In two soils from Central Greece, a pot experiment was conducted with the addition of mixture at various ratios of zeolite and compost (based on Posidonia oceanica (L.) leaves) applied at a rate of 5% w/w (calculated on a soil dry weight basis). Three varieties of tobacco (Burley, Virginia, and Oriental) were cultivated, and Cu, Zn, and Cd concentrations in tobacco leaves were measured at first, second, and third primings. We found that the addition of zeolite in the soil1 led to a significant reduction of metal concentration in all three tobacco varieties compared to the control. Also, zeolite addition reduced significantly the water-soluble, as well as, DTPA-extractable metal concentrations, compared to the other treatments. Our results suggest that the most effective amendment in soil 1 was the mixture consisting of 20% compost and 80% zeolite; this mixture led to higher reduction of metal concentration in all tobacco varieties. As for soil 2, which had almost twice as high Cd concentrations as than in soil 1, Posidonia compost was more effective in reducing Cd concentrations from all three tobacco varieties. In all cases studied, both in soils 1 and 2, Cd concentration was higher in Burley tobacco leaves. The results indicate that a mixture of zeolite and compost consisting of Posidonia oceanica (L.) is a low-cost soil conditioner that is effective in reducing tobacco Cu, Zn, and Cd uptake.

A set of chitosan-g-poly(acrylic acid)/rice husk ash hydrogel composites was successfully employed as methylene blue (MB) adsorbent. Maximum MB adsorption capacity of 1952 mg/g of dried hydrogel was obtained with the composite at 5 wt% of rice husk ash (RHA) at pH ≥ 5. The adsorption capacity varied from 1450 to 1950 mg/g with increasing the initial MB concentration from 1500 to 2500 mg/L. The MB removal efficiency was higher than 90% for all samples. At pH ≥ 5, negatively charged groups (–COO⁻) in the adsorbent were generated, which could strongly interact with the positive charges from MB, favoring adsorption. Adsorption kinetics followed the pseudo-second-order model, which is based on the chemisorption phenomenon, reaching saturation as fast as 1 h of experiments due to the formation of an adsorbed MB monolayer, as suggested by the Langmuir isotherm model (type I). Desorption experiments showed that 75% of loaded MB can be removed from the adsorbent by immersing it in a pH 1 solution. CHT-g-PAAc/RHA5% composite was submitted to five cycles of adsorption/desorption, maintaining its MB removal efficiency at 91%. Therefore, chitosan-g-poly(acrylic acid)/RHA hydrogel composites present outstanding capacity to be employed in the remediation of MB-contaminated wastewaters.

Energy development in the Bakken and Three Forks formations of the USA has led to an increase in fugitive dust from unpaved roads. A dust abatement alternative that has been considered in this region is oil-well produced waters. The objectives of this study were to compare dust loading at sites abated with produced water to non-abated control sites and to determine if the elemental constituents in released dust are different compared to control roads. Three previously untreated unpaved roads were selected, and passive dust collectors were placed at 10, 20, 40, and 60 m from the road on the downwind side of the dominant prevailing wind in each mile section. Eighty-four days post-application, two sections treated with produced waters failed to reduce dust when compared to the controls. Dust elemental changes were found on two of the three roads. Elements that were found to have differences included Mo, Mn, Fe, As, Au, and Hg. Overall results indicated that oil-well produced water is not effective at controlling road dust. Results of this study are important to road managers who are contemplating the usage of produced waters to reduce dusts from unpaved roads.

Genetically modified agricultural products have been introduced to increase food supply by enhancing their resistance to pests and diseases, along with easily adapting to environmental conditions. Due to the modification of DNA, public objections are prevalent, including concerns on the impact on the ecosystem. In this research, adsorption and transport of Cry1Ab, a toxin exuded by the transgenic Bt maize in alumino-silica clays, were evaluated in laboratory columns under steady-state flow conditions. Since Cry1Ab fate and transport were very responsive to animal waste field applications, during which humic acids were released, Cry1Ab adsorption and transport in humic acid-coated alumino-silica clays were also investigated. Cry1Ab breakthrough curves were simulated using the convection-dispersion transport models. It was discovered that the humic acid coating increased Cry1Ab deposition during the transport. Based on analysis of the breakthrough curves, adsorption isotherms of Cry1Ab in alumino-silica clays were obtained and compared with those of batch experiments. The humic acid coating changed the bonding energy between Cry1Ab and the adsorption receptor sites on alumino-silica clay surfaces, thereby changing Cry1Ab partition between the aqueous phase and the solid phase.

Alpine lakes of the Tatra Mountains were severely affected by acidification, with minimum recorded values of pH ∼4.5 in the mid-1980s. Since the 1990s, a dramatic decrease in the deposition of acidifying compounds has led to a considerable reversal in lake water chemistry (to pH∼5 in the most severely affected lakes). We studied changes of planktonic crustaceans and chironomid occurrence during the acidification period and the following period of recovery from acidification in three categories of 50 Tatra Mountain lakes (non-acidified, acidified and strongly acidified, according to their status at the beginning of the 1980s). In acidified and strongly acidified lakes, the planktonic crustaceans completely disappeared already by about 1976 except for a few individuals of ubiquitous species in littoral zone due to acidification-induced oligotrophication. In strongly acidified lakes, the original planktonic crustaceans disappeared and littoral species became more abundant already before 1976 due to acidification-induced eutrophication and aluminium toxicity. These processes were quickly reversed following the increase in lake water pH. Extinct species started to return to several acidified and strongly acidified lakes already in the beginning of 1990s. The process of recovery was delayed in many other lakes of the same categories, however, or it did not even start before 2008 despite the improved water chemistry and feeding resources (concentration of chlorophyll-a). Compared to planktonic crustaceans, the reaction of chironomids to acidification and recent recovery has been less pronounced. An analysis of sediment records showed that fluctuations in relative abundance of the dominant chironomid taxa and a decrease of their density occurred. In spite of the fact that chironomid fauna exhibited clear signs of recovery in the last two decades, the recovered assemblage does not exactly reflect the pre-acidification status in the lake. The occurrence and higher proportion of more thermophilous chironomid species in some alpine lakes of all categories could be correlated with increasing air temperature. The considerable effect of climatic factors may thus prevent the full re-establishment of the original status even when the acidification stress completely ceases. The delayed return of planktonic crustaceans to some recovered lakes could be a consequence of the short water residence time of these lakes. In addition, a shortening of the water residence time in recent decades, probably related to recent climate change, in interaction with the ecology of planktonic crustaceans, may possibly be causing further delays in their return.

The contamination of drinking water with arsenic has been a problem in a lot of countries around the world because of its toxicological and carcinogenic effects on human health. Porous materials modified with Fe₃O₄ nanoparticles (Fe₃O₄ NPs) represent convenient removers for that contaminant. A co-precipitation method of Fe(III) and Fe(II) in alkaline media was applied to obtain Fe₃O₄ NPs. In a first stage, single nanoparticles were synthesized and stabilized with carboxylic acids. A characterization with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, and X-ray diffraction (XRD) confirms a magnetite-type structure. Moreover, transmission electron microscopy (TEM) and calculations from XRD data using Scherrer’s equation indicate an average particle size of 13 nm and an average crystallite size of 10 nm, both independent of the stabilizer used. Then, the co-precipitation method studied was applied to modify kaolin, bentonite, diatomite, and silica and thus prepare magnetic composites having support-magnetite weight ratios of 2:1. Among them, silica-modified material presented the best hydraulic characteristics, an important aspect for large-scale applications such as removal under gravity. This composite has the capacity to remove up to 80 and 70% for initial concentrations of 25 and 50 μg/L, respectively, representing a convenient remover for processes developed in subsequent stages or in continuous flow.

In Portugal, the industrial production of phosphate fertilizers, has been dealing with a specific raw material—north African phosphate rock—with a high content of trace metals and natural radioactive elements mainly from the ²³⁸U decay series. A disabled phosphate plant located in the vicinity of the river Tejo estuary has produced phosphoric acid for several decades (1950–1989) and dumped tons of phosphogypsum (PG) on retention lagoons, formerly decanted and deposited into a stockpile. This paper deals with the assessment of radionuclides, rare earth elements (REEs) and heavy metals transfer to plants (fam. Plantaginaceae, Plantago sp.) and mosses (fam. Bryaceae, Bryum sp.) growing naturally on the PG pile. In Plantago sp., the concentration ratio (CR, plant tissue/PG) was 0.187 for ²²⁶Ra and 0.293 for ²¹⁰Pb. The translocation factor (TF, aerial parts/roots) was 0.781 for ²²⁶Ra and 0.361 for ²¹⁰Pb. In contradiction to the high CR, the leachability of ²²⁶Ra from PG was low, lower than 2%. The results confirmed the role of mosses as biomonitors. A high quantity of contaminants collected in its biomass confirmed the hypothesis of their significant transport by air and rain water. High concentrations of heavy metals (As, Cd, Zn, W) in samples collected on the stockpile are an evidence of their transport from former industrial zones in the surroundings and present even more important risk for public health and environment than natural radionuclides and REEs from the PG stockpile.

Dimethyl disulfide (DMDS) is a new soil fumigant that is considered a good alternative to methyl bromide due to its high activity toward soil-borne pests, with no ozone-depleting potential. The correlative literature for the study of DMDS and its environmental fate is limited. The hydrolysis kinetics of DMDS were studied in buffered aqueous solutions within a pH of 5, 7, and 9, temperature at 15, 25, 45, and 65 °C, and in natural water samples at an ambient temperature of 25 °C. The results showed that DMDS hydrolysis rates were accelerated by increases in pH and temperature. The calculated half-lives of DMDS hydrolysis in the solutions of pH 5, 7, and 9 were 13.91, 10.81, and 10.52 days, respectively at 25 °C, and the trend showed that DMDS hydrolyzed faster in neutral or mild alkali conditions than in acidic solutions at the same temperature. The calculated half-lives of DMDS hydrolysis in the solutions at 15, 25, 45, and 65 °C were 15.78, 10.81, 9.78, and 7.72 days at pH = 7, respectively. There existed no obvious correlations between the activation energies of DMDS hydrolysis and temperatures. However, the activation entropy absolute values of DMDS hydrolysis increased with increasing temperatures, suggesting that the hydrolysis of DMDS in aqueous solutions was driven by activation entropy. The hydrolysis rates of DMDS in natural water samples are as follows: rice paddy field water > Grand Canal water > tap water. Sterilization of three kinds of natural water samples showed that biodegradation accounted for 4.08, 21.52, and 8.82% in tap water, paddy field water, and Grand Canal water, respectively. This research result has important implications in the scientific evaluation of DMDS.

Dispersal of functional microorganisms is a rate-limiting process during in situ bioremediation of contaminated soil and groundwater. In this work, series of column experiments were conducted to investigate the retention and transport behaviors of Herbaspirillum chlorophenolicum FA1, a promising bacterial agent for bioremediation, in saturated porous media under conditions of different combinations of grain size, solution pH, solution ionic strength (IS), and humic acid (HA) concentration. Experimental data showed that the mobility of FA1 in saturated porous media was strongly dependent on the physicochemical conditions. The breakthrough curves (BTCs) indicated that the amounts of FA1 in the effluent increased with increasing in sand size, solution pH, and HA concentration, but decreased with increase of solution IS. The shape of retention profiles (RPs) was hyper-exponential. The amounts of retained bacteria in the media also varied with the experimental conditions with opposite trends to that of effluent. Both experimental BTCs and RPs were simulated by a mathematical model that accounted for deposition kinetics to better interpret the effects of physicochemical conditions on FA1 deposition dynamics. Findings from this study showed that fate and transport of the functional bacterium FA1 in porous media strongly relied on the environmental conditions. Both experimental and modeling results can provide guidelines for field application of functional bacteria for soil and groundwater remediation.

An innovative diatomite-supported iron catalyst has been developed by using an impregnation process with a mixture of ferrous (Fe²⁺) and ferric (Fe³⁺) ions in the form of precipitated iron hydroxides. Raw and modified diatomite samples have been characterized by X-ray fluorescence and scanning electron microscopy. The main characterization results have revealed that modified diatomites are amorphous and have higher iron concentrations than raw diatomite. The results also indicate that the modified materials provided significant catalytic activity on phenanthrene degradation by using sodium persulfate. Satisfactory results were obtained with 45 g/L of sodium persulfate and 1 g of modified diatomite, thus degrading 98% of phenanthrene during 168 h of treatment. Kinetic and statistical approaches were developed for the remediation process herein, which have been validated with experimental data, thence yielding suitable results.