Natural Environmental Samples Research Articles

Four novel Acinetobacter lwoffii strains isolated from the milk of cows in China with subclinical mastitis

BackgroundAcinetobacter lwoffii (A. lwoffii) is a Gram-negative bacteria common in the environment, and it is the normal flora in human respiratory and digestive tracts. The bacteria is a zoonotic and opportunistic pathogen that causes various infections, including nosocomial infections. The aim of this study was to identify A. lwoffii strains isolated from bovine milk with subclinical mastitis in China and get a better understanding of its antimicrobial susceptibility and resistance profile. This is the first study to analyze the drug resistance spectrum and corresponding mechanisms of A. lwoffii isolated in raw milk.ResultsFour A. lwoffii strains were isolated by PCR method. Genetic evolution analysis using the neighbor-joining method showed that the four strains had a high homology with Acinetobacter lwoffii. The strains were resistant to several antibiotics and carried 17 drug-resistance genes across them. Specifically, among 23 antibiotics, the strains were completely susceptible to 6 antibiotics, including doxycycline, erythromycin, polymyxin, clindamycin, imipenem, and meropenem. In addition, the strains showed variable resistance patterns. A total of 17 resistance genes, including plasmid-mediated resistance genes, were detected across the four strains. These genes mediated resistance to 5 classes of antimicrobials, including beta-lactam, aminoglycosides, fluoroquinolones, tetracycline, sulfonamides, and chloramphenicol.ConclusionThese findings indicated that multi-drug resistant Acinetobacter lwoffii strains exist in raw milk of bovine with subclinical mastitis. Acinetobacter lwoffii are widespread in natural environmental samples, including water, soil, bathtub, soap box, skin, pharynx, conjunctiva, saliva, gastrointestinal tract, and vaginal secretions. The strains carry resistance genes in mobile genetic elements to enhance the spread of these genes. Therefore, more attention should be paid to epidemiological surveillance and drug resistant A. lwoffii.

Detection and Removal of Aristolochic Acid in Natural Plants, Pharmaceuticals, and Environmental and Biological Samples: A Review.

Aristolochic acids (AAs) are a toxic substance present in certain natural plants. Direct human exposure to these plants containing AAs leads to a severe and irreversible condition known as aristolochic acid nephropathy (AAN). Additionally, AAs accumulation in the food chain through environmental mediators can trigger Balkan endemic nephropathy (BEN), an environmental variant of AAN. This paper presents a concise overview of the oncogenic pathways associated with AAs and explores the various routes of environmental exposure to AAs. The detection and removal of AAs in natural plants, drugs, and environmental and biological samples were classified and summarized, and the advantages and disadvantages of the various methods were analyzed. It is hoped that this review can provide effective insights into the detection and removal of AAs in the future.

Tetraphenylethene-Based Cross-Linked Conjugated Polymer Nanoparticles for Efficient Detection of 2,4,6-Trinitrophenol in Aqueous Phase.

The cross-linked conjugated polymer poly(tetraphenylethene-co-biphenyl) (PTPEBP) nanoparticles were prepared by Suzuki-miniemulsion polymerization. The structure, morphology, and pore characteristics of PTPEBP nanoparticles were characterized by FTIR, NMR, SEM, and nitrogen adsorption and desorption measurements. PTPEBP presents a spherical nanoparticle morphology with a particle size of 56 nm; the specific surface area is 69.1 m2/g, and the distribution of the pore size is centered at about 2.5 nm. Due to the introduction of the tetraphenylethene unit, the fluorescence quantum yield of the PTPEBP nanoparticles reaches 8.14% in aqueous dispersion. Combining the porosity and nanoparticle morphology, the fluorescence sensing detection toward nitroaromatic explosives in the pure aqueous phase has been realized. The Stern-Volmer quenching constant for 2,4,6-trinitrophenol (TNP) detection is 2.50 × 104 M-1, the limit of detection is 1.07 μM, and the limit of quantification is 3.57 μM. Importantly, the detection effect of PTPEBP nanoparticles toward TNP did not change significantly after adding other nitroaromatic compounds, indicating that the anti-interference and selectivity for TNP detection in aqueous media is remarkable. In addition, the spike recovery test demonstrates the potential of PTPEBP nanoparticles for detecting TNP in natural environmental water samples.

Simultaneous Analysis of Cyanotoxins β-N-methylamino-L-alanine (BMAA) and Microcystins-RR, -LR, and -YR Using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS).

β-N-methylamino-L-alanine (BMAA) and its isomers, 2,4-diaminobutyric acid (2,4-DAB) and N-(2-aminoethyl)-glycine (AEG), along with microcystins (MCs)-RR, -LR, and -YR (the major MC congeners), are cyanotoxins that can cause detrimental health and environmental impacts during toxic blooms. Currently, there are no reverse-phase (RP) LC-MS/MS methods for the simultaneous detection and quantification of BMAA, its isomers, and the major MCs in a single analysis; therefore, multiple analyses are required to assess the toxic load of a sample. Here, we present a newly developed and validated method for the detection and quantification of BMAA, 2,4-DAB, AEG, MC-LR, MC-RR, and MC-YR using RP LC-MS/MS. Method validation was performed, assessing linearity (r2 > 0.996), accuracy (>90% recovery for spiked samples), precision (7% relative standard deviation), and limits of detection (LODs) and quantification (LOQs) (ranging from 0.13 to 1.38 ng mL-1). The application of this combined cyanotoxin analysis on a culture of Microcystis aeruginosa resulted in the simultaneous detection of 2,4-DAB (0.249 ng mg-1 dry weight (DW)) and MC-YR (4828 ng mg-1 DW). This study provides a unified method for the quantitative analysis of BMAA, its isomers, and three MC congeners in natural environmental samples.

Impact of metabolism and temperature on 2H ∕ 1H fractionation in lipids of the marine bacterium Shewanella piezotolerans WP3

Abstract. Compound-specific hydrogen isotopes have increasingly been used as a powerful proxy for investigating biogeochemical cycles and climate change over the past 2 decades. Understanding the hydrogen isotope in extant organisms is fundamental for us to interpret such isotope signals preserved in natural environmental samples. Here, we studied the controls on hydrogen isotope fractionation between fatty acids and growth water by an Fe-reducing heterotrophic marine bacterium Shewanella piezotolerans WP3 growing on different organic substrates, including N-acetyl-D-glucosamine (GlcNac), glucose, acetate, pyruvate, L-alanine, and L-glutamate. Meanwhile, we also evaluated the impact of growth temperature on the hydrogen isotope composition of fatty acids using GlcNac as the sole organic substrate. Our results show that the abundance-weighted mean fatty-acid / water fractionations (εFA/water) display considerable variations for cultures grown on different substrates. Specifically, WP3 yielded the most 2H-enriched fatty acids growing on L-glutamate and pyruvate with an εFA/water of 52 ± 14 ‰ and 44 ± 4 ‰, respectively, and exhibited 2H depletion using GlcNac (−76 ± 1 ‰) and glucose (−67 ± 35 ‰) as sole carbon sources and relatively small fractionations on acetate (23 ± 3 ‰) and L-alanine (−4 ± 9 ‰). Combined with metabolic model analysis, our results indicate that the central metabolic pathways exert a fundamental effect on the hydrogen isotope composition of fatty acids in heterotrophs. Temperature also has an obvious influence on the δ2H values of fatty acids, with strong 2H depletion at an optimal growth temperature (−23 ± 2 ‰ and −23 ‰ growing at 15 and 20 ∘C, respectively) and relatively small fractionations at non-optimal temperatures (4 ± 5 ‰, −4 ± 12 ‰, and 15 ± 41 ‰ at 4, 10, and 25 ∘C, respectively). We hypothesized that this may be associated with temperature-induced enzyme activity for nicotinamide adenine dinucleotide phosphate (NADPH) production. This study helps understand the controlling factors of hydrogen isotope fractionation by marine bacteria, laying the foundation for further interpreting the hydrogen isotope signatures of lipids as an important proxy to decode the biogeochemical cycles and ecological changes in marine sediments.

One-step effervescence tablet-assisted switchable hydrophilic solvent microextraction combined with micro spectrophotometry for the determination of copper in Salvia yunnanensis and environmental samples

In this work, an efficient one-step effervescence tablet-assisted switchable hydrophilic solvent microextraction (ETA-SHS-ME) method was developed and firstly combined with micro ultraviolet-visible (micro UV-Vis) spectrophotometry for the determination of trace copper (Cu) in natural medicine Salvia yunnanensis and environmental samples (water and soil). The extraction was rapidly accomplished in one step by transferring the effervescence tablet into the aqueous sample, the proton donor agent (malonic acid) contained in the tablet reacted simultaneously with the organic phase source (sodium nonanoate) and the effervescent agent (sodium bicarbonate, NaHCO3) to produce the extractant nonanoic acid and CO2. The in situ generated CO2 promoted the dispersion of nonanoic acid in the aqueous sample and improved the extraction efficiency of the analytical method. Under the optimal conditions, the limit of detection (LOD) and the limit of quantification (LOQ) were 0.01 and 0.04 μg/L, respectively, and the enhancement factor (EF) was 76.3. The developed method was successfully applied to the analysis of trace Cu in natural medicine and environmental samples. The one-step extraction method coupled with portable spectrophotometer has a good prospect for application in field analysis.

Temperature-controlled electrochemical sensor based on environmentally responsive polymer/BiPO4/BiOCl/multi-walled carbon nanotube composite for the detection of catechol in water

Catechol is a phenolic environmental pollutant that is highly toxic to living organisms and is released into the environment, where it is difficult to degrade in the ecosystem, thereby contaminating the environment and groundwater. Here, P(NIPAM-co-BMA)/BiPO4/BiOCl/MWCNTs nanocomposites were synthesized, and a temperature-controlled "on/off" electrochemical sensor was constructed. In addition, the P(NIPAM-co-BMA)/BiPO4/BiOCl/MWCNTs/GCE sensor shows good thermal sensitivity and electrochemical detection of catechol. Reproducible "on/off" switching on the CVs curve can be achieved by controlling the temperature of the solution. Under optimal conditions, the sensor was able to detect catechol in the linear range of 0.5–86.51 μM with a limit of detection of 0.2 μM (S/N = 3). Satisfactory results were obtained for the detection of natural environmental samples (tap water). In addition, the redox mechanism and electrochemical reaction sites of catechol were investigated by scanning rates. This work demonstrates for the first time the combination of temperature-sensitive polymers, bismuth-based compounds and multi-walled carbon nanotubes as electrochemical sensors for the detection of catechol, opening a new window for the sensitive detection of catechol. At the same time, the constructed switch-like electrochemical sensors can be better applied to different special scenarios.

Assessing the performance of four indicative analysis devices for ballast water compliance monitoring, considering organisms in the size range ≥10 to

To minimize the global transfer of harmful aquatic organisms and pathogens, the International Maritime Organization (IMO) has introduced the standard in Regulation D-2 to limit the number of viable organisms in ballast water discharged by ships. To meet the standard, many ships are installing ballast water management systems. Concurrently, regulators are looking for indicative analysis devices able to assess compliance with Regulation D-2, producing rapid, accurate and reliable results while being easy to operate. The purpose of this research is to compare four indicative analysis devices against detailed microscopy for measuring the size class of organisms ≥10 to <50 μm in minimum dimension (e.g., phytoplankton, including autotrophs, heterotrophs or mixotrophs), using field and laboratory tests. Comparisons were conducted on (treated) ballast water discharge samples collected across Canada during three consecutive years (2017–2019). During seven tests in 2019, paired ballast water uptake samples were also obtained, facilitating measurements before and after treatment was applied. Indicative analysis devices also were challenged with natural environmental samples containing different organism abundance levels, ranging from low (nominally <10 cells mL−1) to high (nominally >150 cells mL−1) during laboratory tests. While the indicative analysis devices examined during this research produced numeric estimates having weak correlations with the standard reference method, categorical outcomes (above/below the D-2 standard) had high agreement (89% or better) when assessing ballast water samples, but lower agreement (67% or poorer) during laboratory tests. There was a relatively high rate of false negative results measured by all devices during laboratory tests. Results provided by indicative analysis devices had higher uncertainty when organism abundances in ballast samples are below and close to the D-2 standards.

A part per trillion isotope ratio analysis of 90Sr/88Sr using energy-filtered thermal ionization mass spectrometry

Strontium-90 is a major radioactive nuclide released by nuclear accidents and discharge waste. Input of such radioactive nuclide into earth surface environment causes potential threat of long-term internal exposure when taken up by organism. Rapid and precise measurement of 90Sr in variety of environmental sample is important to understand the distribution and dynamics of 90Sr in the local environment after the accident and to assess the effect of radioactive nuclide inputs on bodies. However, previous 90Sr measurement techniques have drawbacks such as long measurement times for radiometry and high detection limits for mass spectrometry. Here we present a technique to accurately measure a significantly small amount of 90Sr in natural environmental samples using an energy-filtered thermal ionization mass spectrometry. Our technique achieved a 90Sr detection limit of 0.23 ag, which corresponds to a 90Sr activity of 1.2 µBq. The detection limit was lowered by two orders of magnitude compared with the previous mass spectrometric 90Sr analyses. The ability of our technique will expand the applicability of mass spectrometric 90Sr survey not only to the rapid 90Sr survey upon nuclear accidents but also to study a long-term environmental diffusion of radioactive materials using size-limited environmental and biological samples.

An anion exchange pretreatment method for the determination of low-level uranium in the environmental water samples

Uranium in environmental water is usually at trace or ultra-trace levels with high concentrations of background ions so that the detection of uranium often couples with pretreatment processes to lower the detection limit, and improve the selectivity and accuracy of instruments. A simple, green, effective and efficient anion exchange pretreatment method was proposed to favor the determination of low-level uranium in natural environmental water samples. To determine the applicability and obtain the optimum operating parameters, the effects of coprecipitation, pH, contact time, uranium concentration, background ions, eluent and the flow speed on the uranium recovery were investigated. The experimental results showed that the proper addition of saturated Na2CO3 solution for pH adjustment did not lead to uranium loss in natural water samples, and the optimum pH value for adsorption was determined from 6 to 8. The adsorption speed was improved a lot with the employment of a novel silica-supported anion exchange resin, which also showed good linear dependence in the concentration range from <0.5 μg/L to 1000 μg/L with high tolerance limits towards common background ions. The optimum eluent was determined as 1 M HNO3, and the optimum flow speeds for adsorption and desorption were about 4.0 and 1.0 mL/min, respectively. Based on these results, a pretreatment process was finally established, which realized the quantitative recovery of uranium from six different natural water samples with the chemical yields exceeding 95% and the enrichment factors about 100 times.

Conversion of the LLNL/CAMS 1 MV biomedical AMS system to a semi-automated natural abundance 14C spectrometer: system optimization and performance evaluation

The Lawrence Livermore National Laboratory – Center for Accelerator Mass Spectrometry compact 1 MV biomedical accelerator mass spectrometer was repurposed and optimized for the semi-automated radiocarbon measurement of natural abundance environmental samples. Here we present results from 15 months of routine system operation and evaluate the system performance based on 30 sample wheels measured with consistent operating conditions over 7 months from August 2019 to March 2020. The average measurement precision was 2.7 ± 0.7‰. System accuracy was assessed with measurements of 14C-free materials, standard materials with 14C-content spanning 0.5 to 1.5 F14C, and by comparison to split samples measured with the 10 MV AMS system. Overall, this system can routinely measure samples as small as 300 µgC and less than 33000 years without the need for size-specific correction protocols.

Separation of microplastics from mass-limited samples by an effective adsorption technique

Microplastic in the environment hides visible and invisible dangers for the ecosystems and domiciled organisms. Due to the large quantities of microplastics already distributed worldwide, comparative studies to investigate the associated hazards, distribution patterns, and abundances are becoming increasingly important. Due to varying efforts and budgets, there is still no homogenized detection method for microplastics in the environment, which severely compromises the comparability and reliability of results between previous studies. In this study, we compare the efficacy, degradative effect on microplastics, and microplastic recovery rates of different digestion and separation methods for isolating microplastics from mass-limited environmental samples with high biogenic content. Our results show that the most gentle and effective isolation method is an adsorption-based technique that exploits the lipophilic properties of plastic for separation. This technique achieves an average microplastic recovery rate of 98.0 ± 3.8% and a matrix removal of 96.3 ± 0.3% at low cost and minimum effort. To examine the applicability of this technique to natural environmental samples, eight sediments and two plankton net samples from the South China Sea were selected to determine microplastic abundances. In the analyzed sediment samples, 0–9 microplastic items per 10 g sediment d. w. were found, while 17–25 items per m3 were detected in net samples. Considering the respective mean plastic density, this corresponds to a calculated microplastic mass of 0–39 μg (10 g d.w.)−1 and 3.7–7.1 μg m−3 in sediment and water samples, respectively. This study represents a new way of microplastic extraction from matrix-rich mass-limited samples with high accuracy and easy feasibility at low costs, which would be useful as a worldwide homogenized method in future microplastic research projects and related data comparability.

Rapid detection of estrogen compounds using surface-enhanced Raman spectroscopy with a Zn/Au-Ag/Ag sandwich-structured substrate

In this paper, SERS substrates with Zn/Au-Ag/Ag sandwich-structures are prepared for detection of estrogen compounds. The substrates exhibit a high SERS activity for the rough surface with massive Raman “hot spots” and the interfacial charge transfer that favors the measured molecule adsorption. With the substrates, the estrogen compounds, estrone (E1) and β-estradiol (E2), show characteristic Raman spectral features with different laser exciting wavelengths, and have little interference from humic acids, potential environmental presence The proposed technique, with initially established concentration-SERS relationships, demonstrates high sensitivity with a wide dynamic range, and is very promising for further application to investigate the occurrence, transport and transformation of estrogens in natural environmental samples. A Zn/Au-Ag/Ag sandwich-structured SERS substrates are prepared and exhibit high SERS activity and specificity for detecting Estrone (E1) and β-estradiol (E2), While the SERS spectra of humic acids absorbed on Zn/Au-Ag/Ag sandwich-structures substrates are so weak that have little effect on the E1 and E2 characteristic peaks, which is of great significance to the actual detection in water environment. • Zn/Au-Ag/Ag sandwich-structured SERS substrates are prepared, which exhibit high SERS activity and specificity. • E1 and E2 possess characteristic Raman spectra-specificity at different laser exciting wavelengths. • The Zn/Au-Ag/Ag sandwich-structures substrates are of great significance to the actual detection in water environment.

A new reversible fluorescent chemosensor based on rhodamine for rapid detection of Al(III) in natural environmental water samples and living organisms

A fluorescence sensor RBKB with high selectivity and sensitivity to Al3+ was designed and synthesized. UV–Vis and fluorescence spectra showed that the probe had a good response to Al3+ in EtOH/H2O (1:1, v/v) solution and the response time is very short. The process of detecting Al3+ is accompanied by the probe solution changing from colorless to pink, which has a good visual effect. The reversible type of the probe and Al3+ was confirmed by adding EDTA. Meanwhile, the probe has a low detection limit of 0.177 μM. In addition, the probe can be used for the detection of Al3+ in actual environmental water samples with a high recovery rate. It is worth mentioning that RBKB can be used to detect Al3+ in living cells, zebrafish, and plant tissues, which has high biological significance.

Application of ionizing radiation for removal of endocrine disruptor bisphenol A from waters and wastewaters

The source of the residues of anthropogenic endocrine disruptor known as bisphenol A (BPA) in the natural environment and foods is both production and very wide use of several classes of polymers. Because of the documented inefficiency of BPA removal from waters and wastewaters using conventional treatment methods, several advanced oxidation processes (AOPs) employing hydroxyl radicals (OH) were developed for this purpose in the recent decade. In this work, especially efficient removal of BPA was performed with the use of OH radicals, which are formed from water radiolysis by irradiation with γ-rays. For the initial BPA level 10 mg L-1 (43.9 μM) the pseudo first order rate-constant for the reaction of OH with BPA in neutral, aerated solutions was evaluated to be 0.392 min−1 (6.23 kGy−1), which can be also much higher for lower initial BPA concentration. The possibility to predict the yield of radiolytic BPA decomposition based on Total Organic Carbon content of irradiated natural environmental samples was demonstrated. A detailed mechanism of radical reactions involving OH radicals and superoxide radical anions (O2−) was proposed leading to the formation of decomposition products which were identified by LC/MS analysis. Moreover, the changes in the cytotoxicity of γ-irradiated BPA solutions were examined for two cell lines of human origin, namely liver carcinoma cells HepG2, and breast cancer cells MDA-MB-231.

Validation and Correction for 208Tl Activity to Assay 232Th in Equilibrium with Its Daughters

The natural radioactivity measurements and analysis of 232Th have been studied using γ-ray spectroscopy depending on its decay daughters in equilibrium; 208Tl of 583.19 keV, 228Ac of (911.2 and 968.97 keV) and 212Pb of 238.63 keV. When using these gamma transitions to calculate the 232Th specific activity, the 208Tl daughter of 583.19 keV gamma line with its 0.845 branching ratio gives activity of approximately 33.94% less than the other gamma transitions. This article is trying to explain and validate this difference and discrepancy that may encounter analysts during calculation of 232Th activity based on 208Tl (583.19 keV) gamma line. Very efficient HpGe detector was used to carry out this work. The MDA and figure of merit as functions of HpGe and energy sensitivity were calculated and tabulated. This issue was verified and validated using Black sand and natural environmental samples. A correction factor was proposed and applied on the 583 keV line of these samples that contain 232Th in equilibrium with its daughters to minimize and eliminate the abovementioned difference in the calculated 232Th specific activity.

A Comparison between the Oil Removal Capacity of Polymer-Coated Magnetic Nanoparticles in Natural and Synthetic Environmental Samples.

Oil spills can have dramatic impacts on the environment. The limitations of current oil remediation techniques have inspired researchers to study the application of nanotechnology for oil cleanup. Previously, we reported essentially 100% removal of a reference MC252 oil using polyvinylpyrrolidone (PVP)-coated iron oxide nanoparticles (NPs) from oil-water mixtures under a wide range of environmentally relevant conditions. Our previous results showed that in the synthetic water samples, the concentration of cations and natural organic macromolecules (NOM) can significantly affect the oil removal efficiency of NPs. Here, we studied the application of these NPs for oil removal from natural freshwater samples and compared the results with the synthetic water samples with the same concentrations of major ions and NOM. For both natural and synthetic samples, concentrations of NOM, calcium, and magnesium were positively correlated with oil removal ( p-value <0.05). NPs show an average of 30% higher oil removal efficiency from natural samples compared to the synthetic samples. Using up to 50 ppm of NP, essentially 100% oil removal was observed under most conditions specially hardwater samples (initial 0.15 g L-1 oil concentration). Results show that these NPs are a facile and reliable technique for removing oil under realistic conditions.

The Influence of Temperature and Nitrogen Source on Cellulolytic Potential of Microbiota Isolated from Natural Environment.

Bacteria from the genus Bacillus are a rich source of commercial enzymes, including amylases, proteases, cellulases, glucose isomerase, and pullulanase. Cellulases account for 15% of the global market of industrial enzymes; thus, new microorganisms producing cellulases in a higher concentration and new ingredients, which can enhance the level of enzyme synthesis, are still needed. Many of cellulose-degrading microorganisms have been isolated so far and characterized in various regions of the world. In this study, we were looking for the bacteria isolated from the natural environment with the high cellulolytic potential, which could be used as components of a biopreparation to accelerate decomposition of postharvest leftovers in agriculture. The 214 bacterial strains were isolated from environmental samples rich in cellulose and their ability to synthesize cellulases were examined using the diffusion method. Six strains, which have the highest diameter of clearing zone both for biomass and supernatant, were selected for identification. Optimization of biosynthesis of the cellulose-degrading enzymes indicated that optimal temperature of this process fluctuated in the range of 21–42°C (depending on the strain and carbon source). The highest cellulolytic activity was observed for the isolates designed as 4/7 (identified as Bacillus subtilis) and 4/18 (identified as Bacillus licheniformis) in a temperature of 32°C. With the use of a desirability function methodology, the optimal medium composition to achieve a simple, cost-efficient process of cellulases production was developed for both strains. These experiments show that microorganisms isolated from natural environmental samples have unique properties and potential for commercial applications (e.g. for biopreparations production).

Development of 231Pa AMS measurements to improve radiological dose assessment from uranium mining and milling

Limited information exists on the movement and partitioning of 235U series radionuclides following their release to the environment from activities associated with the nuclear fuel cycle. Only three isotopes in the series, 235U, 231Pa and 227Ac, have half-lives greater than a month. The extent to which the radiologically-significant isotopes of the 235U series differentiate and fractionate in the environment, and then accumulate in biota, is largely controlled by the chemical properties of these three elements and by their biological uptake. This is particularly the case for biota with life cycles in the order of years. There is therefore potential for changes in the radiation dose received by humans and the environment during, for example, the operational and post-remediation phases of uranium mining practices, particularly where mine sites revert to traditional land uses such as hunting, fishing and camping.Natural activity concentrations of 235U are ∼20 times lower than for 238U. In an environmental context, however, the radiation dose that arises from subsequent members of the 235U decay chain will be determined by their abundance distribution and can exceed that from the 238U series. The half-lives of the protactinium isotopes allow only 231Pa to accumulate independently of its parent radionuclide along the transport pathways and/or through preferential uptake by biota. In particular, 231Pa could make a disproportionately high contribution to the dose if it is preferentially transported and/or taken up.The AMS technique is capable of assessing accumulation of 231Pa in natural environmental samples. We report on a new, safer radiochemical extraction method to prepare the 233Pa isotopic tracer (one that does not use hydrofluoric acid), and on the development of 231Pa AMS measurements at the Australian National University.

Identification of 129I interferences in accelerator mass spectrometry

The identification of interferences to 129In+ (n = 3–6) was conducted with a 5 MV tandem accelerator mass spectrometer at SUERC. In addition to 128Te, the detectable interferences to 12 MeV 129I3+ ions include 43Ca1+ and 86Sr2+ which are likely injected as 43Ca86Sr−, 43Ca32S18O3−, etc. whereas those to 15 MeV 129I4+ ions include 32S1+ injected as 43Ca32S18O3−, 65Cu2+ as 63Cu65Cu1H−, 97Mo3+ as 97Mo16O2−. The 18 MeV 129I5+ ions might be interfered by 77Se3+ and 104Pd4+ (or 104Ru4+) and the 21 MeV 129I6+ ions by 43Ca2+, 65Cu3+, 86Sr4+ and 108Pd5+ (or 107Ag5+, 108Cd5+). Apart from 128Te, these ions can be fully separated from 129I in the gas ionization detector equipped with a thin SiN membrane window and propane gas, which contributes negligibly to the 129I-AMS detection for samples after careful chemical preparation. Although the 129I background is mainly controlled by Te content and the source memory, the rareness of Te in natural environmental samples results in our routine background 129I/127I level in range of ∼10−14. The precision and accuracy of 3% can be routinely achieved at 129I/127I > 10−12 level at SUERC.