Paul Andrewes

Arsenic in the Meager Creek hot springs environment, British Columbia, Canada

Levels of arsenic in water from Meager Creek hot springs, British Columbia, Canada, were found to be naturally elevated. Biota including microbial mats, green algae, sedge, cedar, fleabane, monkey flower, moss, mushrooms and lichens, that were expected to be impacted by the water, were analyzed for total levels of arsenic and for arsenic species. The major arsenic species extracted from all samples were arsenate and arsenite, which are toxic forms of arsenic. Additionally, small amounts of arsenosugars X and XI were detected in microbial mats and green algae, implying that cyanobacteria/bacteria, and possibly green algae are capable of synthesizing arsenosugars from arsenate. Low to trace amounts of arsenosugars X and XI were detected in lichens and the fungus Tarzetta cupularis. A large fraction (on average, greater than 50%) of arsenic was not extracted by using methanol/water (1:1) and the chemical and toxicological significance of this arsenic remains unknown.

The production of methylated organoantimony compounds by Scopulariopsis brevicaulis

Cultures of the fungus Scopulariopsis brevicaulis were grown in antimony-rich media. Although volatile compounds of other elements were readily detected in the culture headspace, volatile antimony compounds were formed irreproducibly and at only ultratrace levels. In order to monitor the media for nonvolatile methylantimony compounds, a method of sample preparation was developed, based on solid-phase extraction. This enabled the separation of large quantities of soluble inorganic antimony species from trace amounts of organoantimony compounds before speciation by HG–GC–AAS. By this methodology methylated antimony compounds were detected at concentrations of 0.8– 7.1 µg Sbl−1 in all media in which S. brevicaulis was grown in the presence of antimony(III) compounds. These methylantimony species were not detected in any of the nonliving or medium-only controls. Methylated compounds were not detected where S. brevicaulis was grown in the presence of antimony(V) compounds. This is the first study to show that antimony(III) compounds are biomethylated by S. brevicaulis under aerobic-only growth conditions. Copyright

Antimony biomethylation by Scopulariopsis brevicaulis: characterization of intermediates and the methyl donor.

The filamentous fungus Scopulariopsis brevicaulis biomethylates inorganic antimony(III) compounds to trimethylstibine, that can be detected in culture headspace gases. Dimethylantimony and trimethylantimony species have been detected in the medium of these cultures, but the origin of these species was controversial. We now show that the dimethylantimony species is a true intermediate on the pathway to trimethylstibine (rather than arising from trimethylstibine oxidation or as an analytical artifact) because no dimethylantimony species are formed on trimethylstibine oxidation, as determined by using HG-GC-AAS. Furthermore, the dimethylantimony and trimethylantimony species can be separated, by using anion exchange chromatography, and so the dimethylantimony species is not an analytical artifact, formed during the hydride generation process. The antimony biomethylation mechanism was further probed by measuring incorporation of the methyl group, from 13CD3-L-methionine and CD3-D-methionine, into methylantimony species and, for comparison, into methylarsenic species. The percentage incorporation of the labeled methyl group into methylarsenic and methylantimony species was not significantly different. The incorporation from 13CD3-L-methionine was 54% and 47% for antimony and arsenic, respectively. The incorporation from CD3-D-methionine was 20% and 16% for antimony and arsenic, respectively. It appears that the biomethylation of arsenic and antimony occur by very similar, perhaps identical, mechanisms.

Antimony Species in Environmental Samples

Abstract Antimony was extracted from environmental biota samples from Yellowknife, NWT and Meager Creek, BC, Canada. Extraction efficiencies ranged from 0.7 to 37% for all samples except for a cattail sample, from which 95% of antimony was extracted. Speciation analysis was carried out by using hydride generation-gas chromatography-atomic absorption spectrometry (HG-GC-AAS). The major antimony species in all samples, including biota extracts and water, was Sb (V). Sb (III) and methylated antimony species were detected in some samples as well. The presence of methylated antimony species in moss from Yellowknife and a water sample from Yellowknife was confirmed by using HG-GC-AAS at a second absorption wavelength, increasing the likelihood that the peaks obtained are due to the presence of antimony compounds. A headspace HG-GC-mass spectrometric (MS) method was developed for the speciation of antimony compounds and this was used to successfully confirm methylantimony species in the headspace following HG of extracts of moss and snail samples from Yellowknife.

Methylantimony compound formation in the medium of Scopulariopsis brevicaulis cultures: 13CD3-L-methionine as a source of the methyl group

The filamentous fungus Scopulariopsis brevicaulis produces nonvolatile methylantimony compounds (found in the medium) when grown in antimony(III)-rich medium. To investigate the methyl source, 13CD3-labelled L-methionine was added to the growth medium. After one month sodium borohydride reduction of media samples produced dimethylstibine and trimethylstibine. The methylstibines were separated on a packed GC column and obtained as gaseous fractions. Analysis of the methylstibines, in the gaseous fractions, by CGC–MS (ion-trap) established 13CD3 incorporation in both the trimethyl-and dimethyl-antimony compounds. Copyright

Confirmation of the aerobic production of trimethylstibine by Scopulariopsis brevicaulis

The filamentous fungus Scopulariopsis brevicaulis produces volatile trimethylstibine, found in the culture headspace, when grown in an antimony(III)-rich medium under aerobic conditions. The trimethylstibine was purged from cultures using a continuous flow of compressed air and trapped in a U-shaped tube containing Supelcoport SP 2100 at −78 °C. The trap contents were determined by using GC–ICP–MS methodology. Typically between 60 and 500 pg of trimethylstibine was trapped during sampling (12 h) from cultures containing 1000 g Sb ml−1 as potassium antimony tartrate. The total production of trimethylstibine over 18 days of growth was estimated at 10 ng. Trimethylarsine was produced in greater quantities than trimethylstibine, even though no arsenic compounds were added to the medium. Copyright

Interaction of Scopulariopsis brevicaulis, and other microorganisms, with 10,10′-oxybisphenoxarsine (OBPA)

The fungicide 10,10′-oxybisphenoxarsine (OBPA) is widely used in consumer products, such as shower curtains, wall coverings and carpets. A possibility exists that microorganisms might be able to degrade OBPA to produce volatile trimethylarsine. If this did occur, then in certain situations enough trimethylarsine might be produced to be a hazard. In this study, we cultured microorganisms in medium containing OBPA, and examined the medium for possible degradation products. We used Scopulariopsis brevicaulis in one experiment, because this microorganism is known for its ability to biomethylate arsenic. OBPA-tolerant microorganisms, isolated from a soil contaminated with arylarsenic compounds, were used in a second series of experiments. We found no evidence of complete microbiological cleavage of aryl–arsenic bonds in any of the cultures, and no significant amount of trimethylarsine was detected in the headspace of S. brevicaulis cultures. Copyright

Solidification/Stabilization of Adamsite and Lewisite in Cement and the Stability of Arylarsenicals in Soil

Adamsite 1 (DM) and Lewisite (L) 6 (Figure 1) are two arsenic based toxic chemical agents that are stored in large quantities in some countries in the world. Some of the methods that have been suggested for the destruction of these chemicals are shown in Figure 2 and 3 (1) (some of these are rather speculative: the route to As2S3,Figure 3seem a little strange). The routes highlighted in Figure 2 have been adopted by Russian experts for development and field use. The hydrolysis reaction is to be used for Lewisite destruction and the polymerization reactions are likely to be used in the decomposition of Lewisite/Mustard mixtures. Many of the proposed technologies ultimately are faced with the problem of disposal of arsenic. For example, incineration undoubtedly destroys the agent but the arsenic is concentrated as the oxide particulate in the flue gas and must be carefully collected for disposal by other means. This means that a chemical weapons problem still remains an environmental problem.