Real-Time Measurements of Indoor-Outdoor Exchange of Gaseous and Particulate Atmospheric Pollutants in an Urban Area.

Air pollution is one of the greatest environmental risks to health, causing millions of deaths and deleterious health effects worldwide, especially in urban areas where citizens are exposed to high ambient levels of pollutants, also influencing indoor air quality (IAQ). Many sources of indoor air are fairly obvious and well known, but the contribution of outside sources to indoor air still leads to significant uncertainties, in particular the influence that environmental variables have on outdoor/indoor pollutant exchange mechanisms. This is a critical aspect to consider in IAQ studies. In this respect, an experimental study was performed at a public site such as a university classroom during a non-academic period in Madrid city. This includes two field campaigns, in summer (2021) and winter (2020), where instruments for measuring gases and particle air pollutants simultaneously measured outdoor and indoor real-time concentrations. This study aimed to investigate the dynamic variations in the indoor/outdoor (I/O) ratios in terms of ambient outdoor conditions (meteorology, turbulence and air quality) and indoor features (human presence or natural ventilation). The results show that the I/O ratio is pollutant-dependent. In this sense, the infiltration capacity is higher for gaseous compounds, and in the case of particles, it depends on the particle size, with a higher infiltration capacity for smaller particles (

Predicting the Olea pollen concentration with a machine learning algorithm ensemble.

Air pollution in large cities produces numerous diseases and even millions of deaths annually according to the World Health Organization. Pollen exposure is related to allergic diseases, which makes its prediction a valuable tool to assess the risk level to aeroallergens. However, airborne pollen concentrations are difficult to predict due to the inherent complexity of the relationships among both biotic and environmental variables. In this work, a stochastic approach based on supervised machine learning algorithms was performed to forecast the daily Olea pollen concentrations in the Community of Madrid, central Spain, from 1993 to 2018. Firstly, individual Light Gradient Boosting Machine (LightGBM) and artificial neural network (ANN) models were applied to predict the day of the year (DOY) when the peak of the pollen season occurs, resulting the estimated average peak date 149.1 ± 9.3 and 150.1 ± 10.8 DOY for LightGBM and ANN, respectively, close to the observed value (148.8 ± 9.8). Secondly, the daily pollen concentrations during the entire pollen season have been calculated using an ensemble of two-step GAM followed by LightGBM and ANN. The results of the prediction of daily pollen concentrations showed a coefficient of determination (r2) above 0.75 (goodness of the model following cross-validation). The predictors included in the ensemble models were meteorological variables, phenological metrics, specific site-characteristics, and preceding pollen concentrations. The models are state-of-the-art in machine learning and their potential has been shown to be used and deployed to understand and to predict the pollen risk levels during the main olive pollen season.

Comparison of modeling with empirical calculation of diffuse and fugitive methane emissions in a Spanish landfill.

One of the most significant environmental problems arising from landfills is the emission of methane into the atmosphere. In this study, methane emissions from a currently in-use Spanish landfill were modeled as well as being experimentally measured using a two-step method. The first step involved a qualitative walkover survey to detect where gases were being emitted on the surface of the landfill. The second stage comprised a quantitative analysis of these surface methane emissions at a selected number of points on the landfill surface using a specially designed flux chamber. The statistical analysis of the data obtained was based on the Sichel function and resulted in an average emission rate of 74.9 g·m-2·day-1, with 27.8 and 202.1 g·m-2·day-1 as the lower and upper limits of the 95% confidence interval, respectively. The total emission for the landfill, with an emitting surface of 335,000 m2, is 9.16 × 103 ton/yr. These values have been compared with those from three different models, with the model results being above the calculated mean emissions measured at the landfill, but below the upper confidence limit at 95%. Implications: One of the main environmental problems arising from the presence of landfills is the emission of biogas (which mainly contains methane and carbon dioxide) into the atmosphere. Several experimental methods as well as models have been developed to quantify these emissions. In this work, the authors have compared the results obtained using experimental measurements with those provided by some local and international models using the default parameters proposed. The results obtained from the experimental method are in accordance with those provided by the models, although the models could be slightly overestimating these emissions.

Application of a short term air quality action plan in Madrid (Spain) under a high-pollution episode - Part I: Diagnostic and analysis from observations.

Exceedances of NO2 hourly limit value (200 µg·m-3) imply the need to implement short term action plans to avoid adverse effects on human health in urban areas. The Madrid City Council applied the stage 3 of the NO2 protocol during a high-pollution episode under stable meteorological conditions on December 2016 for the first time. This included road traffic access restrictions to the city centre (50% of conventional private vehicles based on plate numbers). In this contribution we analyse different meteorological and air quality observations, including non-standard parameters (such as number of ultrafine particles and remote sensing techniques MAXDOAS) for a better understanding of the effectivity of short-term emission abatement measures under real conditions and to identify options to improve the NO2 protocol in the future. According to our results, the inversion base height computed from vertical temperature soundings is a meaningful index to anticipate very unfavourable conditions and trigger the actions included in the protocol. The analysis of the concentration levels of the main pollutants from the Madrid air quality monitoring network indicate that only stage 3 of the protocol had a significant effect on NO2 maximum concentrations. The restrictions applied may have prevented NO2 concentrations to further increase in the city centre (up to 15%) although pollution levels in the city outskirts, outside the area directly affected by the traffic restrictions, remained unchanged or may have been slightly increased. Nonetheless, further studies are needed to estimate more precisely the effect of the measures taken and to assess potential trade-offs. Our results suggest that emissions play an important role also under very strong stability conditions although drastic measures are needed to achieve a significant impact. This highlights the importance of an appropriate timing for short-term actions and the need of permanent abatement measures related to air quality plans and policies.

An integrated assessment of two decades of air pollution policy making in Spain: Impacts, costs and improvements.

This paper analyses the effects of policy making for air pollution abatement in Spain between 2000 and 2020 under an integrated assessment approach with the AERIS model for number of pollutants (NOx/NO2, PM10/PM2.5, O3, SO2, NH3 and VOC). The analysis of the effects of air pollution focused on different aspects: compliance with the European limit values of Directive 2008/50/EC for NO2 and PM10 for the Spanish air quality management areas; the evaluation of impacts caused by the deposition of atmospheric sulphur and nitrogen on ecosystems; the exceedance of critical levels of NO2 and SO2 in forest areas; the analysis of O3-induced crop damage for grapes, maize, potato, rice, tobacco, tomato, watermelon and wheat; health impacts caused by human exposure to O3 and PM2.5; and costs on society due to crop losses (O3), disability-related absence of work staff and damage to buildings and public property due to soot-related soiling (PM2.5). In general, air quality policy making has delivered improvements in air quality levels throughout Spain and has mitigated the severity of the impacts on ecosystems, health and vegetation in 2020 as target year. The findings of this work constitute an appropriate diagnosis for identifying improvement potentials for further mitigation for policy makers and stakeholders in Spain.

Carbon dioxide adsorption in chemically activated carbon from sewage sludge.

UNLABELLED: In this work, sewage sludge was used as precursor in the production of activated carbon by means of chemical activation with KOH and NaOH. The sludge-based activated carbons were investigated for their gaseous adsorption characteristics using CO2 as adsorbate. Although both chemicals were effective in the development of the adsorption capacity, the best results were obtained with solid NaOH (SBA(T16)). Adsorption results were modeled according to the Langmuir and Freundlich models, with resulting CO2 adsorption capacities about 56 mg/g. The SBA(T16) was characterized for its surface and pore characteristics using continuous volumetric nitrogen gas adsorption and mercury porosimetry. The results informed about the mesoporous character of the SBA(T16) (average pore diameter of 56.5 angstroms). The Brunauer-Emmett-Teller (BET) surface area of the SBA(T16) was low (179 m2/g) in comparison with a commercial activated carbon (Airpel 10; 1020 m2/g) and was mainly composed of mesopores and macropores. On the other hand, the SBA(T16) adsorption capacity was higher than that of Airpel 10, which can be explained by the formation of basic surface sites in the SBA(T16) where CO2 experienced chemisorption. According to these results, it can be concluded that the use of sewage-sludge-based activated carbons is a promising option for the capture of CO2. IMPLICATIONS: Adsorption methods are one of the current ways to reduce CO2 emissions. Taking this into account, sewage-sludge-based activated carbons were produced to study their CO2 adsorption capacity. Specifically, chemical activation with KOH and NaOH of previously pyrolyzed sewage sludge was carried out. The results obtained show that even with a low BET surface area, the adsorption capacity of these materials was comparable to that of a commercial activated carbon. As a consequence, the use of sewage-sludge-based activated carbons is a promising option for the capture of CO2 and an interesting application for this waste.

Health impact assessment of a reduction in ambient PM(2.5) levels in Spain.

BACKGROUND: Health effects linked to exposure to high air pollutant levels have been described in depth, and many recent epidemiologic studies have also consistently reported positive associations between exposure to air pollutants at low concentrations (particularly PM(2.5)) and adverse health outcomes. OBJECTIVE: To estimate the number of avoidable deaths associated with reducing PM(2.5) levels in Spain. MATERIALS AND METHODS: For exposure assessment, we used the US Environmental Protection Agency's Community Multiscale Air Quality model to simulate air pollution levels with a spatial resolution of 18×18 km(2). Two different scenarios were compared, namely, a baseline 2004 scenario based on Spain's National Emissions Inventory and a projected 2011 scenario in which a reduction in PM(2.5) was estimated on the basis of the benefits that might be attained if specific air quality policies were implemented. Using an 18×18 km(2) grid, air pollution data were estimated for the entire Iberian Peninsula, the Balearic Islands, Ceuta and Melilla. For these strata, crude all-cause mortality rates (ICD-10: A00-Y98) were then calculated for the over-30 and 25-74 age groups, taking into account the 2004 population figures corresponding to these same age groups, selected in accordance with the concentration-response functions (Pope CA 3rd, Burnett RT, Thun MJ, Calle EE, Krewski D, Ito K et al. Lung cancer, cardiopulmonary mortality, and long-term exposure to fine particulate air pollution. JAMA 2002; 287:1132-41; Laden F, Schwartz J, Speizer FE, Dockery DW. Reduction in fine particulate air pollution and mortality: extended follow-up of the Harvard Six Cities study. Am J Respir Crit Care Med 2006; 173:667-72.). Health impacts were assessed using the Environmental Benefits Mapping and Analysis Program (BenMAP). RESULTS: Air quality improvement was defined as an average annual reduction of 0.7 µg/m(3) in PM(2.5) levels. Using long-term health impact assessment analysis, we estimated that 1720 (673-2760) all-cause deaths (6 per 100,000 population) in the over-30 age group and 1450 (780-2108) all-cause deaths (5 per 100,000 population) in the 25-74 age group could be prevented annually. CONCLUSIONS: The results showed the potential benefits in general mortality which could be expected if pollution control policies were successfully implemented by 2011. A specifically adapted BenMAP could be used as a tool for estimating health impacts associated with changes in air pollution in Spain.