A novel application of thermogravimetry-mass spectrometry for polystyrene quantification in the PM10 and PM2.5 fractions of airborne microplastics.

Microplastics have appeared as emerging pollutants due to the diverse applications of plastics in today's world. Growing evidence points to the negative impacts that airborne microplastics have on human health, as they can enter the human body through respiration. Our aim was to quantify polystyrene airborne microplastics in smaller fractions, thoracic (PM10) and alveolar (PM2.5), as they have scarcely been studied. In this work, we proposed a methodology based on thermogravimetric analysis coupled with mass spectrometry that requires minimal sample preparation and does not limit particle size. We applied this methodology to quantify the airborne polystyrene in PM10 and PM2.5 fractions in mass units of microplastics per m3 of air in an urban and agricultural region during the summer of 2021. The mean concentrations of polystyrene found in the PM10 and PM2.5 fractions were 2.09 and 1.81 ng m-3, respectively. Therefore, the majority of airborne polystyrene microplastics are found in the alveolar fraction which, is associated with severe cardiopulmonary and respiratory diseases. According to air mass backward trajectories, it was noted that the main sources of these emerging pollutants could be related to local agricultural practices.

Cannabis, an emerging aeroallergen in southeastern Spain (Region of Murcia).

The evolution of the behaviour of the Cannabis taxon in the Region of Murcia, Spain, has been analysed (in the cities of Cartagena, 1993-2020; Murcia, 2010-2020; and Lorca, 2010-2020). An attempt has been made to establish the origin of Cannabis pollen in this region to determine whether it is transported locally or from long distances based on air mass origins. Cannabis is an herbaceous, normally dioecious and anemophilous plant, which produces large quantities of pollen grains. It has been widely used for fibre (hemp), bird food (hempseed), essential oils and narcotics. The origin of Cannabis pollen grains has been established by calculating back trajectories at the altitudes of: 750, 1500 and 2500 m above mean sea level (m amsl); 350, 500 and 650 m amsl; and 10, 100 and 250 m amsl, using the HYSPLIT model. Considering this data, 29 days of Cannabis pollen potentially originating in Africa were identified in Cartagena, 19 days in Murcia and 15 days in Lorca. Of the remaining days, the air mass back trajectories showed local or regional pollen origins. These were 83 days in Cartagena, 61 days in Murcia and 57 days in Lorca. The presence of Cannabis in the bioaerosol of the Region of Murcia is irregular, and it is considered a minority pollen type. However, from 2017 to 2020, concentrations increased, with a positive and significant trend of 90% in the Annual Pollen Integral. The pollen season can be defined between June and August. This increase in the concentration of Cannabis pollen grains during this period coincides with an increase in local transport, suggesting the possibility of increased Cannabis cultivation in the study area.

Phenological and seismological impacts on airborne pollen types: A case study of Olea pollen in the Region of Murcia, Mediterranean Spanish climate.

The rationale of this paper was to investigate whether earthquakes impact airborne pollen concentrations, considering some meteorological parameters. Atmospheric pollen concentrations in the Region of Murcia Aerobiological Network (Spain) were studied in relation to the occurrence of earthquakes of moment magnitude (up to Mw = 5.1) and intensity (intensity up to grade VII on the European Macroseismic Scale). In this study, a decade (2010-2019) was considered across the cities of the network. Earthquakes were detected in 12 out of 1535 days in the Olea Main Pollen Season in Cartagena, 49 out of 1481 days in the Olea Main Pollen Season in Lorca, and 39 out of 1441 days in the Olea Main Pollen Season in Murcia. The Olea pollen grains in this network were attributed to the species Olea europaea, i.e., the olive tree, a taxon that appears widely in the Mediterranean basin, in both cultivated and wild subspecies. Differences between the Olea concentration on days with and without earthquakes were only found in Lorca (Kruskal-Wallis: p-value = 0.026). The low frequency and intensity of the earthquakes explained these results. The most catastrophic earthquake felt in Lorca on May 11th, 2011 (IVII, Mw = 5.1, 9 casualties) did not result in clear variations in pollen concentrations, while meteorology (e.g., African Dust Outbreak) might have conditioned these pollen concentrations. The research should be broadened to other active seismological areas to reinforce the hypothesis of seismological impact on airborne pollen concentrations.

The effects of continentality, marine nature and the recirculation of air masses on pollen concentration: Olea in a Mediterranean coastal enclave.

Olea pollen concentrations have been studied in relation to the typology of air masses, pollen grain sources and marine nature during advections in a coastal enclave in the south-eastern Iberian Peninsula. Since Spain is the world's leading olive producer, and olive growing extends throughout the Mediterranean basin, this location is ideal for the study of long-distance transport events (LTD) during the main pollen season (MPS). The air masses were classified using the calculation of 48-h back trajectories at 250, 500 and 750 m above ground level using the HYSPLIT model. After that, the frequency of LDT events from Africa and Europe was found to be 8.7% of the MPS days. In contrast, regional air masses were found in 38.6% of the MPS days. This was reflected in pollen concentrations, with significantly higher concentrations (p-value <0.05) on days with regional air masses compared to days with European air masses. Regarding the source areas, the importance of nearby sources with intense olive cultivation was confirmed (i.e., Andalusia). This proximity was relevant beyond the attenuations observed when the advections acquired a marine nature as the air mass back trajectories moved over the sea (p-value <0.001). The review of air mass typologies, source areas and pollen concentrations resulted in establishing peak dates and the detection of LDT associated with these peak dates. Distortions in the typical path of each air mass explained alterations in pollen concentrations on consecutive days. The recirculation and loops of the air mass back trajectories varied the pollen load that every type of air mass could originally contain.

Impact of organic loading rate and reactor design on thermophilic anaerobic digestion of mixed supermarket waste.

A mixture of supermarket food waste from bakery, butchery, cooked meats and cheese, fishmonger, fruit, and vegetable sections was subjected to anaerobic digestion under thermophilic conditions (55 °C). Lab-scale induced bed reactors (IBR) and completely stirred tank reactors (CSTR) were operated at different organic loading rates (OLR), i.e., 3.0, 3.6 and 4.6 kg volatile solids (VS) per m3 of reactor and day. Regardless of the type of reactor, an OLR of 3.6 kg VS/m3·day was found to be the optimum, achieving up to 48.1% more methane production per kg of treated waste than for the other OLRs tested. In general, there were no statistically significant differences (p-value < 0.05) between IBR and CSTR performance at the same OLR tested. However, for the optimum OLR, the IBR achieved a mean methane production of 1.5 L CH4/Lreactor·day (426.7 L CH4/kg VS) and the highest VS removal (89.0%, on average). This reactor obtained 22.1% more CH4 yield than the analogous CSTR and the highest methane content in the biogas (66.9% CH4). Finally, the process was successfully tested under large-scale conditions (1.25 m3 IBR pilot-plant). The CH4 production and the biodegradation yield were in line with those obtained in the lab-scale IBR.

Analysis of airborne Olea pollen in Cartagena (Spain).

Olive cultivation is of great importance in Southern Europe but olive pollen is the leading cause of allergy in many regions where it is grown. The best preventive measure for allergic patients is to avoid exposure. Thus, aerobiological monitoring networks must supply realistic pollen classes for the different types of allergic pollen. Even though those pollen classes are defined, they do not necessarily fit local data. Altogether, they should use predictive models to assess flowering intensity in advance. In this study, the Olea pollen degree of exposure classes (OPDEC) are defined based on percentiles and a predictive model is suggested for Cartagena, Spain. 24year (1993-2016) Olea pollen counts series was used to characterize the Main Pollen Season (MPS). The aerobiological samples were processed following the methodology proposed by Hirst and developed by the Spanish Aerobiology Network. The aerobiological database was completed with the meteorological data supplied by AEMET (Spanish State Meteorological Agency). MPS evolution over time, and its relation with temperature and rainfall, has been analysed. The study showed an increase in MPS duration and the amount of Olea pollen grains collected both in MPS and the peak day. The OPDEC should fit local data to improve preventive measures. Based on the 24year series, the proposed OPDEC for Cartagena are: Low (≤10grains/m3), Medium (between 10 and 50grains/m3), High (between 51 and 100grains/m3) and Very High (≥100grains/m3). Olea pollen estimations in the MPS and in the peak day were obtained by means of three Regression Methods and climatic factors. The analysis reveals that the Bagging for Regression Trees (BRT) method is a good predictive alternative and stablishes the importance for each meteorological variable.

Impact of secondary inorganic aerosol and road traffic at a suburban air quality monitoring station.

PM10 from a suburban site in the northwest of Spain was assessed using data from chemical determinations, meteorological parameters, aerosol maps and five-day back trajectories of air masses. Temporal variations in the chemical composition of PM10 were subsequently related to stationary/mobile local sources and long-range transport stemming from Europe and North Africa. The presence of secondary inorganic species (sulphates, nitrates and ammonium) in airborne particulate matter constituted one of the main focuses of this study. These chemical species formed 16.5% of PM10 on average, in line with other suburban background sites in Europe. However, a maximum of 47.8% of PM10 were recorded after several days under the influence of European air masses. Furthermore, the highest values of these three chemical species coincided with episodes of poor air circulation and influxes of air masses from Europe. The relationship between SO42- and NH4+ (R2 = 0.57, p-value<0.01) was found to improve considerably in summer and spring (R2 = 0.88 and R2 = 0.87, respectively, p-value<0.01), whereas NO3- and NH4+ (R2 = 0.55, p-value<0.01) reproduced this pattern in winter (R2 = 0.91, p-value<0.01). The application of a receptor model to the dataset led to the identification of notable apportionments due to road traffic and other types of combustion processes. In fact, large amounts of particulate matter were released to the atmosphere during episodes of biomass burning in forest fires. On isolated days, combustion was estimated to contribute up to 21.0 µg PM/m3 (50.8% of PM10). The contribution from industrial processes to this source is also worth highlighting given the presence of Ni and Co in its profile. Furthermore, African dust outbreaks at the sampling site, characterised by an arc through the Atlantic Ocean, were usually associated with a higher concentration of Al2O3 in PM10. Results evidenced the relevance of stationary (i.e., steelworks and thermal power station) and mobile sources in the air quality at the suburban site under study, with important apportionments of particulate matter coming from road traffic and as consequence of releasing precursor gases of secondary particles to the atmosphere.

Inverted phase fermentation as a pretreatment for anaerobic digestion of cattle manure and sewage sludge.

The aim of this research study was to analyse the effect of applying inverted phase fermentation (IPF) prior to the anaerobic digestion of cattle manure and sewage sludge. IPF promotes the endogenous bacteria present in waste and hence enzymatic hydrolysis, producing a solid-liquid separation. The clarified bottom layer or liquid phase (LP, 70% volume in manure and 65% in sludge), and the thickened top layer or solid phase (SP, 30% volume in manure and 35% in sludge) were digested separately. Operating at 37 °C, the time needed to digest the LP from manure was shorter (10 days) than that needed to digest the corresponding SP or the untreated substrate (22 days in both cases). The time needed to digest the separated phases of sludge (LP: 2 days, SP: 15 days) was lower than that needed to digest manure. Biogas production rates for the manure after pretreatment were 0.5 L/L·day for the SP and 0.7 L/L·day for the LP, allowing higher OLR (4.5-4.8 gCOD/L·day) than when digesting untreated manure and increasing biogas production by 17%. IPF applied to sewage sludge led to a production of 1.8 L/L·day at an OLR of 6.2 gCOD/L·day for the SP and 2.0 L/L·day at 12.9 gCOD/L·day for the LP. Assuming a conventional OLR of 2-3 gCOD/L·day, the advantage of applying IPF to sewage sludge resides in the possibility of operating digesters at much higher OLR.

Traffic tracers in a suburban location in northern Spain: relationship between carbonaceous fraction and metals.

PM10 and black smoke were monitored at a suburban sampling station located in the northern Spanish city of Gijón. Thirty-two metals and total carbon (TC) (i.e., organic carbon (OC) and elemental carbon (EC)) were analyzed over a year. The study of air-mass origin based on 5-day back trajectories was carried out to assess its influence on the recovery data. Different strategies were implemented to infer the influence of traffic in the area. On average, TC accounted for 29 % of the PM10 fraction, with OC forming 77 % of this TC. The influence of traffic was clearly reduced during intense Atlantic advection episodes, when OC and EC decreased up to 0.39 and 0.22 µg C/m(3), respectively. In contrast, the highest values were reported during regional episodes, exceeding 10 µg C/m(3) of OC and 2 µg C/m(3) of EC. The correlation between EC and OC was found to notably improve when considering the days with high traffic flow (from R (2) = 0.46 to R (2) = 0.74). This pattern was also reproduced by black smoke and EC (from R (2) = 0.49 to R (2) = 0.59). Cu and Sn were found to be reliable traffic tracers given their high dependence on EC (R (2) = 0.82 and R (2) = 0.79, respectively). Nevertheless, Sn, Ba, and Sb showed a better correlation with Cu than EC, suggesting a common origin. In the case of Sn, R (2) improved from 0.79 to 0.91. The Cu/Sb ratio had a mean value of 6.6 which agrees with diagnostic criterions for brake wear particles. The relationships and ratios between EC, Cu, Sb, Sn, Ba, and Bi pointed out to non-exhaust emissions, playing a significant role in the chemical composition of PM10. Brake wear was presented as the most likely origin for Cu, Sb, and Sn.

Differences in soluble COD and ammonium when applying inverted phase fermentation to primary, secondary and mixed sludge.

Primary, secondary and mixed sludge were treated by inverted phase fermentation. This treatment results in solid-liquid separation of sludge after endogenous enzymatic hydrolysis (anaerobic conditions: 42°C, 48 hours). The soluble chemical oxygen demand (sCOD) was increased in the solid phase up to 1,800%, 21,300% and 260% in primary, secondary and mixed sludge, respectively. The corresponding increase in sCOD in the liquid phase accordingly reached values of up to 440%, 5,100% and 140%. Phase separation led to an enrichment of volatile solids in the solid phase (89-358% primary sludge, 80-102% secondary sludge and 29-133% mixed sludge). The NH4+-N values increased notably after the endogenous enzymatic hydrolysis itself. To investigate the short-term evolution following the treatment, the variation in sCOD, NH4+-N and solids was also monitored after keeping the hydrolysate at 37°C under anaerobic conditions for 24 hours. This stage showed no generalized pattern in terms of sCOD.

Differences in soluble COD and ammonium when applying ultrasound to primary, secondary and mixed sludge.

Ultrasound treatment is often applied to enhance the anaerobic digestion of sludge. Optimal conditions for organic matter solubilisation of primary, secondary and mixed sludge were assessed by implementing ultrasound disruption at different specific energies (from 3,500 to 21,000 kJ/kgTS). The variation in soluble chemical oxygen demand (sCOD) and ammonium nitrogen (NH4+-N) was monitored following the treatment, and after a subsequent fermentation (24 h, 37 °C). The effect of the treatment was clearly more pronounced in secondary sludge than in the other types of sludge. Relatively minimal values in solubility were found when applying ultrasound at different energies depending on the sludge (3,500-7,000 kJ/kgTS in primary sludge and 10,500-14,000 kJ/kgTS in secondary sludge). This minimal value was not so noticeable in mixed sludge. The addition of inoculum was not required after ultrasound disruption in order to perform the subsequent fermentation. After this final stage, no general pattern in terms of sCOD was observed. Increases and decreases were conditioned by the coverage of the ultrasound irradiation; NH4+-N values increased notably during the fermentation.

Effect of ultrasound pre-treatment in the anaerobic co-digestion of cattle manure with food waste and sludge.

This paper presents a study of the effect of applying ultrasound pre-treatment in the production of methane when co-digesting mixtures of cattle manure with food waste and sludge. A series of experiments were carried out under mesophilic and thermophilic conditions in continuously stirred-tank reactors containing 70% cattle manure, 20% food waste and 10% sewage sludge. Ultrasound pre-treatment allows operating at lower HRT, achieving higher volumetric methane yields: 0.85 L CH4/L day at 36°C and 0.82 CH4/L day at 55°C, when cattle manure and sewage sludge were sonicated. With respect to the non-sonicated waste, these values represent increases of up to 31% and 67% for mesophilic and thermophilic digestion, respectively.