Distinct roles of pH and organic ligands in the dissolution of goethite by cysteine

Electron shuttles such cysteine play an important role in Fe cycle and its availability in soils,while the roles of pH and organic ligands in this process are poorly understood.Herein,the reductive dissolution process of goethite by cysteine were explored in the presence of organic ligands.Our results showed that cysteine exhibited a strong reactivity towards goethite-a typical iron minerals in paddy soils with a rate constant ranging from 0.01 to0.1 hr-1.However,a large portion of Fe(Ⅱ) appeare...     

Surface protection method for the magnetic core using covalent organic framework shells and its application in As(III) depth removal from acid wastewater

Fe₃O₄-based materials are widely used for magnetic separation from wastewater. However, they often suffer from Fe-leaching behavior under acidic conditions, decreasing their activity and limiting sustainable practical applications. In this study, covalent organic frameworks (COFs) were used as the shell to protect the Fe₃O₄ core, and the Fe₃O₄@COF core-shell composites were synthesized for As(III) removal from acid wastewater. The imine-linked COFs can in situ grow on the surface of the Fe₃O₄ core layer by layer with [COFs/Fe₃O₄]_mol ratio of up to 2:1. The Fe-leaching behavior was weakened over a wide pH range of 1-13. Moreover, such composites keep their magnetic characteristic, making them favorable for nanomaterial separation. As(III) batch adsorption experiments results indicated that, when COFs are used as the shell for the Fe₃O₄ core, a balance between As(III) removal efficiencies and the thickness of the COF shell exists. Higher As(III) removal efficiencies are obtained when the [COFs/Fe₃O₄]_mol ratios were < 1.5:1, but thicker COF shells were not beneficial for As(III) removal. Such composites also exhibited better As(III) removal performances in the pH range of 1–7. Over a wide pH range, the zeta potential of Fe₃O₄@COF core-shell composites becomes more positive, which benefits the capture of negative arsenic ions. In addition, thinner surface COFs were favorable for mass transfer and facilitating the reaction of Fe and As elements. Our study highlights the promise of using COFs in nanomaterial surface protection and achieving As(III) depth removal under acidic conditions.     

Fate of nitrogen during composting of chicken litter

Chicken litter (a mixture of chicken manure, wood shavings, waste feed, and feathers) was composted in forced-aeration piles to understand the changes and losses of nitrogen (N) during composting. During the composting process, the chemical [different N fractions, organic matter (OM), organic carbon (C), and C:N ratio], physical, and microbial properties of the chicken litter were examined. Cumulative losses and mass balances of N and organic matter were also quantified to determine actual losses during composting. The changes in total N concentration of the chicken litter piles were essentially equal to those of the organic N. The inorganic N concentrations were low, and that organic N was the major nitrogenous constituent. The ammonium (NH(4)(+))-N concentration decreased dramatically during first 35 days of composting. However, the rapid decrease in NH(4)(+)-N during composting did not coincide with a rapid increase in (NO(3)(-)+NO(2)(-))-N concentration. The concentration of (NO(3)(-)+NO(2)(-))-N was very low (<0.5 g kg(-1)) at day 0, and this level remained unchanged during the first 35 days of composting suggesting that N was lost during composting. Losses of N in this composting process were governed mainly by volatilization of ammonia (NH(3)) as the pile temperatures were high and the pH values were above 7. The narrow C:N ratio (<20:1) have also contributed to losses of N in the chicken litter. The OM and total organic C mass decreased with composting time. About 42 kg of the organic C was converted to CO(2). On the other hand, 18 kg was lost during composting. This loss was more than half (59%) of the initial N mass of the piles. Such a finding demonstrates that composting reduced the value of the chicken litter as N fertilizer. However, the composted chicken contained a more humified (stabilized) OM compared with the uncomposted chicken litter, which would enhance its value as a soil conditioner.     

Atmospheric fine particles in a typical coastal port of Yangtze River Delta

In recent decades, coastal ports have experienced rapid development and become an important economic and ecological hub in China. Atmospheric particle is a research hotspot in atmospheric environmental sciences in inland regions. However, few studies on the atmospheric particle were conducted in coastal port areas in China, which indeed suffers atmospheric particle pollution. Lack of the physicochemical characteristics of fine particles serves as an obstacle toward the accurate control for air pollution in the coastal port area in China. Here, a field observation was conducted in an important coastal port city in Yangtze River Delta from March 6 to March 19, 2019. The average PM_2.5 concentration was 63.7 ± 27.8 μg/m³ and NO₃^—, SO₄^2—, NH₄⁺, and organic matter accounted for ~60% of PM_2.5. Fe was the most abundant trace metal element and V as the ship emission indicator was detected. Transmission electron microscopy images showed that SK-rich, soot, Fe, SK-soot and SK-Fe were the major individual particles in the coastal port. V and soluble Fe were detected in sulfate coating of SK-Fe particles. We found that anthropogenic emissions, marine sea salt, and secondary atmosphere process were the major sources of fine particles. Backward trajectory analysis indicated that the dominant air masses were marine air mass, inland air mass from northern Zhejiang and inland-marine mixed air mass from Shandong and Shanghai during the sampling period. The findings can help us better understand the physicochemical properties of atmospheric fine particles in the coastal port of Eastern China.     

Interactions of sulfuric acid with common atmospheric bases and organic acids: Thermodynamics and implications to new particle formation

Interactions of the three common atmospheric bases, dimethylamine ((CH₃)₂NH), methylamine (CH₃NH₂), ammonia (NH₃), all considered to be efficient stabilizers of binary clusters in the Earth's atmosphere, with H₂SO₄, the key atmospheric precursor, and 14 common atmospheric organic acids (COAs) (formic, acetic, oxalic, malonic, succinic, glutaric acid, adipic, benzoic, phenylacetic, pyruvic, maleic acid, malic, tartaric and pinonic acids) have been studied using the density functional theory (DFT) and composite high-accuracy G3MP2 method. The thermodynamic stability of mixed (COA)(H₂SO₄), (COA)(B1), (COA)(B2) and (COA)(B3) dimers and (COA)(H₂SO₄)(B1), (COA)(H₂SO₄)(B2) and (COA)(H₂SO₄)(B3) trimers, where B1, B2 and B3 refer to (CH₃)₂NH, CH₃NH₂ and NH₃, respectively, have been investigated and their impacts on the thermodynamic stability of clusters containing H₂SO₄ have been studied. Our investigation shows that interactions of H₂SO₄ with COA, (CH₃)₂NH, CH₃NH₂ and NH₃ lead to the formation of more stable mixed dimers and trimers than (H₂SO₄)₂ and (H₂SO₄)₂(base), respectively, and emphasize the importance of common organic species for early stages of atmospheric nucleation. We also show that although amines are generally confirmed to be more active than NH₃ as stabilizers of binary clusters, in some cases mixed trimers containing NH₃ are more stable thermodynamically than those containing CH₃NH₂. This study indicates an important role of COA, which coexist and interact with that H₂SO₄ and common atmospheric bases in the Earth atmosphere, in formation of stable pre-nucleation clusters and suggests that the impacts of COA on new particle formation (NPF) should be studied in further details.     

Effect of natural organic matter on thallium and silver speciation

Natural organic matter (NOM) is known to play an important role in the transport and binding of trace metal elements in aquatic and soil systems. Thallium is a pollutant for which the extent of the role played by NOM is poorly known. Consequently, this study investigates thallium(I) and its complexation to a purified humic substance as proxy for NOM. Experiments were performed with the Donnan Membrane Technique to separate, for the first time, the free Tl⁺ ion from its complexed form in the bulk solution. Various pH and concentrations were investigated at constant ionic strength and constant NOM proxy concentrations in solution. Experimental results were described with NICA-Donnan model. Thallium complexation was compared to silver complexation using literature data and using the same NICA-Donnan formalism. Parameters for these two cations (Tl⁺ and Ag⁺) are reported in this article, for the first time. Results display low thallium complexation to the NOM proxy while silver competes with divalent cations for the NOM binding sites. Calculated speciation for dissolved thallium highlights the dominance of free thallium (Tl⁺) in solution whereas Tl-NOM complexes contribute roughly 15% to total Tl(I) species in river and lake type waters. Similar results are obtained for soil solutions, Tl-bound to NOM < 30% of total, from UK soils with different land use and geochemistry.     

Cadmium-induced toxicity reversal by zinc in Ceratophyllum demersum L. (a free floating aquatic macrophyte) together with exogenous supplements of amino- and organic acids

This paper analyzes the detoxification mechanisms adopted by amino- and organic acids to alleviate Cd toxicity. In addition, with our published data on Zn–Cd interactions, the influence of Zn (200 μM) supplements on the detoxification mechanisms of amino- and organic acids have also been studied. The experimental studies on metal uptake, lipid peroxidation levels, estimation of reduced and oxidized glutathione levels as well as γ-glutamylcysteine synthetase activity in amino acid supplemented Cd treatments indicated glutathione-mediated detoxification system, which was also enhanced by Zn (200 μM) supplements. However Zn did not aid in glutathione synthesis, but maintained the ratio of reduced and oxidized forms. The supplementation of organic acids to Cd treatments indicated detoxification through the mechanism of chelation. Zn seemed to be less influential on organic acids-mediated detoxification mechanism as compared to amino acid mediated detoxification system.     

复合电化学法处理含盐有机废水

研究了复合电化学法处理含盐，酚废水的可行性及处理效果，实验结果表明，在110－160℃，PH3-3.5，处理电压5V，电流密度6-9mA/cm^2,H2O2/苯酚（质量比）＞0．06时，200mg/L的苯酚溶液经处理后，酚去除率大于98％，CODCr去除率大于70％，该法电能消耗低，是一种适合于含盐有机废水处理的新方法。     

一种从有机废水中获取甲酸的方法

探讨了从环己醇/环己酮生产装置产生的酸性有机废水中获取甲酸的方法.在实验基础上,确定了共沸-分馏组合法回收甲酸的工艺过程、适宜挟带剂及工艺条件.采用共沸-分馏组合法处理该有机废水,可获取质量分数为80%以上的甲酸水溶液,甲酸回收率可达70%以上.同时,经本法处理后,该有机废水的COD由1.0×105～1.6×105 mg/L降至5× 102 mg/L以下,COD去除率达98%以上.     

Contribution of motor vehicle emissions to organic carbon and fine particle mass in Pittsburgh, Pennsylvania: Effects of varying source profiles and seasonal trends in ambient marker concentrations

We present estimates of the vehicular contribution to ambient organic carbon (OC) and fine particle mass (PM) in Pittsburgh, PA using the chemical mass balance (CMB) model and a large dataset of ambient molecular marker concentrations. Source profiles for CMB analysis are selected using a method of comparing the ambient ratios of marker species with published profiles for gasoline and diesel vehicle emissions. The ambient wintertime data cluster on a hopanes/EC ratio–ratio plot, and therefore can be explained by a large number of different source profile combinations. In contrast, the widely varying summer ambient ratios can be explained by a more limited number of source profile combinations. We present results for a number of different CMB scenarios, all of which perform well on the different statistical tests used to establish the quality of a CMB solution. The results illustrate how CMB estimates depend critically on the marker-to-OC and marker-to-PM ratios of the source profiles. The vehicular contribution in the winter is bounded between 13% and 20% of the ambient OC (274±56–416±72 ng-C m⁻³). However, variability in the diesel profiles creates uncertainty in the gasoline–diesel split. On an OC basis, one set of scenarios suggests gasoline dominance, while a second set indicates a more even split. On a PM basis, all solutions indicate a diesel-dominated split. The summer CMB solutions do not present a consistent picture given the seasonal shift and wide variation in the ambient hopanes-to-EC ratios relative to the source profiles. If one set of source profiles is applied to the entire dataset, gasoline vehicles dominate vehicular OC in the winter but diesel dominates in the summer. The seasonal pattern in the ambient hopanes-to-EC ratios may be caused by photochemical decay of hopanes in the summer or by seasonal changes in vehicle emission profiles.