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.

A groundwater flow and mass transport model simulated the remediation capability of non-pumped wells with filter media placed in backfilled trenches in homogeneous and heterogeneous aquifers. For each of five homogeneous and heterogeneous aquifer settings, the model identified a base configuration of wells for a backfill hydraulic conductivity equal to the mean of the aquifer (1.5 m/d). Base configurations comprised the least number of wells necessary to contain and remove a contaminant plume. For each setting, the model also simulated base configurations with backfill hydraulic conductivity one and two orders of magnitude lower and one and two orders of magnitude higher than the mean of the aquifer. In general, backfill with a hydraulic conductivity equal to the mean of the aquifer, or slightly higher, outperformed other scenarios.

Suspended particles in water are a major concern in global pollution management. They affect the appreciation of water due to clarity, photosynthesis, and poor oxygen environment rendering water unsuitable for aquatic animals. Some suspended materials contain functional groups capable of forming complex compounds with metals making them available for poisoning. Such material promotes the growth of bacteria and fouling that give rise to unpleasant taste and odor of the water and thus requires removal. Removal of suspended solids is normally achieved through sedimentation or filtration. However, some suspended colloidal particles are very stable in water and cannot settle while others are able to pass through the filter due to small size, hence difficult to remove. This study investigated the use of triethanolamine-modified maize tassels to form a flocculent for their removal. The modified maize tassels were characterized using Fourier transform infrared (FTIR), and it was found that the triethanolamine was anchored within the cellulose structure of the maize tassels. Clarification parameters such as settling time, reagent dosage, and pH were investigated. The best clarification was at a pH of 6.0 with clearance being less than in 30 min. The optimal flocculent dosage was found to be 3.5 ml of the material, showing that the material has a potential of enhancing clarity in polluted water.

The aim of this work is to assess the occurrence of Polycyclic aromatic hydrocarbons (PAHs) in the Tisza River and its main Romanian tributaries (Vişeu River and Iza River) and to establish the origin (pyrogenic/petrogenic) of pollution sources. Fifteen PAHs were investigated in surface water and sediment samples collected from three selected sampling point. The target compounds were isolated from the matrices by solid phase extraction for water samples and by ultrasound-assisted extraction for the sediment samples, respectively. The quantification of the target compounds was performed by HPLC coupled with a fluorescence detector. PAH diagnostic ratios, as the abundance ratio of 2–3 ring hydrocarbons to 4–6 ring hydrocarbons (LMW/HMW), ANT/(ANT + PHE), FLT/(FLT + PYR), B[a]A/(B[a]A + CHR), and IND/(IND+ B[g,h,i]P) were used as a tool for identification and assessment of the pollution emission sources. The results of the study showed that in the studied area, the total concentrations of PAHs detected in water samples ranged from 1.22 to 260.26 ng L⁻¹, while those in sediment samples varied from 4.94 to 10.62 μg kg⁻¹. Regarding the PAH pattern, mixed sources of pollution (pyrogenic and petrogenic) occur in both water and sediment samples. Thus, leaks of petroleum products and biomass, coal, and petroleum combustion are the main sources of pollution identified into the studied area.