Organic halogen, heavy metals and biological activities in pristine and pulp mill recipient lake sediments

Abstract

In order to create a basis for prognosing future intrinsic remediation potential of past pollution by pulping industry, we analyzed biochemical activities and levels of pollution in sediments dated with 210Pb and 137Cs. A small pristine forest lake and a pulp mill recipient area of a large oligotrophic Lake Saimaa were test sites. Sediment concentration of EOX ranged from 40 to 130 μg Cl (g d.w.)−1 in the pristine lake and from 770 to 4700 μg Cl (g d.w.)−1 in the pulp mill recipient area and the C:Cl (w/w) ratio of sediment organic matter ranged from 2000 to 5100 and 42 to 230, respectively. The organic matter in 10 to 20 years old pulp mill recipient sediment was mainly of waste water origin. The activity gradients of β-glucosidase, butyrate-esterase, methane oxidation potential and endogenous respiration from surface to deeper layers were less steep in polluted than in pristine sediment. Methane oxidation potential was 120 μmol CH4d−1 (g C)−1 at the sediment surface of pristine lake sediment and 26 μmol CH4d−1 (g C)−1 at the polluted site, endogenous respiration rates of the surface sediment were 670 and 310 μmol CO2 d−1 (g C)−1, respectively. In the most polluted layer we found a depressed potential for methane oxidation, inhibition of phosphatase and butyrate-lipase activities and moderately increased induction ratio of β-galactosidase to phosphatase in the SOS-Chromotest strain E. coli PQ 37. The results suggest that at the concentrations observed these effects in the sediment were not due to heavy metals.