**3.5 Spatial distributions of the heavy metals**

**Figures 5**–**8** show spatial distribution patterns of the heavy metals at the two sites, which were analyzed using the inverse distance weighted (IDW) interpolation method. The analysis revealed elevated levels of heavy metals in subsoil (Cd, Pb at site H and Cr, Cu at site F). Spatial maps also showed that site H was more polluted with Pb and Cd, while site F was mainly Cr and Cu.

### **Figure 5.**

*Spatial distributions of Cd in subsoil (L) and topsoil (R) of sites F and H.*

*Heavy Metal Pollution Resulting from Informal E-Waste Recycling in the Greater Accra Region… DOI: http://dx.doi.org/10.5772/intechopen.112397*

### **Figure 7.**

*Spatial distributions of Cu in subsoil (L) and topsoil (R) of sites F and H.*

**Figure 8.**

*Spatial distributions of Pb in subsoil (L) and topsoil (R) of sites F and H.*

### **3.6 Concentration differences at increasing distance from the scrapyard**

The study also sought to determine levels of heavy metals in the soil components at different distances from the scrapyard. This was important to evaluate the extent to which informal e-waste activities affected nearby communities. The result is provided in **Table 10**. Soil samples taken 25, 50, 75, and 100 m from the scrapyard were mainly sandy. pH values were mildly acidic and were within the 6.5–8.5 WHO thresholds. This indicates a decreasing pH as one moves away from the scrapyard.

Results revealed no level of Cd in these soil samples. Samples within the 25 m distance recorded respective concentrations of 20.73 and 24.94 ppm for Cr and Cu and were within safe levels set by WHO/FAO but slightly above permissible levels of Ghana EPA concerning Cu. However, Pb recorded concentrations of 155.17 ppm, which exceed the safe levels of Pb as determined by both WHO/FAO and Ghana EPA. The pH of the soil sample at 25 m was almost neutral at 6.97.


### **Table 10.**

*Heavy metal levels at distances from the scrapyard.*

Levels of Cr and Cu in samples within the 50 m boundary were within the safe limits set by WHO/FAO, but above permissible levels of Ghana EPA, with respective concentrations of 25.18 and 96.73 ppm. Pb quantified in these samples shows levels were above the 50-ppm threshold of WHO/FAO and the 20-ppm threshold of Ghana EPA, reaching levels of 74.72 ppm. The pH of the soil sample at 50 m was mildly acidic (6.58). Samples taken 75 m from the scrapyard had concentrations of 4.122 ppm (Cr), 4.600 ppm (Cu), and 5.965 ppm (Pb), while at a 100 m distance variation samples analyzed revealed no levels of Cr, 1.260 ppm of Cu, and 8.970 ppm of Pb.

### **3.7 Heavy metal concentration in water and water sediment**

**Table 11** compares levels of heavy metals at different sections and depths of a drain near the scrapyard. Water sediments outside the scrapyard showed lower concentrations of heavy metals than those obtained within the scrapyard. In contrast, none of the four heavy metals was detected in the water samples. Water sediment outside the scrapyard contained levels of Cd at 0.03 ppm, Cr at 11.95 ppm, and Cu and Pb concentrations, respectively, at 5.84 and 5.89 ppm. Water sediment within the scrapyard contained 0.49 ppm Cd and a concentration of 217.98 ppm for Cu. Cr had a concentration of 12.28 ppm, while Pb had a concentration of 44.77 ppm.

### **4. Discussion**

Uncontrolled levels and spatial variabilities of e-waste have serious environmental repercussions. E-waste-laden environments have significant amounts of heavy metals. Such metals interfere with ecosystem integrity and health. Bioaccumulation and biomagnification of the metals remain persistent in the food webs. They pose severe hazards and risks to the biota. More significantly to humans, chronic exposure to these metals in uncontrolled scrap settings and using substandard resource recovery methods put them at high risk of several health damages, which include carcinogenicity, teratogenicity, mutagenicity, genotoxicity, immunosuppression, and physiological *Heavy Metal Pollution Resulting from Informal E-Waste Recycling in the Greater Accra Region… DOI: http://dx.doi.org/10.5772/intechopen.112397*


### **Table 11.**

*Heavy metals concentrations in the water sample.*

and biochemical disorders [32–34]. While the toxicological analysis of the above effects on scrap workers was beyond the scope of the study, the environmental profile analysis has discovered some heavy metals in the study area, which hitherto was unknown. This sets a baseline upon which future research dimensions can evolve.

The concentrations and spatial variations (using IDW) of the heavy metals and the pollution levels using Igeo, CF, and PLI have been quantified and presented in the previous section, together with pH variations at the two e-waste burning sites. Generally, the study revealed that topsoil concentrations of heavy metals were higher than those of the subsoil, with few exceptions. This general trend could be due to the strong affinity of the heavy metals, mostly Pb and Cu, with the abundance of organic matter and minerals found in the topsoil, preventing the percolation of the heavy metals into the subsoil [35–37]. Additionally, it can be inferred from the results that anthropogenic pollution of heavy metals has more effect on the topsoil than subsoil. However, heavy metals found in the subsoil are particularly worrying, as the absorption of nutrients and water by plants takes place through the root system in the subsoil. The subsoil is also home to diverse microorganisms, and toxic metals can destabilize their niche. The high concentrations of heavy metals in some subsoils than in topsoil can be attributed to the leaching capability of the topsoil. Due to the high porosity of the top, sandy soil, heavy metals such as Cd and Cr are retained less in the topsoil and are percolated towards the subsoil [38]. Furthermore, Cd and Cr are less bonded to organic matter and minerals in the soil [38–39]. The above trends are comparable to other studies [39–43]. Pb and Cu were the heavy metals with the highest concentration, possibly because they find more applications in EEE, such as printed circuit boards, cathode ray tubes, bare/insulated wires, refrigeration units, fluorescent bulbs, batteries, and fuses. Furthermore, since Pb is not biodegradable, concentrations of Pb could build up for all the operational years of the scrapyard, resulting in the high concentrations measured. Sources of chromium in the scrapyard include steel alloy, and colored plastics, which are used as combustible materials for the burning of e-waste materials. Comparatively, Cr concentrations at site F were higher than at site H, possibly because the metal containers housing e-waste materials were closer to site F. These are typically composed of steel and chromium, so any wear and tear on the metal add Cr concentration to the soil. Cd was the heavy metal with the least concentration. In addition to the leaching and percolation effect of the soil structure,

the mild to acidic pH of soils has also been shown to be a factor in the high mobility of Cd, resulting in its lower concentrations in the soil component [29]. Site H had higher concentrations of Cd than site F because Cd-containing e-waste materials, including printed circuit boards, batteries, accumulators, cathode ray tubes, and ultraviolet lights, were located more at the former site than the latter. However, the low concentrations of Cd should not be underestimated, as Cd is one of the most toxic heavy metals, especially to aquatic organisms. Cd pollution is related to an increased mortality rate from obstructive lung disease. Cadmium absorption also causes shortness of breath and emphysema. All heavy metals under consideration exceeded national and international standards, suggesting that the open burning of e-waste materials to extract valuable metals leads to excessive pollution of the environment. Indeed, other studies and research reach similar conclusions, and in some cases, other pollutants, such as Poly Aromatic Hydrocarbons (PAHs), are further identified. Igeo, CF, and PLI metrics have substantiated the current study's heavy metal pollution variations.

Heavy metal adsorption and retention by soil increases generally within a pH range of 4–7 [38, 44], and therefore the pH ranges from the study could account for the elevated levels of heavy metals found in the samples. According to a study by [30], dumpsite samples could retain heavy metals within a pH range of 2–8. The high pH value recorded in sample 5B (8.03) could be due to alkaline batteries, steel mills, and ashes from the incineration processes at the e-waste site. The range of pH values for this study is comparable to other e-waste research [9, 28].

The general decline of pH at increasing distance from the scrapyard was expected as increasing distance from the scrapyard meant decreasing heavy metal concentrations, most alkaline. This result is comparable to a study by Tang et al. [45], where the pH at a dumpsite decreased from 5.9 to 4.7 at 18 m from the dump site. The current research indicates that activities at the scrapyard had an effect 25–50 m away from it. However, since soil samples taken at 25 and 50 m were close to the Accra-Tema motorway, contamination from road dust is still possible since heavy metals are found in tires and brake abrasion, combustion exhaust, and pavement wear [46]. Further research will be needed to evaluate this assertion. With a general decline in the concentrations of heavy metals from the 75 and 100 m distance, the high levels of heavy metals within the scrapyard can be attributed mainly to the e-waste activities. Comparably, Cr, Cu, and Pb concentrations were several times higher within the scrapyard than outside. This decreasing concentration of heavy metals with increasing distances from the scrapyard agrees with other studies, which explored the effect of increasing distance from the source on concentration levels of heavy metals [47–49].

Analysis of water sediments showed that levels of the toxic metals in the water sediments increased significantly within the scrapyard compared to the control sample, which was taken outside the scrapyard area. With the drainage lying at a lower plain to the two burning sites, and with the movement of air current across the drainage from the two burning sites, it can be fairly postulated that the e-waste activities are a possible source of heavy metals in the water-sediment, through the actions of wind drift, wet and dry depositions. Another possibility is the presence of e-waste materials near or inside the drainage, causing heavy metals to leach into it [50]. Compared to no detection levels within the water itself, the relatively concentrated amounts of heavy metals in sediments affirm studies associating the high affinity of heavy metals with the suspended matter in water environments [51–52]. Heavy metals in the wastewater were above the standard permissible levels of Ghana EPA and WHO/FAO. This is of major concern as it serves as an irrigation source for farming crops and as drinking water for herds of cattle near the scrapyard. Studies conducted

### *Heavy Metal Pollution Resulting from Informal E-Waste Recycling in the Greater Accra Region… DOI: http://dx.doi.org/10.5772/intechopen.112397*

on vegetation and animals near the e-waste scrapyard revealed high levels of toxic metals in plants' root, stem, and leaves [53].

Sediment and water from the drain generally had neutral pH for both control samples and those taken within the scrapyard area. This observation differs from other studies [54–56] where the pH of water samples was in the acidic range (3.78– 6.53). At lower pH, metals tend to have higher solubilities, leading to higher metal levels. This could be one of the primary reasons for detecting higher heavy metal concentrations in the water samples reported in the other studies [54–56] than in the current research. The highly positive correlation coefficients observed between pairs of heavy metals (0.90, 0.96, 0.97 in **Table 5** and 0.98 in **Table 6**) may be due to their dual complementary usage in certain EEE products. For instance, Cd and Pb find close applications in cathode ray tubes where Cd is used as the fluorescent powder coatings to produce color, while Pb is employed to absorb the UV lights and X-rays built. Cd-Cu alloy wires are more resistant to softening at higher temperatures, hence their co-occurrence in the waste. Pb alloyed to Cu acts as a lubricant and assists in chip breakup, increasing the machinability of the Cu metal. Since site H is a burning site and dumping grounds for e-waste materials, heavy metals can be carried from site F to site H. This could explain the high positive correlation (0.90, 0.95, 0.97, and 0.99) between heavy metals at different sites in **Table 7**. The weak correlations between heavy metals at the two sites could also indicate different and unrelated sources of contamination of the heavy metals.

Coefficient of variation (CV) results suggest that most heavy metals are widely dispersed rather than contained at locations. Wind effects, dry and wet deposition, and migration through water and soil are the primary sources of heavy metal dispersion or transport. High levels due to transport are a worry as it indicates e-waste recycling pollution is not limited to its immediate surroundings but can extend to other parts of the environment. Additionally, CV values provide insight into the sources of contamination. According to a study by [57], a CV of less than 20% indicates natural sources, while values greater than 50% imply anthropogenic sources. By inference, the heavy metal pollution was primarily due to anthropogenic sources, specifically e-waste activities, amplified by environmental factors.

### **5. Conclusions**

The research showed that the heavy metal levels exceeded the permissible limits of the WHO/FAO and Ghana EPA standards. Pollution indices suggest the e-waste scrapyard were polluted with the four heavy metals investigated in varying degree. The CV results indicate that metal pollution is primarily anthropogenic-given and widely dispersed. Spatial distribution maps suggest contamination of the scrapyard, especially at the western north of site H and the central portion of site F. Consequently, environmental laws and regulations on the management and recycling of e-waste should be enforced by local authorities to prevent further pollution of the scrapyard and its environment. Public awareness and education on the adverse effect of informal recycling practices should be intensified. The study has further shown that Cd and Pb levels in the scrapyard suggest skewed distributions relative to Cr and Cu, which are normally distributed. This outcome provides insight into modeling the behavior of these metals in the future. Finally, future studies can also focus on investigating heavy metal contamination in workers at the scrapyard and herds of cattle around the environment.
