Environmental Science & Technology Letters Environ.最新文献

Nanocluster aerosols (NCAs, <3 nm particles) are associated with climate feedbacks and potentially with human health. Our recent study revealed NCA formation owing to the reaction of ozone with human surfaces. However, the underlying mechanisms driving NCA emissions remain unexplored. Squalene is the most abundant compound in human skin lipids that reacts with ozone, followed by unsaturated fatty acids. This study aims to examine the contribution of the squalene–ozone reaction to NCA formation and the influence of ozone and ammonia (NH₃) levels. In a climate-controlled chamber, we painted squalene and 6-hexadecenoic acid (C16:1n6) on glass plates to facilitate their reactions with ozone. The squalene–ozone reaction was further investigated at different ozone levels (15 and 90 ppb) and NH₃ levels (0 and 375 ppb). The results demonstrate that the ozonolysis of human skin lipid compounds contributes to NCA formation. With a typical squalene-C16:1n6 ratio found in human skin lipids (4:1), squalene generated 40 times more NCAs than did C16:1n6 and, thus, dominated NCA formation. More NCAs were generated with increased ozone levels, whereas increased NH₃ levels were associated with the stronger generation of larger NCAs but fewer of the smallest ones. This study experimentally confirms that NCAs are primarily formed from squalene–ozone reactions in ozone–human chemistry.

Semivolatile and intermediate volatility organic compounds (S/IVOCs) are known as crucial precursors of secondary organic aerosols (SOA), yet their specific contributions to SOA in urban areas remain unclear. Here, we investigate the real-time SOA formation from urban ambient air in summer in Beijing utilizing an oxidation flow reactor (OFR), coupled with aerosol and proton-transfer-reaction mass spectrometers. Our results show that the maximum photochemical formation of SOA in the OFR reached 2.9 μg m^–3 at ∼1.5 days of photochemical age. Primary OA and less oxidized oxygenated OA experience mass loss at high photochemical ages (>3 days) in the OFR, whereas more oxidized oxygenated OA continues to show mass enhancement, indicating the role of heterogeneous processes in the formation of highly aged SOA. Closure studies demonstrate that SOA estimated from the known precursors contribute 50.0 ± 17.3% of the measured SOA. The relatively low contribution (10.3 ± 5.2%) of IVOCs emphasizes the importance of unmeasured S/IVOCs in SOA formation. Furthermore, we illustrate the impact of heat waves on ambient SOA formation by enhancing photochemical oxidation and biogenic emissions in summer.

Sustainable water management is essential to increasing water availability and decreasing water pollution. The wastewater sector is expanding globally and beginning to incorporate technologies that recover nutrients from wastewater. Nutrient recovery increases energy consumption but may reduce the demand for nutrients from virgin sources. We estimate the increase in annual global energy consumption (1,100 million GJ) and greenhouse gas emissions (84 million t CO₂e) for wastewater treatment in the year 2030 compared to today’s levels to meet sustainable development goals. To capture these trends, integrated assessment and computable general equilibrium models that address the energy-water nexus must evolve. We reviewed 16 of these models to assess how well they capture wastewater treatment plant energy consumption and GHG emissions. Only three models include biogas production from the wastewater organic content. Four explicitly represent energy demand for wastewater treatment, and eight include explicit representation of wastewater treatment plant greenhouse gas emissions. Of those eight models, six models quantify methane emissions from treatment, five include representation of emissions of nitrous oxide, and two include representation of emissions of carbon dioxide. Our review concludes with proposals to improve these models to better capture the energy-water nexus associated with the evolving wastewater treatment sector.

Oxygenated volatile organic compounds (OVOCs) contribute to atmospheric secondary organic aerosols. To better constrain OVOC distributions, e.g., from the oxidation of phenolics, voltage scanning was applied for the targeted destruction of product nitrate (NO₃^–) clusters in a chemical ionization mass spectrometer. Herein, the voltage difference at which half of the clusters remain (dV₅₀) represents their bond strength. This study identified the type and relative bond strength of adducts for product distributions that can be observed for hours in our steady-state chamber (SAPHIR*). An unexpected increase was observed in voltage scanning curves of clusters containing nitrated phenols [e.g., C₇H₇NO₃(NO₃^–)], which was attributed to the declustering of double-analyte clusters [e.g., C₁₄H₁₄N₂O₆(NO₃^–)] at small voltage differences. Double-analyte clusters were distinguished from accretion product clusters [e.g., C₁₂H_(10,12)O_x(NO₃^–)] by their significantly lower intermolecular forces. Misidentifying C₁₄H₁₄N₂O₆ as accretion products could lead to an overestimation of its contribution to particle mass. In addition, the higher bonding strength in C₆H_(6,8)O_4–9(NO₃^–) compared to that in H₂SO₄(NO₃^–) indicates maximum sensitivities of C₆H_(6,8)O_4–9 at the collision limit. We could elucidate the relative acidity of the analytes to HNO₃. This study highlights additional dimensions gained from voltage scanning and suggests performing it to clarify the product distribution in complex urban air in the presence of nitrated phenols.

Studies of urban heat are often limited by their ability to measure air temperature; data are collected either at a few locations over time or at many locations at one point in time. Citizen science approaches to observing temperature provide a way to overcome these limitations, by capturing data over long time scales, at many locations. However, citizen scientists are more likely to be wealthier, making certain neighborhoods better observed than others. Because urban heat islands are more prevalent in poorer neighborhoods, heat extremes are less likely to be observed by citizen scientists. In spatial statistics, this is known as preferential sampling. When we adjust citizen science data for this effect, we obtain results that better agree with NOAA’s urban heat island data, which are not preferentially sampled. Using this adjustment, estimates of the July 2021 average evening temperature are almost 1 °C warmer in unobserved neighborhoods in Durham, North Carolina, than if they were not adjusted. We demonstrate that adjusted citizen science data allow for better characterization of heat risk at any time of interest and may be used for almost any neighborhood in the United States.

Atmospheric black carbon (BC) over coastal regions poses a threat in terms of both climate change and human health. However, the provenance of aerosol BC, particularly its subfractions (char-BC and soot-BC, which have different physicochemical properties), is poorly constrained. Here, we apportioned the sources of char-BC and soot-BC in year-round PM_2.5 samples from a coastal receptor island off southern China. Char-BC dominated, accounting for 88.6 ± 13.2% of the total BC. The two BC subfractions exhibited distinct seasonal variation patterns, which may be attributed to differences in their sources and hydrophilicity. Combustion of liquid fossil fuels, including bunker fuel, diesel, and gasoline, contributed more highly to soot-BC (71.4%) than to char-BC (53.9%). Conversely, combustion of solid fuels, including biomass and coal, contributed more highly to char-BC (44.6%) than to soot-BC (6.7%). Bunker fuel combustion, the dominant portion of ship emissions, was the largest contributor to total BC (46.0%), char-BC (45.2%), and soot-BC (56.4%). This indicates that marine ship emissions, rather than land-based sources including biomass and coal combustion, were the dominant source of atmospheric BC in coastal areas, highlighting the importance of controlling maritime ship emissions.

Urban stormwater runoff contains the tire-derived transformation product N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone), which poses significant environmental risks due to its high toxicity toward certain salmonids. 6PPD-quinone biotransformation has been investigated to explain some of the stark interspecies differences in sensitivity across different fishes; however, the primary mechanisms of 6PPD-quinone biotransformation remain unclear. This work aimed to explore the toxicokinetics of 6PPD-quinone in immortalized rainbow trout (Oncorhynchus mykiss) liver cells (RTL-W1) to identify transformation products, using coexposure with different enzyme inhibitors and inducers. Using high-resolution mass spectrometry, we identified three phase I 6PPD-quinone transformation products, with phenyl ring hydroxylation dominating, followed by hydroxylation of the alkyl side chain, and an unknown transformation product after 4 h of exposure. Co-exposing RTL-W1 cells with α-naphthoflavone and quercetin greatly inhibited the biotransformation of 6PPD-quinone, revealing that CYP1A is primarily involved in phase I biotransformation. Hepatic clearance predicted from in vitro results was further verified based on isolated perfused trout liver experiments. Further studies are necessary on the biotransformation and kinetics of 6PPD-quinone and the detoxification pathways involved in a wide phylogenetic space in fishes.

Increased wildfire activity increases the demands on fire rescue services and firefighters’ contact with harmful chemicals. This study aimed to determine firefighters’ exposure to toxic metal(loid)s and its association with the lipid profile. CELSPAC-FIREexpo study participants (including 110 firefighters) provided urine and blood samples to quantify urinary levels of metal(loid)s (arsenic, cadmium (Cd), mercury, and lead (Pb)), and serum lipid biomarkers (cholesterol (CHOL), low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), and triglycerides (TG)). The associations were investigated by using multiple linear regression and Bayesian weighted quantile sum (BWQS) regression. Higher levels of Pb were observed in firefighters. Pb was positively associated with CHOL and TG. Cd was negatively associated with HDL. In the BWQS model, the mixture of metal(loid)s was associated positively with CHOL (β = 14.75, 95% CrI = 2.45–29.08), LDL (β = 15.14, 95% CrI = 3.39–29.35), and TG (β = 14.79, 95% CrI = 0.73–30.42), while negatively with HDL (β = −14.96, 95% CrI = −25.78 to −1.8). Pb emerged as a key component in a metal(loid) mixture. The results suggest that higher exposure to lead and the mixture of metal(loid)s is associated with the alteration of the lipid profile, which can result in an unfavorable cardiometabolic profile, especially in occupationally exposed firefighters.