Due to the differences in the main sources of soil pollution between the four sub-regions, data on the extent of polluted soils has been grouped by sub-region and is presented below. Given the absence of soil contamination and pollution monitoring systems in these countries, this section examines the most prevalent and/or unique cases of soil pollution reported in different literature sources. The literature sources include peer-reviewed research articles, reports and infographics made available by government and non-government organizations, press articles, personal communication with relevant expertise in the region. Unfortunately, comprehensive information on the extent of the areas covered by polluted soils is not available.
The region of South Asia, often referred to as the “Indian subcontinent”, includes Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan and Sri Lanka. Soil pollution is mainly the result of land use pressure from growing populations. Surface soils in this region are particularly vulnerable to trace element pollution due to the use of groundwater contaminated by geogenic substances, as well as anthropogenic sources.
The Bengal Delta is one of the most arsenic-polluted areas in the world. Concentrations of arsenic in groundwater are elevated by geogenic sources from aquifer sediments. Extraction of groundwater for rice irrigation transfers arsenic from groundwater to surface soils. Table 2 lists the evidence in this sub-region. In this sub-region, reporting of arsenic in the soil has been made mainly in Bangladesh and India. In several cases, the concentration of arsenic in the paddy soil varies depending on many factors, including reference concentrations (i.e., non-irrigated soil) (Lu et al., 2009). For example, due to different soil types and potential sources of arsenic pollution, a heterogeneous level of arsenic has been reported in all regional areas of Bangladesh (Table 2).
In addition to arsenic, other non-essential trace elements such as cadmium, chromium (VI), lead, and mercury are found in urban and suburban soils in the sub-region. Among the countries of South Asia, a considerable amount of literature is available on India, Pakistan, Sri Lanka and Bangladesh. For the other countries, the information available is more limited, which does not necessarily mean that the pollution problems are minor, but that there is a lack of knowledge and funding to assess the state of soil pollution. Therefore, only a few examples are given below.
Malik, Jadoon and Husain (2010) conducted a study on urban soil pollution by trace elements in Sialkot, Pakistan. Concentrations of some trace elements (cadmium, chromium, lead, nickel, and zinc) were above the maximum tolerable limits for soils (EU permission limit value) (Waseem et al., 2014). For example, the mean concentration of cadmium was found to be seven times higher than its permissible limit of 3 mg/kg (Malik, Jadoon and Husain, 2010). The spatial distribution of trace elements in surface soils in Islamabad also showed high levels of zinc, lead and nickel in built-up areas, and concentrations were affected by waste disposal and vehicle exhaust emissions (Ali and Malik, 2011). Faiz et al. (2009) found elevated concentrations of cadmium in soils near an expressway in Islamabad, with concentrations ranging from 5.8 mg/kg to 6.1 mg/kg. The average concentration of nickel in the soil samples was found to be 32 mg/kg. The spatial variation in concentrations of copper, lead and zinc appears to be due to atmospheric deposition resulting from traffic in urban areas of Karachi; the sources of these trace elements are mainly engine exhausts, wear of engine and tyre parts and spills from radiators and batteries (Karim et al., 2014). Karim and Qureshi (2014) found the main health hazard in urban areas was due to life-time exposure to trace elements such as zinc, chromium, copper and lead. Table 3 presents several examples of soil contaminated with trace elements in various regions of Pakistan.
Due to India’s very rapid economic growth through industrial, agricultural, and mining activities, its soils polluted with trace elements are also significant. In assessing almost 20 years of published literature (1991-2018) on Indian soils, Kumar et al. (2019) reported that in many cases, several trace element concentrations exceeded the Indian national guideline values as well as those of Canada, China, Poland and Sweden. These concentrations vary according to soil types. Table 4 listed examples of such cases:
Soil pollution was found to be significant for arsenic, cadmium, chromium, copper, lead, and nickel, considering anthropogenic activities as the main possible driver. Kumar and co-workers analysed the potential contamination index (Cp)2 of these trace elements and reported an overall risk of soil pollution by arsenic, cadmium, chromium, copper, lead, and nickel. The risk differed between soil types, with the soil in mining areas being the most exposed. Given the sensitivity of biological communities, Kumar et al. (2019) calculated in their studies the potential ecological damage caused by these trace elements and reported that overall cadmium was the contaminant with the highest risk of causing ecological damage in all soil types in India.
The status of soils in Nepal differs from other South Asian countries due to its mountainous landscape. KC and Kalu (2014) identified that Nepalese soils were generally deficient in nutrients, including phosphorus, sulphur, and manganese. However, in some soil types trace elements, including cadmium, lead and arsenic, were found at high levels. Population growth, industrialization, and unsustainable urbanization due to lack of planning and increasing demand for tourist accommodation are causing soil pollution by these trace elements, especially through their accumulation in surface soils. Yadav et al. (2019) tested house dust and nearby surface soil (0-15 cm) in four Nepalese cities (Kathmundu, Pokhara, Birgunj and Biratnagar) and confirmed the presence of seven priority elements (e.g. arsenic, cadmium, chromium, copper, nickel, lead, and zinc). The reported element concentrations, with the exception of arsenic and cadmium, were several times higher than the global average background concentration. Kathmundu and co-workers also considered the enrichment factor of these elements as an indication of source tracing and health impact, and reported that elements such as cadmium, lead, and zinc were highly enriched (Yadav et al., 2019). Health risk assessments revealed that high levels of trace elements, particularly chromium and lead, could result in a greater non-carcinogenic health risk to the local people, while lead, cadmium and nickel were identified as carcinogenic risk factors as a result of direct exposure to surface soil and dust in households (Yadav et al., 2019).
Bangladesh is densely populated with more than 160 million people. As a developing nation, economic growth and rapid development are major priorities that are reflected in industrialization and urbanization. Environmental pollution is increasing throughout the country but environmental protection has not been prioritized. Tanneries and brick kiln industries are sources of soil pollution by trace elements and pose a serious threat to the environment as well as human health (Karim et al., 2012). Hazaribagh, in the city of Dhaka, is considered a highly polluted site due to discharges of tannery effluent loaded with chromium. Extremely high levels of chromium were detected at the site and an excessive concentration of chromium (III) (37 000 mg/kg) was found in subsoils (Karim et al., 2012). Although chromium (III) is generally immobile in soil at neutral to alkaline pH, the low pH and the presence of manganese oxide could transform it into more hazardous chromium (VI). This study also reported that topsoil at the tannery site was contaminated with high levels of organohalogen compounds (e.g. PCBs, pesticides, chlorophenols, halogenated hydrocarbons) (max. 1 200 mg/kg) and sulphur compounds (500-1000 mg/kg) (Karim et al., 2012).
The brick industry is growing rapidly due to the high demand for bricks for construction. Approximately 7 000 brick kilns are currently operating in Bangladesh. Approximately 1 million people are employed by this industry, and it is estimated that about 1 percent of national GDP income is derived from it (Hossain et al., 2019). Kilns have been established in an unsystematic manner, particularly in agricultural areas, leading to land degradation (Kumar et al., 2021). This is also a continuing issue for other developing countries such as India, Pakistan, and Nepal (Bisht and Neupane, 2015; Ismail et al., 2012). The literature shows that a significant amount of fertile land has been sacrificed for industrialization, such as brick kilns. These kilns are sources of serious environmental pollution that impacts on soil quality and also has a negative effect on human health (Bisht and Neupane, 2015). Associated industrial activities, including coal and fuel combustion and wood-burning, have introduced various contaminants in the soils around the brick kilns. In a study in the Tangail district of Bangladesh, concentrations of trace elements including arsenic (2.5-28.4 mg/kg), cadmium (1.0-8.1 mg/kg), chromium (0.8- 21.7 mg/kg), copper (3.1-38.6 mg/kg), lead (2.2-18.3 mg/kg), and nickel (4.7-27.7 mg/kg) were found in soils in the vicinity of a brick kiln. The variations in concentration was dependent on the sampling locations (Proshad et al., 2017). As Bangladesh’s national soil guidelines have not yet established limit values for contaminants, ecotoxicological assessments tend to relate to limit values set by other countries. For example, the Canadian Environmental Quality Guideline values for agricultural soils are arsenic (12 mg/kg), cadmium (1.4 mg/kg), copper (63 mg/kg), chromium (64 mg/kg), lead (70 mg/kg), and nickel (45 mg/kg) (CCME, 1999). In Bangladesh, brick kilns are often located adjacent to agricultural lands. Mean values for all elements examined in soils near brick kiln were within the Canadian Environmental Quality Guideline values except for cadmium, which was almost 2.2 times higher. This study also investigated the ecological risk assessment of soil pollution, such as contamination factor, enrichment factor, geo-accumulation factor and pollution load index. The results indicated soil pollution by arsenic and cadmium as they had the highest enrichment factor values (Proshad et al., 2017). The mean geo-accumulation value for cadmium was 3 104 mg/kg, which also indicated that the soils were contaminated with cadmium (Proshad et al., 2017). The typical background level of arsenic in soil is 5-10 mg/kg (Smedley and Kinniburgh, 2002), while the maximum level of arsenic (28.4 mg/kg) found in this study was much higher.
Soil nutrient pollution, resulting of excessive use of chemical fertilizers, and the input of persistent organic pollutants (POPs) into the soil due to the non-selective (e.g., broad spectrum pesticides) and unregulated use (e.g., lack of strict monitoring) of pesticides, are also two critical problems in the region.
Some of the main causes of soil pollution in Sri Lanka arise from the use of agrochemicals such as inorganic fertilizers and pesticides. The majority of Sri Lankan farmers have been using these agrochemicals since the 1950s, and their use has increased significantly since the introduction of fertilizer subsidy schemes and increased productivity programs (Weerahewa, Kodithuwakku and Ariyawardana, 2010). Sri Lankan farmers apply more fertilizers and agrochemicals than are recommended on their labels, notwithstanding the advice from the Department of Agriculture. Excessive application of fertilizers is also a problem in the interior regions of Sri Lanka. In the vegetable growing area of Nuwara Eliya, soil phosphorus levels and potassium levels are high. Ariyapala and Nissanka (2006) found that the relative proportion of overuse of fertilizers by potato farmers in the Nuwara Eliya district in Sri Lanka was 57 percent for nitrogen, 82 percent for phosphorus and 79 percent for potassium.
Rice is the staple food in Sri Lanka. Over the years, the Sri Lankan government has provided fertilizer subsidies to farmers to increase paddy production yields. Although this has led to increased paddy production and, consequently, national self-sufficiency in rice production (Ekanayake, 2009), researchers have expressed concerns about food safety and water pollution due to misuse of fertilizers (Rodrigo and Abeysekera, 2015). The use of fertilizers for food crops in Sri Lanka began in the early 1950s, but widespread use of chemical fertilizer in agriculture only started in 1960. Initially, the application of mixed fertilizers containing nitrogen, phosphorus and potassium nutrients was recommended. However, in the 1990’s, with policy changes, the Department of Agriculture encouraged farmers to use single nutrients instead of mixtures (Weerahewa, Kodithuwakku and Ariyawardana, 2010). The objective of this exercise was to encourage farmers to make measured decisions to apply the appropriate quantities of each nutrient that were needed for their specific soils and food crops. However, there was limited availability of singular nutrients in the local market (Weerahewa, Kodithuwakku and Ariyawardana, 2010). The fertilizer triple phosphate (TSP) imported to Sri Lanka has been reported to contain 23.5-71.7 mg/kg of cadmium. Water from the Mahaweli River is used for irrigation of agricultural lands in many areas of Sri Lanka. Bandara et al. (2008) investigated the total amount of cadmium entering the reservoirs in the North Central Province (NCP) resulting from cadmium input from TSP fertilized rice and vegetable fields. The cadmium concentration in the reservoir sediments was in the range 1.77-2.45 mg/kg dry weight.
The Indian subcontinent has long used persistent pesticides, including DDT and lindane, both of which are POPs. Cotton production is the most pesticide-intensive cultivation in India, accounting for about 50 percent of all pesticides used in the country, followed by rice, sorghum, vegetables, wheat and oilseeds. In a review article, Yadav et al. (2015) reported that although per capita pesticide consumption in India is relatively low, residues of these compounds in environmental systems, including soils, are high (Abhilash and Singh, 2009). The presence of POPs in soils depends on the area, soil types and seasonal variability (Yadav et al., 2015b). Sruthi et al. (2017) tested a total of 63 samples from paddy fields (21 sites) in the Kuttanad agro-ecosystem and reported that a wide range of organochlorine pesticides (OCPs) were detected, including lindane and its by-product beta-HCH, chlordane, dieldrin, aldrin, endosulfan and DDT. Although many were found most commonly across the sites of the studied region (beta-HCH = 2.26-9.6 ng/g soil, chlordane = 0.33-9.1 ng/g soil, heptachlor = 1.01-8.52 ng/g soil), they fell within the acceptable limit set by the US-EPA. The authors determined that this residual availability in soil was due not only to residues of recently used pesticide, but also those of historically applied pesticides. In addition to pollution through their use, releases of POPs pesticides during manufacture, transportation and disposal have also caused soil pollution. Soils are contaminated at pesticide production sites such as former HCH producers in India (Jit et al., 2011) and former DDT production in Pakistan (Younas et al., 2013).
In Bangladesh, OCPs are present in soil and water due to their widespread use before being banned under the Stockholm Convention. A study evaluated the concentration of DDT in soil near the DDT factory in the Chittagong district. High concentrations of DDTs were detected, with areas extremely contaminated by technical DDT, with concentrations up to 290 g/kg (Al Mahmud et al., 2015). Although severe cases of pollution of water bodies and contamination of food products have been reported in Bangladesh, information on POPS in soil is rare (Islam et al., 2018a).
Although there is ongoing research on the fate and migration of POPs in soil, it is expected that these compounds will be retained in soil for a long time without rapid decomposition (Gevao, Semple and Jones, 2000).
Lack of municipal solid waste collection facilities and poor waste management practices continue to lead to severe soil pollution in Sri Lanka (Bandara, 2008). Studies before 2006 reported that only 24 percent of households in Sri Lanka had access to waste collection services, and in rural areas this dropped to only 2 percent. Waste generation is increasing due to urbanization, industrialization, increased consumption and population growth. Collected wastes are often brought to open dumps and are not treated. These dumps tend to be located close to environmentally sensitive places and residential areas. Soil and water pollution issues are serious, exposing many sensitive people, such as young children and pregnant women, to serious health risks. In addition, soil erosion occurs on 44 percent of the country’s agricultural lands and is also a major environmental issue (Bandara et al., 2001).
The first national soil pollution survey report for mainland China, covering 630 million hectares, was released in 2014 on the basis of the study carried out in 2005-2013 jointly by the Ministry of Ecology and Environment and the Ministry of Natural Resources (MEP and MLR, 2014). The survey classified 16.1 percent of the studied soils as polluted according to the limits set in the national guidelines, Chinese Environmental Quality Standard for Soils (GB 15618-1995). The study assessed the proportion of polluted soils by the following land use classifications: farmland (19.4 percent), forest land (10.0 percent), grassland (10.4 percent) and unused land (11.4 percent).
According to the report, 82.8 percent of all contaminated soils were found to be polluted with trace elements, such as arsenic, cadmium, copper, lead, and mercury. In some soils priority organic contaminants also exceeded safety guideline values. For example, of all soil samples tested 1.9 percent, 1.4 percent, and 0.5 percent were found to be contaminated with DDT, PAHs and hexachlorocyclohexanes (HCHs), respectively (CCICED, 2015; Xiaoming, Junxing and Wei, 2018). Food crops that exceed contamination limits are widespread in some areas, particularly in southern China. For example, a considerable proportion of rice grains exceed the cadmium limit. Nearby mining and industrial activities have had an impact on farmland, leading to widespread public concern about food safety in recent years (Zhao et al., 2015). Details of the distribution of contaminated sites were not revealed in the 2014 National Soil Pollution Survey. However, since 2017, under the new soil pollution law, local governments are required to submit information of polluted sites in order to compile a “Pollution List” to control, remediate and manage these polluted areas (CHN-MEE, 2017). As of October 2018, 27 of the 31 provincial capitals had published a total of 174 polluted plots. Among them, Tianjin, Chongqing and Shanghai have the largest number of polluted sites, with 21, 17 and 14 respectively. Harbin, Xi’an, Fuzhou, Changchun and Nanning reported only one polluted site each. Greenpeace East Asia and the Nanjing University Ecology Department compiled the information and analysed the list of polluted sites published by the provincial capitals, industry and the type of contaminant. According to this study, almost 60 percent of the sites were related in some way to the legacy of industrial plants. For example, chemical plants accounted for up to 41 percent, followed by steel plants (12 percent) and industrial manufacturing sites (9 percent) (GreenPeace, 2019b). Sites polluted by chemical plants were mainly in Tianjin, Taiyuan, and Wuhan, while steel plants and manufacturing factories, respectively were the source of polluted sites in Beijing and Chongqing. Cities also varied in terms of the types of contaminants. For example, Wuhan was identified as the worst in terms of the diversity of contaminants present, and remediation of sites in Shenyang and Hangzhou was deemed difficult due to the mixing of contaminants. Trace elements were the main contaminants, accounting for 54 percent of studied sites that were polluted by trace elements. The most common was chromium which was found in approximately 10 percent of the sites. For organic contaminants, volatile organic compounds (VOCs) (including semi-volatile organic compounds) were detected in about 40 percent of the sites and PAHs and total petroleum hydrocarbons were the main contributors in this category, representing 11 percent and 14 percent, respectively.
Another recent review of trace elements concentrations in soils at 402 industrial sites and 1 041 agricultural sites indicated trace elements pollution, with arsenic, cadmium, and lead being of high concern (Yang et al., 2018). Compared to agricultural regions, the risks in industrial regions are more severe. Among all industrial sites, abandoned mining areas should be controlled as a priority due to their higher risks. In general, trace elements pollution is more serious in southeast China than in its northwest. Liu and co-workers carried out a comprehensive assessment focusing on soil pollution by trace elements in mining areas and recommended that the southern provinces and Liaoning province should be prioritized for control (Liu et al., 2019). The assessment should prioritize areas where antimony, lead, manganese, tungsten, and zinc were mined; and should focus on trace element pollution by arsenic, cadmium, copper, lead, mercury, nickel, and zinc. Compared to soils influenced by metal mining, trace element concentrations in soils around coal mine were much lower (Liu et al., 2019).
A recent review was carried out based on published studies of polluted arable land in China, focusing on trace elements, organochlorines, and polycyclic aromatic hydrocarbons (Zeng et al., 2019). A total of 553 reports published in the Web of Science and China National Knowledge Infrastructure, between 2000 and 2018 were reviewed. These contained analysis of 5 597 samples from 1 781 farmland soils in 31 provinces, municipalities, and autonomous regions of China (Zeng et al., 2019). This review demonstrated that 22.1 percent of China’s farmland soil present a mixture of contaminants, while 20.8 percent of soils are likely to pose a carcinogenic risk to the adult population and an even greater risk to children. The total non-carcinogenic hazard quotients for farmland soil pollution were within the safe threshold for adults, but slightly above the limit for children. The ratio of total farmland area with carcinogenic risk quotients above the safety threshold of 1 × 10−5 was only 1.02 percent for adults and 20.8 percent for children. The review pointed out that land used for food and vegetable crops should be given priority for control and remediation actions over other types of land use. Zeng and co-workers also stated that Yunnan, Hunan, Anhui, Henan, and Liaoning provinces should be controlled as a priority because of their severe pollution and high risks to human health.
Overuse of fertilizer is also a major source of trace element pollution. Excessive nitrogen fertilization in intensive agricultural areas has led to serious environmental problems such as eutrophication. In China, nutrient additions in many fields far exceed those in the United States of America and northern Europe (Vitousek et al., 2009) and much of the excess fertilizer is lost to the environment, degrading both air and water quality. One study found that a 30-60 percent reduction in nitrogen fertilizer halved nitrogen losses to the environment without significantly reducing crop yields (Ju et al., 2009).
Apart from farmland soil pollution, roadside soil pollution in China’s urban and suburban areas is another problem. This is primarily caused by the deposition of toxic chemicals emitted by vehicles. Yan et al. (2018) collected 25 topsoil (0-10 cm) samples from 2 roadsides in the city of Shanghai. Concentrations of antimony, copper, cadmium, lead, mercury, and zinc were found to be higher than the baseline concentration in soils. Heavy traffic on these roads was postulated to be the source of the high deposition of trace elements in surface soils, as the elements concentration decreased with the distance between the sampling site and the road. This study corroborated the results obtained on other roadside soils and plant tissues where heavy traffic was identified as one of the causes of pollution in China (Hou et al., 2019; Wang and Zhang, 2018; Xiao et al., 2019; Zhang et al., 2016).
The main contaminants identified in the agricultural areas of Taiwan Province of China are trace elements, including arsenic, cadmium, chromium, copper, lead, mercury, nickel, and zinc, from the irrigation of paddy fields using arsenic-contaminated groundwater, wastewater discharged from industrial parks and transport areas. Figure 9 shows the main polluted agricultural areas in Taiwan Province of China, according to the Taiwan EPA. The data was based on various scientific papers that show the status of soil pollution in different locations by different trace elements in Taiwan Province of China (Chen, Lee and Liu, 2000; Chen, 1992, 1991, 2000; Lai et al., 2010). More than 700 ha were polluted before 2000 (Taiwan-EPA, 2019a).
The most seriously polluted agricultural areas (about 300 ha) were located in the Ta-Yuan and Chu-Wei townships of Taoyuan city, near Taoyuan international airport, surveyed in 1989-2000. They were polluted by wastewater discharge from the Chung-Li Industrial Park of northern Taiwan. The townships of Changhua and Hemei in Changhua prefecture (about 300 ha), near Taichung City, were also polluted and surveyed in 1990-2000, but by wastewater discharge from illegal factories (e.g. electric coating) and domestic industrial parks in Central Taiwan. Based on the “Soil and Groundwater Pollution Remediation Act (SGWPR Act)” (Taiwan-EPA, 2019c) all the polluted rural soils were completely cleaned up in 2010-2020. There is only one copper mining site operated before 1970 to produce the copper and arsenic pollution area in northern Taiwan (Taiwan-EPA, 2019a).
Soil pollution in this part of the region comes mainly from industrial activities, including mining, coal-burning and solid waste disposal. Coal-powered power plants are predominantly used in East Asia, and therefore the atmospheric deposition of acid in the soil in the region, as well as associated contaminants such as trace elements, has serious environmental consequences (UNEP, 2020).
While 86 percent of the solid wastes in the Republic of Korea are recycled and reused as resources, the country faces soil pollution through abandoned mining sites, industrial complexes, military bases, metal smelters, livestock burial grounds, as well as road and railway sites. These sources of soil contaminants have increased due to economic development and changes in the country’s industrial structure. Since 2015, 21 798 potentially polluting facilities, such as petroleum and toxic substance storages, have been installed (KOR-MOE, 2016). With technological developments and industrial expansion, an increasing variety and quantity of hazardous chemicals are being manufactured and distributed, generating ever more solid and liquid wastes that increase the risk of soil and water pollution.
In 2015, the Ministry of the Environment of Republic of Korea monitored soils at 1 000 sites for eight trace elements, 13 other compounds and pH. They found that mercury and zinc were the most common contaminants at these sites (KOR-MOE, 2017a).
From late 2000 to mid-2010, the main concerns for soil remediation in the Republic of Korea were oil (TPH, BTEX) and trace elements (arsenic, cadmium, chromium (VI), copper, mercury, and lead). Since then concerns have also been raised regarding soils contaminated with PCDD/Fs and fluorine. In 2015, local governments investigated 53 sites, 2.1 percent of which were heavily contaminated with various contaminants, many of which exceeded the national acceptable levels, including those present in Inchoen, Gyeonggi-do Province and Seoul. The 53 sites comprised: 15 transportation facilities, 12 waste disposal and recycling facilities, 6 storage and use areas of ore and scrap, 5 children’s playgrounds, and 4 industrial areas. Contaminants that exceeded national acceptable levels were zinc (22 percent), TPH (13 percent), lead (11 percent), and copper (10 percent) (KOR-MOE, 2017a). This report ranked the contaminant’s impact on human health as: lead > copper > zinc and TPH.
The above-mentioned trends in soil pollution in the Republic of Korea are linked to the main sources of pollution in the country. There were 1 276 abandoned mining sites (936 for metal and 340 for coal) (KOR-MOE, 2015). At industrial complexes located in 530 different locations in the Republic of Korea, soil and groundwater are vulnerable to pollution by trace elements and chemicals because the industrial complexes that are concentrated there. The Janghang copper smelter in Chungnam Province (operational period 1936-1989) and the Bonghwa Seokpo zinc smelter in Gyeongbuk Province (operational since 1970) contributed significantly to the trace elements contamination in surrounding soils. Trace elements included arsenic, nickel, cadmium and sulphur, and compounds such as nitrogen oxides were reported to be released into the soil. The pollution around the Janghang smelter has been subject of a major remediation programme which is discussed in Chapter 13.
In addition, the American Forces in Korea are relocating their military bases within the Republic of Korea: of the 80 bases, 54 have already been returned to the Government, while the remaining 26 will be returned soon (KOR-MOE, 2017b). Most of the bases are heavily polluted with oil (e.g. the US military base in Yongsan), trace elements and PCDD (e.g. Bupyeong Camp Market in Incheon), and there is a great concern about serious health threats to nearby residents (KOR-MOE, 2017b).
Japan is an example of efficient solid waste management and value-added manufacturing. For example, it has been reported that Japan has implemented the “waste-to-energy” concept, in which approximately 70 percent of waste is used to produce energy (Jones, 2018).
Soil pollution by radioactive substances remains a significant problem in Japan. The most recent event was a major event of radionuclide pollution around Fukushima. On 11 March 2011, the Fukushima Daiichi nuclear power plant was damaged by a tsunami, releasing radionuclides. In May 2013, the UN scientific committee on the effects of atomic radiation concluded that there was no immediate health impact from exposure, but that future impacts were still undermined (WNA, 2020a). However, massive soil contamination (primarily with caesium-137) remains a significant concern. Yasunari et al. (2011) conducted dispersion and deposition modelling of caesium-137 between 20 March to 19 April 2011, and reported that soils in the immediate vicinity of the nuclear plant could be contaminated with this radioactive substance with a disposition of 100 000 MBq/km2 and the surrounding area with 10 000 MBq/km2. The authorities initially planned to use this massive amount of soil collected from the 13 000 km2 exposed area for construction purposes, such as road foundation and embankments, where the radioactivity level was detected at 8 kBq/kg (WNA, 2020a). However, there has been considerable public concern about the possibility of reusing these “contaminated” soils (McCurry, 2019). This article reported that numerous bags containing millions of cubic metres of contaminated topsoil had been moved to interim storage facilities until the permanent disposal site would be constructed away from Fukushima (McCurry, 2019). Tsubokura et al. (2016) conducted another study (12 March 2013 to 11 March 2014) to understand the correlation between the availability of caesium-137 in the human body and the concentration of this element in soil. They concluded that although the study had several methodological limitations (e.g. only voluntary human participation), there was a weak association that only high levels of soil pollution (e.g. >100 KBq/km2) could be responsible for the availability of this radionuclide in the human body. Later, on 20 May 2017, several research papers were presented at the Japanese Geoscience Union – American Geoscience Union (JpGU-AGU) Joint Meeting and preliminary results revealed that there was a high level of caesium-137 five years later following the first accident at Fukushima. The average level radioactivity was still approximately 90 percent of that detected around the plant immediately following the accident in 2011 (AGU, 2017). The radionuclide was also found to form insoluble particles (≤100 µm in diameter) with debris and settled on the soil surface, and their health impact or fate (e.g. migration in the soil depth profile) has yet to be determined (AGU, 2017).
The Southeast Asia sub-region includes the Association of Southeast Asian Nations (ASEAN) plus Timor-Leste. The ASEAN member states are Brunei Darussalam, Cambodia, Indonesia, the Lao People’s Democratic Republic, Malaysia, Myanmar, the Philippines, Singapore, Thailand, and Viet Nam. With an aggregate GDP of USD 2.4 trillion, ASEAN is the sixth-largest economy in the world (ASEAN, 2017) Its GDP growth is associated with a growing population and urban expansion. The executive summary of the fifth ASEAN State of the Environment Report indicates that 47 percent of the population in the region lives in urban areas, and this proportion will increase to 63 percent by 2050. Singapore, Brunei Darussalam and Malaysia are already highly urbanized, with more than 75 percent of the population living in urban areas. Solid waste generation is therefore one of the main sources of soil pollution in Southeast Asia.
Trace elements pollution is high in the region and Ding (2019) reported that the problem has worsened due to the growing number of chemical industries in the southeast Asia and the weak environmental regulation. Agriculture and forestation-deforestation are also important activities in this region that affect soil quality (ASEAN, 2017). According to the fifth ASEAN State of the Environment Report (ASEAN, 2017), chemical degradation is a significant threat to soil quality. The term chemical degradation is defined as “the accumulation of toxic chemicals and chemical processes that then impact on the chemical properties that regulate life processes in soil” (Logan, 1990). There are identified or unidentified polluted sites throughout the region, however the compilation of recent data is rare. Examples from Thailand and Myanmar are presented below.
Thailand is one of the fastest-growing countries in the region and concern about polluted sites is also growing, not only because of their indigenous wastes but also because of imported contaminants (Diss, 2019). In Thailand’s 32 year industrial history, there are about 52 major polluted sites (Figure 10). The main sources of pollution are mining, petrochemical industries and illegal dumping, as well as waste processing facilities (including landfills and recycling facilities). Mining is the main cause of trace elements pollution in soil, sediments and surface waters. Currently, Thailand has four polluted sites around the country as a result of mining. Klitty Creek’s lead pollution (up to 200 000 mg/kg lead in sediment) in Kanchanaburi province is being remediated by sediment dredging (contaminated for more than 20 years) (Phenrat Tanapon et al., 2016). On the other hand, the paddy field in the Mae Tao-Mae Ku watershed in Tak province is polluted with cadmium, with levels over 20 mg/kg at sites covering 336 ha (Phenrat and Otwong, 2015; Simmons et al., 2005). Similarly, over the past 5 years, arsenic and cyanide pollution has been reported at two gold mines, one in Loei province and the other in Pichit Province (Kummetha and Areerat, 2014; Rujivanarom, 2018). Two of the sites (Tak and Loei provinces) have been ordered by the court to remediate, while the Pichit site is the subject of arbitration between the company and the Thai government.
E-waste has become an emerging and significant issue in Thailand. Imported e-waste adds to the burden of domestically generated e-waste and is a serious concern for soil quality in Thailand (Figure 11). In 2018, Thailand received 250 000 kg of e-waste from Australia, 500 times more than that of 2017 (Diss, 2019). This includes electronic scrap, battery parts and electrical machinery. In the e-waste dismantling community in Klong Chai district, Kalasin Province, it was found that lead and chromium concentrations in water in streams near the dismantled electronic waste landfill were higher than the standard of the Pollution Control Department (Neeratanaphan et al., 2017). Soil samples taken from around the dismantled e-waste landfill also presented higher concentrations of lead and chromium that affected rice grown in the surrounding rice paddies. Soil around the dismantled e-waste landfill in Bangkok, in the Sua Yai Uthit community, had five times higher concentrations of copper, lead, nickel, and zinc than soils from residential areas without e-waste dismantling (Damrongsiri, Vassanadumrongdee and Tanwattana, 2016). Some sewer sediments had very high concentrations of copper (26-3 541 mg/kg), lead (21-34 976 mg/kg), and zinc (156-3 471 mg/kg) in this area and ultimately flowed into public waterways. The main cause of this pollution was potentially surface soil contaminated by small fragments of e-waste (Damrongsiri, 2018).
Backyard or artisanal extraction of valuable trace elements from e-waste, in addition to polluting the land, has progressively shown health impacts. Artisanal e-waste recycling facilities in Southern Thailand revealed very high lead concentrations in Songkhla province, which were seven times higher than the Pollution Control Department standard. Lead was absorbed into the body, resulting in blood lead concentrations between 1 and 17 µg/dL, being in some cases above the Department of Disease Control’s safety level of 10 µg/dL (Kiddee and Decharat, 2018).
Myanmar is rich in natural mineral resources and has numerous mining sites. Many mine sites in Myanmar started their operation before 2016, when Myanmar did not have Environmental Impact Assessment (EIA) regulation. As a result, mining activities, particularly the management of mining waste was not well managed and caused serious damage, including soil erosion and soil pollution. Agricultural lands in the flood plain are affected by the poor management of mining waste. For example, following acid mine drainage of a coal-mine waste heap in Ban Chaung, Dawei District, Myanmar, pollution of surface water and surface soil was also observed. As shown in Figure 12, a rusty precipitate, a sign of acid mine drainage, affected a nearby agricultural area. Presumably due to low pH and high electrical conductivity, betel nut trees, a plant with low salt tolerance, died. The affected agricultural soil appeared to have much higher concentrations of arsenic and iron than the soil sample from an unaffected control area. Phenrat (in press) reported that the arsenic and iron concentrations in the affected soil were 11.5 mg/kg and 43 266 mg/kg respectively, while the unaffected soil had arsenic and iron concentrations of 3.8 mg/kg and 18 943 mg/kg, respectively. The arsenic and iron pollution are clear signatures of acid mine drainage pollution. No remediation was carried out, neither in the affected natural waterway nor in the affected agricultural soil.
The mining site in the Tanintharyi region of Myanmar has also released various concentrations of trace elements including arsenic, lead and manganese (Table 5). Of these, the soil of two villager’s plots presented arsenic concentrations of 5.24 mg/kg and 4.7 mg/kg respectively, both as a direct contribution from the mine waste. Both exceeded Thailand’s background soil concentration limit (Phenrat, 2020).
Although Australia has more regulations than many countries in this region, the trend in hazardous waste generation is upward. Hazardous waste, which contains a wide range of toxic chemicals, increased by 34 percent in 2017-18 compared to what was reported for 2014-15 (Figure 13). Of the estimated total hazardous waste, approximately 35 percent was excavated polluted soil, while other types of wastes were asbestos 21 percent, tyres 6 percent, grease trap wastes 6 percent, waste oils 4 percent, oil-water mixture 4 percent, alkali 4 percent, animal effluent and residues 3 percent, paints, resins, inks and organic sludge 3 percent and zinc compounds 2 percent (Latimer, 2019).
The report published by the Australian Government’s Department of Environment and Energy states that polluted soil volumes have broken their “historical trend” by 2019 and have decreased after a steady increase in previous years. The identification of “emerging contaminants” in soil, for example, per- and poly-fluoroalkyl substances (PFAS), could contribute to the increase in the amount of contaminated soil in Australia (Latimer, 2019). The report identified that the biosolids often applied to land and fire-fighting foams containing PFAS had contributed significantly to soil pollution in Australia with a significant increase from previous estimates (Latimer, 2019). However, the actual number of PFAS contaminated sites is not known (Bavas, 2019) although the Australian defence and the PFAS data tracking map has updated past and potential PFAS contaminated sites (AUS-DoD, 2020).
Of the total hazardous wastes generated in Australia, approximately 57 percent ended up in landfill, compared to 19 percent for recycling, 10 percent for special treatment and 10 percent for storage pending to be managed in accordance to regulation and available facilities (Latimer, 2019). Although landfill sites in Australia are operated and monitored by a variety of management authorities (e.g. private and local government-owned), a recent study reported that at least five PFAS compounds such as perfluorohexanoate (PFHxA), perfluoroheptanoate (PFHpA), perfluorooctanoate (PFOA), perfuorohexanesulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) were detected in leachate from 27 landfills studied in Australia, with the highest concentration of PFHxS (1 700 ng/litre (mean), min. 73 ng/litre, max 25 000 ng/litre) (Gallen et al., 2017).
Chemicals inherited from industrial sources and diffusion into the soil system could be responsible for several instances of soil pollution by trace elements. In the Melbourne metropolitan area, lead had exceeded the Australian Health Investigations Levels guideline value (300 mg/kg) at some sites. Laidlaw et al. (2018) reported that at least 8 percent of the 13 community garden beds and 21 percent of the 136 residential vegetable gardens were contaminated with lead. In soils from residential garden beds, lead concentrations of less than 4 mg/kg up to 3 341 mg/kg were detected, while in community vegetable garden beds, concentrations of 17 mg/kg to 578 mg/kg were found. It is interesting to note that there may be a link between the use of paint outside of houses and the availability of lead in garden soil.
Australian mine sites, both former and active mines, present a soil pollution risk through acidic mine drainage/sludge, leakage from oil storage, and on-site landfilling of process wastes (Abernethy, 2018). Australia has approximately 60 000 abandoned mining sites, which have become a serious environmental problem, particularly with regard to soil pollution (Hosie, 2017; Nogrady, 2018; Unger, 2014). For example, Abraham, Dowling and Florentine (2018) studied soil pollution at a former gold mine site in Central Victoria, Australia and reported the following trace elements median concentrations: arsenic (85 mg/kg), mercury (2 mg/kg), lead (30 mg/kg), copper (30 mg/kg) and zinc (94 mg/kg), all of which had exceeded the upper average soil concentration at the national (Australia) and state (Victoria) levels. However, only arsenic and mercury were found to be toxic to ecological receptors and human health. There are significant public health concerns, as pollution not only affected nearby residential areas, but rain runoff and wind erosion could cause health impacts in more distant populations (Abraham, Dowling and Florentine, 2018).
In Australia, solid waste generated by the rapid growth of solar panel installations now appears to be a new concern for landfills (Figure 14). Normally, the lifetime of a solar panel is about 20 years, so early installed panels are being retired in Australia. As of December 2019, at least 2 million Australian household roofs have been equipped with solar panels (Hasham, 2019). Salim et al. (2019) estimated that annual residential solar panel waste would increase to 1 532 000 tonnes by 2050, while battery waste would increase to 100 000 tonnes by 2050. The main components of solar panels - the photovoltaic panel - are glass, polymer and aluminium, but they may also contain potentially hazardous elements such as lead, copper and zinc, gallium, tellurium, indium, rare earths and plastics. These rare earth elements could be recycled to reduce the environmental burden; however, attracting profitable businesses to the sector is a barrier. Storage of these panels on land is therefore a natural concern in the event of leaching of trace elements into the soil or groundwater (Shellenberger, 2018).
A recent report entitled “Our Land 2018” published by the Ministry for the Environment and New Zealand State highlighted the current and potential trend of soil pollution caused by hazardous chemicals in New Zealand (NZ-MfE and NZ-Stat, 2018). In New Zealand, only local authorities (e.g. councils) keep independent records on the occurrence of point source pollution, types of pollution and specific location. New Zealand Government records indicate that there are at least 20 000 potentially contaminated sites (NZ-MOE, 2019). However, the exact extent of soil pollution is reportedly unknown (NZ-MfE and NZ-Stat, 2018). According to this 2018 report, the following hazardous chemicals are typically found in various soil sites, caused by anthropogenic activities, including:
Recently in 2017, New Zealand included PFAS in the Emerging Organic Contaminants (EOCs) category, and several initiatives have been taken to identify PFAS contaminated sites and manage them according to the guidelines (HEPA, 2019). In a technical report prepared for the councils in New Zealand on environmental guidelines for emerging organic contaminants, Stewart et al. (2016) reviewed the literature and summarized that several EOCs, including phthalates, PFASs, pesticides, pharmaceutical residues and hormones reside in soil and could migrate through soil to groundwater. In 2014, Stewart et al. (2014) conducted a survey to assess the concentration of EOCs and trace elements in sediments from various locations in Auckland and reported that, although a wide range of EOCs (e.g. Total polybrominated diphenyl ether, nonylphenol, glyphosate, pharmaceuticals) were detected, no concentrations were higher than those reported for the global average. However, there were constraints in the analytical capability to measure emerging contaminants in New Zealand.
The accumulation of cadmium and fluoride in New Zealand’s agricultural soils is another concern due to the continued use of phosphate fertilizers (Loganathan et al., 2003; NZ-MPI, 2019). The latest report prepared in 2014 for the Fertiliser Association of New Zealand and the Ministry for Primary Industries highlights that historical pollution by cadmium exists in the country. This is mainly associated to the intensive and long-term use of phosphate fertilisers in farmland has increased cadmium concentrations in soil. While the national average cadmium content in soil is 0.44 mg/kg, agricultural soils present up to 2.14 mg/kg. A number of soil in Waikato, Taranaki and Bay of Plenty regions presented cadmium concentrations above the national average (medians of 0.74 mg/kg, 0.71 mg/kg, and 0.54 mg/kg, respectively), mainly used for dairy farms and orchads (Cavanagh, 2014). Other recent studies corroborate similar cadmium concentrations in areas where phosphate fertilizers have been used (Salmanzadeh et al., 2016; Stafford et al., 2018; Taylor, Caldwell and Sneath, 2017).
Turnbull et al. (2019) reported that lead concentrations in urban soils in Dunedin, New Zealand, were higher than in many other cities around the world (median value 135.4 mg/kg) and were related to the historical anthropogenic contribution of lead inputs to soil primarily from leaded paints and vehicle fuels (Figure 15).
Pacific Island Countries (PICs) are made up three groupings: Polynesia (e.g. Tonga, Tokelau), Melanesia (e.g. Papua New Guinea, Fiji), and Micronesia (e.g. Federated States of Micronesia, Nauru, Kiribati). The most recent inventory of wastes and polluted sites in the PICs was undertaken in 2000 (Table 6). Understanding the current status of soil pollution is necessary in order to target research activities and management actions to mitigate potential adverse effects on human health and the environment. This is an important knowledge gap for the sub-region.
According to a report published by UNEP (2000), the major sources of contaminants from the main industries (breweries, sugar, edible oils, canned fish) in the region were sewage sludge and oils and grease in 1992. Fiji, Papua New Guinea, Solomon Islands and Vanuatu had a relatively high industrial contaminants load, reflecting their relatively large industrial activities. New Caledonia (a territory of France) is also a large enough PIC to have significant industrial activities but was not included in the UNEP study. Future studies of PICs should seek to include this and the other territories and dependencies in the Pacific.
Between 2013 and 2014, SPREP conducted an audit of waste oils in the PICs (SPREP, 2020c). Table 7 demonstrates the levels of waste oils found in each PIC that was audited. In most PICs there was about 50% recovery of waste oils, such as recycling in other processing plants. An issue identified in the recycling of used oil was the potential for low temperature combustion of oils and the subsequent release of emissions. In addition, the spilled oil from the storage and transportation was reported to cause soil contamination with hydrocarbons. Environmental regulatory authorities were often hindered by a shortage of monitoring equipment and lack of compliance inspectors.
Since the UNEP report of 2000 and the developments under SPREP, very few studies have been published on contaminants in PICs. A more recent study on the levels of lead, copper, zinc and iron in the sediments of Suva Harbor (Fiji) showed that they are 2 to 6 times higher than background levels (Maata and Singh, 2008; Park et al., 2013). High levels of mercury have also been detected. The authors expressed concerns about seafood consumption by the general public. The elevated concentrations detected in Suva Harbour were comparable to older studies available in neighbouring PICs. It is plausible that Papua New Guinea, Solomon Islands and Vanuatu continue to have high levels of these trace elements in harbour sediments.
The sources of trace elements in sediments vary in these largely coastal island states, with a relatively small ratio of land area to coastline length. In addition to diffuse sources, mining, industrial activities and emissions from road transport are known sources of these trace elements in larger PICs. A recent news report raised the serious concern about environmental pollution from EOL vehicles in these island countries (James, 2020). Although pollution of coastal water and surface water by trace elements and oil substances leached from these EOL vehicles has been identified as a major concern, the surface soils of the coastal belt have been significantly exposed to the stockpile and abandonment of EOL vehicles.
A study of a range of pesticides (including organochlorides) and flame retardants PBDE in sediments and shellfish, conducted in 2014 around Fiji Islands showed detectable levels but low concentrations, indicating no large scale coastal pollution from agricultural and industrial activities (Lal et al., 2014). These studies emphasized the need for source, fate, bioavailability, and transport studies to understand and manage land-based pollution. Park et al. (2013) recommended a thorough assessment of land-based waste management practices.
In addition, emerging contaminants whose concern has raised since 2000 should be considered in PICs as part of a new contaminant inventory. For example, in May 2009, at the fourth meeting of the conference of the Parties, additional POPs were added to the Stockholm Convention, including PFAS, which are commonly used for firefighting by the aviation industry worldwide.