Effects of artisanal gold mining activities on soil properties in a part of southwestern Nigeria

Figures & data

Figure 1. Location and land cover/use characteristics of Itagunmodi in southwest Nigeria.

Figure 2. Examples of water-filled depressions that were created during gold search in Itagunmodi, Southwest Nigeria.

Figure 3. Frequencies of plant species across different land cover/use in Itagunmodi, southwest Nigeria.

Table 1. Mean ± standard error of selected physical and chemical variables of soil samples from different landuse/cover at Itagunmodi, southwest Nigeria

Parameters	Active mined site (n = 25)	Abandoned mine site (n = 25)	Farmland (n = 25)	Relatively undisturbed site (n = 25)
% Sand	61.52ª ± 0.16	72.22ª ± 0.22	52.61^b ± 0.35	54.64^b ± 0.22
% Silt	14.80^a ± 2.30	12.90ª ± 3.14	9.21^b ± 2.14	9.32^b ± 1.81
% Clay	13.10ª^,b ± 4.64	11.30^b ± 2.65	14.20ª^,b ± 3.93	17.00ª ± 4.70
Particle size	Sandy loam	Sandy loam	Loamy sand	Loamy sand
Total N (%)	0.03^b ± 0.02	0.03^b ± 0.02	1.10ª ± 0.23	1.20ª ± 0.24
Available P (mg kg^-1)	0.40^b ± 0.02	0.31^b ± 0.02	2.33ª ± 0.02	3.93ª ± 0.03
Organic C (%)	1.30^b ± 0.24	1.85^b ± 0.13	3.77ª ± 0.22	4.13ª ± 0.25
Ca^2+ (cmol kg^-1)	1.62^b ± 0.13	1.50^b ± 0.15	2.67ª ± 0.33	3.53ª ± 0.30
K^+ (cmol kg^-1)	0.07^b ± 0.01	0.04^b ± 0.01	0.11ª ± 0.01	0.12ª ± 0.01
Mg^2+ (cmol kg^-1)	0.17^b ± 0.04	0.15^b ± 0.04	0.63ª ± 0.06	0.70ª ± 0.09
Na^+ (cmol kg^-1)	0.27^b ± 0.05	0.20^b ± 0.06	0.62ª ± 0.05	0.79ª ± 0.15
Cation exchange capacity (cmol kg^-1)	1.47^b ± 0.09	1.29^b ± 0.08	3.38ª ± 0.18	3.68ª ± 0.27
Total acidity (%)	0.05ª^,b ± 0.25	0.07ª ± 0.19	0.04^b ± 0.23	0.05ª^,b ± 0.39
pH (H2O)	4.16^b ± 0.18	3.78^b ± 0.19	6.56ª ± 0.17	6.76ª ± 0.07
pH (KCl)	4.43^b ± 0.09	4.60^b ± 0.12	6.72ª ± 0.22	7.18ª ± 0.28
Zn (ppm)	4.44ª ± 0.01	4.47ª ± 0.01	1.85^b ± 0.01	1.27^b ± 0.01
Cu (ppm)	3.02ª ± 3.23	2.22ª ± 3.09	1.62^b ± 3.30	0.91^b ± 1.60
Mn (ppm)	73.39ª ± 1.51	74.86ª ± 1.51	55.93^b ± 1.14	48.42^b ± 2.56
Fe (ppm)	113.06ª ± 1.14	102.84ª ± 0.97	83.60^b ± 0.66	80.98^b ± 0.86
Pb (ppm)	2.69ª ± 0.16	2.77ª ± 0.19	0.56^b ± 0.29	0.61^b ± 0.20
Cd (ppm)	3.15ª ± 0.02	2.27ª ± 0.09	0.78^b ± 0.09	0.44^b ± 0.10
Hg (ppm)	0.26ª ± 0.01	0.28ª ± 0.01	0.12^b ± 0.03	0.10^b ± 0.02

Notes: The superscripts are used to indicate significant variations at 95% confidence level across rows.

Means at same row with same alphabet (lower case) are not significantly different at p ≤ 0.05.

Figure 4. Nemerow pollution index’ scale for pollution level interpretation and specific contamination level of selected heavy metals, across different sample areas at Itagumodi, southwest Nigeria.

Table 2. Deterioration index values (%) of soil properties under different land uses

Soil properties	Active mine site	Abandoned mine site	Farmland
pH(H2O)	38.5	44.1	3.1
pH(KCl)	38.4	35.9	6.4
Total N	97.5	97.5	8.3
Available P	89.8	92.3	40.6
Organic C	68.8	55.4	8.7
Ca^2+	54.3	57.7	24.1
Mg^2+	75.7	80.0	11.4
K^+	40.9	63.6	9.1
Na^+	65.4	74.4	20.5
CEC	60.2	65.1	7.9
Total acidity	13.0	−30.4	8.7
% Sand	−12.6	−32.2	3.7
% Clay	22.9	33.5	16.5
% Silt	−58.8	−38.4	1.2

Note: Underlined deterioration index values are considered significant (DI > 60%).