Groundwater quality Management in China

Aizhong Ding, Lirong Cheng, Steve Thornton, Wei Huang, David Lerner

1College of Water Sciences, Beijing Normal University, China

2Department of Civil and Structural Engineering, University of Sheffield, UK

Abstract: Groundwater quality is of vital importance in groundwater safety especially for the purpose of water supply, its management becomes more and more necessary as groundwater contamination has threaten its safe use in China. The article analyzed the contamination sources of groundwater and impact of contamination on human health and water supply, the knowledge gaps were pointed and recommendations were made for groundwater quality management in China.

Keywords: groundwater quality； contamination； management； China

1 Introduction

Groundwater is one of the major sources for water supply in China, which covers 18.2% of the total water supply in 2011 reported by the Ministry of Water Resources of China. It provides drinking water for 70% of the total population and 95% of the rural population in the country. In many arid and semi-arid areas, groundwater is the only source of drinking water. Therefore, groundwater needs to be at good status in terms of availability and quality for the safety of water supply, however in many regions, groundwater is non-usable due to its contamination and poor quality. Many recent field investigations showed that groundwater is contaminated by halogenated hydrocarbons (Gao et al. 2012), nitrate (Ma et al. 2012； Zhang et al.2012), pesticides (Zhao & Wang 2012) and heavy metals (Zhang et al. 2012) in some regions of China. The contamination of groundwater has threatened local water supply and sustainability of water resources with high content of hazardous materials and not suitable for use as longer.

Groundwater pollution has become a common problem in urban areas, especially in big cities. A recent investigation reported that the groundwater quality status in more than half of the investigated cities are worsening. Groundwater pollution has developed from individual localized issues to large area problem. Shallow groundwater can no more be used for drinking purpose. Another investigation has shown that 64% of the investigated 118 cities where groundwater is regarded as the main water source suffered from heavy groundwater pollution, 33% suffered from light groundwater pollution. Only 3% still has relatively clean groundwater.

In Northeast China, groundwater is highly polluted in the heavy industry regions and oil production areas. In the Songhuajiang-Nenjiang plain, the main pollutants in groundwater include nitrate, ammonium and oil； while in the lower Liaohe plain, nitrate, ammonium, volatile phenol and oil are the main pollutants in the groundwater.

In the North China plain, groundwater quality has been deteriorating for many years due to the strong economic activities in this area.Groundwater is widely polluted in both urban and agriculture areas. The reported main pollutants in groundwater include nitrate, cyanides, iron,manganese and oil. In the mean time, the hardness and mineralization degree of groundwater in this area are significantly higher than the historical data.

In Northwest China, the groundwater is less polluted due to less intensified human activities.The main pollutant in the inland basins is nitrate,while in the middle reach of Yellow River and the loess plateau the main pollutants include nitrate,nitrite, Chromium and lead which are scattered as point or line source pollution around cities and industry/mining zones. In South China, the groundwater quality is in good condition in general with some heavily polluted areas. In the west part,the groundwater pollution is mainly found near residential areas with nitrite, ammonium, iron,manganese and volatile phenol as the main pollutants. In middle part, the main pollutants are nitrite, ammonium, mercury and arsenic. In the south part, the main pollutants are nitrate,ammonium, mercury, chromium and manganese.Groundwater is heavily polluted near the cities and industry and mining enterprises in this region. The shallow groundwater is widely polluted in the Yangtze River delta and the Pearl River delta.

Groundwater contamination is an urgent issue for China water management and water supply.How to protect and restore groundwater becomes the major task of environment and water management. Groundwater quality is mainly controlled by the geochemical, physical and biological processes occurring in the ground and human activities as well (Vrba & Zaporozec 1994).Since the industrial revolution, anthropogenic contaminants had been fed to groundwater bodies via multiple pathways and became a significant source of groundwater pollution. Most of the synthetic compounds are nondegradable and persistent in environment, and usually pose high harm to human health. With the advances in analytical techniques, it became possible to measure trace chemical constitutes in groundwater,the scientists is becoming focus on the impacts of groundwater contamination from groundwater hydrology (Keeley 1985).

The article reviewed the contamination sources to groundwater, impact of groundwater contamination and analyzed the knowledge gaps and recommendations for groundwater quality management in China.

2 Sources of groundwater contamination

2.1 Natural sources

In certain environment, some hazardous substances of natural origin may occur in groundwater in high concentrations harmful to health. The occurrence of natural hazardous substances in groundwater are closely related to the geological and hydrogeological environment of the groundwater catchment. According to China Geological Environmental Monitoring Institute,the main naturally occurring hazardous substances found in groundwater include As, F, Fe and Mn.

2.1 .1 Arsenic

Under favorable geological and redox conditions, arsenic may appear in groundwater in high concentrations which can cause chronic arsenic poisoning if used as drinking water.Arsenic can accumulate in human bodies and affect the lungs, skin, kidneys, and liver. There are 2 major mobilization mechanisms of As: (a) in oxidizing environment, arsenic rich mineral such as arsenopyrite can be oxidized and release arsenic to the environment； (b)in reducing environment,iron hydroxide may be reduced to ferrous iron causing the adsorbed arsenic release to water (Ding et al. 2007) . This is thought to be the main source of arsenic in groundwater in reducing condition. In the mean time, As5+ in arsenic bearing minerals can be transformed into As3+and enter the groundwater.

High arsenic content in groundwater is found in 8 provinces of China affecting 2.34 million people (Table 1) (Jin et al. 2003). Of which, more than 7,800 people are seriously poisoned. The most affected area is in Hanggin Banner of Inner Mongolia with the highest arsenic concentration of 1,800 ug/l in groundwater (drinking water standard for As was 50μg/l before 2007, 10μg/l after 2007).

Table 1 Epidemiological distribution of arsenic poison in China (adapted from Jin et al., 2003 )

2.1.2 Fluorine

Endemic fluorine poisoning is another problem associated with natural occurring hazardous substance in drinking water in China. People with long-term exposure to fluorine concentrations above safe level in drinking water can suffer chronic disability and even die (Zhu 2009). The affected population in China is estimated to be 50 millions, clustered mainly in the North China plain,Northeast China and Northwest China. In terms of the affected population and the ratio of the affected people to the total population of that area, North China plain is the highest in the country.

Fluorine can be found in the water leached from weathered fluorine bearing rocks and the leached fluorine gets concentrated in geographical depressions and basins in favorable conditions.When geothermal water is present, the indissolvable fluorite can be transformed into soluble fluoride and causing high concentrations of fluorine in groundwater. The combination of all or some of the following factors favors the concentration of fluorine in groundwater:geographic depressions, dry climate, evaporation exceeds precipitation, closed surface and groundwater basin, high content of fluorine bearing minerals in rock/sediments, very slow groundwater flow, alkaline and saline soil,groundwater of HCO--Cl--Na+or HCO--Na+-Ca2+type, close to hot spring(s).

2.1.3 Iron and manganese

High concentrations of iron and manganese often happen together in groundwater. High content of iron and manganese can cause clogging of wells and is harmful to boiler due to fouling.They normally affect only the color of drinking water. But very high concentration in water can be harmful to health as well. Over 44 millions population are affected by drinking water of high iron and/or manganese content.

The insoluble iron and manganese oxides in sediments can be reduced to form more soluble sulfides and carbonates by the decomposition products (e.g. H2S and CO2) of organics.

2.2 Anthropogenic impacts on groundwater quality

Nation wide investigations on groundwater quality have shown that the main causes of groundwater pollution are oil spill, waste water discharge, pipeline failure, excessive use of farm chemicals and dump of mining waste. The important contaminants are BTEX, PAHs,chlorinated solvents, ammonium, fertilizers and heavy metals. Typically they are highly toxic,weakly soluble and very persistent. Once released to water, they are easily sorbed on the particulates in water and on sediments. The sorbed contaminants may return to water under certain conditions.

2.2.1 Chemicals from industry

BTEX are major industry raw materials widely used in pharmacy, production of paint, and printing ink, leather manufacture, rubber processing and synthesizing resins. Improper use, storage and transport of the chemicals all contribute to the contamination of soil and groundwater. Oil spill and sewage irrigation are also the big contributors for BTEX found in groundwater. In the Yangtze river delta, the distribution of BTEX polluted shallow groundwater is nicely correlated with the industries present in the area.

PAHs are mainly from the burning of fossil fuel and wood, processing of oil and petrochemicals, oxygen-deficient combustion,incineration of waste, landfilling, food processing,traffic and road dust. The PAHs produced from human activities account for the vast majority of total PAHs in the environment. Oil spill is another contributor of PAHs in groundwater (Tan et al.2007).

2.2.2 Chemicals from agriculture

Organic chlorine pesticide is a widespread recalcitrant organic pollutant in water environment from agriculture activities in the 1950～1970s.Organophosphorus pesticide is currently the most used pesticide in agriculture.

The excessive use of fertilizers contributes in big part to groundwater pollution. High concentration of nitrate in groundwater is mainly from the application of nitrate fertilizers. Heavy metals commonly found in phosphorous fertilizers(Cd，Co，Cu，Pb，Ni) can cause soil and groundwater pollution when used in large quantities.

2.2.3 Contaminated land, sewage and sea water intrusion

Historically contaminated land from industry can be a big source of groundwater pollution if not properly treated. Leaking of sewage system is another important source of groundwater pollution in urbanized area. Groundwater quality in Jinan,for instance, was affected by heavily polluted river water which receives a big portion of untreated sewage water of the city. Groundwater quality in many coastal areas is affected by sea water intrusion due to improper development of groundwater resources. The total sea water intrusion area is estimated to be more than 1000 square kilometers distributed in Liaoning,Shangdong, Hebei, Jiangsu, Zhejiang and Guangdong provinces (Jiang et al. 2009).

3 Impacts of groundwater contamination

In the last few decades, groundwater quality in most part of country has deteriorated seriously.According to the Ministry of Water Resources and the Ministry of Health, 323 millions rural people are still suffering from unsafe drinking water which accounts for 34% of the total rural population. Ninety million people are affected by drinking water pollution. Endemic diseases associated with naturally occurring hazardous substances in groundwater are still big issues in many places.

With rapid development of urban areas, land use has undergone big changes. Due to incomplete documentation of contaminated land and lack of awareness of the associated risks, lots of the heavily polluted sites from the previous chemical plants have transformed into commercial or residential places without proper treatment. This poses big threat to the health of the people living in the environment.

In some cities, the groundwater pollution has become very serious that threatened the safe water supply. In Anhui province, 90% of the area next to the Huai river is polluted and can no more be used as drinking water. In Zibo, a large well field with production of 510,000 m3/d was polluted. In Beijing, the shallow groundwater is abandoned for drinking water supply because of the wide range of pollutants detected in it. In some arid areas, the contaminated groundwater is often used for irrigation due to the shortage of water resources.The increasing demand for good quality groundwater due to the development of economy and increasing living standards, is facing greater and greater challenges.

4 Knowledge gaps and recommendations

The existing laws and regulations related to groundwater quality protection in China include:The Environment Protection Law (1989), The Water Pollution Prevention Law(2008), The Water Law (2002), The Drinking Water Source Protection Area Pollution Prevention Regulations(1989), The Interim Measures of Water Pollutant Discharge Permit Management(1988). With the release of Technical Guidelines for Environmental Impact Assessment-Groundwater Environment(2008), the groundwater environment impact assessment has become normalized. With all these laws and regulations in place to protect groundwater quality, but many provisions are still a concept and principle, lack of practical operability. Groundwater quality protection plans are typically made and enforced on relatively small scales rather than catchment scale. A strategy of integrated catchment management of water resource is urgently needed in China.

Due to the fact that groundwater generally needs minimal treatment because of its good quality and it is easily accessible, the price of groundwater is typically much lower than other water sources. As a result, groundwater is seriously overpumped and wasted without recognizing that its renewal speed is very slow, especially for deep groundwater. Over exploitation not only depletes aquifers causing ground depression, but also affects the quality of groundwater. A more reasonable pricing mechanism of water is urgently needed to protect groundwater resource.

On top of the above-mentioned aspects, the public awareness of groundwater quality protection is also need to be raised.

Recognizing the knowledge gaps, the following suggestions are made:

National register or record of known contaminated sites for soil and groundwater,indicating the number, type of contamination and location in each case, to identify risks to groundwater and populations, plus focus remediation efforts and financial resources more cost-effectively

Regulations are needed to ensure groundwater has similar financial value (cost to consumer) as surface water supplies to reduce over-utilisation.This must reflect the true value of groundwater as a commodity for consumers and the need to preserve / manage existing resources more sustainably.

Greater communication is needed of the value of groundwater as a national resource for sustainable development and economic growth.Education of industry and general public is required to highlight the risks from human activity and individual, corporate and collective responsibility to reduce pollution and preserve resources.

Need to identify and develop / apply more sustainable remediation concepts (e.g.bioremediation) for these problems, due to nature of contamination (organics, access) and environmental impacts that may arise from conventional technologies (e.g. landfilling, pump& treat, incineration).

5 Future trends for groundwater quality management

Realizing the groundwater quality issues in China, the following trends for groundwater management can be recognized from world experiences:

(1) Catchment management

It has been increasingly accepted that groundwater should be included as a component in integrated management of catchments and issues affecting. Groundwater is not wastewater receptor,but functioning as part of greater ecosystem within the hydrological cycle. Groundwater quality management should be integrated into water resources management and environmental pollution management within catchments,groundwater system functions need to be delineated first, then management goals can be made by coupling water resource management and environmental pollution management.

(2) Public perception

Groundwater should be seen as a resource at risk by industry and the general population, with better understanding of the role of groundwater in the country's development. This is not likely to change in the near future, but it is the ultimate driving force in tackling groundwater quality issues.

(3) Urban regeneration and brownfield development

Recognizing the risks of former industrial land within major urban centres, more stringent regulations on contaminated land management will be enforced. Environmental impact assessment and remediation need to be done on more wide and regular basis before a brownfield is transformed into a commercial or residential area. Groundwater quality could be improved as a result.