Improving Equitability and Inclusion for Testing and Detection of Lead Poisoning in US Children.

Policy Points Child lead poisoning is associated with socioeconomic inequity and perpetuates health inequality. Methods for testing and detection of child lead poisoning are ill suited to the current demographics and characteristics of the problem. A three-pronged revision of current testing approaches is suggested. Employing the suggested revisions can immediately increase our national capacity for equitable, inclusive testing and detection. ABSTRACT: Child lead poisoning, the longest-standing child public health epidemic in US history, is associated with socioeconomic inequity and perpetuates health inequality. Removing lead from children's environments ("primary prevention") is and must remain the definitive solution for ending child lead poisoning. Until that goal can be realized, protecting children's health necessarily depends on the adequacy of our methods for testing and detection. Current methods for testing and detection, however, are no longer suited to the demographics and magnitude of the problem. We discuss the potential deployment and feasibility of a three-pronged revision of current practices including: 1) acceptance of capillary samples for final determination of lead poisoning, with electronic documentation of "clean" collection methods submitted by workers who complete simple Centers for Disease Control and Prevention-endorsed online training and certification for capillary sample collection; 2) new guidance specifying the analysis of capillary samples by inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrometry with documented limit of detection ≤0.2 µg/dL; and 3) adaptive "census tract-specific" universal testing and monitoring guidance for children from birth to 10 years of age. These testing modifications can bring child blood lead level (BLL) testing into homes and communities, immediately increasing our national capacity for inclusive and equitable detection and monitoring of dangerous lower-range BLLs in US children.

Industrial wastewater treatment by plant-based bio-filtration.

Constructed wetlands (CWs) represent a natural wastewater treatment process, offering economic and environmental advantages. These systems can remove several components that may cause negative impacts on the environment. Media types and plant species are crucial influencing factors for the removal of contaminants in CWs. The goal of this study is to evaluate the capacity of a CW using Tamarix spp. with three filter media to treat FGD wastewater. Planted and unplanted CWs were set up with varying types of biofilm support media: 3 bioreactors were operated with 50% gravel and 50% zeolite (v/v), 3 with 100% gravel, and 3 with 50% gravel, 25% zeolite, and 25% silage. Planted CWs had the greatest potential to reduce the concentrations of B, K, and NH4+-N in 64.9%, 91.1%, and 92.5%, respectively, when used in addition to the filter composed by 50% gravel + 50% zeolite, which was the only media keeping the plants alive for 60 days. The results showed that the optimal selection of filter media depends on the purpose for which the treatment has been projected for, considering that the types of substrates influenced the nature of the contaminant removal in the CW.

Salinity impact on Constructed wetlands (CWs) is still scarce in the literature. The novelty is the choice of a salt cedar (Tamarix spp.) combined with three filter media types ((1) gravel; (2) gravel and zeolite; (3) gravel, zeolite, and silage) to treat flue gas desulfurization wastewater in CWs. Our findings demonstrate that filter media containing 50% gravel + 50% zeolite can decrease the toxicity of contaminants from FGD wastewater in plants.

Estimating the proportion of bioaccessible lead (BaPb) in household dust wipe samples: a comparison of IVBA and PBET methods.

Established methods for using standardized dust wipes to collect and measure total lead in household dust are readily available but the use of dust wipes to measure bioaccessible lead (BaPb) is less clear. This study compared two in vitro methods for estimating the proportion of BaPb in dust collected into dust wipes including the US-EPA's in-vitro bioaccessible assay (IVBA) method at two pH (1.5 and 2.5) values; and the physiologically based extraction test (PBET 2.5 pH). Two types of simulated household dust samples (Pb-soil contaminated and Pb-paint contaminated) each with three Pb concentrations were created. Equal amounts of simulated dust were applied to a smooth surface and collected following the standard EPA dust wipe protocol and were analyzed for BaPb and total Pb (ASTM-E1644-17, ICP-OES). Estimated BaPb levels differed significantly by the method of extraction. Mean percent BaPb were IVBA pH 1.5, > 90% (Pb-paint) and 59-63% (Pb-soil); IVBA pH 2.5 78-86% (Pb-paint) and 45-50% (Pb-soil); PBET pH 2.5 56 to 61% (Pb-paint) and 41-50% Pb-soil). Particularly for lead-paint contaminated dust, PBET showed significantly greater discrimination as suggested by the broader range of BaPb values and closer approximation to total lead concentrations in simulated household dust samples.

Phosphorus Release and Speciation in Manganese(IV) Oxide and Zeolite-Amended Flooded Soils.

Phosphorus (P) losses from flooded soils and subsequent transport to waterways contribute to eutrophication of surface waters. This study evaluated the effectiveness of MnO2 and a zeolite Y amendment in reducing P release from flooded soils and explored the underlying mechanisms controlling P release. Unamended and amended (MnO2 or zeolite, surface-amended at 5 Mg ha-1) soil monoliths from four clayey-alkaline soils were flooded at 22 ± 2 °C for 56 days. Soil redox potential and dissolved reactive P (DRP), pH, and concentrations of major cations and anions in porewater and floodwater were analyzed periodically. Soil P speciation was simulated using Visual MINTEQ at 1, 28, and 56 days after flooding (DAF) and P K-edge X-ray absorption near-edge structure spectroscopy and sequential fractionation at 56 DAF. Porewater DRP increased with DAF and correlated negatively with pe+pH and positively with dissolved Fe. Reductive dissolution of Fe-associated P was the dominant mechanism of flooding-induced P release. The MnO2 amendment reduced porewater DRP by 30%-50% by favoring calcium phosphates (Ca-P) precipitation and delaying the reductive dissolution reactions. In three soils, the zeolite amendment at some DAF increased porewater and/or floodwater DRP through dissolution of Ca-P and thus was not effective in reducing P release from flooded soils.

Soil Chemistry and the One Health Initiative: Introduction to the Special Section.

Population growth and technical and social changes have always exerted pressure on environmental quality. However, we are experiencing unprecedented change in the rate and scale of human impacts on the environment. The One Health Initiative recognizes that improving the quality of life for humans and other animal species requires a holistic and integrated framework to seek multidisciplinary solutions to global environmental quality challenges. This special section is designed to elucidate the connections among soil health, environmental quality, food safety and security, and human health. Soil chemistry is defined as the field of soil science that deals with the chemical constituents, properties, and reactions of soils. Soil chemistry plays a central role in food production and the protection of human health. Chemical reactions between nutrients or contaminants and soil solids, and the composition of the soil solution and the atmosphere, influence crop growth as well as the quality of our food, air, and water. This collection of nine papers brings together studies that highlight how soil chemical constituents, properties, and reactions can be examined or managed using a multidisciplinary approach to move toward a more efficient, sustainable, nutrient-rich, and low-contaminant food production system that affords protection of soil, water, and human and animal health. We believe that studies such as these are needed to maintain and enhance environmental quality through interdisciplinary scientific approaches for human, animal, and environmental health outcomes.

Iron Oxides Minimize Arsenic Mobility in Soil Material Saturated with Saline Wastewater.

The soil material in constructed wetlands is effective in retaining Se from flue-gas desulfurization (FGD) wastewater (WW), but reducing conditions can enhance native-soil As mobility. A laboratory-based soil column experiment was performed to assess the effectiveness of ferrihydrite (Fh) in minimizing the mobility of native-soil As in water-saturated soil material. A saline FGD WW mixture (i.e., influent) was delivered to columns of untreated and Fh-treated soil for 60 d. One untreated column and one Fh-treated column were then subjected to drying, followed by an additional 30 d of influent delivery. Although the influent was low in As (∼1 µg L) and the soil As level was normal, the total dissolved As concentration of effluent from the untreated columns increased with time, from ∼1 µg L to a maximum of ∼27 µg L. In contrast, effluent from the Fh-treated columns remained low in As (i.e., <5 µg L). The strong correlation between total dissolved Fe and As in the effluent suggested that reductive dissolution of native-soil Fe minerals was responsible for releasing As into solution. Results from X-ray absorption spectroscopy showed newly precipitated Fe minerals in the Fh-treated soil, and the remaining As was mainly As(V) species in both the untreated and Fh-treated soils. Thus, native-soil As mobilized under saturated conditions can be sequestered by adding poorly crystalline Fe oxides to soil prior to saturation. Furthermore, results obtained by drying and rewetting the columns showed that saturated conditions must be maintained to minimize the remobilization of sequestered As and retained Se.

Application of Synchrotron Radiation-based Methods for Environmental Biogeochemistry: Introduction to the Special Section.

To understand the biogeochemistry of nutrients and contaminants in environmental media, their speciation and behavior under different conditions and at multiple scales must be determined. Synchrotron radiation-based X-ray techniques allow scientists to elucidate the underlying mechanisms responsible for nutrient and contaminant mobility, bioavailability, and behavior. The continuous improvement of synchrotron light sources and X-ray beamlines around the world has led to a profound transformation in the field of environmental biogeochemistry and, subsequently, to significant scientific breakthroughs. Following this introductory paper, this special collection includes 10 papers that either present targeted reviews of recent advancements in spectroscopic methods that are applicable to environmental biogeochemistry or describe original research studies conducted on complex environmental samples that have been significantly enhanced by incorporating synchrotron radiation-based X-ray technique(s). We believe that the current focus on improving the speciation of ultra-dilute elements in environmental media through the ongoing optimization of synchrotron technologies (e.g., brighter light sources, improved monochromators, more efficient detectors) will help to significantly push back the frontiers of environmental biogeochemistry research. As many of the relevant techniques produce extremely large datasets, we also identify ongoing improvements in data processing and analysis (e.g., software improvements and harmonization of analytical methods) as a significant requirement for environmental biogeochemists to maximize the information that can be gained using these powerful tools.

Lead Speciation and In Vitro Bioaccessibility of Compost-Amended Urban Garden Soils.

In situ soil amendments can modify the Pb bioavailability by changing soil Pb speciation. Urban soils from three vegetable gardens containing different total Pb concentrations were used. The study evaluated how compost amendment and aging of soil-compost mixture in situ affected the following: (i) soil Pb speciation in the field and (ii) change of soil Pb speciation during an in vitro bioaccessibility extraction mimicking gastric phase dissolution at pH 2.5. X-ray absorption fine structure spectroscopy was used to determine Pb speciation in amended and nonamended soils and residues left after in vitro bioaccessibility extraction of those soils. Compost amendment and aging of compost in the field had a negligible effect on Pb bioaccessibility in the soils. Major Pb species in the soils were Pb sorbed to Fe oxy(hydr)oxide (Pb-Fh) and to soil organic C (Pb-Org). The fraction of Pb-Org was increased as soil-compost mixture aged in the field. During the in vitro extraction, the fraction of Pb-Fh was decreased, the fraction of Pb-Org was increased, and hydroxypyromorphite was formed in both amended and nonamended soils. Freshly incorporated compost enhanced the dissolution of Pb-Fh during the extraction. As soil-compost mixture aged in the field, the dissolution of Pb-Fh was low, demonstrating more stability of the Pb-Fh during the extraction. Compost amendment showed potential to contribute to reduced bioaccessibility of Pb as compost aged in the soil by increasing Pb-Org fraction in the field and stability of Pb-Fh during the in vitro bioaccessibility extraction.

Transport and Transformation of Selenium and Other Constituents of Flue-Gas Desulfurization Wastewater in Water-Saturated Soil Materials.

Constructed wetland treatment systems are used to remove selenium (Se) from flue-gas desulfurization (FGD) wastewater (WW). However, direct confirmation of the mechanism responsible for FGD WW Se retention in soil is lacking. A laboratory-based soil column study was performed to develop an evidence-based mechanism of Se retention and to study the behavior and the retention capacity of FGD WW constituents in water-saturated soil. A deoxygenated 1:1 mixture of FGD WW and raw water was delivered to the columns bottom-up at a flux of 1.68 cm d for 100 d. Some of the columns were flushed with the raw water at the same rate for an additional 100 d. Column effluent was analyzed for constituents of concern. Results showed a complete retention of FGD WW Se in the soil materials. Boron and fluorine were partially retained; however, sulfur, sodium, and chlorine retention was poor, agreeing with field observations. The FGD WW Se was retained in soil near the inlet end of the columns, indicating its limited mobility under reduced conditions. Sequential extraction procedure revealed that retained Se was mainly sequestered as stable/residual forms. Bulk- and micro-X-ray absorption near-edge structure spectroscopy confirmed that Se was mainly retained as reduced/stable species [Se(IV), organic Se, and Se(0)]. This study provides direct evidence for FGD WW Se retention in water-saturated soil via the transformation of oxidized Se into reduced/stable forms.

A soil column study to evaluate treatment of trace elements from saline industrial wastewater.

Industrial wastewater from the flue gas desulfurization (FGD) process is characterized by the presence of trace elements of concern, such as selenium (Se) and boron (B) and relatively high salinity. To simulate treatment that FGD wastewater undergoes during transport through soils in subsurface treatment systems, a column study (140-d duration) was conducted with native Kansas soil and saline FGD wastewater, containing high Se and B concentrations (170 µg/L Se and 5.3 mg/L B) and negligible arsenic (As) concentration (∼1.2 µg/L As). Se, B, and As, and dissolved organic carbon concentrations and organic matter spectroscopic properties were measured in the influent and outflow. Influent Se concentrations were reduced by only ∼half in all treatments, and results suggest that Se sorption was inhibited by high salinity of the FGD wastewater. By contrast, relative concentrations (C/Co) of B in the outflow were typically <10%, suggesting that B sequestration may have been enhanced by higher salinity. Unexpected elevated As concentrations in the outflow (at >150 µg/L in the treatment with labile organic carbon addition) suggest that soils not previously known to be geogenic arsenic sources have the potential to release As to groundwater in the presence of high salinity wastewater and under reducing conditions.

Lead in Urban Soils: A Real or Perceived Concern for Urban Agriculture?

Urban agriculture is growing in cities across the United States. It has the potential to provide multiple benefits, including increased food security. Concerns about soil contamination in urban areas can be an impediment to urban agriculture. Lead is the most common contaminant in urban areas. In this paper, direct (soil ingestion via outdoor and indoor exposure) and indirect (consumption of food grown in Pb-contaminated soils) exposure pathways are reviewed. It is highly unlikely that urban agriculture will increase incidences of elevated blood Pb for children in urban areas. This is due to the high likelihood that agriculture will improve soils in urban areas, resulting in reduced bioavailability of soil Pb and reduced fugitive dust. Plant uptake of Pb is also typically very low. The exceptions are low-growing leafy crops where soil-splash particle contamination is more likely and expanded hypocotyl root vegetables (e.g., carrot). However, even with higher bioaccumulation factors, it is not clear that the Pb in root vegetables or any other crops will be absorbed after eating. Studies have shown limited absorption of Pb when ingested with food. Best management practices to assure minimal potential for exposure are also common practices in urban gardens. These include the use of residuals-based composts and soil amendments and attention to keeping soil out of homes. This review suggests that benefits associated with urban agriculture far outweigh any risks posed by elevated soil Pb.

Synchrotron-based X-Ray Spectroscopy Studies for Redox-based Remediation of Lead, Zinc, and Cadmium in Mine Waste Materials.

Several studies have examined the effect of submergence on the mobility of metals present in mine waste materials. This study examines the effect of organic carbon (OC) and sulfur (S) additions and submergence time on redox-induced biogeochemical transformations of lead (Pb), zinc (Zn), and cadmium (Cd) present in mine waste materials collected from the Tri-State mining district located in southeastern Kansas, southwestern Missouri, and northeastern Oklahoma. A completely randomized design, with a two-way treatment structure, was used for conducting a series of column experiments. Two replicates were used for each treatment combination. Effluent samples were collected at several time points, and soil samples were collected at the end of each column experiment. Because these samples are highly heterogeneous, we used a variety of synchrotron-based techniques to identify Pb, Zn, and Cd speciation at both micro- and bulk-scale. Spectroscopic analysis results from the study revealed that the addition of OC, with and without S, promoted metal-sulfide formation, whereas metal carbonates dominated in the nonamended flooded materials and in mine waste materials only amended with S. Therefore, the synergistic effect of OC and S may be more promising for managing mine waste materials disposed of in flooded subsidence mine pits instead of individual S or OC treatments. The mechanistic understanding gained in this study is also relevant for remediation of waste materials using natural or constructed wetland systems.

Bioavailability-Based In Situ Remediation To Meet Future Lead (Pb) Standards in Urban Soils and Gardens.

Recently the Centers for Disease Control and Prevention lowered the blood Pb reference value to 5 µg/dL. The lower reference value combined with increased repurposing of postindustrial lands are heightening concerns and driving interest in reducing soil Pb exposures. As a result, regulatory decision makers may lower residential soil screening levels (SSLs), used in setting Pb cleanup levels, to levels that may be difficult to achieve, especially in urban areas. This paper discusses challenges in remediation and bioavailability assessments of Pb in urban soils in the context of lower SSLs and identifies research needs to better address those challenges. Although in situ remediation with phosphate amendments is a viable option, the scope of the problem and conditions in urban settings may necessitate that SSLs be based on bioavailable rather than total Pb concentrations. However, variability in soil composition can influence bioavailability testing and soil amendment effectiveness. More data are urgently needed to better understand this variability and increase confidence in using these approaches in risk-based decision making, particularly in urban areas.

Potential bioavailability of lead, arsenic, and polycyclic aromatic hydrocarbons in compost-amended urban soils.

Urban soils may contain harmful concentrations of contaminants, such as lead (Pb), arsenic (As), and polycyclic aromatic hydrocarbons (PAHs), that can transfer from soil to humans via soil ingestion and consumption of food crops grown in such soils. The objective of this research was to assess the effectiveness of adding different compost types to reduce both direct (soil-human) and indirect (soil-plant-human) exposure of Pb, As, and PAHs to humans. A field experiment was conducted in 2011 and 2012 at an urban garden site with elevated concentrations of Pb (475 mg kg), As (95 mg kg), and PAHs (23-50 mg kg). Soil amendments were composted biosolids, noncomposted biosolids, mushroom compost, leaf compost, and a nonamended control. Collard greens, tomatoes, and carrots were then grown in the amended and nonamended soils and nonamended soils that received urea in 2011. At the beginning of the second season, N-P-K fertilizer was added to all plots. The potential for direct and indirect exposure was evaluated. Soil Pb bioaccessibility was 1 to 4.3%, and As bioaccessibility was 7.3 to 12.3%. Composted biosolids reduced the bioaccessibility of soil Pb by ∼17% compared with the control but temporarily increased the bioaccessibility of As by ∼ 69% compared with the control when soluble inorganic P concentration in soil was elevated by P fertilizer application in 2012. The bioaccessibility of soil Pb decreased by ∼38% in all treatments when soluble inorganic P concentration in soil was elevated by P fertilizer. Compost amendments reduced the concentrations of low molecular weight PAHs in soil. Regardless of the treatments, the concentrations of Pb, As, and PAHs measured in the vegetables were low or nondetectable, except for Pb in carrots. Consumption of vegetables grown at this site will cause insignificant transfer of Pb, As, and PAHs to humans.

Safety of gardening on lead- and arsenic-contaminated urban brownfields.

Elevated levels of lead (Pb) and arsenic (As) are not uncommon for urban soils. Test plots were established at urban gardens in Tacoma and Seattle, WA. The Tacoma site was contaminated with Pb (51-312 mg kg) and As (39-146 mg kg), and the Seattle site had high Pb soil concentrations ranging from 506 to 2022 mg kg and As concentrations of <20 mg kg. The efficacy of biosolids mix and compost amendment in reducing Pb and As concentrations in three vegetables (carrots, lettuce, and tomatoes) and the bioaccessibility of soil Pb and As were evaluated. Food-chain transfer of Pb and As were evaluated by measuring plant Pb and As concentrations after kitchen-style washing, a laboratory cleaning procedure, or peeling. The experimental design was a randomized complete block with a split-plot arrangement. Tacoma site treatments included a Class A biosolids mix (TAGRO) with dolomite, and soil at the Seattle site was amended with Cedar-Grove compost (CGC) plus dolomite. TAGRO amendment diluted soil Pb by 10 to 23% and As by 12 to 25% at the Tacoma site, and CGC + dolomite resulted in 20 to 50% dilution in soil Pb at the Seattle site. Both amendments reduced Pb concentrations in vegetables by 50 to 71%, and As reductions ranged from 46 to 80%. At the Tacoma site, Pb concentrations (dry weight basis) in carrots, lettuce, and tomatoes ranged from 8.89 to 25.0, from 0.37 to 3.83, and from 0.54 to 1.24 mg kg, respectively. Plant As concentrations were below 703 µg kg (dry weight) for the vegetables and followed the order lettuce > carrot > tomato. Food-chain transfer of Pb and As in vegetables grown in contaminated urban soils were reduced by laboratory cleaning.

Field evaluations on soil plant transfer of lead from an urban garden soil.

Lead (Pb) is one of the most common contaminants in urban soils. Gardening in contaminated soils can result in Pb transfer from soil to humans through vegetable consumption and unintentional direct soil ingestion. A field experiment was conducted in 2009 and 2010 in a community urban garden with a soil total Pb concentration of 60 to 300 mg kg. The objectives of this study were to evaluate soil-plant transfer of Pb, the effects of incorporation of a leaf compost as a means of reducing Pb concentrations in vegetables and the bioaccessibility of soil Pb, and the effects of vegetable cleaning techniques on the Pb concentrations in the edible portions of vegetables. The amount of compost added was 28 kg m. The tested plants were Swiss chard, tomato, sweet potato, and carrots. The vegetable cleaning techniques were kitchen cleaning, laboratory cleaning, and peeling. Compost addition diluted soil total Pb concentration by 29 to 52%. Lead concentrations of the edible portions of vegetables, except carrot, were below the maximum allowable limits of Pb established by the Food and Agriculture Organization and the World Health Organization. Swiss chard and tomatoes subjected to kitchen cleaning had higher Pb concentrations than laboratory-cleaned plants. Cleaning methods did not affect Pb concentrations in carrots. Bioaccessible Pb in the compost-added soils was 20 to 30% less than that of the no-compost soils; compost addition reduced the potential of transferring soil Pb to humans via vegetable consumption and direct soil ingestion. Thorough cleaning of vegetables further reduced the potential of transferring soil Pb to humans.

Micro-x-ray fluorescence, micro-x-ray absorption spectroscopy, and micro-x-ray diffraction investigation of lead speciation after the addition of different phosphorus amendments to a smelter-contaminated soil.

The stabilization of Pb on additions of P to contaminated soils and mine spoil materials has been well documented. It is clear from the literature that different P sources result in different efficacies of Pb stabilization in the same contaminated material. We hypothesized that the differences in the efficacy of Pb stabilization in contaminated soils on fluid or granular P amendment addition is due to different P reaction processes in and around fertilizer granules and fluid droplets. We used a combination of several synchrotron-based techniques (i.e., spatially resolved micro-X-ray fluorescence, micro-X-ray absorption near-edge structure spectroscopy, and micro-X-ray diffraction) to speciate Pb at two incubation times in a smelter-contaminated soil on addition of several fluid and granular P amendments. The results indicated that the Pb phosphate mineral plumbogummite was an intermediate phase of pyromorphite formation. Additionally, all fluid and granular P sources were able to induce Pb phosphate formation, but fluid phosphoric acid (PA) was the most effective with time and distance from the treatment. Granular phosphate rock and triple super phosphate (TSP) amendments reacted to generate Pb phosphate minerals, with TSP being more effective at greater distances from the point of application. As a result, PA and TSP were the most effective P amendments at inducing Pb phosphate formation, but caution needs to be exercised when adding large amounts of soluble P to the environment.

Organic amendments temporarily change arsenic speciation and bioaccessibility in a lead and arsenic co-contaminated urban soil.

Organic amendments often reduce the bioaccessibility of soil lead (Pb) but not that of soil arsenic (As). The effect of Pb on As bioaccessibility is rarely studied in co-contaminated soils. In a field study, we assessed the effect of mushroom compost, leaf compost, noncomposted biosolids, and composted biosolids amendments on As speciation in a co-contaminated (As and Pb) soil at 7, 349, and 642 days after amending soils and the change of As speciation during an in vitro bioaccessibility extraction (gastric solution, pH 2.5) using bulk X-ray absorption near-edge structure spectroscopy. Soil was contaminated by coal combustion and other diffuse sources and had low As bioaccessibility (7%-12%). Unamended soil had As(III) sorbed onto pyrite (As(III)-pyrite; ∼60%) and As(V) adsorbed onto Fe oxy(hydr)oxides (As(V)-Fh; ∼40%). In amended soils, except in composted biosolids-amended soils, at 7 days, As(V)-Fh decreased to 15%-26% and redistributed into As(III)-Fh and/or As(III)-pyrite. This transformation was most pronounced in mushroom compost amended soil resulting in a significant (46%) increase of As bioaccessibility compared to the unamended soil. Composted biosolids-amended soils had relatively stable As(V)-Fh. Lead arsenate formed during the in vitro extraction in amended soils, except in composted biosolids-amended soils. Arsenic speciation and bioaccessibility were similar in 349- and 642-day in all the amended and unamended soils. Reduction of As(V)-Fh to As(III) forms in the short term in three of the amended soils showed the potential to increase As bioaccessibility. The formation of stable lead arsenate during the in vitro extraction would counteract the short-term increase of As bioaccessibility in those amended soils.

Phosphorus fractions and speciation in an alkaline, manured soil amended with alum, gypsum, and Epsom salt.

Snowmelt runoff is a dominant pathway of phosphorus (P) losses from agricultural lands in cold climatic regions. Soil amendments effectively reduce P losses from soils by converting P to less soluble forms; however, changes in P speciation in cold climatic regions with fall-applied amendments have not been investigated. This study evaluated P composition in soils from a manured field with fall-amended alum (Al2(SO4)3·18H2O), gypsum (CaSO4·2H2O), or Epsom salt (MgSO4·7H2O) using three complementary methods: sequential P fractionation, scanning electron microscopy with energy-dispersive X-rays (SEM-EDX) spectroscopy, and P K-edge X-ray absorption near-edge structure spectroscopy (XANES). Plots were established in an annual crop field in southern Manitoba, Canada, with unamended and amended (2.5 Mg ha-1) treatments having four replicates in 2020 fall. Soil samples (0-10 cm) taken from each plot soon after spring snowmelt in 2021 were subjected to P fractionation. A composite soil sample for each treatment was analyzed using SEM-EDX and XANES. Alum- and Epsom salt-treated soils had significantly greater residual P fraction with a higher proportion of apatite-like P and a correspondingly lower proportion of P sorbed to calcite (CaCO3) than unamended and gypsum-amended soils. Backscattered electron imaging of SEM-EDX revealed that alum- and Epsom salt-amended treatments had P-enriched microsites frequently associated with aluminum (Al), iron (Fe), magnesium (Mg), and calcium (Ca), which was not observed in other treatments. Induced precipitation of apatite-like species may have been responsible for reduced P loss to snowmelt previously reported with fall application of amendments.

Stability of blood lead levels in children with low-level lead absorption.

Current child blood lead (Pb) screening guidelines assume that blood lead levels (BLLs) are relatively stable over time, and that only youngest children are vulnerable to the damaging effects of lower-range BLLs. This study aimed to test the stability of lower-range (≤ 10 µg/dL) child BLLs over time, and whether lower-range BLLs diminished with age among children aged 6 months to 16 years living in a lower-income neighborhood with a density of pre-1986 housing and legacy contamination. Age, sex, family income, age of residence, and/or residence proximity to point sources of Pb, were tested as potential additional factors. Capillary blood samples from 193 children were analyzed by inductively coupled plasma mass spectrometry (ICPMS). Multiple imputation was used to simulate missing data for 3 blood tests for each child. Integrated Growth Curve models with Test Wave as a random effect were used to test BLL variability over time. Among N = 193 children tested, at Time 1 testing, 8.7% had the BLLs ≥ 5 µg/dL (CDC "elevated" BLL reference value at the time of data collection) and 16.8% had BLLs ≥ 3.5 µg/dL (2021 CDC "elevated" BLL reference value). Modeling with time as a random effect showed that the variability of BLLs were attributable to changes within children. Moreover, time was not a significant predictor of child BLLs over 18 months. A sex by age interaction suggested that BLLs diminished with age only among males. Of the additional environmental factors tested, only proximity to a major source of industrial or vehicle exhaust pollution predicted child BLL variability, and was associated with a small, but significant BLL increase (0.22 µg/dL). These findings suggest that one or two BLL tests for only infants or toddlers are insufficient for identifying children with Pb poisoning.