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

observed in Selenastrum capricornutum 7 exposed to lead (Pb 2+ ) at 207.2 µg/L and a Q/V (flux of
air [Q] divided by volume of the culture [V]) of 4.7 Η 10 !3 sec !1 for 9 days (Simòes Gonçalves
et al., 1991). The Q/V is a measure of culture growth where an increase in the Q/V ratio
indicates growth. The pigment concentration per cell decreased with exposure to Pb, so while
the algae cells were larger, they were less healthy (Simòes Gonçalves et al., 1991). Growth rates
were not reported, making comparison with other studies difficult.
High Pb concentrations were required to elicit effects in Nostoc muscorum and
Scenedesmus aeruginosus (Jampani, 1988; Rai and Raizada, 1989). Following 15-day
exposures, test groups exposed to 10,000, 20,000, and 30,000 µg Pb/L experienced growth rates
that were 90.5, 76.9, and 66.7% of the controls (Rai and Raizada, 1989). Synechococcus
aeruginosus experienced little inhibition of growth from exposure to Pb-nitrate up to a
concentration of 82,000 µg/L (Jampani, 1988). At a test concentration of 100,000 µg/L,
complete inhibition of growth was observed, and at a concentration of 200,000 µg/L, algae failed
to establish a single colony (Jampani, 1988). Scenedesmus obliquus are quite tolerant to the
effects of Pb-nitrate and Pb-acetate on growth. Algae exposed to Pb-nitrate or Pb-acetate up to
180,000 µg/L had higher cell numbers than controls (Adam and Abdel-Basset, 1990). Exposure
to the highest concentration of 300,000 µg/L Pb-nitrate or Pb-acetate resulted in cell numbers
that were 81 and 90% of the controls, respectively (Adam and Abdel-Basset, 1990).
Lead in combination with other metals (e.g., Pb and Cd, Pb and Ni, etc.) is generally less
toxic than exposure to Pb alone (Rai and Raizada, 1989). Nostoc muscorum exposed to
chromium and Pb in combination demonstrated better growth than when exposed to either of the
metals alone (Rai and Raizada, 1989). Antagonistic interaction was observed in the exposure of
Nostoc muscorum to Pb and nickel in combination (Rai and Raizada, 1989). When applied
separately, these metals demonstrated different levels of toxicity; however, in combination, they
exerted similar effects (Rai and Raizada, 1989). More information on toxic interactions of Pb
with other metals is provided in Section AX7.2.3.5.
7
The species name Selenastrum capricornutum has been changed to Pseudokirchneriella subcapitata. The
former species name is used in this report.
AX7-178