Abstract:

Kuitun Reclamation Area of Xinjiang is a typical area with high As content. In order to explore the distribution characteristics of arsenic in the groundwater and cropland soil and the impact of groundwater irrigation on As enrichment in the soil, a total of 50 groundwater samples (2 surface water samples as controls) and 100 cropland soil samples (soil samples with a depth of 0-10 cm and 10-20 cm were taken from each sampling site) were collected from the lower reaches of Kuitun River. Mathematics statistics and GIS spatial interpolation incorporated with the trend analysis of standard deviation elliptic model were used to investigate the spatial distribution of As in the groundwater and soil and explore the impact of groundwater irrigation on soil As accumulation, which might provide theoretical support for the rational use of groundwater for agricultural irrigation in this area. The results showed that the As concentration in groundwater in the study area ranged from 0.76 to 410.00 μg·L^-1, with an average of 116.38 μg·L^-1. Up to 84% of groundwater samples were identified as high As groundwater. The average As mass fraction in the soil at the depth of 0-10cm and 10-20cm was 12.45 mg kg^-1 and 10.97 mg·kg^-1 respectively, with 56% and 42% of soil sample sites exceeding the background values of As in Xinjiang. The mass fraction of As in the soil at the depth of 0-10cm was higher than that at the depth of 10-20 cm. In the study area, the spatial distribution characteristics of As in groundwater and soil were generally similar. The As mass concentration in groundwater was higher in the central and southwestern than the others. In 0-10 cm soil layer, the high value area of As was mainly distributed in the west and mid-northeast, whereas in 10-20 cm soil layer the concentration of As mass fraction generally increased from east to west. There was a significant positive correlation between As mass concentration in groundwater and As mass fraction in soil. The As mass fraction in the soil under mixed irrigation was lower than that under well irrigation. In conclusion, there is a significant accumulation of As in cropland soil in the lower reaches of Kuitun River, which might be caused by longtime groundwater irrigation. Mixed irrigation is suggested when groundwater is used for agricultural irrigation in this area.

Key words: arsenic, groundwater, cropland soil, spatial distribution, Kuitun

摘要：

为探究典型高砷区新疆奎屯垦区地下水和农田土壤As的分布特征以及地下水灌溉对土壤As富集的影响，以新疆奎屯河下游为研究区域，地下水及其灌溉的农田土壤为研究对象，共采集50个地下水水样（以2个地表水水样为对照）和100个农田土样（各采样点分别在0—10 cm和10—20 cm取样）。采用数理统计法和GIS空间插值技术，结合标准差椭圆模型趋势性分析，研究该地区地下水和土壤As的空间分布特征，探讨地下水灌溉对土壤As累积的影响，以期为该地区合理利用地下水进行农业灌溉提供理论支撑。结果表明：研究区地下水As质量浓度范围为0.76—410.00 μg·L^-1，均值为116.38 μg·L^-1，有84%的地下水样品为高砷地下水；0—10、10—20 cm土层中As平均质量分数分别为12.45、10.97 mg·kg^-1，分别有56%、42%的土壤样点As质量分数超出新疆土壤As元素背景值，土壤As质量分数表现为0—10 cm > 10—20 cm；地下水和土壤中As在整体水平上具有相似的空间分布特征，中部及西南方向的地下水As质量浓度较高；0—10 cm土层中，As的高值区主要集中分布于西部及中偏东北方向；10—20 cm土层中，As的分布整体呈现出由东向西方向增加的趋势；地下水As质量浓度与土壤As质量分数呈显著正相关，混灌条件下土壤As质量分数小于井灌条件下土壤As质量分数。综上，奎屯河下游区域长期受地下水灌溉的影响，农田土壤As出现一定累积现象，建议该地区利用地下水进行农业灌溉时多采用混灌方式。

关键词: 砷, 地下水, 农田土壤, 空间分布, 奎屯