The dichlobenil metabolite BAM (2,6-dichlorobenzamide) is frequently detected in aquifers e.g. in Denmark despite the mother compound dichlobenil was banned here since 1997. BAM mineralization was investigated at environmentally relevant concentrations in sediment samples. Undisturbed sediment cores with known dichlobenil application were collected from topsoil to 8.5 m below surface resulting in 57 samples hereof 4 aquifer samples. Mineralization was only substantial (>10%) in the uppermost meter of the unsaturated zone. Microbial adaptation, observed as faster mineralization in pre-exposed than in pristine sediments from the same location, was only evident in sandy sediment where dichlobenil was still present, but not in clayey sediments. Higher initial concentrations (1–5000 μg/kg) did not stimulate mineralization in pristine clayey or sandy sediments, or in pre-exposed sand. However, in pre-exposed clay mineralization was stimulated at high concentrations. Furthermore BAM was for the first time mineralized in aerobic aquifer sediments from different BAM-contaminated groundwater locations.

This study, for the first time, investigates and quantifies the influence of slight changes in solution pH and ionic strength (IS) on colloidal microsphere deposition site coverage by Suwannee River Humic Acid (SRHA) in a column matrix packed with saturated iron-oxide coated sand. Triple pulse experimental (TPE) results show adsorbed SRHA enhances microsphere mobility more at higher pH and lower IS and covers more sites than at higher IS and lower pH. Random sequential adsorption (RSA) modelling of experimental data suggests 1 μg of adsorbed SRHA occupied 9.28 ± 0.03 × 10⁹ sites at pH7.6 and IS of 1.6 mMol but covered 2.75 ± 0.2 × 10⁹ sites at pH6.3 and IS of 20 mMol. Experimental responses are suspected to arise from molecular conformation changes whereby SRHA extends more at higher pH and lower ionic strength but is more compact at lower pH and higher IS. Results suggest effects of pH and IS on regulating SRHA conformation were additive.

A phenanthrene-degrading bacterium, Sphingomonas paucimobilis EPA505 was used to construct two fluorescence-based reporter strains. Strain D harboring gfp gene was constructed to generate green fluorescence when the strain started to biodegrade phenanthrene. Strain S possessing gef gene was designed to die once phenanthrene biodegradation was initiated and thus to lose green fluorescence when visualized by a live/dead cell staining. Confocal laser scanning microscopic observation followed by image analysis demonstrates that the fluorescence intensity generated by strain D increased and the intensity by strain S decreased linearly at the phenanthrene concentration of up to 200 mg/L. Such quantitative increase and decrease of fluorescence intensity in strain D (i.e., from 1 to 11.90 ± 0.72) and strain S (from 1 to 0.40 ± 0.07) were also evident in the presence of Ottawa sand spiked with the phenanthrene up to 1000 mg/kg. The potential use of the reporter strains in quantitatively determining biodegradable or toxic phenanthrene was discussed.

Accurate prediction of the colloid-driven transport of radionuclides in porous media is critical for the long-term safety assessment of radioactive waste disposal repository. However, the co-transport and corelease process of radionuclides with colloids have not been well documented, the intrinsic mechanisms for colloids-driven retention/transport of radionuclides are still pending for further discussion. Thus the controlling factors and governing mechanisms of co-transport and co-release behavior of Eu(III) with bentonite colloids (BC) were discussed and quantified by combining laboratory-scale column experiments, colloid filtration theory and advection dispersion equation model. The results showed that the role of colloids in facilitating or retarding the Eu(III) transport in porous media varied with cations concentration, pH, and humic acid (HA). The transport of Eu(III) was facilitated by the dispersed colloids under the low ionic strength and high pH conditions, while was impeded by the aggregated colloids cluster. The enhancement of Eu(III) transport was not monotonically risen with the increase of colloids concentration, the most optimized colloids concentration in facilitating Eu(III) transport was approximately 150 mg L⁻¹. HA showed significant promotion on both Eu(III) and colloid transport because of not only its strong Eu(III) complexion ability but also the increased dispersion of HA-coated colloid particles. The HA and BC displayed a synergistic effect on Eu(III) transport, the co-transport occurred by forming the ternary BC-HA-Eu(III) hybrid. The transport patterns could be simulated well with a two-site model that used the advection dispersion equation by reflecting the blocking effect. The retarded Eu(III) on the stationary phase was released and remobilized by the introduction of colloids, or by a transient reduction in cation concentration. The findings are essential for predicting the geological fate and the migration risk of radionuclides in the repository environment.

The adsorption of microplastic (MPs) on aquifer media is affected by their own properties and environmental factors. Research results have shown that the adsorption capacity of MPs on the three media has the following order: fine sand > medium sand > coarse sand, and the adsorption equilibrium times are 8 h, 12 h and 24 h, respectively. The adsorption process has three stages (fast linear distribution, slow adsorption and equilibrium stability), and the action law is compounded by the pseudo-second-order kinetic equation. After adsorption, MPs were observed on the three media, and there were single existence and aggregation phenomena. The energy spectrum analysis indicates that elemental carbon (C) appears on the surface of the medium after the action occurs, and the surface of the media adsorbs MPs to varying degrees. According to the results of infrared spectroscopy, after action, the peak areas of the absorption peaks at 680-880 cm⁻¹ and 1450-1620 cm⁻¹ increase. The absorption peaks are mainly C–H out-of-plane bending vibrations from aromatic hydrocarbons and C–H stretching vibrations on the benzene ring skeleton. As the initial concentration increases, the equilibrium adsorption capacity increases linearly. The isothermal adsorption of MPs in porous media conforms to the Freundlich model. The adsorption process is also affected by different anions and cations. The higher the ionic strength of NH₄⁺ is, the weaker the electrostatic effect of negatively charged MPs, thereby increasing the adsorption capacity of microplastics on porous media. Ca²⁺ can promote the adsorption of MPs by the media through the formation of ternary complexes between cations, MPs and surface functional groups. The increase in SO₄²⁻ and HCO₃⁻ concentrations gradually inhibits the adsorption of MPs.

Some of the older Swedish roads contain road tar underneath a surface layer of bituminous asphalt. This road tar, also known as tar asphalt, contains large amounts of polycyclic aromatic hydrocarbons (PAHs). There is concern about PAHs spreading from the bottom layers of these older roads to the surrounding environment, and that because of this spreading road tar asphalt should not be recycled but rather placed in landfills. However, a risk assessment of PAH spreading below roads has not yet been conducted. The first aim of this study was to assess this potential spreading of PAHs from underlying tar asphalt to the sand beneath, the soil next to the roads, as well as nearby groundwater. The second aim was to measure the bioavailability and estimate the toxicity of PAHs in all relevant media using polyoxymethylene (POM) passive samplers. Four road sections and nearby groundwater in northern Sweden were investigated, including a control road without tar asphalt. PAHs were detected in all analysed solid media at varying concentrations: in asphalt from 2.3 to 4800 mg kg⁻¹, in underlying sand from <1.5 to 460 mg kg⁻¹ and in slope soil from <1.5 to 36 mg kg⁻¹. However, the spread of PAHs from the asphalt to roadside soil and groundwater was very limited. Groundwater at most of the road sections contained very low or non-detectable levels of PAHs (<0.08–0.53 μg L⁻¹, excluding one site where fuel contamination is hypothesized). The PAHs generally showed low bioavailability. Only asphalt with PAH content >1200 mg kg⁻¹ exhibited bioavailable concentrations that exceeded threshold concentrations for serious risk. The most PAH contaminated sand and soil samples exhibited low toxicity when considering bioavailability, only in some cases exceeding chronic toxicity threshold concentrations. These results were compared with the Swedish EPA's guideline values for PAH in contaminated soil, which is shown to overpredict toxicity for these sites. Further research on the leaching and transportation processes of PAHs from subsurface tar asphalt is recommended for developing risk analysis approaches.

First flush or the first pore volume of effluent eluted from biofilters at the start of rainfall contributes to most pollution downstream because it typically contains a high concentration of bacterial pathogens. Thus, it is critical to evaluate designs that could minimize the release of bacteria during a period of high risk. In this study, we test the hypothesis of whether an addition of iron-based media to biofilter could limit the leaching of Escherichia coli (E. coli), a pathogen indicator, during the first flush. We applied E. coli-contaminated stormwater intermittently in columns packed with a mixture of sand and compost (70:30 by volume, respectively) and iron filings at three concentrations: 0% (control), 3%, and 10% by weight. Columns packed with a mixture of sand and iron (3% or 10%) without compost were used to examine the maximum capacity of iron to remove E. coli. In columns with iron, particularly 10% by weight, the leaching of E. coli during the first flush was 32% lower than the leaching from compost columns, indicating that the addition of iron amendments could decrease first-flush leaching of E. coli. We attribute this result to the ability of iron to increase adsorption and decrease growth during antecedent drying periods. Although the addition of iron filings increased E. coli removal, the presence of compost decreased the adsorption capacity: exposure of 1 g of iron filings to 1 mg of DOC reduces E. coli removal by 8%. The result was attributed to the alteration of the surface charge of iron and blocking of adsorption sites shared by E. coli and DOC. Collectively, these results indicate that the addition of sufficient amounts of iron media could decrease pathogen leaching in the first flush effluent and increase the overall biofilter performance and protect downstream water quality.

Long term monitoring of atmospheric wet and dry depositions and associated nutrients fluxes was conducted on the coast of Japan facing the East China Sea continuously for 1 year and 2 months, with the origin of air mass investigated based on isotope analyses (Sr, Nd, and NO₃). During the same period, intensive observations of ocean conditions and the chemical composition of sinking particles collected using sediment traps were conducted to investigate the effects of atmospheric deposition-derived nutrients on phytoplankton blooms. Dry-deposition-derived nutrient inputs to the surface ocean were larger during autumn to spring than in summer due to the effect of continental air mass occasionally carrying Asian dust (yellow sand). However, these nutrients fluxes were limited (1.1–1.5 mg-N m⁻² day⁻¹ on average) and didn't appear to cause phytoplankton blooms through the year. Although average dissolved inorganic nitrogen (DIN) concentrations in rainwater were lower in oceanic air masses compared to continental air masses, wet-deposition-derived nutrient inputs to the surface ocean on rainy days during the summer (26.0 mg-N m⁻² day⁻¹ on average) were large due to higher precipitation from oceanic air masses. Wet-deposition-derived nutrients significantly increased nutrient concentrations in the surface ocean and seemed to cause phytoplankton blooms in the warm rainy season when nutrients in the surface were depleted due to increased stratification. The increase in phytoplankton biomass was reflected in increased particle sinking into the bottom layer, as well as changing chemical characteristics. The supply of flesh phytoplankton-derived labile organic matter into the bottom layer could be expected to promote rapid bacterial decomposition and contribute to the formation of hypoxic water masses in early summer when the ocean was strongly stratified. Atmospheric deposition-derived nutrients in East Asia will have important impacts on not only the oligotrophic outer ocean but also surrounding coastal areas in the warm rainy season.

Microplastic pollution is a global concern theme, and there is still the need for less laborious and faster analytical methods aiming at microplastics detection. This article describes a high throughput screening method based on near-infrared hyperspectral imaging (HSI-NIR) to identify microplastics in beach sand automatically with minimum sample preparation. The method operates directly in the entire sample or on its retained fraction (150 μm–5 mm) after sieving. Small colorless microplastics (<600 μm) that would probably be imperceptible as a microplastic by visual inspection, or missed during manual pick up, can be easily detected. No spectroscopic subsampling was performed due to the high-speed analysis of line-scan instrumentation, allowing multiple microplastics to be assessed simultaneously (video available). This characteristic is an advantage over conventional infrared (IR) spectrometers. A 75 cm² scan area was probed in less than 1 min at a pixel size of 156 × 156 μm. An in-house comprehensive spectral dataset, including weathered microplastics, was used to build multivariate supervised soft independent modelling of class analogy (SIMCA) classification models. The chemometric models were validated for hundreds of microplastics (primary and secondary) collected in the environment. The effect of particle size, color and weathering are discussed. Models' sensitivity and specificity for polyethylene (PE), polypropylene (PP), polyamide-6 (PA), polyethylene terephthalate (PET) and polystyrene (PS) were over 99% at the defined statistical threshold. The method was applied to a sand sample, identifying 803 particles without prior visual sorting, showing automatic identification was robust and reliable even for weathered microplastics analyzed together with other matrix constituents. The HSI-NIR-SIMCA described is also applicable for microplastics extracted from other matrices after sample preparation. The HSI-NIR principals were compared to other common techniques used to microplastic chemical characterization. The results show the potential to use HSI-NIR combined with classification models as a comprehensive microplastic-type characterization screening.

Marine canopies formed by seagrass and other coastal vegetated ecosystems could act as sinks of microplastics for being efficient particle traps. Here we investigated for the first time the occurrence of microplastic retention by marine canopies in a hydraulic flume under unidirectional flow velocities from 2 to 30 cm s⁻¹. We used as model canopy-forming species the seagrass Zostera marina with four canopy shoot density (0, 50, 100, 200 shoots m⁻²), and we used as microplastic particles industrial pristine pellets with specific densities from 0.90 to 1.34 g cm⁻³ (polypropylene PP; polystyrene PS; polyamide 6 PA; and polyethylene terephthalate PET). Overall, microplastics particles transported with the flow were retained in the seagrass canopies but not in bare sand. While seagrass canopies retained floating microplastics (PP) only at low velocities (<12 cm s⁻¹) due to a barrier created by the canopy touching the water surface, the retention of sinking particles (PS, PA, PET) occurred across a wider range of flow velocities. Our simulations revealed that less dense sinking particles (PS) might escape from the canopy at high velocities, while denser sinking particles can be trapped in scouring areas created by erosive processes around the eelgrass shoots. Our results show that marine canopies might act as potential barriers or sinks for microplastics at certain bio-physical conditions, with the probability of retention generally increasing with the seagrass shoot density and polymer specific density and decreasing with the flow velocity. We conclude that seagrass meadows, and other aquatic canopy-forming ecosystems, should be prioritized habitats in assessment of microplastic exposure and impact on coastal areas since they may accumulate high concentration of microplastic particles that could affect associated fauna.