Microorganisms are abundant in many surface and near-surface geochemical environments. They interact with arsenic through a variety of mechanisms, including sorption, mobilisation, precipitation and redox and methylation transformation; sometimes, this is to their benefit, while other times it is to their detriment, substantially affecting the fate and transport of arsenic in the environment. Here, an attempt was made to review the current state of knowledge concerning microbial influences on arsenic transformation and retention processes at the water–solid interface with the goal to elucidate the ability of microorganisms to react with arsenic, and to quantify the role of microorganisms in the biogeochemical arsenic cycle. Such knowledge is indispensable for comprehensive understanding arsenic behaviour in the environment and support accurate assessment of the threat of arsenic contamination to human and environmental health, as well as for the development of novel technologies for arsenic bioremediation.

In this work, the sorption of pentachlorophenol (PCP) by non-viable biomass of Rhizopus oryzae ENHE was evaluated. The kinetics and isotherm studies were performed at pH 5.0, 6.0, and 8.0. The point of zero charge of the biomass was determined; this value allowed us to explain the changes of pH during sorption studies. The analyzed experimental kinetic data revealed that Ho’s model adjusted better to the experimental data than Lagergren’s model. PCP sorption was fast; an equilibrium sorption time was reached within 30 min, regardless of pH. PCP sorption at pH 5.0 and 6.0 was better described by the Freundlich isotherm than by the Langmuir isotherm. In contrast, at pH 8.0, the Langmuir isotherm describes better the PCP sorption. Sorption data showed that at pH 5.0 and 6.0, the sorption capacity of PCP was higher than at pH 8.0. Sorption of PCP by the fungal biomass occurred spontaneously; it was endothermic and due to physical sorption. Finally, FT-IR analysis of the dried biomass indicated that amino and hydroxyl groups were involved in the sorption of PCP. This work is one of the few reporting the effect of pH and temperature on the sorption of PCP by microbial biomass from a filamentous fungus belonging to the genus Rhizopus.

Concentrations and bioavailability of Al, Fe, Cd, Pb, Cu, Zn, and Mn in mountain forest soil replanted with speckled alder (Alnus incana (L.) Moench) are explored 7 years after soil surface vs. planting hole application of amphibolite and dolomitic limestone mixture. The mechanisms of slow limestone dissolution are explained and discussed from broader systematic view. The aspects of soil pH and oxidable carbon and the cation exchange capacity changes as well as changes of water-soluble, total, and effective concentrations of tested elements in the amended soils are included. The soil amendment invoked the depletion of K (and slightly Zn) effective concentration. The total concentrations of Ca, Mn, Al, and partly Mg in soil were increased owing to the presence of these elements in the amendment; the water-soluble concentrations nor effective concentrations of Al, Mn, Zn, Cu, Cd, and Pb were increased. Moreover, the effective concentration of Al in both amended variants decreased. The usual negative side effects of liming were not observed due to the slow dissolution of the amendment. Further, the surface application of the amendment is cheaper than the planting hole application, but there are some expected losses of the amendment by concurrent uptake by grass and by flushing. Figure The difference between two liming treatments in contrast to the control

Episodes of pollution resulting from high concentrations of environmental ozone frequently occur in different parts of the world. The ozone can affect human health, natural vegetation, and agricultural productivity. The monitoring of ozone concentrations is essential to aid investigation of its effects and it is also required to assess progress in public management of this pollutant. A new effective and simple technique is presented for the determination of ambient ozone concentrations using a visual procedure. The method is based on the reaction between the dye indigo and ozone, with the formation of colorless products. The bleaching intensity is proportional to the amount of ozone. An indigo color standard scale was developed with the utilization of digital image-based (DIB) calibration and printed as a wheel-chart test kit. Ozone sampling is performed using a passive sampler containing a filter impregnated with indigo. The amount of reacted ozone can be determined by visual comparison using the wheel-chart test kit. The method enables determination of ozone concentrations from 2 to 97 ppb, with intervals of 3 ppb. It does not require an energy source or any post-sampling chemical treatment or analysis, and the ozone concentration can be known immediately, in situ, at the end of the sampling period. The method offers substantial advantages in large-scale mapping and monitoring of ozone or measurements concerning occupational exposure to ozone.

Water quality protection has become a key concern in water resources development and management. Uncontrolled nutrient input may challenge the quality of some water bodies. This study uses the relatively steep Kan watershed located in the north-west of Tehran (Iran) as an example case study, where an artificial lake is currently under construction for recreational purposes. Two approaches to predict the total annual phosphorous load were assessed: the soil and water assessment tool (SWAT) and the export coefficient approach. River discharge and sediment transport were simulated prior to modeling of the total phosphorous (TP) load in SWAT to make the model more accurate. In addition, an upstream to downstream calibration method was utilized. Findings reveal that the SWAT-simulated phosphorous load had sound Nash–Sutcliffe efficiency (ENS) values (ENSof 75 % for calibration and ENSof 52 % for validation). The relative error in estimating annual TP load was 7 %. The export coefficient approach assigning coefficients of export for each land use is known as an alternative method that can be used for estimating the TP load. Four sets of export coefficients were selected from the literature to examine their suitability in TP load prediction. The results showed significant errors in TP load prediction, which indicates that export coefficients are likely to be watershed-specific. Likewise, the export coefficients were found to vary through four wet months with errors ranging from 9 % to 33 %. This paper demonstrates that the export coefficient method may estimate the pollution load in the Kan watershed with less data than the advance SWAT model. However, it is associated with a higher level of error.

The dynamic behavior of water quality and quantity in the Egyptian drains is often viewed as a disruption to the normal operation and performance of the process of water reuse in irrigation. The control of such behavior has been challenging and often elusive in practice. Therefore, this paper presents a framework to advance the understanding and opportunities for improving the reuse process by developing a multivariate process control model. The model starts with preliminary analysis for water quality data that are collected at the reuse site on the examined drain. This phase comprises investigating data distribution and dependency. Then, univariate control charts are used to investigate the state of control for the independent and normally distributed variables. For dependent variables, principal components analysis is used as a method of synthesizing the variables information. In this case, principal component scores are displayed using multivariate control charts. If in-control case existed, process capability index is used to provide a numerical measure of whether or not the reuse process is capable of producing water that satisfies the irrigation quality standards. Since the model will only detect assignable causes if out-of-control or in-capable case existed, management, operational, and/or engineering action will usually be necessary to sustain the reuse process. In these cases, an action plan in response to the model signals will be vital. The main function of the proposed model is to safely manage the reuse practice using statistical quality control techniques. The model was demonstrated using water quality data collected during the period from January 2006 to July 2011 from Hanut (EH02) and El-Salam 3 (ESL03) pump stations along Hadus drain, Eastern Nile Delta-Egypt. The recommended model is automatic, algorithmic, self-tuning, and computerizable.

Nanoscale zero-valent iron supported on activated carbon (NZVI/AC) was synthesized by a modified potassium borohydride reduction method and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and specific surface area (SSA). The effects of NZVI loading on AC, NZVI/AC dosage, pH, the initial concentration of Cr(VI), and temperature on the removal of Cr(VI) were investigated. XRD confirmed the existence of Fe⁰and TEM revealed that the material consisted of mainly spherical bead-like particles aggregated into chains of individual units. The SSA of the iron particles and the removal efficiency of Cr(VI) indicated that the optimum iron loading was 25 %. Increase of NZVI/AC dosage and reaction concentration abated the removal of Cr(VI). Kinetics studies showed that removal of Cr(VI) is a two-step reaction and each step could be expressed by pseudo-first-order reaction kinetics, with initial Cr(VI) and temperature as variables. Total Cr was always almost equal to that of Cr(VI) under all tested conditions, which indicated that little Cr(III) existed in solution. Iron ions, which could cause secondary pollution in the environment, are almost not released from this system. These results demonstrated that NZVI/AC could potentially be used for Cr(VI) removal.

Petroleum hydrocarbons are among the most important contaminants in aquatic ecosystems, but the effects of different petroleum components on the archaeal communities in these environments are still poorly investigated. Therefore, the effects of representative alkanes, polycyclic aromatic hydrocarbons and crude oil on archaeal communities from marine (Massambaba Beach) and hypersaline waters (Vermelha Lagoon) from the Massambaba Environmental Protection Area, Rio de Janeiro, Brazil, were examined in this study. Hydrocarbon contamination was simulated in vitro, and the resulting microcosms were temporally analyzed (4, 12 and 32 days after contamination) using molecular methods. DNA and RNA extractions were followed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analyses and by the further molecular identification of selected DGGE bands. Archaeal communities could not be detected in the marine microcosms after contamination with the different hydrocarbons. In contrast, they were detected by DNA- and RNA-based methods in hypersaline water. Dendrogram analyses of PCR-DGGE showed that the archaeal communities in the hypersaline water-derived microcosms selected for by the addition of heptadecane, naphthalene or crude oil differed from the natural ones observed before the hydrocarbon contaminations. Principal coordinate analysis of the DGGE patterns showed an important effect of incubation time on the archaeal communities. A total of 103 DGGE bands were identified, and phylogenetic analysis showed that 84.4 % and 15.5 % of these sequences were associated with the Euryarchaeota and Crenarchaeota groups, respectively. Most of the sequences obtained were related to uncultivated archaea. Using redundancy analysis, the response of archaeal communities to the type of hydrocarbon contamination used could also be observed in the hypersaline water-derived microcosms.

Sorption–desorption behavior of the antibiotic tetracycline (TET) and the synthetic estrogen hormone 17α-ethinylestradiol (EE2) with wastewater sludge and sludge-derived humic substances [humic acid (HA) and humin] was investigated. From acidic functional group capacity and elemental analyses, HA had higher polarity, aromaticity, and acidity than humin; humin contained aliphatic chains with high mineral content. The different physicochemical properties of the pharmaceuticals and sludge components yielded different kinds of sorption–desorption interactions. Partitioning coefficients (Kd) of TET to sludge were higher (1,552 ± 41–4,667 ± 41 L/kg) than EE2 (534 ± 52–609 ± 47 L/kg). TET sorption was highly pH-dependent and maximal at pH 9. Ca²⁺ions enhanced sorption, emphasizing the role of polyvalent metal ions in forming TET–sludge complexes. Humin was the dominant component for TET sorption due to its high inorganic matter content. In contrast, EE2 sorption was independent of solution pH, forming mostly hydrophobic interactions with sludge organic matter. EE2 had a high affinity for HA due to its chemical structure. Desorption of the two pharmaceuticals differed as well. The amount of desorbed TET (18.7 ± 1.3–29.8 ± 2 %) was lower than that of EE2 (60.6 ± 3–62.3 ± 2 %), and the hysteresis index was higher for TET than EE2. While TET desorption tended to be delayed in the solid matrix, EE2 desorbed easily and in accordance with the aqueous equilibrium concentration. The conclusions emphasize the need for further research into frequently used pharmaceuticals with different physicochemical properties and the recognition of sludge application as an important source of distribution for these contaminants in the environment.

This is the first study that investigates in detail the effect of different sulfate concentrations on trichloroethene-dechlorinating microbial communities, both in terms of dechlorinating performance and microbial composition. The study used a series of Dehalococcoides-containing trichloroethene-dechlorinating microbial communities, which operated for more than 800 days in the presence of different sulfate concentrations and limiting-electron donor conditions. This study proves the ability of Dehalococcoides spp., the only genus able to completely dechlorinate trichloroethene, to predominate in mixed anaerobic microbial communities regardless of the magnitude of sulfate concentration, even under limiting-electron donor conditions. Although other microorganisms, such as the Sulfurospirillum spp. bacteria and members of the sulfate-reducing bacteria group were able to thrive, they were not able to predominate in such a competitive environment. However, this picture was not reflected in reductive dechlorination, which demonstrated a much better performance under methanogenic conditions or in the presence of low sulfate concentration (30 mg/l) than in the presence of higher sulfate concentrations (>400 mg/l). Therefore, different species of Dehalococcoides or other dechlorinating bacteria, which are not able to thrive in the presence of high sulfate concentrations (>400 mg/l), are possibly responsible for the higher dechlorination efficiency that was observed under methanogenic conditions.