Metal binding capacity of soft acid,organic‐rich waters

Organic carbon from one stream and two ponds in South Carolina was fractionated into five nominal molecular diameter fractions by ultrafiltration. The concentrations associated with and binding capacity for Ca, Cd, Cu and Pb were determined for each fraction. The distribution of organic carbon among ultrafilter fractions varied from water to water, with the largest percentage occurring in the smaller fractions. Calcium was associated with each of the fractions isolated from each of the three waters, indicating Ca is bound to organics in all fractions, however, more than 99% of the Ca which passed the smallest ultrafilter was removed by cationic exchange resin. Each fraction bound more Ca than Cd, Cu or Pb except in a few cases where Pb binding was greater. All of the organic fractions had their Ca++ binding sites saturated. Calcium was not an effective competitive ion against Cd, Cu or Pb for organic binding sites. The total Cu binding capacity was less than that of Ca or Pb but similar to that of Cd. Naturally occurring organics bound more Pb than Cd or Cu but less than Ca. Saturation of Cu binding sites was less than 20% in most ultrafilter fractions except that with a nominal molecular weight of between 10,000 and 300,000 where the percent of saturation was as much as 60%. Approximately 50% of the Cu was removed onto anionic exchange resin in two waters while more than 90% was removed from water with a high organic content. Percent saturation of Cd and Pb binding sites ranged from 0.091% to 5.4% and 0.059% to 1.5%, respectively. All ions tested effectively competed with Cd, Cu or Pb for some but not all binding sites, indicating that organic binding sites were heterogeneous. A generalized order of metal‐organic stabilities based on competition for binding sites is Al>Cd>Pb>Cu>Ni = Mg=Zn = Mn>Ca. Both Cd+2 and Al+3 effectively out competed Pb++ and Cd and Pb out competed Cu for most organic binding sites.     

Measuring dissolved organic carbon δ13C in freshwaters using total organic carbon cavity ring-down spectroscopy (TOC-CRDS)

This article reports the first application of coupled total organic carbon cavity ring-down spectroscopy (TOC-CRDS) for the analysis of the ??¹³C signature of dissolved organic carbon (DOC) in freshwater samples. DOC represents a major, dynamic component of the global carbon cycle. The export of DOC from soils into rivers and groundwaters may be highly climate sensitive, and much of this export may occur in ephemeral fluxes. Thus, a robust, simple and inexpensive method for the continuous determination of DOC concentration and quality is urgently needed. We detail recent advances made in the analysis of the ??¹³C signature of DOC using a TOC-CRDS system optimised for the analysis of DOC with natural abundances greater than 2.5?mg?L^?1 with no sample pre-concentration required and sample volumes of 40?mL. Precision between replicated samples was comparable to conventional analysis by gas-source isotope ratio mass spectrometry, yielding ??¹³C values with standard deviations of?±?0.5??? for DOC concentrations higher than 1.5?mg?L^?1. The utility of this technique for the analysis of DOC in samples with a broad range of compositions and concentrations (2.5?C25?mg?L^?1 DOC) is demonstrated. Since DOC ??¹³C can be measured continuously, ca. 45?min per measurement, this method enables the online monitoring of DOC in river water, water intakes and treated waters, allowing changes in DOC fluxes to be monitored in real time.     

Trends of chemical speciation profiles of anthropogenic volatile organic compounds emissions in China, 2005–2020

This study estimates the detailed chemical profiles of China＇s anthropogenic volatile organic com- pounds （VOCs） emissions for the period of 2005-2020. The chemical profiles of VOCs for seven activity sectors are calculated, based on which the Photochemical Ozone Creation Potential （POCP） of VOCs for these sectors is evaluated. At the national level, the VOCs species emitted in 2005 include alkanes, alkenes and alkynes, aromatic compounds, alcohols, ketones, aldehydes, esters, ethers and halocarbons, accounting for 26.4wt.%, 29.2wt.%, 21.3 wt.%, 4.7 wt.%, 5.4 wt.%, 1.7 wt.%, 2.1 wt.%, 0.7 wt. % and 2.2wt.% of total emissions, respectively. And during 2005-2020, their mass proportions would respec- tively grow or decrease by - 34.7%, -48.6%, 108.5%, 6.9%, -32.7%, 7.3%, 65.3%, 100.5%, and 55.4%. This change would bring about a 13% reduction of POCP for national VOCs emissions in the future. Thus, although the national VOCs emissions are expected to increase by 33% over the whole period, its ozone formation potential is estimated to rise only by 14%. Large discrepancies are found in VOCs speciation emissions among provinces. Compared to western provinces, the eastern provinces with a more developed economy would emit unsaturated hydrocarbons and benzene with lower mix ratios, and aromatic compounds except benzene, oxidized hydrocar- bons and halocarbons with higher mix ratios. Such differences lead to lower POCP of VOCs emitted in eastern provinces, and higher POCP of VOCs emitted in western provinces. However, due to the large VOCs emissions from Chinese eastern region, the ozone forma- tion potential of VOCs emission in eastern provinces would be much higher than those in western provinces by about 156%-235%.     

Quantitative structure‐activity relationships of hydrophobic organic chemicals 1

Quantitative structure‐activity relationships of hydrophobic organic chemicals were studied based on equations we established. Results showed that observed toxicity of hydrophobic organic chemicals were correlated to two physical‐chemical parameters: reaction equilibrium constant of target molecule‐organic chemical; octanol/water partition coefficient. Regression results showed that the molecular connectivity index of first‐order was an ideal parameter instead of the equilibrium constant. Good relationships between toxicity data and the two parameters were found for three aquatic organisms with a wide range of chemicals.     

Project tocoen. The fate of selected organic pollutants in the environment—iv. soil,earthworms and vegetation 1988

The samples of soils, earthworms and vegetation (needles, lichens, mosses) were collected for the realization of Project TOCOEN (Toxic Organic Compounds in the ENvironment). The samples were collected from three TOCOEN model areas in Czechoslovakia—one city and two rural areas. The samples were analyzed for polycyclic aromatic hydrocarbons (PAHs), chlorinated pesticides (C1‐PEST) and polychlorinated biphenyls (PCBs).     

Efficiency of Zn phytoextraction,biomass yield and formation of low-molecular-weight organic acids in S × rubens – a hydroponic experiment

The aim of the study was to estimate Zn phytoextraction and changes in biomass of S?×?rubens growing in modified Knop's solution with different levels of Zn addition (0.5, 1.0, 2.5 and 5.0?mM). Obtained results were correlated with secretion of selected low-molecular-weight organic acids (LMWOAs) in the rhizosphere, roots and leaves. An increase in Zn concentration in Knop's solution resulted in Zn accumulation in roots, shoots and leaves. The highest accumulation was observed for plants growing in 5?mM Zn, at concentration levels 4741.36?±?98.66, 1227.31?±?16.57 and 2241.65?±?34.90?mg?kg^?1 DW in roots, shoots and leaves, respectively. The bioaccumulation factor and the translocation factor for plants growing in 0.5, 1.0 and 2.5?mM Zn clearly indicate that this Salix taxon is an effective Zn accumulator. The general reduction of Salix biomass with an increase in Zn concentration in the solution was observed. In the rhizosphere, the total LMWOA concentration was almost 0.93?µmol?kg^?1 DM for control (Zn free) plants, while for 5.0?mM of Zn it was 4.9?µmol?kg^?1 DM. Increasing concentrations of acids were observed in roots (1.34 for the control and 5.57?µmol?kg^?1 DM for plants treated with 2.5?mM of Zn).     

Metal–organic frameworks for active food packaging. A review

Environmental Chemistry Letters - Food wastage is a major concern for sustainable health and agriculture. To reduce food waste, classical preservation techniques such as drying, pasteurization,...     

Aerogels and metal–organic frameworks for environmental remediation and energy production

Environmental pollution and climate change are requiring new methods to clean pollutants and produce sustainable energy. Aerogels and metal organic frameworks are emerging as advanced porous materials with higher functionality, high surface area, high porosity and flexible chemistry. Aerogels are dried gels prepared using the sol–gel procedure, whereas metal organic frameworks are networks of organic ligands and metal ions connected by coordination bonds. Applications of aerogels include the removal of heavy metals, CO₂ capture and reduction, photodegradation of pollutants, air cleanup and water splitting. This article reviews the synthesis and types of aerogels and metal organic frameworks, and the application to pollutant removal, energy production including hydrogen, methane reforming, CO₂ conversion and NOx removal.     

Detection of organic contamination in sediments by double-shoot pyrolysis–GC/MS

Pyrolysis coupled with gas chromatography–mass spectrometry (Py–GC–MS) has been previously proved to be an appropriate tool for the screening of organic contaminants in sediments. In this work the double-shoot pyrolysis technique has been applied to assess the contamination degree of sediment samples from Castro Marim Natural Park (South Portugal) and the Ria of Huelva (SW Spain). Compounds released both by thermodesorption at sub-pyrolysis temperatures (250–280°C) and subsequent pyrolysis (300–500°C) revealed information on the origin of the sedimentary organic matter and the occurrence of organic contamination in the sediments. Thermal desorption was found to be effective in releasing organic contaminants from spiked samples. However, in real sediments samples, higher pyrolysis temperatures (>300°C) were necessary to detect the occurrence of organic contaminants. Particularly polycyclic aromatic hydrocarbons (PAHs) and linear alkylbenzenes (LABs) were detected in variable proportions in most sediment samples.     

Modified ��-cyclodextrins as prospective agents for improving water solubility of organic pesticides

The drawback of some organic pesticides is their low water solubility. Cyclodextrins are used as agents for improving pesticides water solubility. However, the stabilization of the crystalline lattice can reduces to a large extent the solubility of cyclodextrins, especially β-cyclodextrin. Here, searching for the water soluble β-cyclodextrin derivatives, a set of new “host” compounds were prepared by the reaction of β-cyclodextrin with methyl epoxycinnamate. The reactants ratio was varied in to study the substitution degree of the obtained derivatives. The structure was determined by the ¹H-NMR and FT IR spectra. The average degree of substitution was determined by integration of the corresponding NMR signals and by elemental analysis. The solubility of four selected pesticides: dimethoate, simazine, linuron and thiram, in water with and without addition of the new modified β-cyclodextrin was measured by ultraviolet spectrophotometry. Our results showed that the modified β-cyclodextrins significantly improve solubility of pesticides.     

Spatio-temporal variations of fluorescence properties of dissolved organic matter along the River Têt (Pyrénées-Orientales,France)

Fluorescence excitation-emission matrices showed the spectral signature of dissolved organic matter (DOM) downstream in the River Têt at all seasons corresponding to humic substances with maximum fluorescence emission λem=420–460 nm for excitations of λex=340–360 nm and the occasional presence of tryptophan, tracer of anthropogenic pressure, spectroscopically identified by λex/λem=310/350 nm. A factorial discriminant analysis, performed using the parameters selected (λex/λem pairs of wavelength), succeeded in a better discrimination of seasons than stations, and clearly showed the presence of two fluorophores. Fluorophore 1, with two absorption bands: λex=260–320 nm and 330–390 nm for λem=440–500 nm, and Fluorophore 2, with one absorption band: λex=300–360 nm for λem=410 nm, which are attributed to humic acid (HA) and fulvic acid (FA), respectively. Variations of DOM relative contents downstream in the River Têt, according to seasons and stations, showed high amounts of DOM (pedogenic character) along the river in the humid period, with the highest value obtained in the mountain section. In contrast, in summer, the DOM contents were low (aquagenic character). Moreover, DOM presents a relatively constant composition with a percentage of FA ranging from 40% at the mountain station to 48% at the mouth river, whatever the season.     

Online electro-Fenton-mass spectrometry reveals 2,4′,5-trichlorobiphenyl oxidation products and binding to organic matter

Electrochemistry–mass spectrometry is used to simulate redox reactions in many research disciplines because this technique is fast and provides information on compound metabolites. However, the analysis of the degradation of refractory organic pollutants by reactive oxygen species is difficult to achieve by the electrochemistry step. Therefore, here we use online electro-Fenton-mass spectrometry to study for the first time the oxidation of 2,4′,5-trichlorobiphenyl [polychlorinated biphenyl (PCB) 31] by reactive oxygen species and the binding reactions of PCB degradation products with model substances of natural organic matter. The degradation products were identified by coupled Q Trap mass spectrometry. We observed a binding of a degradation product with γ-l-glutamyl-l-cysteinyl-glycine. We propose a transformation pathway. We conclude that online electro-Fenton-mass spectrometry is a promising technique to study the oxidation of refractory organic pollutants and further binding of degradation products with natural organic matter.     

Multi‐phase non‐steady state equilibrium model for evaluation of environmental fate of organic chemicals

A simple mathematical fate model, Multi‐Phase Non‐Steady State Equilibrium Model (MNSEM) is proposed to evaluate distribution, persistence, and concentrations of chemicals in a model environment consisting of air, water, soil and sediment phases. The model is applied to evaluation of environmental fate and concentration of trichloroethylene and 1,4‐dichlorobenzene under generic conditions representative of Japan.

Evaluated chemical concentrations in air are within a factor of 3 of average values in Japanese atmosphere, and evaluated concentrations in water, sediment, or fish are greater than an order of magnitude below detection limits in real environments, so that evaluated concentrations are in reasonable agreement with environmental measurement data in Japan.

Although MNSEM is not a model for site‐specific evaluation of environmental fate, results suggested that this model is an adequate method to aid in evaluation of fate of chemicals under generic environment conditions. Evaluated concentration‐profiles may be used to estimate average chemical exposure concentrations for humans and the environment.     

Effects of dissolved organic matter on the desorption of Cd in freeze–thaw treated Cd-contaminated soils

Lab-scale experiments were conducted to investigate the effects of dissolved organic matter (DOM) on the desorption of Cd in freeze–thaw treated Cd-contaminated soils. The results indicated that DOM significantly facilitated the desorption of Cd from freeze–thaw treated soils when comparing with that of non-frozen soils. Effects of DOM on the Cd desorption were highly dependent on the soil type and contamination concentration. The maximum desorption ratios of Cd by DOM generated from straw and sludge were 15.6% and 13.65%, respectively, in brown soils, and the maximum desorption ratios reached 14.7% and 9.3%, respectively, when using black soils through the same treatment. The higher the Cd contamination concentration in soils, the higher the ratio of Cd desorption by DOM. This was because of the integrated effects of the soil properties changed by the freeze–thaw treatment and the species transformation of Cd. The characteristics of DOM, such as its concentration and properties, had shown obvious impacts on the Cd desorption by DOM. The desorption was promoted with the increased DOM concentration and the hydrophilic fraction, and lowered pH and the low-molecular-weight of DOM.     

‘Aji gnui assonii’—a practice of organic hill farming among the Apatani tribe of Eastern Himalaya

Apatani, a hill tribe of Arunachal Pradesh, India, has been practising rice fish culture traditionally for many decades. Their practice, locally termed aji ngui assonii, is free from the use of agro-chemicals and additional input of supplementary feed for fish. They basically follow the traditional agronomic practices for rice even in rice-fish combination pertaining to field preparation and maintenance. Field preparation starts in April, occasionally continues up to late May, and rice seedlings are planted in May-June. The strains of common carp are stocked at fry stage (3–5 cm), after just ten days of planting the rice and reared in the field for about 4 months in total. Sometimes they harvest fish partially from the field after an interval of 1.5 months. With multiple harvesting, only 200–300 kg ha-' offish are produced in each harvest whereas with final harvesting the production rate is 500 kg ha-'. The dykes of rice fields are utilized for growing millet in June and are harvested during August-September. The system of such integrated farming is an organic practice, as well as sustainable in the sense that it is based solely on available natural resources in the ecosystem and also preserves the agro-biodiversity, enhancing multidimensional support to the tribal livelihood.     

Photosensitivity sources of dissolved organic matter from wastewater treatment plants and their mediation effect on 17α-ethinylestradiol photodegradation

● EE2 photodegradation behavior in the presence of four WWTPs’ DOM was explored. ● The ³DOM* played a major role in the EE2 photodegradation mediated by WWTPs’ DOM. ● The A²/O process DOM contained more aromatic and oxygen-containing substances. ● Possible photosensitivity sources of DOM in the A²/O process were proposed. Dissolved organic matter (DOM) from each treatment process of wastewater treatment plants (WWTPs) contains abundant photosensitive substances, which could significantly affect the photodegradation of 17α-ethinylestradiol (EE2). Nevertheless, information about EE2 photodegradation behavior mediated by DOM from diverse WWTPs and the photosensitivity sources of such DOM are inadequate. This study explored the photodegradation behavior of EE2 mediated by four typical WWTPs’ DOM solutions and investigated the photosensitivity sources of DOM in the anaerobic-anoxic-oxic (A²/O) process. The parallel factor analysis identified three varying fluorescing components of these DOM, tryptophan-like substances or protein-like substances, microbial humus-like substances, and humic-like components. The photodegradation rate constants of EE2 were positively associated with the humification degree of DOM (P < 0.05). The triplet state substances were responsible for the degradation of EE2. DOM extracted from the A²/O process, especially in the secondary treatment process had the fastest EE2 photodegradation rate compared to that of the other three processes. Four types of components (water-soluble organic matter (WSOM), extracellular polymeric substance, humic acid, and fulvic acid) were separated from the A²/O process DOM. WSOM had the highest promotion effect on EE2 photodegradation. Fulvic acid-like components and humic acid-like organic compounds in WSOM were speculated to be important photosensitivity substances that can generate triplet state substances. This research explored the physicochemical properties and photosensitive sources of DOM in WWTPs, and explained the fate of estrogens photodegradation in natural waters.     

Halogenated organic compounds (volatile and non volatile) as parameters for the evaluation of drinking water quality)†

Trihalomethanes are a well known parameter of water quality, but the determinations of the other volatile organochlorine compounds and of total organic halogen can give us more complete informations. Results are given about their use for ground waters and for treated surface waters. Ground waters may be polluted by halogenated solvents. The choice of an oxidizing agent has a great influence upon the quality of treated river water.     

热化学反应在ICP-AES中的应用——水中As,Sb,Bi,Te,Tl,Sn,In,Cd,Pb的ppb,ppt级测定

研究拟定了九种元素的ICP-AES分析方法.检出限在0.0004μg/ml—0.003μg/ml之间,利用自行研制的热化学反应炉电热蒸发装置,将水样蒸发浓缩,用载体吸附后烘干,再与反应剂混合后送入反应炉内发生定向热化学反应,用载气将分析元素的反应蒸气带入等离子体进行光谱方法分析.对主要的测定参量进得了试验,对基盐影响进行了研究,用拟定的方法对As,Cd,Pb三元素的水标准参考样进行了测定,分析结果与标准值相当一致.对不同含量的标准进行了多次回收测定,取得了比较满意的结果.此方法能满足水中痕量元素分析的需要。