Preparation of matrix-matched standards for the analysis of teeth via laser ablation-inductively coupled plasma-mass spectrometry.

Mineralised tissue such as teeth can serve as a retrospective, chronological bioindicator of past exposure to toxic metals. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) can be used to determine the presence and spatial distribution of toxic metals in teeth, giving a record of when an exposure occurred. Concentrations of these metals are often determined by a one-point calibration against NIST glass using an equation that requires an internal standard factor that accounts for differences in ablation behaviour between the glass and the tooth. However, an ideal external calibration would contain multiple matrix-matched standards to obtain a calibration curve. Here, we investigated optimal procedures for preparing synthetic hydroxyapatite (HA) doped with elements of interest as a calibration material. The materials were examined for homogeneity of metal incorporation, matrix-matched ablation characteristics, linearity, and limits of detection. A homogenised and pelleted HA was the most suitable material, providing improved ablation characteristics over previous HA materials and NIST glass for the analysis of teeth. An ablation yield of 1.1 showed its suitability to analyse teeth, the metals were homogeneously incorporated, and it produced excellent linearity with limits of detection ranging from 0.1-2 μg kg-1 for magnesium, aluminium, nickel, copper, zinc, cadmium, barium and lead. A juvenile incisor from a remote indigenous community in Australia and an adult molar from Sri Lanka were assessed for toxic metal exposure. The molar showed evidence of exposure to cadmium and lead. The synthetic HA material was straightforward to prepare, and will improve confidence in the analysis of teeth and other biomineralised material when assessing toxic metal exposure

Reconstruction of the Late Holocene climate and environmental history from North Bolgoda Lake, Sri Lanka, using lipid biomarkers and pollen records

The catastrophic impact and unpredictability of the Indian Ocean Monsoon (IOM) over South Asia are evident from devastating floods, mudslides and droughts in one of the most densely populated regions of the globe. However, our understanding as to how the IOM has varied in the past, as well as its impact on local environments, remains limited. This is particularly the case for Sri Lanka, where erosional landscapes have limited the availability of well-stratified, high-resolution terrestrial archives. Here, we present novel data from an undisturbed sediment core retrieved from the coastal Bolgoda Lake. This includes the presentation of a revised Late Holocene age model as well as an innovative combination of pollen, source-specific biomarkers, and compound-specific stable carbon isotopes of n-alkanes to reconstruct the shifts in precipitation, salinity and vegetation cover. Our record documents variable climate between 3000 years and the present, with arid conditions c. 2334 and 2067 cal a bp. This extreme dry period was preceded and followed by more wet conditions. The high-resolution palaeoenvironmental reconstruction fills a major gap in our knowledge on the ramifications of IOM shifts across South Asia and provides insights during a time of major redistribution of dense human settlements across Sri Lanka.Introduction Background, materials and methods - Study area and site - Sampling - Age–depth model - Biomarker analysis - Compound‐specific carbon isotope analysis - Pollen analysis Results - Chronology and climate zones - Biomarker trends and ratios of n‐alkanes - Triterpenols - δ13C isotopes in n‐alkanes - Pollen Discussion - Palaeoenvironmental implications - Mangrove vegetation, palaeosalinity changes and droughts - Palaeoclimate and palaeoenvironmental reconstruction - Zone 1 (2960 to 2390 cal a bp; 385–252 cm) - Zone 2 (2390 to 1800 cal a bp; 252–140 cm) - Zone 3 (1800 to 1318 cal a bp; 140–60 cm) - Zone 4 (1318 cal a bp to present; 60–0 cm) - South Asian comparisons and potential human implications Conclusion

Comparative Assessment of Trace Element Accumulation in Traditional and Improved Rice (Oryza sativa L.) Varieties Grown with Organic, Chemical and Non-Fertilizers

Oryza sativa L., is the most widely grown rice in Sri Lanka. At present, farmers are using both organic and chemical fertilisers for the paddy cultivation. There is growing concern about heavy metal (mainly As, Cd and Pb) build up in the soils because they enter the soil and the plants via application of fertilisers (anthropogenic). Heavy metals are also found in the soil (geogenic). Cd and As are both nephrotoxic and neurotoxic, and there is a concern that they may be involved in the chronic kidney disease of uncertain etiology (CKDu) prevalent in the North Central Province and neighboring areas. According to the Food and Agriculture Organization (FAO), the maximum allowable limit (MAL) of Cd and As is 0.2 μg g-1. This study was conducted to compare the heavy metal accumulation in traditional and improved rice varieties grown with organic fertilisers, chemical fertilisers and without fertilisers. Total of 126 paddy samples (including seven traditional and seven improved rice varieties) grown with organic, chemical and non-fertiliser, were collected directly from the paddy fields in Rice Research and Development Institute (RRDI) at Batalagoda. Soil samples from paddy plots with different fertiliser treatments were collected. Heavy metal analysis was done at the Geology Department of the University of Peradeniya by using ThermoICapQ Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Rice cultivated with chemical fertilisers had the highest mean heavy metal concentrations. Cd concentration (0.32 μg Cd g-1) in traditional varieties grown with chemical fertilisers was significantly higher than in the other treatments. That value is 1.6 fold higher than the MAL. Organic fertiliser treated improved varieties had the lowest level of Cd and it was less than the MAL. All the other treatments had Cd levels more than the MAL. All treatments had lower content of As than the MAL. Taken as a whole, macro-nutrients (K, Ca, Mg) were higher in the chemical fertiliser treated rice than that of organic treated rice. Heavy metals and macro-nutrient concentrations varied from variety to variety.Keywords: Chemical fertiliser, Heavy metals, Improved rice, Organic fertilizer, Traditional ric

Groundwater quality and antibiotic resistance of coliform bacteria in Wilgamuwa, an area of Chronic Kidney Disease of unknown etiology (CKDu) in Sri Lanka

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Reply to commentary by R Duggleby (2019)

Duggleby (2018) has made a numerical analysis of some aspects of the wide range of phenomena we reviewed in Steele et al. (2018) and asserted " .that panspermia as proposed by Steele et al. (2018) is extremely implausible.” It seems to us that Duggleby has based his viewpoint on a quite narrow and specific model of Panspermia which he supposes to be active in the cosmos. Here we address both his conclusions and his numerical analysis. Our response therefore will be at two levels, his specific analysis and his general conclusions. In the specific section below we show that while Duggleby's numerical analysis appears in part correct it is, in the final analysis, quite irrelevant to Cosmic Panspermia. In the general response which follows we address his unsupported conclusion throughout his critique, namely that … " none of the examples mentioned by Steele et al. (2018) is decisive enough to allow no other explanation.

Reply to editorial and commentaries on Steele, Al-Mufti, Augustyn, Chandrajith, Coghlan, Coulson et al. (2018) "Cause of Cambrian explosion - Terrestrial or cosmic?"

No abstract availabl

Comparison of total ionic strength adjustment buffers III and IV in the measurement of fluoride concentration of teas

Background: Tea is the second most consumed drink in the UK and a primary source of hydration; it is an important source of dietary fluoride (F) for consumers and also abundant in aluminium (Al). Varying ranges of F concentrations in teas have been reported worldwide which may be, in part, due to differences in analytical techniques used to measure this ion.Aim: The effect of using total ionic adjustment buffers (TISAB) III or IV when measuring F concentration of black teas available in the UK was investigated and compared. Based on this evaluation, the effects of three different infusion times, 1 min, 10 min and 1 h, caffeine content and tea form on the F contents of the tea samples were investigated.Methods: The F concentrations of 47 tea samples were measured directly using a fluoride ion-selective electrode (F-ISE), TISAB III and IV and infusion times of 1 min, 10 min and 1 h.Results:Mean (SD) F concentration of tea samples for all infusion times was statistically significantly higher (p &lt; 0.001) measured by TISAB IV (4.37 (2.16) mg/l) compared with TISAB III (3.54 (1.65) mg/l). A statistically significant positive correlation (p &lt; 0.001) was found between Al concentration (mg/l) and differences in F concentration (mg/l) measured using the two TISABs; the difference in F concentration measured by the two TISABs increased with the magnitude of Al concentration.Conclusion :Due to higher concentrations of F and Al in teas and their complexing potential, use of TISAB IV facilitates more accurate measurement of F concentration when using an F-ISE and a direct method.</p