Search Results (217)

Over the last decade, bark beetle outbreaks have significantly impacted forests in Central Europe, causing extensive loss of forest cover. We evaluated the impact of partial deforestation in three mountain forest catchments in the Jeseníky Mountains, comparing them with the unaffected Červík catchment (Beskydy Mountains) and the severely affected Pekelský stream catchment (Czech-Moravian Highlands). Atmospheric deposition in the catchments was similar, with total element input driven primarily by precipitation volumes rather than ion concentrations. We did not observe the hypothesized increase in DOC and nitrogen export, although nitrate outflow was slightly higher than atmospheric input in two cases. Significant export of calcium, magnesium, and bicarbonates was driven mainly by the geology of the individual catchments. The limited impact of bark beetle outbreaks on DOC dynamics can be attributed to the relatively low proportion of clear-cut areas and the rapid development of ground vegetation on impacted sites. Full article

The photo-Fenton process has been widely studied for the treatment of organic pollutants and disinfection in a wide range of scenarios. Nevertheless, its efficiency decreased when applied to complex matrices, as in the case of most advanced oxidation processes. Despite the interferences caused by different anions, the photo-Fenton is able to obtain good degradation values for pollutants and microorganisms, especially in combination with other methods; however, it depends on the matrix to be treated. Due to the lack of studies and reviews in this field, this paper reviewed the outcome of the inorganic ions present on highly saline water matrices (more than 1 g L⁻¹ of chlorides, fluorides, bromides, sulphates, carbonates or bicarbonates, borates, phosphates and nitrates/nitrites) on the Fenton-based processes, focusing on their outcome on iron speciation and their scavenger effect. Also, the most relevant works so far for the abatement of microcontaminants and disinfection by this process on highly saline matrices have been revised. Special emphasis is on the efficiency of the process, considering the relevant industries referred to. Full article

The observed shortage of water resources in the western and southern regions of the Russian Federation may soon affect the territory of the Republic of Bashkortostan. An increase in the share of groundwaters can help to solve this problem. To provide the population of the republic with water resources, the groundwater of magnesium–bicarbonate-type from the Kraka ophiolite massifs can be used. The massifs occur on the western slope of the Southers Urals. In this work we studied ultramafic rocks and their influence on the formation of the chemical composition of water. The research area is located in the northern part of the Zilair synclinorium, which occurs within the Central Ural megazone. In terms of hydrogeology, of particular importance to the territory of the synclinorium is the Zilair basin of fracture waters of the second order, which is part of the Uralian hydrogeologic folded zone. The ultramafic rocks from the studied area have consistently high CaO/Al₂O₃ ratios (0.4–1.6), which indicates the widespread development of parageneses with participation of clinopyroxene and a low degree of depletion of the primitive mantle source. Because of the complex geological structure of the area, water samples collected from both water points in the Kraka massifs, and the surrounding Early–Middle Paleozoic rocks were analyzed for major ions using a laboratory method to identify possible hydro-geochemical zoning. A statistical analysis was then conducted based on the obtained anion–cation composition data. From the viewpoint of the hydrolytic concept, the formation of the chemical composition of groundwater takes place due to the removal of Mg²⁺ from the rock-forming minerals of ultramafic rocks (olivine and pyroxene) and the supply of Na⁺, K⁺, Ca²⁺, and SO₄²⁻ Cl⁻ from atmospheric precipitations. The bicarbonate anion has a complex nature, where both biochemical processes in the soil and atmospheric precipitation play a significant role. Magnesium–bicarbonate-type of waters, due to low mineralization (to 1 g/L) and the majority of other geochemical parameters (pH of the medium, and content of Na, K, Ca, SO₄, and Cl), whose values that are within the limits set by the World Health Organization (WHO), can be used as drinking water. The increased values of total hardness (0.20–3.39 mmol/L) in accordance with the regulatory document SanPiN 1.2.3685–21, adopted by the Russian Federation, do not exceed the maximum permissible concentrations (up to 7.00 (10.00) mEq/L or 3.50 (5.00) mmol/L). The high magnesium content, in accordance with GOST (state standard) R 54316–2020, allows the magnesium–bicarbonate waters of the Kraka massifs to be classified as table mineral waters for the treatment of various diseases (including hypomagnesemia). Full article

Sulfamethazine (SMT) contamination in aquatic environments and its propensity to induce antibiotic resistance pose critical risks to ecosystems and public health, necessitating effective remediation strategies. Here, we develop a MOF-derived copper core–shell activator, Cu-MOFs400@PSN, by coating a calcined Cu-MOF derivative (Cu-MOFs400) with a nitrogen/phosphorus/sulfur-doped shell and systematically evaluate its peroxymonosulfate (PMS) activation performance toward SMT degradation. Comprehensive characterization confirms successful N/P/S incorporation and the formation of a smooth spherical core–shell architecture that enhances chemical stability; the Cu-MOFs400@PSN/PMS system achieves complete SMT removal within 120 min and maintains 99.33% efficiency after five reuse cycles. Bicarbonate markedly promotes degradation, whereas chloride, nitrate, and phosphate exert negligible interference, indicating strong tolerance to common background ions. Radical-quenching tests identify singlet oxygen (¹O₂) and superoxide (•O₂⁻) as the dominant reactive species, with minor contributions from sulfate and hydroxyl radicals; the system facilitates complete SMT mineralization and reduces resistance-inducing intermediates. These results highlight Cu-MOFs400@PSN as a robust and reusable PMS activator for practical remediation of SMT-contaminated waters and mitigation of antibiotic-resistance risks. Full article

This study discusses the unique features of the rural park Parque Rural del Nublo (Gran Canaria) that resulted in the designation of this site as UNESCO’s Biosphere Reserve. Due to its indigenous flora and fauna, its mild climate and its farming lands, this park is considered as an outdoor “sustainable research laboratory”. This paper describes the main features (source, denomination, classification, municipality, year of declaration and hydro-chemical facies) of some of the many groundwater springs found in the park. The quality of the drinking water obtained from the spring “El Molinillo”, located in the basin of the municipality of Tejeda, is analysed by assessing its organoleptic, physico-chemical, chemical and bacteriological properties. Considering that it is described as “natural mineral water”, based on the taxonomy for mineral–medicinal waters, the water from “El Molinillo” is classified as hypothermal, alkaline and very soft water, with a low conductivity, a very weak mineralisation and a significant silica content. The water especially contains the following ions: bicarbonate, chloride, magnesium and calcium. The paper describes several pharmacological effects and therapeutic indications attributed to this water, analysing the impact of its silica content on human and plant health. The paper concludes that the park should be permanently protected as a World Heritage Site, and the water obtained from “El Molinillo” is classified as “drinking water”, “natural mineral water” and “mineral–medicinal water”. Full article

Dental enamel, the final product of amelogenesis, is a highly mineralized bioceramic that becomes acellular and non-regenerating after tooth eruption. This paper reviews literature that explores inorganic phosphate (Pi) transport during the process of enamel formation or amelogenesis. Evidence from transcriptomics, immunolocalization, and physiology implicates ameloblast-specific sodium-dependent Pi uptake by type III sodium–phosphate cotransporters SLC20A1 (PiT1) and SLC20A2 (PiT2), and by type IIb sodium–phosphate cotransporter SLC34A2 (NaPi-IIb) with stage-specific basal (proximal) or apical (distal) enrichment, and pH-dependent expression. Controlled Pi efflux to the enamel space has been partly attributed to xenotropic and polytropic retrovirus receptor (XPR1) mediated Pi export during maturation-stage amelogenesis. These amelogenesis-specific Pi fluxes operate within a polarized cellular framework in which Ca²⁺ delivery and extrusion, together with bicarbonate-based buffering regulated by cystic fibrosis transmembrane conductance regulator (CFTR), Solute carrier family 26 (SLC26) exchangers, anion exchanger 2 (AE2), and electrogenic sodium bicarbonate cotransporter 1 (NBCe1), at-least partially contribute to cellular Pi activity, and neutralize protons generated as the extracellular hydroxyapatite-based enamel matures. Disruption of phosphate handling reduces crystal growth and final mineral content of enamel, and produces hypomineralized or hypomature enamel with opacities, post-eruptive breakdown, and greater caries susceptibility. This review integrates multi-modal findings to appraise established features of ameloblast Pi handling, define constraints imposed by pH control and Ca²⁺ transport, and identify gaps in ion transporter topology and trafficking dynamics. Full article

Background: The relative merits of the Henderson–Hasselbalch (HH) versus Stewart frameworks for interpreting dialysis-associated acid–base shifts remain debated. Dialysis alters systemic pH through exogenous bicarbonate delivery, chloride displacement, and removal of organic anions. We compared these approaches across hemodialysis (HD) and peritoneal dialysis (PD). Methods: We studied 53 HD patients with paired pre/post-HD blood gas and chemistry (106 observations) and 41 PD patients cross-sectionally, totaling 147 datasets. Derived variables followed the Figge/Stewart implementation [apparent SID (SIDa), effective SID (SIDe), strong ion gap (SIG), albumin-corrected anion gap (AGc)]. For HD, changes in pH (ΔpH) were modeled using HH predictors (ΔHCO₃⁻, ΔPCO₂) and Stewart predictors (ΔSIDa, ΔATOT, ΔPCO₂). For cross-sectional data (pre-HD, post-HD, and PD), HH- and Stewart-based level models were fitted. Stewart-predicted pH was also computed using the Figge and the simplified Constable electroneutrality equation. Results: HD increased pH by 0.11, driven by ΔHCO₃⁻ = +5.7 mΕq/L, ΔCl⁻ = −2.3 mEq/L, and declines in unmeasured anions (ΔSIG = −3.9; ΔAGc = −3.3). SIDa increased only marginally (+1.3 mEq/L), whereas SIDe rose by +5.3 mEq/L and fully tracked the alkalinization. In Δ-models, HH explained 90% of variance in ΔpH (R² = 0.903) compared with 51% for Stewart (R² = 0.514). In level models, HH explained 96% of pH variance versus 36% for Stewart. Bland–Altman analysis showed systematic overestimation of pH by the Figge and Constable approach (bias + 0.111), most pronounced pre-HD. PD patients had consistently higher AGc and SIG values than HD patients, indicating a greater burden of unmeasured anions. Conclusions: Alkalinization during HD is primarily attributable to bicarbonate gain, chloride displacement, and organic-anion clearance. The HH framework provides superior predictive performance for ΔpH, while closed-system Stewart formulations based on SIDa underestimate alkalinization. However, a broader physicochemical interpretation using SIDe and SIG, which incorporate bicarbonate and unmeasured anions, coherently describes the observed physiology. Future applications of the Stewart approach in dialysis should emphasize SIDe and SIG to better reflect the open-system physiology of both HD and PD. Our findings suggest that the HH model remains more predictive of alkalinization, while SIDe and SIG refine the physicochemical understanding. Full article

Soil salinity and bicarbonate-induced alkalinity severely limit melon productivity by disrupting physiological and biochemical processes. This study evaluated the effectiveness of grafting an Iranian cantaloupe cultivar, ‘Til-e-Sabz’, onto Cucurbita maxima × C. moschata rootstock in mitigating salinity (10 mM NaCl; 2.7 dS m⁻¹) and alkalinity (10 mM NaHCO₃; 2.6 dS m⁻¹) stress in soilless culture. Compared to non-grafted plants, grafted plants exhibited 22–35% greater leaf area, 28–40% higher shoot and root fresh biomass, and 25–38% higher dry biomass under both stress conditions. Relative chlorophyll content (SPAD) and total chlorophyll were reduced by stress but remained 15–21% higher in grafted plants. Carotenoid content was also maintained at 10–14% higher levels in grafted plants compared to non-grafted controls. Proline and soluble protein accumulation increased significantly under stress, with grafted plants accumulating 18–25% more proline and 12–20% more protein, indicating enhanced osmotic adjustment. Sodium levels increased in the roots and shoots under stress. However, grafted plants maintained 30–45% lower Na accumulation relative to non-grafted plants. In contrast, grafted plants showed up to 27% higher phosphorus and 32% higher iron uptake, while maintaining greater potassium retention (18–24%) under both salinity and alkalinity. Overall, grafting significantly improved physiological resilience and ion homeostasis, leading to enhanced stress tolerance. These findings demonstrate that grafting is a promising agronomic strategy to sustain melon production in saline and alkaline environments associated with increasing soil and water degradation. Full article

Bletilla striata, a perennial orchid of both medicinal and ecological value, exhibits remarkable adaptability to bicarbonate-rich karst environments. To elucidate its physiological and electrophysiological responses to bicarbonate stress, seedlings were cultivated for 45 days under NaHCO₃ concentrations of 0, 5, 10, and 15 mM (n = 4), with the nutrient solution renewed daily. At 5 mM, biomass, chlorophyll content, electrophysiological traits, nutrient transport, metabolic indices, and conductance–resistance parameters did not differ significantly from controls, while intracellular water-use efficiency exhibited only a minor, non-significant increase—indicating stable physiological performance under low bicarbonate conditions. By contrast, higher concentrations (≥10 mM), particularly 15 mM, markedly reduced intracellular water-holding capacity (−35.90%), nutrient translocation capacity (−22.26%), and metabolic activity (−50.00%), alongside electrophysiological signatures of diminished capacitance (−48.69%) and elevated resistance (+147.61%), consistent with membrane injury and impaired ion transport. Although xylem pathways dominated HCO₃⁻ transport, the phloem—despite greater sensitivity—showed an increased relative contribution under stress, supporting partial compensatory allocation. Metabolically, severe stress induced a shift toward a “low-metabolism, high-efficiency” strategy, prioritizing water conservation over carbon assimilation. Collectively, Bletilla striata adopts a dual strategy: maintaining functional stability (and modest enhancement) under environmentally relevant bicarbonate concentrations, while shifting to conservative resource-use under excessive stress. These adaptive mechanisms highlight B. striata’s potential for ecological restoration and sustainable cultivation in bicarbonate-rich karst environments. Full article

Understanding groundwater quality and its controlling mechanisms is vital for the sustainable use of water resources in agriculturally intensive regions. This study evaluates the hydrochemical characteristics, controlling geochemical processes, and overall water quality of 226 groundwater samples collected from a typical agricultural reclamation area in the Sanjiang Plain, northeastern China. Major ion compositions indicate that groundwater is predominantly of the Ca–HCO₃ type, with bicarbonate, calcium, and magnesium as the dominant constituents. Spatial and statistical analyses reveal that rock weathering—particularly the dissolution of carbonates and silicates—is the primary natural process influencing groundwater chemistry, while cation exchange contributes moderately. Anthropogenic inputs, especially from fertilizers, livestock waste, and wastewater discharge, were found to elevate concentrations of NO₃⁻, Cl⁻, and SO₄²⁻ in localized zones. The entropy-weighted water quality index (EWQI) was applied to assess overall groundwater suitability. Results show that 89.8% of samples fall into “excellent” or “good” categories, though 6.6% of samples indicate poor to very poor water quality. This study identified the hydrochemical characteristics, sources of substances, and water quality of groundwater in the reclamation area, providing a basis for scientific prevention and control, rational utilization, and protection of groundwater resources. Full article

The non-oxidizing antimicrobial 2-Methyl-4-Isothiazolin-3-one (MIT) poses a significant environmental risk given its frequent detection in municipal wastewater. This study showed that the combination of Vacuum UV/UV (VUV/UV) and persulfate (PDS) efficiently achieved the rapid transformation and removal of 10 μM MIT within 90 s, which is much faster than UV, UV/PDS, and VUV/UV. Increasing the PDS dosage improved MIT degradation, whereas changes in pH between 4 and 10 had little effect. Radical quenching experiments showed that 93% of the MIT oxidation was attributable to the hydroxyl radical (•OH) and the sulfate radical (SO₄•⁻). SO₄•⁻ and •OH at concentrations of 8.6 × 10⁻¹² M and 1.5 × 10⁻¹² M accounted for 32% and 61% of the MIT degradation, respectively, and the greater contribution of •OH was attributed to its higher reaction rate constant with MIT compared to SO₄•⁻. Sulfate had a negligible impact on the radical concentrations. Chloride (1 mM) reduced the SO₄•⁻ and •OH concentrations by 61% and 27%, respectively. And the SO₄•⁻ contribution to MIT degradation fell to 19%. Nitrate (5 mM) readily quenched •OH but minimally affected SO₄•⁻. The •OH concentration decreased by 79%, reducing its contribution to 27%. Bicarbonate/carbonate (5 mM) simultaneously reduced the SO₄•⁻ and •OH by 26–30% and had little effect on their contributions. Because of the quenching effect of organic matter and inorganic anions on radicals, secondary effluent inhibited the degradation of MIT. After a 120 s treatment, the total organic carbon, UV₂₅₄, and fluorescence regional integration were reduced by 5%, 8%, and 17–24%, respectively. This study provides a quantitative analysis of how inorganic ions alter the concentrations and contributions of •OH and SO₄•⁻, elucidating the MIT removal mechanisms in VUV/UV/PDS for sustainable wastewater reclamation. Full article

This paper does not describe the results of a systematic search for the mechanism of action of cyclophosphamide and the consequences and possible indications arising from this mechanism. Rather, it describes a puzzle in which our own results, with some of them being very old, were re-evaluated with the latest biochemical knowledge and supplemented by results from the scientific literature. The mechanism of action of cyclophosphamide, which has been indispensable in clinical practice for 60 years, was unknown until recently simply because biochemical knowledge was lacking and because results from in vitro experiments were uncritically extrapolated to in vivo conditions. In vitro, the DNA alkylating metabolite phosphoramide mustard (PAM) is formed from the CP metabolite aldophosphamide (ALD) by phosphate and bicarbonate ion-catalyzed β-elimination of acrolein; in vivo, however, ALD is cleaved by phosphoesterases or DNA polymerase δ and ε, which are associated with 3′-5′ exonucleases, into the complementary metabolites PAM and 3-hydroxypropanal (HPA). The following describes the mechanism of action of CP, namely the complementary interaction of alkylating PAM and apoptosis-enhancing HPA, and it is shown that by optimizing the complementary effects of PAM and HPA, the antitumor efficacy in the P388 mouse tumor model can be increased by more than ten thousand-fold. Further experiments show that by optimizing the interaction of DNA alkylation and enhancing the resulting apoptosis by HPA, the formation of resistant metastases can be prevented and low-toxicity chemotherapy can be achieved. Full article

The concentrations of natural radioactive elements in the groundwater environment are regulated by several factors, including aquifer geology, groundwater hydrochemical properties, and changes in environmental conditions. Many studies have explored these factors, but few have systematically elucidated the mechanisms underlying the dissolution of radioactive elements from their host minerals into groundwater. This study investigated the petrological, mineralogical, and weathering properties of aquifer materials and their effects on the leaching of uranium (U) and thorium (Th) into groundwater. The time required for the U concentration to reach the drinking water standard (30 μg/L) was estimated through artificial weathering experiments performed under diverse environmental conditions. Rock core samples were obtained from three sites differing in their geology and groundwater U concentrations. Mineralogical analyses revealed that thorite, a representative radioactive mineral that contains large amounts of U and Th, was present in samples from all collection sites. Thorite minerals differed in terms of their sizes, shapes, cracks, and chemical compositions between samples from different sites, indicating that geological features, mineral alteration characteristics, and environmental conditions controlled the behavior of U and Th. These factors appear to play crucial roles in regulating the mobility and potential long-term leachability of U and Th. Artificial weathering experiments confirmed that a neutral pH with surplus bicarbonate ions favored U leaching. Under these environmental conditions, aquifer U concentrations were estimated to require 8.7–226 years to reach the drinking water standard, depending on the groundwater dissolved oxygen content. Our results provide scientific evidence that may be used for managing radioactive elements in the groundwater environment, and are likely to inform new environmental policies and regulatory standards. Full article

In recent decades, increasing anthropogenic pressure and climate change have made the protection and sustainable management of groundwater resources essential. In this context, the identification of aquifer recharge zones, especially those characterized by rapid groundwater flow and high vulnerability to surface pollution sources, becomes a priority for the protection of underground resources. In the Po Plain (northern Italy), based on the lithological, geometric, hydraulic, and hydrodynamic characteristics of the aquifers, the recharge areas are mainly located in the alluvial fans of the Alpine and Apennine foothills. Due to the high hydraulic conductivity of the aquifer, the shallow depth of the water table and the agricultural activities, groundwater resources are vulnerable to nitrate (NO₃⁻) contamination. Given this background, the present study introduces a novel methodological approach based on the geochemical signature of groundwater, indicated by the presence of bicarbonate (HCO₃⁻) and NO₃⁻ ions, aimed at identifying aquifer recharge areas. Specifically, by analyzing time series of NO₃⁻ and HCO₃⁻ concentrations for the period 2012–2023, and applying criteria of an HCO₃⁻/NO₃⁻ ratio < 10 and NO₃⁻ > 30 mg/L, it was possible to identify areas where aquifer recharge processes are clearly evident. These recharge processes are rapid, as confirmed by the hydraulic gradient, the high hydraulic conductivity of the aquifers, and further supported by the isotopic composition of groundwater, especially tritium concentrations. Furthermore, due to the hydrogeological characteristics of the surveyed region, which resemble those of alluvial basins in close proximity to mountain ranges, the methodology and findings of this study can be used as an unconventional and expedited method for similar research conducted globally, offering hope for the future of groundwater research. Full article

This study evaluated the ability of microalgae to produce carbonate minerals through CO₂ uptake, in comparison with abiotic, direct chemical synthesis through CO₂ absorption. A freshwater microalga (Synechococcus elongatus) isolated from garden soil in East Anglia, UK, was cultivated under laboratory conditions with CO₂ injection to generate a bicarbonate-rich aqueous solution, in which Fe²⁺, Mg²⁺, and Ca²⁺ ions were added to facilitate carbonate formation. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analyses revealed distinct morphologies and mineral types. The algae-based process precipitated calcite, siderite, magnesite, and dolomite, whereas the abiotic process yielded, respectively, calcite, siderite, high-Mg calcite and nesquehonite. Biogenic minerals were finer and more morphologically diverse than their abiotically formed counterparts. The results indicated that microalgae produced 0.21 mol/L of calcium carbonate, compared to 0.51 mol/L obtained through abiotic CO₂ sequestration, and a comparable yield of about 0.25 mol/L reported for Sporosarcina pasteurii-induced precipitation. Acid resistance tests showed that algae-induced minerals had similar or improved resistance to acidic conditions compared to minerals formed through abiotic CO₂ consumption. Overall, despite slower kinetics, algae-induced carbonate precipitation offers advantages for soil stabilization by biocementation in the context of environmental sustainability, climate change mitigation and circular economy. Full article