Pentachlorophenol toxicity to amphipods and fathead minnows at different test pH values

Abstract

Juvenile amphipods (Gammarus pseudolimnaeus and Crangonyx pseudogracilis) and fathead minnows (Pimephales promelas) were exposed to pentachlorophenol (PCP) at pH values of 6.5, 7.5, 8.0 and 8.5 for 96 h, and early life stages of fathead minnows were exposed for 32 d at the same pH values to determine the relationship between test pH and the acute and chronic toxicity of PCP. Residue analyses were performed on fathead minnows after 32 d to determine the relationship between test pH and PCP bioaccumulation. Technical‐grade PCP (88% active ingredient; Dowicide EC7) was used as the toxicant source. Acute exposures with all three species showed that PCP toxicity was decreased with increased test pH. The slopes of this relationship were similar for the amphipods, but were different from that observed for fathead minnows. Early life stage exposures of fathead minnows showed that chronic PCP toxicity and bioaccumulation were similarly decreased when pH values were increased. The decrease in chronic PCP toxicity appeared to be due to the reduction in PCP accumulation as a direct result of the increased ionization of PCP at higher pH values, indicating that the ionized form was less toxic per unit concentration than was the un‐ionized form. However, these studies suggest that chronic as well as acute toxicity may be caused by both forms of PCP when significant concentrations are present in solution.

Ten Years of Practical Experience with the Dreissena-Monitor, a Biological Early Warning System for Continuous Water Quality Monitoring

“…For PCP, the pH is probably the most important factor, because with increasing pH, PCP is more and more ionised, and the ionised form of PCP penetrates less effectively through biological membranes. For example, the LC 50 )[96 h] of PCP for the amphipod Gammarus pseudolimnaeus increased from 0.092 mg/l at pH 6.5 to 0.79 mg/l at pH 8.5, and for fathead minnow (Pimephales prometas) from 0.095 mg/l at pH 6.5 to 0.38 mg/l at pH 8.5 (Spehar et al, 1985). Results of Borcherding & Jantz (1997) demonstrated clearly that even the behaviour of the mussels on a spike of PCP is closely related to pH, and this within 30 min.…”

The influence of the dietary carbohydrate: lipid ratio on the chronic toxicity of sodium pentachlorophenate to rainbow trout (Salmo gairdneri Richardson)

“…Although the highest PCP body burden found in our study approached the lethal burdens of 92/zg/g for goldfish (Carassius auratus; Kobayashi and Kishino 1980) and 75 p.g/g for fathead minnows (Pimephales promelas; Spehar et al 1985), no significant mortality occurred. Storage or partitioning of much of the additional PCP away from sites of activity in fish reared on the LC diet is the most likely explanation for the poor dose-response relationship observed.…”

The effects of temperature, pH, and sediment on the fate and toxicity of 1‐naphthol to the midge larvae Chironomus riparius

“…In addition, 1-naphthol was more toxic at pH 8 than at pH 4 and 6 at both moderate and low temperatures (Table 1). The formation of potentially toxic dihydroxy naphthalenes from the photodegradation of 1-naphthol at an alkaline pH, as well as the presence of the ionized species, 1-naphthoxide, coutd contribute to the high toxicity of 1-naphthol at pH 8 [5,6,43,44]. Further experimentation is needed to quantify the amount of quiñones and naphthoxide present in the system at pH 8 and to determine their toxicity to the midge.…”

“…Ionizable toxic compounds have been reported to exhibit reduced toxicity to aquatic organisms at increasing pH [5,6,41]. This reduced toxicity is attributed to the slower penetration of the ionized species across cell membranes [42].…”

“…Hazard assessments of these compounds are complicated by formation of toxic metabolites from the parent compounds [2] and by the fact that the toxicity of many pesticides has been shown to be altered by changes in environmental factors such as temperature and pH [3][4][5][6][7]. In addition, sorption to dissolved organic carbon (DOC), sediment or suspended material can affect the movement and half-life of a compound, thereby altering its bioavailability to aquatic species [8][9][10][11][12][13].…”