We examine instrumental and methodological capabilities for microscale (10–50 μg of C) radiocarbon analysis of individual compounds in the context of paleoclimate and paleoceanography applications, ...for which relatively high-precision measurements are required. An extensive suite of data for 14C-free and modern reference materials processed using different methods and acquired using an elemental-analyzer–accelerator-mass-spectrometry (EA-AMS) instrumental setup at ETH Zurich was compiled to assess the reproducibility of specific isolation procedures. In order to determine the precision, accuracy, and reproducibility of measurements on processed compounds, we explore the results of both reference materials and three classes of compounds (fatty acids, alkenones, and amino acids) extracted from sediment samples. We utilize a MATLAB code developed to systematically evaluate constant-contamination-model parameters, which in turn can be applied to measurements of unknown process samples. This approach is computationally reliable and can be used for any blank assessment of small-size radiocarbon samples. Our results show that a conservative lower estimate of the sample sizes required to produce relatively high-precision 14C data (i.e., with acceptable errors of <5% on final 14C ages) and high reproducibility in old samples (i.e., F14C ≈ 0.1) using current isolation methods are 50 and 30 μg of C for alkenones and fatty acids, respectively. Moreover, when the F14C is >0.5, a precision of 2% can be achieved for alkenone and fatty acid samples containing ≥15 and 10 μg of C, respectively.
Heavy metal pollution is a global concern with significant ecological and health implications. However, limited studies have focused on assessing heavy metal pollution in soil resulting from heavy ...mineral sand (HMS) mining and processing activities, as well as its effects on ecology and human health. In this study, we assessed heavy metal concentrations in soil samples collected near an HMS mine on the south coast of Kenya using Agilent 7700s ICP-MS. Geo-accumulation index (
I
geo
), enrichment factor (EF), and pollution index (PI) were used to evaluate the extent of soil pollution. The non-carcinogenic (NCR) and carcinogenic (CR) health risk from metal exposure was also evaluated. The results showed moderate pollution by Ti, Mn, Zn, and Nb and high pollution by Cr and As. Mean Cr concentration exceeded the maximum allowable concentration (MAC) and trigger value (TV) by 135 and 61 times, respectively, in topsoil, while As exceeded MAC and TV by 8 and 2 times. Cr and As enrichment factors (EF) were ~ 200 and ~ 25 times higher than the EF threshold value of 1.5. The NCR assessment showed that the population was more susceptible to the effects of As, while the CR assessment indicated a higher risk from Cr and As. Notably, the CR values for both As and Cr exceeded the threshold value of 10
−4
. The findings of this study are essential for developing regulations to monitor, control, and mitigate soil pollution from HMS mining activities and its impact on soil and human health.
Abstract
An increasing number of elderly prostate cancer patients with high-density material hip prostheses are referred for external beam Radiotherapy (EBRT). Radiation treatment of pelvis cancer ...patients with high-density hip prostheses needs special attention due to the artifacts created in the computed tomography (CT) field of view and the radiotherapy dosimetry challenges. This study investigated the pelvic prostate point dose with and without titanium hip prosthesis using a 0.6 cc PTW Farmer ionization chamber, EBT3 Gafchromic films, compared with the EGSnrc Monte Carlo (MC) simulation dose distribution. The doses were measured and simulated in a locally made pelvic phantom. MC and measured doses were compared with the Treatment Planning System (TPS) calculated prostate point dose. The ionization chamber, EBT3 Gafchromic films, and MC doses have a maximum deviation of 6.3 %, 5.7 %, and 7.4 % for 6 MV and 4.2 %, 4.7 %, and 5.5 % for 15 MV photon beam, respectively, when compared with TPS calculated dose. There is a significant difference between the prostate point dose measured with ionization chamber, EBT3 Gafchromic film in comparison MC simulated doses. The MC simulation dose shows the highest deviation especially on the lateral field passing through the prosthesis.
Heavy metal contamination in drinking water is a global health concern. Anthropogenic and geogenic activities exacerbate the concentrations of these metals in surface and groundwater. In this study, ...we sampled drinking water sourced from surface and groundwater resources at the environs of Mrima Hill and the Kwale heavy minerals sand deposit, Kwale County, Kenya. The concentrations of Cr, Ni, Cu, As, Cd, Pb, and U were measured using the inductively coupled plasma mass spectrometer. The water quality indices were evaluated using the weighted arithmetic index method, while the human health risks due to exposure to these heavy metals through the ingestion pathway were assessed using deterministic and probabilistic techniques. The concentrations of Cr and Cd in samples from both study areas exceeded the national and international maximum contaminant levels in drinking water. The concentration levels of Ni, Cu, As, and U in all samples from both study areas were within the recommended values in drinking water. Therefore, the quality of water from both study areas was unsuitable for human consumption due to Cd and Cr contamination. The non-carcinogenic risk assessment also showed that the hazard indices (HI) evaluated for both children and adults at the study areas were higher than unity. In addition, the estimated carcinogenic risks of both population groups were more than the recommended value of 10
–4
. This study shows that the residents near Mrima Hill and the Kwale heavy minerals sand deposit remain susceptible to carcinogenic and non-carcinogenic health risks emanating from exposure to these heavy metals in drinking water.
Excited states up to 3 MeV in the odd-odd 54Mn have been populated in the 54Cr(p,n)54Mn reaction at Ep = 4.5 MeV. Conversion coefficients (αK and απ) were deduced using the NPG method for the first ...time in 54Mn. Multipolarities were unambiguously assigned in 16 transitions for the first time using the obtained conversion coefficient values. Spin and parity has been restricted for three transitions.
Abstract
The contents of the Lanthanides, which are Rare Earth Elements (REE), that show consistent patterns under changing geochemical conditions in uranium ore have been studied. The objective is ...to determine the nuclear forensic parameters inherent to the various uranium ore samples collected from parts of northern Nigeria using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analytical technique for the purpose of baseline data generation and nuclear forensic application. The REE fingerprint obtained in this study suggests that the uranium is of uraninite/pitchblende granitic (vein-type) origin. The REE concentrations varied from 0.011 ± 0.000 ppm to 2.337 ± 0.082 ppm for Riruwai, 0.001 ± 0.000 ppm to 0.035 ± 0.002 ppm for Mika-I, 0.002 ± 0.000 ppm to 0.357 ± 0.007 ppm for Mika-II and 0.001 ± 0.001 ppm to 0.159 ± 0.005 ppm for Michika. A positive correlation between the REEs showed symmetrical chemical properties as well as their overall presence in the samples. The normalised REE/Cl-Chondrites pattern show Light Rare Earth Elements(LREE) enrichment, Heavy Rare Earth Elements (HREE) fractionation with a negative Europium (Eu) anomaly. The ΣLREE/ΣHREE ratio presented varied values for the samples while a negative value of
143
Nd/
144
Nd ratio (0.512638) in the Chondritic Uniform Reservoir (CHUR)
ε
Nd
(-0.64285) suggested LREE uniformity and radiogenic origin.
Abstract
The effects of radiation interaction with materials have been studied over the years on metals, semiconductors, and other alloys. The result of these interactions constitutes microstructural ...effects, like point defects, dislocation loops, and void swellings. The accumulation of these defects results to damage on the macroscopic scale. This study is aimed to predict the magnitude of radiation damage in gold sample due to neutron irradiation. Neutron flux, displacement-per-atom rate, as well as heat deposition, were calculated in MCNP6.2, using the SAFARI-1 reactor model. The total neutron flux and dpa rate in the gold sample were determined to be 2.262 × 10
11
n.cm
−2
.s
−1
and 5.209 × 10
−7
s
−1
respectively. Also, the total heat deposition due to neutrons and photons was 2.515 × 10
−6
W.g
−1
and 0.513 W.g
−1
, respectively. Hence, the predicted neutron dpa and flux for the gold sample in this study suggest a heavy damage regime.
Monsoonal rivers play an important role in the
land-to-sea transport of soil-derived organic carbon (OC). However, spatial
and temporal variation in the concentration, composition, and fate of this
...OC in these rivers remains poorly understood. We investigate soil-to-sea
transport of soil OC by the Godavari River in India using glycerol dialkyl
glycerol tetraether (GDGT) lipids in soils, river suspended particulate
matter (SPM), and riverbed sediments, as well as in a marine sediment core from the Bay
of Bengal. The abundance and composition of GDGTs in SPM and sediments in
the Godavari River differs between the dry and wet season. In the dry
season, SPM and riverbed sediments from the whole basin contain more
6-methyl branched GDGTs (brGDGTs) than the soils. In the upper basin, where
mobilisation and transport of soils is limited due to deficient rainfall and
damming, contributions of 6-methyl brGDGTs in SPM and riverbed sediments are
relatively high year-round, suggesting that they have an aquatic source.
Aquatic brGDGT production coincides with elevated values of the isoprenoid
GDGT-0 / crenarchaeol ratio in SPM and riverbed sediments from the upper basin,
indicating low-oxygen conditions. In the wet season, brGDGT distributions in
SPM from the lower basin closely resemble those in soils, mostly from the
north and east tributaries, corresponding to precipitation patterns. The
brGDGT composition in SPM and sediments from the delta suggests that soil OC
is only effectively transported to the Bay of Bengal in the wet season, when
the river plume extends beyond the river mouth. The sediment geochemistry
indicates that also the mineral particles exported by the Godavari River
primarily originate from the lower basin, similar to the brGDGTs, suggesting
that they are transported together. However, river depth profiles in the
downstream Godavari reveal no hydrodynamic sorting effect on brGDGTs in
either season, indicating that brGDGTs are not closely associated with
mineral particles. The similarity of brGDGT distributions in bulk and
fine-grained sediments (≤ 63 µm) further confirms the absence of
selective transport mechanisms. Nevertheless, the composition of brGDGTs in
a Holocene, marine sediment core near the river mouth appears substantially
different from that in the modern Godavari basin, suggesting that
terrestrial-derived brGDGTs are rapidly lost upon discharge into the Bay of
Bengal and/or overprinted by marine in situ production. The large change in
brGDGT distributions at the river–sea transition implies that this zone is
key in the transfer of soil OC, as well as that of the environmental signal
carried by brGDGTs from the river basin.
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