Organics in the water column of Llake Pontchartrain

A study was conducted to quantitatively screen the Inner Harbor Navigation Canal of Lake Pontchartrain for the presence of EPA priority pollutants and any other pollutants detected in significant concentration. Water column samples were collected at different depths and on the flood and ebb tides. Compounds identified include aliphatic and aromatic hydrocarbons, phthlates, phenols, alcohols, amines, pesticides, herbicides, aldehydes, quinolines, fatty acids, carboxylic acids. These compounds were detected at the parts-per-trillion level. The concentrations of the individual organics detected on the flood and ebb tides were not significantly different. The data derived from samples taken at two different depths suggest that the distribution of organics in the water column was homogeneous.     

Mechanism-based quantitative structure-activity relationships for the inhibition of substituted phenols on germination rate of Cucumis sativus

Comparative inhibition activity (GC50) of 42 structurally diverse substituted phenols on seed germination rate of Cucumis sativus was investigated. Quantitative structure-activity relationships (QSARs) were developed by using hydrophobicity (1-octanol/water partition coefficient, logKow) and electrophilicity (the energy of the lowest unoccupied molecule orbital, Eluma) for the toxicity of phenols according to their modes of toxic action. Most phenols elicited their response via a polar narcotic mechanism and a highly significant log Kow-based model was obtained (GC50 = 0.92 log Kow + 1.99, r2 0.84, n = 29). The inclusion of E(lumo) greatly improved the predictive power of the polar narcotic QSAR (GC50 = 0.88 log Kow - 0.30E(lumo) + 1.99, r2 = 0.93, n = 29). pKa proved to be an insignificant influencing factor in this study. Poor correlation with hydrophobicity and strong correlation with electrophilicity were observed for the nine bio-reactive chemicals. Their elevated toxicity was considerably underestimated by the polar narcotic logKow-dependent QSAR. The nine chemicals consist of selected nitro-substituted phenols, hydroquinone, catechol and 2-aminophenol. Their excess toxic potency could be explained by their molecular structure involving in vivo reaction with bio-macromolecules. Strong dissociation of carboxyl group of the four benzoic acid derivatives greatly decreased their observed toxicity. In an effort to model all chemicals including polar narcotics and bio-reactive chemicals, a response-surface analysis with the toxicity, logKow and E(lumo) was performed. This resulted in a highly predictive two-parameter QSAR for most of the chemicals (GC50 = 0. 70 logKow - 0.66E(lumo) + 2.17, r2 = 0.89, n = 36). Catechol and 2,4-dinitrophenol proved to be outliers of this model and their much high toxicity was explained.     

光催化氧化降解垃圾渗滤液中溶解性有机物

研究了UV-TiO2光催化氧化降解垃圾渗滤液过程中溶解性有机物(DOM)的变化特征。结果表明:在适宜条件下,UV-TiO2光催化氧化降解垃圾渗滤液的色度、COD和DOC的去除率分别可达97%、72%和60%;紫外光谱分析说明渗滤液DOM中包括多种含有共轭双键、羰基的大分子有机物及多环芳香类化合物,不同光催化处理液中DOM具有基本一致的结构单元和官能团;红外光谱分析说明渗滤液DOM中含有大量包括羟基、羧基、氨基和苯环的芳香族化合物,在光催化处理液中这几种官能团都能被有效降解;GC/MS分析结果表明,渗滤液DOM中含有72种有机污染物,醇类、羧酸和酮类分别为25、14和12种;在光催化72 h处理液中,有机物减少为44种;酯类和醇类较多,分别为12种和16种;酮类8种,羧酸没有检出。     

A computationally feasible quantum chemical model for 13C NMR chemical shifts of PCB-derived carboxylic acids

Two quantum chemical models have been derived for the prediction of 13C NMR chemical shifts of novel PCB acids obtained from PCBs by catalytic carbonylation. 13C isotropic shielding constants were calculated employing the GIAO (gauge-independent atomic orbital) method with density functional theory (DFT). The best results were obtained by cluster calculations, which took the solvent effects into account properly. In this approach, a solvent molecule (acetone) was attached by a hydrogen bond to every hydrogen atom present in a PCB acid, and the geometry of the molecular cluster was optimized employing the AM1 method. For 158 chemical shifts, the cross-validated standard error was 2.8 ppm and the cross-validated correlation coefficient was 0.94.     

Buffering processes in a boreal dissolved organic carbon-rich stream during experimental acidification

The role of organic acids on surface water acidity as well as their buffering during anthropogenic acidification and subsequent recovery was studied in a field experiment on a total organic carbon (TOC)-rich stream draining the Svartberget catchment in northern Sweden. H(2)SO(4) was added to the stream to increase SO(4)(2-) concentration by 90 microeq l(-1) for 30 h. About 60% of the added H(+) was buffered by protonation of organic acids, another 20% was buffered by base cations released from the surface of the stream channel and only ca. 20% of the added acid remained unbuffered. TOC concentrations (27 mg l(-1)), and site density of carboxylic groups--8.6 microeq (mg TOC)(-1)--remained stable during the experiment. Two models of organic acid dissociation (a triprotic model and a monoprotic pH-dependent pKa model) were fitted to the experimental results. These models explained the observed variations in organic anions, but the model parameters were quite different from those reported by studies in Northern America and Central Europe. This experiment had substantially more buffering effect of TOC between pH 4.4 and 5.3, which is an environmentally important pH range.     

Investigating the chemical nature of humic-like substances (HULIS) in North American atmospheric aerosols by liquid chromatography tandem mass spectrometry

The high-molecular weight water-soluble organic compounds present in atmospheric aerosols underwent functional-group characterization using liquid chromatography tandem mass spectrometry (LC-MS/MS), with a focus on understanding the chemical structure and origins of humic-like substances (HULIS) in the atmosphere. Aerosol samples were obtained from several locations in North America at times when primary sources contributing to organic aerosol were well-characterized: Riverside, CA, Fresno, CA, urban and peripheral Mexico City, Atlanta, GA, and Bondville, IL. Chemical analysis targeted identification and quantification of functional groups, such as aliphatic, aromatic, and bulk carboxylic acids, organosulfates, and carbohydrate-like substances that comprise species with molecular weights (MW) 200–600 amu. Measured high-MW functional groups were compared to modeled primary sources with the purpose of identifying associations between aerosol sources, high-MW aerosol species, and HULIS. Mobile source emissions were linked to high-molecular weight carboxylic acids, especially aromatic acids, biomass burning was associated with carboxylic acids and carbohydrate-like substances, and secondary organic aerosol (SOA) correlated well with the total amount of HULIS measured, whereas organosulfates showed no correlation with aerosol sources and exhibited unique spatial trends. These results suggested the importance of motor vehicles, biomass burning, and SOA as important sources of precursors to HULIS. Structural characteristics of atmospheric HULIS were compared to terrestrial humic and fulvic acids and revealed striking similarities in chemical structure, with the exception of organosulfates which were unique to atmospheric HULIS.     

Comparison of structural features of water-soluble organic matter from atmospheric aerosols with those of aquatic humic substances

Elemental analysis, Fourier transform infrared coupled to attenuated total reflectance (FTIR-ATR) and solid-state cross polarization with magic angle spinning-¹³C-nuclear magnetic resonance (CPMAS ¹³C NMR) spectroscopies were used to compare the chemical features of water-soluble organic compounds (WSOC) from atmospheric aerosols with those of aquatic humic and fulvic acids. The influence of different meteorological conditions on the structural composition of aerosol WSOC was also evaluated. Prior to the structural characterisation, the WSOC samples were separated into hydrophobic acids and hydrophilic acids fractions by using a XAD-8/XAD-4 isolation procedure. Results showed that WSOC hydrophobic acids are mostly aliphatic (40–62% of total NMR peak area), followed by oxygenated alkyls (15–21%) and carboxylic acid (5.4–13.4%) functional groups. Moreover, the aromatic content of aerosol WSOC samples collected between autumn and winter seasons is higher (∼18–19%) than that of samples collected during warmer periods (∼6–10%). The presence of aromatic signals typical of lignin-derived structures in samples collected during low-temperature conditions highlights the major contribution of wood burning processes in domestic fireplaces into the bulk chemical properties of WSOC from aerosols. According to our investigations, aerosol WSOC hydrophobic acids and aquatic fulvic and humic acids hold similar carbon functional groups; however, they differ in terms of the relative carbon distribution. Elemental analysis indicates that H and N contents of WSOC hydrophobic acids samples surpass those of aquatic fulvic and humic acids. In general, the obtained results suggest that WSOC hydrophobic acids have a higher aliphatic character and a lower degree of oxidation than those of standard fulvic and humic acids. The study here reported suggests that aquatic fulvic and humic acids may not be good models for WSOC from airborne particulate matter.     

Characterization of odor released during handling of swine slurry: Part II. Effect of production type,storage and physicochemical characteristics of the slurry

The quality of rural life can be affected by offensive odors released from animal buildings and storage units. The objectives of this study were to compare the concentrations of odor and odorants above different types of stirred swine slurry to analyze the relationships between concentrations of odor (and odorants) and physicochemical characteristics of the slurry (i.e. pH, temperature, dry matter, volatile solids, and concentration of 22 chemical compounds); and to propose predictive models for the odor concentration (OC) based on these physicochemical characteristics (solely and in combination with concentrations of specific odorants in the air above the slurries). The study comprised data on concentrations of odor and odorants in the air above slurry samples (fresh and/or stored) collected from production units with farrowing sows, finishing swines, or weaning pigs at eight swine operations (N = 48). OC measured in the air above stirred swine slurry samples were not significantly different among production types or storage times. The physicochemical characteristics of the slurries were not useful for predicting OC or concentrations of hydrogen sulfide (or organic sulfides) above the slurry, but were related to concentrations of other emitted gases such as phenols and indoles (r² = 0.65–0.79, p <0.05), ammonia (r² = 0.86, p < 0.05) and carboxylic acids (r² = 0.23–0.59, p <0.05). There was good precision of predictive models of OC based on selected slurry characteristics (i.e. pH, dry matter, nitrogen content, sulfur content or concentrations of individual aromatic compounds and carboxylic acids) together with concentrations of specific odorants in the air (e.g. hydrogen sulfide) (r² between 0.70 and 0.92). This study suggests that predictive models could be useful for evaluating odor nuisance potentials of swine slurry during handling.     

Solubility of organic acids in various methanol and salt concentrations: the implication on organic acid sorption in a cosolvent system

The well-known cosolvency-induced sorption model is not applicable to predict the sorption of carboxylic acids in cosolvent system. To investigate the phenomenon, sorption and solubility of chlorinated phenols (2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP)) and carboxylic acids (benzoic acid and 2,4-dichlorophenoxyacetic acid (2,4-D)) were measured in soil-methanol mixture with various ionic strengths. The sorption (K_m) of chlorinated phenols was explained by a cosolvency-induced sorption model; the inverse log-linear relationship between the K_m and methanol volume fraction (f_c). However, the K_m of carboxylic acids increased with increasing f_c. This discrepancy was attributed to the effect of the carboxylic moiety. To explain the effect, solubility was measured for benzoic acid and 2,4,6-TCP from various liquid conditions. For both solutes, the cosolvency power (σ) increased with CaCl₂ concentrations and the salting constant (K^s) became smaller as f_c increased. However, the σ value at a given salt concentration and the K^s value at a given f_c were greater for 2,4,6-TCP than for benzoic acid, both of which were due to the greater hydrophobicity of the former. Overall, the solubility profiles of the both solutes on combination of f_c and CaCl₂ concentration evidenced no specific role of the carboxylic moiety. Therefore, it can be reasonably concluded that the positive relationship between K_m and f_c for carboxylic organic acid can be attributed to the modification of the activity coefficient occurred in the solid phase, which cannot be traceable by cosolvency-based model.     

Effects of organic ligands on fractionation of rare earth elements (REEs) in hydroponic plants: an application to the determination of binding capacities by humic acid for modeling

Previous studies have revealed the fractionation processes of rare earth elements (REEs) in hydroponic plants, with a heavy REE (HREE, the elements from Gd to Lu) enrichment in leaves. In this study, effects on the HREE enrichment in soybean leaves with additions of carboxylic acids (acetate, malate, citrate, NTA, EDTA and DTPA) and two soil humic acids (HAs) were investigated. REE speciation in carboxylic acid and HA solutions was simulated using Visual MINTEQ and Model V, respectively. The results showed that the effects caused by carboxylic acids were strongly dependent on the differences between their binding strengths for light REEs (LREEs, the elements from La to Eu) and those for HREEs. A good correlation existed between these effects and the changes of free REE ions in solutions. This relationship was also observed for the HA treatments, provided that the intrinsic equilibrium constants of REEs for cation–proton exchange with HA (i.e., pK_MHA) in Model V were estimated using a free-energy relationship with the stability constants for REE complexation with lactic acid. It is suggested that this set of pK_MHA values is more suitable for use in Model V for the simulation of REE complexation with HA.     

Synthesis of environmentally relevant fluorinated surfactants--a review

In the past years there has been a growing interest in fluorinated persistent organic pollutants such as perfluorooctanesulfonic acid, perfluorooctanesulfonamides, perfluorinated carboxylic acids and fluorotelomer alcohols. Although these compounds have probably been present in the environment for many decades, we are only now beginning to realize that these environmental contaminants may have serious environmental and health effects. This article gives a state-of-the-art review of synthetic approaches that have been employed for the synthesis of these environmentally relevant fluorinated compounds. Perfluorooctanesulfonic acid derivatives, in particular, pose a problem because only a few perfluorooctanesulfonic acid derivatives are available from commercial sources--a fact that limits the ability of researchers worldwide to further study these compounds. Because of the limited literature available, this article also describes synthetic approaches for shorter chain homologues or perfluoroether analogues that can potentially be applied for the synthesis of perfluorooctanesulfonic acid derivatives. The preparation of typical starting materials for the synthesis of perfluorooctanesulfonic acid derivatives such as the perfluoroalkanesulfonyl fluorides and chlorides will be discussed. Subsequently, their conversion into relevant perfluoroalkane sulfonate salts (R(F)SO3M), sulfonamides (R(F)SO2NH2), N-alkyl sulfonamides (R(F)SO2NHR, R = alkyl), N,N-dialkyl sulfonamides (R(F)SO2NR2, R = alkyl), sulfonamidoethanol (R(F)SO2NRCH2CH2OH, R = -H, -CH3 or -C2H5) and sulfonamidoacetates (R(F)SO2NRCH2CO2H, R = -H, -CH3 or -C2H5) will be described. Many perfluorinated carboxylic acids and fluorotelomer alcohols are available from commercial sources. The review of the synthesis of these two classes of fluorinated compounds includes a review of their industrial synthesis and the synthesis of relevant degradation products.     

Estrogenicity and acute toxicity of selected anilines using a recombinant yeast assay

Suspected estrogen modulators include industrial organic chemicals (i.e., xenoestrogens), and have been shown to consist of alkylphenols, bisphenols, biphenylols, and some hydroxy-substituted polycyclic aromatic hydrocarbons. The most prominent structural feature identified to be important for estrogenic activity is a polar group capable of donating hydrogen bonds (i.e., hydroxyl) on an aromatic system. The present study was undertaken to explore the estrogenic activity and acute toxicity of chemicals containing a weaker hydrogen bond donor group on aromatic systems, i.e., the amino substituent. There is a great deal of chemical similarity between aromatic amines (anilines) and aromatic alcohols (phenols). The chemicals chosen for the current study contained an amino-substituted benzene ring with hydrophobic constituents varying in size and shape. Thus, 37 substituted aromatic amines were assayed for estrogenic activity EC50 and acute toxicity LC50 using the Saccharomyces cerevisiae recombinant yeast assay. While the EC50 of 17-beta-estradiol occurs at the 10(-10) range, the aniline with the greatest activity had an EC50 of 10(-6) M. Thus, anilines, in general, are capable only of very weak estrogenic activity in this assay. A comparison of estrogenic potency between the present group of anilines and a set of previously tested analogous phenols indicated that anilines are consistently less estrogenic than phenols. A comparison of hazard indices (EC50/LC50) of these chemicals revealed that, for the vast majority of anilines, the EC50 and LC50 were in the same order of magnitude. More specifically, estrogenic activity of para-substituted alkylanilines increases with alkyl group size up to 5 carbons in length, after which the acute toxicity of the larger alkyl-substituents precluded the ability of the compound to induce the estrogenic response.     

Computer-based QSARs for predicting mixture toxicity of benzene and its derivatives

During the past decades, the Quantitative structure-activity relationships (QSARs) have been proven to be reliable tools when little or no empirical data are available in medicinal chemistry, biochemistry, toxicology, and environmental sciences. However, only few studies that quantitatively predict mixtures toxicity have been reported. In this study, the QASR models for the binary mixtures toxicity of 12 benzene and its derivatives, including eight non-polar-narcotic compounds and four polar narcotic compounds were developed, without reference to exact toxicity mechanisms of single compounds. All parameters for the QSAR studies were defined on the basis of quantum mechanical calculations and these parameters were selected by the stepwise procedure. The results of this study provided a simple means of predicting the binary mixtures toxicity from the chemical structure.     

Quantitative structure-activity relationships for the inhibition toxicity to root elongation of Cucumis sativus of selected phenols and interspecies correlation with Tetrahymena pyriformis

The comparative toxicities of selected phenols to higher plants Cucumis sativus were measured and the negative logarithm molar concentration of the root elongation median inhibition (IRC50) were derived. Quantitative structure-activity relationships (QSARs) were developed to explore the toxicity influencing factors and for predictive purpose. The toxicity data, fell into two classes: polar narcosis and bio-reactive. For polar narcotic phenols, a highly significant two-parameter QSAR based on 1-octanol/water partition coefficient (logKow) and energy of the lowest unoccupied orbital (E(lumo)) was derived (IRC50 = 0.77 log Kow - 0.39E(lumo) + 2.36 n = 22 r2 = 0.89). The five bio-reactive chemicals proved to show elevated toxicity due to their typical substructure involved diverse reactive mechanisms. In an effort to model all chemicals, a robust multiple-variable QSAR combining logKow, E(lumo) and Qmax, the most negative net atomic charge, was developed (IRC50 = 0.65 logKow - 0.72E(lumo) + 0.23Qmax + 2.81 n = 27 r2 = 0.94), indicating that hydrophobicity, electrophilicity and hydrogen bond interaction contribute mainly to the phytotoxicity. The toxicological data was compared with Tetrahymena pyriformis 2-d population growth inhibition toxicity (IGC50) and excellent interspecies correlations were observed both for the polar narcotics and for five reactive chemicals (for polar narcotics: IRC50 = 0.95IGC50 + 1.07 n = 16 r2 = 0.89; for bio-reactive chemicals: IRC50 = 0.98IGC50 + 2.19 n = 5 r2 = 0.97; and for all: IRC50 = 0.93IGC50 + 1.63 n = 21 r2 = 0.87). This suggested that T pyriformis toxicity could serve as a surrogate of C. sativus toxicity for phenols and interspecies correlation also could be established for reactive chemicals.     

Characterization of odor released during handling of swine slurry: Part I. Relationship between odorants and perceived odor concentrations

Odor emission from livestock production systems is a major nuisance in many rural areas. This study aimed at determining the major airborne chemical compounds responsible for the unpleasant odor perceived in swine facilities during slurry handling, and at proposing predictive models of odor concentration (OC) based on the concentrations of specific odorants in the air. A multivariate data analysis strategy involving principal components analysis and multiple linear regressions was implemented to analyze the relationships between concentration of 35 gases (measured by GC/MS or gas detection tubes), and the overall OC perceived by sensory analysis. The study compiled data on the concentration of odor and odorants, measured in the headspace of 24 unstored and stored slurry samples collected from three different types of production units on 8 commercial swine farms. Among all the measured constituents, OC was found to have the highest correlation with the sulfur containing compounds (i.e. hydrogen sulfide, dimethylsulfide, dimethyldisulfide, dimethyltrisulfide). The concentration of hydrogen sulfide accounted for 68% of the variation in OC above the stirred slurry samples. The highest concentrations of volatile organic compounds were observed for phenols and indoles, which made a significant contribution to the overall OC when the slurry was fresh. The contribution of ammonia to the OC was only significant in the absence of hydrogen sulfide. The precision of predictive models of OC based on the concentration of specific odorants in the air was satisfactory (R² between 0.66 and 0.89). Hence, this study suggests that monitoring of specific odor compounds released from agitated swine slurry can be used to predict the concentration of odor perceived close to the source (e.g. at storage units), allowing the assessment of odor nuisance potentials.     

Variation of low molecular weight organic acids in precipitation and cloudwater at high elevation in South China

To investigate the sources and chemical behaviors of carboxylic acids in Southern China, precipitation and corresponding cloudwater samples were collected in an acid rain-prone area of Mount Heng. The carboxylic acid levels in the samples were measured, and the concentration patterns were evaluated with respect to temporal and seasonal variations. Formic and acetic acids were predominant among the carboxylic acids identified for both precipitation and cloudwater. Most of the organic acids in the precipitation had a clear seasonal pattern, reaching higher levels during the warm season; these higher levels were attributed to the stronger source strength of biogenic emissions during this season. The cloud–fog samples did not display a similar trend. A distinctive diurnal pattern in carboxylic acids was only observed in the precipitation samples during the warm season. In cloud–fog, the ratio of formic to acetic acid differed considerably with time, with these values varying little in the precipitation samples. This result indicates that the organic acids in precipitation originate consistently from primary sources throughout the entire period, while those in cloud are mainly associated with direct emissions in the earlier stage and with secondary sources in the later period.