The effects of municipal-treated wastewater on growth and gas exchange characteristics were studied in eucalyptus plants cultivated in a greenhouse under continuous sub irrigation with 70 % Long Ashton solution as a control, 100 % treated wastewater, and treated wastewater diluted 50 % with tap water. Irrigation with wastewater resulted in a reduction of total dry matter per plant and the shoot-to-root ratio and increased specific leaf mass, irrespective of the dilution. The gas exchange characteristics were adversely affected by the irrigation with wastewater, with photosynthetic rates been negatively affected. Total chlorophyll and carotenoids content were reduced in plants grown under treated wastewater. The results demonstrated that when the eucalyptus plants were grown under treated wastewater as the only source of mineral nutrients they were able to produce nearly 50 % of the dry matter produced by the plants grown under appropriate mineral nutrient supply, irrespective of the dilution. Therefore, the contribution of mineral nutrients and organic matter from the treated wastewater used as agricultural irrigation will be significant in lower the fertilizer rates without reducing dry matter production per plant.

Spatial and seasonal mobilization trends of metals in surface water were evaluated in the US–Mexico San Pedro River (SPR). Water samples were collected at five sampling stations for the analysis of dissolved oxygen, pH, electric conductivity, sulfates, and metals (Cd, Cu, Fe, Mn, Pb, and Zn). Quality of the water was characterized through Ecological Criteria of Water Quality (ECWQ) established in Mexico and Water Quality Criteria (Environmental Protection Agency (EPA)). High total metal concentrations were detected as follows: Fe > Cu > Mn > Zn > Pb > Cd. Metal concentrations were slightly higher in dry season than in rainy season: Cd (below detection limit (BDL)–0.21 mg L⁻¹), Cu (BDL–13 mg L⁻¹), Fe (0.16–345 mg L⁻¹), Mn (0.12–52 mg L⁻¹), Pb (BDL–0.48 mg L⁻¹), and Zn (0.03–17.8 mg L⁻¹). Low pH and dissolved oxygen values as well as high sulfate content were detected in both seasons. High values of metals (Cd, Cu, Fe, Mn, Pb, Zn) were detected at station E1 representing pollution source, as well as at stations E2 (Cd, Cu, Fe, Mn), E3 (Fe, Mn, Pb), and E4 and E5 (Fe, Mn). Detected concentrations exceeded maximum permissible established in ECWQ and Water Quality Criteria (EPA). Efflorescence salts on sediments in the dry season could increase levels of metals in water column. This study provides valuable information on the potential mobility of metals in surface water of SPR located in an arid environment where transport processes are strongly linked to climate. The information derived from this study should help the regional and national authorities to address present environmental regulations.

Phytostabilization has great practical significance and flexibility in the ecological restoration of mining tailings and remediation of heavy metals polluted soils. However, potential use of metallophytes in phytostabilization is limited by a lack of knowledge of many basic plant processes. A mining ecotype (ME) Athyrium wardii, Pb/Cd phytostabilizer, and a non-mining ecotype (NME) A. wardii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere when exposed to the Cd polluted soils. Rhizobags were used to collect rhizosphere and bulk soils, separately. The results indicated that the ME A. wardii was more efficient in Cd accumulation in the root than NME after growing in Cd polluted soils for 50 days in a green house. Soil solution pH and dissolved organic carbon (DOC) concentration in the rhizosphere of ME A. wardii were higher than in the bulk soil and initial values (before planting), whereas the increment in the ME A. wardii were greater than NME. Owing to the increasing of rhizosphere soil pH, exchangeable Cd significantly decreased, whereas the other Cd species were increased with increasing soil DOC values. It is assumed that the ME A. wardii was effective in stabilizing Cd from the mobile fraction to non-mobile fractions. Results from this study suggest that rhizosphere alkalinization and the exudation of high amounts of dissolved organic matter (DOM) to reduce heavy metal mobility might be the two important mechanisms involved in the metal tolerance/accumulation of ME A. wardii.

The potential for bioremediation of chromium pollution using bacteria was investigated in this study. Five chromium-removing bacteria strains were successfully isolated from Cr(VI)contaminated soils and identified by their 16S rRNA gene sequences. The optimum growth temperature (30–40 °C) and pH (8.5–11) for the five isolates were investigated. The effect of initial Cr(VI) concentrations (0–1,575 mg L⁻¹) on bacterial growth was also studied. Results showed that Pseudochrobactrum saccharolyticum strain W1 had high chromium-removing ability and could grow at Cr(VI) concentrations from 0 to 1,225 mg L⁻¹. To our knowledge, this is the first report of chromium removal by a member of the Pseudochrobactrum genus. Sporosarcina saromensis W5 had the highest chromium-removing rate of 0.79 mg h⁻¹ mg⁻¹biomass. Exopolysaccharide (EPS) production and components of the five bacteria strains were also investigated, and a positive relationship was found between the bacterial chromium removal and EPS production.

Particles derived from humic acid, as p(HA), are synthesized in a single step via a water-in-oil microemulsion system employing different cross-linkers such as divinylsulfone (DVS), glutaraldehyde (GA), epichlorohydrine (ECH), and adipochloride (AC). The different phenolic groups on humic moieties are connected via these cross-linkers to form particles. The prepared p(HA) particles were successfully used in the removal of toxic organo-phenolic such as phenol (Ph), 4-nitrophenol (4-NPh), 4-chlorophenol (4-CPh), 2-chlorophenol (2-CPh), and 2,3-dichlorophenol (2,3-CPh) from aqueous environments. Various parameters such as pH, contact time, reusability of particles, and the initial concentration of adsorbate are investigated. It is found that the absorption capacity of p(HA) particles for Ph is 180 mg/g, and the maximum absorption amount is obtained at pH 6. Furthermore, the reuse experiments are shown that p(HA) particles can release the absorbed Ph by the treatment of methanol, and an absorption capacity of 85 % is attainable up to five consecutive absorption and release cycles. p(HA) particles are characterized by scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential, thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FTIR) techniques.

Larval black flies (Diptera: Simuliidae), which inhabit streams and rivers, are both filter-feeders and a dominant part of the macroinvertebrate community. As filter-feeders, these insects are potentially an important entrance point for mercury into lotic food webs. The objectives of our study were to (1) document mercury concentrations in the water column, streambed sediments, and larval black fly tissue in select streams in coastal Alabama, USA, over both spatial (among streams) and temporal (across and within season) gradients and (2) determine if levels of mercury in stream ecosystems can be predicted based on stream predictors. Mercury was found consistently in both the black fly larval tissues and streambed sediments but was not detected in the water column. The range of total mercury found in larval tissue and stream sediments varied between 23.73–142.05 and 0.60–56.98 ppb, respectively. Mean mercury levels in both tissue and sediments show significant variation among summer, fall, and spring collections. In addition, mercury levels in tissue and sediments were significantly associated with dissolved oxygen, conductivity, or temperature within a season.

The extracellular polymeric substance (EPS) extracted from waste-activated sludge after short-time aerobic digestion was investigated to be used as a novel biosorbent for Cd²⁺removal from water. The sorption kinetics was well fit for the pseudo-second-order model, and the maximum sorption capacity of the EPS (430.3 mg Cd²⁺/g EPS) was markedly higher than those of the reported biosorbents. Both Langmuir model and Freundlich model commendably described the sorption isotherm. The Gibbs free energy analysis of the adsorption showed that the sorption process was feasible and spontaneous. According to the results of multiple analytical techniques, the adsorption process took place via both physical and chemical sorption, but the electrostatic interaction between sorption sites with the functional groups and Cd²⁺was the major mechanism.

Chemically prepared activated carbon derived from durian seed (DSAC) was used as adsorbent to adsorb Malachite green (MG) dye. The prepared DSAC was characterized using Brunauer–Emmet–Teller (BET), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and proximate analysis, respectively. Batch adsorption studies were carried out for the removal of MG dye from aqueous solutions by varying operational parameters like contact time, initial MG dye concentration, solution temperature, and initial solution pH. Maximum dye removal of 97 % was obtained at pH 8. Experimental data were analyzed by eight model equations—Langmuir, Freundlich, Temkin, Dubinin–Radushkevich, Radke–Prausnitz, Sips, Vieth–Sladek, and Brouers–Sotolongo isotherms—and it was found that the Freundlich isotherm model fitted the adsorption data the most. Adsorption rate constants were determined using pseudo-first-order and pseudo-second-order rate equations, Elovich, intraparticle diffusion, and Avrami kinetic model. The results clearly showed that the adsorption of MG dye onto DSAC followed the pseudo-second-order model, and the mechanism of adsorption was controlled both by film diffusion and intraparticle diffusion. Thermodynamic parameters such as ∆G, ∆H, and ∆S were also calculated for the adsorption process. The process was found to be spontaneous and endothermic in nature. This work provided an attractive adsorbent for the removal of MG dye from wastewaters.

The aims of this study were to assess sulfate adsorption in Japanese forest soils and to find and evaluate traces of past heavy anthropogenic sulfur deposition based on the degree of saturation as calculated based on the theoretical adsorption capacity determined by isotherm experiments and the amount of actual adsorbed sulfate. Investigations were conducted at two forest sites, a site in Yokkaichi that is exposed to serious air pollution containing sulfur compounds and a site in Inabu that is unpolluted. The distribution of phosphate-extractable sulfate concentration did not differ between the Yokkaichi site (1.11–13.2 mmol kg⁻¹) and the Inabu site (0.40–11.0 mmol kg⁻¹), and the values were higher than published data for North America and Europe. In contrast, the degree of sulfate saturation in soils of the Yokkaichi site was higher than that in soils of the Inabu site. These results indicate that the degree of sulfate saturation is valuable information for the evaluation of sulfur deposition history. The higher degree of saturation at Yokkaichi site may be due to enhanced sulfate adsorption by soils resulting from substantial past sulfur deposition.

This study focused on the pattern recognition of Malaysian air quality based on the data obtained from the Malaysian Department of Environment (DOE). Eight air quality parameters in ten monitoring stations in Malaysia for 7 years (2005–2011) were gathered. Principal component analysis (PCA) in the environmetric approach was used to identify the sources of pollution in the study locations. The combination of PCA and artificial neural networks (ANN) was developed to determine its predictive ability for the air pollutant index (API). The PCA has identified that CH₄, NmHC, THC, O₃, and PM₁₀are the most significant parameters. The PCA-ANN showed better predictive ability in the determination of API with fewer variables, with R²and root mean square error (RMSE) values of 0.618 and 10.017, respectively. The work has demonstrated the importance of historical data in sampling plan strategies to achieve desired research objectives, as well as to highlight the possibility of determining the optimum number of sampling parameters, which in turn will reduce costs and time of sampling.