Partitioning and mineralization of [¹⁴C]lindane in a laboratory sediment–water system

Abstract

Abstract-To develop a guideline for a simulation test for aerobic degradability in surface water, the fate of [ 14 C]lindane (␥-hexachlorocyclohexane) was studied in laboratory systems using natural river water and sediments. No sterilized controls were set up. Thus, measured data reflect the sum of biotic and abiotic processes. Tests were carried out under various experimental conditions to investigate which of these would affect the feasibility of the test, the fate of lindane, the physicochemical state, and the biological activity within the sediment-water systems. Lindane (37.7 nmol) was applied either to the water (3 L) or the sediment (0.33 L). Sediments remained nonreducing, and there was no serious decline of nutrients nor enzymatic activities. In one experiment up to 14.1% of the applied lindane was mineralized to 14 CO 2 within 50 d and in a second one up to 35.3%. At day 91 of the latter experiment up to 46.8% were found to have been mineralized. Among the experimental factors tested, the method of lindane application and temperature predominantly affected mineralization. The type of aeration and the semicontinuous addition of organic nutrients were of minor importance. Sediments and water collected at the same site but at different times showed variation in carbon content as well as in esterase and dehydrogenase activities. Nevertheless, these parameters could not be correlated with mineralization of lindane during the tests. Between 1 and 9% of the radioactivity volatilized during the tests. At the end, 23 to 66% were bound to sediments and 15 to 45% of the total activity was neither extractable by water nor by cyclohexane.

Freshwater sediment pesticide biodegradation potential as an ecological indicator of microbial recovery following a decrease in chronic pesticide exposure: A case study with the herbicide diuron

“…In summer 2007, a similar gradual increase in diuron mineralization potential along the Morcille river was reported, with higher diuron-mineralizing ability observed in the downstream section of the river for both periphytic biofilm and sediment communities (Pesce et al, 2009). It is noteworthy that studies on the potential of natural freshwater sediments to degrade synthetic pesticides are scarce ( Kalsch et al, 1998, Larsen et al, 2000, Toräng et al, 2003and Trinh et al, 2012, but there is now convincing evidence that the capacity of microbial sediment communities to biodegrade these contaminants can increase after an in situ longterm pre-exposure to these compounds ( Toräng et al, 2003 andTrinh et al, 2012). In the present study, the estimation of diuron-mineralizing ability in the sediments of the Morcille river differentiated the reference (upstream) from the two (intermediate and downstream) exposed stations.…”

Biodegradation of hexachlorocyclohexane (HCH) by microorganisms

“…The Clostridium rectum strain that dechlorinated Lindane did so at an optimum temperature of 37 to 38°C (Ohisa & Yamaguchi 1978). Biodegradation appears to slow down at temperatures as high as 40°C (Manonmani et al 2000) or as low as 5°C (Kalsch et al 1998). The optimum temperature for degradation may vary in field environments depending on the bacterial population.…”

“…Under aerobic conditions, a slight enhancement of degradation was observed as a result of treatment with glutamic acid. In an aerobic sediment-water system spiked with 14 C-c-HCH, application of nettle leaf extract to provide additional dissolved organic carbon did not significantly affect mineralization (Kalsch et al 1998).…”

“…These data demonstrate how different soil types can affect redox potential under the same treatment conditions, and how this and differences in pH and organic matter might contribute to differences in HCH removal rates. Kalsch et al (1998) used partitioning and sorption of a 14 C-c-HCH spike in columns of sediment and water to demonstrate the impact that particle size distribution in the sediment might have on HCH degradation. More rapid mineralization of the radiolabelled pesticide to 14 CO 2 was observed in coarse than in fine sediments.…”

A farewell to Dr Thomas Knacker (* 29.04.1951 – † 30.10.2011): scientific contributions and personal memories

“…He was the coordinator of two large EU projects, Terrestrial Model Ecosystems and ERAPharm (2004)(2005)(2006)(2007). Although Thomas was formally responsible for aquatic ecotoxicology at ECT GmbH, his research interests were much broader [4][5][6][7]. His influence was probably most visible in the environmental risk assessment of chemicals [8][9][10], such as their regulation in the marine environment (OSPAR process), the effects of endocrine disruptors [11,12] or their testing in higher-tier studies, especially Terrestrial Model Ecosystems (TMEs) [13][14][15].…”