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 (pH_H2O) 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.

Abandoned mines pose environmental risks due to the accumulation of sulfide-rich waste, which generates acid mine drainage and produces fine-grained, unconsolidated materials that, when deposited on steep slopes, accelerate erosion and contaminant transport. This study assesses the environmental impact of the Trimpancho mining complex by integrating UAV-based photogrammetry, water analysis, and mine waste characterization. Aerial surveys produced high-resolution orthomosaics and digital surface models, enabling the identification of runoff patterns, erosion hotspots, and waste accumulation. The estimated waste volume is approximately 253,377 m³ . Key findings highlight critical erosion areas on steep slopes (>30°) where waste mobilization enhances metal and sulfate transport into the Trimpancho stream, affecting the Chança River. Water samples have pH values ranging from 2.59 to 8.27, electrical conductivity peaking at 4171 µS/cm, and elevated concentrations of iron (65.7 mg/L), aluminum (174 mg/L), manganese (23.5 mg/L), and zinc (20.7 mg/L). Mine waste characterization revealed that Nuestra Señora del Carmen dump exhibited higher leaching potential compared to Volta Falsa. This study underscores the value of UAV technology for cost-effective and high-resolution environmental monitoring in abandoned mines. The results emphasize the need for targeted remediation strategies and water quality improvement. This multi method approach can serve as a model for assessing contamination risks and optimizing environmental monitoring programs in other legacy mining sites.

In natural waters, total dissolved solids (TDS) are usually estimated from electrical conductivity (EC) by applying a conversion factor (f). However, defining this conversion factor for mining influenced water is more complex since this type of water is highly mineralized and has complex chemical matrices. So, the present work aimed to establish a new conversion factor to estimate TDS from the classic parameters usually analyzed for the hydrochemical characterization of these contaminated waters. A total of 121 mining influenced water samples were collected in three mining areas representing pollution scenarios, such as acidic streams, acidic lagoons, and pit lakes. The parameters analyzed were pH, EC, sulfate, acidity, and TDS. The statistical analysis showed that TDS and acidity are related, with a high and significant correlation (r ≥ 0.964, ρ < 0.001), suggesting that this parameter could be an appropriate indicator to estimate the TDS. Moreover, although acidity analysis also involves laboratory work, the time and effort required are considerably less than the gravimetric determination of TDS. Hierarchical cluster analysis applied to these samples allowed the definition of seven classes, and their specific f_median was calculated employing TDS/Acidity. Then, seven conversion factors were obtained for mining influenced water based on sulfate concentration and acidity degree.

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_s and σ_bs, obtained from an integrating nephelometer, and the absorption coefficient, σ_a, 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_s and σ_a at 550 nm were 33 Mm⁻¹ (StD = 30 Mm⁻¹) and 4 Mm⁻¹ (StD = 3 Mm⁻¹), respectively. For the PM1 fraction, σ_s and σ_a mean values were 16 Mm⁻¹ (StD = 14 Mm⁻¹) and 4 Mm⁻¹ (StD = 3 Mm⁻¹), also at 550 nm. The derived parameters analyzed were the single scattering albedo, ω₀, the backscatter fraction, σ_bs/σ_s, and the Ångström exponents of scattering, absorption and single scattering albedo, α_s, α_a and α ω₀ . 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 ω₀ values, results suggest that it is also necessary to quantify the effect of coarse particles. Fine particles were found to produce ω₀ spectra that decrease with the wavelength, α ω₀ > 0, while PM10 fractions were found to produce spectra that can decrease or increase with the wavelength, 0 < α ω₀ < 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.

The long-term environmental legacy of mining in sulfide-rich regions remains a critical concern due to the persistent generation of acid mine drainage (AMD) and the mobilization of potentially toxic elements (PTEs). This study presents a comprehensive, site-specific assessment of mine waste from two contrasting geochemical zones, Nuestra Señora del Carmen (NSC) and Volta Falsa (VF), within the historically under-characterized Trimpancho Mining Complex, located in the Iberian Pyrite Belt (IPB). A multidisciplinary approach combining mineralogical characterization, physicochemical and geochemical analyses, multivariate statistics, and contamination indices, provided insights into the behavior, mobility, and ecological risk of key PTEs such as Cu, As, and Zn. The NSC zone is dominated by pyrite and secondary sulfates, promoting acidic conditions (pH values ranging from 2.42 to 3.60) and high Cu mobility, whereas VF waste materials show a more heterogeneous mineralogy, higher pH (ranging from 2.77 to 5.05), and broader PTE enrichment. Principal Component Analysis revealed distinct geochemical regimes shaped by the presence of sulfides or silicates. Contamination indices underscored significant ecological risk in both zones, but with distinct pollution signatures. This integrated framework supports site-specific environmental risk management and remediation strategies and applies to other AMD-impacted volcanogenic massive sulfide (VMS) mining environments facing renewed exploration pressures.