Mining causes extensive damage to aquatic ecosystems via acidification, heavy metal pollution, sediment loading, and Ca decline. Yet little is known about the effects of mining on freshwater systems ...in the Southern Hemisphere. A case in point is the region of western Tasmania, Australia, an area extensively mined in the 19th century, resulting in severe environmental contamination. In order to assess the impacts of mining on aquatic ecosystems in this region, we present a multiproxy investigation of the lacustrine sediments from Owen Tarn, Tasmania. This study includes a combination of radiometric dating (14C and 210Pb), sediment geochemistry (XRF and ICP-MS), pollen, charcoal and diatoms. Generalised additive mixed models were used to test if changes in the aquatic ecosystem can be explained by other covariates. Results from this record found four key impact phases: (1) Pre-mining, (2) Early mining, (3) Intense mining, and (4) Post-mining. Before mining, low heavy metal concentrations, slow sedimentation, low fire activity, and high biomass indicate pre-impact conditions. The aquatic environment at this time was oligotrophic and dystrophic with sufficient light availability, typical of western Tasmanian lakes during the Holocene. Prosperous mining resulted in increased burning, a decrease in landscape biomass and an increase in sedimentation resulting in decreased light availability of the aquatic environment. Extensive mining at Mount Lyell in the 1930s resulted in peak heavy metal pollutants (Pb, Cu and Co) and a further increase in inorganic inputs resulted in a disturbed low light lake environment (dominated by Hantzschia amphioxys and Pinnularia divergentissima). Following the closure of the Mount Lyell Co. in 1994 CE, Ca declined to below pre-mining levels resulting in a new diatom assemblage and deformed diatom valves. Therefore, the Owen Tarn record demonstrates severe sediment pollution and continued impacts of mining long after mining has stopped at Mt. Lyell Mining Co.
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•Mining has caused extensive environmental degradation in Tasmania.•A palaeoenvironmental study investigated the impacts of mining on an aquatic ecosystem.•The Owen Tarn record revealed four key impact phases.•Pre-mining, Early mining, Intense mining, and Post mining impacts.•Owen Tarn is impacted by severe sediment pollution and Ca decline from mining.
The Owen Tarn record revealed four impact phases: Pre-mining, Early mining, Intense mining, and Post mining. Mining caused severe sediment pollution and Ca decline in the aquatic environment.
High resolution X-ray fluorescence (XRF) is presented as a robust palaeoclimatic proxy, suitable for use on Late Pleistocene to Holocene sediments located in a volcanic crater on the Atherton ...Tableland in northeastern Queensland, Australia. The proxy allows identification of wet and dry shifts in a complex sedimentary sequence comprised of peat, gyttja, laminated organic rich muds and fine clastic silt-rich sediments. Significant correlation is found between the XRF record and other proxies including magnetic susceptibility, humification, grain size, macrocharcoal, δ13C and C/N and pollen.
Sixteen wetter periods are identified in the 37ka sedimentary record for Bromfield Swamp. Three wetter periods commence in late Marine Isotope Stage 3, nine in the early glacial, one in the late de-glacial and four in Holocene. Nineteen drier periods are identified, four in late MIS 3, seven in the early glacial, one during the LGM, one in the late de-glacial period and six in the Holocene.
The XRF record for Bromfield Swamp is specifically used to identify periods of abrupt climate change. Marked changes in effective precipitation are detected at 32,690, 30,080, 24,660, 21,870, 11,880, 10,020, 9170 and 5120cal.yrBP. The detection of these abrupt climate events may allow correlation with records from terrestrial sites across the Southern Hemisphere and potentially, the Northern Hemisphere.
•High resolution X-ray Fluorescence (XRF) is presented as a robust palaeoclimatic proxy•XRF identifies wet and dry shifts in a complex sedimentary sequence extracted from a volcanic crater in NE Australia•XRF record correlates well with magnetic susceptibility, humification, grainsize, macrocharcoal, δ13C, C/N and pollen•Abrupt climate events recorded at 32,690, 30,080, 24,660, 21,870, 11,880, 10,020, 9170 and 5120cal. yr BP
Surface elevation tables, feldspar marker horizons, and210Pb analysis of core profiles were implemented at four sites in Western Port Bay, Victoria, Australia, to provide information on the role of ...sedimentation, subsidence or compaction, and enhanced sea-level rise in contributing to salt marsh decline. Photogrammetric surveys indicate that the rate of salt marsh decline that is attributable to mangrove encroachment is lower in Western Port Bay than in comparable sites in New South Wales. Differences in the rate of mangrove encroachment at Western Port Bay may be attributed to the inverse relationship found between the degree of mangrove encroachment and surface elevation increase. While sedimentation contributes to surface elevation changes, surface elevation is not solely explained by sedimentation; factors including autocompaction and changes in the water table also play a significant role in Western Port Bay. Historic sedimentation rates measured using210Pb dating techniques corresponded to contemporary sedimentation rates determined from feldspar marker horizons. Core sediment profiles show no change in sedimentation rates at three sites. A fourth site (French Island) was the only site that exhibited high rates of sedimentation, which appears to be related to local land-use changes in the area. All sites maintained their elevation with respect to sea level over the study period. Historic sedimentation exceeded sea-level rise for the past 32 yr, but it is difficult to determine the extent to which belowground processes affect surface elevation, causing deviations between surface elevation and sedimentation over longer periods.
Laboratories from 14 countries (with different levels of expertise in radionuclide measurements and 210Pb dating) participated in an interlaboratory comparison exercise (ILC) related to the ...application of 210Pb sediment dating technique within the framework of the IAEA Coordinated Research Project.
The laboratories were provided with samples from a composite sediment core and were required to provide massic activities of several radionuclides and an age versus depth model from the obtained results, using the most suitable 210Pb dating model. Massic concentrations of Zn and Cu were also determined to be used for chronology validation.
The ILC results indicated good analytical performances while the dating results didn't demonstrate the same degree of competence in part due to the different experience in dating of the participant laboratories. The ILC exercise enabled evaluation of the difficulties faced by laboratories implementing 210Pb dating methods and identified some limitations in providing reliable chronologies.
•Interlaboratory comparison exercise (ILC) finds difficulties of the Pb-210 method.•ILC results indicate good analytical performance of the participants.•ILC dating results did not show the same degree of confidence.
Thiamine is an essential vitamin for most living organisms, of which yeasts are a rich nutritional source. In this study we developed a thiamine extraction and determination method to detect thiamine ...in fresh yeast biomass. The thiamine determination method combines the derivatization of thiamine to a highly fluorescent product, with chromatographic separation (HPLC) and fluorescence detection. The method specifically detects free thiamine (T), thiamine phosphate (TP), and thiamine pyrophosphate (TPP). It has a high sensitivity of 2 ng/ml for TPP and TP, and 1 ng/ml for T, excellent instrumental repeatability, and low day-to-day variation in retention time of the different phosphate forms. We demonstrated the robustness of the method by proving that the fluorescence signals of the derivatised samples are stable for at least 82 h after derivatization, and by showing that the final pH of the samples does not influence the fluorescent response. In addition, we developed and validated a thiamine extraction method consisting of beads beating the fresh yeast biomass in 0.1 M HCl using a lysing matrix composed of 0.1 mm silica spheres. The performance of this method was compared to extraction via heat treatment at 95 °C for 30 min, and a combination of beads beating and heat treatment carried out in different order. We demonstrated that thiamine extraction via beads beating is the only method that prevents the biologically active form thiamine pyrophosphate to be degraded to thiamine phosphate, therefore, the extraction method developed and described in this study is preferred when the different thiamine vitamers need to be detected in their actual proportions. The combination of the extraction via beads beating, the conversion of all vitamers to the thiochrome derivatives, and the separation of these compounds on the reversed phase HPLC with a fluorescence detector, yielded a sensitive, specific, repeatable, and robust method for extraction and determination of vitamin B
in fresh yeast biomass.
Coastal habitats including saltmarshes and mangrove forests can accumulate and store significant blue carbon stocks, which may persist for millennia. Despite this implied stability, the distribution ...and structure of intertidal‐supratidal wetlands are known to respond to changes imposed by geomorphic evolution, climatic, sea level, and anthropogenic influences. In this study, we reconstruct environmental histories and biogeochemical conditions in four wetlands of similar contemporary vegetation in SE Australia. The objective is to assess the importance of historic factors to contemporary organic carbon (C) stocks and accumulation rates. Results from the four cores—two collected from marine‐influenced saltmarshes (Wapengo marine site (WAP‐M) and Port Stephens marine site (POR‐M)) and two from fluvial influenced saltmarshes (Wapengo fluvial site (WAP‐F) and Port Stephens fluvial site (POR‐F))—highlight different environmental histories and preservation conditions. High C stocks are associated with the presence of a mangrove phase below the contemporary saltmarsh sediments in the POR‐M and POR‐F cores. 13C nuclear magnetic resonance analyses show this historic mangrove root C to be remarkably stable in its molecular composition despite its age, consistent with its position in deep sediments. WAP‐M and WAP‐F cores did not contain mangrove root C; however, significant preservation of char C (up to 46% of C in some depths) in WAP‐F reveals the importance of historic catchment processes to this site. Together, these results highlight the importance of integrating historic ecosystem and catchment factors into attempts to upscale C accounting to broader spatial scales.
Key Points
Multiple ecosystem shifts were observed within the surface 1 m of blue carbon sediments
Preservation of inputs from prior ecosystem formation can make large contributions to contemporary carbon stocks
Heterogeneity of historical influence needs to be accounted for in regional assessments of carbon storage
Soil and sediment samples from the Sydney basin were measured to ascertain fallout radionuclide activity concentrations and atom ratios. Caesium-137 ((137)Cs) was measured using gamma spectroscopy, ...and plutonium isotopes ((239)Pu and (240)Pu) were quantified using accelerator mass spectrometry (AMS). Fallout radionuclide activity concentrations were variable ranging from 0.6 to 26.1 Bq/kg for (137)Cs and 0.02-0.52 Bq/kg for (239+240)Pu. Radionuclides in creek sediment samples were an order of magnitude lower than in soils. (137)Cs and (239+240)Pu activity concentration in soils were well correlated (r(2) = 0.80) although some deviation was observed in samples collected at higher elevations. Soil ratios of (137)Cs/(239+240)Pu (decay corrected to 1/1/2014) ranged from 11.5 to 52.1 (average = 37.0 ± 12.4) and showed more variability than previous studies. (240)Pu/(239)Pu atom ratios ranged from 0.117 to 0.165 with an average of 0.146 (±0.013) and an error weighted mean of 0.138 (±0.001). These ratios are lower than a previously reported ratio for Sydney, and lower than the global average. However, these ratios are similar to those reported for other sites within Australia that are located away from former weapons testing sites and indicate that atom ratio measurements from other parts of the world are unlikely to be applicable to the Australian context.
Soil and sediment samples from the Sydney basin were measured to ascertain fallout radionuclide activity concentrations and atom ratios. Caesium-137 (137Cs) was measured using gamma spectroscopy, and ...plutonium isotopes (239Pu and 240Pu) were quantified using accelerator mass spectrometry (AMS).
Fallout radionuclide activity concentrations were variable ranging from 0.6 to 26.1 Bq/kg for 137Cs and 0.02–0.52 Bq/kg for 239+240Pu. Radionuclides in creek sediment samples were an order of magnitude lower than in soils. 137Cs and 239+240Pu activity concentration in soils were well correlated (r2 = 0.80) although some deviation was observed in samples collected at higher elevations. Soil ratios of 137Cs/239+240Pu (decay corrected to 1/1/2014) ranged from 11.5 to 52.1 (average = 37.0 ± 12.4) and showed more variability than previous studies.
240Pu/239Pu atom ratios ranged from 0.117 to 0.165 with an average of 0.146 (±0.013) and an error weighted mean of 0.138 (±0.001). These ratios are lower than a previously reported ratio for Sydney, and lower than the global average. However, these ratios are similar to those reported for other sites within Australia that are located away from former weapons testing sites and indicate that atom ratio measurements from other parts of the world are unlikely to be applicable to the Australian context.
•Comprehensive fallout radionuclide study in the Sydney basin, Australia.•Data presented here adds to the single 240Pu/239Pu atom ratio previously published for Sydney.•240Pu/239Pu atom ratios support other recent Australian measurements which are lower than published global fallout ratios.•137Cs/239+240Pu ratios show more variability compared to other studies.
A Compton suppressed high-purity germanium (HPGe) detector is well suited to the analysis of low levels of radioactivity in environmental samples. The difference in geometry, density and composition ...of environmental calibration standards (e.g. soil) can contribute to excessive experimental uncertainty to the measured efficiency curve. Furthermore multiple detectors, like those used in a Compton suppressed system, can add complexities to the calibration process. Monte Carlo simulations can be a powerful complement in calibrating these types of detector systems, provided enough physical information on the system is known. A full detector model using the Geant4 simulation toolkit is presented and the system is modelled in both the suppressed and unsuppressed mode of operation. The full energy peak efficiencies of radionuclides from a standard source sample is calculated and compared to experimental measurements. The experimental results agree relatively well with the simulated values (within ∼5 − 20%). The simulations show that coincidence losses in the Compton suppression system can cause radionuclide specific effects on the detector efficiency, especially in the Compton suppressed mode of the detector. Additionally since low energy photons are more sensitive to small inaccuracies in the computational detector model than high energy photons, large discrepancies may occur at energies lower than ∼100 keV.
► We model a Compton Suppressed HPGe detector using Geant4. ► Experimental full energy peak (FEP) efficiencies are measured. ► Experimental and simulated FEP efficiencies are compared. ► Radionuclide specific effects on the detector efficiency can occur.
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