Janne Salminen

Polychlorinated phenols and their metabolites in soil and earthworms of sawmill environment

Abstract Topsoil and earthworm samples collected from three Finnish sawmill environments were analysed for polychlorinated phenols, 2,3,4,6-tetrachloro- and pentachlorophenol, and their metabolites. Analyses were carried out by gas chromatography/mass spectrometry using a selected ion monitoring technique and by dual-channel gas chromatography using quartz capillary columns and two electron capture detectors. The total chlorophenol concentrations ranged from ca. 260 to 480 μg/g (dry weight) in soil and from ca. 140 to 3500 μg/g fat in earthworms. The most important metabolites in soil were chlorinated dihydroxy-benzenes (also at ppm level); only traces of chlorinated anisoles were detected in soil. 2,3,4,6-Tetrachloroanisole and pentachloroanisole were found at ppm level in fat of earthworms.

Bioaccumulation of organochlorine compounds in earthworms

Abstract Bioaccumulation of chlorophenolic wood preservatives 2,3,4,6-tetrachlorophenol (2346-TeCP) and pentachlorophenol (PeCP) and their metabolites in earthworms were studied in the laboratory, and by taking worm samples from the contaminated soil of a sawmill which was abandoned 28 yr ago. In two laboratory experiments 2346-TeCP (containing PeCP as impurity) was added into the soil, and samples were taken at certain intervals both from the soil and the earthworms ( Lumbricus rubellus in experiment 1 and Aporrectodea caliginosa tuberculata in experiment 2). Considerable amounts of chlorophenols were found in field samples. Soil concentrations ranged from 157 to 338 μg 2346-TeCP g −1 dry soil and from 103 to 140μg PeCP g −1 dry soil. Earthworm concentrations ranged from 270 to 2000 μg 2346-TeCP g −1 fat and from 130 to 1500μg PeCP g −1 fat, respectively. Earthworms also contained chlorinated anisoles (1–20 μg g −1 fat). On the other hand, chlorinated dihydroxybenzenes were not detected in earthworms, while these substances were present in the soil. Concentrations of chlorophenols were higher in A. caliginosa than in Lumbricus spp. In the pot experiments concentrations of chlorophenols in earthworms increased sharply during the experiments, and concentrations as high as 1800 μg g −1 fat were detected after some weeks incubation (in experiment 1, 61 μg chlorophenols g −1 dry soil, and in experiment 2, 154μg chlorophenols g −1 dry soil, was added). The earthworms had no influence on the concentrations of chlorophenols in the soil.

Effects of pentachlorophenol in forest soil: a microcosm experiment for testing ecosystem responses to anthropogenic stress

Changes in the structure and function of a soil decomposer community and growth of birch (Betula pendula) due to chemical contamination were studied in laboratory microcosms. Sodium pentachlorophenate (PCP) was added to the humus layer of a simulated forest soil at three nominal concentrations (0, 50 and 500 mg kg-1 dry mass). After two growing periods (48 weeks), there were more small soft-bodied mites, but less collembolans and microbial biomass, in the higher PCP concentration treatment than in the other treatments. Number of enchytraeids were significantly reduced and fungal-feeding nematodes became extinct in the soil with the higher PCP concentration. Soil respiration did not change due to PCP contamination. Diversity of soil fauna tended to decrease with increasing PCP concentration. Number of faunal taxa were not influenced by PCP. Mainly due to reduction of enchytraeids, total animal biomass was significantly lower in the higher PCP concentration treatment than in the other treatments. At week 8, leaching of nutrients was greatest in the higher PCP concentration treatment. At the end of the experiment no significant changes in soil pH and NHinf4sup+-N content of the soil were found. Birch growth and N concentration of the leaves were reduced with the higher PCP concentration. We assume that direct toxicity of PCP at the beginning of the experiment and changes in the decomposer community structure (mainly reduction of enchytracids and changes in microflora) due to PCP were responsible for the lowered primary production in the systems.

Effects of pentachlorophenol on soil organisms and decomposition in forest soil

1. In order to find a more reliable basis for ecotoxicological risk assessment, two microcosm experiments, one in the laboratory and another in the field (lysimeters), were performed using pentachlorophenol (PCP) as a model contaminant. PCP was applied at three (0, 50 and 500 μg g -1 dry soil in the laboratory experiment) or at two (0 and 50 μg g -1 in the lysimeters) concentrations in raw humus forest soil and its effects on soil organisms and decomposition processes were monitored. Soil fauna was manipulated at two levels in the laboratory experiment: simple and diverse communities. 2. PCP was strongly adsorbed onto the humus. 3. Microbes, nematodes, enchytraeids and predatory gamasid mites were sensitive to PCP in the laboratory experiment. 4. No significant faunal effects were observed on carbon and nutrient mineralization. At the highest PCP concentration carbon liberation (CO 2 -evolution) was lowered and NH 4 + -N was accumulated in the soil. PCP contamination indirectly affected soil pH and water content of the organic soil layer. 5. In the lysimeters, after 15 weeks there were fewer enchytraeids and prostigmatid mites in the soil contaminated with PCP, but no changes in nitrogen mobilization were observed. After 49 weeks, however, there was less NH 4 + -N in the contaminated soil, while no differences in faunal composition were found. 6. The results showed that, in comparison with single-species toxicity tests, more ecologically relevant microcosm experiments give important information about the behaviour of the decomposition system under contamination. This information, including also indirect impacts of chemicals, may be useful for the improvement of ecotoxicological risk assessment.

Regulation of decomposer community structure and decomposition processes in herbicide stressed humus soil

Abstract Regulation of soil decomposer community structure and ecosystem processes, such as nutrient cycling, under herbicide stress was studied in a microcosm experiment. For the experiment, coniferous forest soil was defaunated and put into the microcosms. In the microcosms two different food webs including microbes, nematodes, tardigrades and oribatid mites, either with or without predatory mesostigmatid mites, were reconstructed. Half of the microcosms were stressed with a herbicide (active ingredient was terbuthylazine). During the 57 weeks incubation community structure of decomposers and nitrogen mineralisation were studied at five destructive samplings and two water irrigations. Soil respiration was measured weekly starting at week 26. Mesostigmatid mites regulated densities of some prey species and hence they had an effect on the community structure of microbivores. A trophic cascade from predators to microbes took place both in unstressed and stressed soils: microbial activity decreased in the presence of predators. Predation effect was observed more clearly in the unstressed soil although predators maintained their populations longer in the herbicide stressed soil. Predators had no significant effects on N mineralisation while herbicide increased it. Oribatids were reduced by the herbicide at the later phase of the experiment. It can be concluded that decomposer food webs and decomposition in the soil can partly be top-down controlled. Due to a high degree of omnivory it was impossible to determine precisely the trophic structure of the food web. Herbicide contamination altered the community regulation and ecosystem processes via direct toxicity and by affecting trophic interactions. Although the application of food web analysis in risk assessment procedures has been proved to be problematic, there is a clear need for system level studies because of the chemical-induced indirect effects on the food webs.

Methylation products of chlorophenols, catechols and hydroquinones in soil and earthworms of sawmill environments

Abstract Soil samples and earthworms collected from one noncleaned and two cleaned sawmill environments were analysed for their content of chlorinated anisoles (methoxybenzenes), veratroles (1,2-dimethoxybenzenes) and 1,4-dimethoxybenzenes. 2,3,4,6-tetrachloroanisole and pentachloroanisole were observed in all soil samples studied, in maximum combined amount about 1.5 μg/g dry soil. Small amounts (ca. 1–110 ng/g dry mass) of 3,4,5-trichloroveratrole, tetrachloroveratrole and tetrachloro-1,4-dimethoxybenzene were found in the most polluted soil samples. Only 2,3,4,6-tetrachloroanisole and pentachloroanisole were found in earthworms, where concentrations of each were ca. 0.1–20 μg/g fat. In general, the concentration of pentachloroanisole was higher than that of 2,3,4,6-tetrachloroanisole in earthworms.

Decomposer communities in contaminated soil : Is altered community regulation a proper tool in ecological risk assessment of toxicants?

Effects of patchy soil contamination on decomposer organisms, their community regulation and nutrient mineralization were studied in a microcosm experiment. Coniferous forest soil was patchily contaminated with three concentrations of sodiumpentachlorophenate PCP (0, 50 and 500 mg PCP kg(-1) of dry soil). Abundance of microbes, enchytraeids, nematodes, small oribatids and predatory mites were reduced by the PCP. Direct toxicity of PCP and lowered microbial biomass seemed to affect animal community composition in the most contaminated patches. Some large oribatids which seemed to be tolerant to PCP increased their numbers in the most contaminated patches. Although predatory mites suffered from PCP, no altered predator-prey interactions were observed. At the beginning of the experiment more nutrients were released in the patches with highest PCP concentration and the nutrients accumulated in the soil. Soil decomposer food webs seemed to be mainly bottom-up controlled: PCP strongly affects microbes and hence caused changes in the community structure of soil animals and nutrient cycling. Hence top-down orientated ecological models on community regulation and food web dynamics seem to be unsuitable when assessing effects of pesticides on soil communities.

Responses of the soil decomposer community and decomposition processes to the combined stress of pentachlorophenol and acid precipitation

Abstract The combined effects of contamination by pentachlorophenol (PCP) and acid precipitation on soil decomposer communities and decomposition processes were studied. Intact soil cores were taken from a coniferous forest in central Finland, enclosed in plastic tube microcosms and dug into the ground. The total set of microcosms was divided in four treatments: (1) contamination with PCP, (2) PCP and two irrigations with strong acid solution, (3) PCP and five irrigations with weak acid solution, and (4) control: irrigations with deionized water. The applications began 8 weeks after initial burial and were completed over a further period of 9 weeks. The microcosms were sampled after 18, 51 and 59 weeks. Soil pH did not decrease consistently with acid deposition. PCP concentrations were not affected by acid deposition. All acid and/or PCP-treated soils contained more NH+4–N than the control soil at the first and second samplings, but there were no differences at the last sampling. There were more enchytraeids in the controls than in other treatments from the second sampling date onwards, that is, after the winter. Collembolan population density was not affected by the treatments while numbers of oribatid, prostigmatid and astigmatid mites were reduced in the stressed soils, but only on the first sampling date. Most of the observed effects on decomposers and nitrogen mineralization were attributable to PCP, but acid deposition may also have been involved through possible effects on the bioavailability of PCP. The imposed anthropogenic stresses, together with winter conditions, were detrimental for enchytraeids. By the end of the experiment decomposer communities together with mosses had mainly recovered.

Chloroanisoles in soils and earthworms

One important group of metabolites of chlorophenols in Finnish soils is their methylation products, i.e. chloroanisoles. Bioaccumulation of chloroanisoles into the biomass of earthworms was studied both in laboratory and by taking earthworm samples from contaminated soils. Concentrations of these compounds in the soils were also analysed. In the laboratory experiment, concentrations of 2,3,4,6-tetrachloroanisole (2346-TeCA) and pentachloroanisole (PeCA) were high in earthworms 1 week after introduction (approx. 50 μ/g fat). Later on, the concentrations decreased to a low level at a considerable rate, bcth in soil and in earthworms. The higher the concentration of chloroanisoles in the soil was, the higher was the microbial activity measured as production of carbon dioxide. Demethylation of chloroanisoles back to corresponding chlorophenols was observed. In the field samples taken from an area of a sawmill which had been closed nearly 30 years before, concentrations of TeCA and PeCA in the soil varied from 0.01 to 1 μg/g (dry mass). Chloroanisole concentrations in the tissues of earthworms varied from 0.04 to 0.24 μg/g fat. In Aporrectodea caliginosa tuberculata, which ingest large amounts of soil, higher concentrations were found than in Lumbricus species, which feed on leaf litter from the soil surface.