Kevin A. Francesconi

Arsenic species in an arsenic hyperaccumulating fern, Pityrogramma calomelanos: a potential phytoremediator of arsenic-contaminated soils

The fern Pityrogramma calomelanos is a hyperaccumulator of arsenic that grows readily on arsenic-contaminated soils in the Ron Phibun district of southern Thailand. P. calomelanos accumulates arsenic mostly in the fronds (up to 8350 microg As g(-1) dry mass) while the rhizoids contain the lowest concentrations of arsenic (88-310 microg As g(-1) dry mass). The arsenic species in aqueous extracts of the fern and soil were determined by high performance liquid chromatography coupled to an inductively coupled plasma mass spectrometer (HPLC-ICPMS) which served as an arsenic specific detector. Only a small part of the arsenic (6.1-12%) in soil was extracted into water, and most of this arsenic (> 97%) was present as arsenate. The arsenic in the fern rhizoids was approximately 60% water-extractable, 95% of which was present as arsenate. In contrast, arsenic in the fern fronds was readily extracted into water (86-93%) and was present mainly as arsenite (60-72%) with the remainder being arsenate. Methylarsonate and dimethylarsinate were detected as trace constituents in only two fern samples. Preliminary estimates of phytoremediation potential suggest that P. calomelanos might remove approximately 2% of the soil arsenic load per year. With due consideration to the type of arsenic compounds present in the fern, and their water-solubility, the option of disposing high arsenic ferns at sea is raised for discussion.

The potential of Thai indigenous plant species for the phytoremediation of arsenic contaminated land.

To assess the potential of the native plant species for phytoremediation, plant and soil samples were collected from two areas in Thailand that have histories of arsenic pollution from mine tailings. The areas were the Ron Phibun District (Nakorn Si Thammarat province) and Bannang Sata District (Yala province), and samples were taken in 1998 and 1999 and analysed for total arsenic by atomic absorption spectrophotometry. Arsenic concentrations in soil ranged from 21 to 14,000 microg g(-1) in Ron Phibun, and from 540 to 16,000 microg g(-1) in Bannang Sata. The criteria used for selecting plants for phytoremediation were: high As tolerance, high bioaccumulation factor, short life cycle, high propagation rate, wide distribution and large shoot biomass. Of 36 plant species, only two species of ferns (Pityrogramma calomelanos and Pteris vittata), a herb (Mimosa pudica), and a shrub (Melastoma malabrathricum), seemed suitable for phytoremediation. The ferns were by far the most proficient plants at accumulating arsenic from soil, attaining concentrations of up to 8350 microg g(-1) (dry mass) in the frond.

MERCURY CONTAMINATION IN A SEMI-ENCLOSED MARINE EMBAYMENT : ORGANIC AND INORGANIC MERCURY CONTENT OF BIOTA, AND FACTORS INFLUENCING MERCURY LEVELS IN FISH

Princess Royal Harbour is a semi-enclosed marine embayment which received mercury-contaminated industrial effluent from a superphosphate plant over a 30-year period. Although the levels of mercury in the sediments were not particularly high (≤ 1·7mg kg−1), most fish taken from the harbour contained very high levels of mercury (up to 10·3 mg kg−1). The organic mercury content of biota within the harbour was related to the trophic level of the organism. The wide range in mercury levels in fish of different species was largely explained by their diets and suggested that direct uptake from water was not a significant source of mercury for these fish.

The marine polychaete Arenicola marina: its unusual arsenic compound pattern and its uptake of arsenate from seawater

Arsenic compounds in the marine polychaete Arenicola marina collected from Odense Fjord, Denmark were determined by HPLC-ICPMS. In contrast to most other marine animals, A. marina contained most of its water soluble arsenic as inorganic forms, arsenite (58%) and arsenate (16%), and arsenobetaine was present as a minor constituent (6%) only. Other arsenic compounds detected in A. marina were dimethylarsinate (4%), two arsenosugars (1 and 3%), tetramethylarsonium ion (1.5%), and arsenocholine (<1%). A new arsenobetaine -trimethylarsoniopropionate-previously only reported in fish, was also present at trace levels (<1%), and an unknown anionic arsenical (approximately 10%) remains unidentified. When A. marina was exposed in laboratory experiments to different concentrations of arsenate in seawater (10, 50. 100, 500 and 1000 microg As 1(-1)) the polychaetes accumulated arsenic in a dose dependent. non-linear manner. Most of the accumulated arsenic was biotransformed to arsenite and dimethylarsinate. with the remainder being accumulated as unchanged arsenate. None of the other arsenic compounds naturally present in A. marina increased in concentration following arsenate exposure.

A novel arsenic containing riboside (arsenosugar) in three species of gastropod

Abstract Arsenic compounds in three marine gastropods ( Thais bitubercularis, Thais distinguenda, Morula musiva ) from Phuket, Thailand were examined by HPLC using ICP-MS as an arsenic specific detector. Aqueous methanol treatment of the freeze-dried samples (initially 112–339 μg As g −1 dry mass) extracted >96% of the total arsenic. HPLC-ICP-MS of the extracts demonstrated the presence of arsenobetaine (93–95% of total extractable arsenic), arsenocholine (3.1–4.6%), tetramethylarsonium ion (0.21–2.2%), two unknown arsenic compounds (each approx. 0.1%), and an unresolved mixture of arsenic compounds (∼1%). One of the unknowns was identified as a new natural product, the arsenosugar 2′,3′-dihydroxypropyl 5-deoxy-5-trimethylarsonioriboside, by co-chromatography with synthetic material. The presence of these arsenic compounds in the gastropods is consistent with the hypothesis that trimethylated arsenosugars are transformed into arsenobetaine via arsenocholine within animals.

Liquid chromatography electrospray mass spectrometry with variable fragmentor voltages gives simultaneous elemental and molecular detection of arsenic compounds

A single quadrupole high performance liquid chromatography electrospray mass spectrometry system with a variable fragmentor voltage facility was used in the positive ion mode for simultaneous recording of elemental and molecular mass spectral data for arsenic compounds. The method was applicable to the seven organoarsenic compounds tested: four arsenic-containing carbohydrates (arsenosugars), a quaternary arsonium compound (arsenobetaine), dimethylarsinic acid, and dimethylarsinoylacetic acid. It was not suitable for the two inorganic arsenic species arsenite and arsenate. In the case of arsenosugars, qualifying ion data for a characteristic common fragment (m/z 237) was also simultaneously obtained. The method was used to identify and quantify the major arsenosugars in crude extracts of two brown algae.

Accumulation and elimination of dietary arsenobetaine in two species of fish, Atlantic salmon (Salmo salar L.) and Atlantic cod (Gadus morhua L.)

Despite the fact that marine fish contain relatively high concentrations of the naturally occurring arsenic compound arsenobetaine, little is known about the disposition of arsenobetaine in fish. We investigated the accumulation, distribution, and elimination of dietary arsenobetaine in Atlantic salmon (Salmo salar L.) and Atlantic cod (Gadus morhua L.), with the focus on muscle, liver, and kidney tissues. The fish were exposed to dietary arsenobetaine (24.7 +/- 0.6 microg As/g feed) for three months, followed by a three-month depuration period. The two species showed marked differences in the accumulation and elimination of arsenobetaine. Total arsenic concentrations in Atlantic salmon increased significantly in muscle, liver, and kidney, whereas in Atlantic cod, a significant increase in total arsenic concentration was observed only in muscle. Elimination kinetics in muscle were distinct between the two species, with elimination half-lives from muscle tissue estimated at approximately 77 d in Atlantic cod and 37 d in Atlantic salmon, resulting in an absorption efficiency approximately twofold higher in Atlantic cod (15 +/- 1%) compared to that in Atlantic salmon (8 +/- 1%). The differences in arsenobetaine disposition studied in Atlantic salmon and Atlantic cod contribute to explain the differences in arsenic levels observed among marine fish.

Long-term study of mercury concentrations in fish following cessation of a mercury-containing discharge

Abstract Mercury-contaminated industrial effluent was discharged over a 30-year period into Princess Royal Harbour, a marine embayment on the south coast of Western Australia. The discharge of effluent was stopped in 1984 and most fish taken from the harbour at that time contained concentrations of Hg in their muscle tissue which exceeded the maximum permitted concentration (0.5 mg kg −1 ) set by Australian health authorities. To allay human health concerns, the contaminated portion of the harbour was closed to all forms of commercial and recreational fishing in 1984. The course of Hg contamination following cessation of the effluent discharge was monitored by determining Hg concentrations in the muscle tissue of eight teleost fish species, namely cobbler ( Cnidoglanis macrocephalus ), rock flathead ( Platycephalus laevigatus ), striped trumpeter ( Pelates sexlineatus ), King George whiting ( Sillaginodes punctata ), Australian herring ( Arripis georgianus ), brown-spotted wrasse ( Pseudolabrus parilus ), spiny-tailed leatherjacket ( Bigener brownii ) and six-spined leatherjacket ( Meuschenia freycineti ), sampled near the effluent outfall on 14 occasions from 1984 to 1993. Mercury concentration showed a significant positive relationship with length of fish for five of the species and a significant negative relationship with length for two species. Four species showed significant differences in Hg concentration depending on season (summer vs winter); summer concentrations were generally higher than those in winter. The Hg concentrations decreased with time and were about 50% of their initial values by 1993. In general, fish Hg levels had decreased to below the maximum permitted concentration by 1991 and the closed portion of the harbour was reopened in 1992. For most species, however, the rate of reduction in Hg concentration was less in the latter part of the study. The data suggest that future reductions in Hg concentrations in fish may be less than those achieved in the first 10 years, and that for some species Hg concentrations could remain elevated for many years.

Uptake and transformation of arsenosugars in the shrimp Crangon crangon

The possible role of arsenosugars as precursors to arsenobetaine was investigated by feeding pure arsenosugar compounds to the shrimp, Crangon crangon, and monitoring the arsenic metabolites in muscle, midgut gland, gills, and ‘remainder’ tissues by HPLC–ICP MS. Control shrimps contained arsenobetaine (ca 90% of the total As) as the major arsenic compound in all four tissues, and traces of tetramethylarsonium ion and two arsenosugars were also present. Shrimps accumulated only 0.9% of a dimethylated arsenosugar, mostly as unchanged compound, and conversion into arsenobetaine could not be detected. Dimethylarsinate and possibly dimethylarsinoylethanol were present as minor metabolites. Shrimps accumulated 4.2% of a trimethylated arsenosugar, and converted about half into arsenobetaine. The remainder of the arsenic was present as unchanged arsenosugar and several minor unidentified metabolites. The overall accumulation of arsenobetaine from ingested trimethylated arsenosugar was only about 2%, whereas shrimps fed arsenobetaine retained 57% of the dose. The undetectable (dimethylated) to low (trimethylated) conversion of the arsenosugars into arsenobetaine suggests that these compounds do not represent a major source of arsenobetaine for wild Crangon. Copyright

A new arsenobetaine from marine organisms identified by liquid chromatography–mass spectrometry

A new arsenic-containing betaine, trimethyl(2-carboxy- ethyl)arsonium inner salt 2, has been identified in fish muscle tissue by liquid chromatography–mass spectrometry.