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Albeit slow and not without its challenges, lead (Pb) emissions and sources in the United States (U.S.) have decreased immensely over the past several decades. Despite the prevalence of childhood Pb poisoning throughout the twentieth century, most U.S. children born in the last two decades are significantly better off than their predecessors in regard to Pb exposure. However, this is not equal across demographic groups and challenges remain. Modern atmospheric emissions of Pb in the U.S. are nearly negligible since the banning of leaded gasoline in vehicles and regulatory controls on Pb smelting plants and refineries. This is evident in the rapid decrease of atmospheric Pb concentrations across the U.S. over the last four decades. One of the most significant remaining contributors to air Pb is aviation gasoline (avgas), which is minor compared to former Pb emissions. However, continual exposure risks to Pb exist in older homes and urban centers, where leaded paint and/or historically contaminated soils + dusts can still harm children. Thus, while effective in eliminating nearly all primary sources of Pb in the environment, the slow rate of U.S. Pb regulation has led to legacy sources of Pb in the environment. More proactive planning, communication, and research of commonly used emerging contaminants of concern that can persist in the environment long after their initial use (i.e., PFAS) should be prioritized so that the same mistakes are not made again. 

Abstract The evolution and expansion of land plants brought about one of the most dramatic shifts in the history of the Earth system — the birth of modern soils — and likely stimulated massive changes in marine biogeochemistry and climate. Multiple marine extinctions characterized by widespread anoxia, including the Late Devonian mass extinction around 372 million years ago, may have been linked to terrestrial release of the nutrient phosphorus driven by newly-rooted landscapes. Here we use recently published Devonian lake records as variable inputs in an Earth system model of the coupled carbon-nitrogen-phosphorus-oxygen-sulfur biogeochemical cycles to evaluate whether recorded changes to phosphorus fluxes could sustain Devonian marine anoxia sufficient to drive mass extinction. Results show that globally scaled increases in riverine phosphorus export during the Late Devonian mass extinction could have generated widespread marine anoxia, as modeled perturbations in carbon isotope, temperature, oxygen, and carbon dioxide data are generally consistent with the geologic record. Similar results for large scale volcanism suggest the Late Devonian mass extinction was likely multifaceted with both land plants and volcanism as contributing factors. 

Abstract Heavy metals are prevalent in urban settings due to many legacy and modern pollution sources, and are essential to quantify because of the adverse health effects associated with them. Of particular importance is lead (Pb), because there is no safe level of exposure, and it especially harms children. Through our partnership with community scientists in the Marion County (Indiana, United States) area (n= 162 households), we measured Pb and other heavy metal concentrations in soil, paint, and dust. Community scientists completed sampling with screening kits and samples were analyzed in the laboratory via x-ray fluorescence by researchers to quantify heavy metal concentrations, with Pb hazards reported back to participants. Results point to renters being significantly (p≤ 0.05) more likely to contain higher concentrations of Pb, zinc (Zn), and copper (Cu) in their soil versus homeowners, irrespective of soil sampling location at the home. Housing age was significantly negatively correlated with Pb and Zn in soil and Pb in dust across all homes. Analysis of paired soil, dust, and paint samples revealed several important relationships such as significant positive correlations between indoor vacuum dust Pb, dust wipe Pb, and outdoor soil Pb. Our collective results point to rental status being an important determinant of metal pollution exposure in Indianapolis, with housing age being reflective of both past and present Zn and Pb pollution at the household scale in dust and soil. Thus, future environmental pollution work examining renters versus homeowners, as well as other household data such as home condition and resident race/ethnicity, is imperative for better understanding environmental disparities surrounding not just Pb, but other heavy metals in environmental media as well. 

Heavy metal contamination in urban environments, particularly lead (Pb) pollution, is a health hazard both to humans and ecological systems. Despite wide recognition of urban metal pollution in many cities, there is still relatively limited research regarding heavy metal distribution and transport at the household-scale between soils and indoor dusts—the most important scale for actual human interaction and exposure. Thus, using community-scientist-generated samples in Indianapolis, IN (USA), we applied bulk chemistry, Pb isotopes, and scanning electron microscopy (SEM) to illustrate how detailed analytical techniques can aid in interpretation of Pb pollution distribution at the household-scale. Our techniques provide definitive evidence for Pb paint sourcing in some homes, while others may be polluted with Pb from past industrial/vehicular sources. SEM revealed anthropogenic particles suggestive of Pb paint and the widespread occurrence of Fe-rich metal anthropogenic spherules across all homes, indicative of pollutant transport processes. The variability of Pb pollution at the household scale evident in just four homes is a testament to the heterogeneity and complexity of urban pollution. Future urban pollution research efforts would do well to utilize these more detailed analytical methods on community-sourced samples to gain better insight into where the Pb came from and how it currently exists in the environment. However, these methods should be applied after large-scale pollution screening techniques such as portable X-ray fluorescence (XRF), with more detailed analytical techniques focused on areas where bulk chemistry alone cannot pinpoint dominant pollution mechanisms and where community scientists can also give important metadata to support geochemical interpretations. 

The evolution of land plant root systems occurred stepwise throughout the Devonian, with the first evidence of complex root systems appearing in the mid-Givetian. This biological innovation provided an enhanced pathway for the transfer of terrestrial phosphorus (P) to the marine system via weathering and erosion. This enhancement is consistent with paleosol records and has led to hypotheses about the causes of marine eutrophication and mass extinctions during the Devonian. To gain insight into the transport of P between terrestrial and marine domains, we report geochemical records from a survey of Middle and Late Devonian lacustrine and near-lacustrine sequences that span some of these key marine extinction intervals. Root innovation is hypothesized to have enhanced P delivery, and results from multiple Devonian sequences from Euramerica show evidence of a net loss of P from terrestrial sources coincident with the appearance of early progymnosperms. Evidence from multiple Middle to Late Devonian sites in Greenland and northern Scotland/Orkney reveal a near-identical net loss of P. Additionally, all sites are temporally proximal to one or more Devonian extinction events, including precise correlation with the Kačák extinction event and the two pulses associated with the Frasnian/Famennian mass extinction. For all sites, weathering, climate, and redox proxy data, coupled with nutrient input variability, reveal similar geochemical responses as seen in extant lacustrine systems. Orbitally forced climatic cyclicity appears to be the catalyst for all significant terrestrial nutrient pulses, which suggests that expansion of terrestrial plants may be tied to variations in regional and global climate. 

A substantial reduction in global transport and industrial processes stemming from the novel SARS-CoV-2 coronavirus and subsequent pandemic resulted in sharp declines in emissions, including for NO2. This has implications for human health, given the role that this gas plays in pulmonary disease and the findings that past exposure to air pollutants has been linked to the most adverse outcomes from COVID-19 disease, likely via various co-morbidities. To explore how much COVID-19 shutdown policies impacted urban air quality, we examined ground-based NO2 sensor data from 11 U.S. cities from a two-month window (March–April) during shutdown in 2020, controlling for natural seasonal variability by using average changes in NO2 over the previous five years for these cities. Levels of NO2 and VMT reduction in March and April compared to January 2020 ranged between 11–65% and 11–89%, consistent with a sharp drop in vehicular traffic from shutdown-related travel restrictions. To explore this link closely, we gathered detailed traffic count data in one city—Indianapolis, Indiana—and found a strong correlation (0.90) between traffic counts/classification and vehicle miles travelled, a moderate correlation (0.54) between NO2 and traffic related data, and an average reduction of 1.11 ppb of NO2 linked to vehicular data. This finding indicates that targeted reduction in pollutants like NO2 can be made by manipulating traffic patterns, thus potentially leading to more population-level health resilience in the future. 

Abstract Lead (Pb) is a neurotoxicant that particularly harms young children. Urban environments are often plagued with elevated Pb in soils and dusts, posing a health exposure risk from inhalation and ingestion of these contaminated media. Thus, a better understanding of where to prioritize risk screening and intervention is paramount from a public health perspective. We have synthesized a large national data set of Pb concentrations in household dusts from across the United States (U.S.), part of a community science initiative called “DustSafe.” Using these results, we have developed a straightforward logistic regression model that correctly predicts whether Pb is elevated (>80 ppm) or low (<80 ppm) in household dusts 75% of the time. Additionally, our model estimated 18% false negatives for elevated Pb, displaying that there was a low probability of elevated Pb in homes being misclassified. Our model uses only variables of approximate housing age and whether there is peeling paint in the interior of the home, illustrating how a simple and successful Pb predictive model can be generated if researchers ask the right screening questions. Scanning electron microscopy supports a common presence of Pb paint in several dust samples with elevated bulk Pb concentrations, which explains the predictive power of housing age and peeling paint in the model. This model was also implemented into an interactive mobile app that aims to increase community‐wide participation with Pb household screening. The app will hopefully provide greater awareness of Pb risks and a highly efficient way to begin mitigation.