Air Quality Criteria for Lead Volume II of II - (NEPIS)(EPA) - US ...

Nostoc muscorum exposed to 20,000 µg Pb/L experienced the greatest reduction in carbon
fixation at 0.5 h of exposure: 62% compared to controls. Inhibition of carbon fixation in the test
group was less pronounced after 1 and 2 h of exposure: 29 and 13% of controls (Rai and
Raizada, 1989). Lead in combination with nickel or chromium had synergistic effects to carbon
fixation. Lead and nickel concentrations of 20,000 and 1000 µg/L, respectively, resulted in 0.5,
1, and 2 h carbon fixation rates reduced by 93, 92, and 91%, respectively, compared to controls
(Rai and Raizada, 1989). Lead with chromium at concentrations of 20,000 µg/L resulted in 0.5,
1, and 2 h carbon fixation rates reduced by 65, 58, and 50%, respectively, compared to controls.
Nutrients such as nitrogen, phosphate, sodium acetate, sodium carbonate, and citric acid
have been shown to protect against the toxic effects of Pb to algae (Jampani, 1988). Nitrogen
compounds (ammonium chloride, potassium nitrate, sodium nitrate, sodium nitrite) protected
Synechococcus aeruginosus from a lethal Pb-nitrate dose of 200,000 µg/L (Jampani, 1988). Two
phosphates (K2HPO4 and Na2HPO4) were found to improve Synechococcus aeruginosus survival
from 0 to 72% at 200,000 µg/L of Pb-nitrate (Jampani, 1988).
Compared to controls, protein content was reduced by 54.2 and 51.9% in aquatic plants
Vallisneria spiralis and Hydrilla verticillata, respectively, exposed to Pb for 7 days at
20,720 µg/L (Gupta and Chandra, 1994). Decreased soluble protein content has been observed
in Scenedesmus obliquus exposed to Pb-nitrate or Pb-acetate at concentrations greater than
30,000 µg/L, and in L. gibba at concentrations greater than 200,000 µg/L (Adam and
Abdel-Basset, 1990; Miranda and Ilangovan, 1996). Lemna gibba also showed increased loss of
soluble starch at concentrations >200,000 µg/L (Miranda and Ilangovan, 1996). Under the
conditions described previously (Gupta and Chandra, 1994), EC50 values for chlorophyll content
were 14,504 and 18,648 µg/L for Vallisneria spiralis and Hydrilla verticillata, respectively
(Gupta and Chandra, 1994). Effects to chlorophyll a content have been observed in
Scenedesmus obliquus at Pb-nitrate and Pb-acetate concentrations >30,000 µg/L (Adam and
Abdel-Basset, 1990).
Summary of Toxic Effects Observed in Single-Species Bioassays
Algae and aquatic plants have a wide range in sensitivity to the effects of Pb in water.
Both groups of primary producers experience EC50 values for growth inhibition between
approximately 1000 and >100,000 µg/L (Jampani, 1988; Gaur et al., 1994; Bilgrami and Kumar,
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