Mechanism of zinc iron removal by zero-valent iron was discussed through zinc removal responses to several operational conditions of a packed column reactor with zero-valent iron powder. The adsorption isotherm observed implied that a kind of chemisorption was responsible for zinc removal. Zinc removal by zero-valent iron was enhanced by dissolved oxygen and ferric ion addition. However, it was deteriorated under acidic pH. In addition, zinc adsorbed on zero-valent iron was eluted by a reducing agent such as citric acid, whereas the zinc was not eluted by diluted sulfuric acid. Consequently, the zinc removal mechanism by zero-valent iron was inferred to be as follows: Zero-valent iron was firstly corroded and oxidized into ferric ion by dissolved oxygen. The ferric ion was precipitated as iron hydroxide onto the surface of the zero-valent iron powder. Zinc ion was adsorbed on and/or coprecipitated with the iron hydroxide. The iron hydroxide was finally oxidized and transformed into iron oxides.

The analysis of gamma emitters natural radionuclides, i.e., 226Ra, 232Th, and 40K, has been carried out in soil, vegetation, vegetable, and water samples collected from some Northern area of Pakistan, using gamma-ray spectrometry. The γ-ray spectrometry was carried out using high-purity Germanium detector coupled with a computer-based high-resolution multi-channel analyzer. The activity concentrations in soil ranges from 24.7 to 78.5 Bq kg−1, 21.7 to 75.3 Bq kg−1, and 298.5 to 570.8 Bq kg−1 for 226Ra, 232Th, and 40K with the mean value of 42.1, 43.3, 9.5, and 418.3 Bq kg−1, respectively. In the present analysis, 40K was the major radionuclide present in soil, vegetation, fruit, and vegetable samples. The concentration of 40K in vegetation sample varied from 646.6 to 869.6 Bq kg−1 on dry weight basis. However, the concentration of 40K in fruit and vegetable samples varied from 34.0 to 123.3 Bq kg−1 on fresh weight basis. In vegetation samples, along with 40K, 226Ra, and 232Th were also present in small amount. The transfer factors of these radionuclides from soil to vegetation, fruit, and vegetable were also studied. The transfer factors were found in the order: 40K > 232Th ≈ 226Ra. The analysis of water samples showed activity concentrations values for all radionuclides below detection limit. The internal and external hazard indices were measured and found less than the safe limit of unity. The mean value of outdoor and indoor absorbed dose rate in air was found 64.61 and 77.54 nGy h−1, respectively. The activity concentrations of radionuclides found in all samples during the current investigation were nominal. Therefore, they are not associated with any potential source of health hazard to the general public.

Limnologists have regarded temporal coherence (synchrony) as a powerful tool for identifying the relative importance of local-scale regulators and regional climatic drivers on lake ecosystems. Limnological studies on Asian reservoirs have emphasized that climate and hydrology under the influences of monsoon are dominant factors regulating seasonal patterns of lake trophic status; yet, little is known of synchrony or asynchrony of trophic status in the single reservoir ecosystem. Based on monthly monitoring data of chlorophyll a, transparency, nutrients, and nonvolatile suspended solids (NVSS) during 1-year period, the present study evaluated temporal coherence to test whether local-scale regulators disturb the seasonal dynamics of trophic state indices (TSI) in a giant dendritic reservoir, China (Three Gorges Reservoir, TGR). Reservoir-wide coherences for TSICHL, TSISD, and TSITP showed dramatic variations over spatial scale, indicating temporal asynchrony of trophic status. Following the concept of TSI differences, algal productivity in the mainstream of TGR and Xiangxi Bay except the upstream of the bay were always limited by nonalgal turbidity (TSICHL−TSISD <0) rather than nitrogen and phosphorus (TSICHL−TSITN <0 and TSICHL−TSITP <0). The coherence analysis for TSI differences showed that local processes of Xiangxi Bay were the main responsible for local asynchrony of nonalgal turbidity limitation levels. Regression analysis further proved that local temporal asynchrony for TSISD and nonalgal turbidity limitation levels were regulated by local dynamics of NVSS, rather than geographical distance. The implications of the present study are to emphasize that the results of trophic status obtained from a single environment (reservoir mainstream) cannot be extrapolated to other environments (tributary bay) in a way that would allow its use as a sentinel site.

A study to understand the biological effects of samples prepared with lead and the effects of lead were conducted on Lemna minor L. and Spirodela polyrhiza (L.) Schleid. This study was intended to test the hypothesis that nutrient enrichment (P, NO ₃ ⁻ -N and SO ₄ ²⁻ ) enhances the metal tolerance of floating macrophytes. The plants were exposed to Pb concentrations 0, 1, 5, 10, 25, and 50 mg l⁻¹ for a period of 1, 3, 5, and 7 days. L. minor accumulated 561 mg g⁻¹ dry weight (dw) Pb, and S. polyrhiza accumulated 330 mg g⁻¹ dw Pb after 7 days, whereas in the groups enriched with nutrients, L. minor accumulated 128.7 mg g⁻¹ Pb and S. polyrhiza accumulated 68.7 mg g⁻¹ dw Pb after 7 days. Relative growth rates and photosynthetic pigments (chlorophyll a, b, and carotenoid) were measured in L. minor and S. polyrhiza exposed to different Pb concentrations under laboratory conditions. Relative growth rates were negatively correlated with metal exposure, but nutrient addition was found to suppress this effect. Photosynthetic pigment levels were found negatively correlated with metal exposure, and nutrient addition attenuated chlorophyll decrease in response to metal exposure. Metal and nutrient concentration in water decreased throughout the experiments. The study concluded that nutrient enrichment increases the tolerance of L. minor and S. polyrhiza to metals, that L. minor and S. polyrhiza are suitable candidates for the phytoremediation of low-level lead pollution, and that L. minor was more effective in extracting lead than was S. polyrhiza.

Increasing release of organic pollutants to the environment has caused one of the largest world crises for water resources. Volatile organic compounds are toxic monoaromatic pollutants of soil and water. In this research, natural zeolite nanoparticles were produced mechanically by means of a milling technique, modified using two cationic surfactants of hexadecyltrimethylammonium chloride and n-cetyl pyridinium bromide and formed as granules using a novel technique already developed by our group. The granulated adsorbents were used to uptake benzene, toluene, ethylbenzene, and xylenes (BTEX) from contaminated water. Two intra-particle diffusion models (i.e., Weber and Morris and Vermeulen models) and three surface reaction models (i.e., pseudo-first order, pseudo-second order, and Elovich) were applied to evaluate the kinetics of adsorption and the best fitted model was chosen. Results of the adsorption kinetic evaluations were shown that uptake of granulated nanozeolites are higher than natural zeolites (in the order of four). Kinetic results revealed that the adsorption follows a pseudo-second order indicating existence of chemisorption in the studied conditions. It was noticed that the intra-particle diffusion is prevailing in the first stage of adsorption for a relatively short time (i.e., first 25 min).

A multiphase model based on the Mackay-type level II fugacity model has been used to predict the behaviour and final environmental concentrations of some of the more consumed pharmaceuticals in Spain. The model takes into account the mean rate of consumption of pharmaceuticals, the percentage of pharmaceutical metabolised, the formation of the corresponding glucuronide, which is assumed to be hydrolysed back to the parent molecule, the partial degradation of each pharmaceutical in a conventional sewage treatment plant, and the fate of these substances in a regional model environmental system. Predicted environmental concentrations in air, water, soil, sediments and suspended matter, and the corresponding residence time for each pharmaceutical have been obtained by application of the model. The predicted concentrations of pharmaceuticals in the water phase are of the same order than the measured experimentally, showing that the simple model used to predict the environmental concentrations is suitable for modelling the environmental fate of high water soluble and low volatile organic compounds such as pharmaceuticals products.

Fluoride (F) is an air pollutant that causes phytotoxicity. Besides the importance of this, losses of agricultural crops in the vicinity of F polluting industries in Brazil have been recently reported. Injuries caused to plant leaf cell structures by excess F are not well characterized. However, this may contribute to understanding the ways in which plant physiological and biochemical processes are altered. A study evaluated the effects of the atmospheric F on leaf characteristics and growth of young trees of sweet orange and coffee exposed to low (0.04 mol L−1) or high (0.16 mol L−1) doses of HF nebulized in closed chamber for 28 days plus a control treatment not exposed. Gladiolus and ryegrass were used as bioindicators in the experiment to monitor F exposure levels. Fluoride concentration and dry mass of leaves were evaluated. Leaf anatomy was observed under light and electron microscopy. High F concentrations (~180 mg kg−1) were found in leaves of plants exposed at the highest dose of HF. Visual symptoms of F toxicity in leaves of citrus and coffee were observed. Analyses of plant tissue provided evidence that F caused degeneration of cell wall and cytoplasm and disorganization of bundle sheath, which were more evident in Gladiolus and coffee. Minor changes were observed for sweet orange and ryegrass. Increase on individual stomatal area was also marked for the Gladiolus and coffee, and which were characterized by occurrence of opened ostioles. The increased F absorption by leaves and changes at the structural and ultrastructural level of leaf tissues correlated with reduced plant growth.

The concentration of p-cresol and p-ethylphenol, two malodorants typical of swine waste, were measured at 0.5 and 1.5 m above a waste treatment lagoon during two separate campaigns encompassing late winter through early spring and late spring through early summer. Concomitant collection of air temperatures, humidities, insolation, and wind speeds, as well as water column temperatures were done so that heat fluxes could be computed using an energy budget method and Bowen ratio estimates. The empirical model that was found to correlate best with variations in malodorant concentrations and gradients above the lagoon had the terms describing evaporation from the lagoon surface and net available energy at the lagoon surface. Emissions were found to be much higher during the cool season than the warm season. This was despite much higher evaporation rates during the warm season. This could be explained by much lower lagoon concentrations of the malodorants in the warm season than in the cool season. Results of this work are being used to determine appropriate models to estimate malodorant emissions from lagoons and devise techniques for the abatement of nuisance emissions.

The feasibility of employing a porous polyurethane–keratin hybrid membrane for the removal of hexavalent chromium was investigated. Keratin was extracted from chicken feathers and incorporated onto a synthetic polyurethane polymer to synthesize a hybrid membrane. Keratin supply active sites to bioadsorb Cr(VI) and polyurethane play an important role as the support to protein. Also, polyurethane–keratin biofiber membranes were synthesized. Biofibers obtained from chicken feathers were modified to activate their surface. The effective pore in membranes is less than 50 nm, which places these materials in the mesopore range. Scanning electron microscopy (SEM) was used to study the morphology of membranes, and mechanical dynamical analysis (DMA) was used to evaluate the viscoelastic properties. NH, C=O, S–S and C–S were determined via Fourier-transform infrared (FTIR) analysis as functional groups of keratin, which participate in the linking sorption of hexavalent chromium. Adsorption of Cr(VI) was carried out in a filtering system at low contact time in continuous flux; the maximum removal reached was 38% at neutral pH of chromium solution. Results indicate that the isoelectric point of keratin is relevant in the adsorption process. pH of keratin solution above the isoelectric point brings about higher adsorption of heavy metals, whereas lower pH causes minor adsorptions, due to the functional groups’ ion charges. Based on the results, keratin extracted from feathers is a natural biosorbent that can be incorporated onto synthetic polymers to develop novel membranes and improve its applications in the heavy metal separation process.

Bacterial associations with plant roots are thought to contribute to the success of phytoremediation. We tested the effect of addition of a polycyclic aromatic hydrocarbon contaminated soil on the structure of the rhizosphere microbial communities of wheat (Triticum aestivum), lettuce (Lactuca sativa var. Tango), zucchini (Cucurbita pepo spp. pepo var. Black Beauty), and pumpkin (C. pepo spp. pepo var. Howden) 16S rDNA terminal restriction fragment length polymorphism (T-RFLP) profiles of rhizosphere microbial communities from different soil/plant combinations were compared with a pairwise Pearson correlation coefficient. Rhizosphere microbial communities of zucchini and pumpkin grown in the media amended with highest degree of contaminated soil clustered separately, whereas communities of these plants grown in unamended or amended with lower concentrations of contaminated soil, grouped in a second cluster. Lettuce communities grouped similarly to cucurbits communities, whereas wheat communities did not display an obvious clustering. The variability of 16S rDNA T-RFLP profiles among the different plant/soil treatments were mostly due to the difference in relative abundance rather than presence/absence of T-RFLP fragments. Our results suggest that in highly contaminated soils, the rhizosphere microbial community structure is governed more by the degree of contamination rather than the plant host type.