Zev Gerstl

Estimation of organic chemical sorption by soils

Abstract Sorption data for > 400 compounds were collected and analyzed. Sorption coefficients on an organic carbon basis ( K oc ) were found to be log-normally distributed. Correlations between log K oc and log aqueous solubility ( S ), log K ow (octanol-water partition coefficient) and molecular connectivity (MC) indices were calculated and their predictive ability determined with a set of test data not included in the original data set. It was found that the equations (log K oc vs.either log S or log K ow ) for individual chemical groups were preferred over the general equation for all chemicals but that a group correction term ( F c ) added to the total equation gave similar results. The use of MC indices alone were inadequate for predicting sorption values with the exception of a few homologous groups.

Suitability of dye–clay complexes for removal of non-ionic organic compounds from aqueous solutions

Aqueous sorption of phenol, atrazine and naphthalene was measured on complexes formed from Na-montmorillonite (Fischer bentonite) and the organic cationic dyes crystal violet and rhodamine-B. Sorption isotherms were found to be non-linear. This agrees well with the rigid nature of the dye-clay organic coverage, which provides a finite surface for adsorption. High values of organic carbon-normalized distribution coefficients reached 20,000-25,000 for atrazine on rhodamine-B-montmorillonite, 7000 for atrazine on crystal violet-montmorillonite, and 1500 for phenol on crystal violet-montmorillonite. As such, dye-clays may significantly extend the variety of organoclay sorbents that effectively reduce aqueous concentrations of non-ionic organic compounds.

Sorption of organic substances by soils and sediments

Abstract The solubility, octanol/water partition coefficient (KOW) and adsorption on soils and lake sediments of several chemicals were determined. Correlations between adsorption (on an organic matter basis) and either solubility or KOW enabled estimates of adsorption to within an order of magnitude. Systematic differences in adsorption between the soils and lake sediments were observed. The implications of these differences are discussed.

Soil pollution by petroleum products. III: Kerosene stability in soil columns as affected by volatilization

Abstract The stability of kerosene in soils as affected by volatization was determined in a laboratory column experiment by following the losses in the total concentration and the change in composition of the residuals in a dune sand, a loamy sand, and a silty loam soil during a 50-day period. Seven major compounds ranging between C 9 and C 15 were selected from a large variety of hydrocarbons forming kerosene and their presence in the remaining petroleum product was determined. The change in composition of kerosene during the experimental period was determined by gas chromatography and related to the seven major compounds selected. The experimental conditions — air-dairy soil and no subsequent addition of water—excluded both biodegradative and leaching. losses. The losses of kerosene in air-dried soil columns during the 50-day experimental period and the changes in the composition of the remaining residues due to volatilization are reported. The volatilization of all the components determined was greater from the dune sand and loamy sand soils than from the silty loam soil. It was assumed that the reason for this behavior was that the dune sand and the loamy sand soils contain a greater proportion of large pores (>4.5 μ m) than the silty loam soil, even though the total porosity of the loamy sand and the silty loam is similar. In all the soils in the experiment, the components with a high carbon number formed the main fraction of the kerosene residues after 50 days of incubation.

Fractionation of the organic matter in soils and sediments and their contribution to the sorption of pesticides

Abstract The organic matter of several soils and sediments was extracted by a gross fractionation procedure designed to dissolve specific classes of organic compounds. The sorption of napropamide, a nonionic herbicide, was measured on the original and extracted soils. It was found that soils contained a higher percentage of cellulose and hemicellulose materials whereas the lipid‐like fraction was greater in the sediments. Sorption of the test chemical was greater in the sediments, even on an organic carbon basis, than in the soils. Removal of specific fractions slightly affected the Koc of the sediments but not of the soils while acid extraction resulted in large increases in sorption by both soils and sediments; this effect was only partially reversible upon readjusting the pH.

The fate of terbuthylazine in test microcosms

The fate of 14C-labeled terbuthylazine in several soils from Israel was determined in a microcosm, designed to gather effluent and to trap volatile organic compounds and CO2. The soils studied included a heavy clay vertisol, a loess soil which has received organic amendments periodically over the last 31 years, and a control loess soil from adjacent unamended plots. No [14C]CO2 was produced in any of the soils, thus indicating that mineralization of the terbuthylazine did not occur. The cumulative volatilization of terbuthylazine and its metabolites from the loess soil after 67 days was 4.2% of the amount applied, while only 1.8% volatilized from the amended soil. This difference is attributed to greater sorption of the herbicide in the amended soil. In the vertisol, 5.4% of the amount applied was volatilized. Over 90% of the volatilized material was parent terbuthylazine. A total of 0.2–1.7% of the applied herbicide was leached from the loess soils by the 137 mm of water applied over the course of the experiment. The breakthrough of 14C activity from the non-amended soil was greater and more rapid than from the amended soil. Breakthrough from the vertisol systems was later than from the loess soils. Metabolites of terbuthylazine comprised the bulk of the activity leached from the columns. In the vertisol, terbuthylazine did not leach below 2 cm, whereas, in the loess soils the herbicide was leached to a depth of 5–6 cm. Although the downward movement of parent terbuthylazine was limited in the three soils studied, incomplete mineralization of the parent compound resulted in the formation of metabolites which were much more mobile in the soil column. As such, these metabolites may pose a serious threat to ground water quality if similar behavior is exhibited under actual field conditions.

Stability of parathion on attapulgite as affected by structural and hydration changes

The structure and hydration status of attapulgite clay after heating at elevated temperatures and the stability of parathion on these clays was studied. Using infrared spectroscopy and scanning electron microscopy it was found that the bound water was lost in two steps, at 250° and 450° with the first step being largely reversible. At 650°C the structure began to dissolve releasing significant amounts of Mg, and a decrease in aggregate porosity was noted. At 850°C an amorphous phase was formed bearing little resemblance to the original attapulgite. Parathion was stable on all of the preheated clays when kept at 25°C for 190 days. The reactions of parathion on the preheated clays was studied at 110°C Hydrolysis of parathion was found to be minimal. Isomerization was the main reaction occurring on the Ca-attapulgite, whereas on an organo-clay no isomerization was observed. A mechanism for the isomerization reaction is proposed which entails a distortion of the phosphate moiety of the pesticide by the oxygen of the ligand water resulting in the conformational changes necessary for the isomerization to take place. On the organo-clay such a conformation was not possible; hence no isomerization occurred.РезюмеИсследовались структура и состояние гидратации аттапулгитовой глины после нагревания при повышенных температурах, а также стабилность паратиона на этих глинах. Путем инфракрасной спектроскопии и электронного сканирующего микроскопа было обнаружено, что связанная вода освбождалась в двух этапах, при температурах 250°С и 450°С, причем первый этап был преимущественно реверсивный. При 650°С структура начинала растворяться, освобождая значительное количество магния, а также наблюдалось уменьшение пористости аггрегатов. При 850°С формировалась аморфная фаза, которая только в небольшой степени напоминала исходный аттапульгит. Паратион был стабильный на всех предварительно нагретых глинах, если они содержались при температуре 25°С в течение 190 дней. Реакции паратиона на нагретых глинах были исследованы при температуре 110°С. Гидролиз паратиона был минимальный. Изомеризация являлясь главной реакцей для Са-аттапульгита, в то время, как она не наблюдалась для органоглины. Для реакции изомеризации предложен механизм, который определяет искажение фосфатовой половины пестицида кислородом аддендовой воды, результатом чего является изменение формы необходимые для изомеризации. Для органо-глины такая форма невозможна, и в этом случае изомеризация не происходит. [Е.С.]ResümeeEs wurde der Struktur- und Hydratationszustand von Attapulgit-Ton nach dem Erhitzen auf erhöhte Temperaturen sowie die Stabilität von Parathion an diesen Tonen untersucht. Die Untersuchungen mit Infrarotspektroskopie und Rasterelektronenmikroskopie zeigten, daß das gebundene Wasser in zwei Schritten, bei 250°C und 450°C abgegeben wurde, wobei der erste Schritt in hohem Maße reversibel war. Bei 650°C begann die Struktur sich zu veräindern, indem sie beträchtliche Mengen an Magnesium vedor. Weiters wurde eine Abnahme der Aggregatporosität festgestellt. Bei 850°C wurde eine amorphe Substanz gebildet, die sehr wenig Ähnlichkeit mit dem ursprünglichen Attapulgit aufwies. Parathion war an allen vorerhitzten Tonen bei einer Temperatur von 25°C über 190 Tage stabil. Die Reaktion von Parathion an vorerhitzten Tonen wurde bei 110°C untersucht. Es zeigte sich, daß die Hydrolyse von Parathion minimal ist. Die wichtigste Reaktion, die bei Ca-Attapulgit festgestellt wurde, war eine Isomerisierung, während an einem Organo-Ton keine Isomerisierung beobachtet wurde. Es wird ein Mechanismus für die Isomerisierungsreaktion vorgeschlagen, der eine Deformation des Phosphatrestes des Pestizides dutch den Sauerstoff des ligandenwassers nach sich zieht, wodurch sich die Anderungen der Konformation ergeben, die für die Isomerisierung notwendig sind. An dem Organo-Ton war eine derartige Konformation nicht möglich, weshalb keine Isomerisierung auftrat. [U.W.]RésuméOn a étudié l’étata de la structure et d’hydration d’argile attapulgite après échauffement à de hautes temperatures, et la stabilité de parathion sur ces argiles. En utilisant la spectroscopie infra-rouge et la microscopie balaynte électronique on a trouvé que l’eau liée est perdue en deux étapes, à 250° et 450°C la première étape étant réversible. A 650°C la stucture a commencé à se dissoudre, relâchant des quantités significatives de Mg, et un amoindrissement de la porosité de l’aggrégat a été remarqué. A 850°C une phase amorphe a été formée, ressemblant peu à l’attapulgite d’origine. Le parathion êtait stable sur toutes les argiles pré-échauffées lorsqu’elles étalent gardées à 25° pendant 190 jours. Les réactions de parathion sur les argiles pré-échauffées ont été étudites à 110°. On a trouvé que l’hydrolise du parathion était minime. L’isomérisation était la réaction principale se passant sur l’attapulgite-Ca, alors que sur l’argile organique, aucune isomérisation n’a été observée. On propose un mécanisme pour la réaction d’isomérisation, mécanisme qui comprend la distortion de la moitié phosphate du pesticide par l’oxygène de l’eau liante, résultant en les changements conformationnels nácessaires pour que l’isomérsation se passe. Sur les argiles organiques, une telle conformation n’était pus possible; par conséquent, aucune isomérisation ne s’est passée. [D.J.]

On the mechanism of field‐scale solute transport: Insights from numerical simulations and field observations

Field-scale transport of conservative and reactive solutes through a deep vadose zone was analyzed by means of two different model processes for the local description of the transport. The first is the advection-dispersion equation (ADE) model, and the second is the mobile-immobile (MIM) model. The analyses were performed by means of three-dimensional (3-D), numerical simulations of flow and transport considering realistic features of the flow system, pertinent to a turf field irrigated with treated sewage effluents (TSE). Simulated water content and concentration profiles were compared with available measurements of their counterparts. Results of the analyses suggest that the behavior of both solutes in the deep vadose zone of the Glil Yam site is better quantified by the MIM model than by the ADE model. Reconstruction of the shape of the measured solute concentration profiles using the MIM model required relatively small mass transfer coefficient, γ, and relatively large volume fraction of the immobile water θim. This implies that for an initially nonzero solute concentration profile, as compared with the MIM model, the ADE model may significantly overestimate the rate at which solutes are loaded in the groundwater. On the contrary, for an initially zero solute concentration profile, as compared with the MIM model, the ADE model may significantly underestimate solute velocities and early arrival times to the water table. These findings stem from the combination of relatively small γ and relatively large θim taken into account in the MIM model. In the first case, this combination forces a considerable portion of the solute mass to reside in the immobile region of the water-filled pore space, while the opposite is true in the second case.

Mineral induced mechanochemical degradation: the imazaquin case.

The potential role of mechanochemical processes in enhancing degradation of imazaquin by soil components is demonstrated. The investigated components include montmorillonite saturated with Na(+), Ca(2+), Cu(2+)and Al(3+), Agsorb (a commercial clay mix), birnessite and hematite. The mechanical force applied was manual grinding of mixtures of imazaquin and the minerals, using mortar and pestle. The degradation rates of imazaquin in these mixtures were examined as a function of the following parameters: time of grinding, herbicide load (3.9, 8.9, 16.7 and 26.6 mg imazaquin per g mineral), temperature (10, 25, 40 and 70 degrees C), acidic/basic conditions, and dry or wet grinding. Dry grinding of imazaquin for 5 min with Al-montmorillonite or with hematite resulted in 56% and 71% degradation of the imazaquin, respectively. Wet grinding slightly reduced the degradation rate with hematite and entirely cancelled the enhancing effect of grinding with Al-montmorillonite. Wet grinding in the presence of the transition metals: Ni(2+), Cu(2+), Fe(3+) added as chlorides was carried out. Addition of Cu(2+) to Na-montmorillonite loaded with imazaquin was the most effective treatment in degrading imazaquin (more than 90% of the imazaquin degraded after 5 min of grinding). In this treatment, Cu-montmorillonite formation during the grinding process was confirmed by XRD and accordingly, grinding with Cu-montmorillonite gave similar degradation values. LC-MS analysis revealed that the mechanochemical transformation of imazaquin resulted in the formation of a dimer and several breakdown products. The reported results demonstrate once again that mechanochemical procedures offer a remediation avenue applicable to soils polluted with organic contaminants.

Impact of biosolids and wastewater effluent application to agricultural land on corticosterone content in lettuce plants

We studied corticosterone occurrence in lettuce plants grown on three biosolids amended soils under irrigation with either tap water or secondary wastewater effluent. Corticosterone was examined as it has possible implications for human health. It is a major glucocorticoid, and as such has an effect on regulation of metabolism, immune functions and stress response. The plants were grown in 220-L lysimeters packed with 3 soils which represent a wide range of physicochemical properties. Lettuce was grown in cycles (two in summer and two in winter) during 3 years, and in every spring season the sludges were re-applied. Corticosterone was quantified using ELISA and LCMS, and was found in the biosolids, tap water, wastewater effluent and lettuce plants. The respective ranges of concentrations were: 11-92 ng g(-1), 0.5-1.6 ng L(-1), 4.2-4.7 ng L(-1); and 1-900 ng g(-1) dry weight. A positive relationship was found between corticosterone concentrations in winter-grown lettuces and the plants fresh weight. The corticosterone content of the plants did not correspond with either the type of irrigation water or the biosolids type and rate of application or the soil properties.