Tropospheric ozone (O3) was first determined to be phytotoxic to grapes in southern California in the 1950s. Investigations followed that showed O3 to be the cause of foliar symptoms on tobacco and eastern white pine. In the 1960s, “X” disease of ponderosa pines within the San Bernardino Mountains was likewise determined to be due to O3. Nearly 50 years of research have followed. Foliar O3 symptoms have been verified under controlled chamber conditions. Studies have demonstrated negative growth effects on forest tree seedlings due to season-long O3 exposures, but due to complex interactions within forest stands, evidence of similar losses within mature tree canopies remains elusive. Investigations on tree growth, O3 flux, and stand productivity are being conducted along natural O3 gradients and in open-air exposure systems to better understand O3 effects on forest ecosystems. Given projected trends in demographics, economic output and climate, O3 impacts on US forests will continue and are likely to increase. Elevated tropospheric ozone remains an important phytotoxic air pollutant over large areas of US forests.

European research efforts to address concerns in relation to increasing levels of marine litter and potential effects on ecosystems and human health have been launched. We assessed a total of 52 European projects which researched or contributed to the implementation of European marine litter legislation. These projects ranged from national initiatives, to large scale programmes involving multiple EU member states. The best represented topics within those European projects were ‘Policy, Governance and Management’ and ‘Monitoring’. Comparatively ‘Risk Assessment’, ‘Fragmentation’ and ‘Assessment Tools’ were underrepresented. The analyses showed that West-European countries have contributed more to marine litter research and therefore received more funding. As a result, thematic hotspots were present, and scientific capacity is concentrated by topic and countries. The results indicate the need to continue to support initiatives to cover clearly identified gaps, either geographic or thematic, to deliver risk assessments and recommendations to address the marine litter issue.

This paper reports the temporal variations, sources and transport characteristics of carbonaceous aerosol in Chongqing, a megacity in the Sichuan Basin. Hourly organic carbon (OC) and elemental carbon (EC) mass concentrations in PM₂.₅ were measured at an urban supersite from November 2019 to October 2020. The annual mean PM₂.₅, OC and EC concentrations (±1SD) were 38.50 ± 25.79 μg/m³, 9.03 ± 5.73 and 2.45 ± 1.47 μgC/m³, respectively. An intensive influence of biomass combustion was found during the observation period. Strong seasonality of carbonaceous aerosol with highest concentrations in winter and lowest concentrations in summer was observed. Meanwhile, two diverse pathways for secondary formation dominated in different seasons. One was highly related to gas-phase photochemical oxidation under high temperature and radiation, and another was highly related to heterogeneous reactions, while the latter was more significant, especially in winter. Diurnal and quarterly variation patterns for carbonaceous aerosol showed that the development of planetary boundary layer strongly influenced carbonaceous aerosol concentrations. Moreover, the regional sources from the northeast within the basin were identified as major contributors of the primary carbonaceous aerosol to Chongqing, while secondary components were more from local sources than regional transport. This study highlights the importance of prioritising the abatement of gaseous precursors for carbonaceous aerosol and an urgent need for the inter-regional prevention and control measures of the cities located in the Sichuan basin, especially the cities in the northeast of urban Chongqing.

This study evaluates the carcinogenic and the non-carcinogenic health risks related to non-methane volatile organic compounds (NMVOCs) and elements, dioxins, furans, dioxin-like polychlorobiphenyls, phthalates and polycyclic aromatic hydrocarbons in PM₂.₅ samples collected during a one-year field campaign in two urban industrial areas in the East Mediterranean region. The health risk was assessed for the three exposure pathways (ingestion, inhalation and dermal contact) and for different age categories (newborns, children, adolescents, and adults). The non-carcinogenic risk calculated for the different species showed that benzene and n-heptane explained 78–94% of the total hazard index (HI) for NMVOCs at both sites. The total HI for NMVOCs varied between 2.9 and 26.8 at Zouk and between 0.8 and 6.6 at Fiaa for adults and newborns respectively exceeding the recommended USEPA limit of 1 for most age categories. PM₂.₅-bound elements had values higher than the recommended USEPA limit for newborns with Mn, Pb, V, and Ni as the major contributors. The other species under study presented moderate risk values. The lifetime cancer risk due only to the exposure to NMVOCs was 170 and 46 times higher than the threshold limit at Zouk and Fiaa, respectively. PM₂.₅-bound PAHs, As, Co, Cr(VI), Ni and V concentrations showed lifetime cancer risk exceeding the threshold limit of 10⁻⁶ with 58 and 28 additional cancer cases per million habitats at Zouk and Fiaa, respectively. To our knowledge, this assessment is a first evaluating the health risk of several classes of compounds from both particulate and gas phases.

Pollution derived from car tires is of growing research interest due to its apparent omnipresence in the urban environment and its associated toxicity. Studies have focused largely on the occurrence of these tire materials, deemed tire wear particles (TWPs), and their associated chemicals in the aquatic environment. However, less attention has been paid to atmospheric TWPs, which can remain airborne and be transported over long distances. In addition, there are few studies pertaining to the gaseous contaminants originating from tire wear, creating a significant knowledge gap. This review aims to summarize the current state of knowledge surrounding atmospheric tire wear pollution by detailing relevant studies conducted under both laboratory and ambient environmental conditions. Organic chemicals that are associated with this form of pollution, including diphenylamine antioxidants, phthalates, benzothiazole, benzotriazoles, and alkylphenols were highlighted for their potential implications for air. While a number of studies have investigated oxidation in aquatic environments, the current review highlights a clear absence of oxidation product information relevant to air. There is also a critical research gap surrounding the physico-chemical properties of these potential atmospheric pollutants. As a result, the environmental behaviour and fate of these contaminants are largely unknown. Based on these knowledge gaps, we propse recommendations for future work to advance this area of research.

In some international cities, winter air pollution can manifest into a local-scale brown air pollution haze which has been associated with negative health outcomes. Land-sea breezes are known to impact urban air quality through the recirculation of air pollution and the formation of internal boundary layers (IBLs). However, research into land-sea breezes has primarily focused on summer air pollution and little is known about the influence of land-sea breezes on local-scale winter brown haze. Using continuous data (including surface meteorology, surface air quality, satellite-derived sea surface temperatures, and ceilometer-derived boundary-layer depths) observed over seven winters from 2013 to 2019, we present a novel investigation of the influence of land-sea breezes on brown haze in Auckland, New Zealand. Severe brown haze days are significantly more likely to coincide with a land-sea breeze circulation simultaneously occurring at both the east and west coasts when compared with days on which brown haze is expected but not observed (based on favourable meteorology and high surface air pollution levels). Both severe brown haze and high surface level PM₂.₅ concentrations (previously associated with the presence of brown haze) are found to be associated with a high degree of horizontal recirculation at Auckland's east coast. No relationship is found between the occurrence of sea-breeze-induced IBLs and the formation of brown haze. The results presented in this study offer insights into the physical mechanisms that influence the formation and persistence of local-scale winter brown haze in a complex coastal setting with correspondingly complex land-sea breezes.

Cities located on Eastern Mediterranean is exposed to both local and distant anthropogenic and natural sources. In this study, to determine the effect of these sources on Particulate Matter (PM) concentrations in a coastal city, particulate matter with diameters less than 2.5 μm (PM2.5) and with diameters between 2.5 and 10 μm (PM2.5−10) were collected once in a two-day period for 24 h between July 2014 and July 2015 in downtown Antalya which is located on the Mediterranean coast of Turkey. Antalya is one of the fast growing city of Turkey with a population of 2.3 million. Samples were analyzed using an energy-dispersive X-ray fluorescence for 15 elements (Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Cu, Zn, As, Pb). Statistical parameters were calculated for all measured elements in fine (PM2.5) and coarse (PM2.5−10) fraction. Crustal and marine elements, such as Ti, Ca, Al and Na were abundant in the course fraction. Only S was found in higher concentration in the fine fraction. Monthly variation of Crustal Enrichment Factor (EFC) results of Si showed that the area was under influence of non-local crustal dust especially during spring and late summer. EFC also indicated that during winter season, fine fraction K was due to local wood combustion. Source regions of S was determined using Potential Source Contribution Function (PSCF) and compared with previous studies conducted at a rural site of Antalya approximately twenty years ago. Most of the source regions affecting S concentrations at the Eastern Mediterranean region were found out to be same: western Anatolia, Marmara region, the Aegean Sea coasts of Greece and some parts of Bulgaria and Romania. However, due to decrease in SO2 emissions over the northeast coast of Black Sea and between Caspian Sea and Ukraine, the region was not turned up to be a source region.

The inappropriate combustion of furniture-industry waste can be a source of serious environmental problems. We proposed a method which is capable to distinguish the emission resulting from the combustion of wood-based materials, the essential component of such waste. The originality of the approach consists in the classification of gas mixtures instead of focussing on the individual pollutants emitted to the atmosphere. The classification of emission was based on the measurements applying differential ion mobility spectrometry (DMS) and Fourier transform infrared (FTIR) spectrometry, for comparison. There were successfully distinguished emissions associated with combustion of wood-based materials: OSB board, MDF board and plywood (≥95% correct classifications in the class (ccc)) and wood: pellet and kindling wood (≥92% ccc). Results of classification based on DMS and FTIR measurements were similar. Emissions from the combustion of individual materials were best distinguished using DMS (100% ccc), as compared with FTIR, which offered lower performance, mostly >90% ccc. Regarding pairwise classification, the most distinctive were emissions from the combustion of plywood (DMS: 99% ccc; FTIR: 99% ccc), MDF board (DMS: 99% ccc; FTIR: 99% ccc) and OSB board (DMS: 99% ccc; FTIR: 98% ccc). Emissions form kindling wood (DMS: 100% ccc; FTIR: 95% ccc) and pellet (DMS: 97% ccc; FTIR: 98% ccc) caused a bit more confusion. In most cases, results of classification based on DMS and FTIR measurements were comparable. The success of classification based on DMS measurements proved that it is possible to detect the harmful emission without determining the chemical composition of the flue gas. This solution represents a new approach to air quality monitoring, which recently attracts increasing attention.

This paper presents model results for the dispersion of radionuclides released into the atmosphere by intense forest fires in the Chernobyl Exclusion Zone in April 2020. The ¹³⁷Cs activity concentration in the surface air is calculated on a regional scale (in Ukraine) and a local scale (within the Chernobyl Exclusion Zone). The ¹³⁷Cs activity in the surface air of Kyiv was found to have reached 2–4 mBq m⁻³ during the period April 4–20. The results presented in this paper are generally consistent with measured data pertaining to radioactive contamination in Kyiv and areas around several nuclear power plants in Ukraine. The total effective dose to the population of Kyiv during the fire period was estimated to be 5.7 nSv from external exposure and the inhalation of ¹³⁷Cs and ⁹⁰Sr, rising to 30 nSv by the end of 2020. This is about 0.003% of the annual permissible level of exposure of the population. A committed effective dose of about 16 nSv was estimated for the personnel of the Chernobyl nuclear power plant from the inhalation of ¹³⁷Cs and ⁹⁰Sr during the 2020 forest fires. A method for estimating the radionuclide activity emissions during wildland fires in radioactively contaminated areas is proposed. This method is based on satellite measurement data of the fire radiative power, the radionuclide inventory in the fire area, and an emission factor for radioactive particles.

Accuracy prediction of air quality is of crucial importance for people to take precautions and improve environmental conditions. By introducing adjacency matrix in Long Short-Term Memory (LSTM) cell, we propose in this research a Graph-based Long Short-Term Memory (GLSTM) model to predict PM2.5 concentration in Gansu Province of Northwest China. We regard all air quality monitoring stations as a graph, and construct a parameterized adjacency matrix on the basis of the adjacency matrix of the graph. Through the combination of parameterized adjacency matrix and LSTM, we introduce spatiotemporal information to achieve PM2.5 prediction. The advantage of GLSTM is that it can realize synchronous operation of all stations, making it unnecessary to train different model for each monitoring station to obtain the overall PM2.5 variation of a certain area. The parameterized adjacency matrix also enhances the interpretability of the model. By visualizing the parameterized adjacency matrix obtained from the end-to-end PM2.5 prediction task in training, the importance of introducing spatial information, i.e. the distribution importance of surrounding stations to a specific station is clearly demonstrated. We compared our model with several newly reported methods, and found that it achieved the best results on PM2.5 prediction tasks at almost all stations, which proved the effectiveness of the GLSTM model.