Towards a model for aerosol removal by rain scavenging: The role of physical-chemical characteristics of raindrops.

A one-year study was carried out in León, Spain, in order to characterize physically and chemically the precipitation. With the aim of studying the scavenging process of atmospheric pollutants, scavenging ratio and removal coefficients were calculated through physical parameters of raindrops (obtained by disdrometer data) and through chemical properties of aerosols. Finally, linear models for the prediction of the chemical composition of rainwater and the efficiency of the removal effect were established. In general, the rainwater was dominated by NH4+ > SO42- > NO3- in all seasons. Higher ion concentrations and conductivity and lowest pH were observed in summer, due to the low volume of rain. In winter, the high values of Na+ and Cl- in the rainwater showed the contribution from marine sources, while in summer the high concentrations of Ca2+, Mg2+, SO42-, NH4+ and NO3- reflected the contribution from both crustal and anthropogenic sources. The linear models revealed that the amount of dissolved organic carbon and of the water-soluble ions in rain samples, Ca2+, SO42-, NO3-, increases with the volume swept by the falling drops. Insoluble carbon fraction has a negative dependence with the volume swept and positive with the diameter of the raindrop. Removal coefficients are affected by the concentration in the air of each species before precipitation, the duration of the event and the time elapsed between two precipitation events.

The importance of contamination control in airborne fibers and microplastic sampling: Experiences from indoor and outdoor air sampling in Aveiro, Portugal.

Airborne microplastics and microfibers are released from daily materials, contaminating both indoor and outdoor air. Sampling in Aveiro, Portugal, revealed concentrations of 6 fibers m-3, with more synthetic fibers found in outdoor than indoor (8.5% vs. 4.1%, n = 6), with variations in fiber characteristics between sampling periods. Suspected microplastics (<10 µm) also followed this trend (12 vs. 5 particles m-3). Synthetic fibers presented peculiar characteristics, with larger median sizes of 513 µm and 90% of lighter colors. Nonetheless, numerous fibers and suspected microplastics were found in field blanks, possibly from sampling contamination, reducing the reliability of results. Few previous works have reported field blanks so far, raising concerns about the quality of their results as well. Thus, quality assurance measures should be more strictly applied when working with airborne fibers and microplastics, while more research should focus on the factors involved in the variation of concentrations and characteristics of airborne fibers.

Fine Particulate Matter and Gaseous Compounds in Kitchens and Outdoor Air of Different Dwellings.

Passive diffusion tubes for volatile organic compounds (VOCs) and carbonyls and low volume particulate matter (PM2.5) samplers were used simultaneously in kitchens and outdoor air of four dwellings. PM2.5 filters were analysed for their carbonaceous content (organic and elemental carbon, OC and EC) by a thermo-optical technique and for polycyclic aromatic hydrocarbon (PAHs) and plasticisers by GC-MS. The morphology and chemical composition of selected PM2.5 samples were characterised by SEM-EDS. The mean indoor PM2.5 concentrations ranged from 14 µg m-3 to 30 µg m-3, while the outdoor levels varied from 18 µg m-3 to 30 µg m-3. Total carbon represented up to 40% of the PM2.5 mass. In general, the indoor OC/EC ratios were higher than the outdoor values. Indoor-to-outdoor ratios higher than 1 were observed for VOCs, carbonyls and plasticisers. PAH levels were much higher in the outdoor air. The particulate material was mainly composed of soot aggregates, fly ashes and mineral particles. The hazard quotients associated with VOC inhalation suggested a low probability of non-cancer effects, while the cancer risk was found to be low, but not negligible. Residential exposure to PAHs was dominated by benzo[a]pyrene and has shown to pose an insignificant cancer risk.

An easy method for processing and identification of natural and synthetic microfibers and microplastics in indoor and outdoor air.

Microplastics and microfibers can contaminate every matrix, including in the atmosphere, thus leading to incidental inhalation. However, concentrations of airborne synthetic particle in indoor and outdoor environments are not well understood due to the complexities of sampling, sample processing and identification. This work aims at producing a simple protocol to determine the concentrations of airborne microplastics and fibers. This is accomplished by removing organic matter using hydrogen peroxide (H2O2), followed by removal of mineral matter by density separation with sodium iodide (NaI). Finally, identification of fibers into synthetic or natural under the stereomicroscope can be achieved following a diagram produced by systematically observing the most common textile fibers. This method produces a recovery rate of 94.4 % for spiked samples and has been proven suitable for environmental samples. •Fibers and microplastics in air are easier to identify after carbonaceous matter removal;•No loss of microfiber is expected from the solutions used;•Recovery rates of spiked samples is 94.4 %.

A one-year record of particle-bound polycyclic aromatic hydrocarbons at an urban background site in Lisbon Metropolitan Area, Portugal.

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic chemicals that are widely distributed in the atmosphere and well known for their adverse health effects. This study aims to describe, for the first time, the levels, sources and associated health risks of particulate PAHs in an urban background atmosphere of Lisbon, the capital and largest city in Portugal. PM10 aerosol samples were collected from early January to the end of December 2012 with a high-volume sampler and were later analyzed for 10 PAHs by high-performance liquid chromatography. The annual average of the sum of the concentrations of PAHs (ΣPAHs) was 1.64 ±â€¯1.85 ng/m3. The dominant PAHs were pyrene, chrysene, benzo[b]fluoranthene, fluoranthene and benzo[g,h,i]perylene. Together these species accounted for approximately 70% of the ΣPAHs. A marked seasonal variation was observed for the investigated PAHs, with the highest values in winter and the lowest in spring and summer, reflecting the variation of emissions and meteorological conditions over time. The average concentration of benzo[a]pyrene was found to be 0.107 ±â€¯0.152 ng/m3, not exceeding the target value of 1 ng/m3 established by European air quality legislation. Diagnostic ratios and principal component analysis were employed for the source apportionment of PAHs. Both tools indicated that vehicle exhaust was the main contributor to the atmospheric levels of PAHs in the study area.

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.

Elements and polycyclic aromatic hydrocarbons in exhaust particles emitted by light-duty vehicles.

The main purpose of this work was to evaluate the chemical composition of particulate matter (PM) emitted by eight different light-duty vehicles. Exhaust samples from petrol and diesel cars (Euro 3 to Euro 5) were collected in a chassis dynamometer facility. To simulate the real-world driving conditions, three ARTEMIS cycles were followed: road, to simulate a fluid traffic flow and urban with hot and cold starts, to simulate driving conditions in cities. Samples were analysed for the water-soluble ions, for the elemental composition and for polycyclic aromatic hydrocarbons (PAHs), respectively, by ion chromatography, inductively coupled plasma atomic emission spectroscopy (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and gas chromatography-mass spectrometry (GC-MS). Nitrate and phosphate were the major water-soluble ions in the exhaust particles emitted from diesel and petrol vehicles, respectively. The amount of material emitted is affected by the vehicle age. For vehicles ≥Euro 4, most elements were below the detection limits. Sodium, with emission factors in the ranges 23.5-62.4 and 78.2-227µg km(-1), for petrol and diesel Euro 3 vehicles, respectively, was the major element. The emission factors of metallic elements indicated that diesel vehicles release three to five times more than petrol automobiles. Element emissions under urban cycles are higher than those found for on-road driving, being three or four times higher, for petrol vehicles, and two or three times, for diesel vehicles. The difference between cycles is mainly due to the high emissions for the urban cycle with hot start-up. As registered for elements, most of the PAH emissions for vehicles ≥Euro 4 were also below the detection limits. Regardless of the vehicle models or driving cycles, the two- to four-ring PAHs were always dominant. Naphthalene, with emission factors up to 925 µg km(-1), was always the most abundant PAH. The relative cancer risk associated with naphthalene was estimated to be up to several orders of magnitude higher than any of the chemical species found in the PM phase. The highest PAH emission factors were registered for diesel-powered vehicles. The condition of the vehicle can exert a decisive influence on both element and PAH emissions.

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.

Assessment of river water quality using an integrated physicochemical, biological and ecotoxicological approach.

In order to maintain and improve the water quality in European rivers, the Water Framework Directive (WFD) requires an integrated approach for assessing water quality in a river basin. Although the WFD aims at a holistic understanding of ecosystem functioning, it does not explicitly establish cause-effect relationships between stressors and changes in aquatic communities. To overcome this limitation, the present study combines the typical WFD physicochemical and biological approaches with an ecotoxicological approach. The main goal was to assess river water quality through an integrated manner, while identifying potential risk situations for aquatic communities in the Cértima river basin (Portugal). To achieve this goal, surface water samples and macroinvertebrate specimens were collected under contrasting hydrological conditions (autumn and spring seasons) at three river sites exposed to distinct pollution levels defined according to the WFD (low, moderate and highly polluted). Physicochemical water quality status was defined according to the Portuguese classification for multipurpose surface waters, whereas biological water quality was assessed in accordance with the South Invertebrate Portuguese Index. Ecotoxicological assays included four standard species, a bacterial species (Vibrio fischeri), a unicellular algae (Pseudokirchneriella subcapitata), a macrophyte (Lemna minor) and a crustacean (Daphnia magna), which were exposed to different river water concentrations. The study sites represented a clear and pronounced gradient of pollution, from the unpolluted reference site to the sites under moderate to high anthropogenic pressure. In the latter sites, clear signs of organic pollution were found, such as low dissolved oxygen concentrations, high nutrient loads and prevalence of highly tolerant macroinvertebrate species. Despite the evident signs of pollution, no clear evidence of toxicity was observed in test species, suggesting that ecotoxicological assays using standard laboratory species and methodologies might not be suitable for assessing the effects of organic pollution. Nevertheless, the integrated methodology presented in this study provided important additional information on the Cértima's water quality status. Its wider use could contribute to a more comprehensive assessment of the effects of anthropogenic pollution on the status and functioning of aquatic ecosystems under the WFD and, thereby, improve the scientific foundations for the sustainable future management of surface water resources.

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.

Impact of water quality on bacterioplankton assemblage along Cértima River Basin (central western Portugal) assessed by PCR-DGGE and multivariate analysis.

The information on bacterial community composition (BCC) in Portuguese water bodies is very scarce. Cértima River (central western Portugal) is known to have high levels of pollution, namely organic. In the present work, the BCC from a set of 16 water samples collected from Cértima River Basin and its main tributaries was characterized using 16S rDNA-denaturing gradient gel electrophoresis, a culture-independent molecular approach. Molecular data were related to environmental parameters through multivariate analysis to investigate potential impact of water pollution along the river. Principal component analysis using environmental data showed a water quality gradient from more pristine waters (at the mountain tributaries) to waters with increasingly eutrophic potential (such as Fermentelos Lake). This gradient was mainly defined by factors such as organic and inorganic nutrient sources, electrical conductivity, hydrogen carbonate concentration, and pH. Molecular results showed variations in BCC along Cértima River Basin but in the main river section, a Bacteroidetes phylotype (Flavobacterium sp.) proved to be dominant throughout the river course. Multivariate analysis suggests that spatial variation of BCC along the Cértima River Basin depended mainly on parameters such as Chl a, total suspended solid (TSS), total organic carbon, electrical conductivity, and HCO[Formula: see text] levels. Bacteroidetes phylotypes were all related to higher electrical conductivity and HCO[Formula: see text] levels although some of these were also correlated with high SO[Formula: see text] and others with high soluble reactive phosphorus, nitrate, TN, and Kjeld-N levels. The Gammaproteobacteria occurrence was correlated with high SO[Formula: see text] levels. One of the Betaproteobacteria phylotypes showed to correlate with low redox potential (E(h)) and high temperature, pH, TSS, and Chl a levels while another one showed a negative correlation with Chl a values.

Size distribution of polycyclic aromatic hydrocarbons in a roadway tunnel in Lisbon, Portugal.

Atmospheric aerosols of four aerodynamic size ranges were collected using high volume cascade impactors in an extremely busy roadway tunnel in Lisbon (Portugal). Dust deposited on the tunnel walls and guardrails was also collected. Average particle mass concentrations in the tunnel atmosphere were more than 30times higher than in the outside urban background air, revealing its origins almost exclusively from fresh vehicle emissions. Most of the aerosol mass was concentrated in submicrometer fractions (65%), and polycyclic aromatic hydrocarbons (PAH) were even more concentrated in the finer particles with an average of 84% of total PAH present in sizes smaller than 0.49µm. The most abundant PAH were methylated phenanthrenes, fluoranthene and pyrene. About 46% of the total PAH mass was attributed to lower molecular weight compounds (two and three rings), suggesting a strong influence of diesel vehicle emissions on the production of local particulate PAH. The application of diagnostic ratios confirmed the relevance of this source of PAH in the tunnel ambient air. Deposited dust presented PAH profiles similar to the coarser aerosol size range, in agreement with the predominant origin of coarser aerosol particles from soil dust resuspension and vehicle wear products.

Spatial patterns of surface water quality in the Cértima River basin, central Portugal.

The Cértima River is the principal source of water flowing into the Pateira de Fermentelos, which is one of the largest natural lakes of the Iberian Peninsula and has elevated conservation value. This study aims at a more comprehensive understanding of the spatial pattern in water quality and, thus, pollution problems in and especially upstream of the Pateira, including a comparison with a prior study in 2003. To this end, surface water samples were collected, in May 2007, at 29 sites covering the basin's four main types of water bodies, and analysed for electrical conductivity, dissolved oxygen, biochemical oxygen demand, total suspended solids, various nitrogen species, orthophosphate and chlorophyll a. The results confirmed the existence of marked pollution along the middle section of the Cértima's main course, which can be attributed to wastewater discharges of urban and animal husbandry origin in particular. This represents an important eutrophication risk to the Pateira. Current legislation and water management does not appear to tackle this risk in an entirely satisfactory manner, since the spatial patterns as well as actual values of key physic-chemical parameters do not appear to have changed markedly between 2003 and 2007. Amongst the various parameters, biochemical oxygen demand stands out for frequently exceeding the legal water quality standards. The type of water body proved helpful to explain part of the variation in some of the parameters. This includes clear differences in electrical conductivity between the right- and left-bank tributaries, illustrating well the heterogeneous and complex character of the Cértima basin.