Effect of particle size on the transport of polystyrene micro- and nanoplastic particles through quartz sand under unsaturated conditions.

Micro- and nanoplastics (MNPs) are contaminants of emerging concern recently found in soil ecosystems. Their presence in terrestrial environments and their migration to aquatic environments may become a risk for the health of ecosystems and, through them, of humans. Understanding the interaction between particle properties and physicochemical and hydrodynamic factors is crucial to evaluate their fate and their potential infiltration towards groundwater. This study investigates the impact of particle size on MNPs transport through sand under unsaturated conditions. Infiltration column experiments with polystyrene MNPs ranging from 120 to 10,000 nm were conducted and supported by numerical modelling to derive reactive transport parameters. Results show a significant effect of particle size on the transport of MNPs, with higher recovery values observed for smaller particles (120 nm; 95.11%) compared to larger particles (1000 nm; 71.44%). No breakthrough was observed for 10,000 nm particles, indicating a complete retention within the quartz sand matrix. DLVO theory confirmed the dominance of electrostatic repulsive forces between MNPs and sand grains, suggesting an unfavourable environment for MNPs to adhere to quartz sand. Consequently, particle retention in the sand matrix occurs predominantly by physical processes. Equilibrium sorption modelling reveals that larger particles (1000 nm) tend to be immobilized in small pores throats due to straining, resulting in lower recoveries. When they are not trapped, particles tend to travel faster through preferential flows due to a size exclusion effect, evidenced by shorter arrival times at the column outlet compared to tracers. These findings highlight the influence of particle size on the transport and retention of MNPs in quartz sand under unsaturated conditions and contribute to a better understanding of their transport dynamics and environmental fate.

Soil amendments and water management to improve attenuation and recovery of wastewater originated nutrients through a vegetation filter.

Vegetation filters (VFs) are on-site wastewater (WW) treatments that can be considered as a nature-based solution (NbS). They are green infrastructures that provide several environmental benefits such as non-potable water reuse, contamination reduction, biomass production, landscaping improvements and CO2 fixation, among others. However, nutrient leaching, especially nitrate, partially exists. To overcome this limitation, operational parameters related to the irrigation water management and soil amendments were tested in a real system receiving WW from an office building operated along 4 years. The attenuation of N is improved (up to 83%) in the vadose zone by boosting biodegradation. Lower hydraulic loads and more frequent irrigation events using drippers and the incorporation of woodchips as a layer above the topsoil promote denitrification processes. Changes in organic carbon characteristics also confirm that biodegradation is enhanced. P attenuation is a result of abiotic processes, mainly driven by chemical equilibriums between the liquid and the sorbed and/or precipitated phase and, when uncontrolled changes in the WW quality occurs, removal efficiency is negatively affected. However, only 10% of the samples collected at 45 cm depth present concentrations above 2 mg/L. The woodchips application does not seem to ameliorate P removal regardless of the application method. The implemented measures allow higher soil water content, infiltration and groundwater recharge and prevents aquifer contamination.

Fate and effects of an environmentally relevant mixture of microplastics in simple freshwater microcosms.

Most studies assessing the effects of microplastics (MPs) on freshwater ecosystems use reference materials of a certain size, shape, and polymer type. However, in the environment, aquatic organisms are exposed to a mixture of different polymers with different sizes and shapes, resulting in different bioaccessible fractions and effects. This study assesses the fate and effects of an environmentally relevant mixture of high-density polyethylene (HDPE) fragments, polypropylene (PP) fragments, and polyester (PES) fibres in indoor freshwater microcosms over 28 days. The MP mixture contained common polymers found in freshwater ecosystems, had a size range between 50 and 3887 µm, and was artificially aged using a mercury lamp. The invertebrate species included in the microcosms, Lymnea stagnalis (snail) and Lumbriculus variegatus (worm), were exposed to four MP concentrations: 0.01, 0.05, 0.1 and 1 % of sediment dry weight. MPs fate was assessed by performing a balance of the MPs in the surface water, water column, and sediment after a stabilization period and at the end of the experiment. Sedimentation rates per day were calculated (2.13 % for PES, 1.46 % for HDPE, 1.87 % for PP). The maximum size of MPs taken up by the two species was determined and compared to the added mixture and their mouth size. The size range taken up by L. variegatus was smaller than L. stagnalis and significantly different from the size range in the added mixture. The No Observed Effect Concentrations (NOECs) for the reproduction factor of L. variegatus and the number of egg clutches produced by L. stagnalis were 0.01 % and 0.1 % sediment dry weight, respectively. The EC10 and EC50 for the same endpoint for L. stagnalis were 0.25 % and 0.52 %, respectively. This study shows that current MP exposure levels in freshwater sediments can result in sub-lethal effects on aquatic organisms, highlighting the importance of testing MP mixtures.

Amended Vegetation Filters as Nature-Based Solutions for the Treatment of Pharmaceuticals: Infiltration Experiments Coupled to Reactive Transport Modelling.

In small populations and scattered communities, wastewater treatment through vegetation filters (VFs), a nature-based solution, has proved to be feasible, especially for nutrient and organic matter removal. However, the presence of pharmaceuticals in wastewater and their potential to infiltrate through the vadose zone and reach groundwater is a drawback in the evaluation of VF performances. Soil amended with readily labile carbon sources, such as woodchips, enhances microbial activity and sorption processes, which could improve pharmaceutical attenuation in VFs. The present study aims to assess if woodchip amendments to a VF's soil are able to abate concentrations of selected pharmaceuticals in the infiltrating water by quantitatively describing the occurring processes through reactive transport modelling. Thus, a column experiment using soil collected from an operating VF and poplar woodchips was conducted, alongside a column containing only soil used as reference. The pharmaceuticals acetaminophen, naproxen, atenolol, caffeine, carbamazepine, ketoprofen and sulfamethoxazole were applied daily to the column inlet, mimicking a real irrigation pattern and periodically measured in the effluent. Ketoprofen was the only injected pharmaceutical that reached the column outlet of both systems within the experimental timeframe. The absence of acetaminophen, atenolol, caffeine, carbamazepine, naproxen and sulfamethoxazole in both column outlets indicates that they were attenuated even without woodchips. However, the presence of 10,11-epoxy carbamazepine and atenolol acid as transformation products (TPs) suggests that incomplete degradation also occurs and that the effect of the amendment on the infiltration of TPs is compound-specific. Modelling allowed us to generate breakthrough curves of ketoprofen in both columns and to obtain transport parameters during infiltration. Woodchip-amended columns exhibited Kd and µw values from one to two orders of magnitude higher compared to soil column. This augmentation of sorption and biodegradation processes significantly enhanced the removal of ketoprofen to over 96%.

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.

Evaluation of contaminants of emerging concern attenuation through a vegetation filter managed using different operating conditions.

In wastewater treatment using Vegetation Filters (VFs), natural processes reduce contaminants present in water although some of them can reach the environment. In this study, 39 contaminants of emerging concern (CECs) are evaluated in a pilot VF under different operating conditions during almost four years. The use of woodchip amendments and the change from surface irrigation through furrows to drip irrigation (and from weekly to daily water application) provide CEC concentration reductions in the water infiltrating through the vadose zone. Biodegradation is the main process taking place and has been favoured mainly by woodchip soil amendments and the increased residence. Median attenuation percentages of the CECs most frequently detected with highest concentrations in applied wastewater vary between 52% and 100% at the end of the study (at 45 cm depth). Among targeted CECs, caffeine, and its transformation product paraxanthine are the most attenuated. Flecainide and venlafaxine show a persistent behaviour. However, their leaching concentrations are very low (< 31 ng/L). Concerning the underlying aquifer, the groundwater quality in terms of CEC concentrations is conditioned by the surrounding area rather than the operation of the VF. Levels in groundwater are always below those in wastewater and infiltrating water.

Untargeted metabolomic analysis to explore the impact of soil amendments in a non-conventional wastewater treatment.

As non-conventional wastewater treatment, vegetation filters make the most of the natural attenuation processes that occur in soil to remove contaminants, while providing several environmental benefits. However, this practice may introduce contaminants of emerging concern (CECs) and their transformation products (TPs) into the environment. A potential improvement to the system was tested using column experiments containing soil (S) and soil amended with woodchips (SW) or biochar (SB) irrigated with synthetic wastewater that included 11 selected CECs. This study evaluated: i) known CECs attenuation and ii) unknown metabolites formation. Known CECs attenuation was assessed by total mass balance by considering both water and soil media. An untargeted metabolomic strategy was developed to assess the formation of unknown metabolites and to identify them in water samples. The results indicated that SB enhanced CECs attenuation and led to the formation of fewer metabolites. Sorption and biodegradation processes were favored by the bigger surface area of particles in SB column, especially for compounds with negative charges. Incorporating woodchips into soil shortened retention times in the column, which reduced attenuation phenomena and resulted in the formation of significantly more metabolites. Incomplete biodegradation reactions, fostered by shorter retention times in SW column could mainly explain these results.

Analytical method to monitor contaminants of emerging concern in water and soil samples from a non-conventional wastewater treatment system.

Nonconventional wastewater treatments, such as vegetation filters (VFs), are propitious systems to attenuate contaminants of emerging concern (CECs) in small municipalities. The development of standardised multiresidue and multimatrix methods suitable for measuring a reliable number of CEC in environmental samples is crucial for monitoring infiltrating concentrations and for ensuring these systems' treatment capacity. The objective of this study is to develop and validate an analytical method for the simultaneous determination of CECs, including transformation products (TPs), with diverse physico-chemical properties, in environmental samples. The optimised method is based on sample clean-up and preconcentration by solid-phase extraction (SPE), followed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). The method is able to detect and quantify 40 target CECs, including pharmaceuticals of different classes (analgesics, antibiotics, antihypertensives, lipid regulators, anticonvulsants, antidepressants, antiarrhythmics, beta-blockers, amongst others), hormones and lifestyle products with good reproducibility (variations below 23%), in different water matrices, and 28 CECs, in soil samples. Acceptable recoveries (65-120%) were obtained for most of the CECs in all the matrices. However in the soil samples, as complexity required a prior extraction treatment, the recovery of some analytes was affected, which reduced the number of target CECs. The achieved methodological quantification limits (0.05-5 ng/L and 0.04-1.1 ng/g levels for the water and the soil matrices, respectively) were reasonably low for most CECs. The proposed method was successfully applied to monitor CECs in a VF. The CECs detected at higher concentrations are some of the world's most widely used products (e.g. acetaminophen or caffeine and its main TP, paraxanthine). The results showed an almost 70% reduction in CEC concentrations during infiltration. The groundwater data indicated that the VF treatment operation did not affect the underlying aquifer (Cmax found in GW <1 µg/L).

Pharmaceutical and transformation products during unplanned water reuse: Insights into natural attenuation, plant uptake and human health impact under field conditions.

In urban and periurban areas, agricultural soils are often irrigated with surface water containing a complex mixture of contaminants due to wastewater treatment plant (WWTP) effluent discharges. The unplanned water reuse of these resources for crop irrigation can represent a pathway for contaminant propagation and a potential health risk due to their introduction in the food chain. The aim of this study is to provide data about the magnitude of attenuation processes and plant uptake, allowing for a reliable assessment of contaminant transfer among compartments and of the human health risk derived from unplanned water reuse activities. Target compounds are 25 pharmaceuticals, including transformation products (TPs). The field site is an agricultural parcel where maize is irrigated by a gravity-fed surface system supplied by the Jarama river, a water course strongly impacted by WWTP effluents. Throughout the 3-month irrigation period, irrigation water and water infiltrating through the vadose zone were sampled. The agricultural soil was collected before and after the irrigation campaign, and maize was sampled before harvesting. All selected compounds are detected in irrigation water (up to 12,867 ng L-1). Metformin, two metamizole TPs and valsartan occur with the highest concentrations. For most pharmaceuticals, results demonstrate a high natural attenuation during soil infiltration (>60%). However, leached concentrations of some compounds can be still at concern level (>400 ng L-1). A persistent behavior is observed for carbamazepine, carbamazepine epoxide and sulfamethoxazole. Pharmaceutical soil contents are in the order of ng g-1 and positively ionized compounds accumulate more effectively. Results also indicate the presence of a constant pool of drugs in soils. Only neutral and cationic pharmaceuticals are taken up in maize tissues, mainly in the roots. There is an insignificant threat to human health derived from maize consumption however, additional toxicity tests are recommended for 4AAA and acetaminophen.

Sustainable soil amendments to improve nature-based solutions for wastewater treatment and resource recovery.

Vegetation Filters (VFs) can be a sustainable solution to treat wastewater and to recover resources such as nutrients, water and biomass from small municipalities and isolated dwellings. However, under certain conditions, the leakage of nutrients, especially of nitrate, can represent a limitation. The addition of two sustainable soil amendments, woodchips and biochar, has been tested as a strategy to improve nutrient attenuation in VFs increasing sorption sites and microbial activity. To this end, unsaturated infiltration and batch experiments have been carried out at laboratory scale. The systems for infiltration experiments contain natural soil, natural soil amended with woodchips and natural soil amended with biochar. To determine the sorption capacity of NH4+, batch tests were performed using an amendment/SWW ratio of 1:20 and an NH4+ initial concentration ranging from 30 to 600 mg L-1. Results from the infiltration experiments show a high attenuation (~95%) of total phosphorous (TP) independently of the amendments. Different behaviour is observed for total nitrogen (TN). The removal of this species is obtained only in the soil amended with woodchips (>85%) whereas the natural soil alone and the soil with biochar have no impact on TN attenuation. In these two porous media, all the NH4+ input concentration is transformed to NO3- that infiltrates without further reactions. According to batch experiment results, the potential role of biochar in the nutrient attenuation is limited to sorption processes (Kd (NH4+) = 21.37-193.18 L kg-1). Woodchips act primarily as a labile source of carbon promoting biodegradation, being more effective for nutrient attenuation than the sorption capacity of biochar.

Pharmaceuticals and trace metals in the surface water used for crop irrigation: Risk to health or natural attenuation?

The use of surface water impacted by wastewater treatment plant (WWTP) effluents for crop irrigation is a form of unplanned water reuse. Natural attenuation processes can buffer contamination spreading. However, this practice can promote the exposure of crops to contaminants of emerging concern, such as pharmaceuticals, trace metals (TMs) and metalloids, posing a risk to health. This research aimed to evaluate the presence of 50 pharmaceuticals, some transformation products, 7 TMs and a metalloid in the water-sediment-soil-plant system, and their potential to be bioaccumulated into edible parts of plants, as a result of the unplanned water reuse. The study site consists of an extensive agricultural land downstream Madrid city (Spain) where surface water, strongly impacted by WWTP effluents, is applied through gravity-based systems to cultivate mainly maize. Sampling campaigns were conducted to collect WWTP effluent, surface and irrigation water, river sediments, agricultural soils and maize fruits. Results demonstrate the ubiquitous presence of several pharmaceuticals. The concentration pattern in irrigation water did not resemble the pattern of contents in soils and plants. The pharmaceuticals included in the EU surface water watch lists were quantified in the lowest concentration range (macrolide antibiotics, ciprofloxacin) or were not detected (most of the hormones). Therefore, hormones do not represent an emerging risk in our scenario. The TMs and the metalloid in water and agricultural soils should not arise any concern. Whereas, their presence in the river sediments may have an adverse impact on aquatic ecosystems. Only acetaminophen, ibuprofen, carbamazepine, nicotine, Zn, Cu and Ni were quantified in corn grains. Calculated parameters to assess bioaccumulation and health risk indicate that neither pharmaceuticals nor TMs pose a threat to human health due to consumption of maize cultivated in the area. Results highlight the need to include different environmental matrices when assessing contaminant fate under real field-scale conditions.

Clinoptilolite and palygorskite as sorbents of neutral emerging organic contaminants in treated wastewater: Sorption-desorption studies.

Water reuse for aquifer recharge could be an important route for the introduction of emerging organic contaminants (EOCs) into the environment. The installation of a Horizontal Permeable Reactive Barrier (H-PRB) could constitute a tertiary treatment process to remove EOCs from treated domestic wastewater prior to recharge activities. The sorption-desorption behaviour of six neutral EOCs present in treated domestic wastewater (acetaminophen, caffeine, carbamazepine, cotinine, 4-acetamidoantipyrine (4-AAA) and 4-formylaminoantipyrine (4-FAA)) has been evaluated. Clinoptilolite and palygorskite have been studied as sorbents to be installed in the H-PRB. Batch tests were carried out using an EOC initial concentration ranging from 5 to 100 µg L-1. Apart from acetaminophen and caffeine, both materials showed a limited sorption capacity of neutral EOCs (Kd = 0.63-5.42 L kg-1). In general, the experimental results show that EOCs exhibit a higher sorption affinity for clinoptilolite than for palygorskite. With the exception of carbamazepine, the sorption of the compounds occurs mainly by interactions with mineral surfaces as indicated by the comparison of the partition coefficients into organic matter and into mineral surfaces. According to the molecular geometry of the compounds and the sorption sequences observed, it appears that the dimensions of the organic molecules play a key role in the sorption process. All the studied EOCs exhibit irreversible sorption and sorption-desorption hysteresis.

Investigating natural attenuation of pharmaceuticals through unsaturated column tests.

The growing consumption of pharmaceuticals together with their incomplete removal in wastewater treatment plants (WWTPs) implies the occurrence of these compounds in natural water resources. To investigate the natural attenuation of selected pharmaceuticals (caffeine, acetaminophen, sulfamethoxazole, naproxen and carbamazepine) during vadose zone infiltration, unsaturated column (L 26.67 cm, Ø 7.62 cm) experiments, filled with a sandy-loamy soil, were performed using two input concentrations (100 and 1000 µg L-1). The software Hydrus 1D was used to simulate experimental data. Caffeine and acetaminophen were never detected at the column outlet indicating a low environmental concern. On the other hand, attenuation of the detected pharmaceuticals could be reproduced by a combination of retardation and removal approaches. Carbamazepine is among the selected contaminants the most persistent. A dependence of removal rates on input concentrations was detected for sulfamethoxazole (µw from 2.78 d-1 to 1.16 d-1) and naproxen (µw from 1.16 d-1 to 0.63 d-1) attributed mainly to decreased metabolism of microorganisms when a higher input concentration is applied. Two transformation products (TPs) (N4-Acetylsulfamethoxazole and epoxycarbamazepine) derived from sulfamethoxazole and carbamazepine transformation, respectively, were detected during the experiment with the highest input concentration.

Soil amendment using poplar woodchips to enhance the treatment of wastewater-originated nutrients.

Vegetation filters, a nature based wastewater regeneration technology, have been reported as a feasible solution for small municipalities and scattered populations with limited access to sewage networks. However even when such a treatment is properly planned, the leaching of contaminants through the unsaturated zone may occur. The amendment of soil with a readily-labile source of carbon is supposed to ameliorate the removal of contaminants by stimulating microbial activity and enhancing sorption processes. In this study, lab-scale leaching column experiments were carried out to explore if the addition of woodchips to the soil could be a feasible strategy to be integrated in a vegetation filter. Two different types of arrangement of soil and woodchips layers were tested. The soil was collected from an operating vegetation filter treating wastewater of an office building characterised by a high nutrient load. Daily pulse of synthetic wastewater were applied into the columns and effluent samples were collected and analyzed for major ions, total nitrogen (NT), total phosphorous (PT) and chemical oxygen demand (COD). By the end of the experiment, NT, NO3-N and PT soil contents were also measured. Results indicate that amendments with woodchips enhance the elimination of wastewater-originated contaminants. NT removal in the columns with woodchips reaches a value of 99.4%. The main processes responsible for this elimination are NH4-N sorption and nitrification/denitrification. This latter fostered by the reduced redox conditions due to the enhanced microbial activity. High removal of PT (99%) is achieved independently of the woodchips presence due to retention and/or precipitation phenomena. The COD removal efficiency is not affected by the presence of the woodchips. The leaching of organic carbon occurs only during the experimental start-up period.

The role of sorption and biodegradation in the removal of acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole during soil contact: A kinetics study.

In countries like Spain, where water is a limited resource, reusing effluents from wastewater treatment plants may imply the introduction of incompletely eliminated pollutants into the environment. Therefore, this work identified the role of sorption and biodegradation in attenuating pharmaceutical compounds (acetaminophen, carbamazepine, caffeine, naproxen and sulfamethoxazole) in natural soil. It also determined which sorption and removal ("sorption+biodegradation") kinetics models describe the behaviour of these substances in the water-soil system. Presence of potential transformation products (TPs) as a result of pharmaceuticals biodegradation was also studied. To this end, serial batch-type experiments were performed with a soil:water ratio of 1:4 and an initial pharmaceutical concentration of 100µgL(-1). Despite results are dependent on soil characteristics, they revealed that, for those substances with a higher affinity to the soil used (loamy sand), sorption seems to play a key role during the first 48h of contact with soil, and gives way to biodegradation afterwards. The sorption of the pharmaceuticals studied follows a pseudo second-order kinetics. Caffeine and sulfamethoxazole displayed the fastest initial sorption velocities (h=2055 and h=228µgkg(-1)h(-1), respectively). The removal kinetics experiments, satisfactorily simulated by the first-order kinetics model, indicated the presence of potential microbial adaptation to degradation. Indeed, half-lives decreased from 1.6- to 11.7-fold with respect to initial values. The microbial capacity to degrade sulfamethoxazole could be a matter of concern if bacteria have developed resistance to this antibiotic. Caffeine, acetaminophen and sulfamethoxazole were mitigated to a greater extent, whereas the removal of naproxen and carbamazepine was more limited. The appearance of epoxy-carbamazepine and N4-acetyl-sulfamethoxazole as possible TPs of carbamazepine and sulfamethoxazole, respectively, indicated that biodegradation was incomplete and showed the capacity of soil microbes to transform these substances.

Sorption/desorption of non-hydrophobic and ionisable pharmaceutical and personal care products from reclaimed water onto/from a natural sediment.

In the present work, the sorption of pharmaceutical and personal care products (PPCPs) (acetaminophen, atenolol, carbamazepine, caffeine, naproxen and sulphamethoxazole) onto the natural organic matter (NOM) and the inorganic surfaces of a natural sandy loam sediment was quantified separately. The quantification was based on the PPCP charge, their degree of ionisation, their octanol-water partitioning coefficient (KOW) and the sediment organic carbon fraction (ƒOC). PPCP desorption from the sediment was examined under conditions of infiltrating water containing a high concentration of inorganic ions (mimicking infiltrating reclaimed water), and a low concentration (and smaller diversity) of inorganic ions (mimicking rainwater infiltration). Batch tests were performed using a sediment/water ratio of 1:4 and a PPCP initial concentration ranging from 1 to 100 µg L(-1). The results showed the type and degree of PPCP ionisation to strongly influence the sorption of these compounds onto the sediment. The sorption of cationic species onto the sediment was higher than that of anionic species and mostly reversible; the sorption of neutral species was negligible. The anionic species sorbed less onto the sediment, but also desorbed less easily. More than 70% of the total sorption was due to interaction with mineral surfaces. This holds especially true for cationic species (atenolol and caffeine) which sorption was enhanced by the negative surface charge of the sediment. The presence of inorganic ions had no impact on the desorption of the PPCPs from the sediment. According to the calculated percentages of removal, the mobility followed the order: carbamazepine>acetaminophen>naproxen>atenolol>sulfamethoxazole>caffeine.

Response of microcrustacean communities from the surface-groundwater interface to water contamination in urban river system of the Jarama basin (central Spain).

In order to evaluate the water quality at the surface/groundwater interface (hyporheic zone), the pattern of microcrustacean assemblages in response to environmental stress caused by urban industrial contamination was studied in the Jarama River basin (central Spain) during high water discharges (March and April 2011). The clustering of biological variables and the concentration of urban contaminants in hyporheic waters showed that pristine hyporheic waters have moderate species diversity (two to seven species) and dominance of k strategist stygobites, whereas excessively contaminated sites are devoid by crustaceans. An intermediate level of disturbance in hyporheic waters is associated with a peak of species taxonomic diversity (four to nine species) and proliferation of r strategist more tolerant species. Typical species found in hyporheic zone, e.g., Paracyclops imminutus (Copepoda, Cyclopoida), Cryptocandona vavrai (Ostracoda) and Herpetocypris chevreuxi (Ostracoda), were good indicators of high concentrations of Cr, Mn, Ni, Cd, Pb and VOCs; whereas the stygobites do not show any significant correlation. The effectiveness of hyporheic crustaceans as efficient bioindicators for assessing the current ecological status of river ecosystems is emphasised.

Removal of trace organic chemicals in onsite wastewater soil treatment units: a laboratory experiment.

Onsite wastewater treatment is used by 20% of residences in the United States. The ability of these systems, specifically soil treatment units (STUs), to attenuate trace organic chemicals (TOrCs) is not well understood. TOrCs released by STUs pose a potential risk to downstream groundwater and hydraulically-connected surface water that may be used as a drinking water source. A series of bench-scale experiments were conducted using sand columns to represent STUs and to evaluate the efficacy of TOrC attenuation as a function of hydraulic loading rate (1, 4, 8, 12, and 30 cm/day). Each hydraulic loading rate was examined using triplicate experimental columns. Columns were initially seeded with raw wastewater to establish a microbial community, after which they were fed with synthetic wastewater and spiked with 17 TOrCs, in four equal doses per day, to provide a consistent influent water quality. After an initial start-up phase, effluent from all columns consistently demonstrated >90% reductions in dissolved organic carbon and nearly complete (>85%) oxidation of ammonia to nitrate, comparable to the performance of field STUs. The results of this study suggest STUs are capable of attenuating many TOrCs present in domestic wastewater, but attenuation is compound-specific. A subset of TOrCs exhibited an inverse relationship with hydraulic loading rate and attenuation efficiency. Atenolol, cimetidine, and TCPP were more effectively attenuated over time in each experiment, suggesting that the microbial community evolved to a stage where these TOrCs were more effectively biotransformed. Aerobic conditions as compared to anaerobic conditions resulted in more efficient attenuation of acetaminophen and cimetidine.