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.

Ferrihydrite is often an initial precipitate resulting from the neutralization of Fe(III) solution, and it seems to be one of the products of acid mine drainage forming reactions. Since having the adsorption properties, ferrihydrite can be effective for the remediation of acid mine drainage. This study prepared fresh ferrihydrite by the rapid hydrolysis of Fe(III) ions and investigates its adsorptive behaviours toward Pb(II), Cu(II), and Zn(II). When the sorption data were presented in plot of percent sorbed versus pH, it was found that sorption is strongly dependent on the solution pH and increasing as expected at higher pH for all metal ions investigated. All the observed metal cation sorption began at pH values below zero point charge (ZPC) of ferrihydrite (pH = 7.8–8.0), and almost all removal are achieved at pH values lower than that related metal hydroxide obtained. Enhanced removal of metal ions, as the pH of the solution and initial metal ion concentration are increased, was attributed to surface precipitation of metal hydroxide. The existence of ferrihydrite and adsorption of metal ions onto surfaces are favouring surface precipitation of metal ions at lower pH values than that for metal ion only. Depending on the pH of the solution and initial metal ion concentration, more than one mechanism such as adsorption by complexation and surface precipitation was responsible for the removal.

The presence of trace of pharmaceutical compounds (PhACs) in groundwater and in drinking and superficial waters is a major public health concern. Recently, various advanced treatment technologies have been studied to remove these kinds of pollutants; among them, combined treatments based on UV light appear to be more eco-friendly and with very interesting removal efficiencies if properly modified. In this paper, the removal of Ibuprofen (IBP) from synthetic water streams was investigated by using a lab-scale experimental device consisting of a batch reactor equipped with a lamp emitting monochromatic UV light (254 nm; 400 mJ m⁻²). The IBP initial concentration (C IBP ⁰) was 45.9 mg L⁻¹. Two sets of experiments were carried out; the first one was aimed at studying the IBP concentration as a function of time, at different volumes of treated solution; the second one was aimed at exploring the effect of pH on IBP degradation as a function of time. The results obtained show that the concentration of IBP decreases along with treatment time, with a negative effect of the treated volume, i.e., smaller volumes, that is lower liquid heights, are more easily degraded. Moreover, the higher the pH, the better the IBP degradation; actually when pH increases from 2.25 to 5.51 and finally to 8.25, the IBP concentration, after an hour of treatment, decreases respectively to 45, 34, and 27 % from its initial value. A reaction mechanism is suggested, which well describes the effects of volume and pH on the experimentally measured IBP degradation.

Brazil is an important country within the global mineral industry. The main reserves of phosphate rock in Brazil are contained in the states of Goiás and Minas Gerais, at the Catalão and Tapira cities, respectively. Atmospheric inputs due to the mining of phosphate rock may have various effects on human health in areas near these types of mines. Thus, this work evaluated the influence of phosphate mining on the chemical composition and annual atmospheric deposition in Catalão (GO) and Tapira (MG), Brazil. The pH of rainwater was 6.90 in Catalão and 6.80 in Tapira. The ionic concentrations (in μeq/L) at both study sites decreased in the following order: Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ for cations and HCO₃ ⁻ > NO₃ ⁻ > SO₄ ²⁻ > PO₄ ³⁻ > F⁻ > Cl⁻ for anions. High Ca²⁺ content indicates that Ca²⁺ contributes to the neutralisation of the rainwater pH in both of the areas studied. The annual atmospheric deposition of NO₃ ⁻ and SO₄ ²⁻ can be attributed to the use of diesel-powered trucks in and around mining areas. Soil dust derived is responsible for the annual atmospheric deposition of Na⁺ and K⁺. Phosphate mining activities are the main source of the annual atmospheric deposition of PO₄ ³⁻ and F⁻.

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.

The presence of insecticides in the waterways of the municipality of Ouro Branco, MG, Southeastern Brazil, has become a public health problem. Recent research correlates the presence of these toxins in the water to the high indexes for hypertension and abortions occurring in the rural area. These insecticide residues are only slightly concentrated in the water, and as such, it is necessary to search for and optimize analytic methods that are capable of detecting these very low concentrations. To define the method that presents the best detectability for the organochlorine chlorpyrifos, one of the most used pesticides in the area, sample extraction techniques such as liquid–liquid extraction with low temperature partition (LLE-LTP) and headspace solid-phase microextraction (HS-SPME) were used, followed by gas chromatography analysis with electron capture detection (GC-ECD). Full factorial design 2⁴ and the Doehlert matrix were used to optimize both extraction techniques. The results displayed that HS-SPME-GC-ECD was the method that presented the best performance for determining the presence of chlorpyrifos in the water. The optimum condition was defined at the extraction time and temperature of 60 min and 85 °C, respectively, with a sample volume of 11 mL and Na₂HPO₄ concentration of 0.04 mol/L. The optimized method was validated for the principal figures of merit. The method displayed linearity with R ² equal to 0.992 and detection limit (LOD) and quantification limit (LOQ) of 0.50 and 1.67 μg/L, respectively. The results indicate that the HS-SPME-GC-ECD technique proposed is efficient for determining the presence of chlorpyrifos in water, and analyses of the collected sample indicated the presence of chlorpyrifos in water bodies in the rural zone of Ouro Branco in concentrations within detection and quantification limits.

Increased emissions of fluoride into the atmosphere contribute to reducing the sustainability of agricultural systems worldwide. In order to improve the understanding of the factors behind such phenomenon, varieties of citrus (Citrus spp.), Valencia sweet-orange, Ponkan mandarin, and Lisbon lemon and coffee (Coffea spp.), Obatã, Catuai, and Apoatã, were treated with fluoride nebulization. The trees were exposed to nebulization for 60 min inside a chamber by using medium (0.04 mol L⁻¹) and high (0.16 mol L⁻¹) doses of fluoridic acid (HF) during three nonconsecutive days in a single week, for a total of 26 days of exposure during the experiment. Sixty days after beginning nebulization, we evaluated leaf gas exchange, (ultra)structural organization, tree growth, and fluoride and nutrient concentrations in plant tissue. Photosynthesis and leaf dry mass of citrus and coffee varieties were affected differently by fluoride toxicity, and based on the tolerance index (relative leaf dry mass of control versus leaf dry mass of trees treated with 0.16 mol L⁻¹ HF), the order of sensitivity for the varieties of each species was as follows: for citrus, lemon > mandarin > sweet-orange; and for coffee, Apoatã > Catuaí > Obatã. The ability of the trees to control fluoride absorption most likely explained this contrast in sensitivity among varieties because both photosynthesis and leaf growth were negatively correlated with leaf fluoride concentration. Although disorganization of the thylakoids, degeneration of vascular cells, and disruption of the middle lamella occurred in leaves of all varieties exposed to fluoride, the more severe damage was observed in those with greater sensitivity to the pollutant (i.e., lemon and Apoatã coffee). Taken together, these results provided insights into the factors that explain poor performance of citrus and coffee trees under fluoride pollution and also revealed the traits driving the tolerance of these crops such a limiting condition, which included a combination of the following: (i) reduced fluoride absorption, (ii) increased photosynthesis, and (iii) improved maintenance of the ultrastructural organization of leaves.

The use of reclaimed water (RW) for irrigation alleviates agricultural water shortages. However, N₂O emissions and N fertilizer transformations in soils irrigated with RW under different N fertilizer types and soil moisture contents are poorly understood. A 216-h laboratory incubation experiment was conducted to evaluate the effects of irrigation water types (RW and fresh water, FW), N fertilizer types (¹⁵N-labeled KNO₃ and (NH₄)₂SO₄), and soil moisture contents at 40, 60, and 90 % water-filled pore space (WFPS) on N₂O emissions and N fertilizer transformations in intact soil cores. The results showed that cumulative N₂O emissions ranged from 3.78 to 36.30 mg N m⁻², and fertilizer-derived N₂O losses accounted for 0.14–2.44 % of N fertilizers, while fertilizer-derived N residues (NO₃ ⁻-N + NH₄ ⁺-N) accounted for 10.16–26.95 % of N fertilizers. The N₂O emissions at 40 % WFPS and fertilizer-derived N residues at 60 % WFPS in soils irrigated with RW were significantly (10.98 and 20.95 %, respectively) higher than those irrigated with FW, while fertilizer-derived N₂O losses at 60 % WFPS in soils irrigated with RW were 10.26 % higher than those irrigated with FW. The N₂O emissions and fertilizer-derived N₂O losses in soils amended with (NH₄)₂SO₄ at 40 and 60 % WFPS were significantly (26.61–178.84 %) larger than those amended with KNO₃, while fertilizer-derived N residues in soils amended with KNO₃ were significantly (41.47 %) higher than those amended with (NH₄)₂SO₄. The N₂O emissions significantly increased with increasing soil moisture content. Our results indicate that N fertilizer types and soil moisture contents are the two important factors regulating N₂O emissions and N fertilizer transformations. When RW irrigation is used, controlling soil moisture contents within 41 and 60 % WFPS (the optimum is 46 % WFPS) and application of KNO₃ can reduce N₂O emissions and fertilizer-derived N₂O losses, and correspondingly increase fertilizer-derived N residues, which can contribute to climate change mitigation.

The study delineates the investigation to determine the adsorption and desorption behaviour of Pretilachlor in three soils of Punjab with varying physicochemical characteristics using batch equilibration techniques. Kinetics of adsorption followed a pseudo-second-order model (R ² > 0.99) and adsorption–desorption data fitted well to the Freundlich equation for the three soils. L-type isotherms were obtained for the adsorption process, which indicated high affinity between Pretilachlor and adsorption sites. The magnitude of logK Fₐdₛ values for the three soils ranged from 0.887–1.226 μg¹⁻¹/ⁿ g⁻¹ mL¹/ⁿ and the order of adsorption was clay loam > sandy loam > loamy sand. Desorption of Pretilachlor was concentration dependent and in three desorption cycles ranged from 5.04 to 56.03 % in loamy sand, 3.14 to 23.12 % in sandy loam and 1.63 to 18.64 % in clay loam soil indicative of difficulty in the release of strongly adsorbed Pretilachlor. The removal of organic matter by hydrogen peroxide (H₂O₂) oxidation increased the adsorption of Pretilachlor in three Punjab soils. Pretilachlor desorption was hysteretic in the original as well as H₂O₂-treated soils. It could therefore be concluded that the adsorption was controlled by clay minerals and desorption of Pretilachlor in soils was controlled by the organic matter.

Fluoride retention from water is nowadays a serious health problem. This study reports the potential of a newly developed nano-hydrotalcite/hydroxyapatite (n-HT/HAp) composite, and its constituent materials, hydrotalcite (HT) and hydroxyapatite (HAp), in fluoride removal. Calcined hydrotalcites (cHT) showed a remarkable fluoride removal ability from water through memory effect mechanism. HAp, the mineral compound of bones, adsorbs fluoride as well but through ion exchange mechanism. Fluoride substitutes hydroxyls to produce fluorapatite. Among the tested calcined hydrotalcites, cHT Mg-Al (4:1) sample, composed of magnesium divalent cation to aluminum ratio of 4, was identified as the best-performing hydrotalcite. The differences among cHT samples in fluoride removal capacities are attributed to hydrotalcite composition as well as to particle size. The performance of these materials is compared with that of n-HT/HAp composite whose main features are basic acidic material and not yet tested in fluoride retention. Interestingly, n-HT/HAp also performs best, 98 %, slightly higher than the best cHT Mg-Al (4:1) sample with 97 % fluoride removal efficiency from such a high initial fluoride solution of 20 mg/L at 10 g/L dose, yielding the final residual fluoride concentrations of 0.36 and 0.6 mg/L, respectively; both meet the WHO standard for drinking water. Besides, the uncalcined hydrotalcite constituent added virtue to the advantage of using n-HT/HAp in fluoride removal as the efficiency was compensated by the nanometric size of the hydrotalcite particle.