Urbanization
Rapid urbanization has taken place in China ever since the economic development and socioeconomic changes of the 1980s. Approximately 40% of the population now lives in cities, compared with ~20% in 1980. The current annual urbanization rate is ~1%, which means that ~13 million people move into cities every year. Urbanization has created huge pressures on the maintenance of agricultural land and production. In 2005, the net loss of arable land was 361,600 ha (~0.3% of the total arable land), of which 138,700 ha was used for construction. From 1998 to 2005, farmland decreased by 7.6 million ha, ~6.2% of the total arable land (3). The per capita area of cropland in China was only 0.93 ha in 2005, 40% of the world average (12). To achieve a higher production rate from the remaining, smaller area of cultivatable land, China has become the world’s largest consumer of fertilizers and the second largest of pesticides (13). Consequently, large amounts of cultivated land and farm produce have been contaminated, especially with residues of organochlorine and organophosphorus pesticides. Domestic waste increased significantly with urbanization. In 2005, domestic sewage amounted to 28.1 × 1010 metric tons, a 30% increase since 2000 (3). Because of the lack of proper treatment, the discharge of domestic waste has resulted in serious environmental problems in the air, soil, and water. Impacts of environmental problems The impacts of the aforementioned environmental problems are significant and multifaceted. They include damage to human health, social conflicts, and economic losses. Acid rain resulting from air pollution is prevalent in southern China. Chemically, the major anion in acid rain is SO4 2–, but recently the concentration of NO3 – has increased, which shows that the contribution of NOx is increasing. Acid rain leads to acidification of surface waters and soils, which can cause ecosystem dysfunction, including loss of fish populations and forest dieback (9, 14). In 2005, ~38% of Chinese cities and counties had annual average pH values <5.6. This indicates that they were likely affected by acid rain (3). The deposition of sulfur in some places is higher than what was reported from the Black Triangle in central Europe in the early 1980s (9). Approximately 60% of China’s population is rural, and nearly all rural residents use highly polluting biomass and coal for household cooking and heating. Indoor air pollution from use of solid fuel in China is responsible for ~420,000 premature deaths annually (15). In 2002, China introduced an indoor air quality standard (16), in which the maximum level of PM10 was set at 150 μg/m3. Although the standard is high compared with the World Health Organization guideline of 50 μg/m3, indoor air pollution is expected to improve with the implementation of the standard. Contaminated soil and water affect human health mainly through the food chain. In China,~7.3% of arable land is irrigated with sewage water, of which 20% has been polluted with heavy metals, such as Cd, As, Cr, and Pb (17). Symptoms of arsenic poisoning from upstream mining activities have emerged among the ~180,000 local inhabitants of seven counties within 6100 km2 in Hetao Area (18). The long-term mercury mining in Guizhou Province, southwestern China, has resulted in significant pollution of the local ecosystem (19). The concentrations of total mercury (THg) in rice grains from one mining area have reached 0.57 mg/kg (20). The SEPA tolerance limit for THg in foodstuffs is 0.02 mg/kg (21).gation of the Environmental Impact Assessment Law of China in 2002. Thus, a full-scale EIA mechanism safeguarding the environmental soundness of socioeconomic development has been established legally and practically. Initiatives for envi
Water shortage and contamination China is one of the 13 countries in the world with the most limited water resources. The available per capita volume of water is ~2200 m3, only 25% of the world average. In addition, water resources are distributed unevenly in China. About 44% of the population lives in the north but has access to only ~15% of the water resources. More than 60% of the 669 cities (of population >0.1 million) in China have problems with water shortages, and the situation in 110 of those cities is categorized as serious (1). In addition, >24 million rural people have insufficient drinking-water supplies (2). The water shortage will be exacerbated by serious pollution. More than 60% of China’s large lakes are eutrophic (3), and the water quality has declined in >50% of its rivers. The water quality at >50% of the monitored sections in five of China’s seven largest rivers (the Liaohe, Songhua, Haihe, Huaihe, and Yellow rivers) is considered Grade IV or worse in a five-class grading system (3, 4), indicating heavy pollution (Figure 1). The major concerns are ammonia nitrogen, biological oxygen demand (BOD5), permanganate index, and oils (3). The discharge of urban sewage and industrial wastewater is the main source of contamination in the rivers, as supported by the observation that >90% of the heavily polluted monitored sections are near large cities (3). The use efficiency of water is still low in China. In 2000, the use efficiencies of irrigation water (the water that reaches cultivated land and is available for plant growth divided by the total amount of water obtained from the water source) and industrial water (the proportion of reused water relative to the total amount of water acquired for industrial use) were 0.43 and 0.55, respectively. In contrast, the ratios in developed countries have reached 0.70 and 0.75–0.85, respectively (2). With ongoing development and urbanization, the gap between water supply and demand will become wider. Most eastward-flowing rivers drain into the coastal marine environment, and the water quality is getting worse with the inflow of polluted river water. As a result, incidents of red tides (harmful algal blooms) started to increase significantly in the 1980s and peaked with 119 episodes in 2003, covering a total affected area of ~1.5 × 104 km2 (3, 5). F I G U R E 1 Ranking the quality of China’s seven largest rivers According to the Environmental Quality Standard for Surface Water (4 ), China’s water bodies can be divided into five classes on the basis of >30 parameters, including pH, sulfate, chloride, nitrate, phosphorus, metals (Cu, Zn, Fe, Mn, Ca, Hg, As, Pb, etc.), BOD5, chemical oxygen demand, volatile phenol, and so on. The limitations of the parameters for each class were described in detail in the standard (4 ). Water of Grades I–III is suitable for drinking, Grade IV is for industrial and recreational use, and Grade V is for agricultural use. All data are from SEPA, 2006. Grades I–III Grades IV, V Inferior to Grade V Yellow River Yangtze River 76% 76% 13% 11% 25% 54% 32% 40% 19% 57% 24% 30% 30% 51% 17% 24% 22% 41% 34% 18% 6% Pearl River Huaihe River Haihe River Liaohe River Songhua River 7598 n Environmental Science & Technology / November 15, 2007 Air pollution Of the 522 cities monitored in 2005, 11% were considered heavily polluted and only 56% had air quality that met the State Environmental Protection Administration of China (SEPA) standard (3). The major air pollutants are particulate matter (PM), SO2, and nitrogen oxides (NOx). Currently, >40% of China’s cities are suffering from high levels of suspended particles (total concentrations of suspended particles >200 μg/m3, or PM10 >100 μg/m3) (3, 6). Ozone has recently aroused much attention because of its harmful impacts on agricultural production and human health. A study in Shanghai revealed that ozone levels are associated significantly with total and cardiovascular mortality, especially during cold seasons (7). High concentrations of ozone have caused crop losses in many regions of China. However, large uncertainty still exists in how to scale surface ozone distribution and crop impacts up to the national level, because of highly inadequate monitoring facilities (8). The main causes, characteristics, and future trends of air pollution in China are related to the energy sector (9, 10) as well as to industrial development, traffic, and urbanization. An estimated 70% of total smoke (aerosols), 90% of SO2, and 67% of NOx are released by burning coal (11). Meanwhile, the number of motor vehicles in China reached 36 million in 2003, compared with 6.2 million in 1990 (9). Thus, the ever-increasing number of vehicles has become an important contributor to the increasing air pollution. The energy infrastructure in China is not expected to change in the near future, and coal will remain the dominant energy source for at least the next several years. In addition, vehicle exhaust and urban activities will increase rapidly in the coming years. Therefore, the emissions of aerosols, SO2, and NOx are expected to continue to increase. For that reason, energy efficiency must be improved, and effective measures are needed to prevent further deterioration of air quality. Urbanization Rapid urbanization has taken place in China ever since the economic development and socioeconomic changes of the 1980s. Approximately 40% of the population now lives in cities, compared with ~20% in 1980. The current annual urbanization rate is ~1%, which means that ~13 million people move into cities every year. Urbanization has created huge pressures on the maintenance of agricultural land and production. In 2005, the net loss of arable land was 361,600 ha (~0.3% of the total arable land), of which 138,700 ha was used for construction. From 1998 to 2005, farmland decreased by 7.6 million ha, ~6.2% of the total arable land (3). The per capita area of cropland in China was only 0.93 ha in 2005, 40% of the world average (12). To achieve a higher production rate from the remaining, smaller area of cultivatable land, China has become the world’s largest consumer of fertilizers and the second largest of pesticides (13). Consequently, large amounts of cultivated land and farm produce have been contaminated, especially with residues of organochlorine and organophosphorus pesticides. Domestic waste increased significantly with urbanization. In 2005, domestic sewage amounted to 28.1 × 1010 metric tons, a 30% increase since 2000 (3). Because of the lack of proper treatment, the discharge of domestic waste has resulted in serious environmental problems in the air, soil, and water. Impacts of environmental problems The impacts of the aforementioned environmental problems are significant and multifaceted. They include damage to human health, social conflicts, and economic losses. Acid rain resulting from air pollution is prevalent in southern China. Chemically, the major anion in acid rain is SO4 2–, but recently the concentration of NO3 – has increased, which shows that the contribution of NOx is increasing. Acid rain leads to acidification of surface waters and soils, which can cause ecosystem dysfunction, including loss of fish populations and forest dieback (9, 14). In 2005, ~38% of Chinese cities and counties had annual average pH values <5.6. This indicates that they were likely affected by acid rain (3). The deposition of sulfur in some places is higher than what was reported from the Black Triangle in central Europe in the early 1980s (9). Approximately 60% of China’s population is rural, and nearly all rural residents use highly polluting biomass and coal for household cooking and heating. Indoor air pollution from use of solid fuel in China is responsible for ~420,000 premature deaths annually (15). In 2002, China introduced an indoor air quality standard (16), in which the maximum level of PM10 was set at 150 μg/m3. Although the standard is high compared with the World Health Org