Multi-element contamination in soils from major mining areas in Northeastern of Brazil.

Mining has become one of the main factors in the global biogeochemical cycle of potentially toxic elements. Therefore, it is considered one of the anthropogenic activities with the greatest negative impact on the environment. These impacts are maximized in semiarid regions, where mining activities can lead to soil degradation and decrease in land productivity. This study aimed to assess the level of contamination in natural, urban, and agricultural soils of three important mining areas, where approximately 80,000 people live, and pollution levels have never been determined before. For this purpose, soil samples were collected around iron, uranium, and vanadium mines, as well as in the main human settlements of the region. The concentrations of 34 elements were determined by instrumental neutron analysis activation (INAA) and inductively coupled plasma optical emission spectrometry (ICP OES) techniques. Pollution indices (CF, EF, mCd, PLI, and REEP) revealed that there is a moderate to heavy level of pollution for 89% of the analyzed elements. Additionally, an extreme contamination level was observed in 78% of the samples, for at least one element. Statistical analyses were performed to identify patterns in the distribution and common sources of pollution. The results suggest that the concentrations for Al, Ba, Hf, Na, Pb, Rb, REE, Ta, Th, U, Zn, and Zr are associated with geogenic causes. However, the influence of anthropogenic sources such as agriculture and mining on the accumulation of these elements in soils should not be disregarded. In contrast, the contents of As, Br, Cd, Co, Cr, Cs, Cu, Fe, K, Mn, Ni, Sc, Ti, and V reflect the direct impact of anthropogenic sources.

Bioaccumulation of nickel in tomato plants: risks to human health and agro-environmental impacts.

Anthropogenic activities such as agriculture, industry, and mining have contributed significantly to the accumulation of heavy metals in the soil, which in turn cause problems to human health and to the environment. The present work aims to study the effects of nickel (Ni) on the development of tomato plants, the risks to human health associated to the consumption of contaminated tomatoes, and the consequences to the environment. The experiment was carried out in greenhouse environment for a period of 120 days, and the plants were cultivated in soils with four different concentrations of Ni: 0, 35, 70, and 105 mg kg-1. The concentration of nickel in each part (root, stem, leaf, and fruit) of the tomato plant was measured at four different stages of the cycle: 30, 60, 90, and 120 days, by inductively coupled plasma optical emission spectrometer (ICP-OES). At the end of the cycle, the concentration of certain macro- and micronutrients was also determined and related to the corresponding Ni concentration in the soil. The distribution of Ni in the parts of the plant was analyzed from the bioaccumulation factor temporal behavior. Nickel concentrations found in the fruit were too low to pose a risk to human health. As a result of this research, it was verified that soils with nickel concentrations close to 70 mg kg-1, which is the limit established by the CONAMA resolution (420/2009), may actually represent an optimum concentration value for the development of tomato plants. It also increases productivity per plant and reduces the use of resources such as water and agricultural inputs.