Abstract
This study assessed the concentrations of arsenic and iron in paddy soil and rice grain samples collected from the Nobewam and Odumase paddy field sites in the Anum Valley of Ghana, as a means of determining the impacts of gold mining activities in the area on rice production. The arsenic content of rice grains from the Anum Valley paddy fields was compared to that in rice grains of the same variety harvested from three non-impacted paddy fields (control sites) in other parts of Ghana. The study findings indicated that soils in the Odumase paddy fields, which are located closer to the gold mining site, were significantly more impacted by mining pollution than soils in the Nobewam paddy fields. Arsenic concentration in the Nobewam paddy soils ranged from 0.6 to 76.1 mg/kg with a mean of 8.3 mg/kg, while that in the Odumase paddy soils ranged from 5.3 to 106.2 mg/kg with a mean of 41.1 mg/kg. Despite the significant difference in mean soil arsenic content, there was no significant difference in the arsenic content of rice grains harvested from the two Anum Valley paddy sites (i.e. Nobewam and Odumase). There was also no significant difference between the two Anum Valley paddy sites with respect to soil iron concentration. The regression equation for a graph of soil arsenic against soil iron (As = 70.0 Fe – 37.7) was, however, highly significant (P
Highlights
Located in the Ashanti region of Ghana is the Anum Valley Irrigation Project (AVIP) which was established in 1992 for the production of paddy rice
Since the water that flows through the Nobewam paddy fields is a mixture of water from both River Anum and River Owerri, it could be argued that the water flowing downstream from the source of River Anum causes a dilution of the arsenic concentration in River Owerri; accounting for the considerably lower mean total arsenic in the Nobewam soils
The study has confirmed that pollution from mining activities has resulted in high concentrations of arsenic in water and soils at the Nobewam and Odumase paddy field sites in the Anum Valley of Ghana
Summary
Located in the Ashanti region of Ghana is the Anum Valley Irrigation Project (AVIP) which was established in 1992 for the production of paddy rice. The AVIP paddy fields are located close to the former Konongo Gold Mine, known as the Owerri Gold Mines. It is worth noting that the Odumase paddy fields are in closer proximity to the gold mining site than the Nobewam fields (Figure 1). Evidence from earlier research showed that the gold mining activities at Konongo resulted in an elevation of the arsenic concentration in River Owerri. Arsenic concentrations much higher than the 10 μg/l permissible limit set by WHO for drinking water [1] have been recorded in water samples collected from River Owerri [2]. Analysis of water samples collected from irrigation channels at Nobewam and Odumase indicated that both sites are drained by arsenic-enriched water. The mean arsenic content of irrigation water from the Odumase paddy fields (144 ± 1.8 μg/l) was, found to be higher than that in water from the Nobewam paddy fields (27 ± 4.3 μg/l) [3]
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