Phylogenetic Diversity of Archaea and the Archaeal Ammonia Monooxygenase Gene in Uranium Mining-Impacted Locations in Bulgaria

Table 1

Physicochemical characteristics of samples from three sites in Bulgaria polluted by uranium mining activities, expressed as means ± standard deviation (𝑛=15).

Parameter	𝐷	BC	BuhC	BuhD	Sliv
pH	—	—	6.9±0.3	6.6±0.2	7.5±0.3
OM	%	—	2.8±1.3	1.6±1.0	0.3±0.1
NO3-N	mg/kg	—	21.6±12.9	9.4±6.6	19.9±11.0
SO4	mg/kg	—	786±95.0	1300±142.0	151±14.0
As	mg/kg	3.84	274±13.0^1	72.4±2.8^1	412±22.0^1
Cd	mg/kg	0.15	2.4±1.3^1	1.1±1.2	2.7±1.8^1
Co	mg/kg	ND	29.5±1.2	27.2±1.2	22.4±1.4
Cr	mg/kg	51.00	89.6±2.6	95.2±7.4	8.6±1.9
Cu	mg/kg	47.34	236±11.4^1	101±21.0	3410±87.0^1
Ni	mg/kg	36.41	75.2±13.4	98.4±8.9^1	37.0±11.0
Pb	mg/kg	19.19	674±39.4^1	126±16.3	5160±49.9^1
Zn	mg/kg	54.98	448±52.0^1	464±23.1^1	1270±98.4^1
U	mg/kg	0.3–11*	200±21.2	78.4±8.7	374±11.2
TIAs	—	—	1.63±0.08	0.43±0.02	2.45±0.13
TICd	—	—	0.03±0.01	0.01±0.00	0.03±0.02
TICo	—	—	0.05±0.00	0.05±0.00	0.04±0.00
TICr	—	—	1.26±0.03	1.34±0.1	0.12±0.02
TICu	—	—	6.74±0.32	2.88±0.60	97.43±2.50
TINi	—	—	0.75±0.13	0.98±0.09	0.37±0.11
TIPb	—	—	1.03±0.06	0.19±0.02	7.90±0.08
TIZn	—	—	3.89±0.45	4.03±0.00	11.04±0.86
TIsum	—	—	15.38	9.91	119.38

1Value above the maximum allowable concentration referring to Bulgarian legislation [47]. ∗Values according to UNSCEAR [48]. ND: no data; 𝑛: number of samples; D: dimension; BC: background concentrations referring to Bulgarian legislation [47]; TI_sum: sum of toxicity indices of heavy metals (except U) and metalloid As.