Water Pollution Events on Lake Biwa

Transcription

1 Water Pollution Events on Lake Biwa It is said that the first water pollution event in Japan was Ashio Copper Mine Poisoning. But this event was not responded as a water quality management issue because of lack of relevant knowledge and counter measures in our society. In those days, Japan had been experiencing three main pollution events. One was Ashio Copper Mine Poisoning, two was Hitachi Mine Poisoning and three was Besshi Copper Mine Poisoning. First one was water pollution event and other two were air pollution events. The needs for environmental management had gradually been recognized with economic growth since the early 1950s. Responding such needs, Japanese Government enacted the two laws on water quality conservation. These two laws, however, had not handled all water areas in Japan except very limited water areas such as main industrial areas. And also they had no strict penalty provisions. In 1960s, taking the opportunity of Minamata Disease Event and Yokkaichi Asthma Event, there were many pollution events unveiled at all over the country. In order to solve such pollution events which had been changed to important social problems, the Government decided to enact relevant laws for prevention of various pollution events in The accident caused by pollution in Shiga Prefecture appeared mainly on Lake Biwa because of the geographical reason. This slide shows three dimension picture of Lake Biwa water shed. 1

2 As you can know by this figure, almost all of precipitation and used water in Shiga Prefectural area flow down into the lake. And most typical and severe accident occurred in Lake Biwa was mass decease of fish and shellfish in early 1960s. The cause of this mass decease was occurred by herbicide used as weeding agent on paddy fields around the lake. In those days, the strong poisonous herbicide, named PCP (Penta Chloro-Phenol), was used to be spread in late May each year for preventing weeds on paddy fields. Just this season, in Japan, is rainy season, so, in every year, spread herbicide often over-flew into the lake from paddy fields, and damaged to fisheries, especially to shellfish fisheries. This figure shows the annual change of shellfish amount caught by commercial fishing in Lake Biwa. The rapid decrease portion pointed by red arrow is the result of mass decease caused by PCP. As the counter measure to this accident, the Government of Shiga Prefecture firstly decided to prohibit use of PCP around the lake. The prohibited area is within red line on this figure. This red line consists with national roads, Route 1, Route 8 and Route 161. However, the structures of roads can't be barriers of 2

3 dissolved herbicide to the lake. Therefore, the government of Japan prohibited use and product of PCP in However, in almost all of the world countries, PCP has been used as pesticide, especially in developed countries, it has been used as insecticide for timbers. The second big accident was occurred in It was health damage such as eczema on which we decided to be occurred by antimony included in effluent discharged from a refinement factory and penetrated into ground water. Antimony is used as one of materials for electrode of battery, alloy of printing type and semiconductor so on. Besides, the factory had buried refined sludge in the factory's ground, and for a long time, antimony had oozed out from the sludge. Then, through a river along the factory, it reached to the lake. The Government of Shiga Prefecture immediately executed health examination to residents around the factory, and the same time, ordered the factory to re-bury sludge to a concrete pit. The fund for construction of a concrete pit was loaned by the Government of Shiga Prefecture without interest. And then, the Government of Shiga Prefecture set up the regulation on antimony. Now, antimony is regulated only in Shiga Prefectural area in Japan. 3

4 The third accident was water pollution caused by PCB included in effluence discharged from an electric condenser production factory in The cause of this accident was penetration of PCB from buried waste. The factory had buried condemned products in the factory's ground for a long time, and by corrosion, PCB enclosed into electric condensers had oozed out. Then, through a stream along the factory, PCB had flowed out into the lake, and polluted lake sediments and fish around the stream mouth. The Government of Shiga Prefecture immediately executed health examination to residents around the factory, and ordered the factory to remove polluted soil around the factory and re-bury polluted soil and condemned electric condensers to concrete pits. The polluted areas are now continuously monitored and regulated on land use. PCP and PCB include Dioxins as unintentionally produced chemicals. Dioxins are hard decomposition chemicals and in sediment of water areas, they remain almost permanently. This figure shows Dioxin Concentration accumulated in sediments of water areas in Japan. As you know from this figure, sediments of water areas in our country are extensively contaminated by Dioxins. The origins of such contamination are those mixed in PCP or PCB as impurities because Dioxins are very near chemicals of PCP or PCB. And another origin of 4

5 accumulated Dioxins is Domestic Waste Incineration. These contaminated states by Dioxins in Japan show close connection with two big problems in this Century, food problem and waste problem. The fourth big accident was ground-water pollution caused by chromiumⅥ. This accident was occurred by a bicycle-ring product factory. In early spring in 1976, the ground-water pollution caused by chromiumⅥ was discovered at a house-well located near by the factory. Color of ground-water in a well was suddenly changed to yellow. The owner of the well immediately corresponded that phenomenon to the Health Center of Shiga Prefecture. As the result of survey of a lot of wells around the polluted house-well, the source of the pollutant was found. The cause of chromiumⅥ effluence was oozed through cracked floor in plating process house of the factory. The Government of Shiga Prefecture immediately ordered the factory to take the same measures as the other two cases, and at the same time, ordered the factory to pump up polluted ground-water from several wells around the factory and treat them. 5

6 The treatment work for polluted ground-water is still continued. 6