A nationwide monitoring of atmospheric microplastic deposition.

Plastic production continues to increase every year, yet it is widely acknowledged that a significant portion of this material ends up in ecosystems as microplastics (MPs). Among all the environmental compartments affected by MPs, the atmosphere remains the least well-known. Here, we conducted a one-year simultaneous monitoring of atmospheric MPs deposition in ten urban areas, each with different population sizes, economic activities, and climates. The objective was to assess the role of the atmosphere in the fate of MPs by conducting a nationwide quantification of atmospheric MP deposition. To achieve this, we deployed collectors in ten different urban areas across continental Spain and the Canary Islands. We implemented a systematic sampling methodology with rigorous quality control/quality assurance, along with particle-oriented identification and quantification of anthropogenic particle deposition, which included MPs and industrially processed natural fibres. Among the sampled MPs, polyester fibres were the most abundant, followed by acrylic polymers, polypropylene, and alkyd resins. Their equivalent sizes ranged from 22 µm to 398 µm, with a median value of 71 µm. The particle size distribution of MPs showed fewer large particles than expected from a three-dimensional fractal fragmentation pattern, which was attributed to the higher mobility of small particles, especially fibres. The atmospheric deposition rate of MPs ranged from 5.6 to 78.6 MPs m-2 day-1, with the higher values observed in densely populated areas such as Barcelona and Madrid. Additionally, we detected natural polymers, mostly cellulosic fibres with evidence of industrial processing, with a deposition rate ranging from 6.4 to 58.6 particles m-2 day-1. There was a positive correlation was found between the population of the study area and the median of atmospheric MP deposition, supporting the hypothesis that urban areas act as sources of atmospheric MPs. Our study presents a systematic methodology for monitoring atmospheric MP deposition.

Characterization and removal efficiencies of microplastics discharged from sewage treatment plants in Southeast Spain.

Microplastics (MPs) are ubiquitous pollutants that can effectively harm different ecosystems. The information on the relative contribution of wastewater treatment plants (WWTPs) to the surrounding environment is important, in order to understand ecological health risks and implement measures to reduce their presence. This focus article presents a quantitative assessment on the relative concentration and types of MPs delivered from four WWTPs located at the Southeast of Spain. Samples from WWTPs were collected throughout a four-year period, comprising more than 1,200 L of analyzed wastewater and 3,215 microparticles isolated. Density extraction with 1.08 g/mL NaCl salt solution was systematically used as the main separation method, in a simple and reliable manner, and repeat extraction cycles did not play any significant impact on the study outcomes. The four WWTPs had removal efficiencies between 64.3% and 89.2% after primary, secondary, and tertiary treatment phases, without diurnal or daily variations. Advanced treatment methods displayed a lower removal rate for fibers than for particulate MPs. The abundance of MPs was always higher and with a lower mean size in wastewater samples collected in Autumn than for the rest of seasons. MPs dumped from WWTPs in large quantities into the environment are meant to be regarded as an important point source for aquatic and terrestrial environments.

A holistic approach on the impact of microplastic discharge from WWTPs to the neighboring environment in Southeast Spain.

The present study investigated the release of microplastics (MPs) from wastewater treatment plants (WWTPs) to the neighboring environment, including marine and coastal sediments, and fish. Here, we comprehensively investigated MP abundance in 34 samples of marine sediment, corresponding to 5,530.5 g of sediment (d.w.) collected at -8.0 m, -12.5 m, and -24.0 m, 69 samples of coastal sediment, accounting for 13,617.4 g (d.w.) from 17 different beaches from Mar Menor, and stomach and intestine of 17 fish samples of Sparus aurata, in the vicinity of Cartagena, a port city in Southeast Spain. The results showed that MPs were detected in all marine sediment samples, with an average abundance of 19.4 ± 2.4 items/kg (d.w.), in coastal sediments, with an average abundance of 52.5 ± 5.3 items/kg (d.w.), and fish samples, with an average of 8.2 ± 1.4 items per individual. The contribution of MPs from WWTPs to marine sediments is expected to be slow, as effluents were mostly dominated by fiber and film shapes, and by polymers less dense than seawater. There were no significant variations in the MP abundance of marine sediments after the atmospheric phenomenon named DANA, although a significant smaller MP size was reported, indicating a high mobility for tiny sizes. The same results were revealed for coastal sediment, although variations after DANA were statistically significant. Coastal sediment samples closer to WWTPs and agricultural fields with plastic mulching displayed higher MP concentrations, and an increase in the removal rate of MPs from WWTP effluents was negatively correlated with a decrease in MPs from fish collected. This study highlights the importance of sewage treatment plants in transporting MPs to the aquatic and terrestrial surrounding environment, which warrants further research on human health risks associated to MP pollution.

Occurrence and size distribution study of microplastics in household water from different cities in continental Spain and the Canary Islands.

The purpose of this study was to investigate the occurrence of microplastics (MPs) in drinking water in Spain by comparing tap water from different locations using common sampling and identification procedures. We sampled tap water from 24 points in 8 different locations from continental Spain and the Canary Islands by means of 25 µm opening size steel filters coupled to household connections. All particles were measured and spectroscopically characterized including not only MPs but also particles consisting of natural materials with evidence of industrial processing, such as dyed natural fibres, referred insofar as artificial particles (APs). The average concentration of MPs was 12.5 ± 4.9 MPs/m3 and that of anthropogenic particles 32.2 ± 12.5 APs/m3. The main synthetic polymers detected were polyamide, polyester, and polypropylene, with lower counts of other polymers including the biopolymer poly(lactic acid). Particle size and mass distributions were parameterized by means of power law distributions, which allowed performing estimations of the concentration of smaller particles provided the same scaling parameter of the power law applies. The calculated total mass concentration of the identified MPs was 45.5 ng/L. The observed size distribution of MPs allowed an estimation for the concentration of nanoplastics (< 1 µm) well below the ng/L range; higher concentrations are not consistent with scale invariant fractal fragmentation. Our findings showed that MPs in the drinking water sampled in this work do not represent a significant way of exposure to MPs and would probably pose a negligible risk for human health.

First evidence of microplastics isolated in European citizens' lower airway.

Microplastics (MPs) have been detected in all environmental locations, including the atmosphere. However, few studies have investigated the presence of airborne MPs in the human respiratory system. Our research purpose was to investigate these pollutants in the lower human airways of 44 adult European citizens, using bronchoalveolar lavage fluid (BALF) collection as a minimally invasive method, that enables the detection of these pollutants in living patients. We studied the relationship between the patients' life habits and physiological parameters, based on background information and medical and occupational history, and the concentration of MPs isolated from their respiratory systems. Our results indicate that most MPs were in the form of microfibers (MFs) (97.06%), with an average concentration of 9.18 ± 2.45 items/100 mL BALF, and only 5.88% (0.57 ± 0.27 items/100 mL BALF) were particulate MPs, without a significant relationship with environmental, physiological, or clinical factors. The average size was 1.73 ± 0.15 mm, with the longest dimension (9.96 mm) corresponding to a polyacrylic fiber. Taken together, the results demonstrated the occurrence of MPs in the lower human airway, although more studies are necessary to elucidate the negative effects these pollutants could induce in the human respiratory system and its associated diseases.

Weathering indices of microplastics along marine and coastal sediments from the harbor of Cartagena (Spain) and its adjoining urban beach.

Marine and coastal sediments from the harbor of Cartagena (Spain) and its adjoining beach were investigated regarding their microplastic burden. Fibers accounted for 47.62% and 61.66% in marine and coastal sediments, respectively, followed by films (31.43% and 18.76%) and fragments (20.95% and 18.65%). Polyvinyl (36.07%), polypropylene (21.31%), and polyethylene (18.03%) were isolated for marine sediments, and low-density polyethylene (40.71%), polypropylene (20.16%), and acrylate (11.37%) for coastal sediments. Highest concentrations were found in the deepest marine sediments (24.0 m) and in the furthest zone from the seashore for coastal sediments (18 m). Carbonyl index increased in the intermediate area (12.5 m) for marine sediments (0.51), whilst vinyl index was maximum for the deepest samples (1.94), reporting Norrish type I and II reactions, respectively. Coastal sediments collected close to the high tide line displayed the highest average values for both indices, 1.57 and 1.29, respectively, indicating a higher exposition to weathering variables.

Micro and Nano-Plastics in the Environment: Research Priorities for the Near Future.

Plastic litter dispersed in the different environmental compartments represents one of the most concerning problems associated with human activities. Specifically, plastic particles in the micro and nano size scale are ubiquitous and represent a threat to human health and the environment. In the last few decades, a huge amount of research has been devoted to evaluate several aspects of micro/nano-plastic contamination: origin and emissions, presence in different compartments, environmental fate, effects on human health and the environment, transfer in the food web and the role of associated chemicals and microorganisms. Nevertheless, despite the bulk of information produced, several knowledge gaps still exist. The objective of this paper is to highlight the most important of these knowledge gaps and to provide suggestions for the main research needs required to describe and understand the most controversial points to better orient the research efforts for the near future. Some of the major issues that need further efforts to improve our knowledge on the exposure, effects and risk of micro/nano-plastics are: harmonization of sampling procedures; development of more accurate, less expensive and less time-consuming analytical methods; assessment of degradation patterns and environmental fate of fragments; evaluating the capabilities for bioaccumulation and transfer to the food web; and evaluating the fate and the impact of chemicals and microorganisms associated with micro/nano-plastics. The major gaps in all sectors of our knowledge, from exposure to potentially harmful effects, refer to small size microplastics and, particularly, to the occurrence, fate and effects of nanoplastics.

Commercial Gilthead Seabream (Sparus aurata L.) from the Mar Menor Coastal Lagoon as Hotspots of Microplastic Accumulation in the Digestive System.

This paper presents the results on the presence and characterization of microplastics (MP) in the gastrointestinal tract of gilthead seabream (Sparus aurata L.), a species of commercial interest from the Mar Menor coastal lagoon in Southeast Spain. This is the first time that microplastic ingestion is recorded in any species from this semi-enclosed bay. Stomach and intestine from a total of 17 specimens captured by local fishermen were processed, and microplastic particles and fibers found in all of them were displayed. Overall, 40.32% (279/692) of total isolated microparticles proved to be microplastics; i.e., <5 mm, as identified by FTIR spectroscopy. The average value by fish was 20.11 ± 2.94 MP kg-1, corresponding to average concentrations of 3912.06 ± 791.24 and 1562.17 ± 402.04 MP by kg stomach and intestine, respectively. Four MP forms were isolated: fiber (71.68%), fragment (21.15%), film (6.81%), and microbead (0.36%), with sizes ranging from 91 µm to 5 mm, an average of 0.83 ± 0.04 mm, and no statistically significant differences between mean sizes in stomach and intestine samples (F-test = 0.004; p = 0.936). Nine polymer types were detected, although most of fibers remained unidentified because of their small size, the presence of polymer additives, or closely adhered pollutants despite the oxidizing digestion carried out to eliminate organic matter. No significant correlation was found between main biological parameters and ingested microplastics, and high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene polypropylene (PEP), and polyvinyl (PV) were identified as the most abundant polymers. The average microplastic ingestion in this study area was higher than those reported in most studies within the Mediterranean Sea, and closely related to microplastic pollution in the surrounding area, although with a predominance of fiber form mainly due to fishery activities.

Membrane bioreactor and rapid sand filtration for the removal of microplastics in an urban wastewater treatment plant.

This paper discusses about the role of two different wastewater treatment technologies in the abatement of microplastics (MPs) from the final effluent of an urban wastewater treatment plant (WWTP); i.e., membrane bioreactor technology (MBR) and rapid sand filtration (RSF). For this purpose, a WWTP with these two technologies was monitored for 18 months. The average microplastic concentration was 4.40 ± 1.01 MP L-1 for the influent, 0.92 ± 0.21 MP L-1 for MBR, and 1.08 ± 0.28 MP L-1 for RSF, without statistically significant differences for MPs removal between both technologies (F-test = 0.195, p = 0.661). The main MP forms isolated in our study were fibers (1.34 ± 0.23 items L-1), followed by films (0.59 ± 0.24 items L-1), fragments (0.20 ± 0.09 items L-1), and beads (0.02 ± 0.01 items L-1). All of them probed to be statistically significant reduced after both technologies, but without statistically significant differences between them. The MP removal efficiency was 79.01% and 75.49% for MBR and RSF, respectively, although higher for microplastic particulate forms (MPPs), 98.83% and 95.53%, than for fibers, 57.65% and 53.83% for MBR and RSF, respectively, displaying a selective removal of particulate forms against microfibers. Fourteen different plastic polymers were identified in the influent, only persisting low-density polyethylene (LDPE), nylon (NYL), and polyvinyl (PV) in RSF effluent, and melamine (MUF) after MBR treatment. The MP size ranged from 210 µm, corresponding to NYL fragment form in the influent, to 6.3 mm, corresponding to a red microfiber also from the influent. The maximum MP average size significantly decreased from MBR (1.39 ± 0.15 mm), to RSF (1.15 ± 0.08 mm) and influent (1.05 ± 0.05 mm) (F-test = 4.014, p = 0.019), exhibiting the fiber selection carried out by these advanced technologies for wastewater treatment.

Microplastics in an urban wastewater treatment plant: The influence of physicochemical parameters and environmental factors.

This paper presents the abundance, concentration and variability of microplastics (MP) in an urban wastewater treatment plant (WWTP), according to different water parameters and environmental factors, their possible sources and removal efficiency. A total of 352.6 L of wastewater from four stages of the treatment process were processed following a standardized extraction protocol by density separation, trinocular microscopic identification and polymeric analysis by Fourier transform infrared spectroscopy. MP comprised a 46.6% of total microlitter, with a statistically significant removal of 90.3% in the final effluent of the WWTP. Five different shapes were isolated; i.e. fragment, film, bead, fiber, and foam. The most prominent MP forms in the final effluent were fragments and fibers, with the most common size class being 400-600 µm. Seventeen different polymer families were identified, with low-density polyethylene being the most prevalent one (52.4%) in a film form (27.7%), mostly from agriculture greenhouses near the sewage plant and single plastic bags (it is noted that only a year ago consumers are charged for them in Spain). Influent wastewater with high concentrations of suspended solids proved to have a low MP burden with a larger MP size, possibly due to a hetero-aggregation with particulate matter. Agglomeration of polystyrene and polyethylene terephthalate with organic material is also suggested, both with surface energies higher than 25 mN m-1 enough for a high biofouling rate. The sewage plant cushions sharp-point microplastic concentrations during the warm season, allowing a stable performance of the WWTP.

Abundance, morphology and chemical composition of microplastics in sand and sediments from a protected coastal area: The Mar Menor lagoon (SE Spain).

This paper presents the abundance and ubiquitous presence of microplastics in a protected coastal zone located in the southeast of Spain: The Mar Menor lagoon, an important tourist destination in this region. Seventeen sampling sites, corresponding to both intertidal and backshore points, were collected during winter 2017 and 2018, being situated in different protected areas according to international, European and Spanish environmental policies. The main objectives of the study were to examine microplastics in both protected and non-protected areas, and to test the importance of local activities on their presence. Northwest samples reported higher average microplastic concentrations than samples collected in the southeastern part of the coastal lagoon, likely due to the extensive use of sludge from wastewater treatment plants besides the fragmentation of low density polyethylene from plastic greenhouses, being microplastic films also higher for northwest than for southeast samples. Moreover, large inter-site differences observed in microplastic concentrations also demonstrated that local activities, mainly tourism and fishery, may play an important role as microplastic sources. The extensive amount of 17 different polymer types identified in this paper, much higher than most reported in similar studies, together with the variety of colors of microplastics most of them in a fragmented form (59.4%) and mainly detected in urban beaches, should be related to the geographical situation of this coastal lagoon, together with enormous environmental passives accumulated over the past 50 years. Only polyvinyl ester resins proved to be statistically higher in non-protected than in protected zones, probably related to their use in manufacturing boat hulls, although sources and pathways for microplastics are always difficult to assess. Measures to avoid microplastic pollution should be taken through educational programs, with also a clear commitment from plastic producers and transformers.

Phytostabilization of polymetallic contaminated soil using Medicago sativa L. in combination with powdered marble: Sustainable rehabilitation.

This study uses an ecotoxicology approach to evaluate the effectiveness of combining powdered marble as an amendment, with phytostabilization by Medicago sativa L. on the neutralization of acidic mine tailings, and the stabilization of heavy metals. The mine tailings were collected from an abandoned polymetallic mine in Southern Morocco, and mixed with powdered marble as the following proportions, 25%, 50%, and 75%. Laboratory immobilization/stabilization tests showed that the application of powdered marble in the treatments led to a significant increase in pH, and significant reductions of Cu, Zn (99%), Pb (98%), and Fe (45%). Greenhouse experiments showed that plant growth in all treatments was significantly (p ≤ 0.05) less than growth in agricultural soil. Plant growth significantly (p ≤ 0.05) decreased as the proportion of powdered marble increased. The concentration of metals in plant roots were significantly (p ≤ 0.05) higher than those of shoots. Combining immobilization by powdered marble with phytostabilization by M. sativa L. could represent a viable method of rehabilitating acidic polymetallic mine tailings.

Principal factor and hierarchical cluster analyses for the performance assessment of an urban wastewater treatment plant in the Southeast of Spain.

Process performance and operation of wastewater treatment plants (WWTP) are carried out to ensure their compliance with legislative requirements imposed by European Union. Because a high amount of variables are daily measured, a coherent and structured approach of such a system is required to understand its inherent behavior and performance efficiency. In this sense, both principal factor analysis (PFA) and hierarchical cluster analysis (HCA) are multivariate techniques that have been widely applied to extract and structure information for different purposes. In this paper, both statistical tools are applied in an urban WWTP situated in the Southeast of Spain, a zone with special characteristics related to the geochemical background composition of water and an important use of fertilizers. Four main factors were extracted in association with nutrients, the ionic component, the organic load to the WWTP, and the efficiency of the whole process. HCA allowed distinguish between influent and effluent parameters, although a deeper examination resulted in a dendrogram with groupings similar to those previously reported for PFA.

The use of native and protonated grapefruit biomass (Citrus paradisi L.) for cadmium(II) biosorption: equilibrium and kinetic modelling.

This paper describes the use of native and protonated grapefruit biomass, a by-product of the food industry, as an effective and low-cost biosorbent for cadmium removal from aqueous solutions. The biomass composition was analysed by high-performance liquid chromatography, scanning electron microscopy coupled with energy-dispersive X-ray analysis and Fourier transform infrared spectroscopy, showing that hydroxyl and carboxylic groups were the main functional groups implicated in Cd(II) biosorption. The effect of different parameters affecting the biosorption process were studied. The optimum removal of cadmium ions was at pH 4.5. Elution of alkaline-earth ions proved to be related with cadmium uptake, aiming for an ion-exchange mechanism. Protonated biomass showed higher adsorption affinity, binding strength and irreversibility for cadmium than native grapefruit, although the optimum metal uptake and high reaction rate was for the native form of grapefruit. Biosorption experimental data fitted Freundlich > Langmuir > Temkin equilibrium adsorption models. Data for both types of biomass were better fitted by a pseudo-second-order kinetic model, with an excellent correlation between calculated and experimental values. Because of these experimental results, and taking into account that both types of biomass displayed an exothermic and spontaneous physical adsorption process, native grapefruit can be proposed in further experiments as a cheap, effective, low-cost and environmentally friendly natural sorbent for the removal of cadmium from industrial wastewater effluents, avoiding chemical pretreatment before its use.

Ecotoxicological screening of reclaimed disinfected wastewater by Vibrio fischeri bioassay after a chlorination-dechlorination process.

It is well known that different substances can react with chlorine in a water disinfection process to produce disinfection by-products (DBPs). Some of these substances have proven to be carcinogenic in humans and animals. Because it is not possible to detect all DBPs produced in chlorinated wastewater, toxicity tests have been proposed as a useful tool for screening toxic chemicals in treated wastewater. In this study, the Microtox bioassay with Vibrio fischeri was used to evaluate the formation of toxic by-products in wastewater, after a chlorination-dechlorination disinfection treatment. All the variables were found to be normally distributed, so analysis of variance could be directly applied without transformation of variables. Significant correlations were obtained between toxicity values and total carbon, total inorganic carbon, total nitrogen, chlorine, and pH. In contrast, total organic carbon, chemical oxygen demand, electrical conductivity and turbidity had no effect on toxicity formation. Toxicity increased with the Cl2:NH4+ ratio at a higher chlorine concentration released from combined chlorine. Regression models provided a good fit for effective concentration (EC50) as a function of total carbon and total nitrogen, after 5, 10, and 15 min of exposure. These models had greater multiple determination coefficients than previously reported for similar studies, without autocorrelation in the residuals as indicated by the Durbin-Watson statistic test. The measured and predicted ecotoxicity values were strongly correlated.