pH-Dependent uranium toxicity to freshwater hydra

doi:10.1016/0048-9697(92)90388-9

Science of The Total Environment

Volume 125, 7 September 1992, Pages 159-173

https://doi.org/10.1016/0048-9697(92)90388-9 Get rights and content

Abstract

A research program was initiated to characterise the major toxicants in water from Retention Pond 2 (RP2) at Ranger uranium mine. RP2 water was bioassayed using local hydra species, with water from Magela Creek used as a control and diluent (pH 6.1–6.7, conductivity 12–20 μS/cm). The bioassay had survival and population growth after 4–6 days as endpoints. Uranium was identified as the major toxicant in RP2 water, and further studies were carried out to assess its toxicity. At pH 8.5, in the presence of bicarbonate, RP2 water containing uranium at concentrations up to 3900 ppb, and uranium at 1000 ppb added to Magela Creek water, did not affect survival or population growth. However, RP2 water made to 32% with diluent resulting in a pH of 8.0, and uranium concentrations ≥ 200 ppb in Magela Creek water held at a normal pH of 6.5, did affect survival and population growth. In the absence of uranium in Magela Creek water, the hydra population growth or survival after 6 days was not affected by pH 5.0–8.0 and 5.0–8.5, respectively. pH was adjusted by adding acetic acid or sodium bicarbonate which also increased the conductivity. Nevertheless, an increase in the conductivity > 400 μS/cm affected the population number only after 6 days. This pH-specific effect of uranium toxicity is discussed in relation to the uranyl carbonate complexes of uranium formed in solution.

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Citation Excerpt :
Although this is an unusual endpoint, it has good potential for ecological relevance because it is probably related to feed intake and hence growth and reproduction. The next series of papers (Trapp, 1986; Hyne et al., 1992a,b; Bywater et al., 1991; Poston et al., 1984; Barata et al., 1999) all reported effect concentrations that graded from 0.15 to 0.9 mg U L−1, with no distinct groupings of effect concentrations. This is a typical and expected outcome for a summary of ecotoxicology results, because it reflects the fact that there is a continuum of effect concentrations over a series of the many possible organisms and endpoints.
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- •
  terrestrial plants—250 mg U kg⁻¹ dry soil;
- •
  other soil biota—100 mg U kg⁻¹ dry soil;
- •
  freshwater plants—0.005 mg U L⁻¹ water;
- •
  freshwater invertebrates—0.005 mg U L⁻¹ water;
- •
  freshwater benthos—100 mg U kg⁻¹ dry sediment;
- •
  freshwater fish at water hardnesses of:
  –
  <10 mg CaCO₃ L⁻¹ (very soft water)—0.4 mg U L⁻¹ water;
  –
  10–100 mg CaCO₃ L⁻¹ (soft water)—2.8 mg U L⁻¹ water; and
  –
  >100 mg CaCO₃ L⁻¹ (hard water)—23 mg U L⁻¹ water; or
  –
  as a function of hardness—0.26 (hardness as mg CaCO₃ L⁻¹)
- •
  mammals—0.1 mg U kg⁻¹ body weight d⁻¹.
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pH-Dependent uranium toxicity to freshwater hydra

Abstract

Tissue Cell

Water Res.

Nucl. Tracks Radiat. Measmt

Comp. Biochem. Physiol.

Geochim. Cosmochim Acta

Toxicol. Appl. Pharmacol.

Aquat. Toxicol.

W. Smith. Aquat. Toxicol.