Skip to Main Content

Table 5 shows the effects of different water sources used for irrigation of guava crops on the heavy metal and microbial content of the guava fruit. As shown in Table 5, the heavy metals Ni, Cr and Pb were not detected in either of the guava samples. On the other hand, heavy metals Cd, Cu and Zn were detected at levels that were lower than the safe recommended values by WHO. This observation could be a result of the low concentrations of heavy metals found in both the water sources used for irrigation. Besides that, a previous report has suggested that heavy metals taken up by plants tend to remain in the roots, and only a fraction of the heavy metals absorbed is translocated to other parts of the plants such as the fruit (Al-Lahham et al. 2007). Translocation of heavy metals to other parts of the plants has also been reported to be attributed to the tendency of different parts of the plant to accumulate certain amounts of metals (Fazeli et al. 1991). This explains the phenomenon whereby minimal uptake of heavy metals from soil and water was observed in the guava fruits. Results from Table 5 also showed that guava fruits from plants irrigated with both the different water sources were completely uncontaminated. This could be a result of the low microbial levels in both the water sources used for irrigation. Guavas are fruits that are mostly eaten raw, and therefore there are regulations for the quality of water that should be used for irrigation of this particular crop (WHO 1989). With regards to heavy metal uptake and microbial contamination, both the water sources used for irrigation in this study resulted in fruits that do not pose a public health risk.

Table 5

Effects of different water sources used for irrigation of guava crops on the heavy metal and microbial content of the guava fruit

 TWWLWWHO permissible level
Heavy metals 
 Nickel, Ni (ppm) ND ND <0.01 
 Cadmium, Cd (ppm) 0.03 ± 0.01a 0.04 ± 0.01a <0.1 
 Chromium, Cr (ppm) ND ND <0.01 
 Copper, Cu (ppm) 0.05 ± 0.01a 0.03 ± 0.01a <1 
 Lead, Pb (ppm) ND ND <2 
 Zinc, Zn (ppm) 0.06 ± 0.02a 0.05 ± 0.01a <5 
Microbiological parameters 
 Faecal coliforms (CFU/100 ml) ND ND <1000 
 E. coli (CFU/100 ml) ND ND <1000 
 TWWLWWHO permissible level
Heavy metals 
 Nickel, Ni (ppm) ND ND <0.01 
 Cadmium, Cd (ppm) 0.03 ± 0.01a 0.04 ± 0.01a <0.1 
 Chromium, Cr (ppm) ND ND <0.01 
 Copper, Cu (ppm) 0.05 ± 0.01a 0.03 ± 0.01a <1 
 Lead, Pb (ppm) ND ND <2 
 Zinc, Zn (ppm) 0.06 ± 0.02a 0.05 ± 0.01a <5 
Microbiological parameters 
 Faecal coliforms (CFU/100 ml) ND ND <1000 
 E. coli (CFU/100 ml) ND ND <1000 

Values followed by different letters within the same column are significantly different for each fruit (p < 0.05) (n = 30). TWW: treated waste water; LW: lake water; ND: not detected.

Close Modal

or Create an Account

Close Modal
Close Modal