A study on the surface modification of uncontaminated sediment dredged for new port development with surfactant was performed, and the effectiveness of surface modified sediment for in-situ capping to control pollutant (N, P) release from the contaminated coastal sediments into seawater was also investigated. From this experiment, the adsorbed amount of surfactants on the surface of sediment particles was increased with the increase in the surfactant concentration. A more feasible method for the sediment modification with surfactants was mechanical shaking for 3 h, compared to sonication for 30 min or microwave radiation for 3 min. The adsorption capacities of the sediments modified with cationic surfactant (hexadecyltrimethylammonium bromide [HDTMA]) were 40 mg g⁻¹ for ammonia-nitrogen, 16 mg g⁻¹ for nitrate-nitrogen, 31 mg g⁻¹ for phosphorus, which are higher those of the sediment modified with anionic (SDS) and nonionic surfactants (TX-100). The capping layer with the sediment modified with HDTMA in column experiment was effective for inhibiting the release of nitrogen and phosphorus from the contaminated sediment into overlying seawater, indicating that the cationic surfactant modified sediment is reusable as a good in-situ capping material for contaminated coastal sediment.

Laoyingshan town lead zinc mine is one of the important zinc production centers in Guizhou province, China. The cadmium (Cd) is one of the mineral resources associated of lead zinc mine. The exploitation and uses of lead zinc mine would lead to Cd pollution to the environment. Soil Cd concentrations in this area are elevated by 30–50 times compared to the national background value in soil which is 0.279 mg kg⁻¹. In situ air Cd concentrations air/soil Cd fluxes were measured at 26 sampling sites in Laoyingshan town by moss bag from Jan. to Sep. 2005. The results showed that the average Cd concentration of total suspended particulates (TSP) and soil were 5.3 and 4.6 times higher than those measured at downwind direction 10 km due to a large amount of Cd emission from traditional melting. The results showed a clear decreasing trend along with the distance increasing from the pollution source for all the study parameters, namely cadmium contents in soil and TSP and deposition rate determined using moss-bag method. The results are consistent with the studied results previously. The correlations between Cd fluxes and soil show the relationship between the content in atmospheric TSP and spatial distribution of deposited heavy metal. The authors found that air spread is the major route of Cd pollution.

Phosphorus (P) release and flux at sediment-water interface was hypothesized to vary with studied catchment branches due to differences in water chemistry of recharging groundwater. Stream water, seepage water, groundwater, and resurgence groundwater were collected, and their dissolved reactive P (DRP) concentrations and related water chemistry variables (pH, dissolved oxygen, cations, and anions) were measured to identify P sources in seepage water and resurgence groundwater and to look into their impacts on stream water DRP. Results showed that the groundwater-carried P concentrations were negligible, and, thus, not a direct source of DRP to stream water. However, the upwelling groundwater could contribute to stream water DRP by dissolving calcite-bound P in top sediments of branch 15. The seepage experiment indicated that in branch14, sediment release of reducible P was minimal. Furthermore, the presence of impermeable clay layer over the streambed of branch 14 prevented the transport of water and nutrients from beneath sediments to stream water, further reducing the P flux across the sediment-water interface. This study revealed that in branch 14, the recharge of anoxic groundwater did not significantly influence stream water P, due directly to its low P concentration, or indirectly to the lack of reducible P and the poor hydrological connectivity in bottom sediments. These results showed that differences between P soluble concentrations in small catchment streams can be explained by physicochemical processes at the sediment-water interface. More investigation is needed to assess whole catchment P dynamics.

The objective of this study was to investigate the effect of chloride ions (Cl⁻) on Cu²⁺adsorption to carbon nanotubes (CNT). The isotherms showed a significant decrease in adsorption capacity on F-400, pristine, and acid-functionalized CNT in the presence of Cl⁻, but had little effect on alcohol-functionalized CNT. Several inductively coupled plasma (ICP) analyses measured the impurities concentration of (1) aqueous-phase isotherm solute, (2) as-received, and (3) acid-washed CNT solutions. Chemical-equilibrium-modeling software MINEQL⁺calculations were applied to compare ICP results to complexes formation. The model suggested that some solid-phase residual-catalytic metals, such as Cr²⁺, after released in water from as-received CNT, formed aqueous-phase complexes and were readsorbed. The 18-metal ICP results were more than two orders of magnitude lower (<4 μM/g-adsorbent) than the lowest isotherm Cu²⁺concentration (157 μM) without significant impact on the isotherm results. The reduced adsorptive capacity of acid-functionalized CNT was related to the mechanisms of water molecule displacement followed by deprotonation during Cu²⁺sorption in the CNT-surface hydration layer and its interaction with other species, generating different ion exchange forces. Brunauer–Emmett–Teller and pore-distribution measurements defined bulk water structure within CNT bundles. Zeta-charge and pHpzc measurements compared as-received and hybrid-CNT indicating copper chemisorption. Functionalized CNT remained negatively charged above pH 2.7, suggesting consistent adsorptive capacity at pH > 5.1, when less Cu²⁺ions are present in solution. scanning electron microscopy–energy dispersive X-ray spectroscopy analysis showed impurities on as-received F-400 and positively charged surface at pH 5.1 (pHpzc 7.1) explaining possible electrostatic attraction of Cl⁻ions, blocking adsorptive sites, reducing its adsorptive capacity for Cu²⁺.

A methodology to determine economically the spatial concentration distribution of the air pollutants of carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen monoxide (NO), nitrogen dioxide (NO₂), oxides of nitrogen (NOₓ) and traffic rates (TR) is described. It involves the immediate transfer of samples from field to analysers for measurement and a subsequent statistical treatment. The proposed methodology has been applied in Patras using 5 and 50-l Teflon air sample bags, sampling at least 12 to 36-l actual volumes within a 20-min time interval. Totally, 221 pairs of 5-l and 112 single 50-l samples were randomly picked in morning rush hours of working days from 64 locations of a 40.0-km²area during a winter period, when peaks of primary air pollutants usually occur due to high traffic rates and systematic inversions. Measurements were used to statistically calculate spatial average levels approximating 1-h mean concentrations with acceptable mean probable errors less than 25 % for indicative random sampling. The 1-h levels were strongly correlated to the corresponding traffic rates. Iso-concentration diagrams indicated possible zones susceptible to high pollution levels and helped to check the location appropriateness of the existing monitoring stations for (a) fixed urban-background measurements at the Vas. Georgiou A’ Sq., which was ideal, and (b) fixed traffic-oriented measurements, which should be relocated to the Ipsilon Alonion Sq. In addition, data helped to determine other points where indicative measurements should be performed. Data could be very useful for the Patras air quality assessment in conjunction with model predictions and/or objective estimation methods.

The growth behavior of canary grass (Phalaris canariensis L) when cultivated in presence of farming fuels is reported in this work. P. canariensis L. is relevant in several countries. It is an emergent plant for phytoremediation and biofuel activities. The following variables: root length, stem length, total plant weight, green tissue weight (tiller, leaf), and total chlorophyll and chlorophyll a/b ratio, were monitored during the growth in presence of commercial fuels (premium grade, regular grade, diesel, and kerosene) at different concentrations. We applied a comprehensive statistical analysis to understand the results: Univariate analysis, factorial analysis of variance, and subsequent Tukey test were applied to the variables to assess the significance of the differences found. The normality of these variables was analyzed with the Shapiro Wilk test. All parameters were affected by all type and concentrations of fuels and its interaction. This is one of the first reported cases which describe the growth parameters responses from canary grass when cultivated in presence of an essentially constant concentration of farming fuels.

Evaluation of variation in the concentration of heavy metal provides vital information about the spatial behavior of the metals affecting the air quality. In the present study, lichen samples of the species Pyxine subcinerea Stirton were collected in the Rudraprayag valley to investigate the metal profile that bioaccumulated in lichens. Multivariate statistical analysis was carried out to elucidate possible contribution of various sources of pollution including anthropogenic sources on heavy metal profile of lichens. Cluster analysis successfully grouped geogenic and anthropogenic inputs represented by Al and Mn and Cu, Cd, Pb, and Zn, respectively. Principal component analysis also segregated sites based on the origin (major contributors).

The present study deals with the synthesis and subsequent application of Fe₃O₄@n-SiO₂nanoparticles for the removal of Cr(VI) from aqueous solutions. Rice husk, an agrowaste material, was used as a precursor for the synthesis of nanoparticles of silica. Synthesized nanoparticles were characterized by XRD and SEM to investigate their specific characteristics. Fe₃O₄@n-SiO₂nanoparticles were used as adsorbent for the removal of Cr(VI) from their aqueous solutions. The effects of various important parameters, such as initial Cr(VI) concentration, adsorbent dose, temperature, and pH, on the removal of Cr(VI) were analyzed and studied. A pH of 2.0 was found to be optimum for the higher removal of Cr(VI) ions. It was observed that removal (%) decreased by increasing initial Cr(VI) concentration from 1.36 × 10⁻²to 2.4 × 10⁻² M. The process of removal was found to be endothermic, and the removal increased with the rise in temperature from 25 to 45 °C. The kinetic data was better fitted in pseudo-second-order model in comparison to pseudo-first-order model. Langmuir and Freundlich adsorption capacities were determined and found to be 3.78 and 1.89 mg/g, respectively, at optimum conditions. The values of ΔG⁰were found to be negative at all temperatures, which confirm the feasibility of the process, while a positive value of ΔH⁰indicates the endothermic nature of the adsorption process. The present study revealed that Fe₃O₄@n-SiO₂nanoparticles can be used as an alternate for the costly adsorbents, and the outcome of this study may be helpful in designing treatment plants for treatment of Cr(VI)-rich effluents.

A new cotton-based hydrogel nanocomposite was successfully prepared by free radical graft copolymerization of acrylamide (AAm) and acrylonitrile (AN) onto fabric followed by insertion of Ag nanoparticles. Ammonium persulfate (APS) was used as an initiator in the presence of a cross-linker, methylene bisacrylamide (MBA). Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were employed to confirm the structure of the hydrogel nanocomposite. Initially, the affecting variables onto graft polymerization (i.e. AAm, AN, MBA, APS, and silver concentrations) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The resulted nanocomposite exhibits superhydrophilic and superhydrophobic properties. Therefore, the grafted fabric selectively separated water from oil/water mixtures with high separation efficiency. The influences of filter type, percentage of coated hydrogel on cotton, presence of silver nanoparticles, pH of solution, extracted oil type, as well as hydrogel nanocomposite on the separation efficiency of filters were also studied in detail. Moreover, pH of zero point charge (pHzₚc) of the hydrogel nanocomposite was determined by alkaline titration method, and a value of 6.5 was obtained.

The aim of this study was to investigate the effect of pH 4 and 7 on the cellular toxicity impact of silver nanoparticles (AgNPs) on the green alga Chlamydomonas acidophila. Changes in chlorophyll content, cellular viability, and reactive oxygen species (ROS) formation were determined permitting the characterization of the toxicity of AgNPs. Chemical characterization of AgNPs in suspension showed that nanoparticle size distribution was dependent to the pH of the culture medium, and a higher solubility was observed at pH 4 compared to that at pH 7. After 24 h of exposure, results indicated that the chlorophyll content and cellular viability decreased significantly, while the intracellular ROS production increased significantly, in relation to the increasing concentration of AgNPs (0.1–100 mg/L). Therefore, our results demonstrated that AgNP-induced toxicity was pH dependent as indicated by the cytotoxicity mediated through the induction of oxidative stress. In conclusion, the characterization of the physicochemical properties of AgNPs in aqueous solution having different pH is essential for the understanding of their toxicity impact on algal cells.