Search Results (70)

Traditional soil management in vineyards and olive groves of semi-arid regions relies on repeated tillage, which accelerates soil organic matter (SOM) oxidation and limits long-term carbon storage. In the context of carbon-neutral agricultural strategies, understanding how alternative practices influence SOM stocks, redistribution, and stabilization is essential. We sampled six paired sites in central Spain (three vineyards and three olive groves), each comprising adjacent plots under conventional tillage or continuous cover cropping, at 0–10 and 10–30 cm depths. We analyzed water-extractable organic carbon (WEOC), optical properties of water-extractable organic matter (WEOM; specific UV absorbance at 254 nm (SUVA₂₅₄) and the absorbance ratio E4/E6), β-glucosidase activity, and the SOC/clay ratio as a proxy for mineral-associated SOC stabilization. Depth was the main factor structuring SOC and biological activity, with higher values in the topsoil. Management effects on bulk SOC were limited although cover cropping increased aboveground biomass and influenced WEOC dynamics. Vertical contrasts (30–10 cm) showed a positive association between WEOC and SOC/clay, suggesting that increased WEOC at depth co-varies with stabilization potential. Partial least squares analysis for 10–30 cm showed that SOC/clay was associated with WEOC, E4/E6, and β-glucosidase activity. These results suggest that subsoil carbon stabilization in semi-arid conditions may be linked to DOC availability and microbial processing rather than directly to surface biomass inputs. Full article

Drinking-water treatment systems must effectively control natural organic matter (NOM), a major precursor of regulated disinfection by-products (DBPs). Specific ultraviolet absorbance (SUVA) is widely used as an operational surrogate for NOM aromaticity and hydrophobicity; however, ozonation and subsequent filtration can disrupt the linear relationship between SUVA and trihalomethane formation potential (THMFP). This study evaluates whether SUVA can reliably predict THMFP under two ozonation configurations frequently applied in drinking-water treatment: pre-ozonation prior to coagulation–filtration and final ozonation following filtration. Experimental data were analyzed using conventional linear regression and artificial neural network (ANN) models, with SUVA employed as the sole predictor variable. Across all treatment configurations, reductions in SUVA were consistently more pronounced than corresponding decreases in THMFP, indicating a decoupling between chromophoric loss and chlorine-reactive precursor dynamics under ozonation-dominated conditions. Linear regression models exhibited only moderate predictive performance (R² = 0.63–0.76), reflecting the limitations of proportional surrogate-based approaches when NOM undergoes oxidative and adsorptive transformation. In contrast, single-parameter ANN models captured the nonlinear SUVA–THMFP relationship with substantially higher accuracy across both pre- and final-ozonation regimes (R² = 0.88–0.99), successfully resolving process-dependent patterns embedded within optically compressed SUVA signals. These findings demonstrate that, although SUVA alone cannot linearly represent the multistep transformation of NOM during ozonation and adsorption, it retains process-relevant structure information on DBP precursor reactivity that can be effectively extracted using nonlinear modelling. The results highlight the potential of integrating ANN-driven tools into advanced monitoring and DBP-control strategies in modern drinking-water treatment systems. Full article

Understanding the long-term evolution of soil carbon pools and dissolved organic matter (DOM) is crucial for evaluating carbon cycling and soil fertility in paddy ecosystems. This study investigated the changes in soil organic carbon (SOC), dissolved organic carbon (DOC), and DOM optical characteristics across an 8–63-year rice cultivation chronosequence in the western Jilin irrigation district of northeastern China. Soil samples were collected from five depth intervals (0–10, 10–20, 20–30, 30–40, and 40–50 cm) to assess physicochemical properties, ultraviolet–visible (UV-Vis) absorption, and three-dimensional excitation–emission matrix (EEM) fluorescence features. The results showed that long-term rice cultivation reduced soil salinity and alkalinity while significantly increasing SOC and DOC contents. The UV–Vis indices (SUVA₂₅₄, SUVA₂₆₀, SUVA₃₀₀) increased with cultivation duration, whereas E2/E3, E4/E6, and SR decreased, indicating enhanced aromaticity, humification, and molecular weight of DOM. Fluorescence analysis revealed a gradual transformation from protein-like to humic-like components, supported by PARAFAC modeling that identified four dominant components (two humic-like and two protein-like). Correlation and PLS-SEM analyses demonstrated that cultivation duration positively influenced soil carbon accumulation and DOM humification, while soil depth exerted a negative effect. Soil carbon acted as the core mediator linking UV–Vis and EEM indices, explaining more than half of the observed variance. Overall, long-term rice cultivation promoted carbon stabilization and humic substance formation, improving soil quality and carbon sequestration potential in saline–alkaline paddy soils. These findings provide valuable insights into the spectroscopic mechanisms of DOM transformation and the sustainable management of carbon processes in temperate agroecosystems. Full article

The present research moves the focus from merely describing epikarst flow to quantifying its natural filtration performance and contaminant retention mechanisms through integrating in situ tracer experiments with controlled laboratory modelling—an approach seldom applied in previous studies. Two field experiments at Peč Cave demonstrated that the epikarst exhibits rapid hydraulic connectivity—evidenced by fast tracer breakthrough with virtual flow speeds between 0.0041 and 0.006 m/s—yet simultaneously provides strong attenuation, as shown by the low tracer recovery and near-complete removal of microbial contaminants as well as nitrogen compounds through retention, degradation, and dilution under natural infiltration conditions, including rainfall and snowmelt. Complementary laboratory simulations further confirmed this duality, with nitrate concentrations reduced by 30–50%. Field data and lab results consistently indicated that the epikarst does not merely transmit water but actively adsorbs and transforms pollutants. Overall, the epikarst on Suva Planina functions as an effective natural filtration layer that substantially improves groundwater quality before it reaches major karst springs, acting as a protective yet vulnerable “skin” of the aquifer. These findings highlight the epikarst’s critical role in Suva planina Mt. karst aquifer protection and results support consideration of epikarst in groundwater management strategies, particularly in regions where springs are used for public water supply. Full article

Bupleurum falcatum (Apiaceae) sensu lato includes multiple infraspecific taxa with longstanding taxonomic ambiguities, often resulting from incomplete morphological and chemical characterizations. Herein, diethyl ether extracts were analyzed from four Balkan populations that were tentatively identified as B. falcatum subsp. falcatum (syn. B. falcatum) and B. falcatum subsp. cernuum (syn. B. sibthorpianum). Comprehensive chromatography and spectroscopic techniques (GC-MS and 1D/2D NMR) enabled the isolation of several newly identified aliphatic polyunsaturated esters, including compounds bearing uncommon conjugated tetraene and triyne backbones. These novel structures differ from canonical falcarinol derivatives by lacking the usual 3-hydroxylation, suggesting a divergent branch in the crepenynate pathway. The chemical profiles of each sample correlated closely with leaf morphology and infraspecific designations: for example, the Galičica Mt. population of B. falcatum featured a unique newly detected heptadecadientriyne, while the populations from Šar Planina and Suva Planina displayed distinct polyunsaturated repertoires. Extracts from B. sibthorpianum likewise contained stereoisomeric compounds that highlight metabolic divergence. Collectively, these findings demonstrate significant chemotypic variation within the Bupleurum falcatum complex and provide the first account of less-polar secondary metabolites, including newly discovered polyunsaturated metabolites. Future research integrating molecular markers and bioactivity assays may elucidate how these specialized metabolites contribute to both the taxonomy and pharmacological potential of these understudied taxa. Full article

To investigate the changes in the composition and structure of the dissolved organic matter (DOM) of the lysate solutions of different types of soil after green manure tilling treatment, we set up two types of soil materials (fluvo-aquic soil; coastal saline soil) and three green manure tilling treatments (T1: CK—without green manure, T2: tilling Dongmu70 rye, and T3: tilling rapeseed green manure); then, the soil leachate was obtained with a soil column simulation test and its DOM spectral properties were determined. The rapeseed green manure leachate demonstrated a significantly higher humic macromolecule content and aromaticity compared to Dongmu70 rye leachate. Fluorescence Index (FI) values (1.5–2.2) suggest a mixed origin of dissolved organic matter (DOM) from both terrestrial and microbial-derived sources. All Humification Index (HIX) values remained below 1, indicating low humification levels and limited stabilization of DOM within the leachate system, and Biological Index (BIX) values exceeding 1 across all soil layers highlight the predominance of a recent biological metabolism in shaping DOM autochthonous origins. The SUVA₂₆₀ values in Dongmu70 rye–moist soils and rapeseed green manure–coastal saline soil exhibited reductions of 0.020–2.573 L·(mg·m)⁻¹ relative to pre-drenching levels. After tilling rapeseed green manure, the SUVA₂₅₄ value of coastal saline soil at the 60–90 cm layer decreased by 1.941 L·(mg·m)⁻¹. This study shows that differences in green manure and soil type affect DOM sources and composition, reducing DOM leaching, with coastal saline soil + rapeseed green manure and fluvo-aquic soil + Dongmu70 rye being the advantageous combinations. The study results provide theoretical guidance for applying green manure coupled with freshwater leaching technology in the context of saline and alkaline land with multiple soil types. Full article

Dissolved organic carbon (DOC) is a critical parameter in water quality management due to its interaction with disinfectants, leading to the formation of disinfection byproducts (DBPs) during water treatment. Forest ecosystems are key contributors of DOC to surface waters, stemming from soil leachate. This study is the first to use DOC solutions directly extracted from soil to examine the formation of trihalomethanes (THMs) during chlorination and chloramination under varying environmental conditions. For this purpose, soil samples from a densely forested upland Cedar Lake watershed in Illinois were processed to extract DOC, which was then subjected to controlled disinfection experiments under varying pH, temperature, disinfectant dose, and reaction time. The results demonstrate that chlorination produces significantly higher levels of THMs compared to chloramination, with THM concentrations ranging from 31.996 μg/L to 62.563 μg/L for chlorination and 0.508 μg/L to 0.865 μg/L for chloramination. The yields of DBPs determined by chloramination increased approximately 4, 5, and 10 times with a higher DOC concentration, disinfectant concentration, and reaction time, respectively. For chlorination, these increases were approximately 5, 8, and 3 times, respectively. The presence of bromide in the DOC solutions influenced the concentration of brominated THMs (Br-THMs). The results indicate that a high formation of THMs, during both disinfection processes, occurred in the pH range of 7–8 and temperature range of 20–25 degrees Celsius. Furthermore, all tested water quality indicators (DOC, total dissolved solids, turbidity, and UV254), except for pH and Specific Ultraviolet Absorbance (SUVA), exhibited a strong positive correlation with THM levels during chlorination. In contrast, these parameters displayed a moderate to weak correlation with THM levels in the chloramination process. These findings highlight the critical role of DOC characteristics and disinfection conditions in controlling THM formation, providing valuable insights for optimizing water treatment processes. Full article

Background: Antimicrobial resistance is a global health threat and Fiji is not exempt. The appropriate prescribing and timely de-escalation of antibiotics as an integral component of antimicrobial stewardship has been recently introduced in Fiji to help curb antimicrobial resistance through de-escalation, leading to a reduced opportunity for the induction of resistance. Objectives: To assess whether empirical antibiotics are being adjusted in a timely fashion in patients admitted with a diagnosis of suspected infection in the Colonial War Memorial Hospital( CMWH) over three months. Method: The study was undertaken on patients admitted to the acute medical ward and intensive care unit of the CWMH in Suva (Fiji’s largest hospital). A total of 474 patients were prospectively enrolled at admission when prescribed empiric antibiotic therapy for suspected infections between February and April 2019. Results: A total of 356 patients admitted to the Acute Medical Ward and 118 admitted to the Intensive Care Unit were prescribed empiricalantibiotics. These 474 patients were prospectively observed to determine the factors influencing the extent and the timing of antibiotic de-escalation. Only 137 (29%) patients had their antibiotic regimen de-escalated in the first 72 h post-admission based on their microbiological results, whereas, 207 (42%) were de-escalated more than 72 h after admission (OR = 0.5, 95% CI 0.3–0.89; p < 0.016). Conclusions: At CWMH, antibiotic de-escalation is slow and may be improved by quicker laboratory reporting, greater access to laboratory results for prescribers, and the availability of a wider range of narrow-spectrum antibiotics to assist de-escalation. Full article

Eutrophication is a major environmental issue affecting freshwater ecosystems worldwide. While its impact on the composition of dissolved organic matter (DOM) is well recognized, the relationships between DOM’s optical and molecular properties across eutrophication gradients remain underexplored. This review synthesizes recent research on DOM’s optical properties (derived from UV-Vis absorption and fluorescence spectroscopy) and molecular characteristics (analyzed using Fourier-transform ion cyclotron resonance mass spectrometry, FT-ICR MS) in freshwater systems of varying trophic states. Generalized additive model (GAM) analysis was used to assess correlations between DOM’s properties and the trophic state index (TSI). The dissolved organic carbon (DOC), a₂₅₄, SUVA₂₅₄, S_R, HIX, BIX, and FI averaged 11.44 ± 11.97 mg/L, 23.23 ± 16.95 m⁻¹. 2.98 ± 0.99 L·mg⁻¹·m⁻¹, 1.42 ± 0.38, 2.38 ± 1.31, 1.08 ± 0.16, and 2.11 ± 0.44, respectively, from mesotrophic to middle-eutrophic sites. The GAM results revealed a significant linear correlation between DOC and DOM’s optical properties, including a₂₅₄, SUVA₂₅₄, and FI, with the TSI, suggesting that DOM accumulation intensifies with eutrophication. DOM’s molecular properties, such as O/C and H/C ratios, double bond equivalents (DBEs), and CHOS% content, exhibited nonlinear correlations with the TSI. These trends imply a shift in DOM sources from terrestrial and macrophyte-derived inputs to those dominated by algal- and sediment-derived sources as eutrophication progresses. We concluded that DOM’s molecular indices alone may not serve as a reliable indicator of freshwater trophic states; future studies should focus on integrating both optical and molecular indices to offer a more comprehensive assessment of freshwater trophic states. Given the limited number of molecular variables examined in this study, this work only offers a preliminary investigation into the relationship between DOM molecular changes and freshwater eutrophication. More systematic studies focusing on the molecular-level analyses of DOM across varying trophic states on a broader geographic scale are needed. Full article

This study focuses on optimizing the ozonation process in drinking water production from Lake Butoniga to ensure safe water quality while minimizing disinfection by-products (DBPs). Laboratory simulations were conducted using the Box–Behnken design to model the effects of ozone dose and treatment duration on bromate formation, trihalomethanes (THMs), haloacetic acids (HAAs) and specific UV absorption (SUVA). Two ozonation strategies were tested: Strategy 1 aimed to minimize all DBPs, while Strategy 2 focused on controlling bromate levels while keeping THMs, HAAs and SUVA below 80% of maximum contaminant levels. Results showed that Strategy 2 reduced ozone consumption while maintaining water quality within regulatory standards, providing a cost-effective and environmentally sustainable treatment approach. Seasonal and depth-dependent variations in water quality had a significant impact on treatment efficiency and required adjustments to operational settings. The study also addressed discrepancies between laboratory and real plant results and suggested recalibration methods that improved the accuracy of model predictions. These results highlight the potential for integrating predictive modelling and dynamic treatment strategies into large-scale water treatment processes. Full article

Storm events have a notable impact on natural organic matter (NOM) and trihalomethanes (THMs). Water samples were collected and analyzed from Ulutan Dam (UD), in the Zonguldak region, Turkey. During four storm events, the data indicated the presence of hysteresis patterns in three of the four storms, with elevated concentrations of organic constituents observed during the falling limb of the hydrographs. It was observed that a higher specific THM (sp.THM) concentration (201.83 µg/L) was reached with an average specific UV absorbance (SUVA) value of 6.66 L/mg·m in the fourth storm. This means that the primary sources of THM precursors are the aromatic compounds present in NOM. A significant correlation between UV absorbance (UV₂₅₄) and dissolved organic carbon (DOC) (R = 0.99–0.92) for all storms was observed. Chlorine demand also yielded a strong correlation (R = 0.81–0.99) with UV₂₅₄ and DOC. Therefore, the present study indicates that UV₂₅₄ can be an effective parameter for monitoring applicable chlorine dosage in drinking water treatment management as faced with storm events. On the other hand, the results of the study also provide valuable insight into the direct and indirect link between short-term precipitation events and their impact on the structural and THM precursors in surface water sources. Full article

Landfill leachate contains a range of organic and inorganic pollutants, including per-/polyfluoroalkyl substances (PFASs), which can infiltrate into surrounding soil and groundwater through leaching processes, and can pose a threat to human health via food chains and drinking water processes. Thus, the transport of PFASs in landfill leachate is a research hotspot in environmental science. This study investigates the complexation and adsorption mechanisms between humic substances and PFASs in landfill leachate at the molecular level. Experimental results demonstrate that the binding constant logK_sv of humic substances with PFASs correlates positively with specific ultraviolet absorbance (SUVA₂₅₄), absorbance ratio (A₂₅₀/A₃₆₅), humification index (HIX), and fluorescence index (FI), while it exhibits a negative correlation with the biological index (BIX). These findings indicate that high aromaticity is a prerequisite for molecular interactions between humic substances and PFASs, with polar functional groups further facilitating the interaction. Molecular-level analysis revealed that humic substances undergo complexation and adsorption with PFASs through hydrophobic interactions, van der Waals forces, hydrogen bonding, ionic bonding, and covalent bonding, by functional groups such as hydroxyl, aliphatic C-H bonds, aromatic C=C double bonds, amides, quinones, and ketones. Future efforts should focus on enhanced co-regulation and mitigation strategies addressing the combined pollution of PFASs and humic substances in landfill leachate. Full article

In this study, the effectiveness of the Fenton process in removing natural organic matter (NOM) from groundwater was investigated. The subject of this study is groundwater characterised by increased content of NOM and iron (II) compounds. In laboratory-scale studies, the influence of the ratio of concentrations of Fe(II) ions, which are naturally occurring in groundwater, to hydrogen peroxide (H₂O₂) as well as oxidation time and pH on the removal efficiency of organic matter was determined. Indicators such as total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV₂₅₄), UV absorbance at 272 nm (UV₂₇₂), and specific UV absorbance (SUVA₂₅₄) were used to quantitatively and qualitatively assess the organic substances present in the raw water and after oxidation with Fenton’s reagent. Analysis of the results obtained showed that the highest removal efficiency of organic substances in the deep oxidation process using the Fenton reaction was obtained for a concentration ratio of Fe(II) to H₂O₂ = 1:5. Acidification of the water samples to a pH of about 4 and extending the oxidation time to 30 min significantly increased the removal efficiency of organic substances including mainly dissolved organic substances containing aromatic rings. The organic substances containing aromatic rings, determined at a wavelength of 254 nm, were degraded to other organic intermediates. Full article

The spotted eagle ray Aetobatus ocellatus (Kuhl, 1923) has a widespread Indo-West Pacific distribution and displays substantial population genetic structuring. Genetic data are crucial for understanding the species’ diversity, connectivity, and adaptation. However, molecular genetic information on A. ocellatus from Melanesia is lacking, which impedes our understanding of gene flow among geographic regions. In this study, we sampled 45 A. ocellatus, primarily from Fiji’s largest fish market in the capital, Suva. Mitochondrial DNA Cytochrome C Oxidase subunit I (COI) barcoding was used for species identification, and DArT-seqTM technology was applied to assess the nuclear genetic diversity. Barcoding of the COI gene showed a 98.6% to 99.8% similarity to A. ocellatus reference sequences in the Barcode of Life Data System, and the 45 individuals were represented by three major evolutionary haplotype clusters. Genotyping resulted in 24,313 Single-Nucleotide Polymorphisms (SNPs) which were quality-filtered to 7094 SNPs per individual. The observed heterozygosity level was 0.310. The inbreeding coefficient was positive, and genotyping identified one full-sibling pair and one half-sibling pair from the 45 individuals. Additionally, eagle rays exhibit polychromatic patterns, and at least three ventral pattern variations were recorded in specimens from the market. Collectively, our main findings characterize the genetic profile of A. ocellatus in Fiji and can help to understand the diversification of this species within the region. Full article

With the explosion of crab farming in China, the urgent need to treat crab wastewater can never be overemphasized. Hence, in this study, excitation–emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC), moving window two-dimensional correlation spectroscopy (MW-2DCOS) and structural equation modeling (SEM) were employed to identify changes in the dissolved organic matter (DOM) fractions in a crab farming park and reveal latent factors associated with removal processes. Seven components (C1–C7) were extracted from DOMs by EEM-PARAFAC as follows: C1: microbial byproduct-like substances, C2: visible-tryptophan-like substances, C3: fulvic-like substances, C4: phenolic-like substances, C5: ultraviolet tyrosine-like substances, C6: D-tryptophan-like substances and C7: L-tryptophan-like substances. Interestingly, C7 (39.20%), a representative component of DOM in the crab farming pond, was deeply degraded in the aeration pond by aerobic microbes, whereas C6 was absent in the crab pond. According to 2DCOS, the changing order of the components was C7 → C4 → C6 → C5 → C2 → C1 → C3, and the changing order of the functional groups was carboxylic → phenolic → aromatic. As assessed by MW-2DCOS, the Fmax of the components, especially components C2, C5 and C6 (and with the exception of C4 and C7) exponentially increased in the aeration pond, where an accumulative effect occurred. C2, C5 and C7 were removed by 24.26%, 39.42% and 98.25% in the crab farming system, and were deeply degraded in the paddy-field, purification pond and aeration pond, respectively. As assessed by SEM, the latent factors of organic matter removal were C1, C2, C4, C5, SUVA254, COD_Mn and DO. This study could be conducive to comprehensively characterizing the removal of components and functional groups of DOMs in crab farming parks. Full article