RESUMO
Ethnic groups from the Atacama Desert (known as Atacameños) have been exposed to natural arsenic pollution for over 5000 years. This work presents an integral study that characterizes arsenic species in water used for human consumption. It also describes the metabolism and arsenic elimination through urine in a chronically exposed population in northern Chile. In this region, water contained total arsenic concentrations up to 1250 µg L(-1), which was almost exclusively As(V). It is also important that this water was ingested directly from natural water sources without any treatment. The ingested arsenic was extensively methylated. In urine 93% of the arsenic was found as methylated arsenic species, such as monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. The original ingested inorganic species [As(V)], represent less than 1% of the total urinary arsenic. Methylation activity among individuals can be assessed by measuring primary [inorganic As/methylated As] and secondary methylation [MMA/DMA] indexes. Both methylation indexes were 0.06, indicating a high biological converting capability of As(V) into MMA and then MMA into DMA, compared with the control population and other arsenic exposed populations previously reported.
Assuntos
Arsênio/urina , Água Potável/química , Poluentes Químicos da Água/urina , Arsênio/toxicidade , Arsenicais/urina , Ácido Cacodílico/urina , Chile , Água Potável/normas , Monitoramento Ambiental , Etnicidade , Humanos , Metilação , Poluentes Químicos da Água/toxicidade , Qualidade da ÁguaRESUMO
This article presents experimental results on 47 µmol L(-1) sulfathiazole (STZ) degradation by Fenton and photo-Fenton reactions using multivariate analysis. The optimal experimental conditions for reactions were obtained by Response Surface Methodology (RSM). In the case of the Fenton reactions there were 192 µmol L(-1) ferrous ions (Fe(II)) and 1856 µmol L(-1) hydrogen peroxide (H2O2), as compared with 157 µmol L(-1) (Fe(II)) and 1219 µmol L(-1) (H2O2) for photo-Fenton reactions. Under these conditions, around 90% of STZ degradation were achieved after 8 minutes treatment by Fenton and photo-Fenton reactions, respectively. Moreover, a marked difference was observed in the total organic carbon (TOC) removal after 60-min treatment, achieving 30% and 75% for the Fenton and photo-Fenton reactions, respectively. Acetic, maleic, succinic and oxamic acids could be identified as main Fenton oxidation intermediates. A similar pattern was found in the case of photo-Fenton reaction, including the presence of oxalic acid and ammonia at short periods of irradiation with UV-A. The calculated values of Average Oxidation State (AOS) corroborate the formation of oxidized products from the initial steps of the reaction.