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

Nitrate uptake reported after 48, 72, and 96 h was reduced by 30.0, 37.5, and 38.9%,
respectively, compared to controls (Rai and Raizada, 1989). Lead in combination with
chromium, both at a test concentration of 20,000 µg/L, demonstrated antagonistic effects on
nitrate uptake. Compared to controls, nitrate uptake was reduced by 52.4, 30, 25, and 22.2% at
24, 48, 72 and 96 h, respectively (Rai and Raizada, 1989). The greatest effect on uptake
occurred at 24 h when, compared to controls, a 52.4% reduction was reported in the test
concentration. Lead and nickel in combination at test concentrations of 20,000 and 1000 µg/L,
respectively, resulted in a greater reduction of nitrate uptake than Pb alone at 48, 72, and 96 h
(Rai and Raizada, 1989).
After 24, 48, and 72 h of Pb exposure at 20,000 µg/L, nitrogenase activity (nmol C2H4/ µg
protein/hr) in Nostoc muscorum was reduced by 39.3, 61.8, and 14.1%, respectively, compared
to controls (Rai and Raizada, 1989). A concentration of 207.2 µg Pb/L had little effect on
nitrogen or phosphorus assimilation in Selenastrum capricornutum over 7 days (Capelo et al.,
1993). An antagonistic effect on nitrogenase activity was generally reported for Nostoc
muscorum exposed to Pb in combination with nickel at 20,000 and 1,000 µg/L, respectively
(Rai and Raizada, 1989). Compared to controls, nitrogenase activity was reduced by 42.9, 32.7,
and 13.6% at 24, 48, and 72 h, respectively (Rai and Raizada, 1989). Lead and chromium, both
administered at a concentration of 20,000 µg/L, had a synergistic impact on nitrogenase activity
in Nostoc muscorum. Nitrogenase activity in the test group was reduced by 60.7, 60, and 50%
compared to the controls at 24, 48, and 72 h, respectively (Rai and Raizada, 1989).
Lead-induced inhibition of ammonium uptake (µg NH4 uptake/µg Chl a) was greatest in
Nostoc muscorum after 48 h of exposure to 20,000 µg/L of lead. Compared to controls, the Pb
test concentration 20,000 µg/L reduced ammonium uptake by 72, 82, 61, and 26 % at 24, 48, 72,
and 96 h, respectively (Rai and Raizada, 1989). Lead in combination with nickel at
concentrations of 20,000 and 1,000 µg/L, respectively, demonstrated an antagonistic effect on
ammonium uptake. Compared to controls, ammonium uptake in the test group was reduced by
44.9, 54.1, 23.3, and 4% at 24, 48, 72, and 96 h, respectively (Rai and Raizada, 1989). Lead in
combination with chromium, both at concentrations of 20,000 µg/L, demonstrated a synergistic
interaction with 24, 48, 72, and 96 h uptake rates reduced by 87.2, 88.5, 72.5, and 50 %,
respectively, compared to controls (Rai and Raizada, 1989).
AX7-180