The balance of production and respiration processes in water of Crnojevica river (Montenegro, Yugoslavia) has been estimate, over the estimate correlation between significant parameters of water quality (BOD, % saturation of O2, pH). Correlation between these parameters is established. The balances exist in stationary conditions. But, impact of precipitation is disturbing this state. The hydrodynamic conditions at underground flow and wastewater effluent from the town Cetinje area, has been influence for it, too. The data are referring to small and middle water state.

Batch sorption of metformin hydrochloride (MET) onto a specially designed biochar mix consisting of both macro (MAC) and micro (MIC) algae, rice husk and pine sawdust was conducted. Pyrolysis of both MAC and MIC algae mixture was done followed by chemical activation with hydrogen-peroxide. Additionally, sorption of MET under the influence of pH was separately investigated. Batch studies of isotherms were well described by Freundlich model with high non-linearity and Freundlich exponent values ranged anywhere from 0.12 to 1.54. Heterogeneity of MET adsorption to the bonding sites was attributed to the surface functional groups of the modified biochar. Amongst the four biochars, the activated macroalgae biochar (MACAC) and microalgae biochar (MICAC) depicted favourable adsorption of MET with maximum adsorption at pH 7. Up to 76% of MET removal from the environment was obatained using the MACAC biochar. Scanning electron micrographs coupled with energy dispersive X-ray, as well as elemental analyses confirmed formation of oxygen containing surface functional groups due to activation strengthening chemisorption as the main sorption mechanism. Further, Fourier transform infra-red spectroscopy and other surface functional group analyses along with Zeta potential measurements reinforced our proposed sorption mechanism. Lowest zeta potential observed at pH 7 enhanced the electrostatic force of attraction for both the biochars. Negative zeta potential value of the biochars under different pH indicated potential of the biochars to adsorb other positively charged contaminants. From a techno-economic perspective, capital expenditure cost is not readily available, however, it is envisaged that production of pyrolyzed biochar from algal biomass could make the process economically attractive especially when the biochar could be utilised for high-end applications.

This study investigated catalytic ozone oxidation using a sawdust char (SDW) catalyst to remove hazardous toluene emitted from the chemical industry. The catalyst properties were analyzed by proximate, ultimate, nitrogen adsorption-desorption isotherms, Fourier-transform infrared, and X-ray photoelectron spectroscopy analyses. In addition, hydrogen-temperature programmed reduction experiments were conducted to analyze the catalyst properties. The specific area and formation of micropores of SDC were improved by applying KOH treatment. MnOx/SDC-K3 exhibited a higher toluene removal efficiency of 89.7% after 100 min than MnOx supported on activated carbon (MnOx/AC) with a removal efficiency of 6.6%. The higher (Oₐdₛ (adsorbed oxygen)+Oᵥ(vacancy oxygen))/OL (lattice oxygen) and Mn³⁺/Mn⁴⁺ ratios of MnOx/SDC-K3 than those of MnOx/AC seemed to be important for the catalytic oxidation of toluene.

The narrow acid pH range and the nonselectivity of the dominant •OH limit the Fenton systems to remediate the organic wastewater. Inspired by the role of heme in physiological processes, we employed iron porphyrin as a novel homogeneous catalyst to address this issue. Multiple active species are identified during the activation of H₂O₂, including high-valent iron porphyrin ((por)Fe(IV)) species ((por)Fe(IV)–OH, (por)⁺•Fe(IV)=O) and oxygen-centered radicals (•OH, HO₂•/•O₂⁻), as well as atomic hydrogen (*H) and carbon-centered radicals. With the cooperation of these active species, the degradation of pollutants could be resistant to the interference of concomitant ions and proceed over a wide pH range. This cooperative behavior is further verified by intermediates identified from bisphenol A degradation. Specifically, the presence of *H could facilitate the cleavage of the C–C bond and the addition of unsaturated or aromatic molecules. (Por)⁺•Fe(IV)=O could hydroxylate substrates with an oxygen rebound mechanism. Hydrogen atom abstraction of contaminants could be performed by (por)Fe(IV)–OH to form desaturated products by attacking oxygen-centered radicals. The ecotoxicity of bisphenol A could be significantly decreased through degradation. This study would provide a new approach to wastewater treatment and shed light on the interaction between metalloporphyrin and peroxide in an aqueous solution.

In recent years, the application of green rusts (GRs) for water purification has received significant attention, but its full understanding has not been well achieved. Then, the comprehension about the synthesis and characteristics of GRs can highly favor their decontamination performances for the site-specific conditions. This review comprehensively summarized the synthesis, characteristics and performances of GRs including the GR (Cl⁻), GR (CO₃²⁻) and GR (SO₄²⁻) for sequestration of various aqueous pollutants (e.g., tetrachloride, Cr(VI), Se(VI), and U(VI), etc.). Generally, the different reactivity of GRs toward contaminants is strongly dependent on the GRs’ characteristics (e.g., interlayer distance, specific surface area, and Fe(II) content) and solution chemistry (e.g., pH, background electrolytes, dissolved oxygen, and contaminant concentration, etc.). In addition, the reaction mechanisms of GRs with the contaminants involve the redox reactions, adsorption, catalytic oxidation, interlayer and octahedral incorporation, which can mutually or singly contribute to the decontamination to varying degrees. Particularly, this review addressed the transformation pathways of GRs under various solution chemistry conditions and clarified that the stability of GRs should be the key challenge for the real application. Finally, how to effectively use the GRs for water decontamination was proposed, which will significantly benefit the rational control of environmental pollution.

Understanding the processes that underlay an ecological disaster represents a major scientific challenge. Here, we investigated phytoplankton and zooplankton community changes before and during a fauna mass kill in a European protected wetland. Evidence on gradual development and collapse of harmful phytoplankton blooms, allowed us to delineate the biotic and abiotic interactions that led to this ecological disaster. Before the mass fauna kill, mixed blooms of known harmful cyanobacteria and the killer alga Prymnesium parvum altered biomass flow and minimized zooplankton resource use efficiency. These blooms collapsed under high nutrient concentrations and inhibitory ammonia levels, with low phytoplankton biomass leading to a dramatic drop in photosynthetic oxygenation and a shift to a heterotrophic ecosystem phase. Along with the phytoplankton collapse, extremely high numbers of red planktonic crustaceans-Daphnia magna, visible through satellite images, indicated low oxygen conditions as well as a decrease or absence of fish predation pressure. Our findings provide clear evidence that the mass episode of fish and birds kill resulted through severe changes in phytoplankton and zooplankton dynamics, and the alternation on key abiotic conditions. Our study highlights that plankton-related ecosystem functions mirror the accumulated heavy anthropogenic impacts on freshwaters and could reflect a failure in conservation and restoration measures.

Biodegradation of microplastics (MPs) in contaminated biowastes has received big scientific attention during the past few years. The aim here is to study the impacts of livestock manure biochar (LMBC) on the biodegradation of polyhydroxyalkanoate microplastics (PHA-MPs) during composting, which have not yet been verified. LMBC (10% wt/wt) and PHA-MPs (0.5% wt/wt) were added to a mixture of pristine cow manure and sawdust for composting, whereas a mixture without LMBC served as the control (CK). The maximum degradation rate of PHA-MPs (22–31%) was observed in the thermophilic composting stage in both mixtures. LMBC addition significantly (P < 0.05) promoted PHA-MPs degradation and increased the carbon loss and oxygen loading of PHA-MPs compared to CK. Adding LMBC accelerated the cleavage of C–H bonds and oxidation of PHA-MPs, and increased the O–H, CO and C–O functional groups on MPs. Also, LMBC addition increased the relative abundance of dominant microorganisms (Firmicutes, Proteobacteria, Deinococcus-Thermus, Bacteroidetes, Ascomycota and Basidiomycota) and promoted the enrichment of MP-degrading microbial biomarkers (e.g., Bacillus, Thermobacillus, Luteimonas, Chryseolinea, Aspergillus and Mycothermus). LMBC addition further increased the complexity and connectivity between dominant microbial biomarkers and PHA-MPs degradation characteristics, strengthened their positive relationship, thereby accelerated PHA-MPs biodegradation, and mitigated the potential environmental and human health risk. These findings provide a reference point for reducing PHA-MPs in compost and safe recycling of MPs contaminated organic wastes. However, these results should be validated with other composting matrices and conditions.

Hot moments of nitrous oxide (N₂O) emissions induced by interactions between weather and management make a major contribution to annual N₂O budgets in agricultural soils. The causes of N₂O production during hot moments are not well understood under field conditions, but emerging evidence suggests that short-term fluctuations in soil oxygen (O₂) concentration can be critically important. We conducted high time-resolution field observations of O₂ and N₂O concentrations during hot moments in a dryland agricultural soil in Northern China. Three typical management and weather events, including irrigation (Irr.), fertilization coupled with irrigation (Fer.+Irr.) or with extreme precipitation (Fer.+Pre.), were observed. Soil O₂ and N₂O concentrations were measured hourly for 24 h immediately following events and measured daily for at least one week before and after the events. Soil moisture, temperature, and mineral N were simultaneously measured. Soil O₂ concentrations decreased rapidly within 4 h following irrigation in both the Irr. and Fer.+Irr. events. In the Fer.+Pre. event, soil O₂ depletion did not occur immediately following fertilization but began following subsequent continuous rainfall. The soil O₂ concentration dropped to as low as 0.2% (with the highest soil N₂O concentration of up to 180 ppmv) following the Fer.+Pre. event, but only fell to 11.7% and 13.6% after the Fer.+Irr. and Irr. events, which were associated with soil N₂O concentrations of 27 ppmv and 3 ppmv, respectively. During the hot moments of all three events, soil N₂O concentrations were negatively correlated with soil O₂ concentrations (r = −0.5, P < 0.01), showing a quadratic increase as soil O₂ concentrations declined. Our results provide new understanding of the rapid short response of N₂O production to O₂ dynamics driven by changes in soil environmental factors during hot moments. Such understanding helps improve soil management to avoid transitory O₂ depletion and reduce the risk of N₂O production.

Despite streams and rivers play a critical role as conduits of terrestrially produced organic carbon to the atmosphere, fluvial CO₂ and CH₄ are seldom integrated into regional carbon budgets. High spatial variability hinders our ability to understand how local and longitudinal controls affect underlying processes of riverine CO₂ and CH₄ and challenge the prediction and upscaling across large areas. Here, we conducted a survey of fluvial CO₂ and CH₄ concentrations spanning multiple stream orders within an agriculturally impacted region, the North China Plain. We explored the spatial patterns of fluvial CO₂ and CH₄ concentrations, and then examined whether catchment and network properties and water chemical parameters can explain the variations in both carbon gases. Streams and rivers were systematically supersaturated with CO₂ and CH₄ with the mean concentrations being 111 and 0.63 μmol L⁻¹, respectively. Spatial variability of both gases was regulated by network properties and catchment features. Fluvial CO₂ and CH₄ declined longitudinally and could be modeled as functions of stream order, dissolved oxygen, and water temperature. Both models explained about half of the variability and reflected longitudinal and local drivers simultaneously, albeit CO₂ was more local-influenced and CH₄ more longitudinal-influenced. Our empirical models in this work contribute to the upscaling and prediction of CO₂ and CH₄ emissions from streams and rivers and the understanding of proximal and remote controls on spatial patterns of both gases in agriculturally impacted regions.

The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F⁻ which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., Fe₃O₄, γ-Fe₂O₃, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.