土壤氮在植物生长、土壤理化性质和微生物活动中扮演着重要的角色.为了识别盐渍化地区非饱和带氮的迁移过程，以河套灌区典型盐渍化耕地为例，通过非饱和带监测和水化学统计分析，探究了土壤剖面中氮素分布的差异性及主要影响因素.结果表明，研究区0～100 cm土层深度土壤氮含量处于较低水平，NO 3 ‐N、NH 4 ‐N和NO 2 ‐N含量平均值分别为4.88、1.63和0.04 mg/kg.土壤氮的空间分布与土层深度和理化性质有关，随深度增大，NO 3 ‐N含量呈逐渐增加的趋势，高值区主要分布于40～80 cm深度的土层，NH 4 ‐N含量多集中在60～100 cm深度的土层.土壤NO 3 ‐N含量主要与土壤p H、含水率和水溶性盐分含量(TDS、Cl - 、SO 4 2- 、Na + )有关，而NH 4 ‐N含量主要受含水率、黏粒和TOC含量的影响.NO 3 ‐N和NH 4 ‐N在土壤中的积累与水盐运移、土壤矿物的静电吸附和微生物的控制有关，这在很大程度上受土壤粒度组成、p H、有机质含量和竞争性阴、阳离子含量的影响.

Improving saline-alkali soil by cutting off the soil capillary zone and inhibiting the migration of soil water and salt is a new idea. An experimental site was established to conduct some physical remediamation experiments in the Western Hetao Irrigation Area (HIA), Northern China. The study aims to explore the improvement effect and mechanism of different physical remediation technologies based on gravel barriers, ditches, and shallow drainage wells. Three different treatments (gravel barrier (T1), gravel ditches combined with shallow drainage wells (T2), and shallow drainage wells (T3)) were employed along with a blank control (CK). Soil moisture, percentage of exchangeable sodium (ESP), available alkali hydrolyzable nitrogen (N) and phosphorus (P), particle size, and total organic carbon (TOC) were determined in the 0–80 cm soil profile. The changes of soil EC, soluble ion content, pH, and ESP monitored for different treatments over time showed salt and alkali reduction was achieved in order of effectiveness as follows: T1 > T2 > T3. At the end of the 3-month growth period, compared with CK, the average content of soli soluble salt at different depths in T1, T2, and T3 treatments decreased by 52.69%, 19.99%, and 18.08%, respectively. The average dry weight of harvested grass in the CK group was 12.8 g, while that of T1, T2, and T3 was 21.6 g, 20.2 g, and 18.3 g. The application of a gravel barrier or gravel ditches and drainage wells can significantly decrease soil salinity and alkalinity, but the drainage wells alone were limited. The gravel layer serves as a capillary barrier layer, which effectively inhibits the salt from rising to the soil surface. The gravel layer intercepts the crystals precipitated by evaporation and helps to prevent the soil salt expansion caused by crystal precipitation. In the soil layers loosened by the construction of the treatment plots, large soil aggregates are broken and release more clay particles that can adsorb macromolecular organic matter and form relatively stable organic-inorganic complexes. This process can contribute to the accumulation of TOC and improve the soil structure, which is conducive to the infiltration of soil salt with irrigation water. A comprehensive comparison of the cost-effectiveness and joint application of gravel ditches and drainage wells should be considered to improve the potential for the large-scale application of these approaches to improve saline-alkali soils.

以典型纳污坑塘(污水库)周边地下水水质监测数据为基础,在对区内地下水污染源进行分析的基础上,采用水环境健康风险评估模型,对区内地下水污染健康风险进行了系统评价研究.污染来源识别结果表明:纳污坑塘周边第Ⅰ、第Ⅱ含水层地下水污染严重,其污染源主要为坑塘内堆放的工业污水以及工业废渣.污染健康风险评估结果表明:8号坑附近第Ⅰ含水层中砷浓度以及北库南侧第Ⅱ含水层中1,2-二氯乙烷总致癌风险分别为10-2、10-3数量级,远超可接受风险水平10-6.不同含水层中污染物平均致癌风险大小关系为,第Ⅰ含水层:砷>1,2-二氯乙烷;第Ⅱ含水层:1,2-二氯乙烷>砷>1,1,2-三氯乙烷>四氯化碳.1,2-二氯乙烷等挥发性有机污染物4种潜在暴露途径的平均致癌风险大小关系表现为:饮用地下水>皮肤接触地下水>经室外吸入空气中气态污染物>经室内吸入空气气态污染物.相对于敏感用地,非敏感用地污染物的总致癌风险以及危害商较低.