Ricardo Perobelli Borba

Human and environmental contamination in the Iron Quadrangle, Brazil

Arsenic (As) exposure is a potential health risk to local populations around Au mining areas in southeastern Brazil. In April 1998, 126 schoolchildren, aged 9.8±1.12 years in the Minas Gerais mining districts of Nova Lima and Santa Barbara, had their spontaneous urine sampled. Toxicologically low Cd (0.04–0.35 μg L−1, mean 0.13 μg L−1), partly elevated Hg (0.1–16.5 μg L−1, mean 1.1 μg L−1), and generally elevated to high As concentrations (2.2–106 μg L−1, mean 25.7 μg L−1) were found. Twenty per cent of the total sample population showed elevated As concentrations where adverse health effects cannot be excluded on a long-term basis. To assess the potential sources particularly of As, a parallel study of surface waters, sediments, soils, and tailing materials was conducted. While Cd and Hg values were low in all these media, As concentrations in water (0.4–350 μg L−1; mean 30.5 μg L−1), in soils (200–860 mg kg−1), sediments (22–3200 mg kg−1, mean 350 mg kg−1), and tailings (300–21000 mg kg−1; mean 10500 mg kg−1) reveal high concentrations which may lead to an explanation for As pathways in the investigated areas.

Arsênio na água subterrânea em Ouro Preto e Mariana, Quadrilátero Ferrífero (MG)

In the Iron Quadrangle region the public supply of water is done mainly by the impound of water of watersheds. However, in some places, the population use spring water or ground water from closed mines for human consumption. The main natural sources of As in the Iron Quadrangle are related to the rocks that contain lode gold deposits. The antropic sources of As are contaminated refuse piles, soil, and sediment. It was found total As concentration varying from 2 to 2,980 µg/L and As3+ from 1 to 86 µg/L in water samples collected in underground gold mines, artesian wells, and springs in Ouro Preto and Mariana counties. Based on geological and hydrogeochemical studies of the occurrence of As in rocks and groundwater, it was found that the highest As concentrations occurred in aquifers hosted in carbonate sulphide rich rocks. The As monitoring in underground water should be done periodically, independent of its absence in a first instance, in wells and other groundwater caption sources that are used nowadays for public or private suppliers.

Water recovery from saline streams produced by electrodialysis

Advances in technologies to enable water reuse in industry have been the objective of many research efforts, mainly due to the need to reduce the use of natural resources and due to factors related to their availability. This paper evaluates the crystallization of salts from petrochemical saline waste to achieve zero water discharge by the recovery of water and dissolved salts as a solid mixture. In line with process symbiosis, the recovered water should be suitable for use as cooling water in heat exchangers. Vacuum evaporative crystallization, at the batch scale, was used to remove the salts present in the concentrated stream from reverse electrodialysis of pretreated wastewater by a biological process. The partition of organic compounds in the feed solution between the condensate and the mother liquor was obtained from measurements of the total organic carbon and total nitrogen in the solutions. The solid phases formed experimentally are compared with those predicted by chemical modelling by PHREEQC. The recovered water presented almost 50 times less total dissolved solids than the feed stream (from 2100 to 44 mg/L). Calcium sulphate hydrate, calcium sulphate and sodium chloride were the majority crystalline phases formed, in accordance with the modelling by PHREEQC.

Estudo da especiação de arsênio inorgânico e determinação de arsênio total no monitoramento ambiental da qualidade de águas subterrâneas

This work reports an alternative, fast and robust method, for the determination of total As, As(III) and As(V) by HG-AAS without the use of prereductants. The method is based on the different rates of arsine formation of the inorganic As species and the effect of As(III) in the signal obtained for total As. Groundwater and mineral spiked waters were used to sample preservation evaluation. The method was validated by the determination of As in SRM 1640 and used in the determination of total As and its inorganic species in groundwater samples collected from mines in the Iron Quadrangle - MG.