For many years, atmospheric mercury has been perceived as a global pollutant. Transport of mercury compounds in the atmosphere and its deposition on the earth’s surface is an important issue that requires knowledge regarding the circulation of the various forms of this metal between environmental components. There are many numerical models that can be used to study and image this phenomenon. These models are based on data concerning mercury emission sources, concentrations of this contaminant on modelling areas and meteorological data to assess air mass inflow on a regional and global scale. A method to assess mercury deposition fluxes on a local scale based only on stream intensity analysis of mercury is proposed in this study. Mercury deposition fluxes (bulk) that were assessed by the MDC method at the Zloty Potok station (regional background station for the Silesian Agglomeration) varied from 22.8 μg · m⁻² · year⁻¹ (an 8-month period in 2013) to 54.2 μg · m⁻² · year⁻¹ in 2012. Developing procedures to estimate the mercury deposition coefficient (MDC) is useful in areas where only meteorological parameters and mercury concentrations in the atmospheric air are measured. The obtained deposition coefficient values enable quantification of a selected pollutant concentration and its potential impact resulting from deposition.

Activated carbon is investigated as adsorptive barrier for organic micropollutants (OMP) within the Berlin water cycle. In a pilot plant using granular activated carbon (GAC) as upper layer in dual-media filtration, OMP concentrations in treated wastewater could be reduced without any negative impact on filtration efficiency. OMP breakthroughs occurred after shorter runtimes than estimated according to isotherm experiments with powdered activated carbon (PAC). Batch adsorption tests comparing the used GAC to new GAC showed that the capacity of the used GAC was not exhausted, indicating that besides direct site competition, pore blocking is also responsible for the poor GAC performance. A pilot plant application of PAC of the same type as GAC showed significantly higher OMP removals at lower dosages, taking advantage of immobilization of PAC particles in the filters. Both PAC and GAC applications can be integrated into tertiary wastewater treatment without significant constructional changes.

The adsorbents (such as hydrous ferric oxides, HFO) generated in the electrocoagulation (EC) processing with iron electrodes are able to remove effectively inorganic arsenic (As) present in underground water. A characterization of the HFO phases produced during the arsenic removal by the EC process from low and high arsenic concentration, by using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM), is presented. The main HFO phase produced by this process is lepidocrocite (γ-FeOOH), and that the sorption of arsenic by this solid-state phase formed as part of the EC process was effective in removing arsenic from aqueous solution.

From a storm water management perspective, not all pavements are equivalent. Pavement type can impose a strong influence on pollutant wash-off dynamics. Pollutant loads from pavement wash-off are affected by the pavements’ physical and chemical composition. However, there is a dearth of information regarding how pavement type influences atmospherically deposited pollutant loads in storm water. Therefore, experimental impermeable and permeable asphalt and concrete boards were deployed in a residential area in Christchurch, New Zealand, to quantify the influence of pavement type on storm water pollutant dynamics. Each pavement type had four replicate systems elevated 500 mm from the ground at a 4° slope. Wash-off from the pavements was collected and analysed for total suspended solids and metals (Cu, Pb, and Zn) from June to August 2014. Results show that Cu and Zn loads were lower from the concrete pavements than the asphalt pavements because the carbonates and hydroxides within the concrete adsorbed Cu and Zn. Run-off from the impermeable asphalt had the highest loads of Zn, which was attributed to Zn leaching from the asphalt. Infiltrate from permeable asphalt provided little/no retention of Cu and Zn, due to the low pH of the infiltrate causing Cu and Zn to partition into the dissolved phase and leach through the pavement. Total suspended solid (TSS) and Pb loads were the highest in run-off from the impermeable concrete, which was attributed to the smooth surface enabling particulates to be easily mobilised. TSS and Pb loads were the lowest from the permeable pavement due to the permeable material filtering out particulates.

This paper presents the results of a study on mercury distribution in urban wells from the town of Almadén (central Spain), a site that not only hosted the world’s largest mercury mine but also a large roasting plant for cinnabar (HgS). The study includes data on Hg contents in the underground waters and also quality and physical-chemical parameters such as pH, conductivity, oxidation-reduction potential (ORP), dissolved oxygen, and water temperature from 27 wells and 2 monitoring drill holes. An important proportion of the wells (16 %) display Hg concentrations above the European Union Commission (EUC) and Spanish threshold (at 1 μg L⁻¹) and only 10 % exceeded the US EPA recommendation (at 2 μg L⁻¹). As expected, the highest concentrations of dissolved and total Hg are found in wells near to the mine. Hydrochemical water types depend on geogenic and anthropogenic factors, for example, higher mercury concentrations are linked to water-rock interactions (e.g., oxidation, leaching) in sectors where soluble mercury compounds have formed. Hg concentrations show a decrease from 2013 to 2015, a fact that may be due to the encapsulation of the main calcines waste dump or to dilution effects related to strong rainfall events previous to the sampling survey.

Dichlorodiphenyltrichloroethane (DDT) is one of the persistent organic pollutants (POPs) that are highly toxic to the environment. Effective evaluation on the bioavailability of DDTs in soils is essential for risk assessment and soil remediation. The aims of this study were to verify the feasibility of the hydroxypropyl-β-cyclodextrin (HPCD) extraction method for predicting the bioavailability of DDT, dichlorodiphenyldichloroethane (DDD), and dichlorodiphenyldichloroethylene (DDE) in soils, and to examine the effect of HPCD on their biodegradation in different soils. Four soils were aged with a mixture of p,p′-DDT, o,p′-DDT, p,p′-DDD and p,p′-DDE (0.25 μg g⁻¹ for each compound) for 20 and 100 days, respectively. For each of the DDTs, a significant positive correlation between HPCD-extractable fraction and biodegradable fraction in each soil was observed. It was demonstrated that the amounts of HPCD-extractable p,p′-DDT and o,p′-DDT were not significantly different from the amounts that were degradable as assessed from their degradation by Enterobacter sp. LY402 (p > 0.05). Such 1:1 relationship between extraction and degradation was not obtained in the cases of p,p′-DDD and p,p′-DDE, as the amounts of degradable p,p′-DDD and p,p′-DDE were lower than the amounts that were extractable with HPCD. Additionally, the biodegradation of p,p′-DDT, o,p′-DDT, p,p′-DDD, and p,p′-DDE was inhibited in the presence of HPCD, which could be due to the binding of the compounds to HPCD, making them less available to access the bacteria for degradation. This study provides the possibility of using the HPCD extraction method to predict the bioavailability of p,p′-DDT and o,p′-DDT in soils. But when HPCD was used as an additive in the bioremediation of DDT-contaminated soils, it might have a negative effect on biodegradation.

Under various abiotic stresses, plants overproduce reactive oxygen species (ROS) such as superoxide anion (O₂•⁻), hydroxyl radical (OH•), and hydrogen peroxide (H₂O₂). When in excess, these highly reactive molecules cause oxidative stress, thus damaging proteins, lipids, and DNA. Therefore, plants evolved an enzymatic defense machinery that involves such enzymes as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APOX). Various plant families, species and even specimens differ in their ability to withstand the abiotic stress. A study has been undertaken to assess the differences in response to trace metals between two species: a resistant hyperaccumulator Indiana mustard (Brassica juncea) and a metal-sensitive pea (Pisum sativum). We observed that trace elements (Cu, Zn, Cd, Pb) changed the activity of antioxidative enzymes (SOD, APOX, CAT) and the rate of ROS generation. However, in the control plants and at a point 0′ of the treatment, we have noticed a large disproportion in the hydrogen peroxide level, with B. juncea maintaining naturally higher H₂O₂level (up to 40 times higher). We believe that this may be a distinguishing trait common to plants being resistant to oxidative stress.

The remediation of metal-impacted soils requires either the enhanced mobility (and capture) of the target analytes or their effective complexation/immobilisation. In this study, a range of ameliorants (activated carbon, bonemeal, bentonite and CaSx (calcium polysulphide)) were compared to assess their effectiveness in immobilising metals in soils. In addition to chemical analysis (pH and trace element analysis), microbial biosensors were used to assess changes in the water-soluble biotoxicity of metals as a consequence of ameliorant dosing. Management of soil ameliorants requires an enhancement of K d (solid/solution partition coefficient) if soil leachate is to meet predefined environmental quality standards. Of the ameliorants tested, CaSx was the most effective per unit added for both laboratory-amended and historically contaminated soils, regardless of the metal tested. At the ameliorant concentrations used to effectively immobilise the metals, the biosensor performance was not impaired. Microbial biosensors offered a rapid and relevant screening tool to validate the reduced toxicity associated with the ameliorant dosing and could be calibrated to complement chemical analysis. While laboratory-amended soils were a logical way to evaluate the performance of the ameliorants, they were generally associated with K d values an order of magnitude lower than those of historically contaminated soils.

Four kinds of surfactants were used to increase accessibility of pyrene and cadmium (Cd) in simulated pyrene, Cd, and pyrene-Cd soils in this study. Tea saponin (TS) at 40 mg L⁻¹groups (exchangeable fraction of Cd and bioaccessible fraction of pyrene were 8.96 and 36.93 mg kg⁻¹) showed more preferable potential application in improving solubilization capability than other surfactants. The morphology of Cd was transformed from Fe-Mn oxides (8.86 to 7.61 and 8.67 to 7.99 mg kg⁻¹in Cd and pyrene-Cd soil) and associated to carbonates fractions (4.46 to 4.36 and 4.28 to 4.36 mg kg⁻¹in Cd and pyrene-Cd soil) to exchangeable fraction with adding TS. These two morphological changes were important processes in the solubilization of Cd. The morphology of pyrene was transformed from associated fraction (72.15 to 61.95 and 71.02 to 63.48 mg kg⁻¹in pyrene and pyrene-Cd soil) to bioaccessible fraction (26.66 to 33.71 and 26.91 to 36.93 mg kg⁻¹in pyrene and pyrene-Cd soil) with adding TS. This morphological transformation was important in the improving of solubilization capacity of pyrene. In contrast, the solubilization of pyrene was promoted in the presence of Cd in pyrene-Cd soil (the bioaccessible fractions were 33.71 and 36.93 mg kg⁻¹in pyrene and pyrene-Cd soil), but the solubilization of Cd was hindered in the presence of pyrene (the exchangeable fractions of Cd were 8.86 and 8.67 mg kg⁻¹in Cd and pyrene-Cd soil). These findings will be beneficial for application of surfactants in soil remediation.

A geochemical analysis and modelling was carried out to investigate the As occurrence and release in groundwater from two different geological environments on Lesvos Island: (i) the volcanic area of Mandamados (ignimbrite of rhyolithic to rhyodacitic composition) and (ii) the metamorphic area of Tarti (schists and marbles) that comprises the geologic basement under ignimbrite. Seven sampling campaigns were conducted between October 2010 and October 2011, including 65 groundwater samples from 11 wells and springs. Chemical analyses showed As concentrations exceeding the 10-μg/L national drinking water limit in 46 % of the samples from Mandamados. Groundwater composition in Mandamados evolved from Ca-HCO₃ type, to mixed type and finally to Na-Cl type along the groundwater flow direction, indicating the contribution of ion exchange in groundwater chemical composition, while Ca-HCO₃ type waters were observed in the Tarti area. Arsenic speciation analysis showed that As(V) was the main species in all samples, indicating that As was released under oxidizing conditions. Statistical analysis suggested silicate weathering as the prime mechanism of As release in groundwater in both cases, while, in the Tarti area, carbonate dissolution may represent a secondary mechanism which could be related to the observed relatively low As concentrations in the region. In both areas, pH-related desorption of As, primarily from Fe mineral phases, was found to be the most important factor controlling the mobilisation of As, while the contribution of the redox control to As release in groundwater was generally found to be less significant.