Physiochemical analysis of soil and water samples
The physicochemical properties of water samples collected from a river at about 300 m from the quarry site and soil samples collected around the quarry site are presented in Tables 1 and 2, respectively. The physicochemical properties of the water samples all fall within the permissible limits set by WHO except alkalinity, turbidity, hardness, suspended solids, and COD (Table 1). This result is similar to the report of Kalu (2018). The water sample is highly turbid, in concordance with the value of suspended solids. Although the value of dissolved solids is lower than the set limit, the water sample contains more suspended solids, which may emanate from the dust particles from the quarry site. Suspended particles in water may absorb radiation from sunlight, making the water warmer. Also, high turbidity affects light penetration, thereby affecting aquatic organisms. Low conductivity may indicate that the sample contains fewer inorganic mobile ions. High total hardness indicates that the sample contains a high amount of Ca and Mg ions, probably from rock particles due to quarry activities. Thus, the water sample may not be good for laundry purposes. Higher COD shows that the sample contains high levels of oxidizable chemical substances; it is moderately polluted and may have an adverse effect on the survival of aquatic organisms.
Table 1
Result of physicochemical parameters of the quarry water sample
Parameters | Result | Nis –WHO Standard |
Colour | Non conform | Clear Colorless Liquid |
pH @ 250C | 7.2 | 6.50–8.50 |
Conductivity (us/cm) | 458 | 2500 (max) |
Alkalinity(mg/L, CaCO3) | 144 | 100 |
Turbidity (NTU) | 56.3 | 5 |
Total Dissolved Solid (mg/L) | 317.5 | 2000 (max) |
Total Hardness (mg/L, CaCO3) | 206.4 | < 200 (max) |
Phosphate (mg/L, PO43−) | 0.13 | 0.3 |
Sulphate (mg/L, SO42−) | 12.9 | 250 (max) |
Total Suspended Solids (mg/L) | 75 | 10 |
COD (mg/L) | 114 | 10 (max) |
BOD (mg/L) | 12 | 10 (max) |
*BOD – Biochemical oxygen demand * COD – Chemical oxygen demand *BDL – Below detectable limit *NS – Not Specified * < - Less than * Max – Maximum |
The results of temperature, pH, total dissolved solids and BOD are similar to the result reported by Kokcha & Chatrath (2021). While the conductivity, alkalinity and sulphate were observed to be lower than the results obtained from the same study.
Table 2
Result of physicochemical properties of soil samples
PARAMETER | Composite (100 + 200 m) | Control (1000 m) | FAO/WHO |
pH (at 25 oC) | 8.74 | 8.04 | 7 |
Redox (mV) | -28 | 4 | NA |
Moisture (%) | 34.1 | 26.3 | |
Porosity (%) | 32.2 | 24 | 0.49 |
Bulk Density (g/cm3) | 0.92 | 1.18 | 1.13 |
Cation Exchange Capacity (mEq/100g) | 0.27 | 0.23 | 12.5 |
Soil Organic Carbon (%) | 0.18 | 4.14 | 0.50–7.50 |
Alkalinity (mEq/100g) | 2.4 | 1.5 | ≥ 9.00 |
Sand (%) | 98.1 | 95.1 | 69.5 |
Silt (%) | 1.9 | 4.9 | 63.5 |
Clay (%) | 0 | 0 | 35 |
The pH of both the soil samples around the quarry site and control is higher than neutral (slightly alkaline) and above the pH range of soils that can support agricultural purposes (6.0-7.5). The quarry soil samples and control are highly porous compared to the recommended standard. Bulk density is an indication of soil compaction and affects water and nutrient availability for plant uptake. Generally, the higher the soil porosity, the lower the bulk density, as indicated in the quarry soil. The quarry soil is porous, sandy, with low CEC, and may not support agricultural purposes.
Soil in all the sampling points generally contained low organic matter content, with the highest being at sampling points 100 m and 200 m. The organic matter content of the soil at the control (1000 m) was generally higher when compared to that obtained in a similar study (Moses & Edet, 2013). However, at sampling points 100 m and 200 m, the organic matter content was generally lower than that reported by Effiong and Gilbert (2012) in a similar study. The percentage of sand, silt, and clay obtained was similar to those obtained by Ojo et al. (2018) and Moses & Edet (2013). Results obtained revealed a decline in soil quality near the quarry, similar to the reports of Igwenagu-Ifeanyi et al. (2021). Soil organic matter is a principal variable that affects the spatial distribution of heavy metals in the soil. An increase in soil organic matter content leads to the elevation of soil adsorption capacity, hence enhancing the accumulation of trace metals. Organic matter can be considered as an important medium through which heavy metals are incorporated into the soil.
Metal analysis of soil, plant and water samples
The concentrations of heavy metals in the rock, soil, and plant samples did not follow a regular pattern. The concentrations of most metals in rock samples are higher than those of soil samples collected around the quarry site (Table 3). The levels of metals recorded in soil samples closer to the quarry site are higher than levels in control samples collected far away from the site for Al, Ba, Cu, Fe, Mn, Ni, especially at 200 m away from the site. The concentration of Fe is the highest in all the samples analyzed in this study. The concentrations of Al, B, Cd, Cr, Cu, Fe, Mn, and Pb in most of the rock and soil samples are higher than the W.H.O. permissible standard. The high levels of toxic metals recorded in rock samples on the quarry site are similar to the report of Igwenagu-Ifeanyi et al. (2021).
The higher concentrations of toxic metals recorded in sampling positions within the quarry site confirm the relationship between metal concentrations and distance from the quarry, which is in good agreement with the report of Ekpo et al. (2012).
Table 3
Result of Metal analysis in Soil, Plant, and Rock Samples
METALS | Rock | S1 | S2 | S4 | SC | WHO (mg/kg) |
Ag | 9.94 ± 0.00 | 3.947 ± 0.00 | 12.27 ± 0.00 | 12.82 ± 0.00 | 14.11 ± 0.33 | 6.00 |
Al | 3961.77 ± 0.10 | 611.17 ± 0.05 | 708.26 ± 0.10 | 278.43 ± 0.58 | 118.19 ± 0.02 | 0.70 |
As | 11.07 ± 0.03 | 45.65 ± 0.02 | 30.98 ± 0.02 | 78.44 ± 0.02 | 12.88 ± 0.00 | 20.00 |
B | 244.03 ± 0.02 | 9.11 ± 0.00 | 0.03 ± 0.00 | 20.09 ± 0.00 | 10.89 ± 0.00 | 2.40 |
Ba | 597.52 ± 0.01 | 54.47 ± 0.01 | 20.93 ± 0.01 | 12.84 ± 0.00 | 78.49 ± 0.09 | 0.70 |
Cd | 111.77 ± 8.34 | 57.78 ± 0.42 | 11.78 ± 0.08 | 28.24 ± 0.30 | 32.35 ± 0.00 | 0.80 |
Co | 251.19 ± 0.00 | 24.27 ± 0.00 | 6.49 ± 0.00 | 38.45 ± 0.00 | 63.99 ± 0.00 | 50.00 |
Cr | 262.84 ± 0.00 | 34.93 ± 0.02 | 159.46 ± 0.00 | 43.97 ± 0.00 | 11.12 ± 0.00 | 100.00 |
Cu | 101.23 ± 0.00 | 212.99 ± 0.00 | 511.68 ± 0.00 | 82.59 ± 0.00 | 46.06 ± 0.00 | 36.00 |
Fe | 3094.87 ± 0.01 | 261.67 ± 0.00 | 1449.37 ± 0.00 | 132.94 ± 0.00 | 52.32 ± 0.00 | 50.00 |
Mn | 2816.07 ± 0.12 | 61.82 ± 0.01 | 6266.28 ± 0.04 | 36.26 ± 0.00 | 0.02 ± 0.01 | 20.00 |
Ni | 235.78 ± 4.34 | 11.57195 ± 0.61 | 166.27 ± 0.45 | 64.44 ± 0.47 | 0.23 ± 0.01 | 35.00 |
Pb | 182.72 ± 3.85 | 85.61 ± 0.09 | 40.66 ± 0.15 | 234.93 ± 0.09 | 3.49 ± 0.00 | 85.00 |
S1-Soil samples at 100m; S2-Soil samples at 200m; S4-Soil samples at 400m; SC- control soil samples.
Metal analysis of water and plant samples
The highest concentration of all the heavy metals analyzed in the water sample is Fe, closely followed by Al and Mn, which are above the NIS-WHO permissible limit, while B is within the WHO permissible limit. The highest concentrations of all the heavy metals analyzed in the plant samples were recorded in the sampling position P (100m), which is in the immediate vicinity of the quarry. The highest concentration of elements in the plant samples obtained was Fe, closely followed by Cu and Cr. Most of the metals were observed to be below WHO permissible limits, especially for the control, which suggests that the quarry site may have little or no effect on the plants. The concentration of dissolved metals in the water sample around the quarrying site at 200 m was observed to be higher than the WHO permissible limits (Table 4). The result of this can be attributed to high amounts of suspended solids than permitted, as well as a slightly higher BOD and COD as shown in Table 1.
Table 4
Result of Metal analysis of rock, plants and water samples
METALS | Rock | P1 | Pc | W2 | WHO Plant (mg/kg) | WHO Water(mg/L) |
Ag | 9.94 ± 0.00 | 0.04 ± 0.00 | BDL | 0.53 ± 0.00 | - | 0.25 |
Al | 3961.77 ± 0.10 | 9.94 ± 0.070 | 1.12 ± 9.45 | 26.33 ± 0.05 | - | 0.01 |
As | 11.07 ± 0.03 | BDL | BDL | 1.30 ± 0.01 | - | 0.01 |
B | 244.03 ± 0.02 | BDL | BDL | BDL | - | 2.40 |
Ba | 597.52 ± 0.01 | BDL | BDL | 24.93 ± 0.00 | - | 0.01 |
Cd | 111.77 ± 8.34 | 0.30 ± 0.07 | BDL | 1.32 ± 0.35 | 0.02 | 0.03 |
Co | 251.19 ± 0.00 | 0.10 ± 0.00 | 1.73 ± 0.14 | 1.07 ± 0.35 | 50.00 | 0.05 |
Cr | 262.84 ± 0.00 | 25.63 ± 0.00 | 6.11 ± 0.58 | 3.04 ± 0.01 | 1.30 | 0.05 |
Cu | 101.23 ± 0.00 | 32.75 ± 0.00 | 5.33 ± 0.41 | 6.61 ± 0.00 | 10.00 | 2.00 |
Fe | 3094.87 ± 0.01 | 44.40 ± 0.00 | 46.24 ± 0.41 | 41.35 ± 0.00 | 20.00 | 0.30 |
Mn | 2816.07 ± 0.12 | 4.66 ± 0.01 | 4.66 ± 0.44 | 26.18 ± 0.02 | 2.00 | 0.20 |
Ni | 235.78 ± 4.34 | 0.13 ± 0.60 | BDL | 1.63 ± 0.02 | 10.00 | 1.40 |
Pb | 182.72 ± 3.85 | 0.03 ± 0.27 | 0.01 ± 0.37 | 0.12 ± 0.13 | 2.00 | 0.01 |
P1- P100 m and Pc- control P1000m (control)
Iron (Fe) has the highest concentrations in both plant samples and plant controls, while silver (Ag) has the lowest concentration in plant samples at 100m and lead (Pb) in plant control. The concentrations of arsenic (As), barium (Ba), and boron (B) in plant samples (at 100m) and control samples are below the detection limit of the instrument. Ag, cadmium (Cd), and nickel (Ni) are also below the detection limit of the instrument in plant control samples (Table 4). However, the Fe concentration was found to be higher in control compared to plant samples. The concentrations of As, B, and Ba are below the detection limit of the instrument used for both plant and control samples (Table 4). High levels of aluminum (Al), Cd, chromium (Cr), Cu, Fe, and Mn above the W.H.O. limit were recorded in plant and water samples close to the quarry site.
The concentration of Fe and Cr follow this trend; rock > Pc > Pi > W2, while the trend for Mn, Al and Cd is Rock > W2 > Pi > Pc. The concentrations of Al, As, Cd, Mn, and Ni in water samples are higher than the levels in plant samples. The concentrations of Cd, Cr, Cu, Fe, and Mn in the plant samples are above the W.H.O. permissible levels for metals in plant samples (Table 4). The high levels of dissolved metals in the analyzed water sample may indicate the high impact of quarry activities, whereby the dust particles from the site are washed into the water body. The impact is more on the water body compared to the plant samples.
Analysis of Variance comparisons of soil and plant samples
The analysis of variance showed no significant differences between the soil samples and the rock (Table 6). However, the control at 1000 m was observed to be significantly different from the rock. The mean difference between the soil samples at 200 m was observed to be the least, implying that the 200 m soil sampling point was most affected by the quarry site activities (Table 6). The soil sample at 200 m was more negatively affected by the activities of the quarry site, as there was no significant difference between the mean concentration of the rock and the mean concentration of the soil sample at 200 M and 100 M. Significant differences were observed between the rock sample and the soil samples at 400 M and 1000 M. It can also be inferred that the soil sample at 1000 m is less affected by the quarry, while the soil sample at 200 m was most affected. The mean concentration of heavy metals in the water sample at 200 m from the quarry site was considerably higher than the WHO permissible limit. This implies that the activities on the quarry site are having a negative impact on the water sample at 200 m.
Table 6
ANOVA Comparison between Soil Samples and Rock
Dependent Variable: Mean concentration LSD |
(I) Sampling Points | (J) Sampling Points | Mean Difference (I-J) | Sig. |
S100M | S200M | -1145.880* | 0.099 |
S400M | 83.577 | 0.902 |
S1km | 141.663 | 0.835 |
ROCK | -1333.201 | 0.057 |
S200M | S100M | 1145.880 | 0.099 |
S400M | 1229.457 | 0.078 |
S1km | 1287.543 | 0.065 |
ROCK | -187.322 | 0.783 |
S400M | S100M | -83.577 | 0.902 |
S200M | -1229.457 | 0.078 |
S1km | 58.086 | 0.932 |
ROCK | -1416.778 | 0.044 |
S1km | S100M | -141.663 | 0.835 |
S200M | -1287.542 | 0.065 |
S400M | -58.085 | 0.932 |
ROCK | -1474.867* | 0.036 |
ROCK | S100M | 1333.201 | 0.057 |
S200M | 187.321 | 0.783 |
S400M | 1416.778* | 0.044 |
S1km | 1474.864* | 0.036 |
*. The mean difference is significant at the 0.05 level. |
Heavy metal pollution not only results in adverse effects on various parameters related to plant quality and yield but also causes changes in the size, composition, and activity of the microbial community. Therefore, heavy metals are considered one of the major sources of soil pollution. Heavy metals indirectly affect soil enzymatic activities by shifting the microbial community, which synthesizes enzymes (Singh & Kalamdha, 2011; Nanda & Abraham, 2013; Lee et al., 2020). Therefore, it can be inferred that the high concentration of heavy metals in the soils at 100 m and 200 m was most likely a result of the activities on the quarrying site.
Effects of toxic metals on human health
The uptake of heavy metals by plants from soils in high concentrations may result in significant health risks, especially when considering food chain implications. The consumption of food crops contaminated with heavy metals is a significant food chain route for human exposure. Food plants, whose examination system is based on exhaustive and continuous cultivation, have a great capacity to extract elements from soils. The cultivation of such plants in contaminated soil represents a potential risk since the vegetal tissues can accumulate heavy metals. Heavy metals become toxic when they are not metabolized by the body and accumulate in soft tissues. The chronic ingestion of toxic metals has undesirable impacts on humans, and the associated harmful impacts become perceptible only after several years of exposure. Omasanya & Ajibade (2011) discovered that the prevalence of respiratory diseases among the Otere community is due to the presence of high levels of suspended particulate matter in the air.