Worldwide Evaluation of CAMS-EGG4 CO2 Data Re-Analysis at the Surface Level.

This study systematically examines the global uncertainties and biases in the carbon dioxide (CO2) mixing ratio provided by the Copernicus Atmosphere Monitoring Service (CAMS). The global greenhouse gas re-analysis (EGG4) data product from the European Centre for Medium-Range Weather Forecasts (ECMWF) was evaluated against ground-based in situ measurements from more than 160 of stations across the world. The evaluation shows that CO2 re-analysis can capture the general features in the tracer distributions, including the CO2 seasonal cycle and its strength at different latitudes, as well as the global CO2 trend. The emissions and natural fluxes of CO2 at the surface are evaluated on a wide range of scales, from diurnal to interannual. The results highlight re-analysis compliance, reproducing biogenic fluxes as well the observed CO2 patterns in remote environments. CAMS consistently reproduces observations at marine and remote regions with low CO2 fluxes and smooth variability. However, the model's weaknesses were observed in continental areas, regions with complex sources, transport circulations and large CO2 fluxes. A strong variation in the accuracy and bias are displayed among those stations with different flux profiles, with the largest uncertainties in the continental regions with high CO2 anthropogenic fluxes. Displaying biased estimation and root-mean-square error (RMSE) ranging from values below one ppmv up to 70 ppmv, the results reveal a poor response from re-analysis to high CO2 mixing ratio, showing larger uncertainty of the product in the boundaries where the CAMS system misses solving sharp flux variability. The mismatch at regions with high fluxes of anthropogenic emission indicate large uncertainties in inventories and constrained physical parameterizations in the CO2 at boundary conditions. The current study provides a broad uncertainty assessment for the CAMS CO2 product worldwide, suggesting deficiencies and methods that can be used in the future to overcome failures and uncertainties in regional CO2 mixing ratio and flux estimates.

Air quality of an urban school in São Paulo city.

A major campaign was carried out in indoor and outdoor environments in a school located in the university campus of the city of São Paulo. Elements, PAH, oxy-PAH, water-soluble ions and black carbon were determined and compared with preliminary campaigns. The results indicated that the concentrations of particles and organic compounds were higher indoors. Some high molecular weight compounds, attributed to vehicular emissions, were more abundant outdoors. The associated health risk was found to be low. 2-Methylanthraquinone and benzo(a)anthracene-7,12-dione were detected in the indoor samples, denoting the infiltration of vehicle exhaust. The observation of black carbon also corroborates the contribution of traffic emissions. For most of the elements, except for chromium, iron and manganese, the concentrations obtained in indoors were higher than outdoors, mainly due to soil resuspension. Chromium and manganese likely derived from emissions of the vehicle powered by mixtures of ethanol and gasoline. Water-soluble inorganic ions species denoted the influence of soil resuspension and human activities.

Polycyclic aromatic hydrocarbons and their derivatives (nitro-PAHs, oxygenated PAHs, and azaarenes) in PM2.5 from Southern European cities.

Atmospheric particulate matter (PM2.5) samples were collected over two one month periods during winter and summer in three Southern European cities (Oporto - traffic site, Florence - urban background, Athens - suburban). Concentrations of 27 polycyclic aromatic hydrocarbons (PAHs), 15 nitro-PAHs (NPAHs), 15 oxygenated-PAHs (OPAHs) and 4 azaarenes (AZAs) were determined. On average, the winter-summer concentrations of ΣPAHs were 16.3-5.60, 7.75-3.02 and 3.44-0.658ngm-3 in Oporto, Florence and Athens, respectively. The corresponding concentrations of ΣNPAHs were 15.8-9.15, 10.9-3.36 and 15.9-2.73ngm-3, whilst ΣOPAHs varied in the ranges 41.8-19.0, 11.3-3.10 and 12.6-0.704ngm-3. Concentrations of ΣAZAs were always below 0.5ngm-3. Irrespective of the city, the dominant PAHs were benzo[b+j+k]fluoranthene, retene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene. The most abundant OPAH in all cities was 1,8-naphthalic anhydride, whereas 5-nitroacenaphthene was the prevailing NPAH. The ΣOPAHs/ΣPAHs and ΣNPAHs/ΣPAHs were higher in summer than in winter, suggesting increasing formation of derivatives by photochemical degradation of PAHs. Molecular diagnostic ratios suggested that, after traffic, biomass burning was the dominant emission source. Apart from being influenced by seasonal sources, the marked differences between winter and summer may indicate that these diagnostic ratios are particularly sensitive to photodegradation, and thus should be applied and interpreted cautiously. The lifetime excess cancer risk from inhalation was, in part, attributable to PAH derivatives, acclaiming the need to include these compounds in regular monitoring programmes. On average, 206, 88 and 26 cancer cases per million people were estimated, by the World Health Organisation method, for the traffic-impacted, urban background and suburban atmospheres of Oporto, Florence and Athens, respectively.

A one-year record of carbonaceous components and major ions in aerosols from an urban kerbside location in Oporto, Portugal.

PM2.5 aerosol samples were collected from January 2013 to January 2014 on the kerbside of a major arterial route in the city of Oporto, Portugal, and later analyzed for carbonaceous fractions and water soluble ions. The average concentrations of organic carbon (OC), elemental carbon (EC) and water soluble organic carbon (WSOC) in the aerosol were 6.2µg/m(3), 5.0µg/m(3) and 3.8µg/m(3), respectively, and fit within the range of values that have been observed close to major roads in Europe, Asia and North America. On average, carbonaceous matter accounted for 56% of the gravimetrically measured PM2.5 mass. The three carbon fractions exhibited a similar seasonal variation, with high concentrations in late autumn and in winter, and low concentrations in spring. SO4(2-) was the dominant water soluble ion, followed by NO3(-), NH4(+), Cl(-), Na(+), K(+), oxalate, Ca(2+), Mg(2+), formate, methanesulfonate and acetate. Some of these ions exhibited a clear seasonal trend during the study period. The average OC/EC ratio for the entire set of samples was 1.28±0.61, which was consistent with a significant influence of vehicle exhaust emissions on aerosol composition. On the other hand, the average WSOC/OC ratio was 0.67±0.23, reflecting the influence of other emitting sources. WSOC was highly correlated with nssK(+), a tracer of biomass combustion, and was not correlated with nssSO4(2-), a species associated with secondary processes, suggesting that the main source of WSOC was biomass burning. Most of the SO4(2-) was anthropogenic in origin and was closely associated with NH4(+), pointing to the formation of secondary aerosols. Na(+), Cl(-) and methanesulfonate were clearly associated with marine sources while NO3(-) was related with combustion of both fossil and non-fossil fuels. Mixed sources explained the occurrence of the other water soluble ions.

Wet deposition of particulate carbon to the Central North Atlantic Ocean.

Elemental carbon (EC) and water-insoluble organic carbon (WIOC) concentrations were measured in wet-only precipitation samples collected on Terceira Island (Azores, Portugal) between December 2009 and October 2010, to investigate temporal variations, source regions and wet deposition fluxes. The global volume-weighted average (vwa) concentrations were 134 ± 19 µgC L(-1) for WIOC and 15.0 ± 1.6 µgC L(-1) for EC, which fall within the range of values that have been found in the European background atmosphere. The WIOC concentration exhibited a temporal variation over the study period with a minimum in winter (vwa 88 ± 16 µgC L(-1)) and a maximum in summer (vwa 477 ± 86 µgC L(-1)). This trend was due to the higher dilution effect of winter rains and possibly to an increase of biogenic particulate carbon incorporation during the growing season. A different temporal variation was observed for the EC concentration with a minimum in summer (vwa 4.2 ± 3.3 µgC L(-1)) and a maximum in spring (vwa 17.5 ± 2.2 µgC L(-1)). The observed trend was mainly related to changes in atmospheric circulation patterns over the Azores. A backward trajectory analysis was applied to identify possible source regions of particulate carbon. The highest WIOC and EC concentrations were associated with air masses that persisted for more than four days over the Central North Atlantic Ocean and with air masses arriving from Europe, respectively. Lower concentrations were observed in samples collected under the influence of back-trajectories from North America. Despite the lower abundance of particulate carbon, the wet deposition fluxes were higher for this group of samples, which reflects the higher amount of precipitation that is normally associated with air masses arriving in the Azores from the west and northwest sectors.

Indoor and outdoor suspended particulate matter and associated carbonaceous species at residential homes in northwestern Portugal.

Particulate matter with an aerodynamic diameter equal to or less than 10 µm (PM10), organic carbon (OC) and elemental carbon (EC) concentrations were measured simultaneously in the indoor and outdoor air of 4 residences located in urban and sub-urban areas in northwestern Portugal. The residences were studied with occupants. One residence was also studied without any indoor activity, taking advantage of the fact that the occupants had moved into a new home. First, 48-h aerosol samples were collected on quartz fiber filters with low-volume samplers equipped with size selective inlets. The filters were weighed and then analyzed for OC and EC using a thermal-optical transmittance method. The average indoor and outdoor PM10 concentrations in the occupied residences were 71.9 ± 38.3 µg/m(3) and 54.0 ± 13.3 µg/m(3), respectively. Despite the higher concentration of PM10 indoors, outdoor sources were found to be a significant contributor to indoor concentrations. An estimate based on data from the residence studied under different occupancy conditions indicated that outdoor sources can account for 68% of the indoor PM10 mass concentration. Average indoor to outdoor (I/O) ratios for OC ranged from 1.7 to 5.6 in occupied residences, showing that indoor sources, such as cooking, smoking, biomass burning and movement of people, strongly influenced indoor OC concentrations. In contrast, I/O ratios for EC were close to 1, except for a smokers' residence, suggesting that indoor concentrations were mainly controlled by outdoor sources, most likely from vehicular emissions and biomass burning.