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Zinc contamination in near- and sub-surface environments is a serious threat to many ecosystems and to public health. Sufficient understanding of Zn speciation and transport mechanisms is therefore critical to evaluating its risk to the environment and to developing remediation strategies. The geochemical and mineralogical characteristics of contaminated soils in the vicinity of a Zn ore transportation route were thoroughly investigated using a variety of analytical techniques (sequential extraction, XRF, XRD, SEM, and XAFS). Imported Zn-concentrate (ZnS) was deposited in a receiving facility and dispersed over time to the surrounding roadside areas and rice-paddy soils. Subsequent physical and chemical weathering resulted in dispersal into the subsurface. The species identified in the contaminated areas included Zn-sulfide, Zn-carbonate, other O-coordinated Zn-minerals, and Zn species bound to Fe/Mn oxides or clays, as confirmed by XAFS spectroscopy and sequential extraction. The observed transformation from S-coordinated Zn to O-coordinated Zn associated with minerals suggests that this contaminant can change into more soluble and labile forms as a result of weathering. For the purpose of developing a soil washing remediation process, the contaminated samples were extracted with dilute acids. The extraction efficiency increased with the increase of O-coordinated Zn relative to S-coordinated Zn in the sediment. This study demonstrates that improved understanding of Zn speciation in contaminated soils is essential for well-informed decision making regarding metal mobility and toxicity, as well as for choosing an appropriate remediation strategy using soil washing. [ABSTRACT FROM AUTHOR]

Abstract: Landmark multidimensional scaling (LMDS) uses a subset of data (landmark points) to solve classical multidimensional scaling (MDS), where the scalability is increased but the approximation is noise-sensitive. In this paper we present an LMDS ensemble where we use a portion of the input in a piecewise manner to solve classical MDS, combining individual LMDS solutions which operate on different partitions of the input. Ground control points (GCPs) that are shared by partitions considered in the ensemble, allow us to align individual LMDS solutions in a common coordinate system through affine transformations. We incorporate priors into combining multiple LMDS solutions such that the weighted averaging by priors improves the noise-robustness of our method. Our LMDS ensemble is much less noise-sensitive while maintaining the scalability and the speed of LMDS. Experiments on synthetic data (noisy grid) and real-world data (similar image retrieval) confirm the high performance of the proposed LMDS ensemble. [Copyright &y& Elsevier]

To confirm the feasibility of an outpatient-based pulmonary rehabilitation program in lung cancer patients receiving radiation therapy. Retrospective chart review. Tertiary referral hospital. - Patients with lung cancer who had undergone radiation therapy - Between July 2019 and December 2019 - Total number of patients was 40. Outpatient-based pulmonary rehabilitation program - Eight sessions, 60 minutes per session, twice a week, four consecutive weeks in duration - Under the supervision and guidance of a physical therapist - Physical therapist monitored side effect including fatigue, breathing difficulty, muscle pain, etc. - Each session consisting of warm-up (10 minutes), strengthening exercise (20 minutes / Squats, bridge exercise, bird dog exercise and leg lowering drill / Intensity of 13-15 points of RPE (Rating of perceived exertion), Aerobic exercise (20 minutes / Using fixed cycle / Intensity in the range of 65-85% of maximum heart rate based on age with 13-15 point intensity according to the Borg scale) and cool-down (10 minutes). - Adherence rate of the pulmonary rehabilitation program - Any adverse event related to PR program - 6-minute walk test (6MWT), a grip strength test (before and after PR) - EORTC-QLQ-C30 Questionnaire (before and after PR) - Self-report questionnaire with a 7-point Likert scale on six items. - 29 patients (72.5%) completed PR program - Mean distance of 6MWT was statistically increased from 423.0m to 454.5m - A grip strength test did not show significant improvement in the dominant hand - Among Self-report questionnaire items, overall satisfaction was 5.7 ± 1.1 - Among EORTC-QLQ-30, social functioning score showed improvement with statistically significance and other items did not show significant difference - No adverse events related to PR were reported. Four-week outpatient-based PR program for lung cancer patients receiving outpatient-based radiation therapy is feasible without serious adverse effects. And this program might improve patients' physical function and quality of life. All authors have nothing to disclose. [ABSTRACT FROM AUTHOR]

• Variable-density flow controls the coupling between pressure and concentration data. • The coupling effect is formally quantified by the analysis of mutual information. • We analyze the value-of-information of joint pressure-concentration inversion. • The advantage of joint inversion decreases as the coupling effect increases. • The amount of shared information decreases as permeability heterogeneity increases. Predicting variable-density flow and transport in aquifers is critical for the management of many coastal saline aquifers. Accurate characterization of hydrogeological parameters is critical for prediction, and the characterization is often conducted by assimilating data into models. However, few studies have investigated the underlying physics controlling the value-of-information (VOI) of data for aquifer characterization. In this study, we show how a greater understanding of the underlying physics controlling pressure and concentration data coupling can lead to improved characterization. In variable-density flow, the key physics that controls the VOI of pressure and concentration data is the non-linear coupling between flow and transport via fluid density which causes the pressure field to experience transient changes according to the evolution of salinity distribution. We first demonstrate the coupling between pressure and concentration data using information theory, and then systematically investigate how the variable-density flow impacts the VOI of these data in relation to permeability estimation. Using an ensemble Kalman filter, we estimate the permeability field of saline aquifer systems in two scenarios of data usage: pressure data only, and pressure and concentration data jointly. This study demonstrates that, regardless of the data usage scenario, the maximum VOI of data is obtained when free convection and forced convection are balanced. We further show that the advantage of joint inversion of pressure and concentration data decreases as the coupling effect between flow and transport increases. Finally, we study how the level of permeability field heterogeneity affects the coupling, which in turn controls VOI of pressure and concentration data. [ABSTRACT FROM AUTHOR]

A new method for identifying the petroleum products in contaminated soils is presented, which characterizes the unresolved complex mixture (UCM) hump in the baseline of gas chromatograph (GC) data. The UCM hump identified in soil data was fitted to the Gaussian function, and characterized according to the time for the maximum point ( T UCM ) and the width of the hump ( w ). Experimental results showed that a UCM hump should be clearly observed in soils when contaminated with petroleum, and that soils contaminated with kerosene, diesel, or some lubricating oils estimated herein should present different characteristic values of T UCM and w . Even though the environmental weathering of contaminated soils under evaporative conditions might cause variations in these characteristic values, they converged to specific constants depending on the product. The method could also differentiate between multiple petroleum contaminants in soil. Feasibility was evaluated using soils from a military oil storage site that was closed in 1970. The soil contaminants identified by the proposed method corresponded to the historical storage records, suggesting that the UCM hump characterization method could have strong potential in environmental forensics for differentiating products in petroleum-contaminated soils. [ABSTRACT FROM AUTHOR]

In this study, the organic components were identified that are mainly responsible for the formation of disinfection byproducts (DBPs) and for the biostability of urban surface water. The compositional distribution of dissolved organic matter (DOM) was strongly associated with the potential for both DBP formation and bacterial growth. Further evaluation was carried out (1) to compare the potential for DBP formation upon chlorination of treated water, (2) to determine the biostability that might result from minimizing assimilable organic carbon (AOC), and (3) to use laboratory-scale soil-column experiments to compare the effects of removal of trace organic chemicals (TOrCs) between managed aquifer recharge (MAR) hybrid systems (such as bank filtration followed by artificial recharge and recovery: ARR), and ozonation followed by ARR. Our fractionation and removal methods provided useful insights into the removal of problematic organic components using MAR hybrid systems. Pretreatment with a small amount of ozone (∼0.7 mg-O 3 mg-C −1 ) resulted in improved ARR performance, especially from removing organic acids from DOM, which substantially decreased the potential for DBP formation, while the robust removal of AOC was attributed to a significant decrease in non-acidic and more hydrophilic fractions during soil passage. Both pretreatments used in this study were effective in the removal of selected TOrCs, but carbamazepine was persistent during soil passage. The pretreatment, which used ozonation before ARR, significantly enhanced the removal of carbamazepine; therefore, ozonation followed by ARR is considered an effective way to enhance removal of persistent compounds. [ABSTRACT FROM AUTHOR]

Aquifer storage and recovery (ASR) is a promising approach for managing water resources that enhances water quality through biogeochemical reactions occurring within aquifers. Iron (hydr)oxides, which are the predominant metallic oxides in soil, play a crucial role in degrading dissolved organic carbon (DOC), primarily through a process known as dissimilatory iron reduction (DIR). However, the efficiency of this reaction varies depending on the mineralogy and composition of the aquifer, and this understanding is essential for adequate water quality in ASR. The objective of this study is to investigate the impact of iron (hydr)oxide on acetate, as an organic carbon source, attenuation during the ASR. To achieve this, three sets of laboratory sediment columns were prepared, each containing a different type of iron (hydr)oxide minerals: ferrihydrite, goethite, and hematite. Following an acclimation period of 28 days to simulate the microcosm within an aquifer, the columns were continuously supplied with the simulated river water spiked with acetate (DOC 40–60 mg L−1), and the acetate concentration in the effluent was monitored. The result revealed that the column containing ferrihydrite achieved 97% acetate attenuation through DIR with anoxic conditions (DO < 0.1 mg L−1), while the goethite and hematite columns exhibited limited attenuation rates of 40 and 50%, respectively. Furthermore, the efficiency of acetate attenuation in the ferrihydrite columns increased with the content of ferrihydrite but experienced a rapidly declined at higher contents (3–4%), possibly due to the partial conversion of ferrihydrite to goethite as a result of the interaction between ferrihydrite and the Fe(II) produced during DIR. Additionally, an analysis of the microbial community demonstrated that microorganisms known to possess the ability to reduce iron (hydr)oxides under anaerobic conditions were abundant in the ferrihydrite columns. [Display omitted] • DOC attenuation during the ASR was investigated with iron mineralogy and contents. • Ferrihydrite is the most efficient iron mineral for DOC attenuation via DIR. • At high ferrihydrite contents (>3%), efficiency declines due to Fe(II) intervention. • Ferrihydrite transforms into goethite upon the injection of DOC-reach surface water. • Findings could be beneficial for selecting optimal sites for ASR application. [ABSTRACT FROM AUTHOR]

• Potential effect of NO 3 ⁻ on DOC attenuation during ASR was investigated. • NO 3 ⁻ brings a synergetic effect on DIR-induced DOC attenuation. • Fe(II) released from DIR reduces the bioavailability of Fe (hydr)oxides. • Interaction between DIR and NDFO enables Fe (hydr)oxide bioavailability to maintain. Aquifer storage and recovery (ASR) is a promising water management technique in terms of quantity and quality. During ASR, iron (Fe) (hydr)oxides contained in the aquifer play a crucial role as electron acceptors in attenuating dissolved organic carbon (DOC) in recharging water through dissimilatory iron reduction (DIR). Considering the preference of electron acceptors, nitrate (NO 3 ⁻), possibly coexisting with DOC as the prior electron acceptor to Fe (hydr)oxides, might influence DIR by interrupting electron transfer. However, this phenomenon is yet to be clarified. In this study, we systematically investigated the potential effect of NO 3 ⁻ on DOC attenuation during ASR using a series of sediment columns representing typical aquifer conditions. The results suggest that DOC attenuation could be enhanced by the presence of NO 3 ⁻. Specifically, total DOC attenuation was notably higher than that from the stoichiometric calculation simply employing NO 3 ⁻ as the additional electron acceptor to Fe (hydr)oxides, implying a synergetic effect of NO 3 ⁻ in the overall reactions. X-ray photoelectron spectroscopy analyzes revealed that the Fe(II) ions released from DIR transformed the Fe (hydr)oxides into a less bioavailable form, inhibiting further DIR. In the presence of NO 3 ⁻, however, no aqueous Fe(II) was detected, and another form of Fe (hydr)oxide appeared on the sediment surface. This may be attributed to nitrate-dependent Fe(II) oxidation (NDFO), in which Fe(II) is (re)oxidized into Fe (hydr)oxide, which is available for the subsequent DOC attenuation. These mechanisms were supported by the dominance of DIR-relevant bacteria and the growth of NDFO-related bacteria in the presence of NO 3 ⁻. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract This study evaluated the performance of a pilot-scale hybrid constructed wetland system for secondary effluent and investigated bulk organic matter characteristics. The hybrid constructed wetland consisted of a vertical-flow (VF) bed followed by a horizontal-flow (HF) bed. We also investigated the effects of hydraulic loading rates and influent organic load on the performance of the pilot-scale VF-HF hybrid constructed wetland. The results showed a high removal efficiency for suspended solids (>95%) and organic matter as determined by total organic carbon (>98.5%) and dissolved organic carbon (>70%), but no significant change in nitrogen removal was observed. The wetland treatment efficiency for suspended solids and organic matter showed a good buffer capacity even when hydraulic loading rates increased from 750 to 1500 L m−2 d−1 and 500–1000 L m−2 d−1 during the VF and HF stages, respectively. Moreover, there was no significant change in the performance when influent organic load increased eight-fold. Fluorescence excitation-emission matrix and liquid chromatography-organic carbon detection (LC-OCD) were used to investigate the dissolved organic matter characteristics in the hybrid VF-HF constructed wetland. Fluorescence excitation-emission matrix spectroscopy showed that both protein- and humic-like substances did not significantly change in the effluent when hydraulic loading rates and organic load increased by two- and eight-fold, respectively. Biopolymers determined using LC-OCD were effectively removed via the VF and HF stage wetlands, indicating the occurrence of biodegradation. Fluorescence excitation-emission matrix spectroscopy and LC-OCD provided the fate of dissolved organic matter characteristics in the hybrid VF-HF constructed wetland. Graphical abstract Image 1 Highlights • A pilot scale hybrid VF-HF constructed wetland was used as tertiary treatment. • VF constructed wetland preferentially removed biodegradable organic matter. • Fluorescence EEM and LC-OCD are helpful to understand DOM characteristics. [ABSTRACT FROM AUTHOR]

Highlights • Sediment batch experiments show mixing-dependent DOC biodegradation rates. • Pore-scale incomplete mixing has significant potential impact on field-scale DOC biodegradation. • Pore-scale incomplete mixing can be a major source of uncertainty over a wide range of Pe and Da numbers. Abstract Biogeochemical reactions take place when reactants are present at the same location and time, which occurs through pore-scale mixing. Although the degree of mixing should be variable in space and time, most conventional reactive transport models do not consider mixing-dependent reaction rates and often make predictions based on rates measured with batch experiments. We quantify the effect of pore-scale mixing on the biodegradation rate of dissolved organic carbon (DOC) with sediment batch experiments, and study its potential impact on the field-scale fate and transport of DOC with numerical simulations. We collected sediment samples from an aquifer storage transfer and recovery (ASTR) field site located in Busan, South Korea, and conducted batch experiments to measure mixing-dependent biodegradation rates. Complete mixing conditions were realized by continuously shaking the batch, and diffusion-limited mixing conditions were realized by keeping the batch under static conditions. The two mixing conditions are most widely used conditions in batch experiments and they also represent the maximum and minimum degree of mixing. The different mixing conditions led to significant differences in the biodegradation rates (a factor of 4.9 on average). We then performed reactive transport modeling using the measured biodegradation rates to study the potential impact of pore-scale incomplete mixing on the field-scale DOC biodegradation. The results show that pore-scale mixing can significantly affect the effectiveness of biodegradation at the ASTR site. We generalize this finding by performing a comprehensive nondimensional sensitivity analysis of the fate and transport of DOC to pore-scale mixing conditions over a wide range of P e ´ clet and Damköhler numbers. We show that pore-scale incomplete mixing can be a major source of uncertainty in field-scale model predictions. [ABSTRACT FROM AUTHOR]

Phosphorous is an essential limiting nutrient for which there is no substitute. Its efficient recovery from sewage treatment plants is important to mitigate both dependence on limited reserves of exploitable phosphate rock and eutrophication of surface waters. Here, we evaluate the use of calcium silicate hydrates (CSH) to recover phosphorous eluted from sewage sludge. Phosphorous elution experiments were conducted with acid and base leaching solutions. The phosphorous recovery efficiency with CSH was compared to that with other calcium compounds, and the final product was analyzed to assess its potential value as fertilizer. Dried sewage sludge from the West Lake Ecological Water Resource Center, South Korea, having 123 g-P kg −1 , was used for these tests. About 55% of the phosphorus in the sludge was released with an elution solution of 0.1 M H 2 SO 4 . A dose of 15 g L −1 of CSH recovered 89.6% of the eluted phosphorous without the need for additional pre-treatment, and the resulting calcium phosphate product (in brushite form, based on XRD analysis) exhibited superior settleability than that resulting from Ca(OH) 2 - and CaCl 2 -induced precipitation. XRD peaks of the calcium sulfate hydrate (in gypsum form) and residual CSH were also observed. The final product contained a relatively high content of the total P 2 O 5 eluted in a 2% citric acid solution (43.1%), which suggests that it might be readily used to fertilize crops. [ABSTRACT FROM AUTHOR]

The contribution by anthropogenic sources to abnormally high Zn concentrations in soils with naturally abundant Zn was investigated at a contaminated site surrounding a Zn smelter in eastern Korea. Nineteen soil samples were collected within a 2 km radius of the smelter, and analyzed for metal concentrations and Pb isotope ratios using an inductively coupled plasma-optical emission spectrometer and -mass spectrometer, respectively. Higher Zn concentrations in locations closer to the smelter implied that the smelter was the source of the Zn pollution. Lead isotope ratios ( 206/207 Pb) from soil samples assumed to be unaffected by the smelter were higher than those found in the contaminated area, suggesting that the raw materials of Zn concentrates (ZnS, sphalerites) and smelting by-products from the smelter with low 206/207 Pb ratios were the anthropogenic Zn source impacting the area. To verify this finding, the mineralogical forms of Zn found in the different soil fractions were investigated by X-ray diffraction analysis, scanning-electron-microscope energy-dispersive spectrometer analysis, and sulfur element analysis. Since approximately 50% of Zn concentrates have particle sizes less than 0.044 mm, the observation of sphalerites and elevated sulfur concentrations in the finer soil fraction (< 0.044 mm) provide substantial support to the hypothesis that the deposition of airborne Zn-containing dust from the smelter is responsible for the high Zn concentration in the area. [ABSTRACT FROM AUTHOR]

The migration of petroleum hydrocarbons in vadose zone involves complex coupled processes such as downward displacement and natural attenuation. Despite its significance in determining groundwater vulnerability to petroleum contamination and optimizing the remedial strategy, it has not been comprehensively studied in terms of overall processes under field-relevant conditions. In this study, a series of unsaturated soil column experiments were conducted by simulating subsurface diesel contamination within a vadose zone using different soil textures at different soil bulk densities and initial diesel concentrations, while partly exposing them to simulated precipitation. The results showed that the soil column with less fine fraction was favorable for the downward migration of diesel but unfavorable for its natural degradation. However, precipitation complicated the relative conductivities of multiple fluids (water, air, and diesel) through the pore network, therby decreasing diesel migration and degradation. For example, the downward migration of diesel in the SL column decreased by 8.4% under precipitation, while the overall attenuation rate dropped to almost 0.24% of its original state. Lowering bulk density (from 1.5 to 1.23 g/cm3), however, could enhance the attenuation rate presumably due to the secured void space for the incoming fluids. A high initial concentration of diesel (2%; w/w) inhibited its natural attenuation, while its influence on its vertical propagation after the precipitation was not significant. The present findings provide a mechanistic basis for approximating the behavior of petroleum hydrocarbons in a random vadose zone. [Display omitted] • Fate and transport of diesel in vadose zone was investigated in a holistic manner. • Soil pore network governs both the migration and natural attenuation of diesel. • Precipitation can enhance or inhibit the diesel behavior depending on soil textures. • Low soil density can reudce the decrease of diesel attenuation under precipitation. • High initial concentration of diesel can decrease its natural attenuation. [ABSTRACT FROM AUTHOR]

We investigate tracer transport on random discrete fracture networks that are characterized by the statistics of the fracture geometry and hydraulic conductivity. While it is well known that tracer transport through fractured media can be anomalous and particle injection modes can have major impact on dispersion, the incorporation of injection modes into effective transport modeling has remained an open issue. The fundamental reason behind this challenge is that—even if the Eulerian fluid velocity is steady—the Lagrangian velocity distribution experienced by tracer particles evolves with time from its initial distribution, which is dictated by the injection mode, to a stationary velocity distribution. We quantify this evolution by a Markov model for particle velocities that are equidistantly sampled along trajectories. This stochastic approach allows for the systematic incorporation of the initial velocity distribution and quantifies the interplay between velocity distribution and spatial and temporal correlation. The proposed spatial Markov model is characterized by the initial velocity distribution, which is determined by the particle injection mode, the stationary Lagrangian velocity distribution, which is derived from the Eulerian velocity distribution, and the spatial velocity correlation length, which is related to the characteristic fracture length. This effective model leads to a time-domain random walk for the evolution of particle positions and velocities, whose joint distribution follows a Boltzmann equation. Finally, we demonstrate that the proposed model can successfully predict anomalous transport through discrete fracture networks with different levels of heterogeneity and arbitrary tracer injection modes. [ABSTRACT FROM AUTHOR]

Despite its environmental significance, little is known about denitrification in vadose zones owing to the complexity of such environments. Here, we investigated denitrification in unsaturated soils with different pore distributions. To this end, we performed batch-type denitrification experiments and analyzed microbial community shifts before and after possible reactions with nitrates to clarify the relevant denitrifying mechanism in the microcosms. For quantitative comparison, pore distribution in the test soil samples was characterized based on the uniformity coefficient (C u) and water saturation degree (SD). Micro-CT analysis of the soil pore distribution confirmed that the proportion of bigger-sized pores increased with decreasing C u. However, oxygen diffusion into the system was controlled by SD rather than C u. Within a certain SD range (51–67%), the pore condition changed abruptly from an oxic to an anoxic state. Consequently, denitrification occurred even under unsaturated soil conditions when the SD increased beyond 51–67%. High throughput sequencing revealed that the same microbial species were potentially responsible for denitrification under both partially (SD 67%), and fully saturated (SD of 100%) conditions, implying that the mechanism of denitrification in a vadose zone, if it exists, might be possibly similar under varying conditions. [Display omitted] • Denitrifications in unsaturated soils with different pore networks were examined. • Saturation degree (SD) of soils takes priority over the pore size in denitrification. • Denitrification occurs even under unsaturated soil conditions. • The same microbes might work for denitrification in a vadose zone if it occurs. [ABSTRACT FROM AUTHOR]

In this study, indigenous microbes enabling Fe reduction under saline groundwater conditions were identified, and their potential contribution to Fe release from aquifer sediments during managed aquifer recharge (MAR) was evaluated. Sediment and groundwater samples were collected from a MAR feasibility test site in Korea, where adjacent river water will be injected into the confined aquifer. The residual groundwater had a high salinity over 26.0 psu, as well as strong reducing conditions (dissolved oxygen, DO < 2.0 mg/L; oxidation-reduction potential, ORP < − 100 mV) with high Fe 2 + concentrations. The indigenous microbes that mediate the reduction of Fe-minerals in this deep saline aquifer were found to be Citrobacter sp. However, column experiments to simulate field operation scenarios indicated that additional Fe release would be limited during MAR, as the dominant microbial community in the sediment would shift from Citrobacter sp. to Pseudomonas sp. and Limnohabitans sp. as river water injection alters the pore water chemistry. [ABSTRACT FROM AUTHOR]

The natural attenuation potential of a vadose zone against diesel is critical for optimizing remedial actions and determining groundwater vulnerability to contamination. Here, diesel attenuation in unsaturated soils was systematically examined to develop a qualitative relationship between physical soil properties and the natural attenuation capacity of a vadose zone against diesel. The uniformity coefficient (C u) and water saturation (S w , %) were considered as the proxies reflecting the degree of effects by porous network and water content in different soils, respectively. These, in turn, are related to the primary diesel attenuation mechanisms of volatilization and biodegradation. The volatilization of diesel was inversely proportional to C u and S w , which could be attributed to effective pore channels facilitating gas transport. Conversely, biodegradation was highly proportional to C u under unsaturated conditions (S w = 35–71%), owing to nutrients typically associated with fine soil particles. The microbial community in unsaturated soils was affected by S w rather than C u. The overall diesel attenuation including volatilization and biodegradation was optimized at S w = 35% for all tested soils. [Display omitted] • Natural attenuation of diesel was investigated in unsaturated soils. • The uniformity coefficient (C u) and water saturation (S w) were primary variables. • Diesel volatilization was inversely proportional to C u and S w in the local range. • Diesel biodegradation was highly proportional to C u under unsaturated conditions. • Microbial community was primarily changed by S w rather than C u. [ABSTRACT FROM AUTHOR]

Highlights: [•] Washing and drying conditions affect reactivity of nZVIs. [•] Volatile solvent washing decreases thickness of oxide shell layer on nZVIs. [•] Volatile solvent washing increases content of Fe2+-containing oxides in nZVI shell. [•] Volatile solvent washing help nZVIs keep high reactivity even after aerobic drying. [Copyright &y& Elsevier]