The effect of soil types, pH, and geographical locations on carcinogenic metal buildup in Oryza sativa cultivated in Ghana.

This study investigated the impact of soil type, pH, and geographical locations on the accumulation of arsenic (As), lead (Pb), and cadmium (Cd) in rice grains cultivated in Ghana. One hundred rice farms for the sampling of rice grains and soil were selected from two regions in Ghana-Volta and Oti. The concentrations of As, Pb, and Cd were analyzed using ICP-OES. Speciation modeling and multivariate statistics were employed to ascertain the relations among measured parameters. The results showed significant variations in soil-As, Pb, and Cd levels across different soil types and pH ranges, with the highest soil-As and Cd found in alkaline vertisols. For soil-As and Cd, the vertisols with a pH more than 7.0 exhibited the highest mean concentration of As (2.51 ± 0.932 mgkg-1) and Cd (1.00 ± 0.244 mgkg-1) whereas for soil-Pb, the luvisols of soil types with a pH less than 6.0 exhibited the highest mean concentration of Pb (4.91 ± 1.540 mgkg-1). Grain As, Pb, and Cd also varied across soil types and pH levels. In regards to grain-As, the vertisols soil type, with a pH less than 6.0, shows the highest mean concentration of grain As, at 0.238 ± 0.107 mgkg-1. Furthermore, vertisols soil types with a pH level less than 6.0 showed the highest mean concentration of grain Cd, averaging at 0.231 ± 0.068 mgkg-1 while luvisols, with a pH less than 6.0, exhibited the highest mean concentration of grain Pb at 0.713 ± 0.099 mgkg-1. Speciation modeling indicated increased bioavailability of grains Cd2+ and Pb2+ ions in acidic conditions. A significant interaction was found between soil-Cd and pH, affecting grain-As uptake. The average concentrations of soil As, Pb, and Cd aligned with international standards. Generally, the carcinogenic metals detected in grain samples collected from the Volta region are higher than that of the Oti region but the differences are insignificant, and this may be attributed to geographical differences and anthropogenic activities. About 51% of the study area showed a hazard risk associated with grain metal levels, although, no carcinogenic risks were recognized. This study highlights the complex soil-plant interactions governing metal bioaccumulation and emphasizes the need for tailored strategies to minimize metal transfer into grains.

Ecotoxicity of heavy metals in soil around long-term e-waste recycling sites in Tema and Ashaiman areas of Ghana.

The effect of e-waste recycling activities on the prevalence of metals (Cd, Cu, Hg, Ni, Pb, and Zn) and a metalloid (As) in soil was assessed for four e-waste sites in Ghana. Samples of top- and subsoil were collected from dismantling and burning sections, and the prevalence and the distribution of selected metals were determined using atomic absorption spectroscopy. The concentrations of the metals analyzed were above the background concentrations except for Cd, which was detected at a comparable level to the background levels. Levels of Cu and Pb increased with increasing soil depth. Cd, Zn, As, and Ni levels decreased with increasing soil depth. However, Hg levels showed no recognizable trend in its distribution relative to soil depth. The pollution indices evaluated revealed deterioration of the soil quality at the e-waste sites. Pollution indices are used to categorize soil pollution levels based on cut-off values. Geo-accumulation indices suggested that the soil was very highly polluted with Pb, highly polluted with Cu, and moderately polluted with As, Hg, Cd, and Zn. The enrichment factor values indicated that soil from the studied sites was very highly enriched with Pb (i.e., EF of 9.60 to 63.14; median being 28.51) and significantly enriched with Cu and Hg (i.e., EF of 3.09 to 21.86; median 7.72 for Cu and EF of 1.48 to 25.5; median 10.57 for Hg). The contamination factor analysis revealed very high contamination of soils with Pb. The metals Cu, Zn, As, Ni, Cd, and Hg exhibited moderate to considerable contamination. This study is part of the continuous effort to assist policymakers with scientific information needed to influence policy decisions on environmental management in Ghana.