Chemical Speciation Of Arsenic Research Articles

Microbial transformations of arsenic in lake ohakuri, New Zealand

The concentration and chemical speciation of arsenic in the waters and sediments of Lake Ohakuri, New Zealand were examined. Mixed microbial populations from the sediments were tested in vitro for their ability to mediate redox transformations of inorganic arsenic. Under aerobic conditions the mixed microbial cultures were found to be able to reduce arsenic(V) to arsenic(III) and also to oxidize arsenic(III) to arsenic(V). Under anaerobic conditions only reduction of arsenic(V) to arsenic(III) was observed. Four species of sediment fungi were isolated, grown aerobically and all were found capable of reducing arsenic(V) to arsenic(III). The role of microbial heterotrophs in determining the observed mobility and speciation of arsenic in Lake Ohakuri is discussed.

Metabolism of inorganic arsenic to organoarsenicals in rainbow trout ( Salmo gairdneri)

Chemical speciation of arsenic was examined by radioactive tracer and chromatographic techniques applied to muscle, liver, kidney, blood, bile, and urine from rainbow trout ( Salmo gairdneri) given an oral dose of 74As as arsenic acid. Conversion to organic forms of arsenic was rapid and extensive. The ratio of total organic to inorganic increased with time in all tissues, with the organic arsenic fraction accounting for about 50% at 6 hr and over 80% at 24 hr. An organoarsenic metabolite was shown by thin-layer chromatography to have the same R f as ethylarsenobetaine, and this compound accounted for the major portion of the total arsenic in all tissues including bile and urine sampled 24–96 hr postdose.

Changes in the chemical speciation of arsenic following ingestion by man.

The concentrations of four chemical species of arsenic in urine were observed with time, after ingestion of three different chemical species of arsenic. The arsenic-rich substances ingested, including arsenite-rich wine, arsenate-rich drinking water, and crab meat which contained organo-arsenic compounds. After ingestion of arsenite-rich wine, approximately 10% of the arsenic was excreted as arsenite, but the majority of the arsenic was methylated to methylarsonic acid and dimethylarsinic acid and excreted. After ingestion of arsenate-rich water, elevated levels of both arsenate and dimethylarsinic acid were observed. When crab meat was ingested, none of these four arsenic species were observed at elevated levels until the urine was heated in 2N NaOH. After the hot base digestion, high levels of dimethylarsinic acid were detected in these samples. The apparent biological half-lives were on the order of 10 hr for inorganic arsenic and 30 hr for the methylated arsenic forms.