Incidental zinc sulfide nanoparticles (nano-ZnS) are spread on soils through organic waste (OW) recycling. Here we performed soil incubations with synthetic nano-ZnS (3 nm crystallite size), representative of the form found in OW. We used an original set of techniques to reveal the fate of nano-ZnS in two soils with different properties. 68 Zn tracing and nano-DGT were combined during soil incubation to discriminate the available natural Zn from the soil, and the available Zn from the dissolved nano-68 ZnS. This combination was crucial to highlight the dissolution of nano-68 ZnS as of the third day of incubation. Based on the extended X-ray absorption fine structure, we revealed faster dissolution of nano-ZnS in clayey soil (82% within 1 month) than in sandy soil (2% within 1 month). However, the nano-DGT results showed limited availability of Zn released by nano-ZnS dissolution after 1 month in the clayey soil compared with the sandy soil. These results highlighted: (i) the key role of soil properties for nano-ZnS fate, and (ii) fast dissolution of nano-ZnS in clayey soil. Finally, the higher availability of Zn in the sandy soil despite the lower nano-ZnS dissolution rate is counterintuitive. This study demonstrated that, in addition to nanoparticle dissolution, it is also essential to take the availability of released ions into account when studying the fate of nanoparticles in soil.

In order to determine the mechanisms of the retention of 60Co, 85Sr and 134Cs in natural silica sand columns, desorption experiments were performed by changes of pH and ionic strength and by injection of natural organic matter (NOM). Injection of KCl (0.1 M) resulted in a high release of 60Co (60-100%) and 85Sr (72-100%) but a smaller release of 134Cs (31-66%). Only limited release of 60Co (66%) and 85Sr (71%) and no release of 134Cs were observed by injection of NOM. The different percentages of desorption were related to the chemical characteristics of the organic colloids previously retained in columns before the desorption step. The results evidenced different sorption processes on energetically heterogeneous surface sites. According to the initial conditions, the binding of the radionuclides to the solid phase resulted from weak and easily reversible sorption processes to strong association probably by inner sphere complexes. The rather weak release of 134Cs by KCl was attributed to the strong retention of 134Cs by clay coatings on the natural silica sand surfaces. © 2005 Elsevier Ltd. All rights reserved.

The ionic strength of infiltration water changes with the seasonal alternation of irrigation sources. In this study, reactivity changes of birnessite-coated sand with the fluctuations of ionic strength of infiltration water (i.e. from groundwater to rainwater) and the involved mechanism were investigated through column experiments. Birnessite-coated sand was less reactive in groundwater than in rainwater because of the higher cation content and higher pH of groundwater. The cations in the groundwater were adsorbed on birnessite-coated sand and then desorbed in presence of a dilute aqueous solution represented by rainwater. The reactivity of the passivated birnessite-coated sand was recovered instantaneously, and approximately one-third of the pristine reactivity was restored. During recovery, Na⁺ desorption and lincomycin (LIN) removal both exhibited a two-stage reaction pattern. The LIN removal correlated with Na⁺ desorption (r = 0.99) so that the reactive sites that were binding 5.602 μmol of Na⁺ became available for 1 μmol of LIN removal. These results suggest that the reactivity of manganese oxides toward organic contaminant is associated with the ionic strength of infiltration water and indicate that the partial reactivity can be naturally restored.

Since the fifties, organochlorine pesticides (OCPs) had been used in agriculture to protect vegetables. Two decades after their ban by the Stockholm convention in 2001, OCPs are still present in agricultural soils inducing vegetable contamination with concentrations above Maximum Residue Level (MRL). This is a major concern for a 5 km² peri-urban vegetable growing valley located in the south west of France. In the present work, the sampling method was developed to clarify the spatial distribution of one OCP, Dieldrin, and its relationship with soil properties at the scale of study area. A total of 99 soil samples was collected for physicochemical analyses and Dieldrin concentrations. Results show Dieldrin concentrations in soils up to 204 μg kg⁻¹. The horizontal distribution of this pesticide is heterogeneous at the study area scale but homogeneous in each reference plot studied. About 85% of the contamination was located in the top soil layers (0–40 cm depth), but Dieldrin may still be quantified at a depth of 80 cm. Among all soil physicochemical parameters analysed, SOM was the most significantly related (P < 10⁻⁴) with Dieldrin concentrations, once different grain size fractions were considered. Moreover, results indicate a 33 times higher Dieldrin concentration and/or extractability for coarse sand than for other grain size fractions. These results show that the developed sampling method is adapted for the study area scale as it helps understanding the factors influencing the spatial distribution of Dieldrin. Historical amendments are the predominant factor for the horizontal contamination and deep ploughing for the vertical contamination. Also, the variations of coarse sand repartition in soils prevents identification of relationships between SOM and Dieldrin contamination in bulk soil. Further investigation is required to explain these relationships but these results highlight why no clear relationship between OCPs and SOM was previously identified.

The inconsistency of available methods and the lack of harmonization in current microplastics (MPs) analysis in soils demand approaches for extraction and quantification which can be utilized across a wide variety of soil types. To enable robust and accurate assessment of extraction workflows, PET MPs with an inorganic tracer (Indium, 0.2% wt) were spiked into individual soil subgroups and standard soils with varying compositions. Due to the selectivity of the metal tracer, MPs recovery rates could be quickly and quantitatively assessed using ICP-MS. The evaluation of different methods specifically adapted to the soil properties were assessed by isolating MPs from complex soil matrices by systematically investigating specific subgroups (sand, silt, clay, non-lignified and lignified organic matter) before applying the workflow to standard soils. Removal of recalcitrant organic matter is one of the major hurdles in isolating MPs for further size and chemical characterization, requiring novel approaches to remove lignocellulosic structures. Therefore, a new biotechnological method (3-F-Ultra) was developed which mimics natural degradation processes occurring in aerobic (Fenton) and anaerobic fungi (CAZymes). Finally, a Nile Red staining protocol was developed to evaluate the suitability of the workflow for non-metal-doped MPs, which requires a filter with minimal background residues for further chemical identification, e.g. by μFTIR spectroscopy. Image analysis was performed using a Deep Learning tool, allowing for discrimination between the number of residues in bright-field and MPs counted in fluorescence mode to calculate a Filter Clearness Index (FCI). To validate the workflow, three well-characterized standard soils were analyzed applying the final method, with recoveries of 88% for MPs fragments and 74% for MPs fibers with an average FCI of 0.75. Collectively, this workflow improves our current understanding of how to adapt extraction protocols according to the target soil composition, allowing for improved MPs analysis in environmental sampling campaigns.

We investigated the competitive effects of different fractions of wastewater treatment plant effluent organic matter (EfOM) on adsorption of an organic micro pollutant (OMP), propranolol (PRO), in a fixed bed column packed with magnetic tyre char (MTC). The results showed that the presence of EfOM inhibited PRO adsorption in wastewater leading to decreased PRO adsorption capacity from 5.86 to 2.03 mg/g due to competitive effects and pore blockage by smaller EfOM fractions. Characterization of EfOM using size exclusion chromatography (LC-OCD) showed that the principal factor controlling EfOM adsorption was pore size distribution. Low molecular weight neutrals had the highest adsorption onto MTC while humic substances were the least interfering fraction. Effect of important parameters such as contact time, linear velocity and bed height/diameter ratio on MTC performance was studied in large-lab scale columns. Linear velocity and contact time were found to be effective in increasing adsorption capacity of PRO on MTC and delaying breakthrough time. Increase in linear velocity from 0.64 cm/min to 1.29 cm/min increased mass transfer and dispersion, resulting in considerable rise of adsorbed amount (5.86 mg/g to 22.58 mg/g) and increase in breakthrough time (15.8–62.7 h). Efficiency of non-equilibrium Hydrus model considering dispersion and mass transfer mechanism was demonstrated for real wastewater and scale up purposes. Ball milling for degradation of adsorbed PRO and regeneration of MTC resulted in 79% degradation of PRO was achieved after 5 h milling (550 rpm), while the addition of quartz sand increased the efficiency to 92%.

Effects of commercial sand mining on aquatic diversity are of increasing global concern, especially in parts of some developing countries. However, understanding of this activity on the diversity of macroinvertebrates remains focused on the α component of species diversity, rather than community functioning. Thus, there remains much uncertainty regarding how each component of taxonomic (TD) and functional (FD) diversity respond to the activity both in freshwater and marine environments. Here, we assessed the effect of sand dredging on α, β and γ components of TD and FD during different dredging periods based on the response of macroinvertebrate communities over 4 years in the second largest freshwater lake in China. After three years of active dredging, substantial reductions in each component (α, β and γ) of TD and FD were observed within the dredged area. Moreover, after one year of natural recovery, a distinct restoration was observed with an obvious return in multiple facets of TD and FD indices. No such changes were observed within the adjacent and reference areas. Decreases in the multiple components of TD and FD within the dredged area were most likely associated with the direct extraction of substrate and associated benthic fauna and indirect variations of the water and sediment environment (e.g., increases in water depth and decreases in %Clay). Furthermore, dispersal processes and mass effects mainly contributed to the maintenance of TD and FD during the dredged and recovery stages. In addition, the fast recovery of TD and FD was also related to the simple taxonomic structure and highly connected nature of the study area. Our results suggest that a more precise experimental design (BACI) should be pursued to avoid potentially confounding effects (e.g., natural disturbance) because the sensitivity of diversity indices depends upon different experimental designs. Moreover, measurement of the impacts of sand dredging on macroinvertebrate diversity can be undertaken within a rigorous framework for better understanding the patterns and processes of each component of TD and FD under the sand dredging disturbance.

The feasibility and effectiveness of iron turning waste as low cost and sustainable permeable reactive barrier (PRB) media for remediating dieldrin, endrin, dichlorodiphenyltrichloroethane (DDT), and lindane individually (batch system) and combined (continuous flow column) in water were investigated. After 10 min of reaction in a batch system, removal of endrin, dieldrin, and DDT was higher (86–91 %) than lindane (41 %) using 1 g of iron turning waste in 200 mL of pesticide solution (20 μg/L for each pesticide). Among the studied pesticides, only lindane removal decreased substantially in the presence of nitrate (37 %) and magnesium (18 %). Acidic water environment (pH = 4) favored the pesticide removal than neutral and basic environments. For the column experiments, sand alone as PRB media was ineffective for remediating the pesticides in water. When only iron turning was used, the removal efficiencies of lindane, endrin, and dieldrin were 83–88 % and remained stable during 60 min of the experiments. DDT removal was less than other pesticides (58 %). Sandwiching the iron turning waste media between two sand layers improved DDT removal (79 %) as well as limited the iron content below a permissible level in product water. In a long-term PRB column performance evaluation, iron turning waste (150 g) removed all pesticides in water (initial concentration of each pesticide = 2 μg/L) effectively (≥94 %) at a hydraulic retention time of 1.6 h. Iron turning waste, which was mainly in the form of zerovalent iron (Fe⁰), was oxidized to ferrous (Fe²⁺) and ferric (Fe³⁺) iron during its reaction with pesticides, and electrons donated by Fe⁰ and Fe²⁺ were responsible for complete dechlorination of all the pesticides. Therefore, it can be used as inexpensive and sustainable PRB media for groundwater remediation especially in developing countries where groundwater contamination with pesticides is more prevalent.

The unified bioaccessibility method (UBM) was harnessed to assess in vitro oral bioaccessibility pools of dialkyl phthalate congeners (with methyl, –ethyl, –butylbenzyl, –n-butyl, –2-ethylhexyl, and –n-octyl moieties) and bisphenol A at the 17 μg g⁻¹ level in beach sand contaminated with polyethylene microplastics. A variety of sample preparation approaches prior to the analysis of the UBM gastrointestinal extracts, including traditional methods (protein precipitation, liquid-liquid extraction, and solid-phase extraction) and dispersive liquid-liquid microextraction (DLLME) were comprehensively evaluated for clean-up and analyte enrichment. DLLME was chosen among all tested approaches on account of the high extraction efficiency (73–95%, excluding bis(2-ethylhexyl)phthalate and di-n-octyl phthalate), high sample throughput (∼7 min per set of samples), and environmental friendliness as demonstrated by the analytical eco-scale score of 83, and the green analytical procedure index pictogram with green/yellow labeling. The release of the less hydrophobic plastic-laden compounds (dimethyl phthalate, diethyl phthalate and bisphenol A) from the contaminated sample into the body fluids was significant, with bioaccessibility values ranging from 30 to 70%, and from 43 to 74% in gastric and gastrointestinal fluids, respectively, and with relative standard deviation < 17% in all cases. The majority of the compounds were leached during gastric digestion, likely as the combined action of the low pH and the gastric enzymes. The risk exposure analysis revealed that accumulation/concentration in the body fluids is potentially relevant for dimethyl phthalate, diethyl phthalate and bisphenol A, with relative accumulation ratios ranging from 1.1 ± 0.1 to 2.6 ± 0.4. The average daily intake values for the suite of compounds, corrected with the bioaccessibility fraction, ranged from 60 to 430 ng kg of body weight⁻¹·day⁻¹, in all cases, far below the tolerable daily intakes, thus indicating the lack of children health risk by ingestion of microplastic-laden sand with elevated concentrations of plasticizers.

Capping represents an efficient and well-established practice to contain polycyclic aromatic hydrocarbons (PAHs) in sediments, reduce mobility, and minimize risks. Exposure to PAHs can encourage biodegradation, which can improve the performance of capping. This study investigates biodegradation of naphthalene (a model PAH) in highly reducing, sediment-like environments with amendment of different capping materials (PAC and sand). Microcosms were prepared with sediment enrichments, sulfate as an electron acceptor, and naphthalene. Results show that PAC stimulates naphthalene biodegradation and mineralization, as indicated by production of ¹⁴CO₂ from radiolabeled naphthalene. Mineralization in PAC systems correlates with the enrichment of genera (Geobacter and Desulfovirga) previously identified to biodegrade naphthalene (Spearman’s, p < 0.05). Naphthalene decay in sand and media-free systems was not linked to biodegradation activity (ANOVA, p > 0.05), and microbial communities were correlated to biomass yields rather than metabolites. Naphthalene decay in PAC systems consists of three stages with respect to time: latent (0–88 days), exponential decay (88–210 days), and inactive (210–480 days). This study shows that PAC amendment enhances naphthalene biodegradation under strictly sulfate-reducing conditions and provides a kinetic and metagenomic characterization of systems demonstrating naphthalene decay.