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To double bottom or not
Marine Pollution Bulletin
used successfully for over a year at Devonport Royal Dockyards where around 60% of the RNs vessels are refitted. TBT is known to cause serious problems in the marine environment and, although still used as an antifoulant on ocean-going vessels, its use on pleasure craft and by the fish-farming industry was banned in 1987 (see Mar. Pollut. Bull. 18, 146). When a vessel is dry docked ar, d has its hull cleaned by high pressure water hoses large volumes of water become contaminated with organotin compounds which then enter rivers, estuaries and the sea. Although TBT breaks down in the presence of UV light, contaminated washings tend to sink and breakdown is therefore very slow. The award-winning scheme is aimed at preventing contaminated water finding its way into drains by controlled storage and disposal of the washings. This has been achieved by firstly reducing the amount of water used in the wash-down process from around 20 00030 000 gallons per ship to 6000-8000 gallons. Diversion channels are then used to separate contaminated washings from clean water. The contaminated washings are channelled into a culvert from which they are transported by road-tanker to a shallow settling pond where chemical decomposition can occur. The system relies on simple and well-proven techniques which could easily be applied to less developed countries.
Tackling the Most Heavily Polluted Bay in China Jinzhou Bay with an area of 120 kln 2 is a semi-enclosed bay located in the Bohai Sea (N. China). At present, fishery resources, salterns, and tourist spots have been destroyed by oil and heavy metals. Local residents' health has been affected very seriously and this has caused attention both from the state and public to be directed to the pollution problem. As a result the Institute of Marine Environmental Protection was asked by State Oceanic Administration to take the initial step in harnessing the pollution catastrophe. Pollution in this bay has been occurring for thirty years. The main pollution sources are the Jinxi chemical plant, five oil refinery plants and a zinc smelter plant which account for 99% of the total pollutants released to the bay. Oil levels in the water column and in the sediment have reached as high as 0.2 mg 1-1 and 5000 mg 1-1, respectively. Oil tars can be found everywhere on the beach. Even more toxic are the levels of heavy metals which are the highest in China. The concentrations of Hg, Cd, Pb, Zn, Cu in the water column are 1.0 ~g 1-1, 10 ~tgl -t, 10 ~tg 1-1, 400 p.g 1-1, and 7 ~tg 1-1 respectively; concentration of Cd in sediment is 50 mg kg-~ and Cu, Pb, and Zn are all over 1000 mg kg-1. This is the first case of marine pollution treatment in Chinese history. As far as the specific location and morphology of the bay are concerned, several proposals have been raised by specialists. The main points are: 362
1. Identification of the marine environmental target. According to the present pollution situation, current regime, and future development of the bay, three environmental quality control areas should be classified (Table 1). Then each area can be managed in accordance with different environmental criteria and functions. TABLE 1 Maximum permitted concentrations of toxic pollutants in the classified sea areas. Maximum permitted concentrations (mg 1-~) 1st Class 2nd Class 3rd Class Hg 0.0005 0.0010 0.0010 Cd 0.005 0.010 0.0010 Pb 0.05 0.10 0.10 Total Cr 0.10 0.50 0.50 As 0.05 0.10 0.10 Cu 0.01 0.10 0.10 Zn 0.10 1.00 1.00 Se 0.01 0.02 0.03 Oil 0.05 0.10 0.50 Cyanides 0.02 0.10 0.50 Phenols 0.005 0.010 0.050 Inorganic Nitrogen 0.10 0.20 0.30 Inorganic Phosphates 0.015 0.03 0.045 Organochloride Pesticides 0.001 0.02 0.040 Pollutant
2. Control of the amount of pollutants discharged into the sea. The most important step in dealing with the rehabilitation of the bay is to control pollution sources. The present investigations have revealed that mercury concentrations both in seawater and sediment are near or over the danger point. Therefore levels have to be cut down in order to prevent the occurrence of environmental deterioration and COD (Chemical Oxygen Demand) should also be reduced accordingly. 3. Reform of the industrial structure in this region. 4. Pretreatment of oil and organic-waste water. Waste waters which contain oil, cyanides and phenols should be processed to the requirements of first class treatment. By doing so, 95%.of oil and 30% of COD can be removed. 5. Transformation of polluted environments and elimination of secondary pollution sources--(a) mercury levels in the surrounding environment of the Jinxi chemical plant are very high. This must be given priority when tackling the overall mercury pollution problem; (b) the waste water pond in the Jinxi chemical plant is the main source for regional groundwater pollution. Therefore the waste sludge must be removed or incinerated; (c) the level of mercury in the sediments of Wuli River is very high with an estimated total load of 90 tons. At present, part of this mercury load has been transformed to methylmercury. The sediments must be dredged out and cleaned up. 6. Regional stringent marine environmental regulations and rules must be drawn up as soon as possible according to the national marine environmental protection laws.
FAN ZHIJIE
Loss of Dangerous Cargoes The recent loss of toxic pesticides from the stricken cargo ship M.V. Perintis (see Mar. Pollut. Bull 20, 201 ;
used successfully for over a year at Devonport Royal Dockyards where around 60% of the RNs vessels are refitted. TBT is known to cause serious problems in the marine environment and, although still used as an antifoulant on ocean-going vessels, its use on pleasure craft and by the fish-farming industry was banned in 1987 (see Mar. Pollut. Bull. 18, 146). When a vessel is dry docked ar, d has its hull cleaned by high pressure water hoses large volumes of water become contaminated with organotin compounds which then enter rivers, estuaries and the sea. Although TBT breaks down in the presence of UV light, contaminated washings tend to sink and breakdown is therefore very slow. The award-winning scheme is aimed at preventing contaminated water finding its way into drains by controlled storage and disposal of the washings. This has been achieved by firstly reducing the amount of water used in the wash-down process from around 20 00030 000 gallons per ship to 6000-8000 gallons. Diversion channels are then used to separate contaminated washings from clean water. The contaminated washings are channelled into a culvert from which they are transported by road-tanker to a shallow settling pond where chemical decomposition can occur. The system relies on simple and well-proven techniques which could easily be applied to less developed countries.
Tackling the Most Heavily Polluted Bay in China Jinzhou Bay with an area of 120 kln 2 is a semi-enclosed bay located in the Bohai Sea (N. China). At present, fishery resources, salterns, and tourist spots have been destroyed by oil and heavy metals. Local residents' health has been affected very seriously and this has caused attention both from the state and public to be directed to the pollution problem. As a result the Institute of Marine Environmental Protection was asked by State Oceanic Administration to take the initial step in harnessing the pollution catastrophe. Pollution in this bay has been occurring for thirty years. The main pollution sources are the Jinxi chemical plant, five oil refinery plants and a zinc smelter plant which account for 99% of the total pollutants released to the bay. Oil levels in the water column and in the sediment have reached as high as 0.2 mg 1-1 and 5000 mg 1-1, respectively. Oil tars can be found everywhere on the beach. Even more toxic are the levels of heavy metals which are the highest in China. The concentrations of Hg, Cd, Pb, Zn, Cu in the water column are 1.0 ~g 1-1, 10 ~tgl -t, 10 ~tg 1-1, 400 p.g 1-1, and 7 ~tg 1-1 respectively; concentration of Cd in sediment is 50 mg kg-~ and Cu, Pb, and Zn are all over 1000 mg kg-1. This is the first case of marine pollution treatment in Chinese history. As far as the specific location and morphology of the bay are concerned, several proposals have been raised by specialists. The main points are: 362
1. Identification of the marine environmental target. According to the present pollution situation, current regime, and future development of the bay, three environmental quality control areas should be classified (Table 1). Then each area can be managed in accordance with different environmental criteria and functions. TABLE 1 Maximum permitted concentrations of toxic pollutants in the classified sea areas. Maximum permitted concentrations (mg 1-~) 1st Class 2nd Class 3rd Class Hg 0.0005 0.0010 0.0010 Cd 0.005 0.010 0.0010 Pb 0.05 0.10 0.10 Total Cr 0.10 0.50 0.50 As 0.05 0.10 0.10 Cu 0.01 0.10 0.10 Zn 0.10 1.00 1.00 Se 0.01 0.02 0.03 Oil 0.05 0.10 0.50 Cyanides 0.02 0.10 0.50 Phenols 0.005 0.010 0.050 Inorganic Nitrogen 0.10 0.20 0.30 Inorganic Phosphates 0.015 0.03 0.045 Organochloride Pesticides 0.001 0.02 0.040 Pollutant
2. Control of the amount of pollutants discharged into the sea. The most important step in dealing with the rehabilitation of the bay is to control pollution sources. The present investigations have revealed that mercury concentrations both in seawater and sediment are near or over the danger point. Therefore levels have to be cut down in order to prevent the occurrence of environmental deterioration and COD (Chemical Oxygen Demand) should also be reduced accordingly. 3. Reform of the industrial structure in this region. 4. Pretreatment of oil and organic-waste water. Waste waters which contain oil, cyanides and phenols should be processed to the requirements of first class treatment. By doing so, 95%.of oil and 30% of COD can be removed. 5. Transformation of polluted environments and elimination of secondary pollution sources--(a) mercury levels in the surrounding environment of the Jinxi chemical plant are very high. This must be given priority when tackling the overall mercury pollution problem; (b) the waste water pond in the Jinxi chemical plant is the main source for regional groundwater pollution. Therefore the waste sludge must be removed or incinerated; (c) the level of mercury in the sediments of Wuli River is very high with an estimated total load of 90 tons. At present, part of this mercury load has been transformed to methylmercury. The sediments must be dredged out and cleaned up. 6. Regional stringent marine environmental regulations and rules must be drawn up as soon as possible according to the national marine environmental protection laws.
FAN ZHIJIE
Loss of Dangerous Cargoes The recent loss of toxic pesticides from the stricken cargo ship M.V. Perintis (see Mar. Pollut. Bull 20, 201 ;