The current study explores the relationship between water resources and tourism in South Asia for the period of 1995–2017. The study employs the CIPS unit root test for stationarity of the variables and the CD test for cross-sectional dependence among cross-sectional units. As for the long-run parameters, a novel technique, known as dynamic common correlated effect (DCCE) model, is used which was recently developed by Chudik and Pesaran (J Econ 188:393–420, 2015b). The outcomes from the DCCE method suggest that water resources have a positive impact on tourism in South Asia. It is also proven that ignoring cross-sectional dependence among the cross-sectional units may bring about misleading outcomes. The findings of the study can be helpful for policymakers to understand the role of water resources in boosting tourism and contributing to the economic prosperity of South Asian countries.

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid) is an extensively used organoarsenic feed additive. The effective removal of arsenic from roxarsone degradation before discharging is of great importance for controlling artificial arsenic pollution in aquatic environment. In this study, a bifunctional TiO₂/ferrihydrite (TiO₂/FeOOH) hybrid was synthesized by a hydrothermal method for the simultaneously photocatalytic degradation of roxarsone and adsorption removal of released arsenic. The analysis of the prepared TiO₂/FeOOH by field-emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), Raman spectra, X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and X-ray photoelectron spectroscopy (XPS) confirmed the successful formation of the hybrid of crystalline TiO₂ and no crystalline FeOOH. TiO₂/FeOOH hybrid had better adsorption capacity for As(V) than roxarsone. Compared to TiO₂, the TiO₂/FeOOH hybrid exhibited much superior UV-driven photocatalytic activities for roxarsone degradation. After 12 h irradiation, more than 96% of roxarsone was degraded by 1:1 TiO₂/FeOOH hybrid, and the released As(V) was simultaneously removed from the solution. The residual As(V) concentration was lower than 0.02 mg L⁻¹. The reusability test indicated that TiO₂/FeOOH hybrid had excellent stability and reliability. The possible mechanism of roxarsone degradation and released inorganic arsenics removal by this hybrid was also proposed. These results clearly indicated that the TiO₂/FeOOH hybrid could be used for the removal of roxarsone and its degradation product.

The potential of cassava (Manihot esculenta Crantz.) for simultaneous Hg and Au phytoextraction was explored by investigating Hg and Au localization in cassava roots through Micro-Proton Induced X-Ray Emission, High-Resolution Transmission Electron Microscopy (HR-TEM) and X-Ray Diffractometry (XRD). The effect of Hg and Au in the cyanogenic glucoside linamarin distribution was also investigated using Matrix Assisted Laser Desorption Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (MALDI-FT-ICR-MS) imaging. Hg was located mainly in the root vascular bundle of plants grown in 50 or 100 μmol L⁻¹ Hg solutions. Au was localized in the epidermis and cortex or in the epidermis and endodermis for 50 and 100 μmol L⁻¹ Au solutions, respectively. For 50 μmol L⁻¹ solutions of both Hg and Au, the two metals were co-localized in the epidermis. When the Hg concentrations were increased to 100 μmol L⁻¹, Au was still localized to a considerable extent in the epidermis while Hg was located in all root parts. HR-TEM and XRD revealed that Au nanoparticles were formed in cassava roots. MALDI-FT-ICR-MS imaging showed linamarin distribution in the roots of control and plants and metal-exposed plants thus suggesting that linamarin might be involved in Hg and Au uptake and distribution.

Bushehr, a port along the northern part of the Persian Gulf, has repeatedly encountered dust storms in recent years but there is not been a comprehensive study on the PM₂.₅ contents in this region. The present study reports the characteristics and health risks of atmospheric PM₂.₅-bound heavy metals (HMs) in Bushehr from December 2016 to September 2017. A total of 46 samples were analyzed, and a high volume air sampler equipped with quartz fiber filters was used for sampling. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was also used for HMs analyses. Risk assessment and hazard index (HI) of these metals were computed by using USEPA’s exposure parameters. The results showed that the average 24-h mass concentration of PM₂.₅ ranged from 22.09 to 292.45 μg/m³. The results also indicated that 95.65 and 82.61% of the samples were higher than WHO and EPA guidelines for 24-h PM₂.₅. Also there was no statistically significant relationship between wind direction and PM₂.₅.The average concentration levels of seven measured metals (Cd, Co, Cr, Fe, Ni, Pb, and V) in the PM₂.₅ samples were in the range of 6.03 ng/m³ to 1335.94 ng/m³, and the order of their concentration was Fe > Ni > Pb > Cr > Cd > V > Co. Principal component analysis (PCA) showed that PM₂.₅-bound heavy metals were categorized in three groups. The ecological risk level of calculated metals was very significant, and the major contribution of the ecological risk was related to Cd. The highest HQ in children and adults was related to Cr, and overall HI in children was higher than adults. Also the RI values of Cr in both groups of children and adults were indicated high risk of developing cancer in human.

The vegetation plays important role in urban environment and associated ecology. Urban vegetation experienced various changes due to biotic and natural interference which alter the vegetation structure, function and ecology. The present study deals with the assessment of shrub species structure, diversity, biomass, volume, C storage and CO₂ mitigation potential in an urban setup. Total four sites were selected, viz., east, west, north and south directions of Ambikapur City. A sum of eight shrub species representing seven families was recorded in Ambikapur City area. The highest representatives were recorded towards east direction (seven species with six families) and lowest towards south direction (five species with five families). The total density of shrubs ranged between 230 and 570 individual ha⁻ ¹ being highest at east direction and least at south direction. The higher diversity was found at east direction. The shrub biomass was ranged between 0.999 and 2.603 t/ha being highest at north direction and lowest at east direction. The shrub volume, C storage and CO₂ mitigation values reflected similar trend as in case of shrub biomass. The shrub volume, C stock and CO₂ mitigation values were ranged from 0.141 to 0.250 m³/ha, 0.437 to1.132 t/ha and 1.597 to 4.156 t/ha, respectively, among the various sites. The species like Cestrum nocturnum and Nerium oleander are found to be potential in terms of various ecological services such as biomass, C storage and CO₂ mitigation in different sites. However, Lantana camara was also found to be potential species under urban setup which can be utilized for its various ecological functions. Further, it was found that the contribution of the non-native species was higher over native species in terms of stand density, basal area, biomass, C stock, volume and CO₂ mitigation potential among different study sites.

A total of 161 water samples were collected from five large and medium-sized city rivers and residential tap waters, Xi’an and Yan’an in Shaanxi province, Xining in Qinghai province, Lanzhou in Gansu, and Urumqi in Xinjiang province, within arid and semi-arid area (NW China). The pH, EC parameters, and concentrations of 10 major ions (F⁻, Cl⁻, HCO₃⁻, NO₃⁻, SO₄²⁻, NH₄⁺, K⁺, Na⁺, Mg²⁺, Ca²⁺) in the drinking waters (DWs) and surface waters (SWs) were analyzed to determine the ion chemistry, geochemical process, and potential anthropogenic input sources and to assess the water quality for drinking, domestic, and irrigation purposes. Durove diagrams and Gibbs diagram indicated that the ions Ca²⁺ and HCO₃⁻ dominant in DWs from Xi’an and Xining were of Ca²⁺-(HCO₃⁻ + SO₄²⁻) type, while sulfate and Na⁺ dominant in SWs, and Na⁺/K⁺-SO₄²⁻ type was for Yan River in Yan’an and Peaceful Canal in Urumqi, their water chemistry influenced by evaporation and rock dominance, and evaporation and fractional crystallization, respectively. Meanwhile, Na⁺/K⁺/Ca²⁺-HCO₃⁻/SO₄²⁻ type dominated in Huang River in Xining and Yellow River in Lanzhou, which dominated by rock weathering. The quality assessments showed that in general the drinking waters were suitable for domestic purposes. However, the high values of NO₃⁻ at some sites influenced by agricultural and industrial inputs made it unsafe for drinking and demand detailed regional drinking water investigations. The assessment of SWs showed that the waters from Yan River in Yan’an and Yellow River in Lanzhou and Huang River in Xining would be used for irrigation. However, high values of SAR, Na%, RSC, and EC at sites in Peaceful Canal restricted suitability for irrigation, and not recommended for drinking water sources. It was noted that for the sustainable development of surface water, a reduction of discharge water from human activities and/or an increase in the fresh water inflow to the surface were needed.

Agricultural activity, especially the increasing use of pesticides, is considered one of the main reasons for the decline of amphibian populations. Mancozeb (MCZ) is one of the most used fungicides worldwide, despite its ancient use and toxicity demonstrated in different taxa. However, there is limited information about the effects of MCZ in amphibians, which are keystones of riparian ecosystems. For species conservation purposes, it is essential to identify the most sensitive developmental period(s) of a given species to a xenobiotic. We evaluated the toxicity of a commercial fungicide of mancozeb, (80% active ingredient) on the early development of the common South American toad Rhinella arenarum (Anura, Bufonidae). Embryos from early blastula (S.4) and larvae from complete operculum (S.25) stages were exposed to a wide range of MCZ concentrations during acute, subchronic and chronic exposure (up to 504 h) periods. The toxicity profiles for lethal and sublethal effects were performed. At all exposure times, MCZ was more toxic to embryos, for instance, NOEC 504 h were 0.01 and 0.05 mg MCZ/L for embryos and larvae, respectively. Thus, embryo sensitivity was 5-fold higher than larvae. A Teratogenic Index of 14 indicated the significant teratogenic potential of this fungicide. Among sublethal effects, embryos exhibited a wide range of abnormalities with high incidence. The ecological risk assessment demonstrated that the estimated Risk Quotient value for Rhinella arenarum embryos at chronic exposure was higher than the Level of Concern value, which warns about the potential risk of MCZ for this native species.

Increasing entrance of aluminum chloride (AlCl₃) in many fields exposes human beings to its biotoxicity. Thereby, the present study assesses the potential ameliorative role of curcumin phytosome (CP) on AlCl₃-induced hepatotoxicity. Rats were divided into four groups (n = 6): group 1 served as control; group 2 received CP (200 mg CP/kg b.wt) for 21 days; group 3 injected three doses of AlCl₃ (30 mg/kg/body weight) every 5 days intraperitoneally; group 4 received CP for 7 days prior to AlCl₃ and then received CP concurrently with AlCl₃ for another 14 days. AlCl₃ markedly increased (P < 0.05) the concentrations of AST, ALT, ALP, LDH, total bilirubin, and LPO as well as depleted (P < 0.05) albumin, GSH, SOD, and GPx stores in comparison to the control group. These biochemical alterations supported by the lesion observed in histological sections, increasing the expression of caspase-3 and decreasing the expression of Bcl-2. Treatment with CP modulates the hepatic dysfunction, boosting the endogenous antioxidant status, downregulating the expression of caspase-3, and upregulating the expression of Bcl-2. This hepatic ameliorative effect may be mediated by the ability of CP to repair the oxidant/antioxidant equilibrium rather than its ability to suppress apoptosis.

Bacterial denitrification is widely documented at neutral pH in order to improve the removal of nitrate in wastewater treatment processes. However, certain industrial contexts generate alkaline waste and effluent containing nitrate that must be denitrified. To obtain more information on denitrification at alkaline pH, this study evaluated the possibility of adapting a neutrophilic denitrifying strain, Paracoccus denitrificans, to alkaline pH. Firstly, P. denitrificans’ denitrifying activity was evaluated without acclimation in batch bioreactors at pH 7.0, 8.0, 9.0 and 10.0. Then, two acclimation methods using successive batch bioreactors and a continuous bioreactor allowed P. denitrificans to be gradually exposed to alkaline pH: from 8.5 to 11.2 in 26 and 72 days respectively. Results showed that P. denitrificans could grow and catalyse nitrate reduction (i) at pH 9.0 without acclimation, (ii) at pH 10.5 in successive batch cultures with progressively increasing pH and (iii) at pH 10.8 in continuously fed culture with a hydraulic retention time (HRT) of 8 days. It was shown that denitrification affected the pH despite the presence of carbonate buffering of the P. denitrificans growth medium. With acetate as an electron donor, the pH of a carbonate buffered medium tends towards pH 10 during the process of denitrification. Graphical abstract

The aim of this study was the valorization of titanium flakes (waste) from titanium and titanium alloy ingot production factories and using in applications related to metals recovery as retention bed for some trace metals. The titanium flakes were anodized for surface nanostructuration with TiO₂ nanotubes and then annealed in order to increase the surface stability. The nanostructured titanium flakes were loaded and pressed in a retention column linked with inductively coupled plasma spectrometer (ICP-OES). This system allowed determination of trace elements such as beryllium, lanthanum, lutetium, and ytterbium from sample solutions. Beryllium recovery percentage was over 90%, while lanthanides have just a satisfactory recovery percentage (about 65% Yb and Lu and 50% La). The TiO₂ nanotube architecture was not affected during utilization being able to perform for a long time. A thermodynamic and kinetic study was done for beryllium due to its successful adsorption recovery percentage. The obtained results showed that the titanium waste is a promising material for rare earth and relatively rare earth elements retention and recovery. Graphical abstract Graphical abstract