Water / Soil / Ground Environment

Conservation of Soil Environment

The soil environment plays an important role in the circulation of substances and maintenance of ecosystem. It performs functions such as water purification and the production of food and wood. Therefore, it shall be conserved properly.

1. Soil Pollution Control Measures for Agricultural Land

In 1968, after it had become known that the "Itai-Itai disease" in the Jinzu River Basin area was a case of chronic cadmium poisoning, social attention was again drawn to the soil pollution problem of agricultural land. Finally, in 1970, the Agricultural Land Soil Pollution Prevention Law was enacted and remedial projects employing methods such as clean soil dressing were carried out. As of 1997, remediation projects for 76% of the total polluted land area (7,140 ha) had been completed.

2. Urban-type Soil Pollution Control Measures

In recent years, the number of incidents of so-called "urban-type" (non-agricultural) soil pollution has increased rapidly. The most common soil contaminants are organic chlorides such as trichloroethylene.

In 1975, a large quantity of soil contaminated with hexavalent chromium was found in part of Tokyo and it became a serious social issue. Since then, the number of so-called "urban-type" (non-agricultural) soil pollution cases discovered has been rapidly increasing throughout Japan. The increase was mainly due to accelerated urban redevelopment of former factory sites and the implementation of groundwater quality monitoring activities required by the Water Pollution Control Law. Presently, the major soil polluters are the chemical and electroplating industries, and the major contaminants are lead, hexavalent chromium, and trichloroethylene. The Environmental Quality Standards (EQSs) for soil pollution were issued in August 1991 to deal with these problems. With substances added in February 1994, the EQSs now regulate 25 substances. The Guidelines for Investigation and Countermeasures for Soil and Groundwater Pollution were established in November 1994 to ensure smooth implementation of surveys and countermeasures based on the EQSs and Evaluation Standards Relevant to Soil and Groundwater. Administrative guidance is issued to polluters to urge them to clean up polluted soil voluntarily using these guidelines.

System for Implementing Agricultural Land Soil Pollution Control Measures

Environmental Quality Standards for Soil Pollution

SubstanceTarget level of soil quality examined
through leaching test and content test
cadmium 0.01 mg/l in sample solution and less than 0.4mg/kg in rice for agricultural land
cyanide not detectable in sample solution
organic phosphorus not detectable in sample solution
lead 0.01 mg/l or less in sample solution
chromium(VI) 0.05 mg/l or less in sample solution
arsenic 0.01 mg/l or less in sample solution, and less than 15mg/kg in soil for agricultural land (paddy field only)
total mercury 0.0005 mg/l or less in sample solution
alkyl mercury not detectable in sample solution
PCBs not detectable in sample solution
copper less than 125 mg/kg in soil for agricultural land (paddy field only)
dichloromethane 0.02 mg/l or less in sample solution
carbon tetrachloride 0.002 mg/l or less in sample solution
1,2-dichloroethane 0.004 mg/l or less in sample solution
1,1-dichloroethylene 0.02 mg/l or less in sample solution
cis-1,2-dichloroethylene 0.04 mg/l or less in sample solution
1,1,1-trichloroethane 1 mg/l or less in sample solution
1,1,2-trichloroethane 0.006 mg/l or less in sample solution
trichloroethylene 0.03 mg/l or less in sample solution
tetrachloroethylene 0.01 mg/l or less in sample solution
1,3-dichloropropene 0.002 mg/l or less in sample solution
thiram 0.006 mg/l or less in sample solution
simazine 0.003 mg/l or less in sample solution
thiobencarb 0.02 mg/l or less in sample solution
benzene 0.01 mg/l or less in sample solution
selenium 0.01 mg/l or less in sample solution

The above standards are not applicable to :
1) Places where natural toxic substances exist such as the vicinities of mineral veins
2) Places designated for storage of toxic materials such as waste disposal sites

Progress in Identifying and Rehabilitating Sites [Number/(area, ha)] that Exceeded the EQSs under the Agricultural Land Soil Pollution Policy Plan. Data in 31 Oct. 1997.

Specific harmful substance(1)Breakdown(5)(6)(7)
(2)(3)(4)
cadmium 92
(6,610)
57
(6,110)
34
(320)
18
(180)
57
(6,030)
57
(4,810)
41
(3,640)
copper 37
(1,430)
13
(1,250)
16
(60)
8
(120)
13
(1,250)
13
(1,200)
12
(1,140)
arsenic 14
(390)
7
(160)
2
(90)
6
(140)
7
(160)
7
(160)
5
(80)
total
(Approx. area, ha)
129
(7,140)
66
(6,260)
49
(460)
31
(420)
66
(6,180)
66
(4,950)
48
(3,720)
  • (1)Sites exceeding EQS
  • (2)Sites designated for cleanup
  • (3)Cleanup sites for which independent prefectural projects, etc have been completed
  • (4)Cleanup sites being surveyed
  • (5)Sites designated for cleanup for which remediation in already planned
  • (6)Sites for which projects have been completed
  • (7)Cleaned sites which have been delisted

[Notes]

  1. Differences in the vertical columns between the total number of areas and their totals at the bottom are due to areas polluted by multiple substances. Horizontal discrepancies between the total number of areas under breakdown and that under (1) are due to the designation of divided areas.
  2. The sources of (1) are results of detailed surveys, etc. implemented until 1996.
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