Dulasiri Amarasiriwardena

Antimony, arsenic and mercury in the aquatic environment and fish in a large antimony mining area in Hunan, China

Antimony (Sb) has received increasing attention recently due to its toxicity and potential human carcinogenicity. In the present work, drinking water, fish and algae samples were collected from the Xikuangshan (XKS) Sb mine area in Hunan, China. Results show that serious Sb and moderate arsenic (As) contamination is present in the aquatic environment. The average Sb concentrations in water and fish were 53.6 + or - 46.7 microg L(-1) and 218 + or - 113 microg kg(-1) dry weight, respectively. The Sb concentration in drinking water exceeded both Chinese and WHO drinking water guidelines by 13 and 3 times, respectively. Antimony and As concentrations in water varied with seasons. Fish gills exhibited the highest Sb concentrations but the extent of accumulation varied with habitat. Antimony enrichment in fish was significantly lower than that of As and Hg.

Investigation of gold nanoparticles uptake and their tissue level distribution in rice plants by laser ablation-inductively coupled-mass spectrometry

The tissue level uptake and spatial distribution of gold nanoparticles (AuNPs) in rice (Oryza sativa L.) roots and shoots under hydroponic conditions was investigated using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Rice plants were hydroponically exposed to positively, neutrally, and negatively charged AuNPs [AuNP1(+), AuNP2(0), AuNP3(-)] with a core diameter of 2 nm. Plants were exposed to AuNPs having 1.6 mg Au/L for 5 days or 0.14 mg Au/L for 3 months to elucidate how the surface charges of the nanoparticles affects their uptake into living plant tissues. The results demonstrate that terminal functional groups greatly affected the AuNP uptake into plant tissues. Au concentration determined by LA-ICP-MS in 5 day treated rice roots followed this order: AuNP1(+) > AuNP2(0) > AuNP3(-) but this order was reversed for rice shoots, indicating preferential translocation of AuNP3(-). Bioimages revealed distributions of mesophyll and vascular AuNP dependent on organ or AuNP concentration.

Dual purpose secondary compounds: phytotoxin of Centaurea diffusa also facilitates nutrient uptake

Traits that allow more efficient foraging for a deficient resource could increase the competitiveness of a species in resource-poor habitats. Considering the metal-nutrient mobilization ability of many allelochemicals, it is hypothesized that, along with the reported toxic effect on the neighbors, these compounds could be directly involved in resource acquisition by the allelopathic plant. Using nutrient manipulation treatments in hydroponic culture, this hypothesis was tested using Centaurea diffusa, an invasive species that produces the putative phytotoxin 8-hydroxyquinoline (8HQ). The exudation of 8HQ by C. diffusa was very limited and transient. It was further shown that: C. diffusa utilizes 8HQ for its own acquisition of iron, a nutrient deficient in many of its alkaline, invaded habitats; there possibly exists a unique mechanism for the uptake of the 8HQ-complexed iron (Fe) in C. diffusa, which is novel to the nongraminaceous species; although phytotoxic at very low concentrations, the toxic effect of 8HQ showed a conditional response in the presence of metals, and was significantly reduced when 8HQ was complexed with copper (Cu) and Fe. This study, in addition to elucidating one of the possible adaptive mechanisms conferring competitive advantage to C. diffusa, also outlines measures to negate the phytotoxicity of its putative allelochemical. The results indicate that the exudation of 8HQ by C. diffusa could be primarily for nutrient acquisition.

Arsenic determination in environmental, biological and food samples by inductively coupled plasma mass spectrometry

Methodology developed with inductively coupled plasma mass spectrometry (ICP-MS) for the determination of total arsenic in soil, house dust, and childrens daily diet and faecal samples is described. Microwave oven dissolution, high temperature, pressure vapour phase acid digestion, and dry ashing with conventional thermal and microwave furnace heating and Mg(NO3)2 ashing aid are compared for sample preparation. Arsenic recovery from reference materials and spiked samples is between 94.8 and 109%. The ICP-MS Elan 5000a As detection limits (3sb) were 2.0 ng g–1 in freeze-dried human faeces prepared by closed-vessel, microwave-heated digestion and 1.1 ng g–1 in freeze-dried childrens diets prepared by furnace ashing with an ashing aid.

Vapour-phase acid digestion of micro samples of biological material in a high-temperature, high-pressure asher for inductively coupled plasma atomic emission spectrometry

This vapour-phase acid decomposition of small biological samples (50-165 mg) and concurrent purification of the reagent acid were achieved in a mini-quartz sample holder inserted in a commercial high-pressure digestion vessel. A 3.1 ml volume sample contained was developed to hold the sample and to maximize the successful decomposition of a variety of biological samples. When biological standard reference materials were digested at 230 degrees C and 122 bar (1770 psi), the residual carbon content in the digested samples was less than 1.8 +/- 0.1%. Inductively coupled plasma atomic emission spectrometric analysis of the digested materials for C, Ca, Cu, Cd, Fe, Mg, Mn and Zn provided good recoveries and low reagent blank values and demonstrated complete matrix decomposition.

Imaging of metal bioaccumulation in hay-scented fern (Dennstaedtia punctilobula) rhizomes growing on contaminated soils by laser ablation ICP-MS.

Understanding Pb removal from the translocation stream is vital to engineering Pb hyperaccumulation in above ground organs, which would enhance the economic feasibility of Pb phytoextraction technologies. We investigated Cu, Pb, Sb and Zn distributions in Hay-scented fern (Dennstaedtia punctilobula) rhizomes on shooting range soils by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), analyzing digested rhizomes, stems, and fronds using ICP-MS. Nutrients Cu and Zn concentrated in fronds while toxic elements Pb and Sb did not, showing potential Pb and Sb sequestration in the rhizome. Frond and rhizome concentration of Pb was 0.17 ± 0.10% and 0.32 ± 0.21% of dry biomass, respectively. The 208Pb/13C and 121Sb/13C determined by LA-ICP-MS increased from inner sclerotic cortex to the epidermis, while Pb concentrated in the starchy cortex only in contaminated sites. These results suggest that concentration dependent bioaccumulation in the rhizome outer cortex removes Pb from the vascular transport stream.

Characterization of lead and lead leaching properties of lead glazed ceramics from the Solis Valley, Mexico, using inductively coupled plasma-mass spectrometry (ICP-MS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT)

Abstract Ingestion of relatively small amounts of lead is now recognized to cause significant neurological and cognitive effects in humans. Large quantities may be fatal, yet lead poisoning, especially of children, is still a major public health concern in many parts of the world. In rural Mexican communities lead oxide (PbO) is added to ceramic glaze as a fluxing agent, lowering starting firing temperatures to 500 °C. The purpose of this study is to characterize the lead chemical forms in ceramic glazes from the Solis Valley, Mexico, to investigate lead leaching properties of these ceramics, and to demonstrate the applicability of lead isotope signatures as a means of tracing lead source origins. Ceramics were collected from the rural village of Santa Maria de Canchesda, State of Mexico, Mexico. Dried liquid glazes, post-fired glaze material, and pure PbO were analyzed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFT). Results from DRIFT analysis indicate that PbO (1429 cm−1 band) is the active form of lead found in liquid glazes and ceramics. Some shifting of 1429 cm−1 PbO peak to lower wavenumbers occurs in post-fired ceramics, and this may be due to the formation of lead bisilicate during firing. Ceramics samples were leached in 0.02 M citric acid solution for 1 min, and leached lead concentrations were measured using inductively coupled plasma-mass spectrometry (ICP-MS). Lead concentrations in these leachates varied from 0.4–80.4 μg ml−1, while the control pottery from the US leached only 0.1 μg ml−1 lead. Elemental distributions on glaze surfaces were identified by laser ablation (LA)-ICP-MS. Nitric acid extracts of soils, teeth, and ceramic glazes were analyzed for lead isotope ratios (207Pb/206Pb vs. 208Pb/206Pb) using ICP-MS. Similarities of tooth and ceramic lead isotope ratios indicate that ceramics may be a substantial source of body lead burden in the Solis Valley. This study demonstrates the applicability of lead isotope ratios for lead source identification, and it identifies potential health risks from ceramic use induced lead toxicity within the Solis Valley.

Biomonitoring of lead in Antarctic lichens using laser ablation inductively coupled plasma mass spectrometry

A method for direct determination of Pb by LA-ICP-MS in lichen samples collected in a heavily anthropogenically impacted area of Maritime Antarctica was developed. The lichen samples were cryogenically ground and digested with nitric acid and hydrogen peroxide. Lead determination by solution-based ICP-MS was validated by the use of 2 certified reference materials. Once the Pb concentrations were measured with adequate accuracy and precision, a method for its direct determination by LA-ICP-MS was developed. The laser ablation parameters were optimized by the use of a Doehlert design matrix. The final optimized conditions were: laser energy (60%), spot size (150 μm) and repetition rate (10 Hz). Lead concentration of the analyzed lichen samples were plotted against the intensity of the lead isotopes (208Pb, 207Pb and 206Pb) determined by LA-ICP-MS. Satisfactory linear correlation factors were obtained when 13C was used as internal standard. Lead distribution profiles in lichen thalli cross-sections were also obtained. By these results, LA-ICP-MS emerges as a potential analytical tool for Pb concentration estimation in lichen samples. Minimum amount of sample required, bioimaging capability, high analytical throughput, and minimization of waste generation are the major analytical features of this approach. The significant differences between the Pb concentration in the lichen samples from the control site (1.12 ± 0.05 mg kg−1) and from the impacted points (mean = 5.03 ± 0.57 mg kg−1) permitted qualify these organisms as good biomonitors. Elemental bioimaging of lichens demonstrated that the medulla region of lichen thalli is consistently the main atmospheric lead bioaccumulating lichen tissue.

Closed-vessel microwave acid digestion of commercial maple syrup for the determination of lead and seven other trace elements by inductively coupled plasma-mass spectrometry

Abstract A method was developed and applied for the determination of lead and other trace elements (As, Cd, Co, Cu, Mn, V and Zn) in 8 commercial maple syrups. Samples were digested using closed-vessel microwave heating. Two different types of microwave vessels, low-pressure and moderately high-pressure vessels, were evaluated. Average temperatures and maximum pressures attained during the maple syrup sample digestion were 140°C and 190 psi (1310 kPa) for low-pressure vessels and 200°C and 500 psi (3450 kPa) for moderately high-pressure vessels. All digested samples were clear and colorless and their residual carbon content was less than 1%, indicating successful decomposition of the organic matrix. The residual acid concentrations in the final analytical solutions were 2.2±0.3% and 2.5±0.2% (w/w) for low and moderately high-pressure vessels, respectively; this is suitable for inductively coupled plasma-mass spectrometery (ICP-MS) analysis. The digested syrup samples were analyzed using ICP-MS. Spike recovery for lead, after digestion in the low-pressure and moderately high-pressure digestion vessels, were 100±2% ( n =5, 95% CI) and 98±1% ( n =5, 95% CI), respectively. Satisfactory recoveries were also obtained for seven selected elements. Lead-spiked maple syrup check standards were digested, and lead concentrations were in the range of certified values. Lead levels ranged from 18 to 367 ng/g. Concentrations of seven other trace elements (As, Cd, Co, Cu, Mn, V and Zn) in maple syrup were also determined.

Tooth Rings: Dental Enamel as a Chronological Biomonitor of Elemental Absorption from Pregnancy to Adolescence

Because the dental hard tissues commence development in the 13th week in utero and once formed are essentially inert, they may provide unique windows onto environmental and physiological changes du...