Environmental Science & Technology Letters Environ.最新文献

The growing issue of electronic waste (E-waste), driven by the exponential growth in electronic device usage, presents significant environmental and economic challenges. E-waste production has surged, increasing by ∼2 million metric tonnes (Mt) annually, reaching 60 Mt in 2023, with projections suggesting it will exceed 70 Mt by 2030. Despite China, the United States, and India being the top E-waste producers, their recycling rates remain critically low at 16%, 15%, and 1%, respectively. E-waste contains valuable metals, such as gold (Au), silver (Ag), and copper (Cu), which comprise ∼60% of its composition. However, only 17.4% of the global E-waste was appropriately recycled in 2023. This Review discusses the latest data on E-waste, evaluates current metal recovery methods, and emphasizes the urgency of sustainable solutions to mitigate environmental hazards and promote a circular economy. The paper also covers case studies highlighting challenges and potential strategies for enhancing metal recovery efficiency, contributing significantly to global sustainability efforts and waste management.

Oxidative potential (OP) is increasingly recognized as a more health-relevant metric than particulate matter (PM) mass concentration because of its response to varying chemical compositions. Given the limited research on the OP of complex combustion aerosols, the effects of aging processes on their OP remain underexplored. We used online instruments to track the evolution of OP [via dithiothreitol (DTT) assays] during the aging of wood burning and coal combustion emissions by hydroxyl-radical-driven photooxidation and dark ozonolysis. We observed very substantial increases in the intrinsic OP (OP_m^DTT) of complex combustion aerosols (e.g., OP_m^DTT up to 100 pmol min^–1 μg^–1 for OH-aged wood burning emissions) within 1 day of equivalent aging. Further analysis in relation to the degree of oxidation revealed a potential for generalizing the OP of carbonaceous aerosols with average carbon oxidation state ${\overline{OS}}_c$ values ranging from −1.5 to −0.5 by assuming they have a constant OP_m^DTT value of ∼10 ± 6 pmol min^–1 μg^–1. Additionally, we uncovered a strong dependency of OP_m^DTT on both the source/precursor and aging pathway with ${\overline{OS}}_c$ above ∼−0.5. OH photooxidation was identified as an exceptionally efficient pathway for generating highly oxidized, multifunctionalized, and DTT-active products, particularly from wood burning emissions.

Oxidative potential (OP) is increasingly recognized as a more health-relevant metric than particulate matter (PM) mass concentration because of its response to varying chemical compositions. Given the limited research on the OP of complex combustion aerosols, the effects of aging processes on their OP remain underexplored. We used online instruments to track the evolution of OP [via dithiothreitol (DTT) assays] during the aging of wood burning and coal combustion emissions by hydroxyl-radical-driven photooxidation and dark ozonolysis. We observed very substantial increases in the intrinsic OP (OP_m ^DTT) of complex combustion aerosols (e.g., OP_m ^DTT up to 100 pmol min^-1 μg^-1 for OH-aged wood burning emissions) within 1 day of equivalent aging. Further analysis in relation to the degree of oxidation revealed a potential for generalizing the OP of carbonaceous aerosols with average carbon oxidation state values ranging from -1.5 to -0.5 by assuming they have a constant OP_m ^DTT value of ∼10 ± 6 pmol min^-1 μg^-1. Additionally, we uncovered a strong dependency of OP_m ^DTT on both the source/precursor and aging pathway with above ∼-0.5. OH photooxidation was identified as an exceptionally efficient pathway for generating highly oxidized, multifunctionalized, and DTT-active products, particularly from wood burning emissions.

Aminiums are significant components of organic aerosols with intense research on aliphatic aminiums. However, the mechanisms of formation of aromatic aminiums in urban aerosols remain elusive. Highly time-resolved PM_2.5 samples were collected in the center of Shanghai (China) during the winter to investigate the origin and formation of aminiums. The dominant aminium groups were aliphatic (mainly dimethylaminium and monomethylaminium). Anilinium was the third most abundant aminium. The concentrations of anilinium and total aminiums showed higher levels during the daytime and on weekdays. This finding combined with source apportionment analysis suggested that the daily and weekly scale variations of anthropogenic activities (e.g., traffic for commuting) were mainly responsible for the fluctuations in aminium concentrations (particularly aromatic aminiums). The acid dependence of aliphatic aminium formation was significantly stronger than that of aromatic aminium formation. Aliphatic and aromatic aminiums were significantly negatively and positively correlated with ozone, respectively, suggesting that the oxidative processes weakened the abundance of aliphatic aminiums but promoted the formation of aromatic aminiums. The molecular characterization of aromatic aminiums suggested that the atmospheric degradation of higher-molecular-weight aromatic amine compounds was an important mechanism for anilinium formation in urban aerosols. Thus, this study provides novel insights into the formation of aromatic aminiums.

Chlorophyll-a (Chl-a) is a commonly used proxy for algal biomass within surface waters, which can be indicative of harmful algal blooms. Excess nutrients, such as nitrogen or phosphorus, promote Chl-a production, often leading to eutrophication. However, little research exists on river nutrients-to-downstream lake Chl-a linkages at large watershed scales and across disparate climatic and physiographic regions. We found a significant positive relationship between measured total nitrogen (TN) and total phosphorus (TP) concentrations in upstream rivers and Chl-a concentrations in downstream lakes at the watershed scale (average area = 99.8 km² [35.8–628.6 km²], n = 254 watersheds) throughout the conterminous United States (CONUS). Additionally, through spatial logistic regression models, we demonstrate that a small number of explanatory variables (2–3 per model) can accurately predict (77%–86% accuracy, AUC = 0.83–0.91) classifications of high or low riverine TN, TP, or lake Chl-a concentrations throughout the CONUS at the watershed scale. The predictive variables included vegetation type, runoff, tile drainage, temperature, and nitrogen inputs. This work supports the hypothesis that rivers supply nutrients that enhance Chl-a concentrations in downstream lakes and demonstrates the power of parsimonious models combined with spatial autocorrelation to accurately predict classifications of nutrient concentrations and Chl-a across the CONUS.

Given the severe loss of species richness across diverse ecosystems, there is an urgent need to assess and monitor biodiversity on a global scale. The analysis of environmental DNA (eDNA), referring to any DNA extracted from environmental samples and subsequently sequenced, is a promising method for performing such biodiversity related studies. However, a comprehensive understanding of the factors that drive distinct eDNA degradation rates under different environmental conditions is currently missing, which limits the spatiotemporal interpretations that are possible from the eDNA-based detection of species. Here, we explore what role photochemistry may play in the fate of eDNA in aquatic ecosystems. Since few eDNA photodegradation studies have been performed, we extrapolate measured photochemical degradation dynamics from dissolved organic matter (DOM) and cellular DNA to what is expected for eDNA. Our findings show that photochemistry may dominate eDNA degradation under certain environmental conditions (e.g., DOM-rich waters with no light-limitation) and that photochemical alteration of eDNA may impact microbial respiration rates and the quantitative polymerase chain reaction (qPCR)-based detection of eDNA. We therefore encourage future studies to analyze the impact of photochemistry on eDNA degradation and provide suggested research directions that could help improve the accuracy of spatiotemporal inferences from eDNA analyses.

Given the severe loss of species richness across diverse ecosystems, there is an urgent need to assess and monitor biodiversity on a global scale. The analysis of environmental DNA (eDNA), referring to any DNA extracted from environmental samples and subsequently sequenced, is a promising method for performing such biodiversity related studies. However, a comprehensive understanding of the factors that drive distinct eDNA degradation rates under different environmental conditions is currently missing, which limits the spatiotemporal interpretations that are possible from the eDNA-based detection of species. Here, we explore what role photochemistry may play in the fate of eDNA in aquatic ecosystems. Since few eDNA photodegradation studies have been performed, we extrapolate measured photochemical degradation dynamics from dissolved organic matter (DOM) and cellular DNA to what is expected for eDNA. Our findings show that photochemistry may dominate eDNA degradation under certain environmental conditions (e.g., DOM-rich waters with no light-limitation) and that photochemical alteration of eDNA may impact microbial respiration rates and the quantitative polymerase chain reaction (qPCR)-based detection of eDNA. We therefore encourage future studies to analyze the impact of photochemistry on eDNA degradation and provide suggested research directions that could help improve the accuracy of spatiotemporal inferences from eDNA analyses.

Microplastic (MP) pollution has become a global issue, attracting attention from stakeholders around the globe. Knowledge of MPs has been substantially advanced in recent years. Newly developed analytical technologies allow better characterization of MPs, but characterizing nanosized plastic particles remains challenging. Transport of plastic debris from land to oceans is a key driver for marine plastic pollution, and the relative contributions from riverine runoff and atmospheric deposition must be further quantified. Another lingering issue is whether MPs can bioaccumulate and biomagnify along a food web, which demands further investigations. Currently there is no health risk assessment for human exposure to MPs, probably due to the lack of reference threshold values. Hence, establishing reference threshold values for MPs should be a long-term and continuing task for the scientific community. Recent progress in quantifying the vertical settling of plastic debris in deep oceans has brightened the prospect of finding the “Missing Plastics”, at least partially. Future efforts are urgently needed in developing novel analytical techniques, conducting additional laboratory and field measurements, and formulating robust models to better understand the occurrence, fate, and effects of MPs on the planet.