故紙再生におけるPCB, PCTによる環境汚染 (I) : 故紙再生工場周辺の底質汚染の状況

Abstract

故紙再生を通してのPCB, PCTによる環境汚染の状況を把握するために, 1つの事例として, 大津市東部に位置する一板紙工場を対象とし, 同工場の排水の影響を受ける琵琶湖の底質, 湖水および工場排水の汚染の実態を調査した。得られた結果は, 1. 底質中のPCB, PCT濃度は新排水路 (1970年以降) およびその周辺で高い値を示し, 排水路口からの距離とともに減少する傾向が認められた。また, PCBは1970年まで使用されていた旧排水口付近ではとくに高い濃度を示したのに対して, PCTは新排水路中で最も高い濃度レベルにあり, 両者の汚染のピークの時期にはずれがあったと思われる。2. 底質中のPCB濃度, PCT濃度, I, L. (強熱減量) の3者の間には, それぞれ明らかな正の相関が認められ, 工場排水中のPCB, PCTは, その大部分が繊維カスなどの浮遊物に吸着されているものと思われる。3. 底質中のPCBは, 高濃度汚染地点のものでは, KC-300 (カネクロール-300) に類似したガスクロマトグラフパターンを示すが, 濃度が低くなるにつれて低塩素数のものの割合が減少する。これは水への溶出, 水中からの蒸発による低塩素部分の選択的消失によるものと考えられる。

PCBs and PCTs contaminations of bottom deposits, surface waters and drain waters were investigated at the area in Lake Biwa being influenced by the drain water from a paper board factory on the east area of Ohtsu City, as a case study in order to obtain informations about the environmental pollution by PCBs and PCTs resulting from reclaiming waste paper. Results obtained are as follows: 1. PCBs and PCTs concentrations in bottom deposits were observed to be high in the new drainage canal (after 1970) and around it, and to be lower at the further region from the outlet of the canal. The highest concentration level in bottom deposits for PCBs was found out at the surrounding of outlet of former drain (used until 1970), but for PCTs in the new drainage canal. That seems to indicate that the peak times of the pollution by PCBs differed from that by PCTs. 2. Obvious correlations were observed between PCBs concentration and ignition loss (I. L.), between PCTs concentration and I. L., and between PCBs and PCTs concentration in bottom deposits. Therefore it is thought that most parts of PCBs and PCTs in the drain water from the waste paper reclaiming factory were adsorbed by suspending substances such as fine pulp fibers. 3. PCBs in bottom deposits at the highly contaminated region abound with low chlorinated biphenyls, so thier gass chromatograms show similar pattern to that of Kanechor-300. However, the lower the PCBs concentration in bottom deposits becomes, namely the further from the source of contamination, the lower the ratio of low chlorinated biphenyls to total PCBs in bottom deposits becomes. That seems to result from preferential diminution of low chlorinated biphenyls that is due to thier preferential elution into the water and volatilization into the atmosphere from the water surface.