Showing papers in "Environmental Science & Technology in 1986"

Water solubility enhancement of some organic pollutants and pesticides by dissolved humic and fulvic acids

Abstract: Water solubility enhancements by dissolved humic and fulvic acids from soil and aquatic origins and by synthetic organic polymers have been determined for selected organic pollutants and pesticides (p,p'-DDT,2,4,5,2',5'-PCB, 2,4,4'-PCB, 1,2,3,-trichlorobenzene, and lindane). Significant solubility enhancements of relatively water-insoluble solutes by dissolved organic matter (DOM) of soil and aquatic origins may be described in terms of a partition-like interaction of the solutes with the microscopic organic environment of the high-molecular-weight DOM species; the apparent solute solubilities increase linearly with DOM concentration and show no competitive effect between solutes. The K/sub dom/ values of solutes with soil-derived humic acid are approximately 4 times greater than with soil fulvic acid and 5-7 times greater than with aquatic humic and fulvic acids. The effectiveness of DOM in enhancing solute solubility appears to be largely controlled by the DOM molecular size and polarity. The relative inability of high-molecular-weight poly(acrylic acids) to enhance solute solubility is attributed to their high polarities and extended chain structures that do not permit the formation of a sizable intramolecular nonpolar environment. 41 references, 6 figures, 3 tables.

General purpose adsorption isotherms.

Abstract: The fitting of adsorption isotherm equations to experimental data is often an important aspect of data analysis If the Langmuir and Freundlich isotherms are used, then consideration must be given to the proper weighting of the observations Preferably nonlinear regression (nonlinear least squares) should be used since this enables these isotherms to be fitted directly and also enables other isotherms to be tested with little extra effort Isotherms described here which are likely to show a wide range of applicability include the Toth, modified Dubinin-Radushkevich, and multisite Langmuir isotherms These can also describe competitive adsorption (binary exchange) reactions and are well suited for heterogeneous exchangers such as soils and sediments Specific examples discussed are the adsorption of P and K by soils, Na-Cu exchange by montmorillonite, and Zn adsorption by ferrihydrite

Sorption kinetics of hydrophobic organic compounds to natural sediments and soils

Abstract: Sorption kinetics of hydrophobic organic chemicals to and from suspended sediment and soil particles is described by a radial diffusive penetration model modified by a retardation factor reflecting microscale partitioning of the sorbate between intraaggregate pore fluids and the solids making up the aggregate grains. In light of this and other sorption kinetics models, a closed-loop-stripping apparatus with a photoionization detector operating in-line was used to examine the effects of sorbate hydrophobicity, sorbent particle size, and system temperature on solid-solution exchange over times of seconds to days. The authors results indicate that a single effective diffusivity parameter, which is predictable from compound solution diffusivity, octanol-water partition coefficient, and sorbent organic content, density, and porosity, can be used to quantify the sorption kinetics.

Fluorescence quenching method for determining equilibrium constants for polycyclic aromatic hydrocarbons binding to dissolved humic materials

Abstract: rn A fluorescence quenching method has been developed for determining equilibrium constants for the association of pyrene, phenanthrene, and anthracene with dissolved humic and fulvic acids. The technique is based upon the observation that polycyclic aromatic hydrocarbon (PAH) fluorescence in aqueous solution is quenched upon association with humic material. Association constants are derived from the fractional decrease in fluorescence intensity as a function of added humic material with Stern-Volmer plots. This allows association constants to be measured without a separation. In addition, the technique involves a ratio measurement so the exact concentration of pollutant need not be determined. Stern-Volmer plots were linear for the three PAHs studied. Anthracene-humic association constants determined by the fluorescence quenching technique correlated reasonably well with values determined by a reverse-phase method. However, unlike the reverse-phase method the measured association constants do not depend on the concentration of dissolved organic matter.

Singlet oxygen in surface waters. 3. Photochemical formation and steady-state concentrations in various types of waters

Abstract: For prediction of the rate with which organic compounds are oxidized and photoproducts formed in the aquatic environment by the /sup 1/O/sub 2/ route, the steady-state concentrations of O/sub 2/ in various waters were determined by using furfuryl alcohol as a trapping agent. Under noon, summer sunlight (Switzerland) in lake, river, and wastewaters, surface concentrations were (0.3-3) x 10/sup -14/ M /sup 1/O/sub 2/ per mg of DOC/L. Separation of natural aquatic organic compounds by gel permeation chromatography resulted in fractions showing little correlation between /sup 1/O/sub 2/ production efficiency and molecular weight, indicating that large macromolecular structures are not a prerequisite for the sensitization of /sup 1/O/sub 2/ formation. 26 references, 8 figures, 3 tables.

Characteristics of atmospheric organic and elemental carbon particle concentrations in Los Angeles

Abstract: A fine particle air monitoring network was operated in the Los Angeles area during 1982. It was found that carbonaceous aerosols accounted for typically 40% of total fine particle mass loadings at most monitoring sites. The ratio of total carbon (TC) to elemental carbon (EC) in ambient samples and in primary source emissions was examined as an indicator of the extent of secondary organic aerosol formation. It was found that TC to EC ratios at all sites on average are no higher than recent estimates of the TC to EC ratio in primary source emissions. There is little evidence of the sustained summer peak in the ratio of TC to EC that one might expect if greatly enhanced secondary organics production occurs during the photochemical smog season. The TC to EC ratio does rise by the time that air masses reach the prevailing downwind edge of the air basin as would be expected if secondary organics are being formed during air parcel transport, but the extent of that increase is modest. These results suggest that primary particulate carbon emissions were the principal contributor to long-term average fine aerosol carbon concentrations in the Los Angeles area during 1982.

Limitations in the use of commercial humic acids in water and soil research.

Abstract: Seven samples of commercial humic acids, purchased from five different suppliers, were studied, and their characteristics were compared with humic and fulvic acids isolated from streams, soils, peat, leonardite, and a dopplerite sample. Cross-polarization and magic-angle spinning /sup 13/C NMR spectroscopy clearly shows pronounced differences between the commercial materials and all other samples. Elemental and infrared spectroscopic data do not show such clear-cut differences but can be used as supportive evidence, with the /sup 13/C NMR data, to substantiate the above distinctions. As a result of these differences and due to the general lack of information relating to the source, method of isolation, or other pretreatment of the commercial materials, these commercial products are not considered to be appropriate for use as analogues of true soil and water humic substances, in experiments designed to evaluate the nature and reactivity of humic substances in natural waters and soils.

Potential artifacts in the determination of metal partitioning in sediments by a sequential extraction procedure

Abstract: The partitioning of trace metals in sediments, as obtained with a sequential extraction procedure, may be affected by (i) the techniques used to preserve the sediments before analysis and (ii) the presence/absence of atmospheric oxygen during the extraction steps. No storage method tested completely preserved the initial chemical and physical characteristics of the sediments. Drying of the sediment (freeze-drying; oven-drying) should be avoided; acceptable preservation techniques include freezing or short-term wet storage (1-2/sup 0/C). Among the different metals (Cd, Co, Cr, Cu, Ni, Pb, Zn, Fe, and Mn), copper, iron, and zinc were particularly sensitive to sample pretreatment. For anoxic sediments, the maintenance of oxygen-free conditions during the extractions is of critical importance.

Influence of the nature of soil organics on the sorption of toluene and trichloroethylene

Abstract: Predictive relationships that are presently employed for estimating the soil-water partitioning of nonionic organic pollutants do not account for the variable nature of soil organic matter. The capacity of selected components of soil organic matter to sorb trichloroethylene (TCE) and toluene, two nonionic volatile organic pollutants commonly encountered in contaminated groundwaters, is examined here. Sorption coefficients were determined and correlated with selected physico-chemical characteristics of the sorbents. Results indicate that the components of soil organic matter had widely varying affinities for toluene and TCE that cannot be solely explained by their organic carbon content. Multivariate regression results show that use of a sorbent's oxygen content as well as its carbon content yields a more accurate prediction of the sorptive partitioning coefficient than relationships that rely solely on the sorbent's carbon content.

Selective recovery of gold and other metal ions from an algal biomass.

Abstract: The authors observed that the pH dependence of the binding of Au/sup 3 +/, Ag/sup +/, and Hg/sup 2 +/ to the algae Chlorella vulgaris is different than the binding of other metal ions. Between pH 5 and 7, a variety of metal ions bind strongly to the cell surface. Most of these algal-bound metal ions can be selectively desorbed by lowering the pH to 2; however, Au/sup 3 +/, Hg/sup 2 +/, and Ag/sup +/ are all bound strongly at pH 2. Addition of a strong ligand at different pHs is required to elute these ions from the algal surface. Algal-bound gold and mercury can be selectively eluted by using mercaptoethanol. An elution scheme is demonstrated for the binding and selective recovery of Cu/sup 2 +/, Zn/sup 2 +/, Au/sup 3 +/, and Hg/sup 2 +/ from an equimolar mixture. 20 references, 2 figures.

Molecular weight distribution, carboxylic acidity, and humic substances content of aquatic organic matter: implications for removal during water treatment.

Abstract: The characterization of dissolved aquatic organic matter present in several natural water sources as well as corresponding treated waters derived from several types of water treatment processes is presented. Important characteristics of the organic matter, including molecular weight distribution, carboxylic acidity, and humic substances content, appear to affect the removal of organic material although the results of this research do not permit one to accurately quantify source-related effects from process-related effects.

Biotransformations of selected alkylbenzenes and halogenated aliphatic hydrocarbons in methanogenic aquifer material: a microcosm study.

Abstract: Leachates from municipal landfills commonly contain a variety of organic contaminants of industrial origin. The behavior of these compound in anaerobic, and particularly in methanogenic, subsurface materials is poorly understood. The behavior of benzene, toluene, ethylbenzene, o-xylene, 1,1-dichloroethylene, trans-1,2-dichloroethylene, cis-1,2-dichloroethylene, trichloroethylene, and 1,2-dibromoethane was studied in authentic aquifer material known to support methanogenesis. These compounds are frequently found as contaminants in groundwater used for municipal water supplies. The disappearance of all compounds was observed with long lag times required before initiation of degradation of 1,1-dichloroethylene, trans-1,2-dichloroethylene, trichloroethylene, benzene, ethyl-benzene, and o-xylene. (/sup 14/C)Toluene degraded to CO/sub 2/. Vinyl chloride was found was a daughter product of 1,1-dichloroethylene, trans-1,2-dichloroethylene, and tri-chloroethylene. 1,2-Dichloroethylene was also observed as a degradation product of trichloroethylene. No daughter products were identified for the remaining compounds. 30 references, 3 tables.

Polybrominated dibenzofurans and dibenzo-p-dioxins: thermal reaction products of polybrominated diphenyl ether flame retardants.

Abstract: Thermolysis of three technical polybrominated diphenyl ether (PBDPE) flame, retardants in quartz minivials at 510-630/sup 0/C produced a range of potentially hazardous and toxic polybrominated dibenzofurans (PBDFs) and di-benzo-p-dioxins (PBDDs) at total yields of up to 10%. HRGC-MS analysis revealed the formation of various mono- to octabrominated species. EI mass spectra of PBDPEs, PBDFs, and PBDDs were found to be similar to those of the chlorinated analogues. The technical PBDPEs, consisting of a rather small number of components, lead to reasonably simple mixtures of reaction products with, often, one or two main PBDF and PBDD isomers. Except 2,3,7,8-tetrabromodibenzofuran, which was not among the main thermolysis products, isomer assignments were not possible due to the lack of authentic reference compounds. PBDPEs are of environmental concern; the formation of PBDFs and PBDDs is of additional concern. These adverse effects should be carefully evaluated against the possible merits of these products as flame retardants. 20 references, 2 figures, 4 tables.

Mathematical modeling of chemically reactive pollutants in indoor air.

Abstract: A general mathematical model is presented for predicting the concentrations of chemically reactive compounds in indoor air. The model accounts for the effects of ventilation, filtration, heterogeneous removal, direct emission, and photolytic and thermal chemical reactions. The model is applied to the induction of photochemically reactive pollutants into a museum gallery, and the predicted NO, NO_x-NO, and O_3 concentrations are compared to measured data. The model predicts substantial production of several species due to chemical reaction, including HNO_2, HNO_3, NO_3, and N_2O_5. Circumstances in which homogeneous chemistry may assume particular importance are identified and include buildings with glass walls, indoor combustion sources, and direct emission of olefins.

Drinking-water standards.

Abstract: This paper discussed the revising of the primary and secondary drinking-water regulations by EPA in accordance with the Safe Drinking Water Act. Since consideration of risk is playing an increasing role in setting environmental standards, questions were raised regarding the adequacy of human health protection afforded by some of the existing and proposed standards. 1 table.

Vapor-particle partitioning of semivolatile organic compounds: estimates from field collections.

Abstract: Pesticides, polychlorinated biphenyls (PCB), and other semivolatile organic compounds (SOC) exist in air as vapors and are associated with particulate matter. Factors influencing the vapor-to-particle distribution can be obtained from high-volume sampling experiments using a glass-fiber filter to collect particles and an adsorbent trap to collect vapors. Measurements of airborne organochlorine pesticides and PCB in four cities over a wide temperature range were used to estimate apparent partition coefficients A(TSP)/F, where A and F are the adsorbent- and filter-retained SOC concentrations (ng/m/sup 3/) and TSP in the total suspended particle concentration (..mu..g/m/sup 3/). A(TSP)/F were related to the average sampling temperature (T, kelvin) through log(A(TSAP)/F) = m/T + b. Fitted log(A(TSP)/F) at 20/sup 0/C were closely correlated with logp/sup 0//sub L/, the subcooled liquid vapor pressure. Heats of adsorption (..delta..H/sub A/), calculated from slopes m, were at most 2-4 kcal/mol greater than subcooled liquid heats of vaporization (..delta..H/sub VL/) and in most cases indistinguishable from ..delta..H/sub V,L/ at the 95% confidence level. 41 references, 3 figures, 5 tables.

Airborne dioxins and dibenzofurans: sources and fates

Abstract: Polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) were found in urban air particulates and Great Lakes sediments. In all samples, octachlorodibenzo-p-dioxin predominated. Combustion of municipal and chemical wastes was the most likely source of these compounds. When these data were compared with dioxins and dibenzofurans found in combustion sources, evidence was found that the most likely source of PCDD and PCDF to a western Lake Ontario site was pentachlorophenol production. Historical fluxes of dioxins and dibenzofurans to sediment cores from Lake Erie and Siskiwit Lake (Isle Royale) suggest that the incineration of chloro aromatics has been an important source of dioxins and dibenzofurans. 24 references, 6 figures, 1 table.

Influence of colloids on sediment-water partition coefficients of polychlorobiphenyl congeners in natural waters

Abstract: Measurements of sediment-water partitioning of polychlorobiphenyl (PCB) congeners in Lake Superior provide some of the first field evidence demonstrating the importance of colloids to the fates of highly hydrophobic organic pollutants Laboratory-derived correlations between sediment-water distribution coefficients and properties of both the contaminant (octanol-water partition coefficient) and the suspended solids (organic carbon content, concentration) do not accurately predict PCB speciation in Lake Superior This failure can be explained by the presence of colloidal matter with which contaminants may associate and the very low solids concentrations in oligotrophic surface waters A surprising consequence of such colloid associations is that the observed sediment-water distribution coefficients are independent of properties of highly hydrophobic compounds A three-phase model including nonfilterable microparticles and macromolecular organic matter shows that colloidal-associated contaminants may be the dominant species in most surface waters Colloidal associations are therefore likely to significantly impact the geochemistry of hydrophobic pollutants

Metal-Humate Interactions. 1. Discrete Ligand and Continuous Distribution Models

Abstract: In this paper the authors examine critically the theory underlying discrete and continuous multiligand models for metal-humate binding. The concepts and equations that unify the various models are presented, and a general solution to the fundamental integral equation for ion binding in a multiligand system is given. Particular attention is paid to the continuous distribution models (normal distribution, affinity spectrum, and continuous stability function) which are relatively new tools in the field of metal-humate complexation. It is shown that the lower half and extreme right of the Gaussian ligand distribution assumed in the normal distribution model never affect metal speciation measurably and hence are not knowable. It is also shown that an affinity spectrum does not correspond to an actual distribution of ligands; rather, each peak in the spectrum indicates the most probable stability constant controlling metal binding in a particular region of the experimental formation function. Application of the affinity spectrum model leads to a set of discrete ligands. A close examination of the continuous stability function model shows that it contains implicitly the same assumption as the affinity spectrum approach and thus leads also to discrete ligands.

Effects of nonreversibility, particle concentration, and ionic strength on heavy-metal sorption.

Abstract: The reversible component partition coefficient for nickel and cobalt sorbed to montmorillonite and quartz is shown to be a function of particle concentration. Resuspension and dilution experiments appear to exclude explanations that rely on nonseparated particles and/or complexing ligands associated with the particles. A particle interaction model is presented that assumes the existence of an additional desorption reaction that results from particle-particle interactions. The model is in conformity with the experimental results. The observed partition coefficient decrease with increasing ionic strength is a result of the decrease in the classical, low particle concentration limit, partition coefficient. The particle-particle interaction is independent of ionic strength. 41 references, 6 figures, 3 tables.

Accumulation of bis(tributyltin) oxide by the marine mussel Mytilus edulis.

Abstract: Marine mussels, primarily Mytilus edulis, accumulated bis(tributyltin) oxide (TBT) when it was either dissolved in water (0.5 ..mu..g L/sup -1/) or associated (absorbed or adsorbed) with phytoplankton Isochrysis galbana. Uptake occurred rapidly under both protocols but was more rapid and caused higher TBT burdens when accumulation occurred by ingestion of phytoplankton. TBT accumulated differentially in tissues. Highest burdens in viscera or gills were approx.4.5 ..mu..g of TBT (g of tissue)/sup -1/ following water exposure lasting 47 days and approx.5 ..mu..g of TBT (g of gill)/sup -1/ or (g of viscera tissue)/sup -1/ following 30 days of exposure to contaminated Isochrysis. This corresponds to a bioconcentration factor of approx.5000 from water but <2 from food (on a ..mu..g g/sup -1/ basis). Mantle or muscle tissue had TBT burdens one-half to one-third the level of viscera or gill tissue. Steady state between water and tissue was not observed. When TBT exposed mussels were returned to the field, t/sub 1/2/ for depuration was approx.14 days. Depuration rate constants estimated from uptake and release phases did not agree. This observation suggests differences in laboratory and field depuration processes by bivalve molluscs. Therefore, bioconcentration factor (BCF) measurements made in the laboratory may not accurately predictmore » those obtained from environmental exposures. Neither humic acids nor kaolin significantly reduced accumulation of TBT.« less

Model describing the rates of transfer processes of organic chemicals between atmosphere and water

Abstract: A comprehensive model is developed describing the rates of processes of organic chemical volatilization, absorption at the water surface, dissolution in rainfall, and wet and dry particle deposition, which in total comprise the dominant air-water exchange processes. Correlations are suggested for partitioning between air and airborne particles and for washout ratios as a function of the chemical's physical-chemical properties. It is suggested that chemicals with high Henry's law constants, which are subjected to volatilization, but have low vapor pressures and are thus subject to appreciable sorption to atmospheric particles, may cycle between water and air with intermittent periods of intense deposition followed by slower but prolonged volatilization. A steady-state but non-equilibrium condition may be achieved in which the water is supersaturated with respect to the air; i.e., the chemical potential or fugacity of the chemical in the water exceeds that in the air. These effects will be pronounced at low temperatures. 34 references, 1 figure, 4 tables.

On ranking chemicals for environmental hazard

Abstract: A formal approach is developed to rank chemicals for environmental hazard according to test results relevant to their fate and/or toxicity by using a vectorial approach for partial ordering. In this example, 34 chemicals have been ranked according to seven criteria related to their bioaccumulation and degradation characteristics. In addition, a smaller set of test compounds, namely, chlorobenzenes, have been also ranked according to their toxicity to fish, bacteria, and zooplankton and according to their environmental fate. The ranking is displayed by using Hasse diagrams which show that 2,4-dichlorobiphenyl, 2,4,6,2'-tetrachlorobiphenyl, pentachlorobenzene, and hexachlorobenzene are environmentally the most hazardous of the 34 chemicals on the basis of the seven criteria. By use of only five criteria, hexachlorobenzene is ranked the highest.

Comprehensive method for determination of aquatic butyltin and butylmethyltin species at ultratrace levels using simultaneous hydridization extraction with gas chromatography-flame photometric detection.

Abstract: An ultratrace method for the analysis of aquatic anthropogenic butyltin and mixed methylbutyltin species using simultaneous hydridization with sodium borohydride and extraction into dichloromethane is described The detection limits for a 100-mL sample are 7 ng of Sn/L for tetrabutyltin, 7 ng of Sn/L for tributyltin, 3 ng of Sn/L for dibutyltin, and 22 ng of Sn/L for monobutyltin Detection limits of approximately 1-2 ng of Sn/L for tri- and tetrabutyltin and less than 1 ng of Sn/L for dibutyltin species were achieved with 800-mL samples The presence of tetrabutyltin in harbor waters is reported 39 references, 9 figures, 2 tables

Tributyltin in seawater: speciation and octanol-water partition coefficient.

Abstract: Analysis of chloroform extracts of tributyltin (TBT) dissolved in seawater shows that the equilibrium mixture of speciation products is composed of tributyltin chloride (TBTCl), tributyltin hydroxide (TBTOH), the aquo complex (TBTOH/sub 2//sup +/) (as a function of pH), and a tributyltin carbonato species. The equilibrium distribution is influenced by (Cl/sup -/), dissolved CO/sub 2/, and pH and is easily displaced by variation within the environmental concentration range of these substances. Octanol-water partition coefficients (K/sub ow/) for tributyltin vary as a function of salinity. The lowest value, 5500, was measured in 25 per cent per thousand and increased in higher or lower salinities to a maximum of 7000 in deionized water. The K/sub ow/ values reported here are substantially higher than some previous reports in the literature but are in more reasonable agreement with published bioaccumulation measurements for tributyltin assuming partitioning processes are responsible. 24 references, 4 figures, 1 table.

Water treatment processes. III. Removing dissolved inorganic contaminants from water

Abstract: This article describes the physicochemical treatment processes typically used to remove the more common inorganic contaminants from water and wastewater. These are precipitation, coprecipitation, adsorption, ion exchange, membrane separations by reverse osmosis and electrodialysis, and combinations of these processes. The general criteria for process selection are discussed, and the processes and their typical applications are described.

Solubility properties in polymers and biological media. 7. An analysis of toxicant properties that influence inhibition of bioluminescence in Photobacterium phosphoreum (the Microtox test).

Abstract: Inhibition of bioluminescence in Photobacterium phosphoreum (the Microtox test) has been proposed as a cost-effective prescreening procedure to eliminate the relatively more innocuous chemicals from testing programs for toxicities of organic chemicals to fish. The biological response, as a function of toxicant properties, is given by log EC/sub 50/ (in ..mu..molL) = 7.61 - 4.11 anti V100 - 1.54 ..pi..* + 3.94..beta.. - 1.51..cap alpha../sub m/ n = 38, r = 0.987, SD = 0.28 where anti V is the solute molar volume and ..pi..*, ..beta.., and ..cap alpha../sub m/ are the solvatochromic parameters that measure dipolaritypolarizability, hydrogen-bond acceptor basicity, and hydrogen-bond donor acidity of the solute (toxicant). The above equation applies to compounds that act by a nonreactive toxicity mechanism, and it is suggested that for certain compounds, which are outliers relative to the above equation, reactive toxicity properties mask the effects of the nonreactive mechanism. The above equation is compared with a correlation of log EC/sub 50/ with octanolwater partition coefficients. 25 references, 2 figures, 2 tables.