西江下游某滩涂农田土壤与江水中镉砷的分布特征

任杰; 刘晓文; 吴颖欣; 刘星; 李杰; 文展

doi:10.7524/j.issn.0254-6108.2020032901

西江下游某滩涂农田土壤与江水中镉砷的分布特征

1.
兰州交通大学环境与市政工程学院，兰州，730070
2.
生态环境部华南环境科学研究所，广州，510655

通讯作者: E-mail：wuyingxin@scies.org;

基金项目:
国家重点研发计划项目（2017YFD0801300）资助

Distribution characteristics of cadmium and arsenic in the tidal flat farmland soil and the river environment in the lower Xijiang River

1.
School of environmental and municipal engineering, LanZhou JiaoTong University, Lanzhou, 730070, China
2.
South China Institute of Environmental Sciences, Ministry of Ecology and Environment, Guangzhou, 510655, China

Corresponding author: WU Yingxin, wuyingxin@scies.org ;

Fund Project: the National Key Research and Development Program of China（2017YFD0801300）

摘要: 珠三角城市化、工业化过程增加了Cd、As的环境释放量，江水沉积物既是污染物的汇，又是沿江农田污染物输入的源，同时江水水体是污染物远距离迁移的主要载体。为防范沿江农田Cd、As的生态环境风险，需加大对Cd、As分布特征的研究。本文对西江下游F市某滩涂农田开展野外调查研究，采集了沿江水样、沉积物和滩涂农田土壤样品，探究了Cd、As在滩涂农田土壤和江水沉积物中的分布特征和相关关系。研究发现，江水水体中Cd总量普遍小于1 µg·L⁻¹，As总量（均值45.80 µg·L⁻¹）与农闲期（均值3.80 µg·L⁻¹）相比显著增大。滩涂农田土壤和沉积物中Cd含量均值呈现低潮滩农田土壤＞河流沉积物＞高潮滩农田土壤的趋势；As含量均值呈现河流沉积物＞低潮滩农田土壤＞高潮滩农田土壤的趋势。相关性分析结果表明，低潮滩农田土壤Cd各形态含量与总量之间存在显著相关性（P <0.05），滩涂农田土壤和江水沉积物中As的残渣态与总量呈现极显著相关性（P<0.01）；低潮滩农田土壤中As的个别形态与江水沉积物中As的个别形态之间存在着显著相关性（P<0.05）。研究结果表明，相较高潮滩农田土壤与江水沉积物，低潮滩农田土壤Cd形态分布受到规模性的外部输入影响相对较大。滩涂农田土壤和江水沉积物中As主要为残渣态，江水沉积物和低潮滩农田土壤之间存在着明显的As交换，滩涂农田土壤中As受水力冲刷，发生横向迁移。江水水体中Cd受外源污染程度较小，江水水体中As可能来源于农田污染物迁移、农田排水和江水沉积物As释放。本文通过对西江下游滩涂农田Cd、As的存在形态与迁移规律的研究，以期为珠三角滩涂农田安全生产和Cd、As的生态风险防控提供数据支撑。
- 沉积物 /
- 低潮滩 /
- 高潮滩 /
- 江水 /
- Cd /
- As
Abstract: The urbanization and industrialization in the Pearl River Delta have increased the environmental release risk of Cd and As in this area. The river sediment is not only contaminant accumulations, but also the source for the contaminant in the farmland soil along the river. And river water body is the main carrier of pollutant long-distance transport. In order to prevent the ecological and environmental risks of Cd and As in the farmland soil along the river, it was necessary to study the distribution characteristics of Cd and As. A field investigation was conducted on a tidal flat farmland in the F city located in the lower reaches of the Xijiang River. Water, sediment and farmland soil samples along the river were collected. The distribution characteristics and correlation of Cd and As in the tidal flat farmland soil and the river sediment were explored. It was found that the total content of Cd in the river water was generally less than 1 µg·L⁻¹, while the total content of As (the mean content was 45.80 µg·L⁻¹) was significantly increased compared with that (the mean content was 3.80 µg·L⁻¹) in the farming slack period. The mean contents of Cd in the tidal-flat farmland soil and the river sediment showed a trend of low-tide flat farmland soil> river sediment> high-tide flat farmland soil, while the mean contents of As showed the trend of river sediment> low-tide flat farmland soil> high-tide flat farmland soil. Correlation analyses found that there was a significant correlation between the Cd morphological content and the total content of the low-tide flat farmland soil (P<0.05), and the residue form and total content of As in the tidal flat farmland soil and the river sediment were extremely significant (P<0.01). There was a significant correlation between individual forms and individual forms of As in the river sediment (P<0.05). Compared with the high-tidal flat farmland soil and the river sediment, the research results showed that Cd morphological distribution in the low-tidal flat farmland soil was relatively affected by the large-scale external input. As was mainly residue form in the tidal flat farmland soil and the river sediment. There was an obvious exchange of As between the river sediment and the low-tidal flat farmland soil. As in the tidal flat farmland soil moved laterally by the hydraulic scour. Cd in the river water was less polluted by external sources. As in the river water might come from the migration of farmland pollutants, farmland drainage and the release of As from the river sediment. In this paper, through the research on the chemical species and migration of Cd and As in the tidal flat farmlands soil in the lower reaches of the Xijiang River, we hope to provide data support for the safe production of the tidal flat farmland and the ecological risk control of Cd and As in the Pearl River Delta.
- sediment /
- low-tidal flat /
- high-tidal flat /
- river /
- Cd /
- As

图 1 采样点布置及周边环境示意图

Figure 1. The layout of sampling site and the surrounding environment

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图 2 江水沉积物、低潮滩农田土壤和高潮滩农田土壤 Cd、As含量均值

Figure 2. Average contents of Cd and As in SED, LTF and HTF

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图 3 Cd、As的MDFs和生物有效性特征

Figure 3. MDFs and bioavailability character of Cd and As

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图 4 8月研究区江水水体不同位点Cd、As含量

Figure 4. Contents of Cd and As at different sites of river water in the study area in August

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图 5 低潮滩农田土壤中Cd、As迁移的潜在路径和灌溉进水、雨水径流冲刷示意图

Figure 5. Potential migration pathways of Cd and As in the LTF and schematic diagram of irrigation inflow and rainwater runoff scouring

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表 1 土壤中重金属形态的Tessier五步连续提取法

Table 1. Tessier five-step continuous extraction method for heavy metal forms in the soil

步骤 Steps	形态 Forms	浸提剂 Leaching agent	操作条件 Operating conditions
Ⅰ	可交换态EX	8 mL 1.0 mol·L⁻¹ MgCl₂（pH=7.0）	25 ℃ 振荡1 h
Ⅱ	碳酸盐结合态CAB	8 mL 1.0 mol·L⁻¹ NaAc（pH=5.0）	（25±1 ）℃ 振荡8 h
Ⅲ	铁锰氧化物结合态FMO	20 mL 0.04 mol·L⁻¹ NH₂OH·HC1（20% HAc溶液）	（96±3 ）℃ 间歇振荡4 h
Ⅵ	有机物结合态OM	a.3 mL 0.02 mol·L⁻¹ HNO₃+5 mL 30% H₂O₂（pH=2） b.3 mL 30% H₂O₂（pH=2） c.5 mL 3.2 mol·L⁻¹ NH₄Ac（20% HNO₃溶液）	（85±2） ℃ 偶尔振荡2 h （85±2） ℃ 间歇振荡3 h 室温振荡30 min
Ⅴ	残渣态RES	HNO₃-HF-HClO₄	土壤消化法
衔接	—	8 mL超纯水洗涤	—

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表 2 低潮滩农田土壤、高潮滩农田土壤和江水沉积物中As、Cd含量比值

Table 2. Ratios of As to Cd contents of LTF, HTF and SED

As/Cd	TC	EX	CAB	FMO	OM	RES
SED	21.76±4.57	0.12±0.06	0.46±0.32	22.83±22.26	18.83±4.27	68.92±61.07
LTF	18.32±9.22	0.13±0.14	0.81±0.55	8.25±4.03	21.39±10.62	58.65±28.02
HTF	49.97±21.89	0.49±0.44	0.97±0.51	37.44±12.00	44.43±18.13	178.57±216.45

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表 3 江水沉积物、低潮滩农田土壤和高潮滩农田土壤中Cd、As形态含量与其全量的相关性分析

Table 3. Cd and As correlation analysis of TC and form contents of SED, LTF and HTF

相关性 Correlation		EX	CAB	FMO	OM	RES	EX+CAB	FMO+OM
Cd	SED	0.538	0.309	0.426	0.502	0.129	0.490	0.151
	LFT	0.942**	0.638*	0.864**	0.918**	0.814**	0.954**	0.845**
	HFT	0.318	0.210	0.749	−0.074	0.445	0.462	0.621
As	SED	0.477	−0.548	0.813*	0.103	0.997**	−0.137	0.816*
	LFT	0.316	−0.069	0.507	0.125	0.931**	0.030	0.507
	HFT	0.354	0.812*	0.565	-0.004	0.996**	0.659	0.558
表示P＜0.05，相关性系数达到显著水平；*P＜0.01，相关性系数达到显著水平。SED是江水沉积物，LTF是低潮滩农田土壤，HTF是高潮滩农田土壤.

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表 4 江水沉积物和江水水体中Cd、As形态间的相关矩阵

Table 4. Correlation matrix between Cd and As forms in SED and RW

元素Element		TC	EX	CAB	FMO	OM	RES	EX+CAB	FMO+OM
Cd	TC	−0.19	−0.15	−0.23	−0.06	−0.06	0.03	−0.18	−0.06
Cd	SC	−0.03	−0.05	0.03	0.14	−0.10	−0.05	-0.03	0.13
As	TC	0.58	0.26	0.08	0.50	0.04	0.58	0.23	0.51
As	SC	0.42	0.17	0.36	0.42	0.36	0.41	0.39	0.44

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表 5 低潮滩农田土壤和江水水体中Cd、As形态间的相关矩阵

Table 5. Correlation matrix between Cd and As forms in LTF and RW

元素Element		TC	EX	CAB	FMO	OM	RES	EX+CAB	FMO+OM
Cd	TC	0.28	0.25	0.39	0.47	0.38	−0.11	0.31	0.46
Cd	SC	0.07	0.00	0.21	0.28	0.19	−0.25	0.06	0.27
As	TC	0.36	−0.18	0.53	0.12	0.86*	0.26	0.42	0.36
As	SC	0.12	−0.42	−0.05	0.05	0.53	0.06	−0.14	0.20

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表 6 低潮滩农田土壤与江水沉积物中Cd、As形态间的相关矩阵

Table 6. Correlation matrix between Cd and As forms in LTF and SED

元素Element		TC	EX	CAB	FMO	OM	RES	EX+CAB	FMO+OM
Cd	TC	0.07	0.05	−0.09	−0.01	−0.04	0.04	0.01	−0.02
	EX	−0.11	−0.11	−0.12	−0.27	−0.13	0.13	−0.11	−0.26
	CAB	−0.23	−0.41	−0.57	−0.16	−0.58	0.27	−0.47	−0.20
	FMO	0.20	0.19	0.04	0.01	0.20	0.02	0.15	0.02
	OM	0.09	0.12	−0.05	0.10	0.01	−0.04	0.08	0.10
	RES	0.19	0.23	0.01	0.32	0.00	−0.14	0.17	0.30
	EX+CAB	−0.15	−0.20	−0.25	−0.26	−0.27	0.18	−0.22	−0.26
	FMO+OM	0.20	0.18	0.03	0.01	0.18	0.01	0.14	0.03
As	TC	−0.03	0.73	0.61	−0.04	−0.85*	−0.02	0.83*	−0.09
	EX	−0.34	0.44	0.16	−0.34	−0.49	−0.32	0.34	−0.37
	CAB	0.67	0.50	−0.55	0.58	−0.11	0.66	−0.16	0.57
	FMO	−0.17	0.86*	0.39	0.13	−0.62	−0.20	0.73	0.09
	OM	0.83*	0.13	−0.16	0.40	0.30	0.86*	−0.06	0.42
	RES	−0.07	0.49	0.58	−0.15	−0.77	−0.05	0.68	−0.19
	EX+CAB	0.51	0.54	−0.45	0.43	−0.21	0.51	−0.06	0.42
	FMO+OM	0.07	0.88*	0.34	0.24	−0.52	0.05	0.70	0.21

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随着城市化、工业化发展，农用地被其他类型用地挤占的状况愈发严重，沿海省市等经济发达地区的人均耕地面积严重不足 ^[1]。珠三角地区作为我国经济最发达的地区之一，人均耕地面积呈现不断缩减的态势 ^[1]。西江下游段流经珠三角地区，流域内河网密布，滩涂面积相对较大，滩涂农田开发已初具规模。有学者指出滩涂农田重金属污染受人为活动影响较大^[2]，镉（Cd）、砷（As）复合污染是珠三角农田典型的污染形式之一^[3]，珠三角滩涂围垦农田土壤污染以Cd为主^[1]，西江沿岸属于高As背景区域^[4]且As对人体健康的危害较大^[5]，土壤Cd、As污染使西江下游滩涂农田的生态风险不断攀升。滩涂在地貌学上称之为“潮间带”，受潮汐作用影响，低潮滩农田土壤（low-tidal flat soil，LTF）会经常被水淹没，相对堤内农田、中潮滩和高潮滩农田土壤（high-tidal flat soil，HTF）而言，低潮滩农田土壤受江河水潮汐作用的影响更大，在暴雨径流、高频度灌溉作业和江水潮汐作用下，滩涂农田连续种植可能存在较高的Cd、As生态风险。

近年来，国内外学者在滩涂农田重金属污染方面进行了大量研究工作，主要集中于原生滩涂、垦区土壤及其作物中重金属的含量和分布等^{[1, 6-9]}。目前，珠三角地区滩涂农田Cd、As迁移影响因素的研究不多。本文以西江下游某连续从事农业生产的低潮滩农田作为研究区域，以高潮滩农田土壤作为对照，研究低潮滩农田土壤与江水环境（river environment，RE）之间的相关性，并考虑研究区Cd、As分布受到暴雨径流、江水潮汐作用和高频度灌溉作业等迁移驱动力的影响，研究低潮滩农田土壤、高潮滩农田土壤和江水沉积物（river sediment，SED）中Cd、As含量的分布特征，具体而言，初步探究滩涂农田土壤Cd、As在横向上的迁移规律与污染形成机制，江水水体（river water，RW）、江水沉积物对滩涂农田土壤Cd、As分布的影响。

3. 结论（Conclusions）

本文对西江下游某滩涂农田土壤与西江Cd、As的分布特征研究，可获得以下结论：

（1）当地滩涂农田土壤和江水沉积物中Cd的生态风险高于As，低潮滩农田土壤中Cd、As活性处于极高水平。低潮滩农田土壤中Cd存在规模性的外源输入，以非残渣态为主，生物活性极高，迁移能力很强，江水沉积物和高潮滩农田土壤中Cd受局部影响较大。滩涂农田土壤和江水沉积物中As主要以RES存在，其中江水沉积物中As的全量和RES最大，滩涂农田土壤中As呈现向低位点迁移的趋势，降雨径流等是可能性较大的迁移方式。

（2）江水水体中Cd受外源污染较小，As的全量较农闲期显著增大，可能受农田污染物迁移等影响。滩涂农田土壤中As呈现从高位点向低位点迁移的现象，可能借助水动力主要以溶解形态/非残渣态发生横向迁移。江水沉积物和低潮滩农田土壤之间存在着明显的As交换，江水泛滥/农灌是可能性较大的交换途径。

（3）灌溉进水可适当加强净化力度，优化中间生产构筑物的结构，增加截留效果和减少外源降雨径流等的污染。优化潮滩农田排水系统，完善农田排水（包括降雨径流）的过程构筑物和末端处置。

参考文献 (15)

西江下游某滩涂农田土壤与江水中镉砷的分布特征

通讯作者: E-mail：wuyingxin@scies.org;

Distribution characteristics of cadmium and arsenic in the tidal flat farmland soil and the river environment in the lower Xijiang River

Corresponding author: WU Yingxin, wuyingxin@scies.org ;

计量

西江下游某滩涂农田土壤与江水中镉砷的分布特征

通讯作者: E-mail：wuyingxin@scies.org;

English Abstract

Distribution characteristics of cadmium and arsenic in the tidal flat farmland soil and the river environment in the lower Xijiang River

Corresponding author: WU Yingxin, wuyingxin@scies.org ;

全文HTML

1.1. 研究区域概况

1.2. 污染来源

1.3. 采样及样品前处理

1.4. 分析测试

1.5. 质量保证

1.6. 数据处理

2.1. 沿江农田土壤和底泥样品中Cd、As分布特征

2.1.1. pH值

2.1.2. Cd、As含量分布

2.1.3. 沿江农田土壤和底泥样品Cd、As形态特征

2.1.4. 沿江农田土壤和沉积物样品Cd、As活性

2.1.5. Cd、As形态含量与全量相关性分析

2.2. 江水水体中Cd、As对低潮滩农田土壤中Cd、As的分布影响

2.2.1. 江水水体中Cd、As的形态与分布

2.2.2. 江水水体中Cd、As的分布特征

目录

西江下游某滩涂农田土壤与江水中镉砷的分布特征

通讯作者: E-mail：wuyingxin@scies.org;

Distribution characteristics of cadmium and arsenic in the tidal flat farmland soil and the river environment in the lower Xijiang River

Corresponding author: WU Yingxin, wuyingxin@scies.org ;

计量

出版历程

西江下游某滩涂农田土壤与江水中镉砷的分布特征

通讯作者: E-mail：wuyingxin@scies.org;

English Abstract

Distribution characteristics of cadmium and arsenic in the tidal flat farmland soil and the river environment in the lower Xijiang River

Corresponding author: WU Yingxin, wuyingxin@scies.org ;

全文HTML

1.1. 研究区域概况

1.2. 污染来源

1.3. 采样及样品前处理

1.4. 分析测试

1.5. 质量保证

1.6. 数据处理

2.1. 沿江农田土壤和底泥样品中Cd、As分布特征

2.1.1. pH值

2.1.2. Cd、As含量分布

2.1.3. 沿江农田土壤和底泥样品Cd、As形态特征

2.1.4. 沿江农田土壤和沉积物样品Cd、As活性

2.1.5. Cd、As形态含量与全量相关性分析

2.2. 江水水体中Cd、As对低潮滩农田土壤中Cd、As的分布影响

2.2.1. 江水水体中Cd、As的形态与分布

2.2.2. 江水水体中Cd、As的分布特征

目录