Sensitivity of PM10 oxidative potential to aerosol chemical composition at a Mediterranean urban site: ascorbic acid versus dithiothreitol measurements.

The oxidative potential (OP) of PM10 daily samples collected at a traffic site in southeastern Spain during summer and winter was assessed by two acellular assays: the ascorbic acid (AA) and dithiothreitol (DTT) methods. Although PM10 levels were similar during both periods, OP values (expressed in nmol min-1 m-3) showed a defined seasonal trend. The AA activity was higher in summer than in winter, whereas the DTT reactivity exhibited an opposite seasonal pattern. Both assays were sensitive to different PM10 components, as shown by the results of the linear correlation analysis. Moreover, the relationship between OP values and PM10 chemical species was not the same during summer and winter, indicating that particle toxicity is associated with different sources during the warm and cold seasons. When OP values were expressed on a mass basis (nmol min-1 µg-1), lower correlation coefficients with PM10 chemical species were generally obtained compared to volume-normalized activities. These outcomes suggest that only some specific components have a significant intrinsic oxidative potential. Supplementary Information: The online version contains supplementary material available at 10.1007/s11869-023-01332-1.

Size segregated ionic species collected in a harbour area.

Water-soluble ions were analysed in size segregated aerosol samples collected in the port of Alicante (Southeastern Spain) during summer and winter using a multistage cascade impactor. Seasonal variations in the size distributions of the analysed components and the influence of bulk materials handling (loading/unloading and stockpiling) at the docks were investigated. The size distributions of SO42-, NH4+ and K+ were characterized by prominent peaks in the condensation and droplet modes, both in summer and winter, while those of Ca2+, Na+, Mg2+ and Cl- had a main peak centred at ∼4 µm. Although oxalate size distributions were similar during both seasons, the fraction of coarse-mode oxalate increased in summer most likely as a result of volatilization and repartition processes or reactions of oxalic acid with coarse alkaline particles. Nitrate size distributions were dominated by a coarse mode; however, during winter, modal peaks in the submicron size range were also observed due to favourable conditions for the formation of fine-mode NH4NO3. Harbour activities had a significant impact only on the concentrations of calcium, particularly in the coarse fraction, during both summer and winter.

Quantification of the impact of port activities on PM10 levels at the port-city boundary of a mediterranean city.

The main objective of this work was to quantify the impact of handling of bulk materials on PM10 levels measured at the port-city border of Alicante (Spain), located on the western Mediterranean coast. To achieve that goal, 355 PM10 samples were collected at the perimeter of the harbor of Alicante from March 2017 to February 2018. A 181 sample subgroup was chemically characterized in order to perform a source apportionment study with the EPA PMF 5.0 model. Eight factors were identified, two of them directly related to the handling of bulk materials (Limestone + gypsum and Clinker), accounting jointly for 35% of the average PM10 concentration. A Road traffic factor was the second highest contributor to PM10 levels (17%) while the Shipping emissions factor accounted for only 6% of the average PM10 mass. Other factors such as Biomass burning+ secondary nitrate and Aged sea salt represented a joint contribution of 25% of the PM10 mass. Results indicate that emission abatement strategies should primarily focus on the reduction of fugitive emissions caused by the handling of bulk materials at the docks. Moreover, scenarios including reductions of more than 50% in bulk handling sources and 10% in other anthropogenic sources would help to reduce anthropogenic exceedances of the daily PM10 limit (50 µg·m-3) and to approach to WHO daily PM10 standard (20 µg m-3).

Insights into the origin and evolution of carbonaceous aerosols in a mediterranean urban environment.

Organic carbon (OC) and elemental carbon (EC) concentrations were measured in PM1 and PM10 daily samples collected at an urban station in Elche (southeastern Spain) from February 2015 to February 2018. The effect of seasonal weather conditions, traffic, and specific pollution events (Saharan dust outbreaks and local pollution episodes) on the variability of carbonaceous aerosol levels was studied in this work. The joint contribution of carbonaceous species to PM1 and PM10 mass concentrations was, respectively, 48% and 26%. Both OC and EC concentrations were higher in winter than in summer because of the poor dispersion conditions and lower temperatures leading to the condensation of semivolatile species. Secondary organic carbon (SOC), estimated using the EC tracer method, also exhibited higher concentrations during winter, indicating that the prevailing meteorological conditions during the cold season are more favorable for the formation of secondary organic aerosols. Our results suggest different formation pathways of secondary organic components during summer and winter. At the sampling site, EC was primarily derived from traffic emissions, independently of the season and the type of event, with a modest contribution from biomass burning (<20%). The estimated contribution from this source to OC levels was similar. Local pollution episodes lead to a significant increase in the concentrations of carbonaceous species, in particular of SOC, influencing its temporal variation. On average, African dust outbreaks showed a moderate impact on the levels of carbonaceous aerosols; however, the effect was significantly stronger during winter Saharan events.

Characterization of metals in PM1 and PM10 and health risk evaluation at an urban site in the western Mediterranean.

PM1 and PM10 samples collected in the urban center of Elche during two years were analyzed by Energy Dispersive X-Ray Fluorescence in order to determine the concentrations of the following metals: K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr and Ba. The influence of traffic and Saharan dust intrusions on PM levels and metal content was studied in this work. The results indicate that the coarse fraction was affected more by variations in traffic intensity than the submicron fraction. The concentrations of Ca, commonly used as a tracer of road dust, showed the highest decreases during the weekends due to the reduction in traffic-induced resuspension. In contrast, Saharan events had a greater impact on the levels of other metals such as Ti and Fe, significantly affecting their seasonal variability. High concentrations of V and Ni compared with the values found at larger urban areas were observed. This could be attributed to a significant contribution from soils, Saharan dust and even ship emissions. Enrichment factors calculated using Ti as a reference element indicate that Zn and Cu are predominantly emitted by anthropogenic activities. In fact, Saharan dust intrusions had a minor influence on the average concentrations of these metals. Non-carcinogenic health hazards associated with exposure to airborne metals were lower than the safety threshold (hazard quotient < 1). Carcinogenic risks for Cr (VI) and Ni were between 10-6 and 10-4 and, therefore, within the range considered acceptable by the US EPA.

Depletion of tropospheric ozone associated with mineral dust outbreaks.

From May to September 2012, ozone reductions associated with 15 Saharan dust outbreaks which occurred between May to September 2012 have been evaluated. The campaign was performed at a mountain station located near the eastern coast of the Iberian Peninsula. The study has two main goals: firstly, to analyze the decreasing gradient of ozone concentration during the course of the Saharan episodes. These gradients vary from 0.2 to 0.6 ppb h(-1) with an average value of 0.39 ppb h(-1). The negative correlation between ozone and coarse particles occurs almost simultaneously. Moreover, although the concentration of coarse particles remained high throughout the episode, the time series shows the saturation of the ozone loss. The highest ozone depletion has been obtained during the last hours of the day, from 18:00 to 23:00 UTC. Outbreaks registered during this campaign have been more intense in this time slot. The second objective is to establish from which coarse particle concentration a significant ozone depletion can be observed and to quantify this reduction. In this regard, it has been confirmed that when the hourly particle concentration recorded during the Saharan dust outbreaks is above the hourly particle median values (N > N-median), the ozone concentration reduction obtained is statistically significant. An average ozone reduction of 5.5 % during Saharan events has been recorded. In certain cases, this percentage can reach values of higher than 15 %.

Temporal variations of PM1 major components in an urban street canyon.

Seasonal changes in the levels of PM1 and its main components (organic carbon (OC), elemental carbon (EC), SO4 (2-), NO3 (-) and NH4 (+)) were studied in an urban street canyon in southeastern Spain. Although PM1 levels did not show an evident seasonal cycle, strong variations in the concentrations of its major components were observed. Ammonium sulfate, the main secondary inorganic compound, was found to be of regional origin. Its formation was favored during summer due to increased photochemical activity. In contrast, the concentrations of particulate ammonium nitrate, which is thermally unstable, were highest in winter. Although traffic emissions are the dominant source of EC in the city, variations in traffic intensity could not explain the seasonal cycle of this component. The higher EC concentrations during the cold months were attributed to the lower dispersion conditions and the increase in EC emissions. Special attention has been given to variations in organic carbon levels since it accounted for about one third of the total PM1 mass. The concentrations of both total OC and secondary OC (SOC) were maxima in winter. The observed seasonal variation in SOC levels is similar to that found in other southern European cities where the frequency of sunny days in winter is high enough to promote photochemical processes.

Impacts on particles and ozone by transport processes recorded at urban and high-altitude monitoring stations.

In order to evaluate the influence of particle transport episodes on particle number concentration temporal trends at both urban and high-altitude (Aitana peak-1558 m a.s.l.) stations, a simultaneous sampling campaign from October 2011 to September 2012 was performed. The monitoring stations are located in southeastern Spain, close to the Mediterranean coast. The annual average value of particle concentration obtained in the larger accumulation mode (size range 0.25-1 µm) at the mountain site, 55.0 ± 3.0 cm(-3), was practically half that of the value obtained at the urban station (112.0 ± 4.0 cm(-3)). The largest difference between both stations was recorded during December 2011 and January 2012, when particles at the mountain station registered the lowest values. It was observed that during urban stagnant episodes, particle transport from urban sites to the mountain station could take place under specific atmospheric conditions. During these transports, the major particle transfer is produced in the 0.5-2 µm size range. The minimum difference between stations was recorded in summer, particularly in July 2012, which is most likely due to several particle transport events that affected only the mountain station. The particle concentration in the coarse mode was very similar at both monitoring sites, with the biggest difference being recorded during the summer months, 0.4 ± 0.1cm(-3) at the urban site and 0.9 ± 0.1cm(-3) at the Aitana peak in August 2012. Saharan dust outbreaks were the main factor responsible for these values during summer time. The regional station was affected more by these outbreaks, recording values of >4.0 cm(-3), than the urban site. This long-range particle transport from the Sahara desert also had an effect upon O3 levels measured at the mountain station. During periods affected by Saharan dust outbreaks, ozone levels underwent a significant decrease (3-17%) with respect to its mean value.

Impact of fugitive emissions in ambient PM levels and composition: a case study in Southeast Spain.

The results of this study show the high impact that anthropogenic fugitive emissions of mineral dust have on air quality (levels of PM(10), PM(2.5) and some metals) in a region in SE Spain named L'Alacantí. This could be extensive to other areas of Europe with similar characteristics. Fugitive emissions, such as those arising from large public construction works, cement and ceramic manufacturing, mining, heavy industries, handling and transport of powdered raw materials and road dust, are very often left out of emission monitoring and inspections in Europe. The comparative study of daily PM(10) series in the area shows how the increase of annual average PM(10) concentrations over 40 microg/m(3) is due to extreme episodes occurring in 2006 and 2007, at a regional scale, given the simultaneous recording of PM episodes at distant monitoring sites. The annual average values of the PM(10) concentrations were close to or slightly higher than 40 microg/m(3) (limit value of Directive 2008/50/CE) during 2006-2007 (Alicante-University 39-41, Agost 40-42, Sant Vicent 42-46, Alicante-El Plà 40-42 microg/m(3)). The main PM(10) sources in the zone were identified with the assistance of the PMF receptor model. Six common factors were determined, mineral as a main source (37% at Agost and 32% at Sant Vicent), road traffic, secondary sulfate, petroleum coke, sea spray and industry. Mineralogical studies, with XRD and SEM-EDX techniques, support the hypothesis that the highest PM episodes are associated to fugitive emissions of mineral matter. Despite the fact that L'Alacantí region is a heavily industrialized area with two cement plants and a significant number of ceramic manufacturing plants, the fugitive emissions may have accounted for the exceedances of the PM limit values during these two years, part of them caused by the construction of a highway. These results may contribute to the interpretation of prior studies on source apportionment carried out in Southern Europe, with very high loads of anthropogenic dust in PM(10) and PM(2.5).