Mining activities increase contaminant levels in the environment, so it is crucial to study the particulate matter in these areas to understand the impacts on nearby urban areas and populations. This work was conducted close to the active mine of Aljustrel (Portugal), where black dust deposition is evident. PM10 samples were collected in two periods: 10–17 July and 1–10 November of 2018. Two different techniques were used: SEM-EDX for the individual characterization of the aerosols and ICP-MS to quantify the elemental concentration of 11 elements (Ca, Na, Fe, Mn, As, Cd, Cu, Sb, Pb, and Zn). In this region, the observed PM10 mass concentration was 20 to 47 µg m −3 (July) and 4 to 23 µg m−3 (November), which is lower than the limit of 50 μg m−3 established in the European Directive. The individual characterization of 2006 particles by SEM-EDX shows oxides (17%) and sulfides (10%), while Na, Si, Fe, S, Al, and Cu are the elements with the most representativeness in all the analyzed particles. The ICP-MS results indicate that the daily elemental concentration in the samples collected in July is higher than November, and only As exceeds the limit established for European legislation.
Continuous measurements of the optical properties of aerosol particles have been made at Valladolid, Spain, covering the period from June 2011 to July 2012. The measurements were made at two size cuts: sub-10 μm and sub-1 μm (PM10 and PM1). The data measured were the scattering and backscattering coefficients, σ and σ, obtained from an integrating nephelometer, and the absorption coefficient, σ, obtained from a particle soot absorption photometer. Spectrally resolved data were obtained from both instruments at 3 wavelengths (blue/green/red) at low relative humidity (RH < 40%). The statistical data for the instruments were calculated based on the hourly averages. For the PM10 fraction, the hourly mean values of σ and σ at 550 nm were 33 Mm (StD = 30 Mm) and 4 Mm (StD = 3 Mm), respectively. For the PM1 fraction, σ and σ mean values were 16 Mm (StD = 14 Mm) and 4 Mm (StD = 3 Mm), also at 550 nm. The derived parameters analyzed were the single scattering albedo, ω, the backscatter fraction, σ/σ, and the Ångström exponents of scattering, absorption and single scattering albedo, α, α and α. The contribution of the PM10 and the PM1 fractions for all these parameters plays a central role throughout the paper, allowing an improved classification of aerosol types. Our data are dominated by elemental carbon (EC) and elemental carbon/organic carbon mixed (EC/OC). For the PM10 data, dust dominated aerosol is also observed. Although we found that fine particles contribute more than coarse particles for decreasing the ω values, results suggest that it is also necessary to quantify the effect of coarse particles. Fine particles were found to produce ω spectra that decrease with the wavelength, α > 0, while PM10 fractions were found to produce spectra that can decrease or increase with the wavelength, 0 < α < 0. Both daily cycle and monthly variations are analyzed and related to local features as well as the transport of particles from elsewhere. A diurnal pattern characteristic of urban areas is observed, but it is less evident on weekends. The main long range transport influences are Atlantic advection, anthropogenic events from Central Europe and dust events.
Wildfires can cause serious imbalances in ecosystems, primarily at the soil level, making it vulnerable to degradation processes such as erosion. During and after a fire, changes occur in soil properties, including pH, which affects the solubility and availability of nutrients. Currently, there is a great diversity of protocols, some involving normalized standards, to determine soil pH, but there is no consensual or universal analytical method for this parameter, especially in burned soils, in which mineral and organic fractions could have been modified. Therefore, the objective of the present work is to evaluate the effect that variations in these analytical protocols may have on pH results. For this, five methods commonly found in the international bibliography for the analysis of pH of soil in water (pHH2O) were selected and compared to propose the most precise procedure. The analytical methods were applied to 43 soil samples, collected in a plot subjected to prescribed burning in the Parque Natural de Montesinho (Northern Portugal). The studied methods differ in the following protocol items: water suspension ratio (1:2.5 or 1:5), mechanical stirring time in the suspension (10 min or 1 h), and in the resting time for the solid particles to settle (15 min or 8 h). The obtained results point to the suitability of the five methods used for soil pH analysis, indicating that there are no statistically significant differences. However, results also allow suggesting a more appropriate method concerning practical reasons, such as labor in a lab. Thus, to make the analysis process more profitable, M2 is a good option because it uses a small amount of sample (5 g), short agitation (10 min) and settling time (15 min). In turn, M1 and M5, which use a lower proportion of soil (1:2.5) show lower pH variation in the measurements. This fact may be explained by a smaller dilution effect. Considering that these two methods differ in the settling time, it is suggested to apply M1, because only 15 min are required. Therefore, the main conclusion reached with this work is that the measurement of soil pH using M1, i.e., a soil:water ratio of 1:2.5, with agitation of 10 min and settling time of 15 min, is a robust and more expeditious protocol to be applied to soil samples after a fire.
<p>Mining activities are associated with dust emissions and increased contaminant levels in the environment, due to excavation, crushing and transportation of ore and the generation of a high amount of polluting wastes. Therefore, it is crucial to study the particulate matter in these areas to understand their impacts on nearby urban areas and populations (Csavina <em>et al.</em>, 2012). Analysis PM<sub>10</sub> samples collected near the active mining area of Aljustrel (SW Portugal) allowed to do an individual characterization and to investigate the contaminants levels and aerosols sources. In Aljustrel, the exploitation of volcanogenic massive sulphides (VMS) deposits has been done since pre-Roman times, releasing great quantities of mine wastes, which have contaminated the soils (Candeias, <em>et al</em>. 2011). Now the exploitation is done underground, but even so, the ore processing plant releases dust, which is transported by wind to the village.</p><p>The PM<sub>10</sub> samples were collected in two points at the southeast of the ore processing plant. The sampling was done in two periods July 10-17 and November 1-10 of 2018. Two different techniques were used: SEM-EDX for the individual characterization and ICP-MS for the elemental concentration of 11 elements (Ca, Na, Fe, Mn, As, Cd, Cu, Sb, Pb, and Zn). PM<sub>10</sub> mass concentration observed was 20 to 47 &#181;g m<sup>-3</sup> (July) and 4 to 23 &#181;g m<sup>-3</sup> (November) which is lower than the limit of 50 &#956;g m<sup>-3</sup> established in the European Directive (Directive 2008/50/CE of May 21). The individual characterization of 2006 particles by SEM-EDX shows the presence of oxides (17%) and sulphides (10%) in the aerosols, and the elements Na, Si, Fe, S, Al and Cu are those with the most representativeness in all the analyzed particles. The Principal Component Analysis (PCA) allowed to distinguish the main sources of aerosols. Five factors were extracted (72% of the total variance of the data): CP1 is defined by O, Al, Si and Fe, the geogenic elements; CP2 is defined by As and Pb, CP3 is defined by S, CP4 defined by Cu and Zn; and finally, the CP5 defined by Mn. These factors are related to the ore minerals. The ICP-MS results indicate that daily elemental concentration in the samples collected in July is higher than in those collected in November, for each element. The elements Fe, Cu, Zn, As, Cd, Sb, Pb have strong correlations (&#945;&#160;=&#160;0.05, r&#160;>&#160;0.93) and are the main constituents of the ore minerals. Therefore, these elements will have an anthropogenic source. Comparing the concentration of some pollutes (As, Cd, and Pb) with their limits in the European legislation only As exceeds its limit in all samples.</p><p>This work was the first study about atmospheric aerosols developed in this area and shows a strong relationship between PM<sub>10</sub> analyzed and the ore exploited in Aljustrel, indicating implications in the quality of the air for the resident population. Even if some limits are not exceeded, the continuous exposition over many years is a potential hazard.</p>
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