Currently, there are increasing efforts to utilize nanoremediation as an environmental technology for cleaning up polluted environments using nanoscale zero-valent iron (nZVI); however, concerns exist regarding the long-term environmental impact of this strategy. In this study, an innovative methodology for evaluating nZVI impact on soil bacteria is utilized, based on transcriptional analysis of three novel biomakers: tnaA, sodB and trx genes. At the same time, classical toxicological bioassays with the nematode Caenorhabditis elegans were performed. Microcosms treated with 1, 5 and 10 % w/w of nZVI were set up using a commercial standard soil and incubated for 21 days. The tnaA gene, involved in indole production, was significantly upregulated at all assessed nZVI concentrations, suggesting that bacterial cells used this molecule to inform the rest of the community about the changes produced upon nZVI soil treatment. The higher the exposure time, the lower nZVI concentration needed to detect these changes. Consequently, soil bacteria activate a cellular adaptive response to cope with the nZVI-induced oxidative stress, increasing the expression of genes encoding key reactive oxygen species (ROS)-scavenging enzymes; in fact, an upregulation of the sodB and katB genes was recorded upon nZVI exposure. On the contrary, C. elegans survival and growth endpoints were not affected at any nZVI concentration whereas the exposure time significantly increased nematode growth in the soil. Therefore, despite the lack of toxicity revealed by the classical conducted tests, the transcriptional analyses demonstrated the usefulness of combining the set of proposed biomarkers for early detection and monitoring the impact of nZVI on soil bacteria after environmentally important periods of exposure.

The effects of soil micro-particles and micro-pores on the release of total petroleum hydrocarbons (TPH) were investigated using long-term weathered, TPH-contaminated soil samples. The TPH concentrations were analyzed using various extraction schemes (i.e., total extraction, weak extraction, solvent extraction with or without ultrasound). The particle size distribution (<2 mm, 0.063–2 mm, <0.063 mm), micro-pore volume (<0.38 mm), and TPH fraction (C8–14, C16–28, C30–40) of selected samples were also determined to better understand the factors controlling TPH release from contaminated soils. TPH concentrations varied greatly among different fractions of each soil sample, but were highest in the micro-fraction (<0.063 mm) of each sample. In weathered soil samples, TPH was not only weakly or strongly adsorbed on soil particles, but also trapped in soil micro-pores. Moreover, heavier fractions of TPH were released slowly and lesser extent from contaminated soils. Results showed that the solvent extraction method with and without ultrasound could be used to assess relative binding strength of TPH to contaminated soils. These findings imply that to achieve a remediation goal, some contaminated soils require only relatively mild extraction with solvent, but soils with TPH trapped in micro-pores require physical destruction along with chemical extraction.

This study characterizes a biotensoactive produced by the bacterium Azospirillum lipoferum, which was isolated from the rhizospheres of contaminated plants with oil in the lower basin of the Tonala River, Villa Benito Juarez, municipality of Cardenas, Tabasco, Mexico. The following properties were analyzed: viscosity at 25 °C, elemental analysis (% mol) by scanning electron microscopy, density at different temperatures, molecular weight, acute toxicity, median lethal concentration (LC₅₀), and saponification and acidity indices. The effects of pH (6.0, 7.0, 8.0, and 9.0) and temperature (25, 30, 35, and 40 °C) on the production of the biotensoactive and the effect of NaCl on the surface tension, density, and emulsifying capacity were studied. The results showed that the viscosity remained stable between 1.0914 and 1.1276 mPa-s, so the biotensoactive was classified as low-molecular weight. Toxic effects on the population of Eisenia foetida began at surfactant concentrations above 55,000 ppm, and the LC₅₀ was 96,695 ppm. The highest yield of biotensoactive production was obtained 48 h after the beginning of the treatment at pH 8 and pH 9 and 25 °C. At 25 °C, the surface tension ranged from 44.60 mN/m at a 1 % concentration by weight of NaCl to 51.11 mN/m at 15 % NaCl, while at 60 °C, the surface tension ranged from 34.90 mN/m at 1 % NaCl to 40.22 mN/m at 15 % NaCl. The emulsifying capacity was 70 % (aqueous solution 15 % NaCl).

Extension of hydrological or water quality records at short-gauged stations using information from another long-gauged station is termed record extension. The ordinary least squares regression (OLS) is a traditional and commonly used record-extension technique. However, OLS is more appropriate for the substitution of scattered missing values than for record-extension as the OLS provides extended records with underestimated variance. Underestimation of the variance of the extended records leads to underestimation of high percentiles and overestimation of low percentiles given that the data is normally distributed. The Maintenance of Variance Extension techniques (MOVE) have the advantage of maintaining the variance in the extended records. However, the OLS and MOVE techniques are sensitive to the presence of outliers. Two new record-extension techniques with the advantage of being robust in the presence of outliers were recently proposed by the authors: the robust line of organic correlation (RLOC) and modified version of the Kendall-Theil Robust line (KTRL2). In this study a new robust technique is proposed. The new regression technique based on L-moments (LMOM) is a modified version of the RLOC and uses the same intercept as that of RLOC and KTRL2 while the estimated slope is based on the second L-moment. An empirical examination of the preservation of the water quality variable characteristics was carried out using water quality records from the Nile Delta water quality monitoring network in Egypt. A comparison between nine record-extension techniques (OLS, MOVE1 to MOVE4, KTRL, KTRL2, RLOC and LMOM) was performed to examine the extended records for bias and standard error in their statistical moment estimates and over the full range of percentiles. Results showed that the proposed LMOM technique outperforms other techniques by producing extended records that preserve variance as well as extreme percentiles.

Acid mine drainage (AMD) is a persisting environmental problem and a grievous nuisance in the mining sector. In this study, iron (Fe(II)) removal was tested in AMD samples collected from the Enugu Okpara abandoned coal mine (Nigeria), having iron concentrations of ∼1300 mg/l. Digestion, toxicity characteristic leaching procedure (TCLP), and batch adsorption tests using coal bottom ash (BA), bentonite clay (BC), and coal fly ash (FA) were performed. Apart from elucidating the effects of adsorbent dose and initial Fe(II) concentrations on the maximum adsorption capacity (q ₑ) of the adsorbents, the experimental data were also fitted to well-known adsorption isotherms and kinetic models. The results from batch tests showed that the optimum adsorbent dosages for BA, BC, and FA were found to be 3, 4, and 4 g per 100 ml, respectively. Among the different adsorption isotherm models tested, the Temkin model fitted the experimental data well for Fe(II) removal. Results from kinetic analysis showed that the Fe(II) removal efficiency increased with an increase in the contact time and then remained almost constant after 30 min for the three tested adsorbents.

Classification of spectral data has recently drawn more and more attention in environmental and geoscience applications. In the past decade, this attention has been translated into an interest in employing unmixing techniques to retrieve accurate quantitative information suppressed in spectral data. The main task in real applications is to detect potential information regarding the physical and chemical nature of ground targets in different spectral data sources (point field and laboratory spectroscopy, hyperspectral imagery, etc.). Recently, semisupervised classification techniques have been proposed for spectral data by combining ground-truth and laboratory measured spectral signatures and advanced signal processing algorithms based on posterior probability support vector machine and Dempster-Shafer evidence theory. In this paper, the sensitivity of this combined classification method to extract and identify a small amount of settle dust over green vegetation canopy using field spectral data is examined and reported. The results are compared with the performance of selected semisupervised unmixing classification techniques.

The effect of titanium dioxide nanoparticles (TiO₂ NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH₄ ⁺-N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO₂ NPs resulted in increased conversion of NO₂ ⁻-N to NO₃ ⁻-N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO₂ NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge.

The recent rapid expansion of nanotechnologies has increased concern over the impact of engineered nanoparticles (ENPs) on the environment and biota. Although the toxicity of ENPs has received considerable attention in the recent years, there are still gaps in our knowledge of the mechanisms responsible for their effects. In this study, we tested the toxicity of various metal oxide ENPs (Al₂O₃, CuO, Fe₃O₄, MnO, TiO₂, and ZnO), including nanowires together with their bulk counter particles and soluble metal salts, on germinating seeds of Sinapis alba L. Fe₃O₄, TiO₂, MnO₂, and Al₂O₃ ENPs did not negatively affected seed germination at any tested concentrations. However, CuO and ZnO ENPs showed a dose-dependent inhibition of germination. Metal ions were more toxic than metal oxide particles at corresponding concentrations. The highest toxicity was exhibited by Cu, followed by Zn, Fe, Al, and Mn ions. A comparison of ENPs with bulk materials did not reveal significantly higher ENP toxicity. Similarly, nanowires showed effects similar to other nanoparticles and bulk materials. Our results indicate that the nanosize or shape of particles did not play a crucial role, whereas metal ions released into cultivation media and accumulated in seedlings contributed significantly to the phytotoxicity of metal oxides.

Sorption and desorption of heavy metals (Cd, Cu, Pb, and Zn) was evaluated in biochars derived from sugarcane bagasse (SB), eucalyptus forest residues (CE), castor meal (CM), green coconut pericarp (PC), and water hyacinth (WH) as candidate materials for the treatment of contaminated waters and soils. Solid–liquid distribution coefficients depended strongly on the initial metal concentration, with K d,ₘₐₓ values mostly within the range 10³–10⁴ L kg⁻¹. For all biochars, up to 95 % removal of all the target metals from water was achieved. The WH biochar showed the highest K d,ₘₐₓ values for all the metals, especially Cd and Zn, followed by CE (for Cd and Pb) and PC (for Cd, Pb, and Zn). Sorption data were fitted satisfactorily with Freundlich and linear models (in the latter case, for the low concentration range). The sorption appeared to be controlled by cationic exchange, together with specific surface complexation at low metal concentrations. The low desorption yields, generally less than 5 %, confirmed that the sorption process was largely irreversible and that the biochars could potentially be used in decontamination applications.

This study provides an analysis of the spatial distribution and trends of NO, NO₂ and O₃ concentrations in Portugal between 1995 and 2010. Furthermore, an estimation model for daily ozone concentrations was developed for an urban and a rural site. NO concentration showed a significant decreasing trend in most urban stations. A decreasing trend in NO₂ is only observed in the stations with less influence from emissions of primary NO₂. Several stations showed a significant upward trend in O₃ as a result of the decrease in the NO/NO₂ ratio. In the northern rural region, ozone showed a strong correlation with wind direction, highlighting the importance of long-range transport. In the urban site, most of the variance is explained by the NO₂/NOX ratio. The results obtained by the ozone estimation model in the urban site fit 2013 observed data. In the rural site, the estimated ozone during extreme events agrees with observed concentration.