William A. Maher

Bioaccumulation and biomagnification of mercury in Lake Murray, Papua New Guinea

The bioaccumulation of mercury in the food webs incorporating the major piscivorous fish species of Lake Murray, Papua New Guinea, has been characterised. Methylmercury concentrations increased with trophic level and the proportion of total mercury present as methylmercury increased from <1% in plants to 94% in piscivorous fish. Methylmercury bioaccumulation factors (BAFs) were similar to those found in temperate environments, with a typical increase of 1 log unit between planktivore and piscivore trophic levels. The greatest bioaccumulation of methylmercury occurred between seston and the water column (log BAF of 5.36). The bioaccumulation of mercury to levels of regula tory concern by the lake’s piscivores was attributable to the biomagnification power of the plankton-based food chain comprising four trophic levels (phytoplankton, zooplankton, planktivore, piscivore) rather than any elevated concentra tions of mercury in waters or sediments. The methylmercury concentrations of individual piscivores were positively correlated with both trophic position, as indicated by d15N measurements, and fish size. Stable-isotope measurements were used to identify fish species where dietary changes occurring with age significantly augmented age-related bioaccumulation of mercury. Résumé: La bioaccumulation du mercure a été étudiée dans le réseau alimentaire reliant les principales espèces de poissons piscivores du lac Murray en Papouasie-Nouvelle-Guinée. Les concentrations de méthylmercure croissent avec le niveau trophique et le pourcentage du mercure total présent sous la forme méthylée augmente de <1% chez les plantes à 94% chez les poissons piscivores. Les facteurs de bioaccumalation du méthylmercure (BAFs) sont semblables à ceux que l’on retrouve dans les milieux tempérés et i l y a typiquement une augmentation d’une unité logarithmique entre les niveaux trophiques planctonophage et piscivore. La bioaccumulation la plus considérable a lieu entre le seston et la colonne d’eau (log BAF de 5,36). La bioaccumulation du mercure à des niveaux inquiétants (d’après les normes actuelles) par les piscivores du lac est causée par le pouvoir de bioamplification de la chaîne alimentaire à base de plancton qui couvre quatre niveaux (phytoplanctonique, zooplanctonique, planctonophage, piscivore) plutôt qu’à une augmentation des concentrations de mercure dans les eaux ou dans les sédiments. Les concentrations de méthylmercure chez les différents piscivores sont en corrélation positive à la fois avec leur position trophique, telle que déterminée par les mesures de d15N, et avec leur taille. Les analyses à l’aide d’isotopes stables ont permis de reconnaître les espèces de poissons chez lesquelles des changements de régime alimentaire au cours de la vie augmentent significativement la bioaccumulation du mercure reliée à l’âge. [Traduit par la Rédaction] Bowles et al. 897

Polycyclic aromatic hydrocarbons in nearshore marine sediments of Australia

The occurrence and fate of polycyclic aromatic hydrocarbons (PAH) in nearshore marine sediments of Australia is discussed. Available information indicates that PAH are accumulating in the sediments and organisms of estuaries and harbours with both highly urbanized/industrialized and non-urban catchments. PAH levels in polluted sediments are similar to those of grossly polluted areas of Japan, North America and Europe, however PAH sources cannot be identified from the information available. PAH appear to persist in reducing environments, while in relatively pristine environments that have been previously exposed to PAH, conditions are probably favourable for the aerobic degradation of PAH by microorganisms.

A microwave-assisted sequential extraction of water and dilute acid soluble arsenic species from marine plant and animal tissues

This paper describes the use of dilute nitric acid for the extraction and quantification of arsenic species. A number of extractants (e.g. water, 1.5M orthophosphoric acid, methanol-water and dilute nitric acid) were tested for the extraction of arsenic from marine biological samples, such as plants that have proved difficult to quantitatively extract. Dilute 2% (v/v) nitric acid was found to give the highest recoveries of arsenic overall and was chosen for further optimisation. The optimal extraction conditions for arsenic were 2% (v/v) HNO(3), 6 min(-1), 90 degrees C. Arsenic species were found to be stable under the optimised conditions with the exception of the arsenoriboses which degraded to a product eluting at the same retention time as glycerol arsenoribose. Good agreement was found between the 2% (v/v) HNO(3) extraction and the methanol-water extraction for the certified reference material DORM-2 (AB 17.1 and 16.2microg g(-1), respectively, and TETRA 0.27 and 0.25microg g(-1), respectively), which were in close agreement with the certified concentrations of AB 16.4+/-1.1microg g(-1) and TETRA 0.248+/-0.054microg g(-1). To preserve the integrity of arsenic species, a sequential extraction technique was developed where the previously methanol-water extracted pellet was further extracted with 2% (v/v) HNO(3) under the optimised conditions. Increases in arsenic recoveries between 13% and 36% were found and speciation of this faction revealed that only inorganic and simple methylated species were extracted.

Determination of phosphorus in aqueous solution via formation of the phosphoantimonylmolybdenum blue complex. Re-examination of optimum conditions for the analysis of phosphate

This paper describes an investigation of the conditions affecting the determination of phosphate using the reduced phosphoantimonylmolybdic acid method. The aim was to develop a determination method with faster kinetics than the original procedure of Murphy and Riley, for automation using flow-injection analysis. Optimum colour formation was found to occur at [H+ ] / [MOO:-] ratios between SW30 at all pH values tested (0.36-1.06). The maximum rate of formation occurs at a [H’ ] / [MOO:- ] ratio of 70 within a pH range of 0.574.88 when an antimony concentration greater than 0.06 mM and ascorbic acid concentration greater than 0.009 M in the final solution are used. Full colour development occurs within 0.8-l min. The ascorbic acid reagent was found to be stable for 30 days. The results of the study indicated that by suitable selection of reagent conditions, rapid chromophore development can be achieved.

Arsenic concentrations and speciation in the tissues and blood of sea mullet (Mugil cephalus) from Lake Macquarie NSW, Australia

Total arsenic concentrations and species were measured in the tissues and blood of the mullet Mugil cephalus. Arsenic concentrations ranged from 0.54 μg/g dry mass in the gill tissue to 19.2 μg/g dry mass in liver tissue. The concentrations of arsenic in liver tissues were found to be significantly greater (P>0.01) than in other tissues. Significant correlations exist between arsenic concentrations in all tissues. There was no significant difference (P>0.05) in arsenic concentrations between male and female fish. Age was found not to influence arsenic concentration. Significant regressions of arsenic concentration against mass were found for stomach (r2=0.23, P<0.01), gill (r2=0.143, P<0.05), intestine (r2=0.138, P<0.05) and gonad tissues (r2=0.13, P<0.05). Most tissues and blood contained large percentages of arsenobetaine (35%–100%) and with the exception of muscle and gonad tissues, dimethylarsinic acid (7%–62%). Smaller percentages of trimethylarsine oxide (TMAO) (4%–14%) were found in stomach, intestine and kidney tissues; arsenate (1%–6%) in stomach, intestine, liver, gonad tissues and blood and arsenocholine (2%–3%) in all tissues except muscle. Traces of arsenic sugars were found in stomach, intestine, kidney and gonad tissues. The species of arsenic found in tissues and blood can be explained by the ingestion and degradation of organic arsenic compounds found in fauna and flora consumed by mullet. The conversion of inorganic arsenic obtained through ingestion of sediment to organic arsenic compounds by microbial processes in the digestive system and enzymes in the liver may also be occurring.

Measurement of arsenic species in marine macroalgae by microwave-assisted extraction and high performance liquid chromatography-inductively coupled plasma mass spectrometry

The measurement of arsenic species (arsenoribosides, arsenate, dimethyl arsenic and monomethyl arsenic) in marine macroalgae by microwave-assisted extraction and HPLC–ICP-MS is described. The extraction of arsenic from three different macroalgae classes was optimised using a chemometric approach, with solvent composition and sample mass being the two significant factors influencing the extraction of arsenic. Extraction temperature and extraction time did not significantly influence the extraction of arsenic from macroalgae. The optimised conditions for arsenic extraction (methanol (%)) were: 56% for phaeophyta, 66% for rhodophyta and 78% for chlorophyta, (sample mass in 10 ml of solvent) 0.05 g for phaeophyta, 0.07 g for rhodophyta and 0.08 g for chlorophyta. When two extractions were used, the percentage of arsenic extracted from macroalgae was greater than 88%. Unambiguous separation and identification of three arsenoribosides (phosphate-, sulfonate- and sulfate-arsenoriboside) was achieved by chromatographing extracts on a Hamilton PRP X-100 anion exchange column with ammonium phosphate buffer as the mobile phase at a pH of 9.2. The unambiguous separation and identification of the glycerol-arsenoriboside was achieved by chromatographing extracts on a Supelcosil SCX cation exchange column with a pyridine–formic acid buffer as the mobile phase at a pH of 2.6.

Procedures for the storage and digestion of natural waters for the determination of filterable reactive phosphorus, total filterable phosphorus and total phosphorus

Abstract An overview of the forms of phosphorus species likely to be encountered in natural waters and the implications for the measurement of filterable and total phosphorus is given. Procedures reported in the literature for the storage and digestion of water samples for filterable reactive phosphorus (FRP), total filterable phosphorus (TFP) and total phosphorus (TP) measurements are summarised and the advantages and limitations of methods discussed. Water samples for FRP and TFP measurements need to be filtered immediately on collection as exchange on and off particles may occur in the sample container. Slow freezing of filtered or turbid water samples in acid washed low density polyethylene bottles appears to be satisfactory for the long term storage (years) of a variety of water sample types. Storage of water samples at room temperature or refrigeration (1–5°C) with a preservative is suitable only for short term storage (days-months). If water samples contain Batch digestion of samples with alkaline or acid peroxodisulphate using autoclave or microwave heating offers the advantages of ease, simplicity and precision. Good recoveries of phosphorus from a range of phosphorus compounds containing P–O–P, C–O–P and C–P bonds expected in natural waters have been reported. If turbid samples are to be analysed, caution must be exercised to ensure that the carbon or suspended solids concentration does not exceed the capacity of the digestion procedure to oxidise the carbon present and release occluded phosphorus from particulate materials. Better recoveries of phosphorus from turbid water samples are achieved using microwave heating with closed vessels, probably because of the higher temperatures and pressures generated. The use of on-line heating (microwave, thermal induced) coupled with flow injection analysis and using peroxodisulphate or an oxidising acid mixture should also allow the automation of TFP and TP measurements. Reliable procedures for the removal of unwanted particulate material prior to or after the digestion step need to be developed.

Measurement of water-soluble arsenic species in freeze-dried marine animal tissues by microwave-assisted extraction and HPLC-ICP-MS

A microwave-assisted procedure is outlined for the extraction of water-soluble arsenic in freeze-dried marine animal tissues. The optimum microwave-assisted conditions were three extractions with 50% (v/v) methanol–water at 70 to 75 °C for 5 min. Quantitative extraction of arsenic in the water-soluble fraction of dogfish muscle (Dorm-2: 103 ± 2%) is consistent with that reported in the literature for this tissue. Lower extraction efficiencies for arsenic were found for liver (e.g. Dolt-1: 75 ± 5%; Pomatomus saltatrix: 80%), digestive (e.g. Tort-2: 92 ± 5%; Mugil cephalus stomach: 58%) and whole (e.g. Mussel CRM 278R: 66.1 ± 0.5%; Bembicium auratum: 76.4%) tissues. Arsenic extraction efficiencies in the water-soluble fraction were slightly higher for Dogfish Liver (Dolt-1) and Oyster (SRM 1566a) compared to that reported in the literature for these tissues. These results indicate that when samples are prepared in a similar manner, the efficiency to extract arsenic in the methanol–water soluble fraction will depend on the marine animal species and tissue analysed. The robustness of the microwave-assisted extraction procedure to identify and quantify arsenic species in freeze-dried marine animal tissues was determined using high performance liquid chromatography-inductively coupled plasma-mass spectrometry and the certified reference materials Dogfish Muscle (Dorm-2) and Lobster Hepatopancreas (Tort-2). Arsenic species determined in Dorm-2 tissue were AsB (16.80 ± 0.14 µg g−1), TMAP (0.17 ± 0.01 µg g−1), AsC (0.023 ± 0.002 µg g−1), TETRA (0.24 ± 0.02 µg g−1) and DMA (0.280 ± 0.004 µg g−1). Arsenic species determined in Tort-2 tissue were AsB (13.10 ± 0.08 µg g−1), TMAP (1.20 ± 0.03 µg g−1), AsC (trace), TETRA (0.055 ± 0.005 µg g−1), DMA (1.03 ± 0.10 µg g−1), MA (0.20 ± 0.01 µg g−1), As+5 (0.41 ± 0.03 µg g−1) and phosphate arsenoribose (0.13 ± 0.03 µg g−1). Two unknown anionic and one cationic arsenic species were also identified in Tort-2 tissue.

Occurrence and chemical form of arsenic in marine macroalgae from the east coast of Australia

Arsenic concentrations were measured in thirteen macroalgal species from Sydney, Australia. Brown macroalgae contained, on average, more arsenic (range, mean ± s.e.: 5-173 µg g -1 , 39 ± 4 µg g -1 ) than either green (0.12-30.2 µg g -1 , 10.7 ± 0.7 µg g -1 ) or red macroalgae (0.11-16.9 µg g -1 , 4.3 ± 0.3 µg g -1 ). Despite the overlap in arsenic concentrations between different macroalgal species, inter-species arsenic variation was apparent with arsenic concentrations following the order brown > green > red macroalgal species. It was concluded that the main contribution to the variation in arsenic concentration was from natural variability expected to occur between individuals of any species as a result of physiological differences. Most of the arsenic compounds in macroalgae (70-108%) could be extracted using methanol/water mixtures, with 38-95% of the arsenic compounds present in characterizable forms. All macroalgal species contained arsenoribosides (9-99%). The distribution of arsenoribosides followed a general pattern; glycerol-arsenoriboside and phosphate-arsenoriboside were common to all macroalgal species. Sulfonate-arsenoriboside and sulfate-arsenoriboside were found in brown macroalgal species and one red macroalgal species. Six macroalgal species contained high concentrations of inorganic arsenic (14.2-62.9%) and four species contained high concentrations of dimethylarsinic acid (13.3-41.1%). The variation in the distribution of arsenic compounds in marine macroalgal species appears to be related to taxonomic differences in storage and structural polysaccharides.

Determination of total phosphorus and nitrogen in turbid waters by oxidation with alkaline potassium peroxodisulfate and low pressure microwave digestion, autoclave heating or the use of closed vessels in a hot water bath: comparison with Kjeldahl digestion

The evaluation of the use of alkaline peroxodisulfate digestion with low pressure microwave, autoclave or hot water bath heating for the determination of total phosphorus and nitrogen in turbid lake and river waters is described. The efficiency of these digestion procedures were compared to a Kjeldahl digestion procedure with sulphuric acid–potassium sulfate and copper sulfate. The final solution before digestion was 0.045 M in potassium peroxodisulfate and 0.04 M in sodium hydroxide. Procedures were evaluated by the analysis of suspensions of two reference materials, National Institute of Environmental Science, Japan, no. 3 Chlorella and no. 2 pond sediment and natural turbid waters. Best recoveries of phosphorus and nitrogen by microwave heating were obtained when solutions were digested at 95 ◦ C for 40 min. Quantitative recoveries of phosphorus from Chlorella suspensions up to 1000 mg/l were obtained by all three heating procedures, but incomplete recoveries of nitrogen occurred above 20 mg N/l in the digested sample. Good recoveries of phosphorus and nitrogen from suspended sediment suspensions were obtained only from solutions containing 150 mg/l) and are only suitable for the analysis of very turbid samples when the turbidity is due to organic matter (algal cells, plant detritus). Underestimation of nitrogen occurs when samples contain more than 20 mg N/l.