Aerial monitoring of atmospheric particulate matter produced by open-pit mining using low-cost airborne sensors.

Mining is an economic activity that entails the production and displacement of significant amounts of atmospheric particulate matter (PM) during operations involving intense earthcrushing or earthmoving. As high concentrations of PM may have adverse effects on human health, it is necessary to monitor and control the fugitive emissions of this pollutant. This paper presents an innovative methodology for the online monitoring of PM10 concentrations in air using a low-cost sensor (LCS, <300 USD) onboard an unmanned aerial vehicle. After comprehensive calibration, the LCS was horizontally flown over seven different areas of the large Riotinto copper mine (Huelva, Spain) at different heights to study the PM10 distribution at different longitudes and altitudes. The flights covered areas of zero activity, intense mining, drilling, ore loading, waste discharge, open stockpiling, and mineral processing. In the zero-activity area, the resuspension of PM10 was very low, with a weak wind speed (3.6 m/s). In the intense-mining area, unhealthy concentrations of PM10 (>51 µgPM10/m3) could be released, and the PM10 can reach surrounding populations through long-distance transport driven by several processes being performed simultaneously. Strong dilution was also observed at high altitudes (> 50 m). Mean concentrations were found to be 22-89 µgPM10/m3, with peaks ranging from 86 to 284 µgPM10/m3. This study demonstrates the potential applicability of airborne LCSs in the high-resolution online monitoring of PM in mining, thus supporting environmental managers during decision-making against fugitive emissions in a cost-effective manner.

Source contribution and origin of PM10 and arsenic in a complex industrial region (Huelva, SW Spain).

Air pollution coming from industrial activities is a matter of interest since their emissions can seriously affect to the human health of nearby populations. A more detailed study about industrial emissions is required in order to discriminate different activities contributing to pollutant sources. In this sense, gaseous pollutants (NO2, SO2 and O3) and PM10 levels has been studied in a complex industrial area in the southwest of Spain (La Rabida and the nearby city of Huelva) during the period 1996-2017. Hourly, daily, monthly and annual variations of PM10 and gaseous pollutants concentrations point to the industrial activity as the main SO2 source. Furthermore, traffic and resuspension emissions contribute to the NO2 and PM10 levels, respectively. Results from chemical composition of PM10 at both sites during the period 2015-2017 are characterized by high concentrations of the crustal components derived from natural and local resuspension. Arsenic is found to be the main geochemical anomaly at La Rabida (annual mean of 7 ng m-3), exceeding the European annual target of 6 ng m-3, which supposes a risk for the nearby population. An emission source from Cu-smelter has been identified in La Rabida and Huelva. A second source corresponding to emissions from polymetallic sulfides handling in a port area has been described for the first time in La Rabida. In addition, arsenic speciation results have identified three different As impacts scenarios as a function of the dominant wind direction, the SO2 episodes and the As extraction efficiency: impact of the Cu-smelter, impact of the bulk polymetallic sulfides and a mixed impact of both sources.

Hazardous trace elements in thoracic fraction of airborne particulate matter: Assessment of temporal variations, sources, and health risks in a megacity.

The deleterious health effects of thoracic fractions seem to be more related to the chemical composition of the particles than to their mass concentration. The presence of hazardous materials in PM10 (e.g., heavy metals and metalloids) causes risks to human health. In this study, twelve trace elements (Cd, Cr, Pb, Zn, Cu, Ni, Sn, Ba, Co, As, V, and Sb) in 315 samples of ambient PM10 were analyzed. The samples were collected at an urban background site in a Latin American megacity (Bogota, Colombia) for one year. The concentrations and temporal variabilities of these elements were examined. According to the results, Cu (52 ng/m3), Zn (44 ng/m3), Pb (25 ng/m3), and Ba (20 ng/m3) were the traces with the highest concentrations, particularly during the dry season (January to March), which was characterized by barbecue (BBQ) charcoal combustion and forest fires. In addition, the differences between the results of weekdays and weekends were identified. The determined enrichment factor (EF) indicated that Zn, Pb, Sn, Cu, Cd, and Sb mainly originated from anthropogenic sources. Moreover, a speciation analysis of inorganic Sb (EF > 300) was conducted, which revealed that Sb(V) was the main Sb species in the PM10 samples (>80%). Six causes for the hazardous elements were identified based on the positive matrix factorization (PMF) model: fossil fuel combustion and forest fires (60%), road dust (19%), traffic-related emissions (9%), copper smelting (8%), the iron and steel industry (2%), and an unidentified industrial sector (2%). Furthermore, a health risk assessment of the carcinogenic elements was performed. Accordingly, the cancer risk of inhalation exposure to Co, Ni, As, Cd, Sb(III), and Pb was negligible for children and adults at the sampling site. For adults, the adjusted Cr(VI) level was slightly higher than the minimal acceptable risk level during the study period (1.4 × 10-6).

Trace elements in sediments and fish from Atrato River: an ecosystem with legal rights impacted by gold mining at the Colombian Pacific.

The Atrato watershed is a rainforest that supports exceptional wildlife species and is considered one of the most biodiversity-rich areas on the planet, currently threatened by massive gold mining. Aimed to protect this natural resource, the Constitutional Court of Colombia declared the river subject to rights. The objective of this study was to quantify trace elements in sediments and fish from Atrato watershed, assessing their environmental and human health risk. Forty-two trace elements were quantified using ICP-MS. Thirty-one elements increased their concentration downstream the river. Concentration Factors (CF) suggest sediments were moderately polluted by Cr, Cu, Cd, and strongly polluted by As. Most stations had Cr (98%) and Ni (78%) concentrations greater than the Probable Effect Concentration (PEC) criteria. Together, toxic elements generate a Pollution Load Index (PLI) and a Potential Ecological Risk Index (RI) that categorized 54% of the sediments as polluted, and 90% as moderate polluted, respectively. Hemiancistrus wilsoni, a low trophic guild fish species, had the greater average levels for Ni, Cu, As and Cd, among other elements. Rubidium and Cs showed a positive correlation with fish trophic level, suggesting these two metals biomagnify in the food chain. The Hazard Quotient (HQ) for As was greater than 1 for several species, indicating a potential risk to human health. Collectively, data suggest gold mining carried out in this biodiversity hotspot releases toxic elements that have abrogated sediment quality in Atrato River, and their incorporation in the trophic chain constitutes a large threat on environmental and human health due to fish consumption. Urgent legal and civil actions should be implemented to halt massive mining-driven deforestation to enforce Atrato River rights.

The geochemical evolution of brines from phosphogypsum deposits in Huelva (SW Spain) and its environmental implications.

The present study focuses on the geochemistry of large phosphogypsum deposits in Huelva (SW Spain). Phosphogypsum slurry waste from fertiliser production was disposed in large ponds containing aqueous waste (i.e. brines) and exposed to weathering. These evaporation ponds were found to be dynamic environments far from attaining steady state conditions where a number of trace pollutants are subjected to temporal variations in response to changing environmental conditions. Chemical, mineralogical and morphological data were used to improve our understanding on the dynamics of a large number of elements in the phosphogypsum-brine-evaporation deposits system. Weekly sampling of brines over the course of 1 yr indicated a substantial enrichment in potentially harmful elements (e.g. As, Cr, Cu, F, Ni, U, V, Zn) present in time-dependent concentrations. The evaporation deposits formed multi-layered precipitates of chlorides, sulphates, phosphates and fluorides containing a large number of pollutants in readily soluble forms. The precipitation sequence revealed a time-dependent composition reflecting alternating precipitation and re-dissolution processes associated with seasonal changes in the local weather conditions. Concatenation of precipitation/re-dissolution stages was found to progressively enrich the brines in pollutants. These findings were supported by the observations from a tank experiment simulating the phosphogypsum-brine-evaporation deposits system under laboratory conditions. Given the substantially high concentrations of pollutants present in mobile forms in the brine-salt system, actions to abate these compounds should be implemented.

Physicochemical characterization and sources of the thoracic fraction of road dust in a Latin American megacity.

Road dust has been identified as one of the main sources of outdoor PM10 in Bogota (a Latin American megacity), but there are no studies that have analyzed the physicochemical characteristics and origins of its respirable fraction. A characterization of inorganic compounds (water soluble ions, major and trace elements, organic and elemental carbon) and an analysis of source contributions to the PM10 fraction of road dust were carried out in this study. A total of twenty road dust samples, selected from representative industrial, residential and commercial areas, were swept and resuspended to obtain the thoracic fraction. Size distribution by laser diffraction and individual particle morphology by Scanning Electron Microscopy were also evaluated. The data obtained revealed that the volume (%) of thoracic particles was higher in samples from industrial zones where heavy vehicular traffic, industrial emissions and deteriorated pavements predominated. Crustal elements were the most abundant species, accounting for 49-62% of the thoracic mass, followed by OC (13-29%), water-soluble ions (1.4-3.8%), EC (0.8-1.9%) and trace elements (0.2-0.5%). The Coefficient of Divergence was obtained to identify the spatial variability of the samples. A source apportionment analysis was carried out considering the variability of chemical profiles, enrichment factors and ratios of Fe/Al, K/Al, Ca/Al, Ti/Al, Cu/Sb, Zn/Sb, OC/TC and OC/EC. By means of a PCA analysis, five components were identified, including local soils and pavement erosion (63%), construction and demolition activities (13%), industrial emissions (6%), brake wear (5%) and tailpipe emissions (4%). These components accounted for 91% of the total variance. The results provide data to understand better one of the main sources of PM10 emissions in Bogota, such as road dust. These data will be useful to optimize environmental policies, and they may be used in future studies of human health and air quality modeling.

2005-2014 trends of PM10 source contributions in an industrialized area of southern Spain.

Particulate matter with a diameter of 10 µm or less (PM10) using receptor modelling was determined at an urban (La Linea, LL) and an industrial area (Puente Mayorga, PMY) in Southern Spain with samples collected during 2005-2014. The concentrations of PM10 had been decreasing at both sites in three distinctive periods: 1) the initial PM10 levels approached or exceeded the Spain and EU PM10 annual guidelines of 40 µg/m3 during 2005-2007 at LL and 2005-2009 at PMY; 2) then PM10 dropped by 25%-∼30 µg/m3 during 2008-2011 at LL and during 2010-2011 at PMY; 3) since 2012, the PM10 concentrations gradually decreased to <30 µg/m3. Chemical compositions of PM10 revealed the important contributions of water soluble ions (sulfate, nitrate, ammonium, and chloride), carbonaceous aerosols, and other major elements. These PM components generally showed a decrease trend, in accord with the trend of PM10 reduction. A PMF model identified seven sources to PM10 contributions. Secondary sulfate, soil/urban/construction dust, and secondary nitrate showed significantly decreasing trends with reduction of 40-60% comparing to the initial levels. The road traffic contribution decreased by 14% from the first to third period. However, sea salt, oil combustion, and industrial metallurgical process had relative stable contributions. These source contribution changes are reasonably governed by the PM emission abatement actions implemented during the past decade, as well as the financial crisis, that accounted for a significant decrease of PM pollution in Southern Spain. THE MAIN FINDING OF THE WORK: We identified that the mitigation efforts on industry, fossil fuel combustion, and urban transportation during the past decade were successful for air quality improvement in a highly industrialized area in Southern Spain.

Geochemical anomalies of household dust in an industrialized city (Huelva, SW Spain).

Geochemical anomalies of sulphide like elements (Cu, As and Cd) derived from the industrial activity have been identified in household dust of Huelva (SW Spain) using geochemical maps. Major and trace elements were analysed by ICP-OES and ICP-MS, respectively. Electron images of single particles were analysed by SEM-EDS in order to know their size, shape and composition. The geochemistry of the household dust has been compared to anomalies in deposition particles, PM10 and soils. A zonation has been observed: the eastern part of the city displays higher concentrations of sulphide like elements than the western part, supporting the origin of these elements related to the vicinity of industrial estates (Cu-smelter processes). Other domestic sources (e.g. wall painting) did not contain any geochemical anomalies related to sulphide like elements in household dust. Principal Component Analysis (PCA) was applied for grouping elements with similar sources, and reinforced the identification of a major industrial source in the eastern part. In this context, geochemical composition of household dust is considered as a fingerprint in order to identify industrial sources in the indoor air quality of Huelva.

Geochemical anomalies of toxic elements and arsenic speciation in airborne particles from Cu mining and smelting activities: influence on air quality.

A characterization of chemical composition and source contribution of PM10 in three representative environments of southwest Spain related to mining activities (mineral extraction, mining waste and Cu-smelting) has been performed. A study of geochemical anomalies was conducted in the samples collected at the three stations between July 2012 and October 2013. The influence of Cu-smelting processes was compared to other mining activities, where common tracers were identified. The Cu and As concentrations in the study area are higher than in other rural and urban stations of Spain, in which geochemical anomalies of As, Se, Bi, Cd, and Pb have been reported. The results of source contribution showed similar geochemical signatures in the industrial and mining factors. However, the contribution to PM10 is different according to the type of industrial activity. These results have been confirmed performing an arsenic speciation analysis of the PM10 samples, in which the mean extraction efficiency of arsenic depended on the origin of the samples. These finding indicate that the atmospheric particulate matter emitted from Cu-smelting has a high residence time in the atmosphere. This indicates that the Cu-smelter can impact areas of high ecological interest and considered as clean air.

Short-term effects of particulate matter constituents on daily hospitalizations and mortality in five South-European cities: results from the MED-PARTICLES project.

BACKGROUND: Few recent studies examined acute effects on health of individual chemical species in the particulate matter (PM) mixture, and most of them have been conducted in North America. Studies in Southern Europe are scarce. The aim of this study is to examine the relationship between particulate matter constituents and daily hospital admissions and mortality in five cities in Southern Europe. METHODS: The study included five cities in Southern Europe, three cities in Spain: Barcelona (2003-2010), Madrid (2007-2008) and Huelva (2003-2010); and two cities in Italy: Rome (2005-2007) and Bologna (2011-2013). A case-crossover design was used to link cardiovascular and respiratory hospital admissions and total, cardiovascular and respiratory mortality with a pre-defined list of 16 PM10 and PM2.5 constituents. Lags 0 to 2 were examined. City-specific results were combined by random-effects meta-analysis. RESULTS: Most of the elements studied, namely EC, SO4(2-), SiO2, Ca, Fe, Zn, Cu, Ti, Mn, V and Ni, showed increased percent changes in cardiovascular and/or respiratory hospitalizations, mainly at lags 0 and 1. The percent increase by one interquartile range (IQR) change ranged from 0.69% to 3.29%. After adjustment for total PM levels, only associations for Mn, Zn and Ni remained significant. For mortality, although positive associations were identified (Fe and Ti for total mortality; EC and Mg for cardiovascular mortality; and NO3(-) for respiratory mortality) the patterns were less clear. CONCLUSIONS: The associations found in this study reflect that several PM constituents, originating from different sources, may drive previously reported results between PM and hospital admissions in the Mediterranean area.

Contribution of mine wastes to atmospheric metal deposition in the surrounding area of an abandoned heavily polluted mining district (Rio Tinto mines, Spain).

The present study seeks to estimate the impact of abandoned mine wastes on the levels and chemical profile of total atmospheric deposition in one of the oldest and largest mining districts in Europe (Rio Tinto mines, Iberian Pyrite Belt), on the basis of a complete geochemical characterization of particulate matter samples periodically collected in five sampling stations located around the mining district between March 2009 and February 2011. The annual levels of total bulk deposition (soluble and insoluble fractions) registered in the Rio Tinto Mining District ranged between 18 and 43 g/m(2) depending on the distance from the sampling station with regard to the mine waste deposits. As a general pattern in the area, high mass levels of Zn and Cu were deposited in a range of 9-62 mg/m(2) not only in the insoluble but also in the soluble fraction. Other potentially toxic trace elements such as As, Sb, Ba, Pb, Sn and Bi showed greater deposition fluxes in the locations closest to the mine waste deposits. A principal component analysis with a Multilinear Regression Analysis certifies the presence of two common sources in the mining area: 1) a mineral factor composed mainly of elements derived from silicate minerals (Al, Ca, Sr, Ti, Li, Mg, Mn, K, Na and Fe), mixed with other anthropogenic species (NH4(+), SO4(2-), NO3(-)) within the village closest to the mine; and 2) a marine factor composed of Na, Cl, Mg, SO4(2-) and Sr. In addition, a mine waste factor made up of toxic elements (Cu, Zn, Ga, As, Sb, Ba, Pb, Sn, Cd and Bi) has been recognized in the sampling sites exposed to dust-bearing winds downwind of the mining area, suggesting that mine wastes are a relevant source of heavy-mineral particles with potentially adverse environmental effects to surrounding soils, plants and humans.

Impact of abandoned mine waste on atmospheric respirable particulate matter in the historic mining district of Rio Tinto (Iberian Pyrite Belt).

This work documents for the first time the levels and composition of atmospheric particulate matter in the historic mining district of Rio Tinto (Spain) to estimate the contribution and impact of resuspended particles from hazardous mine waste on air quality. The resuspended mine waste dust contributes notably (32%) to the total concentrations of toxic trace metals (Bi, As, Cu, Pb, Cd, Zn and Sb) into the atmosphere, with the consequent impact on public health.

Source apportionment of PM(10) and PM(2.5) at multiple sites in the strait of Gibraltar by PMF: impact of shipping emissions.

BACKGROUND: The impact of shipping emissions on urban agglomerations close to major ports and vessel routes is probably one of the lesser understood aspects of anthropogenic air pollution. Little research has been done providing a satisfactory comprehension of the relationship between primary pollutant emissions, secondary aerosols formation and resulting air quality. MATERIALS AND METHODS: In this study, multi-year (2003-2007) ambient speciated PM(10) and PM(2.5) data collected at four strategic sampling locations around the Bay of Algeciras (southern Spain), and positive matrix factorisation model were used to identify major PM sources with particular attention paid to the quantification of total shipping emissions. The impact of the emissions from both the harbour of Algeciras and vessel traffic at the Western entrance of Mediterranean Sea (Strait of Gibraltar) were quantified. Ambient levels of V, Ni, La and Ce were used as markers to estimate PM emitted by shipping. RESULTS AND DISCUSSION: Shipping emissions were characterised by La/Ce ratios between 0.6 and 0.8 and V/Ni ratios around 3 for both PM(10) and PM(2.5). In contrast, elevated La/Ce values (1-5) are attributable to emissions from refinery zeolitic fluid catalytic converter plant, and low average V/Ni values (around 1) result mainly from contamination from stainless steel plant emissions. The direct contribution from shipping in the Bay of Algeciras was estimated at 1.4-2.6 µg PM(10)/m(3) (3-7%) and 1.2-2.3 µg PM(2.5)/m(3) (5-10%). The total contribution from shipping (primary emissions + secondary sulphate aerosol formation) reached 4.7 µg PM(10)/m(3) (13%) and 4.1 µg PM(2.5)/m(3) (17%).

Arsenic speciation of atmospheric particulate matter (PM10) in an industrialised urban site in southwestern Spain.

An arsenic speciation study has been performed in PM10 samples collected on a fortnight basis in the city of Huelva (SW Spain) during 2001 and 2002. The arsenic species were extracted from the PM10 filters using a NH2OH x HCl solution and sonication, and determined by HPLC-HG-AFS. The mean bulk As concentration of the samples analyzed during 2001 and 2002 slightly exceed the mean annual 6 ng m(-3) target value proposed by the European Commission for 2013, arsenate [As(V)] being responsible for the high level of arsenic. The speciation analyses showed that As(V) was the main arsenic species found, followed by arsenite [As(III)] (mean 6.5 and 7.8 ng m(-3) for As(V), mean 1.2 and 2.1 ng m(-3) for As(III), in 2001 and 2002, respectively). The high levels of arsenic species found in PM10 in Huelva have a predominant industrial origin, such as the one from a nearby copper smelter, and do not present a seasonal pattern. The highest daily levels of arsenic species correspond to synoptic conditions in which the winds with S and SW components transport the contaminants from the main emission source. The frequent African dust outbreaks over Huelva may result in an increment of mass levels of PM10, but do not represent a significant input of arsenic in comparison to the anthropogenic source. The rural background levels of arsenic around Huelva are rather high, in comparison to other rural or urban areas in Spain, showing a relatively high atmosphere residence time of arsenic. This work shows the importance of arsenic speciation in studies of aerosol chemistry, due to the presence of arsenic species [As(III) and As(V)] with distinct toxicity.