Assessing the spatial distribution and ecologic and human health risks in mangrove soils polluted by Hg in northeastern Brazil.

The emission of mercury (Hg) by chlor-alkali plants can pollute soils and sediments, posing risks to the environment and human health. Mangrove ecosystems are particularly sensitive to Hg contamination. Here, we studied the Hg spatial distribution and associated human and ecologic risks in mangrove soils impacted by a chlor-alkali plant. Sixty-six samples of superficial soils were collected from the mangrove of the Botafogo River, Brazil. Mercury contents were determined and ecological and human health risks were estimated from the soil. The Hg contents exceeded the local Hg background by up to 180 times, indicating the substantial anthropic contribution that occurred in the area. Mercury concentrations followed a gradient as a function of the distance from the chlor-alkali plant, with an apparent contribution from the estuary's hydrodynamic regime. The ecological risk was considered high in all the soils evaluated, while the daily average exposure for humans, considering multiple exposure routes to soil, is below the tolerable dose recommended by the World Health Organization (WHO). However, the risk to human health was unacceptable in the estuary section closest to the plant, mainly for children. Vapor inhalation was the main route for estimating non-carcinogenic risk. The results of this study indicate a severe scenario of Hg pollution with unacceptable risks to the ecosystem and the health of human beings, especially of the communities that live from fishery and shellfish colletion and are exposed daily to soils polluted by mercury. Studies on the organomercurial species in the food chain and Hg levels in individuals living close to the estuary are warranted. This research is an important reference in the world regarding the contamination of mangrove areas by Hg.

Assessing human health risks and strategies for phytoremediation in soils contaminated with As, Cd, Pb, and Zn by slag disposal.

Soils impacted by metallurgy activities pose serious risks to the health of exposed populations, whether by ingestion of soil or contaminated food and water. The municipality of Santo Amaro, Bahia state, presents the most important case of human lead contamination in Brazil. It occurred because of inadequate slag disposal. The aims of this research were to: (i) determine the environmentally available concentrations and the distribution of As, Cd, Pb, and Zn in soil fractions; (ii) estimate the non-carcinogenic and carcinogenic risks of these elements for children; and (iii) to evaluate the use of corn (Zea mays) and castor bean (Ricinus communis) either for phytoextraction induced by chelating agents or phytostabilization. Our data demonstrated that the environmentally available concentrations of As, Cd, Pb, and Zn in soils surrounding the Pb smelting plant are among the highest that have been reported. Apart from Cd, sequential extraction demonstrated that most metals are in recalcitrant forms in the soil. However, the daily exposure of children to Pb, Zn, Cd, and As exceeded the acceptable daily intake as established by the World Health Organization. Non-carcinogenic risk modeling indicated probable adverse health effects from chronic exposure to soil Pb. The mean estimated time for remediation of the area using phytoextraction was high, ranging from 76 to 259 years; therefore, this is not a viable alternative for remediating soils in the studied area. However, good development in the contaminated soil along with restriction of the metal(oid) translocation to shoots enables castor bean to phytostabilize metal(oid)s. Additionally, castor bean cultivation may be an alternative for an economic return because of biofuel production.