典型山地农业区浅层地下水硝酸盐来源及转化过程解析

范祖金; 魏兴; 周育琳; 陈蒙恩; 申纪伟; 李佳文

doi:10.13198/j.issn.1001-6929.2023.07.19

典型山地农业区浅层地下水硝酸盐来源及转化过程解析

doi: 10.13198/j.issn.1001-6929.2023.07.19

重庆三峡学院土木工程学院，重庆　404100

基金项目: 重庆市自然科学基金项目(No.CSTB2022NSCQ-MSX1392)；重庆市教委科学技术研究项目(No.KJQN202201224, KJQN202201210)

详细信息

作者简介:
范祖金（1996-），男，四川广元人，2960365531@qq.com

通讯作者:
魏兴(1993-)，男，安徽阜阳人，讲师，博士，主要从事地下水循环演化及同位素水文学研究，weixing@sanxiau.edu.cn

中图分类号: X52
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- 被引次数: 0
出版历程
- 收稿日期: 2023-05-17
- 修回日期: 2023-06-29
- 网络出版日期: 2023-07-14

Analysis of Nitrate Sources and Transformation Processes in Shallow Groundwater in Typical Mountainous Agricultural Area

College of Civil Engineering, Chongqing Three Gorges University, Chongqing 404100, China

Funds: Chongqing Natural Science Foundation of China (No.CSTB2022NSCQ-MSX1392); Chongqing Municipal Education Commission Science and Technology Research of China (No.KJQN202201224, KJQN202201210)

摘要

摘要: 为准确识别重庆市典型山地农业区(万州区)浅层地下水硝酸盐来源及转化过程，利用水化学方法和环境同位素技术(δ¹⁸O-H₂O、δ¹⁵N-NO₃⁻和δ¹⁸O-NO₃⁻)，对不同土地利用类型的浅层地下水进行分析，并结合贝叶斯同位素混合模型(MixSAIR模型)对各硝酸盐源贡献率进行计算. 结果表明：①研究区浅层地下水属于弱碱性淡水，阴阳离子分别以HCO₃⁻和Ca²⁺为主，水化学类型以HCO₃-Ca型为主；硝酸盐是浅层地下水无机氮的主要赋存形式，其中耕地浅层地下水硝酸盐含量普遍高于建设用地和林地，且水样G20、G31和G40硝酸盐含量超过世界卫生组织规定的饮用水标准限值. ②研究区浅层地下水环境同位素值关系显示，硝酸盐转化过程以硝化作用为主，基本不存在反硝化作用. ③MixSAIR模型计算结果表明，耕地浅层地下水硝酸盐主要来源于化学肥料(占36.3%)、污水粪肥(占35.4%)和土壤有机氮(占24.7%)；林地浅层地下水硝酸盐主要来源于大气降水(占35.3%)、化学肥料(占31.3%)和土壤有机氮(占22.1%)；建设用地浅层地下水硝酸盐主要来源于化学肥料(占46.0%)和污水粪肥(占32.2%). 研究显示，研究区浅层地下水硝酸盐来源整体上以化学肥料和污水粪肥为主，硝酸盐污染防治应控制农业种植过程中化学肥料的过量施用，同时加大农村和城镇污水粪肥排放管理力度.
- 山地农业区 /
- 浅层地下水 /
- 硝酸盐来源 /
- 转化过程 /
- 贝叶斯同位素混合模型(MixSAIR模型)
Abstract: This study aimed to characterize the sources and transformation processes of nitrate in shallow groundwater in a typical mountainous agricultural area of Wanzhou District, Chongqing, China. The isotopes (δ¹⁸O-H₂O, δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻) and hydrochemistry of shallow groundwater in different land use types were analyzed, and the Bayesian isotope mixing model (MixSAIR model) was used to calculate the contribution of each nitrate source. The results indicated that: (1) Shallow groundwater in the study area was weakly alkaline fresh water with HCO₃-Ca hydrochemical type, and HCO₃⁻ and Ca²⁺ were the main anions and cations, respectively. Nitrogen in shallow groundwater was mainly in the form of nitrate, and nitrate content of shallow groundwater under cultivated land was generally higher than that under construction land and forest land. The nitrate content of water samples G20, G31 and G40 exceeded the drinking water standard limit stipulated by the World Health Organization. (2) Isotopic analysis of the shallow groundwater showed that nitrification dominated the nitrate conversion process, with denitrification mostly absent. (3) The MixSAIR model indicated that nitrate in shallow groundwater under cultivated land mainly originated from chemical fertilizer (occupy 36.3%), sewage manure (occupy 35.4%), and soil organic nitrogen (occupy 24.7%). The nitrate in shallow groundwater under forested land mainly originated from atmospheric precipitation (occupy 35.3%), chemical fertilization (occupy 31.3%), and soil organic nitrogen (occupy 22.1%). The nitrate in shallow groundwater under construction land mainly originated from chemical fertilizer (occupy 46.0%) and sewage manure (occupy 32.2%). The results of this study showed that the main sources of shallow groundwater nitrate in the study area include chemical fertilization and sewage manure. Groundwater nitrate pollution in the study area can be ameliorated by regulating the agricultural application of chemical fertilizers and more effective management of sewage manure discharge in rural and urban areas.
- mountain agricultural area /
- shallow groundwater /
- nitrate sources /
- transformation processes /
- MixSAIR model

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图 1 研究区土地利用类型及浅层地下水采样点分布示意

Figure 1. Distribution of land use types and shallow groundwater sampling sites in the study area

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图 2 研究区浅层地下水Piper图

Figure 2. Piper diagram demonstrating the hydrochemistry of shallow groundwater in the study area

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图 3 研究区浅层地下水水化学类型空间分布

Figure 3. Spatial distribution of hydrochemical types of shallow groundwater in the study area

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图 4 研究区浅层地下水硝酸盐及氮氧同位素空间分布

Figure 4. Spatial distribution of nitrate and δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ of shallow groundwater in the study area

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图 5 研究区浅层地下水[NO₃⁻]/[Cl⁻]值与[Cl⁻]关系和硝酸盐氮氧同位素值分布

Figure 5. The relationship between [NO₃⁻]/[Cl⁻] and [Cl⁻] and the distribution of nitrate nitrogen and oxygen isotopes in shallow groundwater of the study area

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图 6 研究区浅层地下水δ¹⁵N-NO₃⁻与ln[NO₃⁻-N]、δ¹⁸O-NO₃⁻与ln[NO₃⁻-N]、δ¹⁵N-NO₃⁻与δ¹⁸O-NO₃⁻的关系

Figure 6. The relationships between δ¹⁵N-NO₃⁻ and ln[NO₃⁻-N], δ¹⁸O-NO₃⁻ and ln[NO₃⁻-N], and δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ of shallow groundwater of the study area

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图 7 研究区浅层地下水各硝酸盐源贡献率

Figure 7. The contributions of difference sources to shallow groundwater nitrate in the study area

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表 1 研究区浅层地下水化学参数统计

Table 1. Statistical summary of chemical parameters of shallow groundwater in the study area

采样区	项目	pH	TDS浓度/ (mg/L)	ORP/ mV	离子浓度/(mg/L)
采样区	项目	pH	TDS浓度/ (mg/L)	ORP/ mV	K⁺	Na⁺	Ca²⁺	Mg²⁺	HCO₃⁻	Cl⁻	SO₄^2-	NO₃⁻	NO₂⁻	NH₄⁺
耕地 (n=35)	最小值	5.94	40.49	137.00	0.39	1.34	4.54	1.56	11.98	2.44	5.28	0.39	—	—
	最大值	8.46	551.60	248.00	5.08	34.83	101.50	23.17	353.30	35.13	46.15	33.03	0.60	0.23
	平均值	7.47	325.47	164.00	1.70	12.55	56.43	10.03	185.57	11.87	22.61	4.29	0.04	0.02
	标准差	0.66	141.82	27.54	1.05	7.85	27.67	5.47	103.26	8.08	11.35	5.93	0.11	0.05
林地 (n=12)	最小值	7.39	39.39	117.00	0.22	0.08	4.00	0.12	16.77	2.16	2.38	0.37	—	—
	最大值	9.62	450.80	218.00	3.70	15.65	104.80	21.01	294.00	10.31	88.88	6.57	0.02	0.05
	平均值	8.22	217.60	169.00	1.29	4.58	40.85	5.57	129.69	3.91	20.82	1.34	0.00	0.01
	标准差	0.56	176.00	33.10	1.01	4.78	37.00	6.21	115.21	2.54	29.21	1.83	0.01	0.02
建设用地 (n=9)	最小值	7.10	71.96	145.00	0.35	2.38	8.24	3.19	41.92	2.81	7.72	0.38	—	—
	最大值	8.71	465.20	218.00	1.78	19.02	102.90	15.09	308.40	11.63	38.91	3.82	0.90	0.17
	平均值	7.79	287.00	179.00	1.03	9.05	52.00	7.60	174.00	6.47	23.42	1.41	0.10	0.02
	标准差	0.56	148.04	28.84	0.44	5.42	33.87	4.17	97.76	3.09	11.36	1.11	0.30	0.06
注：n为水样数；NO₃⁻、NO₂⁻和NH₄⁺浓度均以N计；“—”表示低于仪器检出限.

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表 2 不同硝酸盐源初始δ¹⁵N-NO₃⁻、δ¹⁸O-NO₃⁻的平均值和标准差

Table 2. Mean and standard deviation of initial δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ from different sources of nitrate

硝酸盐源	δ¹⁵N-NO₃⁻/‰		δ¹⁸O-NO₃⁻/‰		数据来源
硝酸盐源	平均值	标准差	平均值	标准差	数据来源
土壤有机氮	3.3	2.4	4.1	0.3	文献[33,43]
污水粪肥	16.3	5.7	7.0	2.7	文献[43]
化学肥料	0.9	2.0	−2.0	0.5	文献[33,43]
大气降水	3.2	2.4	44.0	9.1	文献[43]

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