The Henry's law coefficient of 2-nitrophenol over the temperature range 278-303 K

Although 2-nitrophenol has been identified as an important environmental chemical there is scarcity in the literature regarding the temperature dependence of its Henry's law coefficient, H. Here a bubble purge method was used to measure H for 2-nitrophenol over the temperature range 278-303 K. A novel approach in the data treatment allowed correction of the data for non-equilibrium partitioning in the apparatus to obtain the true equilibrium H value. The experimentally derived temperature-dependent expression for H of 2-nitrophenol is lnH (M atm(-1)) = (6290/T (K)) - 16.6. The standard enthalpy and entropy of gas-to-liquid transfer for 2-nitrophenol in aqueous solution are -52.3 +/- 8.1 kJ mol(-1) and -138 +/- 28 J mol(-1) K(-1), respectively. (Errors are 95% confidence intervals.)     

A review of Henry's law coefficients for chlorine-containing C1 and C2 hydrocarbons

Experimentally determined Henry's law coefficients of 18 chlorinated C(1) and C(2) hydrocarbons reported in the literature as a function of temperature and at the single temperatures 20 and 25 degrees C were compiled and converted to common units of concentration and pressure: K(H) (moldm(-3)atm(-1)). The individual values are plotted in the ln(K(H)) versus reciprocal absolute temperature coordinate frame, data not in harmony with others were deleted, and the resulting data sets treated by linear regression analysis to derive averaged parameters in the general equation ln(K(H))=A+B/T. The quality of the evaluation was further checked by comparison of values calculated from the resulting parameter values with averages obtained from the direct measurements at 20 degrees C. Good agreement was observed for 15 compounds, larger discrepancies arise only for chloroethane, 1,2-dichloroethane and hexachloroethane. In all three cases the data base is poor and needs to be improved. The results are used to derive heats of solution for the C(1) and C(2) chlorinated hydrocarbons in water, Gibbs energies of solution and standard Henry's law coefficients at 298.15K. Henry's law coefficients calculated from the ratio of solubility of the compound in water and the saturation vapor pressure of the pure compound reported by Sangster [Sangster, J.M., 2003. Henry's law constants for compounds stable in water. In: Fogg, P.G.T., Sangster, J.M. (Eds.), Chemicals in the Atmosphere - Solubility, Sources and Reactivity. Wiley, Chichester, West Sussex, England, pp. 255-397] provide good agreement with the experimental data in eight out of eleven cases treated.     

Temperature dependencies of Henry's law constants and octanol/water partition coefficients for key plant volatile monoterpenoids

To model the emission dynamics and changes in fractional composition of monoterpenoids from plant leaves, temperature dependencies of equilibrium coefficients must be known. Henry's law constants (H(pc), Pa m3 mol(-1) and octanol/water partition coefficients (K(OW), mol mol(-1)) were determined for 10 important plant monoterpenes at physiological temperature ranges (25-50 degrees C for H(pc) and 20-50 degrees C for K(OW)). A standard EPICS procedure was established to determine H(pc) and a shake flask method was used for the measurements of K(OW). The enthalpy of volatilization (deltaH(vol)) varied from 18.0 to 44.3 kJ mol(-1) among the monoterpenes, corresponding to a range of temperature-dependent increase in H(pc) between 1.3- and 1.8-fold per 10 degrees C rise in temperature. The enthalpy of water-octanol phase change varied from -11.0 to -23.8 kJ mol(-1), corresponding to a decrease of K(OW) between 1.15- and 1.32-fold per 10 degrees C increase in temperature. Correlations among physico-chemical characteristics of a wide range of monoterpenes were analyzed to seek the ways of derivation of H(pc) and K(OW) values from other monoterpene physico-chemical characteristics. H(pc) was strongly correlated with monoterpene saturated vapor pressure (P(v)), and for lipophilic monoterpenes, deltaH(vol) scaled positively with the enthalpy of vaporization that characterizes the temperature dependence of P(v) Thus, P(v) versus temperature relations may be employed to derive the temperature relations of H(pc) for these monoterpenes. These data collectively indicate that monoterpene differences in H(pc) and K(OW) temperature relations can importantly modify monoterpene emissions from and deposition on plant leaves.     

Temperature dependence of the infinite dilution activity coefficient and Henry's law constant of polycyclic aromatic hydrocarbons in water

The water solubility of 9,10-dihydroanthracene was experimentally determined between 278.12 and 313.17 K. Determinations were carried out by an experimental procedure developed in our laboratory, which is a modification of the dynamic coupled column liquid chromatographic technique. The uncertainty of the experimental determinations ranged from +/- 0.50% to +/- 3.10%. These data, as well as the water solubility data of other five polycyclic aromatic hydrocarbons (PAHs) previously studied, were used to calculate the temperature dependence of the infinite dilution activity coefficient of 9,10-dihydroanthracene, anthracene, pyrene, 9,10-dihydrophenanthrene, m-terphenyl, and guaiazulene in water. Molar excess enthalpies and entropies at infinite dilution, at 298.15 K, were also derived. The temperature dependence of the infinite dilution activity coefficients was used, together with literature values of the vapor pressures of supercooled liquid PAHs (p(B)(sc)), to estimate their Henry's law constants (HLC). Only HLC for anthracene, pyrene, and 9,10-dihydrophenanthrene were calculated, since no p(B)(sc) data were available in the literature for 9,10-dihydroanthracene, m-terphenyl, and guaiazulene. From the observed temperature dependence of the Henry's law constants the enthalpy and entropy of the phase change from the dissolved phase to the gas phase were also derived for anthracene, pyrene, and 9,10-dihydrophenanthrene.     

Kinetics and mechanism of nitrite oxidation by hypochlorous acid in the aqueous phase

The rate coefficient for the reaction of nitrite with hypochlorite and hypochlorous acid has been studied using spectrophotometric measurements. The reaction rate has been determined in a wide range of H(+) concentration (5< or =-log[H(+)]< or =11). The kinetics were carried out as a function of NO(2)(-), H(+) and total hypochlorite ([HOCl](total)=[HOCl]+[ClO(-)]+[ClNO(2)]) concentrations. The observed overall rate law is described by: -d[HClO](T)dt=[a[NO(2)(-)](2)+b[NO(2)(-)]][H(+)](2)c+d[H(+)]+e[NO(2)(-)][H(+)](2)[HOCl](total)At T=298 K and in Na(2)SO(4) at an ionic strength (I=1.00 M), we obtained using a nonlinear fitting procedure: a=(1.83+/-0.36)x10(7) s(-1), b=(1.14+/-0.23)x10(5) Ms(-1), c=(1.12+/-0.17)x10(-13) M, d=(1.43+/-0.29)x10(-6) M(2) and e=(1.41+/-0.28)x10(3) M where the errors represent 2sigma. According to the overall rate law, a/b=k(1)/k(3), b/e=k(3), c=K(w), d/c=K(a), d=K(a)K(w) and e=K(1)K(a). In Na(2)SO(4) at an ionic strength (I=1.00 M), the values of K(1) and K(a) are (1.1+/-0.1)x10(-4) and 1.28x10(7) M(-1), respectively. A mechanism is proposed for the NO(2)(-) oxidation which involves the reversible initial step: NO(2)(-)+HOCl left harpoon over right harpoon ClNO(2)+OH(-) (K(1)), while ClNO(2) undergoes the two parallel reactions: attack by NO(2)(-) (k(1)) and hydrolysis (k(3)). ClNO(2) and N(2)O(4) are proposed as important intermediates as they control the mechanism. The rate coefficients k(1) and k(3) have been determined at different ionic strengths in NaCl and Na(2)SO(4). The influence of the ionic strength and ionic environment has been studied in this work.     

Aqueous solubility, Henry's law constants and air/water partition coefficients of n-octane and two halogenated octanes

New data on the aqueous solubility of n-octane, 1-chlorooctane and 1-bromooctane are reported between 1 degree C and 45 degrees C. Henry's law constants, K(H), and air/water partition coefficients, K(AW), were calculated by associating the measured solubility values to vapor pressures taken from literature. The mole fraction aqueous solubility varies between (1.13-1.60)x10(-7) for n-octane with a minimum at approximately 23 degrees C, (3.99-5.07)x10(-7) for 1-chlorooctane increasing monotonically with temperature and (1.60-3.44)x10(-7) for 1-bromooctane with a minimum near 18 degrees C. The calculated air-water partition coefficients increase with temperature and are two orders of magnitude lower for the halogenated derivatives compared to octane. The precision of the results, taken as the average absolute deviations of the aqueous solubility, the Henry's law constants, or the air/water partition coefficients, from appropriate smoothing equations as a function of temperature is of 3% for n-octane and of 2% and 4% for 1-chlorooctane and 1-bromooctane, respectively. A new apparatus based on the dynamic saturation column method was used for the solubility measurements. Test measurements with n-octane indicated the capability of measuring solubilities between 10(-6) and 10(-10) in mole fraction, with an estimated accuracy better than +/-10%. A thorough thermodynamic analysis of converting measured data to air/water partition coefficients is presented.     

Salting-in and salting-out effects of ionic and neutral osmotica on limonene and linalool Henry's law constants and octanol/water partition coefficients

Foliar emission rates of plant-generated volatile monoterpenes depend on monoterpene partitioning between air, aqueous and lipid-phases in the leaves. While Henry's law constants (H pc, equilibrium gas/water partition coefficient) and octanol/water partition coefficients (K OW) for pure water have been previously used to simulate monoterpene emissions from the leaves, aqueous phase in plants is a complex solution of electrolytes and neutral osmotica. We studied the effects of dissociated compounds KCl and glycine and sugars glucose, sorbitol and sucrose with concentrations between 0 and 1M on H pc and K OW values for limonene and linalool. Linalool with ca. 1500-fold lower H(pc) (2.62 Pa m(3)mol(-1) for pure water at 30 degrees C) and ca. 30-fold lower K OW (955 mol mol(-1) for pure water at 25 degrees C) is the more hydrophilic compound of the two monoterpenes. H pc of both monoterpenes increased with increasing concentration of both ionic compounds and sorbitol, but decreased with increasing glucose and sucrose concentrations. The salting-out coefficients for H pc (kH) were ca. an order of magnitude larger for more hydrophilic compound linalool than for more hydrophobic limonene. For linalool, co-solutes modified H pc by 30-50% at the highest concentration (1M) tested. The effect of temperature on the salting-out coefficient of KCl was minor. As with H pc, K OW increased with increasing the concentration of KCl, glycine and sorbitol, and decreased with increasing glucose and sucrose concentrations. For limonene, co-solutes modified K OW by 20-50% at the highest concentration used. For linalool, the corresponding range was 10-35%. Salting-out coefficients for H pc and K OW were correlated, but the lipid-solubility was more strongly affected than aqueous solubility in the case of limonene. Overall, these data demonstrate physiologically important effects of co-solutes on H pc and K OW for hydrophilic monoterpenes and on K OW for hydrophobic monoterpenes that should be included in current emission models.     

Henry's law constant, octanol-air partition coefficient and supercooled liquid vapor pressure of carbazole as a function of temperature: application to gas/particle partitioning in the atmosphere

The Henry's law constant for carbazole was experimentally determined between 5 and 35 degrees C using a gas-stripping technique. The following equation was obtained for dimensionless Henry's law constant (H') versus temperature (T, K): ln H' = -3982(T,K)(-1) + 1.01. Temperature-dependent octanol-air partition coefficients (KOA) and supercooled liquid vapor pressures (PL,Pa) of carbazole were also determined using the GC retention time method. The temperature dependence of KOA and PL were explained by the following: log KOA = 4076/(T,K) - 5.65, log PL(Pa) = -3948(T,K)(- 1) + 11.48.The gas and particle-phase carbazole concentrations measured previously in Chicago, IL in 1995 was used for gas/particle partitioning modeling. Octanol based absorptive partitioning model consistently underpredicted the gas/particle partition coefficients (Kp) for all sampling periods. However, overall there was a good agreement between the measured Kp and soot-based model predictions.     

An analytical method to determine Henry's law constant for selected volatile organic compounds at concentrations and temperatures corresponding to tap water use

Henry's law constants (H) are needed to model human exposure to Volatile Organic Compounds (VOCs) in indoor air resulting from the use of tap water. This paper presents an experimental method to determine Hs for several common tap water pollutants at concentrations and temperatures used in household water. For 5 VOCs Henry's law constants were obtained simultaneously over the 25 degrees C to 45 degrees C temperature range, providing data on H beyond the currently available data (up to 35 degrees C). Henry's law constants were obtained as the ratio of equilibrium concentrations of VOCs in air and water, using simultaneous sampling from sealed bottles kept at constant temperatures. Air and water samples were concentrated by a purge-and-trap method, thermally desorbed from a Tenax trap, and analyzed with a gas chromatograph with an electron capture detector (GC-ECD). Experimental results agreed well with available literature data.     

Vapour pressures, aqueous solubilities, Henry's Law constants, and octanol/water partition coefficients of a series of mixed halogenated dimethyl bipyrroles

Basic physical-chemical properties of five bromine and chlorine containing mixed halogenated dimethyl bipyrroles (HDBPs) were determined using established methods. Subcooled liquid vapour pressures (P(o)(L,25)), aqueous solubilities (S(w,25)), and octanol/water partition coefficients (K(ow)) were determined using the gas chromatography-retention time, generator column, and slow-stirring methods, respectively. Henry's Law constants (H25) were estimated using experimentally-derived P(o)(L) and S(w,25) data. Values of all four properties were generally similar to those reported for other polyhalogenated aromatic compounds [P(o)(L,25) = (7.55-191) x 10(-6) Pa; S(w,25) = (1.0-1.9) x 10(-5) g/l; log K(ow) = 6.4-6.7; H25 = 0.0020-0.14 Pa m3/mol]. The effect of replacing a chlorine with a bromine atom significantly decreased P(o)(L,25) (log P(o)(L,25) = -0.4197 (# bromine atoms) - 2.643, p<0.01) and H25 (log H25 = -0.508 (# bromine atoms) + 0.394, p<0.02). There were no significant effects of bromine/chlorine substitution on S(w,25) or K(ow). A simple Level I equilibrium partitioning model predicted the environmental behaviour of HDBPs to be similar to a tetrabrominated diphenyl ether. Only slight differences in behaviour amongst HDBP congeners were predicted since substitution of a bromine for a chlorine (Cl/Br substitution) atom had less effect than H/Cl or H/Br substitution on P(o)(L,25), S(w,25), H25, and K(ow).     

Desorption kinetics for selected PCB congeners from river sediments

Desorption of PCBs from sediment can significantly affect the ultimate fate and effects of PCBs in aquatic systems. Using a gas purging technique to strip soluble and sorbed polychlorinated biphenyls (PCBs) from solutions and sediment suspensions, Henry's law constants, approach to equilibrium, and desorption rate constants for four PCB congeners were measured. Henry's law constants were on the order of 10⁻⁴ m³ atm mole⁻¹. Desorption rate constants measured for a predominantly kaolinitic, low-organic carbon sediment were on the order of 0.03–0.1 days⁻¹. In contrast, desorption rate constants measured for a sediment composed of montmorillonite with a 3% organic carbon content were on the order of 0.009–0.04 days⁻¹. Desorption data suggest that equilibration times for PCBs with low chlorine content are on the order of six weeks, and months to years for PCBs with a significantly higher chlorine content.     

Physicochemical properties of selected polybrominated diphenyl ethers and extension of the UNIFAC model to brominated aromatic compounds

The aqueous solubilities (S(w)) at various temperatures from 283 K to 308 K and 1-octanol/water partition coefficients (K(ow)) for four polybrominated diphenyl ethers (PBDEs: 4,4'-dibromodiphenyl ether (BDE-15), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2',4,4',5-pentabromodiphenyl ether (BDE-99), and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153)) were measured by the generator column method. The S(w) and K(ow) data revealed the effect of bromine substitution and basic structure on S(w) and K(ow). To estimate the infinite dilution activity coefficients (gamma(i)(w,infinity)) of the PBDEs in water from the S(w) data, enthalpies of fusion and melting points for those compounds were measured with a differential scanning calorimeter. Henry's Law constants (H(w)) of the PBDEs were derived from the determined gamma(i)(w,infinity) and literature vapor pressure data. Some physicochemical characteristics of PBDEs were also suggested by comparing the present property data with that of polychlorinated dibenzo-p-dioxins, brominated phenols and brominated benzenes in past studies. Furthermore, in order to represent different phase equilibria including solubility and partition equilibrium for other brominated aromatic compounds using the UNIFAC model, a pair of UNIFAC group interaction parameters between the bromine and water group were determined from the S(w) and K(ow) data of PBDEs and brominated benzenes. The ability of the determined parameters to represent both properties of brominated aromatics was evaluated.     

Temperature dependence of Henry's law constants of metolachlor and diazinon

A dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube has been used to determine experimentally the Henry's law constants (HLC) of two pesticides: metolachlor and diazinon. The measurements were conducted over the temperature range 283-301 K. At 293 K, HLCs values are (42.6+/-2.8) x 10(3) (in units of M atm(-1)) for metolachlor and (3.0+/-0.3)x10(3) for diazinon. The obtained data were used to derive the following Arrhenius expressions: HLC=(3.0+/-0.4) x 10(-11) exp((10,200+/-1,000)/T) for metolachlor and (7.2+/-0.5) x 10(-15) exp((11,900+/-700)/T) for diazinon. At a cumulus cloud temperature of 283 K, the fractions of metolachlor and diazinon in the atmospheric aqueous phase are about 57% and 11% respectively. In order to evaluate the impact of a cloud on the atmospheric chemistry of both studied pesticides, we compare also their atmospheric lifetimes under clear sky (tau(gas)), and cloudy conditions (tau(multiphase)). The calculated multiphase lifetimes (in units of hours) are significantly lower than those in gas phase at a cumulus temperature of 283 K (in parentheses): metolachlor, 0.4 (2.9); diazinon, 1.9 (5.0).     

Kinetic assessment of the potassium ferrate(VI) oxidation of antibacterial drug sulfamethoxazole

Sulfamethoxazole (SMX), a worldwide-applied antibacterial drug, was recently found in surface waters and in secondary wastewater effluents, which may result in ecotoxical effects in the environment. Herein, removal of SMX by environmentally-friendly oxidant, potassium ferrate(VI) (K(2)FeO(4)), is sought by studying the kinetics of the reaction between Fe(VI) and SMX as a function of pH (6.93-9.50) and temperature (15-45 degrees C). The rate law for the oxidation of SMX by Fe(VI) is first-order with respect to each reactant. The observed second-order rate constant decreased non-linearly from 1.33+/-0.08 x 10(3) M(-1)s(-1) to 1.33+/-0.10 x 10(0) M(-1)s(-1) with an increase of pH from 7.00 to 9.50. This is related to protonation of Fe(VI) (HFeO(4)(-) <==> H(+) + FeO(4)(2-); pK(a,HFeO(4)) = 7.23) and sulfamethoxazole (SH <==> H(+) + S(-); pK(a,SH)=5.7). The estimated rate constants were k(11)(HFeO(4)(-) + SH) = 3.0 x 10(4) M(-1)s(-1), k(12)(HFeO(4)(-) + S(-)) = 1.7 x 10(2) M(-1)s(-1), and k(13) (FeO(4)(2-) + SH) = 1.2 x 10(0) M(-1)s(-1). The energy of activation at pH 7.0 was found to be 1.86+/-0.04 kJ mol(-1). If excess potassium ferrate(VI) concentration (10 microM) is used than the SMX in water, the half-life of the reaction using a rate constant obtained in our study would be approximately 2 min at pH 7. The reaction rates are pH dependent; thus, so are the half-lives of the reactions. The results suggest that K(2)FeO(4) has the potential to serve as an oxidative treatment chemical for removing SMX in water.     

Oxidation of MCPA and 2,4-D by UV radiation, ozone, and the combinations UV/H2O2 and O3/H2O2

The phenoxyalkyl acid derivative herbicides MCPA (4-chloro 2-methylphenoxyacetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) were oxidized in ultrapure water by means of a monochromatic UV irradiation and by ozone, as well as by the combinations UV/H2O2 and O3/H2O2. In the direct photolysis of MCPA, the quantum yield at 20 degrees C was directly evaluated and a value of 0.150 mol Eins(-1) was obtained in the pH range 5-9, while a lower value of 0.41 x 10(-2) mol Eins(-1) was determined at pH=3. Similarly, for 2,4-D a value of 0.81 x 10(-2) mol Eins(-1) was deduced, independent of the pH of work. The influence of the additional presence of hydrogen peroxide was established in the combined process UV/H2O2, and the specific contribution of the radical pathway to the global photo-degradation was evaluated. The oxidation by ozone and by the combination O3/H2O2 was also studied, with the determination of the rate constants for the reactions of both herbicides with ozone and hydroxyl radicals at 20 degrees C. These rate constants for the direct reactions with ozone were 47.7 and 21.9 M(-1) s(-1) for MCPA and 2,4-D respectively, while the found values for the rate constants corresponding to the radical reactions were 6.6 x 10(9) and 5.1 x 10(9) M(-1) s(-1).     

Henry's law constants for hexachlorobenzene, p,p'-DDE and components of technical chlordane and estimates of gas exchange for Lake Ontario

The Henry's law constants (HLC) for trans- and cis-chlordane (TC, CC), trans-nonachlor (TN), hexachlorobenzene (HCB) and p,p'-DDE were determined by the gas-stripping method over a temperature range of 5-35 degrees C. The HLC variation versus temperature (K) was described by logH=m/T+b. Parameters of this equation were (with standard deviations) TC: m=-1524+/-158, b=6.58+/-0.54; CC: m=-1786+/-209, b=7.42+/-0.71; TN m=-2068+/-284, b=8.44+/-0.97; HCB: m=-3013+/-174, b=11.60+/-0.59 and p,p'-DDE: m=-2043+/-240, b=8.37+/-0.82. The HLCs (Pa m3 mol(-1)) at 25 degrees C (298.15 K) were: TC=29; CC=27; TN=32; p,p'-DDE=33 and HCB=35. These HLCs values were used to calculate fugacity ratios from paired air and water data from Lake Ontario, July 1998. The resulting fugacity ratios predict that volatilization was occurring for all compounds during that month.     

Determination of Henry's law constant for elemental mercury

The assessment of the global mercury cycle involves estimations of the evasion of mercury form oceanic waters. In such estimations Henry's law constant is often used. In this study the Henry's law constant for elemental mercury has been re-determined in MQ water and artificial sea water. Moreover, for the first time it has been determined for 1.5M sodium chloride (NaCl) solution which is of relevance for modeling of atmospheric waters at coastal locations. For all solutions, experiments has been conducted at five different temperatures between 278 and 308K, using a novel technique, for mercury, based on direct measurements of the portioning of mercury between the aqueous and gaseous phase. Elemental mercury was extracted from the water column and the logarithm of the mass of extracted mercury was plotted against time. A dimensionless Henry's law constant, defined as: [Formula: see text] was obtained from the slope of the curve. Almost no difference was observed in the values comparing the Milli-Q water and artificial sea water, however for the 1.5M NaCl solution a salting-out effect was seen, i.e. the solubility of mercury in the water phase decreased. The decreased solubility will generate an increase in the value of Henry's law constant.     

A comparative study of the effects of chloride, sulfate and nitrate ions on the rates of decomposition of H2O2 and organic compounds by Fe(II)/H2O2 and Fe(III)/H2O2

The effects of chloride, nitrate, perchlorate and sulfate ions on the rates of the decomposition of hydrogen peroxide and the oxidation of organic compounds by the Fenton's process have been investigated. Experiments were conducted in a batch reactor, in the dark at pH < or = 3.0 and at 25 degrees C. Data obtained from Fe(II)/H2O2 experiments with [Fe(II)]0/[H2O2]0 > or = 2 mol mol(-1), showed that the rates of reaction between Fe(II) and H2O2 followed the order SO4(2-) > ClO4(-) = NO3- = Cl-. For the Fe(III)/H2O2 process, identical rates were obtained in the presence of nitrate and perchlorate, whereas the presence of sulfate or chloride markedly decreased the rates of decomposition of H2O2 by Fe(III) and the rates of oxidation of atrazine ([atrazine]0 = 0.83 microM), 4-nitrophenol ([4-NP]0 = 1 mM) and acetic acid ([acetic acid]0 = 2 mM). These inhibitory effects have been attributed to a decrease of the rate of generation of hydroxyl radicals resulting from the formation of Fe(III) complexes and the formation of less reactive (SO4(*-)) or much less reactive (Cl2(*-)) inorganic radicals.     

Lead sorption in calcareous soils

The sorption of lead by three soils that differed in texture and calcium carbonate content was studied at three different temperatures. Lead sorption was found to conform to both Freundlich and Langmuir isotherms. Soil adsorption maxima were derived from the reciprocal of the slope obtained by a least-squares fit of Langmuir plots for each soil. The highest adsorption capacity was exhibited by CaCO(3)-rich soil (773.55 mmol Pb kg(-1)). Raising the temperature from 298 K to 308 and 318 K increased the sorption capacity of all of the soils.