Evaluation of ecological disturbance and intrinsic bioremediation potential of pulp mill-contaminated lake sediment using key enzymes as probes.

A rapid protocol was developed to measure 10 different enzymic activities from a large number of 1-cm-sliced freshly collected lake sediments. Layers heavily polluted by organic halogens (4900 mg Cl kg(-1)) revealed severe depression of phosphatase, sulfatase, leucine-aminopeptidase, chitinase, acetate esterase and butyrate esterase activities as compared to layers above and below the most polluted zone. alpha-Glucosidase, beta-glucosidase, beta-xylosidase and palmitate esterase were less affected. Methane oxidation potential was dramatically depressed in the polluted strata whereas tetrachloromethane dehalogenating activity was observed in the polluted sediment only. The sediment layers formed after the chlorine discharges into the lake had diminished to 1/10, and showed restoration of the activities close to those observed in non-recipient sediment, in spite of the persisting presence of >1000 mg of organic chlorine (kg dry wt)(-1). We conclude that certain enzymic activities involved in breakdown or oxidation of organic matter in the sediments are useful probes for assessing the degree of ecological damage and its potential for restoration in recipient lakes of industrial discharges.

Sediment accumulation of organic halogens in pristine forest lakes: Tracking of a single defined discharge of pulp bleaching wastewater.

Sediment accumulation of organic halogen was studied in two forest lakes, one pristine and one which received 30 m(3) of biologically purified bleaching wastewater from a kraft pulp mill in 1979 equivalent to ca. 2 kg of adsorbable organic halogen (AOX). Lake sediments were dated with(210)Pb,(134)Cs and(137)Cs and the annual deposition rates of organic halogens and organic matter were calculated. Organic bound halogen contents of the sediment aged 150 years was 180 microg Cl g(-1) d.w. in both lakes. The concentration of organic bound halogen at the topmost 6 cm of the sediments (less than 20-years-old) ranged from 45 to 80 microg Cl g(-1) d.w. This suggests that solvent extractable halogen had enriched in the older sediment layers. The deposition of extractable organic halogen (EOX) in the lakes in 1950's was 4 to 5 mg Cl m(-2) a(-1). Since then, the deposition of EOX doubled in both lakes. The deposition of organic matter increased concomitantly from 50 g m(-2) a(-1) to 110 g m(-2) a(-1) in Lake Mustalampi and from 35 g m(-2) a(-1) to 62 g m(-2) a(-1) in Lake Pyylampi suggesting that the increase in the deposition of organic halogen followed the increase in the deposition of organic matter. Of the 2 kg of organic halogen discharged into the lake, 5% or less was detected in the sediment in tetrahydrofuran extractable form 15 years later.