Research articleSoil contamination in China: Current priorities, defining background levels and standards for heavy metals
Graphical abstract
Introduction
Soil pollution refers to the occurrence of some substances in soil caused by human activities, which can change soil quality and function, lead to soil degradation, damage basic soil structures and has the potential to harm human and environmental health. Soil pollution has been identified as a key national priority in China, with an increase of reports on agricultural land and human health affected by soil pollution (Luo et al., 2015). With economic growth and industrial restructuring in China, soil pollution from abandoned sites in urban areas has also drawn attention and concern regarding the safety of human settlements and human health in industrial and brownfield sites (Cao and Guan, 2007; Luo et al., 2015). According to the National Investigation Bulletin of Soil Pollution Status (NIBSPS) issued by the Ministry of Environmental Protection of the People's Republic of China (MEP-PRC), investment in soil remediation will reach up to RMB 4,633,000 million (£526,000 million). This is a huge financial commitment, so it is critical that sound science and knowledge are applied to the decisions that determine how this money will be spent. There is still work to be done in China to improve information to define soil background conditions and pollution status, the relevant science and policies needed to set soil quality standards, the assessment system for site evaluation and soil remediation strategies and technologies (State Council, 2016). The importance of soil pollution and degradation in China has now been recognized at the highest level, with specific requirements included in China 13th Five-Year National Development Plan and the Fifth Plenum of the 19th Central Committee of the Communist Party of China (MEP-PRC, 2016).
This paper focusses on an assessment of some of the priorities relating to heavy metals in Chinese soils. Soil heavy metal pollution has become a widespread and serious problem globally. Heavy metals are present naturally in soils, but elevated levels may be derived from agricultural activities, urbanization, industrialization and other human activities. To define and resolve pollution problems, it is therefore necessary to be able to define what constitutes ‘clean’, ‘background’ and ‘contaminated’ and ‘polluted’ soils. Following surveys and analysis of heavy metals in soils, many countries such as the United Kingdom, the United States and the Netherlands have developed such values. Depending on the national environmental management and regulatory processes, different countries have different approaches. Examples include the Soil Guideline Values (2009) in the UK, the US Soil Screening Levels (2002), the Intervention Values (2009) in the Netherlands, and Environmental Quality Standards (EQS) (1991 and 1994) in Japan.
China first developed its own Soil Environmental Quality Standards (SEQS) in 1995 (GB15618-1995) (Xia, 1996). So far, there are 63 current standards related to soil environmental protection in China and the number of standards released by the MEP-PRC has increased, especially in the last 5 years (Li et al., 2016). Following China previous focus on air and water quality, the Government has now turned a focus onto soils and groundwater, publishing a landmark ‘10-Measures for Soil Pollution Action Plan’ in 2016 (State Council, 2016). Its purpose is to manage, control and prevent soil pollution, to gradually improve soil quality in China. The Plan's first action recommends conducting surveys on soil pollution to better define the status of China's soil resources. GB15618-1995 first defined SEQS values for 8 heavy metals in China to apply to the whole country. Later, relevant soil quality standards in China were developed by referring to GB15618-1995 as a basic standard (Li et al., 2016). For example, the MEP-PRC issued a series of standards, such as ones for ‘Green food-technical conditions for environmental areas’ (NY/T391-2000), but these are rarely applied in practice. In contrast, European countries conduct soil pollution control mainly through a series of systematic assessment methods. These are based on different land use type, soil specificity or local environmental factors for understanding the risks either to the environment or human health. In China over the past 20 years, a general soil standard value (GB15618-1995) was applied to the whole country, without considering soil specificity and integrated environmental factors. During this period, in order to meet development needs, some regional standards for soil risk assessment were also set; for example, Beijing issued screening levels for soil environmental risk assessment of sites (DB11/T 811) in 2011.
A particular challenge for China is the country size and hence the range of soil types and conditions. Heavy metal concentrations vary naturally in soils, as a function of the geology, climate, land use etc. Hence, the Soil Environment Background Value (SEBV) will vary across the country. SEQS values were originally set nationally, so now there is an important discussion about whether different SEQS are needed regionally/locally. When managing contaminated sites, SEQS and SEBV will affect the selection, formulation and cost of remediation strategies.
Internationally, different countries have prioritized soil pollution and management in different ways. China has been eager to learn from this (Luo et al., 2015; Wang et al., 2005; Wen et al., 2010; Xia and Luo, 2007) and – given the Government's stated aim to manage its soil pollution problems effectively - has the opportunity to put in place sound, strong policies and management structures. An interesting comparison is with the UK, which has a long history and legacy of contaminated land problems and a mature environmental regulatory system (Luo et al., 2009; Wu, 2007). The 10-Measures Soil Pollution Action Plan strongly recommended that: surveys of the soil pollution situation be conducted; regulations and laws of soil pollution prevention be amended; soil pollution control and remediation be promoted; and a control system to prevent soil pollution be introduced (State Council, 2016).
Given the highly topical nature of soil contamination issues in China, in this paper we focus on the following questions: 1. What is the situation of soil heavy metal contamination in China? 2. What factors affect the background value of heavy metals in soils? 3. What are the background values of selected heavy metals and how do they compare between China and the UK? 4. What can we learn from the UK about soil survey methodologies and soil environmental standard assessment? 5. What are future priorities and next steps for China in its management of soil pollution?
Section snippets
Heavy metal soil pollution in China
As in other countries, key sources of heavy metals to Chinese soils include: metal mining and smelting; industrial activities, power generation; agricultural activities, including fertilizer and animal manure amendments; waste disposal activities; urbanization, transportation. In some regions, high contamination of the soil occurs around point sources, for example, mines and smelters – giving high but generally localized problems. In other situations, for example, agricultural soils,
Soil background values and factors that affect them
‘Soil environment background values’ (SEBV) are the concentration of elements or components in soil with little influence from human activities (Connor and Shacklette, 1975; Wang and Yang, 1990). They reflect the underlying geology and soil formation processes; hence they vary between locations and are commonly expressed as a range of values for a particular country or region. The background value could change over time, if environmental processes (including background human activities) affect
Experience from surveying UK soils
In the UK, there have been different national soil surveys in past decades. In the late 1970s, soil information in England and Wales was incomplete, knowledge of regional soil geochemistry was limited, available soil maps only covered ~25% of the area, and the existing information was not based on a representative and unbiased sampling strategy. Thus, between 1978 and 1983, the National Soil Inventory (NSI) carried out a survey of soil background metal concentrations in England and Wales (
Surveying Chinese soils
The earliest research on SEBVs in some selected city areas of China (Beijing, Nanjing, Guangzhou etc.) was in the mid-1970s. Subsequently, in 1978, SEBVs for 9 elements in agricultural soils and crops were surveyed in 13 provinces. In 1982, a background value survey was listed in the national key scientific and technological projects, which was carried out in a few of the main climate zones in northeast China, Yangzi River basin, Pearl River Basin etc. In 1990, a large-scope and systematic
Countryside Survey 2000
All elements were analyzed in different environments, classified according to Land Class and eighteen broad habitats and major soil groups and Countryside Vegetation System Aggregate Vegetation Class. Data are typically presented as figures (box-plots, scatterplots, frequency histograms etc.) to summarize the variation in different environmental factors. Mean values, standard deviations, median, maximum value and minimum values are commonly calculated to represent the primary analysis (Black et
Soil standards
Environmental Quality Standards (EQSs) for soils (GB15618-1995) in China were officially released in 1995. They were derived based on several factors: data on the soil background in China; data from soil ecological tests; data from geographically anomalous areas in China and information on soil standards or guidelines from abroad (MEP-PRC, 1995; Wu and Zhou, 1991). These EQSs set the maximum acceptable concentration of pollutants and relevant monitoring methods in the soil based on different
Current situation and future priorities
China is highly reliant on its ‘best quality’ soils for food security and agricultural production. It has been estimated that 20% of China total arable land is contaminated (Lin, 2004; Zhao et al., 2007). This may be different from the situation in most developed countries, where a higher proportion of agricultural land is not contaminated. For example, a higher (~93%) proportion of European agricultural land is considered safe for food production (Tóth et al., 2016). The reality is that China
Acknowledgements
We are grateful to Dr Lisa Norton and Dr Aidan Keith in Centre for Ecology & Hydrology-Lancaster for their contribution to the knowledge of the Countryside Survey.
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