Knowledge of the water sources used by desert trees and shrubs is critical for understanding how they function and respond to groundwater decline and predicting the influence of water table changes on riparian plants. In this paper, we test whether increased depth to groundwater changed the water uptake pattern of desert riparian species and whether competition for water resources between trees and shrubs became more intense with a groundwater depth gradient. The water sources used by plants were calculated using the IsoSource model, and the results suggested differences in water uptake patterns with varying groundwater depths. At the river bank (groundwater depth = 1.8 m), Populus euphratica and Tamarix ramosissima both used a mixture of river water, groundwater, and deeper soil water (>75 cm). When groundwater depth was 3.8 m, trees and shrubs both depended predominantly on soil water stored at 150–375 cm depth. When the groundwater depth was 7.2 m, plant species switched to predominantly use both groundwater and deeper soil water (>375 cm). However, differences in water acquisition patterns between species were not found. The proportional similarity index (PSI) of proportional contribution to water uptake of different water resources between P. euphratica and T. ramosissima was calculated, and results showed that there was intense water resource competition between P. euphratica and T. ramosissima when grown at shallow groundwater depth (not more than 3.8 m), and the competition weakened when the groundwater depth increased to 7.2 m.

We investigated the horizontal and vertical distribution of heavy metals (Hg, Pb, Zn, Cu, Cd, As, Ni, and Cr) in soils in the water source protection zone for Shanghai to study the origins of these metals, their connections with urbanization, and their potential risk posed on the ecosystem. Determination of metal concentrations in 50 topsoil samples and nine soil profiles indicated that Hg, Pb, Zn, and Cu were present in significantly higher concentrations in topsoil than in deep soil layers. The spatial distributions of Hg, Pb, Zn, and Cu and contamination hotspots for these metals in the study area were similar to those near heavy industries and urban built-up areas. Emissions from automobiles resulted in increased soil concentrations of Cu, Pb, and Zn along roadsides, while high concentrations of Hg in the soil resulted from recent atmospheric deposition. Calculation of the potential ecological risk indicated that the integrative risk of these heavy metals in most areas was low, but a few sites surrounding high density of factories showed moderate risks.

The elimination of herbicides in aquatic environment is influenced by various biotic or abiotic factors. Thus, efficient, more applicable, and flexible methods are in demand. Photodegradation has been applied to remove three main types of herbicides, phenylurea, triazine, and chloroacetanilide, from water, based on a series of TiO₂–reduced graphene oxide nanocomposites. Experimental results showed that the three types of herbicides could be mostly removed under simulated sunlight irradiation for 5 h with the as-prepared photocatalyst. Compared with pure TiO₂ or P25, the photodegradation efficiency has been markedly increased. Thus, the present work could promote a new strategy dealing with the pollution of herbicides in aquatic ecosystems.

The aim of this study is to evaluate the fluoride removal from contaminated water using a new adsorbent material of high efficiency to obtain drinking water. The ZrCl₄-graphene supported on vegetal activated carbon composite (G-ZrCl₄/VAC) was synthesized and characterized using transmission and scanning electron microscopy, N₂ physisorption, energy dispersive X-ray spectrometry, Fourier transform-infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Furthermore, the point of zero charge was determined. The G-ZrCl₄/VAC was evaluated for fluoride adsorptive removal from water under several operating conditions in batch system. The results indicated that fluoride adsorption by G-ZrCl₄/VAC is favored at low pH values with the maximum adsorption at pH 2, corresponding to 97.22% removal. Among the conditions of temperature and agitation evaluated, the best results were achieved at 30 °C and 130 rpm, with removal percentages equal to 47.78 and 48.48%, respectively. The equilibrium of the system was achieved in 5 h of operation. The pseudo-first order kinetic model was the one that best described the kinetic data, while the equilibrium data were best described by the Langmuir isotherm with maximum adsorption capacity equal to 3.89 mg g⁻¹. Therefore, the results obtained show that the material synthesized has a great capacity for adsorption and demonstrate the viability of use of G-ZrCl₄/VAC in the removal of fluoride to obtain drinking water.

Using ZnO nanoparticles, comparisons between sorption and sono-sorption efficiencies, equilibrium and kinetics in Direct Red 23 have been researched under the various experimental conditions. Pseudo-second-order model was practiced for the experimental data. The mechanism of the dye uptake was clarified based on the analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM). Brunauer-Emmett-Teller (BET) surface area and total pore volume of the nanoparticles were obtained. The highest Direct Red 23 (DR23) removal efficiencies by sorption and sono-sorption processes were determined as 78.6 and 96.8 %, respectively. Experimental data have been evaluated according to Langmuir, Freundlich and Dubinin-Radushkevich. The mean energies of sorption and sono-sorption processes were calculated to be 16.22 and 25.41 kJ/mol, respectively. Arrhenius equation was used to calculate the activation energies. ΔH° and ΔG° values indicated that sorption and sono-sorption processes were endothermic processes. But, negative free energy values of ΔG° indicated that sorption and sono-sorption processes were favoured at high temperatures.

Reactive extraction of phenol (0.053 mol kg⁻¹) from aqueous solution is carried out using two aminic extractants, trioctylmethylammoniumchloride (TOMAC) and trioctylamine (TOA) considering four concentrations (0.023 to 0.091 mol kg⁻¹) and dissolving them in solvents like nonane and isoamyl alcohol (IAA) at 298 K. The effects of extract type (TOMAC and TOA), their concentrations, and type of diluent on the separation efficiency of extraction have been determined. Data show that the neutral phenol molecule is more effectively extracted by TOA than TOMAC into the organic phase. Increase in the extractant concentration from 0.023 to 0.091 mol kg⁻¹ obviously enhances the recovery of phenol (2.3 times with nonane + TOMAC or TOA; 2.97 times with IAA + TOMAC; and 4.83 times with IAA + TOA). The equilibrium extraction results are presented in terms of distribution coefficient (D), degree of extraction (%E), and loading ratio (Z). Maximum value of D (=12.25) is obtained with TOA + IAA (0.091 mol kg⁻¹) which could extract 92.45 % of phenol from the water phase. A suitable mathematical model for the determination of equilibrium D is expressed by employing the mass action law. The equilibrium constant (K E) and the stoichiometric coefficient (n) of extraction are determined graphically. Also, the individual equilibrium constants (K ₁₁, K ₂₁, and K ₁₂) for the phenol-extractant complexes formed are estimated from the regression of the experimental values. The better extraction power of the TOA + IAA extract system is also shown from the estimated value of complexation constant (K E = 164.44). Phenol molecules form 1:1 and 2:1 and 1:1 and 1:2 solvates with nonane and IAA, respectively, with both the extractants.

Emerging organic contaminants in wastewater are usually analyzed by targeted approaches, and especially estrogens have been the focus of environmental research due to their high hormonal activity. The selection of specific target compounds means, however, that most of the sample components, including transformation products and potential new contaminants, are neglected. In this study, the fate of steroidal compounds in wastewater treatment processes was evaluated by a nontargeted approach based on comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry. The potential of the nontargeted approach to generate comprehensive information about sample constituents was demonstrated with use of statistical tools. Transformation pathways of the tentatively identified compounds with steroidal four-ring structure were proposed. The purification efficiency of the wastewater treatment plants was studied, and the distribution of the compounds of interest in the suspended solids, effluent water, and sludge was measured. The results showed that, owing to strong adsorption of hydrophobic compounds onto the solid matter, the steroids were mostly bound to the suspended solids of the effluent water and the sewage sludge at the end of the treatment process. The most abundant steroid class was androstanes in the aqueous phase and cholestanes in the solid phase. 17β-estradiol was the most abundant estrogen in the aqueous phase, but it was only detected in the influent samples indicating efficient removal during the treatment process. In the sludge samples, however, high concentrations of an oxidation product of 17β-estradiol, estrone, were measured.

Tropospheric ozone (O₃) is the air pollutant of most concern to vegetation at present. Ozone impacts on stomata are still controversial, as both decreased stomatal conductance and slow stomatal responses to environmental stimuli (namely, stomatal sluggishness) have been shown. We postulated that the light environment affects stomatal sluggishness. To concurrently manipulate O₃ and light conditions and measure gas exchange at leaf level, we developed an innovative O₃ exposure system by modifying a commercially available gas exchange system. We exposed the first trifoliate leaf of the O₃-sensitive genotype S156 of snapbean (Phaseolus vulgaris) to a 1-h O₃ exposure (150 ppb) under 1000 μmol m⁻² s⁻¹ photosynthetic photon flux density, so that stomata were fully open and O₃ uptake was maximized. Then, leaves were subjected to different light intensities (200, 1000, or 1500 μmol m⁻² s⁻¹) until a steady state was reached. As a metric of sluggishness, we quantified the stomatal responses to a sharp water stress generated by cutting the petiole at steady state. The results showed that O₃ exposure induced stomatal sluggishness only under high light (stomata needed 53 % more time to half stomatal conductance relative to steady state) and did not when the plants were under lower light intensities. We conclude that O₃-induced stomatal sluggishness may occur only in fully irradiated leaves, and suggest it is a minor response when entire crowns and canopies are assessed and a major reason of the higher O₃ sensitivity of sun leaves than of shade leaves.

There is global concern about the effects of decabromodiphenyl ether (BDE209) on environmental and public health. The molecular properties, biosorption, degradation, accumulation, and cellular metabolic effects of BDE209 were investigated in this study to identify the mechanisms involved in the aerobic biodegradation of BDE209. BDE209 is initially absorbed by wall teichoic acid and N-acetylglucosamine side chains in peptidoglycan, and then, BDE209 is transported and debrominated through three pathways, giving tri-, hepta-, octa-, and nona-bromodiphenyl ethers. The C–C bond energies decrease as the number of bromine atoms on the diphenyl decreases. Polybrominated diphenyl ethers (PBDEs) inhibit protein expression or accelerate protein degradation and increase membrane permeability and the release of Cl⁻, Na⁺, NH₄⁺, arabinose, proteins, acetic acid, and oxalic acid. However, PBDEs increase the amounts of K⁺, Mg²⁺, PO₄³⁻, SO₄²⁻, and NO₃⁻ assimilated. The biosorption, degradation, accumulation, and removal efficiencies when Brevibacillus brevis (1 g L⁻¹) was exposed to BDE209 (0.5 mg L⁻¹) for 7 days were 7.4, 69.5, 16.3, and 94.6 %, respectively.

From April 2008 to November 2009, a field decomposition experiment was conducted to investigate the effects of sediment burial on macro (C, N) and microelement (Pb, Cr, Cu, Zn, Ni, and Mn) variations in decomposing litter of Phragmites australis in the coastal marsh of the Yellow River estuary. Three one-off sediment burial treatments [no sediment burial (0 mm year⁻¹, S₀), current sediment burial (100 mm year⁻¹, S₁₀), and strong sediment burial (200 mm year⁻¹, S₂₀)] were laid in different decomposition sites. Results showed that sediment burials showed significant influence on the decomposition rate of P. australis, in the order of S₁₀ (0.001990 day⁻¹) ≈ S₂₀ (0.001710 day⁻¹) > S₀ (0.000768 day⁻¹) (p < 0.05). The macro and microelement in decomposing litters of the three burial depths exhibited different temporal variations except for Cu, Zn, and Ni. No significant differences in C, N, Pb, Cr, Zn, and Mn concentrations were observed among the three burial treatments except for Cu and Ni (p > 0.05). With increasing burial depth, N, Cr, Cu, Ni, and Mn concentrations generally increased, while C, Pb, and Zn concentrations varied insignificantly. Sediment burial was favorable for C and N release from P. australis, and, with increasing burial depth, the C release from litter significantly increased, and the N in litter shifted from accumulation to release. With a few exceptions, Pb, Cr, Zn, and Mn stocks in P. australis in the three treatments evidenced the export of metals from litter to environment, and, with increasing burial depth, the export amounts increased greatly. Stocks of Cu and Ni in P. australis in the S₁₀ and S₂₀ treatments were generally positive, evidencing incorporation of the two metals in most sampling times. Except for Ni, the variations of C, N, Pb, Cr, Cu, Zn, and Mn stocks in P. australis in the S₁₀ and S₂₀ treatments were approximated, indicating that the strong burial episodes (S₂₀) occurred in P. australis marsh in the future would have little influence on the stocks of these elements. With increasing burial depths, the P. australis was particularly efficient in binding Cu and Ni and releasing C, N, Pb, Cr, Zn, and Mn, implying that the potential eco-toxic risk of Pb, Cr, Zn, and Mn exposure might be very serious. This study emphasized the effects of different burials on nutrient and metal cycling and mass balance in the P. australis marsh of the Yellow River estuary.