Recent Heavy Metal Concentrations in Watarase Basin Around Ashio Mine
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Journal of Health Science, 52(4) 465–468 (2006) 465 Recent Heavy Metal Key words —–— Ashio mine, heavy metal, copper, ar- senic Concentrations in Watarase Basin around Ashio Mine INTRODUCTION Kimihide Ohmichi,*, a Yoshiaki Seno,b Atsuko Takahashi,c Kohichi Kojima,c Pollution in the Watarase River caused by min- Hiroshi Miyamoto,d Masayoshi Ohmichi,e eral wastewater containing high levels of copper Yasuhiko Matsuki,a and Kazuhiko Machidab discharged during the development of the Ashio Copper Mine has drawn attention as one of the most a Japan Food Hygiene Association, 2–6–1 Jingumae, Shibuyaku, well-known environmental pollution problems in Tokyo 150–0001, Japan, bLaboratory of Preventive Medicine, Japan, and has been called the “Starting line of en- Faculty of Human Sciences, Waseda University, 2–579–15 1) Mikajima, Tokorozawa, Saitama 359–1192, Japan, cHatano vironmental pollution problems in Japan.” A cop- Research Institute, Food and Drug Safety Center, 729–5 Ochiai, per vein was found there in 1610, and especially Hatano, Kanagawa 257–8523, Japan, dChiba City Institute of since 1868, when Japan opened its country, mining Health and Environment, 1–3–9, Saiwaicho, Mihamaku, Chiba accelerated to support the rapid industrial develop- 261–0001, Japan, and eChiba City Social Welfare Administra- ment of Japan to catch up with industrialized West- tive Office, 1208–8 Chibadera, Chuoku, Chiba 260–0844, Ja- ern countries. In the late 19th century, dead fish in pan the river, which was contaminated with the water (Received April 6, 2006; Accepted April 17, 2006; discharged from the refinery, were observed. This Published online April 19, 2006) drew our attention as the first sign of a series of di- Pollution in the Watarase River caused by min- sastrous impacts. Around 1894, the latest refining eral wastewater containing high levels of copper dis- method was introduced, and the valleys around the charged during the development of the Ashio Copper refineries were filled with sulfur oxide gas exhausted Mine is one of the most well-known environmental from the refurbished refinery. The results were empty pollution problems in Japan, and has been called the valleys without any trace of life. Then, Kozai pointed “Starting line of environmental pollution problems in out this pollution issue and found high copper lev- Japan.” In this study, we conducted follow-up investi- els in farmland soil in the area.2) gations on the conditions of pollution in the Watarase Poisonous metals, including copper and arsenic, River since 1991, and measured the heavy-metal lev- were discovered in the waters of the Watarase River els in water in other rivers near the Watarase River when the amount of water had increased due to heavy and in soils around them. In addition, we compared rains. The Ashio refinery was surrounded by 14 very the results in this study with previous results, i.e. pol- large slag-pile accumulation basins and these are a lution conditions in the Watarase River, other rivers constant menace to the natural river system, for any and soils. Six points in upstream sites of the Watarase one of them might collapse into the river if there were chosen for sampling. Six samples from river wa- were heavy rains or an earthquake.1) ter, five samples from soils around the respective points, Mining operations at the Ashio Mine were aban- and three samples from tap water distributed there doned in February 1973, but the copper refinery were collected for the analysis. Heavy metal levels in business, which apparently caused heavy metal con- rivers and soils around the Ashio Copper Mine were significantly lower than the environmental standards tamination, was not discontinued until 1988. Thus, 3) for them. When compared with our previous investi- there is no possibility of new pollution. After the gations, the levels of polluting heavy metals around termination of refining operations at the Ashio Mine, the closed refinery at the Ashio Mine were gradually we conducted a series of investigations on the heavy but clearly reduced. In conclusion, the environment metal levels in rivers around the Ashio Mine begin- around the Watarase River has been steadily improved ning in 1991, for the purpose of determining pollut- so that safety in the living environment is assured. ants. In our previous investigations4–7) for the rivers around the Ashio Mine, a slight degree of pollution *To whom correspondence should be addressed: Japan Food by heavy metals had already been confirmed. In this Hygiene Association, 2–6–1 Jingumae, Shibuyaku, Tokyo 150– study, we conducted a follow-up investigation to con- 0001, Japan. Tel.: +81-3-3403-2112; Fax; +81-3-3403-2384; E- firm the degree of improvement of environmental mail: [email protected] circumstances around the basin of the Watarase River 466 Vol. 52 (2006) Fig. 1. Map of Ashio Area with Sampling Sites in comparing with our previous data. Therefore, we spectrometry (ICP, using the absolute calibration focused on measuring the levels of several kinds of method) and ICP-mass spectrometry (ICP-MS, us- heavy metals in the river water and soils sampled ing the internal standard method) for metals, where around the Watarase River, and compared them to the measurement conditions were optimized for each the environmental regulation standard in Japan. metal. Ashio is a small town located about 150 km north of Tokyo. The Watarase River runs down from the mountains in the Ashio area and flows into the Kanto RESULTS AND DISCUSSION Plain, which includes the main source of tap water for human activities in Kanto area. This is also an The concentrations of elements found in water important reason for researching the current status samples and soil are shown in Tables 1 and 2. As for of the Ashio area. the six samples from river water, the copper level, levels of heavy metals (arsenic, cadmium, lead, hexavalent chromium, mercury, selenium and bo- MATERIALS AND METHODS ron) regulated under Japanese environmental stan- dards by the Japanese Basic Environment Law, as In this study, six points in upstream sites of the well as nickel and antimony are shown in Table 1. Watarase River [A: Upstream of the Ashio Dam, B: In the case of soils, none of the levels of heavy-met- Around the closed refinery, C: Around the Ashio als (cadmium, lead, hexavalent chromium, arsenic, Town Office, D: The Souri area at the Kusaki Dam, total mercury, alkyl mercury, selenium and boron) E: Under the Takatsudo Bridge in Omama Town, regulated under the Soil Contamination Countermea- and F: Around the Mikouchi River (tributary of the sures Law exceeded the environmental standards for Watarase River)] were chosen for sampling. Sam- soils. Therefore, the copper and arsenic levels in pling site is showed in Fig. 1. On May 4, 2005, six particular are shown in Table 2. All the samples from samples from river water, five samples from soils tap water conformed the quality standards for heavy around the respective points, and three samples from metals in tap water under the Water Works Law. In tap water distributed there were collected for the this study, heavy metal levels in rivers and soils analysis. Each sample was analyzed according to the around the Ashio Copper Mine were significantly Japanese Industrial Standards and the Notification lower than the environmental standards for them. of Ministry of Health, Labour and Welfare, Japan. The copper levels in the area around the closed In the analysis, heavy metal levels were simulta- refinery and the downstream areas were higher than neously measured by inductively-coupled plasma those in the upstream area of the sampling points No. 4 467 Table 1. The Concentrations of Elements Found in Water at Each Sampling Point A–F (g/l) element A B C D E F MRLaµ copper 0.3 6.1 1.6 1.6 1.5 0.9 — arsenic 2.9 3.8 3.9 1.8 1.5 1.4 10 cadmium 0.02 0.34 0.04 0.04 0.07 < 0.02 10 < < < < lead 0.1 < 0.1 0.1 0.1 0.1 0.1 10 < < < < < hexavalent chromium < 0.5 0.5 0.5 0.5 0.5 0.5 50 < < < < < total- mercury < 0.02 0.02 0.02 0.02 0.02 0.02 0.5 < selenium < 0.2 0.2 0.3 0.4 0.3 0.2 10 boron 3.3 4.3 12.7 6.7 20.9 3.6 1000 nickel 0.8 1.1 0.5 0.7 0.5 0.9 — antimony 0.13 0.16 0.28 0.15 0.17 0.09 — a) Maximum Residue Limit; Japanese environmental regulated standards in river water by the Japanese basic environment law. Table 2. The Concentrations of Elements Found in Soil at Each Sampling Point A–F (mg/kg) element A B C D E F MRLaµ copper 0.02 0.45 0.44 not measured 0.02 0.01 125 mg/kg in farmland < < arsenic 0.001 < 0.001 0.012 not measured 0.001 0.001 15 mg/kg in farmland a) Maximum Residue Limit; Japanese soil standards by the Japanese soil contamination countermeasures law. Fig. 2. Annual Changes of Copper Concentration in River Water at Each Sampling Point A–F (Table 1). Residual copper was detected in the water in all the areas were detectable but lower than samples from the areas around the refinery and the the environmental standards, and the same result was downstream areas, suggesting the actual conditions obtained from soils. However, the arsenic level in of pollution there. Results for soils indicated that water around the closed Ashio Copper Mine was the copper level around the refinery was the highest approximately three times higher than that around when compared with upstream and downstream ar- the Mikouchi River, a tributary of the Watarase River.