Use of lead-210 as a novel tracer for lead (Pb) sources in plants

Potentially Toxic Elements in Urban-Grown Lettuce: Effectiveness of Washing Procedures, Risk Assessment, and Isotopic Fingerprint

This study investigates the presence of potentially toxic elements (PTEs) in lettuce (Lactuca sativa L.) grown in urban gardens in a highly industrialized city in Brazil and evaluates the effectiveness of different washing methods in reducing contamination. Ten elements (arsenic (As), barium (Ba), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn)) were analyzed for their concentration, and a health risk assessment was performed. The results showed that Pb concentrations in lettuce from gardens near the Capuava Petrochemical Complex reached 0.77 mg kg-1, exceeding both national and international safety limits. The most effective washing procedure involved the use of sodium hypochlorite, which reduced As by 46%, Pb by 48%, and V by 52%. However, elements such as Ba, Cd, Cr, and Ni showed limited reductions of less than 10% across all washing methods. Health risk assessments revealed a particular concern for children, with the total cancer risk (TCR) exceeding acceptable limits in some gardens. Isotopic analysis of Pb revealed that atmospheric pollution from gasoline emissions and industrial activities were the primary sources of contamination. The elevated levels of Pb, Cr, and As highlight the need for targeted health education in local communities, especially regarding the importance of proper washing techniques. Risk management strategies, including improved contamination control and public awareness, are crucial to minimize exposure to these harmful elements, particularly in vulnerable populations like children.

Recent progresses in analytical method development for 210Pb in environmental and biological samples

As a decay product of uranium series, 210Pb spreads widely in the nature and imposes strong radiological and chemical toxicity. It is vital to establish reliable and efficient radioanalytical methods for 210Pb determination to support environment and food radioactivity monitoring programs. This article critically reviews analytical methods developed for determining 210Pb in environmental and biological samples, especially new development in recent years. Techniques applied throughout different analytical steps including sample pretreatment, separation, purification, and detection are summarized and their pros and cons are discussed to provide a holistic overview for 210Pb environmental and biological assay.

Anthropogenic Land Use and Land Cover Change as Potential Drivers of Sediment Sources in the Upper Crocodile River, North West Province, South Africa

In this study, we investigated the accelerating pace of anthropogenic land use and land cover change (LULCC) disturbance, which has generated enormous impacts on the Crocodile River. Spot images from 1996, 2009 and 2022 were used to generate the land use maps and quantify the changes. A supervised classification with the maximum likelihood classifier was used to classify the images. Sediment sources were classified into two sources, revealed by erosional characteristics in the catchment. A gamma spectrometry detector, high-purity germanium (HPGe) "Well" detector by Canberra and inductively coupled plasma mass spectrometry (ICP-MS) were used for the analysis of the samples. The results revealed that from 1996-2022, built-up areas, bare land and water bodies increased by 3.48%, 2.47% and 1.90%, respectively. All the LULCC classes increased annually from 1996-2022, except for grassland, which shrunk. The results of the radionuclides analysis showed that ²¹⁰Pb_ex was found to be a more effective tracer than ¹³⁷Cs. The mass balance model revealed that subsurface sources contributed 60%, while surface sources contributed 40%, of the sediment load in the river. This research provides valuable information necessary for integrated catchment management policies for future LULCC and soil erosion to be adopted.

Radiological impact of an active quarry in the Papuk Nature Park, Croatia

Papuk Nature Park, unlike most similar parks and preserves in the world, contains active quarries. Quarries dig stone from the ground, creating dust and exposing deeper, potentially more radioactive layers. Since the forest trails in the Park lead right up to the quarries, we believed it was important to determine the radiological impact of the quarries on the Park environment. We measured ambient dose rate equivalent H*(10) and sampled moss at 26 Park locations along two of four quarries, along the road between them, and near Lake Orahovac, a very popular tourist destination close to the quarries. Moss is a standard bioindicator of exposure to heavy metals, including radionuclides. Using-gamma ray spectrometry we determined the activity concentration of ¹³⁷Cs and of representative naturally occurring radionuclides – ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, and ⁴⁰K – in sampled moss. H*(10) at selected locations was similar to the background H*(10) measured continuously all over Croatia. The ranges of measured activity concentrations of ¹³⁷Cs and naturally occurring radionuclides in moss did not differ significantly from other parts of Croatia and nearby countries.

Sedimentation rates and sediment age of the high-altitude cold desert Ramsar Wetland, the Chandratal, inferred from radionuclide (210Pb and 137Cs) technique

In the current scenario, the pristine Himalayan Wetlands are under endangerment due to higher sedimentation rate, including siltation, reduction of ecological value, pollution, and significant anthropogenic encroachment along with advanced civilization. The more increased sedimentation reduces the depth and existing expansion of the Wetland. This study articulates the record of sedimentation in the Chandratal present in Western Himalaya, Himachal Pradesh, India, at the altitude of 4300 m. The sedimentation rate of the Chandratal was calculated based on a 1-m core sample considering isotopes of ¹³⁷Cs and ²¹⁰Pb dating techniques. The present study based on the Constant Rate of Supply (CRS) model of ²¹⁰Pb reveals that the Wetland experienced an average sedimentation rate of 1.75 ± 0.04 cm/year during the last 63 years observed from 1953 to 2016. The ¹³⁷Cs peak method-based calculated sedimentation rate of the Chandratal is 1.6 ± 0.02 cm/year representing the years for about 62 years from 1954 to 2016. The Wetland's functional survival prevalence was estimated to be 420 and 459 years based on ²¹⁰Pb and ¹³⁷Cs dating techniques, respectively. The study communicates that the magnified human interference in the catchment area of the Chandratal is accountable for the faster sedimentation in recent years.

Sorption Behavior and Aerosol-Particulate Transitions of 7Be, 10Be, and 210Pb: A Basis for Fallout Radionuclide Chronometry

We investigated the partitioning of ⁷Be, ¹⁰Be, and ²¹⁰Pb aerosols between operationally dissolved and >0.5 μm particulate fractions in wet and dry atmospheric deposition. Bulk deposition in situ-log(K_D) averaged 4.27 ± 0.46 for ⁷Be and 4.79 ± 0.59 for ²¹⁰Pb (±SD, n = 163), with corresponding activity-fractions particulate (f_P) = 24 and 48%. K_D was inversely correlated with particulate mass concentration (p_C), a particle concentration effect (p.c.e.) that indicates that dissolved ⁷Be and ²¹⁰Pb are bound to submicron colloids. Experimental desorption-K_D was higher than in situ by a factor of 20 for ⁷Be and 4 for ²¹⁰Pb (n = 27), indicating that FRN sorption to particulates was irreversible. ⁷Be:¹⁰Be ratios confirmed that colloidal and particulate fractions were geochemically distinct, with corresponding ages of 120 ± 30 and 260 ± 45 days, respectively [mean ± SE, n = 9, p = 0.011]. Fractions particulate f^Be7, f^Be10, and f^Pb210 each increased with ⁷Be:¹⁰Be bulk age, a particle-age effect (p.a.e). In multiple regression, f^Be7 was best predicted by N, Mn, Al, and Ni [R² = 0.75, p < 0.0001], whereas f^Pb relied on N, S, Fe, and Mn [R² = 0.69, p < 0.0001]. Despite differences in magnitude and controls on partitioning, the ratio f^Be:f^Pb converged to 1 with p_C in the range of 10-100 mg L^-1. Given sufficient solid surfaces, irreversible sorption and p.a.e. form a basis for ⁷Be:²¹⁰Pb chronometry of aerosol biogeochemical cycling.

Dosimetry and Calorimetry Performance of a Scientific CMOS Camera for Environmental Monitoring

This paper explores the prospect of CMOS devices to assay lead in drinking water, using calorimetry. Lead occurs together with traces of radioisotopes, e.g., 210Pb, producing g-emissions with energies ranging from 10 keV to several 100 keV when they decay; this range is detectable in silicon sensors. In this paper we test a CMOS camera (OXFORD INSTRUMENTS Neo 5.5) for its general performance as a detector of X-rays and low energy g-rays and assess its sensitivity relative to the World Health Organization upper limit on lead in drinking water. Energies from 6 keV to 60 keV are examined. The CMOS camera has a linear energy response over this range and its energy resolution is for the most part slightly better than 2%. The Neo sCMOS is not sensitive to X-rays with energies below ~10 keV. The smallest detectable rate is 40 ± 3 mHz, corresponding to an incident activity on the chip of 7 ± 4 Bq. The estimation of the incident activity sensitivity from the detected activity relies on geometric acceptance and the measured efficiency vs. energy. We report the efficiency measurement, which is 0.08(2)% (0.0011(2)%) at 26.3 keV (59.5 keV). Taking calorimetric information into account we measure a minimal detectable rate of 4 ± 1 mHz (1.5 ± 0.1 mHz) for 26.3 keV (59.5 keV) g-rays, which corresponds to an incident activity of 1.0 ± 0.6 Bq (57 ± 33 Bq). Toy Monte Carlo and Geant4 simulations agree with these results. These results show this CMOS sensor is well-suited as a g- and X-ray detector with sensitivity at the few to 100 ppb level for 210Pb in a sample.

A comprehensive review of biogeochemical distribution and fractionation of lead isotopes for source tracing in distinct interactive environmental compartments

Lead (Pb) is a non-essential and extremely noxious metallic-element whose biogeochemical cycle has been influenced predominantly by increasing human activities to a great extent. The introduction and enrichment of this ubiquitous contaminant in the terrestrial-environment has a long history and getting more attention due to its adverse health effects to living organisms even at very low exposure levels. Its lethal-effects can vary widely depending on the atmospheric-depositions, fates and distribution of Pb isotopes (i.e., ²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb &²⁰⁸Pb) in the terrestrial-environment. Thus, it is essential to understand the depositional behavior and transformation mechanism of Pb and the factors affecting Pb isotopes composition in the terrestrial-compartments. Owing to the persistence nature of Pb-isotopic fractions, regardless of ongoing biogeochemical-processes taking place in soils and in other interlinked terrestrial-compartments of the biosphere makes Pb isotope ratios (Pb-IRs) more recognizable as a powerful and an efficient-tool for tracing the source(s) and helped uncover pertinent migration and transformation processes. This review discusses the ongoing developments in tracing migration pathway and distribution of lead in various terrestrial-compartments and investigates the processes regulating the Pb isotope geochemistry taking into account the source identification of lead, its transformation among miscellaneous terrestrial-compartments and detoxification mechanism in soil-plant system. Additionally, this compendium reveals that Pb-pools in various terrestrial-compartments differ in Pb isotopic fractionations. In order to improve understanding of partition behaviors and biogeochemical pathways of Pb isotope in the terrestrial environment, future works should involve investigation of changes in Pb isotopic compositions during weathering processes and atmospheric-biological sub-cycles.

Lead seasonality in humans, animals, and the natural environment

Lead adversely impacts the health of humans, animals, and the natural environment. Higher lead burdens in warm weather occur in humans, domesticated and wild animals; land and water species; urban and rural, developed and pristine environments. The array of evidence suggests that lead seasonality is multifactorial within the natural world, including humans. Seasonally higher temperatures, solar radiation, humidity and anthropogenic pollution result in lower pH (acidification) in air, water and soil. Environmental acidification increases lead's bioavailability and mobility thus intensifying human, animal and plant exposures. In addition, lead seasonality in the biosphere is influenced by higher growth rates, slightly increased exposures, and more Vitamin D metabolism. Methodologically, we applied a One Health perspective to EPA's Integrated Science Assessments of Lead to review the published literature, supplemented with subsequent and related publications to assess data on the seasonality of lead exposure across species and through the earth's systems. Our integrated assessment suggests that: 1) 'Seasonality' is a multifactorial, terrestrial phenomenon affecting the natural world; human activities have exacerbated natural cyclicities that impact lead exposures across species. 2) To be sustainable, human lead remediation strategies must consider the total environment. 3) Global warming and climate change events may increase lead exposures and toxicity to all species throughout the natural environment.

A quantitative spectral component analysis method based on maximum likelihood

In spectroscopy, the compositional analysis of the spectrum is important, such as extracting information about the species of spectral objects contributing to spectral data from an emission spectrum of photon energy. A quantitative spectral component analysis method based on Maximum Likelihood Estimation using Expectation Maximization (MLEM) is developed, which could quantitatively decompose out the components of the measured spectrum of low counts and surpass conventional techniques which belong to classification or regression. Abundant experimental and simulated spectra data on gamma-ray spectrum of radionuclides are presented to demonstrate and evaluate this method, while the ingredient radionuclides in the mixed spectrum are identified accurately with high precision. It will be a powerful and alternative method recommended for the circumstances needing fast and quantitative spectral analysis, including radionuclide identification (gamma-ray spectra), biomass or mineral composition (near-infrared spectra), laser-induced breakdown spectra and other spectroscopy scenarios.

Legacy Lead Stored in Catchments Is the Dominant Source for Lakes in the U.K.: Evidence from Atmospherically Derived 210Pb

There has been a considerable reduction in anthropogenic lead (Pb) emission in the atmosphere in recent decades. However, the reduction in Pb inputs in many lakes does not match this as the Pb stored in catchment upper soil layers, derived from previous deposition, has become an important source although it is difficult to assess quantitatively. This work uses atmospherically deposited ²¹⁰Pb as a tracer to track Pb movement, and so for the first time, we were able to calculate the relative Pb inputs from direct atmospheric deposition and catchment sources to lakes in the U.K. directly. Within individual lake sites, ratios of ²¹⁰Pb/Pb in the catchment terrestrial mosses were normally an order of magnitude higher than those in the catchment surface soils, trapped lake sediments, and the surface sediments in the lake bottom. Results suggest that the Pb isotope signatures in the mosses are close to or dominated by atmospheric depositions, and it is reasonable to use the ratios of ²¹⁰Pb/Pb in terrestrial mosses collected from the lake sites with a high annual rainfall over 2000 mm to represent those in atmospheric depositions. It reveals that after the reduction in Pb emissions, catchment Pb inputs now typically account for more than 95% of the total Pb entering the lakes.

Mobility of 232Th and 210Po in red mud

The valorization of industrial by-products such as red mud became a tempting opportunity, but the understanding of the risks involved is required for the safe utilization of these products. One of the risks involved are the elevated levels of radionuclides (in the 100-1300 Bq/kg range for both the ²³⁸U and ²³² Th decay chains, but usually lower than 1000 Bq/kg, which is the recommended limit for excemption or clearance according to the EU BSS released in 2013) in red mud that can affect human health. There is no satisfactory answer for the utilization of red mud; the main current solution is still almost exclusively disposal into a landfill. For the safe utilization and deposition of red mud, it is important to be able to assess the leaching behaviour of radionuclides. Because there is no commonly accepted measurement protocol for testing the leaching of radionuclides in the EU a combined measurement protocol was made and tested based on heavy metal leaching methods. The leaching features of red mud were studied by methods compliant with the MSZ-21470-50 Hungarian standard, the CEN/TS 14429 standard and the Tessier sequential extraction method for ²³²Th and ²¹⁰Po. The leached solutions were taken to radiochemical separation followed by spontaneous deposition for Po and electrodeposition for Th. The 332 ± 33 Bq/kg ²³²Th content was minimally mobile, 1% became available for distilled water 1% and 6% for Lakanen-Erviö solution; the Tessier extraction showed minimal mobility in the first four steps, while more than 85% remained in the residue. The ²¹⁰Po measurements had a severe disturbing effect in many cases, probably due to large amounts of iron present in the red mud, from the 310 ± 12 Bq/kg by aqua regia digestion, distilled water mobilized 23%, while Lakanen-Erviö solution mobilized ∼13%. The proposed protocol is suitable for the analysis of Th and Po leaching behaviour.