Arsenic compounds transport

Melarsoprol, a trivalent organic melaminophenyl arsenic compound, kills intracerebral parasites of both T. brucei gambiense and T. brucei rhodesiense. Melarsoprol accumulates via an adenosine/adenine transporter in trypanosomes and is believed to inhibit glycolytic enzymes. Melarsoprol leads to a rapid lysis of trypanosomes. Melarsoprol is highly toxic to humans. 

Arsenic (mfz 75) is known to suffer from an isobaric interference caused by the presence of ArCl+ (m/z 75) during speciation analyses, particularly for samples that contain a high chloride salt content, e.g., sea water and urine. Several groups [37-39] used hydride generation to transform the arsenic compounds into their volatile hydrides before aspiration into the ICP. Selective transportation of the hydrides may thus be achieved by using a gas-liquid separator to eliminate the chloride interference (Fig. 10.6). 

Nowadays, it is well established that total arsenic concentrations provide no information about possible risks. The determination of individual molecular species of arsenic is absolutely necessary for risk assessment. Acute toxicities of the arsenic compounds are given in Table 1. Moreover, knowledge about the chemical form of an element provides useful information on its bioavailability, transport, and metabolism. 

Following the Armistice came disruption in transportation, shortages of resources (especially coal), the cancellation of contracts, and sharp reductions in chemical production. However, industrial capacity remained intact. Clearly, it was in Germany s interest to convert wartime facilities to peacetime production as quickly as possible. The chemical industry continued to enjoy its new-found independence from overseas nitrates. Moreover, many of its wartime products found peacetime uses - for example, phosgene, picric acid, and arsenic compounds were in demand as intermediates in the production of dyes, pharmaceuticals, and other commercial products. Almost immediately, this raised a question whether the Allies could deal with the contingencies of an industry whose technology was manifestly both military and civilian. 

During the 1960s, Americans lived in a lead-drenched society. They fueled their cars with leaded, antiknock gasoline. They ate food and their babies drank milk from lead-soldered cans. They stored drinking water in lead-lined tanks and transported it through lead or lead-soldered pipes. They squeezed toothpaste from lead-lined tubes and poured wine from bottles sealed with lead-covered corks. They picked fruit sprayed with lead arsenate pesticide and served it on lead-glazed dishes in houses painted and puttied with lead-based compounds. 

Anaerobic metabolism occnrs nnder conditions in which the diffusion rate is insufficient to meet the microbial demand, and alternative electron acceptors are needed. The type of anaerobic microbial reaction controls the redox potential (Eh), the denitrification process, reduction of Mu and SO , and the transformation of selenium and arsenate. Keeney (1983) emphasized that denitrification is the most significant anaerobic reaction occurring in the subsurface. Denitrification may be defined as the process in which N-oxides serve as terminal electron acceptors for respiratory electron transport (Firestone 1982), because nitrification and NOj" reduction to produce gaseous N-oxides. hi this case, a reduced electron-donating substrate enhances the formation of more N-oxides through numerous elechocarriers. Anaerobic conditions also lead to the transformation of organic toxic compounds (e.g., DDT) in many cases, these transformations are more rapid than under aerobic conditions. 

FishbeinL. 1981. Sources, transport and alterations of metal compounds An overview. I. Arsenic, beryllium, cadmium, chromium and nickel. Environ Health Perspect 40 43-64. 

The biological cycle of arsenic in the surface ocean involves the uptake of arsenate by plankton, the conversion of arsenate to a number of as yet unidentified organic compounds, and the release of arsenite and methylated species into the seawater. Biological de-methylation of the methylarsenicals and the oxidation of arsenite by as yet unknown mechanisms serve to regenerate arsenate. The concentrations of the arsenic species are then controlled primarily by the relative rates of biologically mediated reactions, superimposed on processes of physical transport and mixing. The... 

Major environmental trends that we see for land, air, water, and transportation of environmentally hazardous materials are shown in Box 9. These trends require that we get ahead of these issues and lead the chemical industry in the reduction of toxic metal (e.g., Sb, Sn, As) compounds, greenhouse gases, mercury emissions, and sulfur from gasoline and diesel, and find ways to control and sequester C02. Reduction of arsenic, as well as nitrates and ammonia, in drinking water is necessary. It is also imperative in these days of terrorism that we reduce transportation and storage of hazardous materials and continue our drive to develop inherently safer processes. 

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