的释放量;在厌氧状态下三价铁被还原为二价铁离子,铁结合态磷表面的Fe(OH)3保护层转化为溶解性较强的Fe(OH)2,使PO43-脱离土壤颗粒物进入水中;○3光照对底泥氮磷释放影响不明显。可见,水体酸碱度是控制土壤中氮、磷释放的关键因素。4)模拟研究了塌陷地土壤对氮、磷的吸附特征,确定了塌陷地土壤“源”、“汇”功能转换的临界条件,结果表明:当上覆水中磷浓度大于0.50mg/L时,采煤塌陷地土壤对磷的吸附等温线符合Langmuir模型,最大吸附量Qm为0.28mg/g,吸附平衡常数K=0.246,当磷浓度小于0.50mg/L时,其吸附等温线为交叉型,采煤塌陷地土壤对磷的吸附/解吸平衡浓度为0.27mg/L;土壤对氮的吸附过程可以用修正的Henry模型进行拟合,K=0.0157,土壤对氮的吸附/解吸平衡浓度为3.65mg/L。截止到2009年12月,潘北煤矿采煤塌陷地水中氨氮与可溶性总磷浓度分别为0.54mg/L和0.06mg/L,均小于其吸附/解吸平衡浓度,表明淹水后的土壤仍处在氮磷释放阶段。5)遥感影像解译结果表明,潘北煤矿东部采区2009年4月、7月和12月的采煤塌陷积水区面积分别为0.29km2、0.53km2、0.51km2。预计到2015年12月塌陷面积将达到7.25km2,其中积水区域面积约为1.8km2,最大下沉深度约4m。利用USLE方程预计了2015年潘北矿区采煤塌陷区土壤侵蚀量约为800.93t/a,总氮、总磷的流失量分别为251.87kg/km2·a和67.38kg/km2·a,比塌陷前增加了约58%,因此,采煤塌陷加速了土壤侵蚀与氮、磷流失。更多还原

【Abstract】 Aimed at addressing the spatio-temporal distribution of nitrogen and phosphorus in topsoil and water of Paibei coal mining subsidence land in Huainan, time-lapse monitoring was taken in this study. Moreover, simulation experiments were implemented to test the release mechanism and adsorption characteristics of nitrogen and phosphorus after soil submerge in this area. Based on the ArcInfo technique amount changes of soil erosion and losses of nitrogen and phosphorus in soil pre and post the formed of coal mining subsidence land were evaluated. The results are as follows:1) The content of nitrogen decreases significantly from the edge of subsidence basin to catchments. Phosphorus decreases slightly compared to nitrogen. Vertical distribution of nitrogen presents a consistent trend, which indicates that the contents of nitrogen gradually decrease with the depth. The contents decreases larger in wet season than in dry season2) Nitrogen and phosphorus have obvious seasonal variation in water body of Panbei coal mining subsidence wetlands. The high contents of Nitrogen and phosphorus arised the risk of water eutrophication in both April and December.The concentration of different species of nitrogen and phosphorus in July is low due to plentiful of precipitation in this season.3) Results of release experiment indicate that the pH of overlying water is the key factor controlling release of nitrogen and phosphorus from soil. The intensity of phosphorus release from soil is the highest when pH of the overlying water equals to 10, higher when pH equals to 4 and the lowest when pH equals to 7 separately. Nitrogen and phosphorus releases more in anaerobic condition than in aerobic condition. The effect of illumination on phosphorus release from soil is not obvious.4) Adsorption experiment of nitrogen and phosphorus on soil presents that when concentration of nitrogen and phosphorus is more than 0.5mg/L for phosphorus and 5.0mg/L for nitrogen, the adsorption isotherm of phosphorus fits Langmuir model with the maximum adsorption Qm of 0.28mg/g. And the adsorption isotherm of nitrogen fits Henry adsorption model. According to adsorption-desorption equilibrium of nitrogen and phosphorus in the submerge soil of Panbei coal mining subsidence land, nitrogen and phosphorus are still releasing from the submerge soil.5) According to the interpretation of remote sensing image, the catchments area of coal mining subsidence land in the east part of Panbei coal mine are respectively 0.29km2, 0.53km2 and 0.51km2 in April, July and December, 2009. Therefore, up to 2015, the maximum subsidence depth is 4 meter and subsidence area is about 7.25km2 of which including catchments of 1.8km2; and the amount of soil erosion around catchments within the scope of subsidence land will be 800.93t/a. Soil erosion modulus increases by 58% after subsidence compared to those before the subsidence. The losses of total nitrogen and phosphorus are 251.87 kg/km2 and 67.38 kg/km2 respectively.更多还原