TABLE 1.

Dynamics of nitrate reduction, nitrite appearance and consumption, and Cr(VI) reduction in carbon-, nitrate-, and chromium(VI)-amended anaerobic microcosms

Treatmenta	NO3−		NO2−			Chromium
	Reduction rateb	Final concnc	Maximum concn	Time of maximum concn (days)	Final concn	Reduction rate	Time at which Cr(VI) became undetectable (days)	Reduction rate after readdition	Final concn
N	431 ± 2	0	648 ± 161	2	0
GN	307 ± 77	452 ± 15	498 ± 35	2	260 ± 10
GNL	109 ± 38	455 ± 35	538 ± 45	7	192 ± 118	70 ± 0	2	48 ± 1	0
GNM	109 ± 77	465 ± 104	287 ± 128	7	149 ± 11	96 ± 1	4	81 ± 1	0
GNH	82 ± 24	580 ± 161	85 ± 48	35	85 ± 48	63 ± 5	11	28 ± 5	0
PN	309 ± 86	0	766 ± 218	2	0
PNL	154 ± 15	0	1,004 ± 43	5	0	70 ± 0	2	52 ± 1	0
PNM	75 ± 55	0	755 ± 318	7	0	98 ± 8	2	21 ± 3	0
PNH	63 ± 51	0	411 ± 38	14	0	99 ± 2	2	1 ± 1	29 ± 13

^aThe letters in the treatments indicate the addition of nitrate (N) (15 μmol g⁻¹ [dry weight] soil), glucose (G) (3 mg g⁻¹ [dry weight] soil), or protein (P) (3 mg g⁻¹ [dry weight] soil) and one of three chromium(VI) levels, low (L) (140 μg g⁻¹ [dry weight] soil), medium (M) (240 μg g⁻¹ [dry weight] soil), and high (H) (340 μg g⁻¹ [dry weight] soil).

^bReduction rates calculated for the first 48 h of incubation and reported as means ± standard errors for three replicate samples. The reduction rates are reported as micrograms gram⁻¹ soil day⁻¹.

^cAll final concentrations reported are means ± standard errors for three replicate samples. The final concentrations are reported as micrograms gram⁻¹ (dry weight) soil.