Impact of anthropogenic activity on the chemical regime of underground waters

The article is dedicated to definition of the tendency to change and pattern of formation of the chemical regime of underground waters in the Turyanchay-Girdimanchay interfluve in the Shirvan steppe, Azerbaijan as a result of anthropogenic activity. The subsoil waters studied are spread in the zone between the Turyanchay and Girdimanchay rivers. From 1930 to 2019 based on analysis of the observation of the chemical regime of subsoil waters, the natural regime of the groundwaters in the studied area strongly changed as a result of irrigation and construction works. In 1930 the average mineralization degree of subsoil waters was 26.8 gram/liter in the zone. The level of subsoil waters approaches the surface and is exposed to strong evaporation as a result of irrigation and filtration of waters from irrigation channels. Consequently, the mineralization rate of subsoil waters increased and mass secondary salinization process occurred in the irrigated lands. The average mineralization degree of subsoil waters was 33.6–34.5 gram/liter in the research zone in the 1960s-1970s. Collector-drainage networks were built and basic washing of soils is carried out in order the prevent secondary salinization and regulate the level of subsoil waters. After the 1970s the mineralization rate of subsoil waters began to decrease due to basic washing, intensive irrigation and the activity of the collector-drainage network.The average mineralization degree decreased to 15.1 gram/liter. The mineralization degree of the water in the Main Shirvan Collector which takes subsoil waters formed in the zone with 253,000 hectares and which discaharges them into the Caspian Sea decreased more than 3 times in comparison with 1995. At present the mineralization degree of collector water is 1.8–2.5 gram/liter while its mineralization degree was 8.81 gram/liter in 1995. Formation of the process in a favourable direction enchances the potential of using collector water for irrigation, technical and other purposes and creates a basis for elimination of water deficiency in drought years. The research shows that anthropogenic activity mainly plays an important role in formation of the chemical regime of subsoil waters.

Heterogeneous Photocatalysis of Metronidazole in Aquatic Samples

Metronidazole (MET) is a commonly detected contaminant in the environment. The compound is classified as poorly biodegradable and highly soluble in water. Heterogeneous photocatalysis is the most promoted water purification method due to the possibility of using sunlight and small amounts of a catalyst needed for the process. The aim of this study was to select conditions for photocatalytic removal of metronidazole from aquatic samples. The effect of catalyst type, mass, and irradiance intensity on the efficiency of metronidazole removal was determined. For this purpose, TiO2, ZnO, ZrO2, WO3, PbS, and their mixtures in a mass ratio of 1:1 were used. In this study, the transformation products formed were identified, and the mineralization degree of compound was determined. The efficiency of metronidazole removal depending on the type of catalyst was in the range of 50–95%. The highest MET conversion (95%) combined with a high degree of mineralization (70.3%) was obtained by using a mixture of 12.5 g TiO2–P25 + PbS (1:1; v/v) and running the process for 60 min at an irradiance of 1000 W m−2. Four MET degradation products were identified by untargeted analysis, formed by the rearrangement of the metronidazole and the C-C bond breaking.

New insights on the UV/TiO2 photocatalytic treatment of thiomersal and its 2-sulfobenzoic acid product

Background: Thiomersal (TM), a complex between 2-mercaptobenzoic acid (2-MBA) and ethylmercury (C2H5Hg+), is an antimicrobial preservative used in immunological, ophthalmic, cosmetic products, and vaccines. Objective: TM has been treated by UV/TiO2 photocatalysis in the presence or absence of oxygen at acidic pH. C2H5Hg+, 2-MBA, and 2-sulfobenzoic acid (2-SBA) were found as products. A 2-SBA photocatalytic treatment was undertaken to study sulfur evolution. Methods: Photocatalytic runs were performed using a UVA lamp (λmax = 352 nm), open to the air or under N2. A suspension of the corresponding TM or 2-SBA salt and TiO2 was prepared, and pH was adjusted. Suspensions were stirred in the dark for 30 min and then irradiated. TM, 2-MBA, 2-SBA, and C2H5Hg+ were quantified by HPLC, sulfur by TXRF, and the deposits on the photocatalyst were analyzed by chemical reactions. The mineralization degree was followed by TOC. Sulfate was determined using BaCl2 at 580 nm. Results: Photocatalytic destruction of TM and total C2H5Hg+ was complete under N2 and air, but TM degradation was much faster in air. The evolution of TM and the products followed a pseudo-first-order kinetics. Conclusion: TiO2-photocatalytic degradation is a suitable technique for the treatment of TM and its degradation products. In contrast to other organomercurial compounds, TM degradation is faster in the presence of O2, indicating that the oxidative mechanism is the preferred pathway. A significant TM mineralization (> 60%, NPOC and total S) was obtained. TM was more easily degraded than 2-SBA. Sulfate was the final product.

Effect of Cu doping on the photocatalytic activity of InVO4 for hazardous dye photodegradation under LED light irradiation and its mechanism

Cu doped InVO4 (xCu-InVO4 (x = 0.06–0.15 wt %) was synthesized by a facile one-pot hydrothermal method for the removal of methylene blue (MB) under LED light irradiation. The X-ray photoelectron spectroscopy (XPS) analysis indicated the coexistence of V5+ and V4+ species due to the O-deficient nature of the xCu-InVO4. The synthesized photocatalysts displayed a morphology of spherical and square shaped particles (20–40 nm) and micro-sized rectangle rods with a length range of 100–200 μm. The xCu-InVO4 exhibited superior adsorption and photodegradation efficiency compared to pristine InVO4 and TiO2 due to the presence of O2 vacancies, V4+/V5+ species, and Cu dopant. The optimum reaction conditions were found to be 5 mg L−1 (MB concentration), pH 6, and 100 mg of photocatalyst mass with a removal efficiency and mineralization degree of 100% and 96.67%, respectively. The main active species responsible for the degradation of MB were •OH radicals and h+. Reusability studies indicated that the 0.13Cu-InVO4 was deactivated after a single cycle of photocatalytic reaction due to significant leaching of V4+ and Cu2+ species.

Study on Ecological Threshold of Groundwater in Typical Salinization Area of Qian’an County

A suitable groundwater level is an important condition to maintain the stability of the vegetation community, especially in arid and semi-arid areas. The surface of Qian’an County in Western Jilin Province is often accompanied by salinization due to the influence of natural and human factors. In order to maintain the healthy development of ecological vegetation and reduce the risk of soil salinization, the concept of an ecological threshold of groundwater level is proposed, and two methods are used to determine the reasonable ecological threshold of groundwater. (1) Based on field investigation and indoor experiment, the data layer of soil texture, land use type and groundwater mineralization degree in the research area was established by using remote sensing technology and GIS technology. According to the thickness of vegetation root layer and the height of capillary rise of different soil and water types, the influence of groundwater salinity is considered, and the sum of the two is taken as the ecological threshold of groundwater in the study area. The reasonable threshold value of suitable growth of various vegetation crops is 3.76~5.66 m. (2) According to the relationship between the normalized vegetation index (NDVI) and the groundwater buried depth and phreatic salt, the groundwater buried depth and the mineralization degree under the best vegetation cover are analyzed as follows: the buried depth of groundwater is between 4.8 m and 6.1 m, and the salinity of groundwater is between 0.37 and 1.25 g/L, which are reasonable groundwater properties in the study area of the ecological threshold. This result not only enriches and broadens the content of groundwater research, but also helps to predict the prospect of water resource development.

Photocatalytic Decomposition of Acetaldehyde on Different TiO2-Based Materials: A Review

Purification of air from the organic contaminants by the photocatalytic process has been confirmed to be very perspective. Although many various photocatalysts have been prepared and studied so far, TiO2 is still the most commonly used, because of its advantageous properties such as non-toxicity, relatively low cost and high stability. Surface modifications of TiO2 were extensively proceeded in order to increase photocatalytic activity of the photocatalyst under both UV and visible light activations. The intention of this review paper was to summarize the scientific achievements devoted to developing of TiO2-based materials considered as photocatalysts for the photocatalytic degradation of acetaldehyde in air. Influence of the preparation and modification methods on the parameters of the resultant photocatalyst is reviewed and discussed in this work. Affinity of the photocatalyst surfaces towards adsorption of acetaldehyde will be described by taking into account its physicochemical parameters. Impact of the contact time of a pollutant with the photocatalyst surface is analyzed and discussed with respect to both the degradation rate and mineralization degree of the contaminant. Influence of the photocatalyst properties on the mechanism and yield of the photocatalytic reactions is discussed. New data related to the acetaldehyde decomposition on commercial TiO2 were added, which indicated the different mechanisms occurring on the anatase and rutile structures. Finally, possible applications of the materials revealing photocatalytic activity are presented with a special attention paid to the photocatalytic purification of air from Volatile Organic Compounds (VOCs).

Sonochemical degradation of bisphenol A using persulfate activated by hematite nanoparticles (HNPs/PS)

In this study, hematite nanoparticles were used as persulfate activator for sonocatalytic degradation of bisphenol A (BPA). The physicochemical properties of the synthesized nanoparticles were investigated by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) analysis. The effect of different operational parameters such as pH, nanoparticle dosage, persulfate concentration, and ultrasonic power on catalytic activity were evaluated. The BPA degradation rate was improved when US irradiation was used simultaneously with HNPs for activating PS. According to the results, 98.94% of BPA (10 mg/L) was degraded within 15 min reaction time at 4 mM persulfate and 0.01 g/L α-Fe2O3 under ultrasonic irradiation of 250 W. The mineralization degree of BPA was determined by chemical oxygen demand (COD). 36.98% mineralization of BPA was achieved under optimum conditions. The quenching tests were done in the presence of different scavenger compounds. The results showed that both hydroxyl and sulfate radicals were reactive species in BPA degradation. According to the results of reusability test, the degradation efficiency was decreased to 86.34% indicating that HNPs can be recycled several times. Based on the results, all of the anions had the inhibitory effect on BPA degradation and most of the effect was related to hydrogen phosphate ions. The results showed that ultrasonic/hematite/ persulfate (US/HNPs/PS) process is an effective process for degradation of the organic pollutants.

Enhanced Naproxen Elimination in Water by Catalytic Ozonation Based on NiO Films

This study evaluates naproxen (NP) degradation efficiency by ozonation using nickel oxide films (NiO(F)) as a catalyst. The NiO films were synthesized by chemical vapor deposition and characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. NP degradation was conducted for 5 min using 10 films of NiO(F) comparing against ozonation using 100 mg/L NiO powder in suspension (NiO(S)) and conventional ozonation (O3-conv). Total organic carbon analysis demonstrated a mineralization degree of 12% with O3-conv, 35% with NiO as powder and 22% with NiO(F) after 60 min of reaction. The films of NiO(F) were sequentially used 4 times in ozonation demonstrating the stability of the synthesized material, as well as its properties as a catalyst for ozonation. A proposed modeling strategy using robust parametric identification techniques allows the comparison of NP decomposition pseudo-monomolecular reaction rates.

Use of the ozonation method in treating dentin caries in children’s permanent teeth

Relevance. Permanent teeth carious involvement starts from their eruption in children aged 5-6 years. Hard tissues mineralization in permanent teeth lasts long. Nowadays, efficacy of combined applying calcium containing drugs and the ozonation method while treating permanent teeth caries in children with incompleted processes of dental hard tissues mineralization has not been revealed.Purpose. Increasing effectiveness of dentin caries treatment of children's permanent teeth with incompleted mineralization processes in dental hard tissues. Materials and methods. There were carried out clinical and laboratory examinations and treatment of 41 children (aged 6-14). They had dentin caries in permanent teeth with incompleted mineralization processes in hard tissues .In 2 groups studied carious cavities were treated mechanically and medically and afterwards the dentin density measurement was made by the method of fluorecent analysis using DIAGNOdent apparatus. The mineralization degree of clinically intact dentin having been determined, in Group 1 Dycal paste and a hermetic temporary filling of glass ionomer cement were placed onto the floor of carious cavities. In Group 2 carious cavities were treated mechanically and medically and then ozonized during 30 seconds with Kavo - HealOzone apparatus followed by application of Dycal paste onto the floor of carious cavities and temporary filling with glass ionomer cement. Three months later, the temporary filling material and Dycal paste were removed out of the children's teeth in both groups and measuring mineralization degree of the clinically intact dentin was made again. Results. Dentin mineralization increase in Group 1 showed 33,9% following delayed filling technique. In Group 2 the ozonation method promoted the increase by 54,9%.Conclusions. Carious cavitiies ozonation before applying calcium containing material favours higher mineralization degree (by 21%).

Role of surface water in the formation of underground water in Aghstafachai-Ganjachai interfluve and its usage prospects

With the purpose of water resources estimation of Aghstafachai-Ganjachai interfluve, geophysical surveys have been carried out. As a result, based on the well data, the maps were developed and interface conditions of the territory specified. The tectonic structure of Aghstafachai-Ganjachai interfluve lowland is associated with the formation of a sole artesian basin on its territory. Aghstafachai, Hasansu, Tovuzchai, Zeyemchai, Shamkirchai, Goshgarchai, Ganjachai and Kurekchai, being the main source of groundwater recharge, created a combined alluvial cone on the territory. The underground water of these rivers were studied in the sloping plain and the estimation of its volume carried out as well. It was revealed that the underground water on a large part of studied territory is fresh and less mineralized. From the bacteriological point of view, it is clean water. The content of microelements and harmful chemical substances in the water does not exceed the standards set for the drinkable water. Despite the long-term usage, the quality of the underground water, the mineralization degree and chemical composition remain unchanged. The regime of underground water is characterized with the irrigated climate type. Hydrogeological indexes and the parameters of ground water horizon in the studied area justify the possibility of their research for water supply.