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硝酸盐是地下水常量组分。近年来,硝酸盐污染成为全球最普遍、污染面积最大的地下水污染。农业化肥过量使用及城市、工矿企业污水无序排放是地下水硝酸盐污染的主要原因[1]。我国现为氮肥施用最多的国家,约占世界施用总量的30%[2]。在无合理农业管理措施情况下,作物对氮肥的利用率仅为30%—40%[3]。过量的氮肥最终以硝酸盐的形式在淋滤下进入水体。我国华北平原氮污染较为广泛,12.2%的地下水受到不同程度的“三氮”污染[4],且呈增加趋势。茹淑华等[5]通过对河北省11个地区连续7年的地下水硝酸盐含量监测,发现河北省地下水硝酸盐平均含量呈逐年明显增加的趋势,超标频率明显增加,由2006年的6.96%增加到了2012年的10.60%。武海英[6]通过对张家口地区8年地下水监测数据的分析,指出张家口地区地下水“三氮”污染总体情况不乐观,在所分析的监测井中有近一半“三氮”超标,坝上地区和市区“三氮”污染情况较坝下严重。硝酸盐可能通过地下水的饮用进入人体。高浓度的硝酸盐可导致高铁血红蛋白症,对婴幼儿的危害尤为显著;此外硝酸盐在人体中可能被还原为亚硝酸盐,与仲胺类作用形成致癌的亚硝胺类,严重危害人体健康[7-8]。预防、控制和治理地下水硝酸盐污染成为了重要环境问题。
安固里淖内陆河流域位于河北省西北部坝上环京津地区,半干旱气候,降雨稀少而蒸发强烈,地表水资源极为有限,地下水几乎是当地唯一的供水水源。区内农业、畜牧业活动范围广、强度大,地下水已受到硝酸盐的污染。同时,流域含水层多为岩浆岩,强非均质性,裂隙、孔洞发育,地表覆盖第四系土层大多较薄,导致硝酸盐更易进入地下水系统,且易扩散,而运移路径复杂,污染状况难以模拟。地下水对研究区生态系统、居民生产生活以及社会的稳定发展均有重要影响。而多年来对该区域的研究多集中于资源型缺水问题,硝酸盐的广泛分布和积累问题急需得到重视。
本文以水化学方法结合土地利用类型揭示流域内地下水硝酸盐污染分布特征及成因,为安固里淖内陆河流域的硝酸盐污染提供防治依据,提出指导当地生产生活的理论依据,为有限地下水资源的水质提供保障。
安固里淖内陆河流域地下水硝酸盐污染时空分布特征及成因分析
Temporal and spatial distribution characteristics and origin analysis of nitrate pollution in groundwater in Angulinao inland river basin
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摘要: 安固里淖内陆河流域为严重缺水区,多年来,此区域的地下水研究集中水资源量及其开发方向,含水层遭受的污染受到了忽视,其中硝酸盐污染是安固里淖内陆河流域最突出的水质问题。本研究采集流域雨季前和雨季后地下水样品共258组进行全分析检测,分析流域硝酸盐分布及成因。结果表明,流域补给区水化学类型以HCO3-Ca为主,阴离子类型沿流向向HCO3·SO4、HCO3·Cl、Cl·HCO3、Cl型过渡;部分地点硝酸盐超标严重,超标率达44.3%;降雨期结束后流域硝酸盐浓度升高,且污染羽沿地下水流向扩大呈条带状分布;流域地下水处于弱碱性氧化条件,适宜硝酸盐的积累。硝酸盐主要受土地利用类型影响,来源主要为农业化肥和人畜生活用水排放。Abstract: Angulinao inland river basin was a severe water shortage area, and the issues about the amount and use of groundwater resources in this area were paid much attention. However, the groundwater contamination including nitrate contamination has been neglected in this area. The present study investigated the distribution of groundwater nitrate and its factors in the Angulinao inland river basin, and 258 groundwater samples were collected for analysis. The results showed that HCO3-Ca was the main hydrochemical type in the recharge area of the basin, and the anionic type was evolved with HCO3·SO4, HCO3·Cl, Cl·HCO3, Cl type along the groundwater flow. Nitrate concentrations in 44.3% groundwater samples in this area exceeded the standard for groundwater quality in China. The concentration of groundwater nitrate in this area increased after the rainfall period, and the pollution plume expanded along the flow direction of groundwater. The groundwater in this area characterized by weak alkaline and oxidation conditions was in favor of the enrichment of nitrate. Groundwater nitrate in this area originated mainly from agricultural fertilizer and discharge of domestic water, and the distribution of nitrate in groundwater was mainly affected by land use type.
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Key words:
- Angulinao /
- inland river basin /
- groundwater /
- nitrate /
- distribution /
- origin
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表 1 研究区地下水、泉水及地表水水化学参数统计(mg·L−1)
Table 1. Statistics of chemical parameters of groundwater, spring and surface water in the study area(mg·L−1)
pH Na+ Ca2+ Mg2+ SO42− Cl− NO3− NO2− NH4+ TDS DO 地下水 最大值 8.59 1176.73 368.7 377.83 892.84 1367.56 786.45 11.53 6.00 4398.57 9.9 平均值 7.85 107.50 97.73 47.10 107.05 153.87 111.03 0.14 0.07 797.15 7.07 最小值 6.40 6.80 10.46 4.90 1.50 6.28 0.56 0 0 130.80 1.3 泉水 最大值 8.42 29.65 99.80 31.36 76.51 56.31 107.11 0.62 0.04 500.67 12.6 平均值 7.87 16.37 56.86 14.36 31.82 18.99 31.23 0.04 0 293.34 8.43 最小值 7.44 7.14 23.09 5.79 13.72 4.02 3.20 0 0 127.00 4.7 地表水 最大值 7.80 27.57 81.12 28.64 31.16 23.85 0.92 0.09 20.86 433.30 17.00 平均值 7.68 25.82 59.56 24.70 28.75 22.75 0.90 0.04 10.43 357.98 10.01 最小值 7.55 24.06 38.00 20.76 26.34 21.65 0.89 0 0 282.65 3.02 表 2 研究区地下水组分相关系数统计表
Table 2. Statistical table of correlation coefficient of groundwater components in the study area
井深
Well depth埋深
Groundwater depth第四系厚度
Quaternary thickness硝酸盐
NO3−氯化物
Cl−硫酸盐
SO42−溶解性总固体
TDS井深 1.000 埋深 0.468** 1.000 第四系厚度 0.465** 0.252** 1.000 硝酸盐 −0.259** −0.197* −0.170* 1.000 氯化物 −0.071 −0.068 −0.045 0.597** 1.000 硫酸盐 −0.180* −0.310** −0.129 0.514** 0.817** 1.000 溶解性总固体 −0.151 −0.173* −0.093 0.674** 0.953** 0.867** 1.000 注:**:在置信度(双测)为0.01时,相关性显著;*:在置信度(双测)为0.05时,相关性显著.
Note:**: 0.01 level(bilateral) significantly correlated; *: 0.05 level(bilateral) significantly correlated.表 3 不同含水层氧化还原条件与不同形态氮含量关系(mg·L−1)
Table 3. Relationship between redox conditions and nitrogen content in different aquifers
DO ${\rm{NO}}_3^{-} $ ${\rm{NO}}_2^{-} $ ${\rm{NH}}_4^{+} $ 花岗岩和凝灰岩裂隙水 6.11 82.07 0.10 0 玄武岩裂隙孔洞水 6.77 107.8. 0.11 0.01 第四系孔隙水 7.58 115.25 0.32 0.19 -
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