**3. Results**

### **3.1 Soil pH**

**Tables 2** and **3** show levels of heavy metals with their respective pH. pH values ranging from a mildly acidic pH of 5.88 to high alkaline pH of 8.03 was recorded for site F with an average of 7.13. At site H, samples had pH values between 6.07 and 7.78 and a mean of 6.94. pH values recorded were within the WHO benchmark of 6.5–8.5, except for three samples (5.88 at site F and 6.07, 6.38 at site H), which recorded pH values below the 6.5 minimum threshold.


### **Table 2.**

*Concentration and pH of soil samples at site F.*

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


**Table 3.**

*Concentration and pH of soil samples at site H.*

### **3.2 Heavy metal concentrations at the burning sites of the scrapyard**

The concentrations of the four heavy metals obtained are detailed in **Tables 2** and **3**. At site F, Cd ranged from a non-detection level to a maximum concentration of 1.57 ppm and an average of 0.48 ppm. Except for a subsoil sample with a concentration of 1.57 ppm, all Cd concentrations at site F were below the Ghana EPA permissible limit of 1.0 ppm and the WHO/FAO standard of 3 ppm. At site H, Cd concentrations were comparatively higher, with a minimum of 0.29 ppm, a maximum of 13.56 ppm, and an average concentration of 4.14 ppm, which exceeded Ghana EPA and the WHO/FAO standards.

A minimum concentration of 13.97 ppm and a maximum concentration of 162.50 ppm were recorded for Cr, with an average concentration of 77.33 ppm at site F. Most Cr concentrations exceeded the Ghana EPA threshold value of 30 ppm. Three samples also had Cr concentrations (123.07 ppm, 162.50 ppm, and 117.27 ppm) above the WHO/FAO standard of 100 ppm. However, Cr levels from site H were below the permissible limit of WHO/FAO and Ghana EPA with minimum and maximum concentrations of 15.95 ppm and 30.11 ppm, respectively, and an average of 21.00 ppm.

At site F, minimum and maximum concentrations of 29.97 and 253.42 ppm were recorded for Cu, with an average concentration of 114.85 ppm. They exceeded the permissible levels of Ghana EPA (20 ppm) and the WHO/FAO standards of 100 ppm. Also, at site H, Cu recorded minimum and maximum concentrations of 5.24 and 108.76 ppm, respectively, and an average concentration of 48.37 ppm, above the national and international standard limits.

At site F, a minimum concentration of 13.58 ppm and a maximum concentration of 276.78 ppm were recorded for Pb with an average concentration of 77.07 ppm, which

**Figure 3.**  *Heavy metal levels in samples from site F.*

**Figure 4.**

*Heavy metal levels in samples from site H.*

was above the WHO/FAO and Ghana EPA standard of 50 ppm and 20 ppm, respectively. Pb in the sampled soil had a minimum concentration of 17.81 ppm, a maximum concentration of 1000.85 ppm, and an average concentration of 341.43 ppm at site H, exceeding the Ghana EPA and WHO/FAO standard limits.

The extent of pollution at sites F and H can be respectively expressed as Cu > Cr > Pb > Cd and Pb > Cu > Cr > Cd. This is also illustrated graphically in **Figures 3** and **4**.

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


### **Table 4.**

*A review of research studies on heavy metals concentrations (ppm) in e-waste soil.*

Heavy metal concentrations in this study were similar to other research works in e-waste research, as shown in **Table 4**. Generally, Cu and Pb were in high concentrations in most of the research studies. Also, Cd concentrations are lower in most e-waste soils in other research works.

### **3.3 Statistical analysis**

Pearson correlation revealed a positive relationship (p < 0.05 and p < 0.01) between Cd and Cu, Cd and Pb, and Cu and Pb in the subsoil at both investigated sites. These relationships are depicted in **Tables 5** and **6**.

Positive correlations were established between concentrations of heavy metals within the subsoil at both sites. This is shown in **Table 7**.

Coefficient of variation (CV) was computed for each heavy metal at both e-waste burning sites. Cr showed the least variation with CV values of 57.63% and 22.14%, respectively, at sites F and H. At sites F and H, CV values for Cd were high (136.77% and 107.76%, respectively), whiles Pb had CV values of 103.92% at site F and 93.13% at site H. A CV value of 61.24% was obtained for Cu at site F. Comparatively, a higher measurement of Cu was recorded at site H, with a CV value of 125.25%.

An independent t-test was conducted at p < 0.05 to determine the statistical significance of the mean concentration of the heavy metal. Results showed the following:


### *Heavy Metals – Recent Advances*


*a significant correlation at the 0.05 level (2-tailed). b*

*significant correlation at the 0.01 level (2-tailed).*

### **Table 5.**

*Pearson correlation between heavy metal levels in the subsoil at site F.*

