九龙江河口咸淡水混合过程中汞的额外增加与消除

张小丹; 孙鲁闽; 薛凯宁; 邹游; 弓振斌; 袁东星

doi:10.13198/j.issn.1001-6929.2022.11.17

九龙江河口咸淡水混合过程中汞的额外增加与消除

doi: 10.13198/j.issn.1001-6929.2022.11.17

张小丹^{1, 2,},
孙鲁闽^2, ,,
薛凯宁²,
邹游²,
弓振斌¹,
袁东星¹

1.
厦门大学环境与生态学院，滨海湿地生态系统教育部重点实验室，福建厦门　361102
2.
厦门大学嘉庚学院环境科学与工程学院，河口生态安全与环境健康福建省高校重点实验室，福建漳州　363105

基金项目: 国家自然科学基金项目(No.41406120)；福建省自然科学基金项目(No.2019J01035)

详细信息

作者简介:
张小丹（1998-），男，湖北武汉人，zzhangxiaodan@vip.qq.com

通讯作者:
孙鲁闽(1984-)，男，福建厦门人，教授，博士，硕导，主要从事环境监测技术研究，sunlumin@xmu.edu.cn

中图分类号: X52
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出版历程
- 收稿日期: 2022-08-25
- 修回日期: 2022-11-10

Addition and Removal of Mercury in Jiulong River Estuary during Mixing of Seawater and Freshwater

1.
Key Laboratory of the Coastal and Wetland Ecosystems, Ministry of Education, College of Environment and Ecology, Xiamen University, Xiamen 361102, China
2.
Key Laboratory of Estuarine Ecological Security and Environmental Health, Education Department of Fujian, School of Environmental Science and Technology, Tan Kah Kee College, Xiamen University, Zhangzhou 363105, China

Funds: National Natural Science Foundation of China (No.41406120); Natural Science Foundation of Fujian Province, China (No.2019J01035)

摘要

摘要: 河口是海陆界面能量和物质交换的重要场所，研究汞在河口的迁移特征及影响因素，对认识汞的生物地球化学行为具有重要意义. 本研究测定了九龙江河口区沉积物孔隙水的总汞(total mercury, THg)浓度与汞同位素特征，结合笔者所在课题组已发表的相关研究数据，比较不同季节、不同潮位、降水与否的表层水THg浓度、汞同位素组成与盐度之间的关系，探究影响表层水中汞额外增加/消除的因素及机制. 结果表明：①孔隙水THg浓度〔(38.28±28.80) ng/L，n=28〕显著高于表层水〔(8.53±6.85) ng/L，n=35〕(P<0.01)；孔隙水THg浓度受季节或径流量变化的影响不明显. 孔隙水δ²⁰²Hg平均值(−1.24‰±0.36‰，n=28)处于表层水(−0.32‰±0.38‰，n=29)和沉积物(−1.99‰±0.69‰，n=18)之间；Δ¹⁹⁹Hg平均值(−0.13‰±0.03‰，n=28)低于表层水(−0.04‰±0.10‰，n=29)和沉积物(−0.04‰±0.16‰，n=18)，表明汞在孔隙水与沉积物间的双向传递与吸附及非光致氧化过程有关. ②枯水期河口区表层水中的汞以额外消除为主，呈现汞“汇”特征；丰水期则呈现汞“源”特征. 当咸淡水在河道较浅处交汇时，表层水中汞的额外增加更大. 无论是增加或消除，表层水中汞的δ²⁰²Hg与Δ¹⁹⁹Hg值均升高. 汞在咸淡水交汇界面的迁移受径流量、潮位、河道特征及降水事件等多因素影响. ③枯水期中降水事件发生时表层水THg浓度和汞同位素组成随盐度的变化特征与非降水期不同，表明降水可影响表层水中汞的行为. 研究显示，汞在咸淡水交汇界面的迁移受径流量、潮位、河道特征及降水事件等多因素影响，河口是汞“源”也是汞“汇”.
- 九龙江口 /
- 盐度 /
- 总汞浓度 /
- 汞同位素 /
- 孔隙水
Abstract: Estuaries play an essential role in the exchange of energy and materials at the sea-land interface. Studying the migration characteristics of mercury (Hg) and related influencing factors is of great significance for understanding the biogeochemical cycling of Hg. This study assessed total Hg (THg) concentration and Hg isotope compositions in sediment porewater of the Jiulong River Estuary (JRE). Combined with data from relevant published studies published by author′s research group, the relationship between THg concentration, Hg isotopic composition, and surface water salinity in different seasons (wet and dry seasons), different tidal levels, and with or without precipitation events were compared to determine the factors and mechanisms affecting the addition/removal patterns of Hg in surface water. The results showed that: (1) The average porewater THg concentration ((38.28±28.80) ng/L, n=28) was significantly higher than that in surface water ((8.53±6.85) ng/L, n=35) (P<0.01); Porewater THg concentration was not significantly affected by seasons and runoff. On the other hand, the average δ²⁰²Hg value of porewater (−1.24‰±0.36‰, n=28) was between that of surface water (−0.32‰±0.38‰, n=29) and sediment (−1.99‰±0.69‰, n=18), while the average Δ¹⁹⁹Hg value (−0.13‰±0.03‰, n=28) of porewater was lower than that of surface water (−0.04‰±0.10‰, n=29) and sediment (−0.04‰±0.16‰, n=18), indicating that the bidirectional Hg transfer between porewater and sediment was related to the adsorption and abiotic dark oxidation processes. (2) Hg in the surface water of JRE was mainly removed during the dry season, acting as a Hg sink, while during the wet season, the river estuary was the source of Hg. In addition, significant increases in Hg addition in the surface water were observed when freshwater and seawater converged in the shallow channel. Regardless of the addition/removal pattern of Hg, the δ²⁰²Hg and Δ¹⁹⁹Hg values increased among almost all samples. The Hg migration at the converge interface of freshwater and seawater was affected by several factors, such as runoff, tide level, channel characteristics, and precipitation events. (3) The variation characteristics of THg concentration and Hg isotopic composition with salinity in surface water during the precipitation period were different from those in the non-precipitation period, indicating the effects of precipitation events on the Hg behavior in surface water during the dry season. It is concluded that Hg migration at the converge interface of freshwater and seawater was affected by several factors, such as runoff, tide level, channel characteristics, and precipitation events. In addition, the river estuary was both source and sink of Hg.
- Jiulong River Estuary /
- salinity /
- total mercury (THg) concentration /
- Hg isotopic composition /
- porewater

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图 1 研究区域、采样站点及沉积物(河道)采样深度示意

Figure 1. Study area, location of sampling sites, and depth of sediment sampling (channel)

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图 2 九龙江河口各航次表层水、孔隙水THg浓度及沉积物THg含量分布

注：表层水THg浓度与沉积物THg含量数据均源自笔者所在课题组前期研究结果^[32].

Figure 2. Distribution of THg concentrations in surface water, porewater, and sediment samples collected from Jiulong River Estuary (JRE)

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图 3 九龙江河口区表层水、孔隙水及沉积物的Δ¹⁹⁹Hg与δ²⁰²Hg关系

注：表层水与沉积物汞同位素δ²⁰²Hg、Δ¹⁹⁹Hg的数据均源自笔者所在课题组前期研究结果^[32]；方框代表沉积物或表层水样品坐标点的分布范围；阴影代表孔隙水样品坐标点分布范围.

Figure 3. Relationships between Δ¹⁹⁹Hg and δ²⁰²Hg in surface water, porewater, and sediment samples of JRE

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图 4 丰水期与枯水期表层水THg浓度与盐度的关系

Figure 4. Relationships between THg concentrations and salinity of surface water in the wet and dry seasons

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图 5 丰水期与枯水期表层水汞同位素组成与盐度的关系

Figure 5. Relationships between the distribution of Hg isotopic compositions and salinity of surface water in the wet and dry seasons

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图 6 丰水期表层水δ²⁰²Hg-Δ与THg-Δ、Δ¹⁹⁹Hg-Δ与δ²⁰²Hg-Δ以及Δ¹⁹⁹Hg-Δ与Δ²⁰¹Hg-Δ之间的相关关系

Figure 6. Correlations between δ²⁰²Hg-Δ and THg-Δ, Δ¹⁹⁹Hg-Δ and δ²⁰²Hg-Δ, Δ¹⁹⁹Hg-Δ and Δ²⁰¹Hg-Δ of surface water in the wet season

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表 1 九龙江河口区孔隙水THg浓度、汞同位素组成及表层水盐度

Table 1. THg concentrations and isotopic compositions of JRE porewater samples, and salinity of JRE surface water samples

航次	站点名称	THg浓度/(ng/L)	汞同位素组成			表层水盐度/‰
航次	站点名称	THg浓度/(ng/L)	δ²⁰²Hg/‰	Δ¹⁹⁹Hg/‰	Δ²⁰¹Hg/‰	表层水盐度/‰
17Lc(枯水期)	A3	—	—	—	—	1.5
	A4	34.66	−1.37	−0.14	−0.15	4.4
	A5	44.15	−1.35	−0.09	−0.14	7.0
	A6	—	—	—	—	10.0
	A7	—	—	—	—	14.2
	A8	33.28	−1.65	−0.15	−0.18	20.5
	A9	—	—	—	—	22.5
	A9-1	—	—	—	—	24.4
	JY1	36.95	−0.54	−0.08	−0.02	26.8
	JY2	—	—	—	—	29.3
18Hc1(丰水期)	A3	49.27	−1.41	−0.13	−0.17	1.6
	A4	55.86	−1.66	−0.15	−0.16	2.7
	A5	37.51	−1.50	−0.17	−0.21	3.2
	A6	28.44	−1.36	−0.19	−0.21	5.9
	A7	18.7	−1.50	−0.14	−0.16	10.5
	A8	17.91	−1.19	−0.14	−0.14	13.4
	A9	26.33	−1.31	−0.12	−0.15	18.9
	A9-1	15.1	−1.31	−0.20	−0.18	25.5
	JY1	—	—	—	—	—
	JY2	—	—	—	—	—
18Hc2(丰水期)	A3	49.48	−1.90	−0.14	−0.26	0.0
	A4	52.39	−0.90	−0.09	−0.13	0.1
	A5	112.20	−1.04	−0.10	−0.18	1.3
	A6	58.27	−1.22	−0.13	−0.13	3.9
	A7	67.06	−1.26	−0.13	−0.14	8.8
	A8	82.17	−1.07	−0.15	−0.15	12.6
	A9	—	—	—	—	15.2
	A9-1	—	—	—	—	24.5
	JY1	—	—	—	—	25.3
	JY2	—	—	—	—	—
18Lc(枯水期,强降雨)	A3	33.12	−1.51	−0.14	0.02	0.0
	A4	9.25	−1.25	−0.11	−0.01	0.1
	A5	29.38	−1.35	−0.14	0.00	0.1
	A6	9.70	−0.22	−0.08	0.04	0.2
	A7	9.96	−0.53	−0.06	0.07	8.2
	A8	69.32	−1.44	−0.12	0.03	13.6
	A9	1.09	−1.28	−0.16	−0.01	24.3
	A9-1	2.13	−1.14	−0.12	−0.01	25.1
	JY1	76.27	−1.45	−0.17	0.02	30.5
	JY2	11.81	−1.02	−0.16	0.05	28.5
注：—代表未检出.

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