Mineralization Rates Research Articles

Diversity of Microbial Functional Genes Promotes Soil Nitrogen Mineralization in Boreal Forests.

Soil nitrogen (N) mineralization typically governs the availability and movement of soil N. Understanding how factors, especially functional genes, affect N transformations is essential for the protection and restoration of forest ecosystems. To uncover the underlying mechanisms driving soil N mineralization, this study investigated the effects of edaphic environments, substrates, and soil microbial assemblages on net soil N mineralization in boreal forests. Field studies were conducted in five representative forests: Larix principis-rupprechtii forest (LF), Betula platyphylla forest (BF), mixed forest of Larix principis-rupprechtii and Betula platyphylla (MF), Picea asperata forest (SF), and Pinus sylvestris var. mongolica forest (MPF). Results showed that soil N mineralization rates (Rmin) differed significantly among forests, with the highest rate in BF (p < 0.05). Soil properties and microbial assemblages accounted for over 50% of the variability in N mineralization. This study indicated that soil environmental factors influenced N mineralization through their regulatory impact on microbial assemblages. Compared with microbial community assemblages (α-diversity, Shannon and Richness), functional genes assemblages were the most important indexes to regulate N mineralization. It was thus determined that microbial functional genes controlled N mineralization in boreal forests. This study clarified the mechanisms of N mineralization and provided a mechanistic understanding to enhance biogeochemical models for forecasting soil N availability, alongside aiding species diversity conservation and fragile ecosystem revitalization in boreal forests.

Visible-to-near-infrared spectroscopy for prediction of soil nitrogen mineralization after sample stratification by textural homogeneity criteria

On-time and accurate estimation of the soil nitrogen mineralization rate (SNMR) is critical for nitrogen (N) management and protecting the environment. This study evaluated the performance of a visible-to-near-infrared reflectance (vis-NIR) spectroscopy for predicting SNMR for four texture groups. A total of 62 topsoil samples were collected from 17 management zones distributed over four fields and incubated with seven destructive sampling events. Samples were analysed for total mineral N (NH4++NO3–) content and scanned using a vis-NIR sensor simultaneously at each of the seven-sampling times. Four partial least squares regression models were calibrated and validated for four textural groups (groups- 1– 4) identified over the United State Department of Agriculture (USDA) texture triangle. Prediction accuracies indicated that vis-NIR sensor was moderately to highly accurate for predicting SNMR, while observing variable accuracies across texture groups. The highest accuracy was obtained for group 1 (sandy-loam; coefficient of determination, R2 = 0.90; root mean square error, RMSE = 0.04 mg N kg−1 soil day−1), successively followed by group 2 (mostly loam; R2 = 0.80, RMSE = 0.05 mg N kg−1 soil day−1) group 4 (mostly silt; R2 = 0.66, RMSE = 0.08 mg N kg−1 soil day−1), and group 3 (silt-loam; R2 = 0.44, RMSE = 0.08 mg N kg−1 soil day−1). Variable importance in projection score revealed that the key spectral bands to predict SNMR were in 2150 – 2260 nm and 2470 – 2480 nm, resembling the key bands associated with soil organic compounds and clay minerals. In-advance texture information required for soil stratification is regarded a limitation of the proposed approach. In conclusion, vis-NIR holds potential for a rapid estimation of SNMR when samples are stratified into similar texture groups in advance, however, confirmatory research will be needed to validate the current findings for soils from different origin and under different management.

Tracking atrazine degradation in soil combining 14C-mineralisation assays and compound-specific isotope analysis

The quantification of pesticide dissipation in agricultural soil is challenging. In this study, we investigated atrazine biodegradation in both liquid and soil experiments bioaugmented with distinct atrazine-degrading bacterial isolates. This was achieved by combining 14C-mineralisation assays and compound-specific isotope analysis of atrazine. In liquid experiments, the three bacterial isolates mineralised over 40% of atrazine, demonstrating their potential for extensive degradation. However, the kinetics of mineralisation and degradation varied among the isolates. Carbon stable isotope fractionation was similar for Pseudomonas isolates ADPT34 and ADP2T0, but slightly higher for Chelatobacter SR27. In soil experiments, atrazine primarily degraded into atrazine-desethyl, while atrazine-hydroxy was mainly observed in experiments with SR27. Atrazine mineralisation in soil by ADPT34 and SR27 exceeded 40%, whereas ADP2T0 exhibited a mineralisation rate of 10%. In experiments with ADPT34 and SR27, atrazine 14C-residues were predominantly found in the non-extractable fraction, whereas they accumulated in the extractable fraction in the experiment with ADP2T0. Compound-specific isotope analysis (CSIA) relies on changes of stable isotope ratios and holds potential to evaluate herbicide transformation in soil. CSIA of atrazine indicated atrazine biodegradation in water and solvent extractable soil fractions and varied between 29% and 52%, depending on the bacterial isolate. Despite atrazine degradation in both soil fractions, a significant portion of atrazine residues persisted, depending on the bacterial degrader, initial cell concentration, and mineralisation and degradation rates. Overall, our approach can aid in quantifying atrazine persistence and degradation in soil, and in optimizing bioaugmentation strategies for remediating soils contaminated with persistent herbicides.

Alfalfa-livestock system promotes the accumulation of soil organic carbon in a semi-arid marginal land

Developing cropland in marginal lands presents a potential solution to address food security challenges. However, the low organic carbon (C) content in these soils severely constrains crop productivity, and developing cropland aggravates the loss of soil organic carbon (SOC). Therefore, it is essential to elevate the SOC content via a profitable solution for food production. In this study, we examine the impacts of land use changes (fallow, cropland, and Alfalfa-livestock system [AL]) over 12 years on SOC content, composition, and mineralization rate in a semiarid marginal land. SOC was categorized into three components: plant necromass C, microbial necromass C, and "other C." We utilized lignin and amino sugars as biomarkers to assess plant and microbial necromass C content, respectively, and the remaining component was other C. We found that AL increased SOC contents in 0–15 cm by 142 % and 123 % compared to fallow and cropland. Other C was the main factor driving SOC accumulation in AL compared to fallow and cropland, which contributed 2 times more than microbial necromass C (63 % VS 31 %), while plant necromass contributed less than 7 %. Furthermore, AL decreased C mineralization per unit of SOC than fallow and cropland due to increased soil available N contents. In conclusion, AL facilitated a rapid increase in SOC contents on marginal lands by fostering the accumulation of microbial necromass C and other C while inhibiting SOC mineralization. This finding helps improve the productivity and sustainability of marginal croplands.

Effects of Incubation Temperature and Sludge Addition on Soil Organic Carbon and Nitrogen Mineralization Characteristics in Degraded Grassland Soil

Elucidating the characteristics and underlying mechanisms of soil organic carbon (SOC) and nitrogen mineralization in the context of sludge addition is vital for enhancing soil quality and augmenting the carbon sink capacity of soil. This study examined the chemical properties, enzyme dynamics, and organic carbon and nitrogen mineralization processes of soil from degraded grasslands on the Loess Plateau at various incubation temperatures (5, 15, 25, and 35 °C) and sludge addition rates (0%, 5.0%, 10.0%, and 20.0%) through a laboratory incubation experiment. The results showed that incubation temperature, sludge addition, and their interactive effects significantly altered the soil enzyme C:N, C:P, and N:P stoichiometries. The cumulative mineralization rates of SOC and nitrogen increased significantly with increasing incubation temperature and sludge addition rate. Principal component analysis revealed a significant linear correlation between cumulative SOC and nitrogen mineralization. Random forest analysis indicated that β-1,4-Glucosidase (BG), β-1,4-N-acetyglucosaminidase (NAG), cellobiohydrolase (CBH), ammonium nitrogen (NO3−), enzyme C:P ratio, alkaline phosphatase (ALP), and incubation temperature were crucial determinants of cumulative SOC mineralization. Structural equation modeling demonstrated that sludge addition, NO3−, NAG, ALP, and enzyme C:P positively impacted SOC mineralization, whereas dissolved organic carbon and BG had negative impacts. Conversely, incubation temperature negatively affected soil nitrogen mineralization, whereas NO3−, available phosphorus, and ALP contributed positively. Sludge addition and temperature indirectly modulated soil net nitrogen mineralization by altering soil chemical properties and enzyme activities. These findings underscore the role of SOC and nitrogen mineralization as indicators for evaluating soil nutrient retention capabilities.

Do government resource management policies influence green productivity? New perspectives from fintech and digital resource policy in China

Achieving sustainable development necessitates the exploration of innovative approaches towards low-carbon development and efficient resource management. By adopting the low-carbon city pilot project as a policy shock of Government Resource Management Policies (GRMP), we aim to scrutinize the nuanced impacts of GRMP on green productivity (GTFP). Using the difference-in-difference (DID) approach and panel data from 280 cities in China. Our findings reveal a significant relationship between GRMP and GTFP. In the immediate short-term, GRMP exhibits a negative effect on GTFP growth, followed by a long-term positive promoting effect. A detailed temporal analysis uncovers an “inverted N″ time-period effect of GRMP on GTFP growth. Further exploration into the mechanisms driving this influence reveals three key aspects: the reduction of natural resources consumption and the promotion of low-carbon production (LCP), low-carbon transportation (LCT), and low-carbon industries (LCI). While the regulated effect of financial technology resources on the relationship between GRMP and GTFP is positive but statistically insignificant, the regulated effect of digital resource policy emerges as positive and significant. Additionally, the regulated effect of mineral and forest resource coverage rate is positive but not statistically significant in the context of the influence of GRMP on GTFP. This comprehensive analysis contributes to our understanding of the dynamic interplay between policy interventions, resource management, and sustainable development in the Chinese urban landscape.

Subcritical water delamination: A promising path to efficient recycling of critical minerals

The objective of this study is to degrade the polymer layers within crystalline silicon (c-Si) photovoltaic modules and delaminate the essential valuable minerals for recycling, employing solely the thermodynamic attributes of water under subcritical conditions and abstaining from the utilization of chemical solvents. The c-Si wafer was successfully delaminated from the polymer structures at 200 °C, 100 bar for 30 min in a high-pressure reactor and ground in a planetary ball mill, where the experimental conditions were optimized for energy consumption using a Box-Behnken design. Hydrothermal subcritical delamination process provides structural changes in the polymer layers due to swelling of the ethylene vinyl acetate (EVA) and hardening of the backsheet. The energy consumption measured at the laboratory scale corresponds to the optimum response value of 0.132 kWh, demonstrating the effectiveness of the study under short-term and stable conditions.The c-Si wafer analyzed using techniques such as EDXRF, XRD, TGA, FTIR, and SEM/EDS. 87.5% Si, 1.95% aluminum, 1.12% silver, and 1.23% other metals were recovered from the solar cell. However, an oxidation rate of 6.71% by mass was detected in the c-Si wafer. The recovery rate of valuable minerals by ignoring oxidation is 98.4% of the total mass.

The practical utility of nitrogen doped TiO2 as a photocatalyst for the oxidative removal of gaseous formaldehyde

This study reports the development of nitrogen-doped TiO2 (N–TiO2: N/Ti molar ratio = 1) photocatalyst with the enhanced photoelectronic properties for the phtocatalytic oxidation (PCO) of formaldehyde (FA). The N–TiO2 photocatalyst is coated with ceramic beads and placed in a packed-bed tube reactor to examine the PCO-based mineralization of FA vapor (100 - 500 ppm) under ultraviolet (UV)-A illumination (32 W light source) with the control of flow rate (100–500 mL min−1), O2 (0–21%), and relative humidity (RH: 0–100%). Accordingly, the N-TiO2 in dry conditions showcases 100% degradation of 100 ppm FA with high stability over 5 reuse cycles (compared to the P25 (75.9%) and bare TiO2 (69.2%)) at a flow rate of 100 mL min−1 and a 21 % O2 level (quantum yield = 1.72.E−02 molecules photon−1 and space-time yield = 3.44.E−03 molecules photon−1 mg−1). The superior performance of N–TiO2 may reflect the combination of N/O atoms in the crystal structure to enhance the photo-redox reactivities with the heightened valence band enegry and prolonged lifespan of charge carrier (1.34 ns) relative to 1.04 ns of P25 and 1 ns of pure (anatase) TiO2. The PCO efficiency of N–TiO2 increases by around 1.6 times in slightly humid conditions (74.6%: RH 20%) compared to dry conditions (47%: RH 0%) while the absence of oxygen (at 0% O2) reduces it significantly down to 13.6%. In situ diffuse reflectance infrared Fourier transform spectroscopy and electron paramagnetic resonance studies confirm the critical role of O2 and H2O vapor on the enhanced FA mineralization rate (CO2 yield = 91 %) through the generation of •O2-/•OH oxidative radicals. This study offers deep insights into the practical utility of N–TiO2 for the photocatalytic mineralization of aldehyde VOCs.

Legacy soil phosphorus bioavailability in tropical and temperate soils: Implications for sustainable crop production

Improving phosphorus (P) use efficiency is key to improving the productivity and sustainability of cropping systems and slowing the exploitation rate of mineral P resources required for fertilizer production. At present, large amounts of added P in fertilizers and manure each year are retained in the soil and are not used by the crop. This ‘legacy P’ progressively accumulates in soil and represents an untapped P resource in tropical soils while in temperate soils it contributes to eutrophication. In the context of legacy P, the aim of this study was to quantify changes in soil P pools of contrasting bioavailability (determined using conventional chemical extraction procedures) during 12 successive brachiaria (Urochloa ruziziensis) cropping cycles in which no additional P was added. The study was undertaken in the greenhouse with 10 tropical (Brazil) and 6 temperate (UK) agricultural topsoils. Above-ground dry matter yield (DM) and P offtake was measured at each harvest alongside operationally-defined measures of the labile, moderately-labile and non-labile P pools at the start and end of the experiment. Over twelve repeated cultivation cycles, brachiaria demonstrated an ability to efficiently mine legacy P from all measurable soil pools across both sets of soils. This included the depletion of up to 87 % of non-labile soil P in some soils from the UK and up to 66 % from soils in Brazil after one year. While the amounts of initial labile P showed the closest positive relationship with plant P export, contrary to expectation the non-labile P pool also clearly contributed to plant nutrition across all the soils. As a cover crop, brachiaria clearly possesses traits which enable both the solubilization and efficient capture of soil P that can be harnessed to actively recycle historically non recalcitrant soil P fractions. Incorporating brachiaria into crop rotations or intercropping systems therefore shows promise as a strategy to enhance the longer-term sustainability of soil P management.

Crop Diversification and Fertilization Strategies in a Rainfed System with Drought Periods

Crop diversification and the reduction of nitrogen (N) inputs are key issues in the EU for more sustainable agriculture. An experiment was set up in a semiarid rainfed Mediterranean system. Our hypothesis was that these challenges could be addressed by introducing new crops and using pig slurries (PSs). The experimental factors were N fertilization at sowing (with or without PS) combined (according to a split-block design) with N fertilization as topdressing (the control, two N mineral rates, and two N rates from PS). Barley, rapeseed, and pea performances were evaluated in two different crop sequences: (i) barley–rapeseed or rapeseed–barley after a fallow season, and (ii) barley–pea or pea–barley after a fallow season followed by a non-fertilized barley crop. The results of the four-year study demonstrated that under a spring drought risk, barley performed better than peas in terms of relative crop yield maintenance. After fallow, N can be saved while maintaining the yields and total biomass of barley and rapeseed. In the second crop sequence, maximum pea and barley yields were associated with a minimum topdressing of 60 or 120 kg mineral N ha−1, respectively. However, slurry fertilization at sowing also allowed the highest yields for barley. Rapeseed and peas can be introduced to reduce N fertilization inputs. However, the obtained yield plateau for pea and rapeseed (3 and 4 Mg ha−1, respectively) and the effect of a yield spring drought on pea yields (50% reduction) might be a constraint for the success of EU policies on crop diversification.

Improved peracetic acid activation under simulated solar-light irradiation by regulating shells of Cu2O: In-situ photothermal activation

Advanced oxidation processes based on light-mediated peracetic acid (PAA) activation are novel degradation systems for wastewater purification. In this work, different shells of Cu2O are controllably synthesized and used to activate PAA under simulative solar light. Interestingly, the kobs in the system without temperature control is 2.47 times that in the temperature-controlled system, implying the important role of the photothermal conversion effect in PAA activation. Reactive oxygen species identification demonstrates that photothermal promotes the decomposition of PAA into radical OH with higher redox potential instead of R–O, which together with non-radical 1O2 achieves a high mineralization rate (72.49%). The core–shell structure enhances light absorption and photogenerated charge separation of Cu2O, thereby improving photothermal conversion efficiency. Meantime, the in-situ photothermal conversion effect expedites the diffusion of ROS and the cycle of active Cu(Ⅱ)/Cu(Ⅰ) ultimately achieves the high-efficiency and long-lasting PAA activation. This work provides novel strategies for solar energy utilization and PAA activation processes in wastewater purification.

Novel Approach to Photocatalytic Removal of Linezolid by Advanced Nano-Biochar/Bismuth Oxychloride Hybrid.

Herein, we introduce an innovative nanohybrid material for advanced wastewater treatment, composed of Corchorus olitorius-derived biochar and bismuth oxychloride (Biochar/Bi12O17Cl2), demonstrated in a solar photoreactor. This work focuses on the efficient degradation of linezolid (LIN), a persistent pharmaceutical pollutant, utilizing the unique (photo)catalytic capabilities of the nanohybrid. Compared with its individual components, the biochar/Bi12O17Cl2 hybrid exhibits a remarkable degradation efficiency of 82.6% for LIN, alongside significant chemical oxygen demand (COD) and total organic carbon (TOC) mineralization rates of 81.3 and 75.8%, respectively. These results were achieved within 3 h under solar irradiation, using an optimal composite dose of 125 mg/L at pH 4.3 ± 0.45, with an initial COD and LIN concentrations of 1605 and 160.8 mg/L and TOC of 594.3 mg/L. The nanohybrid's stability across five cycles of use demonstrates its potential for repeated applications, with degradation efficiencies of 82.6 and 77.9% in the first and fifth cycles, respectively. This indicates the biochar/Bi12O17Cl2 composite's suitability as a sustainable and cost-effective solution for the remediation of heavily contaminated waters. Further, the degradation pathway proposed the degradation of all of the generated intermediates to a single-ring compound. Contributing to the development of next-generation materials for environmental remediation, this research underscores the critical role of nanotechnology in enhancing water quality and ecosystem sustainability and addressing the global imperative for clean water access and environmental preservation.

Mealworm Larvae Frass Exhibits a Plant Biostimulant Effect on Lettuce, Boosting Productivity beyond Just Nutrient Release or Improved Soil Properties

There is a need for alternatives or complements to synthetic fertilizers to enhance agricultural sustainability. Applying organic amendments can play a significant role in this. Insect droppings show high potential, though studies evaluating their agronomic value have only recently begun to emerge. This study compared black soldier fly (Hermetia illucens L.) and mealworm (Tenebrio molitor L.) larvae frass with another organic amendment (Nutrimais) derived from composting forestry, agro-industrial, and domestic waste. The experiment also included ammonium nitrate at two rates [the same as the organic amendments, 50 kg ha–1 nitrogen (N) (FullR), and half that rate (HalfR)] and an unfertilized control. The study spanned two growth cycles of lettuce (Lactuca sativa L.) grown in pots, followed by unfertilized oats (Avena sativa L.) to assess the residual effects of the fertilizing treatments. Mealworm larvae frass mineralized rapidly, with an apparent N recovery of 37.4% over the two lettuce growth cycles, indicating its high availability to soil heterotrophic microorganisms. The average dry matter yield (DMY) of lettuce was the highest among all treatments (12.8 and 9.8 g plant–1 in the first and second lettuce cycles), even compared to the FullR treatment (12.2 and 7.8 g plant–1), though without significant differences. Although mealworm larvae frass exhibited a high mineralization rate, the DMY cannot be attributed solely to N supply, as plants in the FullR treatment showed better N nutritional status. Mealworm larvae frass provided strong evidence of a plant biostimulant effect, not explained by the variables measured in this study. Black soldier fly larvae frass exhibited typical behavior of a moderately reactive organic amendment, while Nutrimais showed low reactivity, with a near-neutral mineralization/immobilization balance. The results suggest mealworm larvae frass is recommended for early maturing vegetable crops, whereas Nutrimais appears more suitable for perennial crops with low short-term nutrient requirements.

Effect of chloride ions on persulfate/UV-C advanced oxidation of an alcohol ethoxylate (Brij 30)

In the present study, the effect of chloride ions on the oxidative degradation of an alcohol ethoxylate (Brij 30) by persulfate (PS)/UV-C was experimentally explored using Brij 30 aqueous solution (BAS) and a domestic wastewater treatment plant effluent spiked with Brij 30. Brij 30 degradation occurred rapidly during the early stages of oxidation without affecting the water/wastewater matrix. Mineralization of intermediates of Brij 30 degradation markedly influenced by presence of chloride ions. Chloride ions at concentrations up to 50 mg/L accelerated the mineralization through reactions involving reactive chlorine species, which reduced the sink of SO4·− by Cl− scavenging at both initial pH of 6.0 and 3.0 in the case of BAS. The fastest mineralization was achieved under acidic conditions. The WWTP effluent matrix significantly influenced mineralization efficacy of the intermediates. Co-existence of HCO3-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{HCO}}_{3}^{-}$$\\end{document} and Cl− anions accelerated the mineralization of degradation products. Organic matter originating from the WWTP effluent itself had an adverse effect on the mineralization rate. The positive effects of organic and inorganic components present in the WWTP effluent were ranked in the following order of increasing influence: (Organic matter originating from the effluent + Cl− +HCO3-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{HCO}}_{3}^{-}$$\\end{document}) < (Cl−) < (Cl− +HCO3-\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{HCO}}_{3}^{-}$$\\end{document}).

FeCo@hydrochar nanocomposites as efficient peroxymonosulfate activator for organic pollutant degradation.

Sulfate radical-based advanced oxidation processes (SR-AOPs) are renowned for their exceptional capacity to degrade refractory organic pollutants due to their wide applicability, cost-effectiveness, and swift mineralization and oxidation rates. The primary sources of radicals in AOPs are persulfate (PS) and peroxymonosulfate (PMS) ions, sparking significant interest in their mechanistic and catalytic aspects. To develop a novel nanocatalyst for SR-AOPs, particularly for PMS activation, we synthesized carbon-coated FeCo nanoparticles (NPs) using solvothermal methods based on the polyol approach. Various synthesis conditions were investigated, and the NPs were thoroughly characterized regarding their structure, morphology, magnetic properties, and catalytic efficiency. The FeCo phase was primarily obtained at [OH-] / [Metal] = 26 and [Fe] / [Co] = 2 ratios. Moreover, as the [Fe]/[Co] ratio increased, the degree of xylose carbonization to form a carbon coating (hydrochar) on the NPs also increased. The NPs exhibited a spherical morphology with agglomerates of varying sizes. Vibrating-sample magnetometer analysis (VSM) indicated that a higher proportion of iron resulted in NPs with higher saturation magnetization (up to 167.8 emu g-1), attributed to a larger proportion of FeCo bcc phase in the nanocomposite. The best catalytic conditions for degrading 100ppm Rhodamine B (RhB) included 0.05g L-1 of NPs, 2mM PMS, pH 7.0, and a 20-min reaction at 25°C. Notably, singlet oxygen was the predominant specie formed in the experiments in the SR-AOP, followed by sulfate and hydroxyl radicals. The catalyst could be reused for up to five cycles, retaining over 98% RhB degradation, albeit with increased metal leaching. Even in the first use, dissolved Fe and Co concentrations were 0.8 ± 0.3 and 4.0 ± 0.5mg L-1, respectively. The FeCo catalyst proved to be effective in dye degradation and offers the potential for further refinement to minimize Co2+ leaching.

Synthesis of new Cu/Zn (II) complexes for sonophotocatalysis for mineralization of pesticides and agrochemical wastewater

In the present work synthesis of new semiconductor-based Schiff’s base Cu/Zn-complexes for sonophoto mineralization of agrichemical wastewater (ACWW), pesticides, and various types of industrial wastewater, are reported under ultrasonicated and visible light treatment circumstances. The newly prepared ligands and [Cu2(HBAPAT)(OAc)2] and [Zn2(HBAPAT)(OAc)2] complexes are systematically analyzed with several spectroscopic methods and confirmed as 2:1 ratio of Cu2+/Zn2+ ions and ligand with distorted octahedral structure. These reported complexes are used for the sonophoto mineralization of ACWW and pesticides under ultrasonication and visible light treatment. With the increase in the dosage of complexes, the rate of mineralization of ACWW increased. Further, ACWW samples were analyzed through HPLC and mass spectral techniques for identification of various pesticides present in wastewater samples, before and after sonophotocatalysis. The active species for sonophotocatalysis of ACWW were identified by EPR, scavengers for superoxide radicals and metal organic thin-film transistor study for electrons. The metal complex [Cu2(HBAPAT)(OAc)2] is with better efficiency than [Zn2(HBAPAT)(OAc)2] for mineralization of ACWW and pesticides are reported using indigenous sonophotocatalytic reactor.

Oxidation and mineralization rates of harmful organic chemicals in hydroxyl radical induced reactions

In most of advanced oxidation processes (AOPs) used to destroy harmful organic chemicals in water/wastewater hydroxyl radical (•OH) reactions oxidize (increasing the oxygen/carbon ratio in the molecules) and mineralize (transforming them to inorganic molecules, H2O, CO2, etc.) these contaminants. In this paper, we used the radiolysis of water to produce •OH and characterised the rate of oxidation and mineralization by the dose dependences of the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) content values. Analysis of the dose dependences for 34 harmful organic compounds showed large differences in the oxidation and mineralization rates and these parameters are characteristic to the given group of chemicals. E.g., the rate of oxidation is relatively low for fluoroquinolone antibiotics; it is high for β-blocker medicines. Mineralization rates are low for both fluoroquinolones and β-blockers. The one-electron-oxidant •OH in most cases induces two − four-electron-oxidations. Most of the degradation takes place gradually, through several stable molecule intermediates. However, based on the results it is likely, that some part of the oxidation and mineralization takes place parallel. The organic radicals formed in •OH reactions react with several O2 molecules and release several inorganic fragments during the radical life cycle.

An innovative Zn3In2S6/ZnIn2S4 homojunction photocatalyst with enhanced interfacial charge transfer for the highly efficient degradation of tetracycline under visible radiation

The interfacial charge transfer ability is a decisive factor influencing the photocatalytic performance of composite photocatalysts. Compared with heterojunctions that combine two or more semiconductors with different properties, homojunctions that combine two semiconductors with similar properties can accelerate the interfacial charge shift and achieve higher photocatalyticability. In this study, a Zn3In2S6/ZnIn2S4 homojunction photocatalyst (ZIS-5) with a Zn3In2S6 to ZnIn2S4 molar ratio of 5:1 was synthesized by selecting Zn3In2S6 nano-microspheres as the substrate material and growing ZnIn2S4 flocs on the nano-microspheres. The photocatalytic performance of the ZIS-5 homojunction was assessed by using tetracycline (TC) as a typical pollutant. The photocatalytic performance and mineralization rate of the ZIS-5 homojunction were significantly improved compared with those of Zn3In2S6 and ZnIn2S4, and its photocatalytic performance was increased by 10.2% and 20.9%, compared with Zn3In2S6 and ZnIn2S4, respectively, while the mineralization rate was enhanced by 22.78% and 43.28%, respectively. The results of the comparison experiment revealed that the interfacial electron transfer ability of the ZIS-5 homojunction is 1.6 times that of the g-C3N4/ZnIn2S4-5 heterojunction. The density functional theory (DFT) computation and Mott–Schottky plots verified the formation of an internal electric field. The toxicity analysis showed that the ZIS-5 homojunction system effectively reduced the toxicity of TC. This work supplies a valuable route for inventing catalysts with efficient photocatalytic performances.

Grazing stabilized carbon and nitrogen pools by reducing carbon and net nitrogen mineralization after soil nutrients were added

Nutrient addition and grazing exclusion are effective methods to restore carbon and nitrogen pools in degraded grassland. However, how the combination of nutrient addition and grazing exclusion affect carbon and nitrogen pools through carbon and net nitrogen mineralization is unknown. A 56-day incubation study examined the effect of no additive (control — CK) and, the addition of sucrose (S), urea (U), sucrose + urea (SU), and yak dung (D) to the soil of grazed and fenced alpine grassland on carbon and net nitrogen mineralization. The 15N-tracer technique was used to determine nitrogen utilization by soil microorganisms. Nutrient addition with grazing exclusion increased soil organic carbon, microbial biomass carbon (MBC), inorganic nitrogen, and dissolved organic nitrogen (DON), and promoted carbon and net nitrogen mineralization in early incubation. The 15N recovery rate in soil was 4.5 to 21.7 % and decreased with time. Grazing exclusion altered the drivers of the carbon and net nitrogen mineralization rates, and increased carbon and net nitrogen mineralization rates by enhancing MBC and DON. The results indicated that nutrient addition: (1) decreased soil carbon and nitrogen stability by increasing nutrient availability and enhancing carbon and net nitrogen mineralization rates; and (2) in combination with grazing exclusion promoted carbon and net nitrogen mineralization. Consequently, soil carbon and net nitrogen mineralization depended on nutrient availability, and grazing stabilized soil carbon and nitrogen pools by reducing carbon and net nitrogen mineralization. The results could provide a theoretical basis for alpine grassland management.

BiOIO3/Bi12SiO20 core-shell S-type heterojunction for efficient photocatalytic removal of bisphenol A: Performance and mechanism study

The construction of S-type heterostructures is a very promising strategy for removing bisphenol A. In this paper, BiOIO3/Bi12SiO20 S-type heterojunction with a core-shell structure was firstly prepared by a simple hydrothermal reaction. In the photocatalytic experiment of degrading bisphenol A, the degradation efficiency of bisphenol A by the BiOIO3/Bi12SiO20 catalyst was as high as 96 % within 20 min, and the mineralization rate also reached 63.2 %. In comparison to BiOIO3 (0.174 × 10−1 min−1) and Bi12SiO20 (0.127 × 10−1 min−1), respectively, the degradation rate k of bisphenol A by 11 % BIS was 1.724 × 10−1 min−1, which was 10 and 13 times greater. Even under the condition of pH 4, the photocatalytic degradation rate was as high as 91 % in 30 min. Therefore, 11 % BIS exhibited the highest catalytic performance and good stability. We also used the successfully synthesized catalysts to degrade bisphenol A in tap water and wastewater after secondary treatment in a wastewater treatment plant, and the degradation rates reached 85.7 % and 71.1 %, respectively, after 30 min of photocatalysis, demonstrating the applicability of the catalysts in practice. Meanwhile, the BET test also showed that the construction of S-type heterojunction increased the specific surface area and increased the active sites for the reaction, thus improving the photocatalytic effect. The formation mechanism of the S-type heterojunction was clarified by quenching experiments, ESR analysis, the UPS test, and other characterizations. It was proved that ·O2− was the main active species in the process of photocatalytic degradation of bisphenol A. The attack sites of bisphenol A were determined by density functional theory calculation, and the degradation pathway was proposed by liquid chromatography-mass spectrometry analysis. The toxicity changes of the photocatalytic degradation of bisphenol A were also investigated by the toxicity experiment of Escherichia coli. The development of this bismuth-based material's core-shell S-type heterostructure offers inspiration for the creation of high-performance catalysts.