Part of China's more than 3-million-square-kilometre marine environment is suffering from pollution due to land-based activities, an investigation report released in 2005 showed.
The report said that about 24 per cent of offshore seawater quality was bad, while 67 per cent of offshore seawater witnessed an improvement last year and was tested as being of good quality according to the national seawater quality standard.
Among China's four offshore marine areas, the East China Sea had the worst seawater, while the water quality of the Yellow Sea and South China Sea was slightly better. The seawater in Bohai Bay showed signs of deterioration.
And among all the coastal provinces, autonomous regions and municipalities, Shanghai and Zhejiang Province in East China had bad-quality seawater along their coasts. Hainan, Guangxi, Shandong and Guangdong had relatively better seawater.
Compared with the situation in 2004, the investigation found that generally China's offshore seawater quality had seen some improvement.
The report showed that in 2005 inorganic nitrogen and active phosphate were the main pollutants in offshore seawater.
Excluding the two main sources of pollution, in some parts of sea there were excessive levels of COD (chemical oxygen demand), dissolved oxygen, oil pollutants, lead, copper and nonionic ammonia.
In all of the four offshore sea areas, inorganic nitrogen and active phosphate were found. And in the other three seas, except the Yellow Sea, there was lead content beyond the standard. All offshore seawater contained oil pollutants, especially in the Yellow Sea, where oil pollutants were 8 per cent higher than the national standard.
In 2005, 82 red tides occurred in more than 27,000 square kilometres of offshore area in China, which were generally caused by greatly increased amounts of algae. Most large-scale red tides took place in the marine areas along Zhejiang Province in East China, the Yangtze River estuary, Bohai Bay in Northeast China and Hangzhou Bay in East China.
Although there was a 15 per cent reduction in the number of occurrences compared with 2004, the red tide areas and affected areas caused by harmful algae increased dramatically.
In 2005, red tides caused China a direct economic loss of about 69 million yuan (US$8.6 million).
Marine accidents were another cause for marine environmental pollution. In 2005, there were 115 accidents in China's offshore areas. Among the accidents, there were three serious accidents each leading to 50 tons of oil being spilt.
Major land-based activities, which polluted the marine environment, included:
Economic and social development in coastal cities and towns.
In 2005, nearly 32 billion tons of waste water from land-based activities, accounting for 60 per cent of the country's total sewage, was discharged into the sea.
In the waste water, there were 9.5 million tons of COD, 500,000 tons of ammonia and nitrogen, 30,000 tons of phosphate, 4 million tons of suspended materials, 80,000 tons of BOD (biological oxygen demand), 120,000 tons of oil pollutants, 20,000 tons of heavy metals, 800 tons of cyanide and 70,000 tons of other pollutants.
Most of the waste water discharged into the sea came from daily life and industries in coastal urban areas. The 2005 statistics showed that more than 222 million people live along the sea. They released about 11.6 billion tons of waste water in 2005. The remainder of sewage into the sea came from inland cities.
An investigation carried out in 2004 showed that along China's coast, there were 643 large waste water discharge outlets into the sea, among which, 285 were set for industrial pollution, 151 for domestic sewage, 87 for urban comprehensive sewage and 120 for sewage ditches.
Agriculture Production Activities
China has an arable land area of 130 million hectares with the application of 46-million- ton fertilizers. Among them, 22 million tons were nitrogen fertilizers, 7 million tons phosphorus fertilizers, 5 million potassium fertilizers and 12 million compound fertilizers.
Major impacts of agriculture production activities on the environment are mainly the non-point pollution resulting from such factors as field runoff like the loss of fertilizers and pesticides, water and soil erosion, domestic sewage and garbage in rural areas and the contamination by livestock and fowl farming.
The generation of agricultural pollutants has a close relationship with precipitation. Nitrogen, phosphorus, pesticides and other organic and non-organic substance enter rivers, lakes and seas through runoff or seepage during the precipitation period. In addition, the nitrogen- and phosphorus-containing leachate from the scattered domestic garbage piles and animal dung and urine flow into waters during the wet season, leading to water pollution.
The impacts of agriculture production activities also include the pollution of sea aquaculture. The main pollution sources come from the organic pollutants such as the excrement of the aquatic fish, shrimp and crabs, residue bait and shell excrement.
Marine transportation
Pollution from marine transportation mainly came from ships, shipyards and marine accidents.
Ships released oil pollutants, toxic liquid, consumer sewage and waste.
And currently in China there are more than 700 shipyards, which accommodate not only the demands of maintenance and repairs of all kinds of domestic ships, but also those of about 1,000 foreign ships.
In addition, there are about 200 factories dismantling retired ships with an annual import of 1.7 million tons of scrapped steel ships.
Most of the ship-related pollutions came from dismantling, offshore petroleum production platforms and floating oil storage ships.
Oil spills in the sea by marine accidents is another source of marine pollution. From 1976 to 2000, such accidents occurred every 3.5 days. During the period, there were 53 serious accidents each with oil spills of more than 50 tons. The total spill was nearly 30,000 tons.
Although China keeps strengthening the management and supervision of marine accidents, they are still happening frequently.
Marine dumping and offshore oilfield operations
In 2005, China had 98 marine dumping places, of which, 78 were in use, dumping materials of more than 192 million cubic metres.
And there were 39 offshore oil fields, releasing more than 90 million tons of sewage containing oil.
Land resource development in coastal zones
As the important buffer zone between land and sea, as well as a purification zone for pollution from land to sea, the unsustainable development of coastal zones will directly lead to the deterioration of the ecosystem, thus destroying the marine environment.