ENVR 13 |
| Kong-Hwa Chiu and Shaofen Joanna Wang. |
| Arsenic (As, Z = 33) is a naturally occurring and ubiquitous element found in the Earth's crust. It is classically considered as a soft metal and shares many of its toxicity effects. Contamination of groundwater with arsenic is a global environmental problem because arsenic can enter groundwater systems from weathering and leaching of arsenic minerals in rocks and soil. The affinity of arsenic for sulfur is revealed in many natural arsenic-containing sulfide minerals, for example, As4S6 (orpiment). This affinity also accounts for the toxicity of arsenite As(III) compounds through its interactions with protein thiols in the human body. Trivalent arsenic is extremely poisonous because it can bind strongly to sulfur groups in amino acids, the building blocks of protein as illustrated for cystine in global groundwater contamination by arsenic and related health problems and the controversies around government regulations of arsenic in drinking water. Ancient Chinese used arsenic trioxide (pee-song) to kill rats and fungi in rice fields to protect and increase crop yield; “peesong” was also used to kill people in some well-known murder cases described in the Chinese classical literature. The first well-documented, large-scale arsenic contamination of deep well waters and its correlation to “Blackfoot Disease” (BFD) occurred nearly half a century ago in Taiwan. The symptoms of BFD start with spotted discoloration on the skin of extremities, especially on the feet. The spots change from white to brown and eventually to black, hence, the name. BFD area were inorganic arsenic species As(III) and As(V), with an average ratio of As(III)/As(V) of about 2.6. The individual wells showed a variation of As(III)/As(V) ratio from 1.1 to 5.2. Monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) were below the detection limit; insoluble suspended arsenic accounted for about 3% of the total arsenic in the well water. |
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Occurrence, Chemistry, Toxicity and Remediation of Arsenic
8:00 AM-11:00 AM, Sunday, 26 March 2006 Georgia World Congress Center -- B218, Oral
Division of Environmental Chemistry |