High-resolution modeling of the distribution of surface air pollutants and their intercontinental transport by a global tropospheric atmospheric chemistry source–receptor model (GNAQPMS-SM)

Many efforts have been devoted to quantifying the impact of intercontinental transport on global air quality by using global chemical transport models with horizontal resolutions of hundreds of kilometers in recent decades. In this study, a global online air quality source–receptor model (GNAQPMS-SM) is designed to effectively compute the contributions of various regions to ambient pollutant concentrations. The newly developed model is able to quantify source–receptor (S-R) relationships in one simulation without introducing errors by nonlinear chemistry. We calculate the surface and planetary boundary layer (PBL) S-R relationships in 19 regions over the whole globe for ozone (O3), black carbon (BC), and non-sea-salt sulfate (nss-sulfate) by conducting a high-resolution (0.5&deg &times 0.5&deg) simulation for the year 2018. The model exhibits a realistic capacity in reproducing the spatial distributions and seasonal variations of tropospheric O3, carbon monoxide, and aerosols at global and regional scales – Europe (EUR), North America (NAM), and East Asia (EA). The correlation coefficient (R) and normalized mean bias (NMB) for seasonal O3 at global background and urban–rural sites ranged from 0.49 to 0.87 and −2 % to 14.97 %, respectively. For aerosols, the R and NMB in EUR, NAM, and EA mostly exceed 0.6 and are within ±15 %. These statistical parameters based on this global simulation can match those of regional models in key regions. The simulated tropospheric nitrogen dioxide and aerosol optical depths are generally in agreement with satellite observations. The model overestimates ozone concentrations in the upper troposphere and stratosphere in the tropics, midlatitude, and polar regions of the Southern Hemisphere due to the use of a simplified stratospheric ozone scheme and/or biases in estimated stratosphere–troposphere exchange dynamics. We find that surface O3 can travel a long distance and contributes a non-negligible fraction to downwind regions. Non-local source transport explains approximately 35 %–60 % of surface O3 in EA, South Asia (SAS), EUR, and NAM. The O3 exported from EUR can also be transported across the Arctic Ocean to the North Pacific and contributes nearly 5 %–7.5 % to the North Pacific. BC is directly linked to local emissions, and each BC source region mainly contributes to itself and surrounding regions. For nss-sulfate, contributions of long-range transport account for 15 %–30 % within the PBL in EA, SAS, EUR, and NAM. Our estimated international transport of BC and nss-sulfate is lower than that from the Hemispheric Transport of Air Pollution (HTAP) assessment report in 2010, but most surface O3 results are within the range. This difference may be related to the different simulation years, emission inventories, vertical and horizontal resolutions, and S-R revealing methods. Additional emission sensitivity simulation shows a negative O3 response in receptor region EA in January from EA. The difference between two methods in estimated S-R relationships of nss-sulfate and O3 are mainly due to ignoring the nonlinearity of pollutants during chemical processes. The S-R relationship of aerosols within EA subcontinent is also assessed. The model that we developed creates a link between the scientific community and policymakers. Finally, the results are discussed in the context of future model development and analysis opportunities.

High-resolution modeling the distribution of surface air pollutants and their intercontinental transport by a global tropospheric atmospheric chemistry source-receptor model (GNAQPMS-SM)

Many efforts have been devoted to quantifying the impact of intercontinental transport on global air quality by using global chemical transport models with horizontal resolutions of hundreds of kilometers in recent decades. In this study, a global online air quality source-receptor model (GNAQPMS-SM) is designed to effectively compute the contributions of various regions to ambient pollutant concentrations. The newly developed model is able to quantify source-receptor (S-R) relationships in one simulation without introducing errors by nonlinear chemistry, which largely reduces the computation costs compared to the brute force method. We calculate the surface and planetary boundary layer (PBL) S-R relationships in 19 regions over the whole globe for ozone, black carbon (BC) and non-sea-salt sulphate (nss-sulphate) by conducting a high-resolution (0.5° × 0.5°) simulation for the year 2018. The model exhibits a realistic capacity in reproducing the spatial distributions and seasonal variations of tropospheric ozone, carbon monoxide, and aerosols at global and regional scales (Europe, North America and East Asia). The correlation coefficient (R) and normalized mean bias (NMB) for seasonal ozone at global background and urban-rural sites ranged from 0.49 to 0.87 and −2 % to 14.97 %, respectively. For aerosols, the R and NMB in Europe, North America and East Asia mostly exceed 0.6 and are within ±15 %. These statistical parameters based on this global simulation can match those of regional models in key regions. The simulated tropospheric nitrogen dioxide and aerosol optical depths are generally in agreement with satellite observations. The model overestimates ozone mixing ratios in the upper troposphere and stratosphere in the tropics, mid-latitude and polar regions of the Southern Hemisphere due to the use of a simplified stratospheric ozone scheme and/or biases in estimated stratosphere-troposphere exchange dynamics. We find that O3 in the surface layer can travel a long distance and contributes a nonnegligible fraction to downwind regions. Nonlocal source transport explains approximately 35–60 % of surface O3 in East Asia, South Asia, Europe and North America. The O3 exported from Europe can also be transported across the Arctic Ocean to the North Pacific and contributes nearly 5–7.5 % to the North Pacific. BC, as a primary aerosol, is directly linked to local emissions, and each BC source region mainly contributes to itself and surrounding regions. For nss-sulphate, contributions of long-range transport account for 15–30 % within the PBL in East Asia, South Asia, Europe and North America. Our estimated international transport is lower than that from the Hemispheric Transport of Air Pollution (HTAP) assessment report in 2010. In this study, local contributions to surface nss-sulphate and BC exceed the ranges given in the HTAP model, while local contributions to nss-sulphate and BC within the PBL are mainly within the ranges. This difference may be related to the different simulation years, emission inventories, horizontal resolutions and S-R revealing methods. The S-R relationship of aerosols within the East Asia subcontinent is also assessed. The model that we developed creates a link between the scientific community and policymakers. Finally, the results are discussed in the context of future model development and analysis opportunities.

Invasive mosquito species (Diptera: Culicidae) in Serbia

Invasive mosquito species surveillance has been carried out in Europe since late 1990s, and the results revealed that their distribution range and population density have been increasing every year (ECDC, 2020). Majority of European countries are affected by at least one of invasive mosquito species, which are considered as important vector species of public health concern. Aedes invasive species are very aggressive daily biters and highly competitive with native mosquito species coexisting in the same breeding sites. Although pathogens transmitted by mosquitoes are much bigger problem in tropical areas, imported and autothonous cases of these diseases have been recorded every year in Europe. International and intercontinental transport of humans and goods increase the likely-hood of outbreaks caused by vector-borne pathogens. Cases of imported invasive mosquito species and cases of imported human infection (with Dengue and Chikungunya virus, imported and autohtonous) are increasing every year. Together with the presence of invasive mosquito species, outbreaks caused by vector-borne pathogens are significantly driven by human behaviour, ecosystem and climat changes. Two invasive mosquito species were present in Serbia so far: Aedes albopictus (Asian tiger mosquito) and Aedes japonicus (Japaneese bush mosquito). Populations of Ae. albopicus has been succesfully spreading in many urban and suburban areas in our country, while Ae. japonicus was identified in only two localities up today. According to the experience from Croatia, where this mosquito species is widely spread, similar scenario could be expected in Serbia as well.

Attribution of ground-level ozone to anthropogenic and natural sources of nitrogen oxides and reactive carbon in a global chemical transport model

We perform a source attribution for tropospheric and ground-level ozone using a novel technique that accounts separately for the contributions of the two chemically distinct emitted precursors (reactive carbon and oxides of nitrogen) to the chemical production of ozone in the troposphere. By tagging anthropogenic emissions of these precursors according to the geographical region from which they are emitted, we determine source–receptor relationships for ground-level ozone. Our methodology reproduces earlier results obtained via other techniques for ozone source attribution, and it also delivers additional information about the modelled processes responsible for the intercontinental transport of ozone, which is especially strong during the spring months. The current generation of chemical transport models used to support international negotiations aimed at reducing the intercontinental transport of ozone shows especially strong inter-model differences in simulated springtime ozone. Current models also simulate a large range of different responses of surface ozone to methane, which is one of the major precursors of ground-level ozone. Using our novel source attribution technique, we show that emissions of NOx (oxides of nitrogen) from international shipping over the high seas play a disproportionately strong role in our model system regarding the hemispheric-scale response of surface ozone to changes in methane, as well as to the springtime maximum in intercontinental transport of ozone and its precursors. We recommend a renewed focus on the improvement of the representation of the chemistry of ship NOx emissions in current-generation models. We demonstrate the utility of ozone source attribution as a powerful model diagnostic tool and recommend that similar source attribution techniques become a standard part of future model intercomparison studies.

The Effect on Air Quality of Lockdown Directives to Prevent the Spread of SARS-CoV-2 Pandemic in Campania Region—Italy: Indications for a Sustainable Development

Data on air quality collected by the regional network of fixed stations in the most urbanized areas of the Campania region in the south of Italy are examined. Two periods are considered: before and during the adoption of the main directives limiting human activities to fight the spread of SARS-CoV-2 infection. The first period is from the 5th of February to the 5th of March, and the second is from the 13th of March to the 13th of April. Meteorological conditions in the two periods were compared and significant differences were not observed. Therefore, the comparison of air quality data is feasible. During the second period, an intercontinental transport of particulate matter occurred. Data collected during this event (4 p.m. on the 30th of March to 4 p.m. on the 31st of March) were excluded from the analysis. The main reduction of pollutant concentration is observed for NO2 (−48% of the period average). PM10 shows a lower reduction (−17%). The PM2.5 average period concentration was quite constant, while the 98° percentile was reduced by −21%. Ozone shows, on the contrary, an increase in concentration due mainly to an increase in solar irradiation during the 2nd period, but also due to the decrease of NOx concentration. The reduction or the increase of pollutant concentration depends on the category of the station: background, industrial, residential, and traffic. In addition to air quality, the reduction of anthropogenic emissions is also studied. All the information available on the reduction of emissions from transport, industry, heating, and other main emissive sectors were collected. The results give useful insights for the development of air quality management policies that could be adopted when the sanitary emergency will end to guarantee the sustainable development of the Campania region.

Attribution of ground-level ozone to anthropogenic and natural sources of NO_x and reactive carbon in a global chemical transport model

We perform a source attribution for tropospheric and ground-level ozone using a novel technique which accounts separately for the contributions of the two chemically distinct emitted precursors (reactive carbon and oxides of nitrogen) to the chemical production of ozone in the troposphere. By tagging anthropogenic emissions of these precursors according to the geographical region from which they are emitted, we determine source/receptor relationships for ground-level ozone. Our methodology reproduces earlier results obtained through other techniques for ozone source attribution, and also delivers additional information about the modelled processes responsible for intercontinental transport of ozone, which is especially strong during the spring months. The current generation of chemical transport models used to support international negotiations aimed at reducing the intercontinental transport of ozone show especially strong inter-model differences in simulated springtime ozone. Current models also simulate a large range of different responses of surface ozone to methane, one of the major precursors of ground-level ozone. Using our novel source attribution technique, we show that emissions of NOx from international shipping over the high seas play a disproportionately strong role in our model system to the hemispheric-scale response of surface ozone to changes in methane, as well as to the springtime maximum in intercontinental transport of ozone and its precursors. We recommend a renewed focus on improvement of the representation of the chemistry of ship NOx emissions in current-generation models. We demonstrate the utility of ozone source attribution as a powerful model diagnostic tool, and recommend that similar source attribution techniques become a standard part of future model inter-comparison studies.

The California Baseline Ozone Transport Study (CABOTS)

Ozone is one of the six “criteria” pollutants identified by the U.S. Clean Air Act Amendment of 1970 as particularly harmful to human health. Concentrations have decreased markedly across the United States over the past 50 years in response to regulatory efforts, but continuing research on its deleterious effects have spurred further reductions in the legal threshold. The South Coast and San Joaquin Valley Air Basins of California remain the only two “extreme” ozone nonattainment areas in the United States. Further reductions of ozone in the West are complicated by significant background concentrations whose relative importance increases as domestic anthropogenic contributions decline and the national standards continue to be lowered. These background concentrations derive largely from uncontrollable sources including stratospheric intrusions, wildfires, and intercontinental transport. Taken together the exogenous sources complicate regulatory strategies and necessitate a much more precise understanding of the timing and magnitude of their contributions to regional air pollution. The California Baseline Ozone Transport Study was a field campaign coordinated across Northern and Central California during spring and summer 2016 aimed at observing daily variations in the ozone columns crossing the North American coastline, as well as the modification of the ozone layering downwind across the mountainous topography of California to better understand the impacts of background ozone on surface air quality in complex terrain.

Phase Space Analysis of Pig Ear Skin Temperature during Air and Road Transport

High or variable ambient temperature can affect thermal regulation in livestock, but few studies have studied thermal variability during air and road transport, partly due to the lack of tools to compare thermal data from a long time series over periods of different duration. In this study, we recorded the ear skin temperature (EST) of 11 Duroc breeder pigs (7 females and 4 males) during commercial intercontinental transport from Canada to Spain, which included both road and aircraft travel and lasted 65 h. The EST was measured using a logger placed inside the left ear. Phase space diagrams EST, that is EST time series vs. itself delayed in time, were used to quantify the variability of the time-temperature series based on the areas that included all the points in the phase space. Phase space areas were significantly higher for all the animals during air travel, almost doubling that of road transport. Using the phase spaces, we identified an event during air transport that lasted 57 min, leading to a general decrease in EST by 8 °C, with respect to the average EST (34.1 °C). We also found that thermal variability was more stable in males (F = 20.81, p = 0.0014), which were also older and heavier.

Is Summer African Dust Arriving Earlier to Barbados? The Updated Long-Term In Situ Dust Mass Concentration Time Series from Ragged Point, Barbados, and Miami, Florida

Surface dust mass concentrations, extracted from filters collected at Miami, Florida, and Ragged Point, Barbados, since 1974 and 1973, respectively, provide a rare, unusual, and important metric of the intercontinental transport of North African dust. The daily-resolved time series, updated through December 2018 for Miami and through December 2015 along with May–September 2016 and January–March and June–August 2017 for Barbados, indicate summer-mean dust mass concentrations have mostly decreased this decade at Miami, but not at Barbados, where instead the events containing the highest dust mass concentration events may be shifting to earlier in the year.