Pollution characteristics and ecological risk assessment of heavy metals in paddy fields of Fujian province, China
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Pollution characteristics
and ecological risk assessment
of heavy metals in paddy fields
of Fujian province, China
Zhiming Kang1,2,3, Songliang Wang2,3*, Junhao Qin1, Renyue Wu2,3 & Huashou Li1*
To analyze the concentration, spatial distribution patterns, and ecological risks of heavy metals
(Cd, Cr, Pb, As, Cu, Ni and Co), 272 topsoil samples (0–20 cm) were collected from paddy fields in
Fujian province in July 2017. The results revealed that the mean concentration of all heavy metals
exceeded the background values in Fujian province, with the mean concentration of Cd being 5.20
times higher than its background. However, these concentrations of heavy metals were lower than
their corresponding national standards (GB 15618-1995). Spatially, for Cd, the high concentration
areas were located mainly in southeast of Sanming city and northeast of Quanzhou city. For Pb and
As, the places of highest concentration were mainly in southeast of Quanzhou city and Zhangzhou
city, and the main areas of high Ni concentration were distributed southeast of Nanping city. The
geo-accumulation index (Igeo ) of Cd and As were indicative of moderate contaminations, and the index
of Co, Cu and Cr suggested that these were practically uncontaminated. The nemerow integrated
pollution index (Pn) showed that the entire study area was prone to a low level of pollution, but at the
county level, Yongcun county and Zhaoan county are in an warning line area of pollution. According
to the potential ecological risk (RI ), the ecological risk belongs to the low risk of paddy fields in Fujian
province. However, Cd should be given attention (Er = 25.09), as it contributed to the majority of
potential ecological risks in Fujian province.
The large number of industrial waste, mining byproducts, chemical fertilizers, pesticides and other synthetic
chemical substances in the agroecological ecosystem has seriously threatened food security, food safety and
human health around the world1–6. Thus, soil pollution treatment is urgently needed to solve the current problems
in agricultural production. At the same time, the accumulation of heavy metals in agricultural soil is a serious
problem for human health and safe food p
roduction7–9. Heavy metal contaminants are commonly introduced
to soils through anthropogenic activities, such as mineral resources development, agrochemical use, fossil fuel
consumption, poultry manure, waste disposal, and sewage irrigation10–12. Soil heavy metal contamination has
become serious and widespread in China. According to the national communiqué of the soil pollution survey
by the ministry of environmental protection of China and the ministry of land and resources in 2 01413, some
regions of soil have become heavily contaminated, and the quality of cultivated soil is particularly concerning.
The total over-standard rate of soil (environmental quality standard for soils in China, GB15618-1995) in China
was 16.1%. Further, the over-standard rates of Cd, Cu, Hg, As, Pb, Ni and Cr were 7.0%, 2.1%, 2.7%, 1.5%, 4.8%
and 1.1%, r espectively13. A soil pollution control plan has been developed in China to improve soil quality, ensure
the quality and safety of agricultural products and protect the health of humans, such as a national action plan
“Soil Ten Chapter”14.
However, most of the prior studies were focused on a subset of typical areas, such as chemical factories, mining and smelting areas, to measure the heavy metal concentration of the sampling sites and then to assess the
1
College of Natural Resources and Environment/Key Laboratory of Agro‑Environment in the Tropics of Agriculture
Ministry of the People’s Republic of China/Guangdong Provincial Key Laboratory of Eco‑Circular Agriculture,
South China Agricultural University, Guangzhou 510642, China. 2College of Agriculture, Fujian Agriculture and
Forestry University, Fuzhou 350002, China. 3Key Laboratory of Ministry of Education for Genetics, Breeding and
Multiple Utilization of Crops, College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou 350002,
China. *email: ;
Scientific Reports |
(2020) 10:12244
| https://doi.org/10.1038/s41598-020-69165-x
1
Vol.:(0123456789)
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Figure 1. Location map showing the study area and sampling sites. (By the software of ArcGIS, version 10.2).
pollution level and ecological risk. Previously, some researchers concluded that there is heavy metal pollution,
causing concern for human health, in urban soils around an electronics manufacturing facility in Xianyang,
Hubei province, C
hina15. In addition, a case study conducted in Pahang, Malaysia, reported that iron ore-mining
had significant effects on surface soil heavy metals p
ollution16. Meanwhile, there are some domestic studies that
focus on mining regions in China, such as the gold mining area in Tongguan, Shanxi p
rovince1, the lead–zinc
mining area in Chenzhou, Hunan province17, Sb mining, lead–zinc mining, and pyrite mining areas in Lengshuijiang, Hengyang, and Liuyang, Hunan province18, the multi-metal mining area in Shaoguan, Guangdong
province19, and a tin-polymetallic ore field in the Guangxi Zhuang Autonomous R
egion20. However, most studies on heavy metal pollution are limited to small scale areas, such as cities, towns, villages, sub basins and field
test monitoring points. For example, Lü et al. found that in mining areas of You’xi County, the concentrations
of Cd, Cr, Cu, Hg, Pb, and Zn exceeded the background values of provincial and national s tandards21. And the
agricultural soils from Yangshuo county, Guangxi province also were heavily contaminated with Cd, Cu, Pb
and Zn, and exceeded national soil quality s tandards22. Diami et al. found that seven locations in the vicinity
of active and abandoned iron ore-mining sites in Pahang, Malaysia, the concentrations of Cu was exceeded the
soil guideline value at the all sampling locations16. Thus, it is clear that the research on heavy metal pollution
of agricultural land, especially in paddy fields, is very limited on large or moderate regional scales. However, to
better manage the quality of the soil environment, it is necessary to strengthen the study of heavy metal pollution
in paddy soils of a large regional scale, such as a provincial level. In recent years, the evaluation of levels and risks
for soil heavy metals pollution have been widely used to the methods of geo-accumulation index (Igeo), nemerow
integrated pollution index (Pn) and potential ecological risk index (RI ), which considers the lithology, maximum
value, toxicity variance of the different heavy metals and the comprehensive effect of multiple contaminants,
have been applied frequently15,23,24.
Rice production is an important contributor to China’s food s ecurity25. However, consumption of rice contaminated with toxic heavy metals has been reported in central China, such as the “Cd rice” in Hunan province26,27.
Meanwhile, (...truncated)
