Tripling of western US particulate pollution from wildfires in a warming climate.

SignificanceRecord-setting fires in the western United States over the last decade caused severe air pollution, loss of human life, and property damage. Enhanced drought and increased biomass in a warmer climate may fuel larger and more frequent wildfires in the coming decades. Applying an empirical statistical model to fires projected by Earth System Models including climate-ecosystem-socioeconomic interactions, we show that fine particulate pollution over the US Pacific Northwest could double to triple during late summer to fall by the late 21st century under intermediate- and low-mitigation scenarios. The historic fires and resulting pollution extremes of 2017-2020 could occur every 3 to 5 y under 21st-century climate change, posing challenges for air quality management and threatening public health.

Drought Impacts on Secondary Organic Aerosol: A Case Study in the Southeast United States.

Secondary organic aerosol (SOA) is a significant component of fine particulate matter, and it has increased during past drought periods in the U.S. Here, we use the Community Multiscale Air Quality (CMAQ) model to characterize the complex effects of drought on SOA through a case study comparing a drought period (June 2011) and a wet period (June 2013) over the southeast U.S. The model simulates a 68% (1.7 µg/m3) higher SOA concentration at the surface during drought and attributes 98% of this increase to biogenic SOA. Through model sensitivity simulations, the SOA increase associated with drought is attributed to 54% from accelerated gas-phase reactions oxidizing volatile organic compounds (VOCs) to SOA, 45% from higher emissions of biogenic VOCs, 18% from enhanced acid-catalyzed production of isoprene SOA in aerosol water due to changing sulfate, 3% from enhanced in-cloud aqueous phase chemistry. Because the higher SOA levels overwhelm the reduced precipitation, there is an increase in wet deposition flux in the drought month which offsets 20% of the total SOA increase. If anthropogenic emissions are held constant, anthropogenic SOA is 51% higher during drought, highlighting the importance of meteorological impacts on chemistry.

Daily Estimation of Ground-Level PM2.5 Concentrations over Beijing Using 3 km Resolution MODIS AOD.

Estimating exposures to PM2.5 within urban areas requires surface PM2.5 concentrations at high temporal and spatial resolutions. We developed a mixed effects model to derive daily estimations of surface PM2.5 levels in Beijing, using the 3 km resolution satellite aerosol optical depth (AOD) calibrated daily by the newly available high-density surface measurements. The mixed effects model accounts for daily variations of AOD-PM2.5 relationships and shows good performance in model predictions (R(2) of 0.81-0.83) and cross-validations (R(2) of 0.75-0.79). Satellite derived population-weighted mean PM2.5 for Beijing was 51.2 µg/m(3) over the study period (Mar 2013 to Apr 2014), 46% higher than China's annual-mean PM2.5 standard of 35 µg/m(3). We estimated that more than 19.2 million people (98% of Beijing's population) are exposed to harmful level of long-term PM2.5 pollution. During 25% of the days with model data, the population-weighted mean PM2.5 exceeded China's daily PM2.5 standard of 75 µg/m(3). Predicted high-resolution daily PM2.5 maps are useful to identify pollution "hot spots" and estimate short- and long-term exposure. We further demonstrated that a good calibration of the satellite data requires a relatively large number of ground-level PM2.5 monitoring sites and more are still needed in Beijing.

A novel biosensing strategy on the dynamic and on-site detection of Vibrio coralliilyticus eDNA for coral health warnings.

Heat stress and coral diseases are the predominant factors causing the degradation of coral reef ecosystems. Over recent years, Vibrio coralliilyticus was identified as a temperature-dependent pathogen causing tissue lysis in Pocillopora damicornis and one of the primary pathogens causing bleaching and mortality in other corals. Yet current detection techniques for V. coralliilyticus rely primarily on qPCR and ddPCR, which cannot meet the requirements for non-invasive and real-time detection. Herein, we developed an effective electrochemical biosensor modified by an Au-MoS2/rGO (AMG) nanocomposites and a specific capture probe to dynamically detect V. coralliilyticus environment DNA (eDNA) in aquarium experiments, with a lower limit of detection (0.28 fM) for synthetic DNA and a lower limit of quantification (9.8 fg/µL, ∼0.86 copies/µL) for genomic DNA. Its reliability and accuracy were verified by comparison with the ddPCR method (P > 0.05). Notably, coral tissue started to lyse at only 29 °C when the concentration of V. coralliilyticus increased abruptly to 880 copies/µL, indicating the biosensor could reflect the types of pathogen and health risks of corals under heat stress. Overall, the novel and reliable electrochemical biosensing technology provides an efficient strategy for the on-site monitoring and early warning of coral health in the context of global warming.

Application of Graphene-Combined Rare-Earth Oxide (Sm2O3) in Solar-Blind Ultraviolet Photodetection.

Rare-earth oxide Sm2O3 is theoretically expected to be used in the preparation of ultraviolet (UV) detectors with low dark currents and high radiation resistance due to its characteristics of a wide bandgap, a high dielectric constant, and high chemical stability. However, certain features that rare-earth oxides possess, such as high resistivity and weak photoelectric response currents, have hindered relevant research on these kinds of materials in the field of UV detection. In this work, a p-Gr/i-Sm2O3/n-SiC heterojunction photovoltaic solar-blind UV sensor was constructed for the first time. Because of the high mobility of graphene (Gr) and the contribution of double built-in electric fields in the heterojunction, the collection efficiency of photogenerated carriers has been greatly improved, with the typical shortcomings of high resistivity and poor photoelectric response performance of rare-earth oxides having been overcome. This detector has exhibited outstanding performance at 0 V, including a responsivity of 19.8 mA/W and an open-circuit voltage of 0.68 V. Additionally, this detector has a detectivity as high as 1.2 × 1011 jones, which is at the front position of most ultraviolet detectors. The fabrication of this high-performance Sm2O3-based photovoltaic UV detector has broadened the application fields of rare-earth oxide semiconductors. Therefore, this project has important value for future research in relevant fields.

General synthesis strategy of ZrO2 nanofilms with few-atom layered thickness for boosting triethylamine detection.

ZrO2, a traditional inert transition metal oxide (TMO), can be prepared into ZrO2 nanofilms (NFs) with a single-layer thickness of only 2.5 nm through the generally applicable two-dimensional TMO synthesis strategy reported by us, and has displayed remarkable sensitivity and selectivity properties for triethylamine gas detection.

Mapping daily PM2.5 at 500 m resolution over Beijing with improved hazy day performance.

The application of satellite-derived aerosol optical depth (AOD) to infer surface PM2.5 has significantly increased the spatial coverage and resolutions (1-10 km) of ground-level PM2.5 mapping as required for accurate exposure estimation. The remaining challenge is to further increase the mapping resolution to the sub-km level with improved algorithms to minimize misrepresentation of severe haze as clouds. In this study, we provide the first daily PM2.5 estimation over Beijing at a 500 m resolution using AOD from the Simplified Aerosol Retrieval Algorithm (SARA) and linear mixed effects model. A novel cloud screen method is developed which significantly improves data availability during hazy days. The cross-validation R2 for PM2.5 estimations is 0.82 with the cloud-screened SARA AOD. Based on the satellite-predicted high-resolution PM2.5 map, all-day population-weighted PM2.5 is estimated to be 81.4 µg m-3 over Beijing (2.3 times higher than China's NAAQS of 35 µg m-3). Compared to the standard MODIS Dark Target 3 km product which presents a significant percentage of missing data, the 500 m resolution PM2.5 mapping derived from SARA AOD reveals distinct pollution patterns and population exposure conditions during severe hazy days, thereby providing valuable information for pollution control and epidemiological studies.

Publisher Correction: Causes of model dry and warm bias over central U.S. and impact on climate projections.

The original version of this Article contained an error in Figure 2. In panel a, the x axis of the graph was incorrectly labeled 'precipitation bias', and should have read 'negative precipitation bias'. This error has been corrected in both the PDF and HTML versions of the Article.

Publisher Correction: Regional disparities in warm season rainfall changes over arid eastern-central Asia.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Regional disparities in warm season rainfall changes over arid eastern-central Asia.

Multiple studies have reported a shift in the trend of warm season rainfall over arid eastern-central Asia (AECA) around the turn of the new century, from increasing over the second half of the twentieth century to decreasing during the early years of the twenty-first. Here, a closer look based on multiple precipitation datasets reveals important regional disparities in these changes. Warm-season rainfall increased over both basin areas and mountain ranges during 1961-1998 due to enhanced moisture flux convergence associated with changes in the large-scale circulation and increases in atmospheric moisture content. Despite a significant decrease in warm-season precipitation over the high mountain ranges after the year 1998, warm season rainfall has remained large over low-lying basin areas. This discrepancy, which is also reflected in changes in river flow, soil moisture, and vegetation, primarily results from disparate responses to enhanced warming in the mountain and basin areas of AECA. In addition to changes in the prevailing circulation and moisture transport patterns, the decrease in precipitation over the mountains has occurred mainly because increases in local water vapor saturation capacity (which scales with temperature) have outpaced the available moisture supply, reducing relative humidity and suppressing precipitation. By contrast, rainfall over basin areas has been maintained by accelerated moisture recycling driven by rapid glacier retreat, snow melt, and irrigation expansion. This trend is unsustainable and is likely to reverse as these cryospheric buffers disappear, with potentially catastrophic implications for local agriculture and ecology.

Causes of model dry and warm bias over central U.S. and impact on climate projections.

Climate models show a conspicuous summer warm and dry bias over the central United States. Using results from 19 climate models in the Coupled Model Intercomparison Project Phase 5 (CMIP5), we report a persistent dependence of warm bias on dry bias with the precipitation deficit leading the warm bias over this region. The precipitation deficit is associated with the widespread failure of models in capturing strong rainfall events in summer over the central U.S. A robust linear relationship between the projected warming and the present-day warm bias enables us to empirically correct future temperature projections. By the end of the 21st century under the RCP8.5 scenario, the corrections substantially narrow the intermodel spread of the projections and reduce the projected temperature by 2.5 K, resulting mainly from the removal of the warm bias. Instead of a sharp decrease, after this correction the projected precipitation is nearly neutral for all scenarios.Climate models repeatedly show a warm and dry bias over the central United States, but the origin of this bias remains unclear. Here the authors associate this bias to precipitation deficits in models and after applying a correction, projected precipitation in this region shows no significant changes.

Summer rainfall over the southwestern Tibetan Plateau controlled by deep convection over the Indian subcontinent.

Despite the importance of precipitation and moisture transport over the Tibetan Plateau for glacier mass balance, river runoff and local ecology, changes in these quantities remain highly uncertain and poorly understood. Here we use observational data and model simulations to explore the close relationship between summer rainfall variability over the southwestern Tibetan Plateau (SWTP) and that over central-eastern India (CEI), which exists despite the separation of these two regions by the Himalayas. We show that this relationship is maintained primarily by 'up-and-over' moisture transport, in which hydrometeors and moisture are lifted by convective storms over CEI and the Himalayan foothills and then swept over the SWTP by the mid-tropospheric circulation, rather than by upslope flow over the Himalayas. Sensitivity simulations confirm the importance of up-and-over transport at event scales, and an objective storm classification indicates that this pathway accounts for approximately half of total summer rainfall over the SWTP.

Occurrence and fate of PPCPs and correlations with water quality parameters in urban riverine waters of the Pearl River Delta, South China.

The occurrence and fate of eight PPCPs was studied in river waters from upstream to downstream of the three rivers in the Pearl River Delta, China. The correlations of PPCP levels and water quality parameters were also investigated. The analytes of the highest concentrations were caffeine, acetaminophen, and ciprofloxacin. Carbamazepine and erythromycin-H2O were detected at the lowest concentrations. The highest concentrations of PPCPs were found in the Shijing River, with 865 ng/L caffeine, 339 ng/L acetaminophen, and 304 ng/L ciprofloxacin. In general, the levels of PPCPs in the Zhujiang River were higher at sites where the metropolitan city Guangzhou is located and decreased from the epicenter along the river. Low levels of PPCPs were generally found in the Beijiang River. Positive correlations were found between PPCP levels, total nitrogen, ammonium nitrogen, and cumulative fluorescence excitation-emission matrix (EEM) volume. Among the four PPCPs evaluated (caffeine, acetaminophen, ciprofloxacin, and sulfamethoxazole), caffeine had the best correlations with the correlation coefficients ranging from 0.62 to 0.98. The prediction of PPCP concentrations at specified locations can be substantially simplified.