Fate and biological effects of pentachlorophenol in outdoor ponds

Abstract

Various laboratory methods and mathematical models are being developed to assess the hazards of chemicals to aquatic environments. Although the approach is generally accepted, many of the methods and models have not been validated by comparison with field observations. In this study we compared predictions of the fate and biological effects of a reference compound, pentachlorophenol (PCP), with observations in experimental outdoor ponds. PCP was repeatedly applied to the subsurface water of three ponds with the aim of maintaining an average concentration of 50 to 100 μg/L in the water for a period of 30 d. At this dosage level chronic toxicity to some organisms was expected. Evaporation, sorption, hydrolysis, biodegradation and indirect phototransformation of PCP were expected to be of minor importance under the environmental conditions encountered in the ponds. The partition coefficient of PCP between water and wet sediment was predicted to be near unity and the dominant loss process to be direct phototransformation. The rate of this process was calculated using the SOLAR mathematical model. Data used for this calculation were the light absorption spectrum of PCP, the quantum yield for the light‐activated reaction, depth and light attenuation of pond water, season and latitude. After correcting for cloud cover, the calculated rate constant was 0.23 to 0.46 d−1. In good agreement with the calculations, the observed rate of loss was 0.15 to 0.34 d−1, and there was no evidence of accumulation in sediment. The results of chronic toxicity tests with various species of fish, two species of snail and the planktonic crustacean Daphnia magna Straus were consistent with field observations. Chronic toxicity to filamentous algae (Chara sp. and Enteromorpha sp.) was observed in the field, and their death and decay were responsible for depression of dissolved oxygen concentrations and fish deaths. Direct effects on filamentous algae and the indirect effects caused by their death and decay could not be predicted in the absence of relevant laboratory data.

Seasonal Variation in Plankton Community Responses of Mesocosms Dosed with Pentachlorophenol

“…No treatment-related changes were seen at the lower concentration of 100 lg/l PCP. Similarly, no significant treatment effects were apparent on zooplankton in ponds dosed continuously for 30 days to maintain nominal concentrations of 50-100 lg/l PCP (Crossland and Wolfe, 1985). Therefore, the concentrations causing effects in the current study were considerably lower than those reported previously.…”

The scientific basis of bioassays

“…To a certain degree, some checks have been made (e.g., Mount et al, 1984, Crossland & Wolff, 1985, Geckler etal., 1976. To a certain degree, some checks have been made (e.g., Mount et al, 1984, Crossland & Wolff, 1985, Geckler etal., 1976.…”

Endocrine disruption in aquatic pulmonate molluscs: few evidences, many challenges

“…Field investigations only refer to experimental aquatic ecosystems where snail populations were artificially introduced and exposed to pesticides. Evidence that L. stagnalis populations were affected by prolonged exposure to pentachlorophenol (PCP) in outdoor ponds was reported by Crossland and Wolff (1985). Two-phase exposure to PCP (ca.…”

“…However, there were no differences in the number of eggs collected, and the number of non-viable eggs was abnormally high in only one out of the three treated ponds. The authors considered that the study was inconclusive, but deduced from their observations that concentrations of PCP in the ponds were near to threshold values for toxicity to L. stagnalis populations (Crossland and Wolff 1985). The effects of HCB, another chlorinated pesticide, have been studied in populations of L. palustris maintained in outdoor ponds treated at the rates of 0.5, 1.25, and 5 lg/l.…”