A study of the routes of contamination by lead and cadmium in Santo Amaro, Brazil

Abstract

The problem of contamination by cadmium and lead in Santo Amaro, Brazil, has been studied since 1970 and the severity of this contamination case has been demonstrated by many authors. This study evaluates the persistence of the superficial soil contamination around the metallurgical plant and attempts to correlate the lead and cadmium concentrations to the past atmospheric emissions from the lead plant and with the presence of lead debris under urban road surface and in the backyards of homes. Past emissions still play an important role in soil contamination. In areas without debris, about 30% of the soil samples had lead concentrations above the agricultural use limit of 180 parts per million (ppm) (according to CONAMA 420, 2009), 20% of the samples had concentrations above 300 ppm (maximum for residential use) and 9.6% of the samples had concentrations above 900 ppm (maximum for industrial use). These concentrations are higher cldse to the chimney of the metallurgical plant. An average lead concentration of 1316 ppm was found in the backyard samples. About 80% of the houses had lead concentrations above 300 ppm and about 50% of the samples had values above 900 ppm, indicating the importance of the lead debris in the contamination scenario. Although a matter of concern, the cadmium concentrations seem to be less problematic than lead at the present time, probably due to the higher mobility of cadmium. The cadmium concentrations in the atmospheric dispersion and backyard samples showed similar trends, while the influence of the lead debris on the soil contamination is less evident.

Soil Contamination by a Lead Smelter in Brazil in the View of the Local Residents

“…The metal mobility in the soil can also be affected by the content of organic matter, clay, iron, and manganese. Fortunately, the pH values higher than 5 favors lead immobilization in clay and silt soils [4]. Lower pH values tend to increase bioavailability and mobility of most metals in soil [5].…”

“…Lower pH values tend to increase bioavailability and mobility of most metals in soil [5]. Studies on the stability and leaching of some contaminants in the soil of Santo Amaro, especially Pb, Zn, and Cd, have been developed by different researchers during the last years [4,6,7]. However, there was a disagreement between the results of these researchers.…”

Bioavailability of lead using chemical extractants in soil treated with humic acids and activated carbon

“…Provocando a maior contaminação por Pb do mundo, desta forma, como consequência da exposição à contaminação houve a manifestação de diversos problemas de saúde entre a população e antigos funcionários da usina, como casos de câncer e defeitos congênitos. Machado et al (2013) avaliaram a contaminação remanescente no sítio urbano e no entorno da cidade de Santo Amaro da Purificação-BA, buscando identificar as contribuições provenientes da deposição de escória e das antigas emissões atmosféricas geradas pela indústria nos valores de concentração de Pb e Cd detectados no solo superficial; observaram valores médios de 1.086 e 10,14 mg kg -1 de Pb e Cd, respectivamente.…”

Lead concentrations in whole blood, serum, saliva and house dust in samples collected at two time points (12 months apart) in Santo Amaro, BA, Brazil

“…A lead smelter operating from 1956 to 1993 contaminated this city (Carvalho et al, 2003;Machado et al, 2013). This company was a subsidiary of a French company (Penarroya Oxide) and was initially called COBRAC; its name was changed to PLUMBUM Co in the last years of operation.…”

“…According to Machado et al (2013) analysis performed in 223 superficial soil samples from Rui Barbosa Street, in the metallurgy neighborhood, indicated that approximately 80% of them presented values above the lead limits established by CONAMA No. 420/2009 (Brazilian Resolution on soil elements accepted limits) for residential areas (300 mg/kg).…”