Impacts of Soil Organic Matter and Temperature on Sorption of Acetazolamide on Four Soils

Batch sorptions of acetazolamide (AZ) were conducted using four soils from China. Sorption of AZ was found to be impacted by OC, clay content, and soil pH, with higher k_d values for soils with higher clay content. The k_d values of SOM-removed soils are much lower than those of bulk soils. Sorption data were well fitted with a Freundlich model (r² > 0.99). Chelating with the metal ions on the surfaces of soil particles was probably involved. With pH increase, the electrostatic attraction between anionic AZ and positively charged soil surface may increase. The sorption capacity decreased when the temperature increased from 20 to 40°C, and the calculated thermodynamics parameters of ΔG₀, ΔH₀, and ΔS₀ indicated that the sorption was a non-spontaneous, physisorption, and exothermic process. Sorption coefficients (k_d) for the compound in soil were low (ranging from 0.42 to 1.19 L·kg^?1) and indicated that low level sorption of AZ with appreciable risk of ground water contamination.     

Effects of dissolved organic matter from sewage sludge on the atrazine sorption by soils

The effects of dissolved organic matter (DOM), water soluble organic matter derived from sewage sludge, on the sorption of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-trazine) by soils were studied using a batch equilibrium technique. Six paddy soils, chosen so as to have different organic carbon contents, were experimented in this investigation. Atrazine sorption isotherms on soils were described by the linear equation, and the distribution coefficients without DOM (K_d) or with DOM (K_d ^*) were obtained. Generally, the values of K_d ^*/K_d initially increased and decreased thereafter with increasing DOM concentrations of 0–60 mg DOC · L^?1 in soil-solution system form. Critical concentrations of DOM (DOM_np) were obtained where the value of K_d ^* was equal to K_d. The presence of DOM with concentrations lower than DOM_np promoted atrazine sorption on soils (K_d ^* > K_d), whereas the presence of DOM with concentrations higher than DOM_np tended to inhibit atrazine sorption (K_d ^* < K_d). Interestingly, DOM_np for tested soils was negatively correlated to the soil organic carbon content, and the maximum of K_d ^*/K_d (i.e.K _max) correlated positively with the maximum of DOM sorption on soil (X_max). Further investigations showed that the presence of hydrophobic fraction of DOM evidently promoted the atrazine sorption on soils, whereas the presence of hydrophilic DOM fraction obviously tended to inhibit the atrazine sorption. Interactions of soil surfaces with DOM and its fractions were suggested to be the major processes determining atrazine sorption on soils. The results of this work provide a reference to the agricultural use of organic amendment such as sewage sludge for improving the availability of atrazine in soils.     

The Role of CEC and pH in Cd Retention from Soils of North of Iran

Cadmium (Cd) is a critical environmental chemical in which sorption reactions control its entry into soil solution. The aim of the present study was to evaluate Cd sorption characteristics of some soils of the northern part of Iran with a wide range of physicochemical properties. Duplicates of each sample were equilibrated with solutions containing 5 to 500 mg Cd L^?1 with 0.01 M CaCl₂ as background solution. The quantity of Cd retention was calculated as the difference between initial and equilibrated Cd concentration. Sorption isotherms including Freundlich, Langmuir, Temkin, Dubinin-Radushkevich, and Redlich-Peterson were used to evaluate the behavior of Cd sorption. Cadmium sorption data were well fitted to Langmuir, Freundlich, and Redlich-Peterson isotherms. The constant of Freundlich equation (k_F ) and adsorption maxima (b_L ) of Langmuir equation were related to pH and cation exchange capacity (CEC). The maximum buffering capacity (K_d ) was significantly correlated with pH (R² = 0.52, p ≤ 0.001) and calcium carbonate equivalent (CCE) (R² = 0.63, p ≤ 0.001). Redlich-Peterson constants (k_RP and a_RP ) were significantly correlated with pH (R² k_RP = 0.30, p ≤ 0.007) and (R² a_RP = 0.27, p ≤ 0.012). It seemed that pH, CEC, and CCE were the main soil properties regulating Cd retention behavior of the studied soils.     

Desorption of Pyrene from Freshly-Amended and Aged Soils and its Relationship to Bioaccumulation in Earthworms

Desorption of pyrene was studied in freshly-amended and 120 d-aged samples of six different soils using a Tenax-assisted method in order to evaluate the influence of soil properties and aging time on desorption. The correlations between desorption percentage (P _d ), rapid desorption rate constant (k _rap ), and biota to soil accumulation factor (BSAF) were analyzed. Results showed that in soils with a relatively high soil organic matter (SOM) content (> 1% in this study), P _d and k _rap decreased with the increase of SOM content both in freshly amended and aged soils. This suggests that SOM is the key component for sorption organic pollutants by providing highly active combination sites, where the combined pollutant becomes difficult to desorb. In soils with a relatively low SOM content (< 1%), clay minerals played an important role through offering nanopores to entrap pollutant molecules, making it difficult for these molecules to diffuse out. Aging significantly reduced the rate and extent of pyrene desorption. It is reasonable to deduce that, during aging, some of the pyrene molecules moved from “readily desorbing sites” to “relatively slower desorbing sites,” which led to a reduction of desorption. Ln P _d showed a linear relationship with ln BSAF for both freshly-amended and aged soils, and ln k _rap only in aged soils. In freshly-amended soils, rapid desorption in some soils is too quick to be the limiting step for bioaccumulation, and, therefore, the elevation BSAF became insignificant when k _rap was larger than 3 × 10 ^{? 3} h ^{? 1} .     

Relationship between the weathering of clay minerals and the nitrification rate: a rapid tree species effect

We compared the properties of the clay mineral fraction and the composition of soil solutions in a Fagus sylvatica coppice (native forest) and four adjacent plantations of Pseudotsuga menziesii, Pinus nigra, Picea abies and Quercus sessiliflora planted in 1976. The results revealed changes of clay fraction properties due to tree species effect. Clay samples from Douglas fir and pine stands differ when compared to other species. Twenty-eight years after planting, we observed the following changes: a more pronounced swelling after citrate extraction and ethylene glycol solvation, a higher CEC and a smaller poorly crystallised aluminium content. All these changes affecting the clay fraction agreed well with soil solution analyses which revealed high NO₃ ^?, H⁺ and Al concentrations under Douglas fir and pine. These changes were explained by a strong net nitrification under Douglas fir and pine stands when compared with other tree species. The higher NO₃ ^? concentrations in soil solutions should be linked to the presence, type and activity of ammonia-oxiding bacteria which are likely influenced by tree species. The production of NO₃ ^? in excess of biological demand leads to a net production of hydrogen ion and enhances the dissolution of poorly crystallised Al-minerals. Secondary Al-bearing minerals constituted the principal acid-consuming system in these soils. As a consequence, the depletion of interlayer spaces of hydroxyinterlayered minerals increases the number of sites for exchangeable cation fixation and increases CEC of the clay fraction. The dissolution of Al oxy-hydroxides explain the increase in Al concentrations of soil solutions under Douglas fir and pine stands when compared to other species. Nitrate and dissolved aluminium were conjointly leached in the soil solutions. A change in environmental conditions, like an introduction of tree species, enough modifies soil processes to induce significant changes in the soil mineralogical composition even over a period of time as short as some tens of years. Generally, mineral weathering has been considered to be very slow and unlikely to change over tens of years, resulting in few studies capable of detecting changes in mineralogy. This study appears to have detected changes in clay mineralogy during a period of 28 years after the planting of forest species. Our study represents a single location with a limited block design, but causes us to conclude that the observed changes could be widely representative. Where available, archived samples should be utilized and long-term experiments set up so that similar changes can be tested for and detected using more robust designs. The plausible hypothesis we present to explain apparent changes in clay mineralogy has strong relevance to the sustainable management of land.     

Clay Mineralogy of Central Victorian (Creswick) Soils: Clay Mineral Contents as a Possible Tool of Environmental Indicator

The clay mineralogy and heavy metal/metalloid (As, Pb and Cu) contents of soils developed on the various rock units in a central highlands environment in Victoria (Creswick, Australia) have been investigated. The clay minerals identified showed an order of abundance as: kaolinite ? illite > smectite > mixed-layer (ML) ≈ vermiculite. The soil clay mineralogy did not change systematically with depth (0～ 10, 10～ 20 and 20～ 30 cm) and showed large variations spatially. The high proportion of kaolinite was probably due to the removal of 2:1 phyllosilicates by the formation of 1:1 kaolinite through weathering, which also reduced the cation exchange capacity (CEC) and electrical conductivity (EC, soil: water ratio of 1:5) of soils by aging. Soils were classified as silty loam to loam with a low clay size (≤ 2μ m) fraction. The soils were acidic to moderately acidic with pH ranging from 4.5 to 7.1, averaging 5.7. Concentrations of As, Pb, and Cu (average values 24.3, 16.7 and 11.0 mg/kg, respectively) did not show an association with the clay mineral contents except vermiculite. The occurrence of smectite and mixed-layer clay contents, although far lower than kaolinite and illite, contributed significantly to CEC of soils. The study area was affected by mining, high natural background As values dominate the area and the role of clay minerals in fixation of metalloid/metals was found to be less significant. Low organic matter content (average ～ 6.5%), low soil surface area (average ～ 1.0 m²/g) and the high proportion of kaolinite mineral content result in a limited ability to fix heavy metals. The role of Fe oxides appeared to be a key influence in the fixation of As and other potentially toxic metals, rather than the clay minerals, and therefore requires further research. This work highlighted the importance of the determination of types and amounts of clay minerals of natural soils in environmental management.     

Effect of biotite,zeolite, heavy clay,bentonite and apatite on the uptake of radiocesium by grass from peat soil

Biotite is a potassium rich mineral, which is used as a fertilizer in organic farming and as a soil amendment in conventional farming. Its ability to reduce ¹³⁴Cs uptake by ryegrass from peat soil was studied in pot experiments and compared with zeolite, heavy clay, bentonite and apatite. In addition, the long-term effect of biotite on ¹³⁷Cs uptake from peat soil was studied in the peat field. In the pot experiments in the first cut of ryegrass, the minerals decreased ¹³⁴Cs uptake by plants in the following order: zeolite > heavy clay > bentonite > biotite > apatite. Apatite did not have any effect on the plant ¹³⁴Cs level. In the later cuts, the uptake of ¹³⁴Cs from biotite-treated soil decreased further while that from soils treated with other minerals remained unchanged or even increased. In general, ¹³⁴Cs uptake by plants decreased with increasing mineral level. The decrease of ¹³⁴Cs uptake became more efficient, especially at the early growth stage, by mixing small amounts of zeolite in biotite. The results of the field experiment indicated the long-term effect of biotite on reducing ¹³⁴Cs uptake by plants. Biotite application rate was 30 t ha-1. The five-year mean of the plant/soil concentration ratio of ¹³⁷Cs was 0.05 for biotite-treated soil, in contrast to 0.14 for the control soil. On the whole, biotite reduced considerably the ¹³⁷Cs level of plants on peat soil and this effect was long-lasting. For an effective reduction of plant radiocesium a great quantity of biotite is needed and therefore it is most suitable for greenhouse cultivation where contaminated slightly decomposed peat is used as a growing medium.     

Temperature and vegetation effects on soil organic carbon quality along a forested mean annual temperature gradient in North America

Both climate and plant species are hypothesized to influence soil organic carbon (SOC) quality, but accurate prediction of how SOC process rates respond to global change will require an improved understanding of how SOC quality varies with mean annual temperature (MAT) and forest type. We investigated SOC quality in paired hardwood and pine stands growing in coarse textured soils located along a 22 °C gradient in MAT. To do this, we conducted 80‐day incubation experiments at 10 and 30 °C to quantify SOC decomposition rates, which we used to kinetically define SOC quality. We used these experiments to test the hypotheses that SOC quality decreases with MAT, and that SOC quality is higher under pine than hardwood tree species. We found that both SOC quantity and quality decreased with increasing MAT. During the 30 °C incubation, temperature sensitivity (Q₁₀) values were strongly and positively related to SOC decomposition rates, indicating that substrate supply can influence temperature responsiveness of SOC decomposition rates. For a limited number of dates, Q₁₀ was negatively related to MAT. Soil chemical properties could not explain observed patterns in soil quality. Soil pH and cation exchange capacity (CEC) both declined with increasing MAT, and soil C quality was positively related to pH but negatively related to CEC. Clay mineralogy of soils also could not explain patterns of SOC quality as complex (2 : 1), high CEC clay minerals occurred in cold climate soils while warm climate soils were dominated by simpler (1 : 1), low CEC clay minerals. While hardwood sites contained more SOC than pine sites, with differences declining with MAT, clay content was also higher in hardwood soils. In contrast, there was no difference in SOC quality between pine and hardwood soils. Overall, these findings indicate that SOC quantity and quality may both decrease in response to global warming, despite long‐term changes in soil chemistry and mineralogy that favor decomposition.     

Reaction of labelled65ZnCl2,65ZnEDTA and65ZnDTPA with different clay-systems and some alluvial Egyptian soils

Summary The clay fraction separated from an alluvial Egyptian soil and montmorillonite clay mineral were equilibrated with CaCl₂ or NaCl solution then treated with humic acid isolated from composted clover straw to obtain different clay systems: Ca-clay, Ca-clay-HA, Na-clay, Na-clay-HA, Ca-mont and Ca-mont-HA. These clays as well as seven soil samples were reacted with different amounts of labelled⁶⁵ZnCl₂,⁶⁵ZnEDTA and⁶⁵ZnDTPA. The effectiveness of these Zn-sources for maintaining soluble Zn²⁺ ions in the equilibrium solution was the greatest for ZnDTPA and the lowest for ZnCl₂. Ca-clay provided greater Zn sorption capacity than Na-clay, and complexing the clay with humic acid depressed its capacity for Zn sorption. At the pH of the clay-systems (pH=6.5), the possibilities of Zn(OH)₂ formation were reduced especially in the presence of Zn-chelates. Reactions of⁶⁵ZnE DTA and⁶⁵ZnDTPA with the seven soils produced higher levels of soluble Zn²⁺ ions in the equilibrium solution rather than⁶⁵ZnCl₂ meanwhile ZnDTPA was more effective than ZnEDTA. The calculated Zn(OH)₂ ion product in the solution of ZnCl₂-soil systems indicated the precipitation of Zn as Zn(OH)₂. However, this was not valid in the Zn-chelates-soil systems. The results also revealed the role of soil carbonate, organic matter and soil texture as soil variables affecting Zn sorption by natural soils.     

Regionalization of sorption capacities for arsenic and cadmium

To fulfill the purpose as a sink for trace elements, soils must not be overloaded with As and Cd. Therefore, it is necessary to get knowledge of the sorption capacities of soils on a regional scale. The determination of these sorption capacities for large areas is, however, impeded by the great expenditure of laboratory work involved. With data presented here retention capacities for cadmium and arsenic from routinely determined soil parameters are estimated. In batch experiments the sorption behaviour of 40 soils from the area of Freiberg/Saxony in Germany was examined. The obtained sorption isotherms from the laboratory were fitted to the Freundlich equation (S = k^*C^m). The two constants (k, m) of this equation were used for multiple linear regression to correlate the sorption capacity and the soil parameters, namely clay content, pH value, total organic carbon, and dithionite extractable Fe contents. Due to long lasting ore mining of Freiberg there exist high background levels in that area for the two surveyed elements As and Cd. Therefore, this study offers two different mathematical procedures to take these contaminations into account. Thus the experimental data were corrected before they were fitted to Freundlich and pedotransfer equations were determined. Using the transfer equation, parameter k and m for cadmium sorption could be estimated with statistical certainties of 91% and 61% (adjusted R²), respectively, whereas the predictability for the arsenic sorption is not practicable because achieved R₂ values are very low (17% and 7%). This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date. This revised version was published online in June 2006 with corrections to the Cover Date.     

Status of copper in some calcareous and non-calcareous soils of Egypt

Summary To assess the status of copper in Egyptian soils, surface and subsurface soil samples were collected from various geographical regions of Egypt and of various genesis. The samples were analyzed for the total Cu, water-soluble plus exchangeable as well as the acid-extractable and EDTA-extractable Cu. The total Cu varied between 3.5 and 72.3 ppm. Less than 2% of this copper was in the soluble plus exchangeable form. The highest values of total and soluble plus exchangeable copper were found in the alluvial soils while the sandy soils had the least amounts. This was attributed to the high clay and organic matter content of the alluvial soils in addition to the dominance of montmorillonitic clay minerals in their fine fraction. The calcareous soils showed intermediate values of total and soluble plus exchangeable Cu due to their lower organic matter and clay mineral content. The clay mineralogy of these soils revealed the dominance of illitic and kaolinitic minerals which are relatively poor in Cu and other trace elements.Because of their relatively higher organic matter content, the alluvial soils had a large percentage (up to 43%) of their total Cu in the EDTA extractable form. The calcareous soils, on the other hand, had a large percentage (up to 52%) of their Cu in the acid-extractable form. The EDTA extractable Cu was correlated with the organic matter content of the soils. Since the pH of the EDTA extract was found to be dependent on the CaCO₃ content of the soils, it was suggested that the method be modified so that the final pH of the extract is constant for all soils.     

Slow vapor‐phase desorption of toluene from several ion‐exchanged montmorillonites

The sorption and desorption of volatile compounds from soils and clays exhibit a wide range of kinetics. While much of the sorptive interaction is very rapid, a certain fraction of volatile compounds that enter soil and clays are only slowly desorbed. It is generally believed that the formation of this recalcitrant or slowly desorbing fraction of volatile organic compounds (VOCs) in soils is due to the diffusion of compounds to poorly accessible sorption sites. However, the exact nature of these sites is in doubt. In montmorillonite, there are two likely possibilities for formation of the recalcitrant fraction: sites between the clay lamella and sites within clay particle aggregates. Because montmorillonite may be an important fraction of many soils, we have explored the formation of slowly desorbing toluene on a montmorillonite clay that was ion exchanged with five different ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, and Fe³⁺) to form mineralogically similar clays with varying interlamellar spacing. The recalcitrant fraction was quantified for varying sorption and desorption times. The type of ion exchanged into the clay appears to have an important influence on the formation of a recalcitrant fraction.     

Phosphate sorption isotherms for evaluating phosphorus requirement of wetland rice soils

Summary Phosphate sorption isotherms were developed for five Philippine wetland rice soils using the conventional technique and a modified one. In the conventional method, P requirements of soils varied between 280 and 810 g P/g soil. In the modified method, they varied from 160 to 540 g P/g soil at 0.2 ppm P in solution. Soils with high P-sorption capacities had vermiculite and halloysite as the dominant clay minerals. Soil reduction by flooding decreased P-sorption by 28–70 percent at 0.2 ppm P in solution. The decrease in P-sorption due to soil reduction was greatest in a crystalline soil with vermiculite and halloysite as the dominant clay minerals and least in a soil with dominant X-ray amorphous silicates in the clay fraction.Desorption of freshly adsorbed P under reduction was greater in HCO ₃ ^– solution than in CaCl₂ and it increased with level of applied P. Desorption patterns of freshly adsorbed P were similar to adsorption patterns but values of P in solution were lower at desorption. Soils varied with respect to desorption of freshly sorbed P. Desorption studies indicate that soils vary in intensity factor with respect to P and thus influence P availability to plants. Use of P-sorption and P-desorption data obtained under reduced soil condition was proposed for detecting P needs of submerged rice soils.Results of a pot study with IR36 at different levels of solution P (reduced) in one soil indicated a high degree of correlation between adjusted P levels and the measured growth parameters. About 0.12 ppm P in the soil solution or 0.46 ppm P desorbed in HCO ₃ ^– solution (equivalent to 100 mg P/kg soil) was adequate for near-maximum plant height, tiller production, total dry matter yield, plant P content, and total P uptake.     

Root uptake and distribution of radiocaesium from contaminated soils and the enhancement of Cs adsorption in the rhizosphere

Uptake by roots from contaminated soil is one of the key steps in the entry of radiocaesium into the food chain. We have measured the uptake by roots of radiocaesium and its transfer to shoots of a heathland grass, sheep fescue (Festuca ovina L.) from two contrasting agricultural soils, a sandy podzol and a clayey calcareous soil. A culture device which keeps the roots separate from the soil was used thus allowing rhizosphere soil to be obtained easily and enhancing the effect of root action. Biomass production and ¹³⁷Cs in shoots and roots were recorded. Cs adsorption was studied on both the initial, nonrhizosphere soil and on rhizosphere soil in dilute soil suspension. Cs desorption was measured by resuspending subsamples of contaminated soil in solutions containing various concentrations of stable Cs. The proportion of Cs fixed, i.e. not readily desorbable, was calculated by comparison of the adsorption and desorption isotherms. Uptake by roots varied considerably between soils and did not appear to be diffusion limited. Root-to-shoot transfer did not differ for the two soils studied. Root action considerably enhanced Cs adsorption on the soils, particularly the in sandy podzol with a low Cs affinity. The value of K_d was increased by up to an order of magnitude. A large proportion of adsorbed Cs was found to be fixed, the K_d was up to seven times greater on desorption than adsorption, indicating that up to 80% of adsorbed Cs was not readily exchangeable. Root action had little effect on the fixed fraction. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fate and Transport of High Explosives in a Sandy Soil: Adsorption and Desorption

Several areas of the Massachusetts Military Reservation (MMR) have soils with significant levels of high explosives (HE) contamination because of a long history of training and range activities (such as open burning, open detonation, disposal, and artillery and mortar firing). Site-specific transport and attenuation mechanisms were assessed in sandy soils for three contaminants of concern: the nitramine hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and the nitroaromatics 2,4-dinitrotolune (2,4-DNT) and 2,4,6-trinitrotoluene (TNT). For all three contaminants, linear distribution coefficients (K_d) were dependent on the fraction of organic carbon in soil. The nitroaromatics sorbed much more strongly than RDX in both soils. Over 120 hours, the desorption rate of RDX from field contaminated surface soil was much slower than its sorption rate, with the desorption K_d (1.5 L/kg) much higher than K_d for sorption (0.37 L/kg). Desorption of 2,4-DNT was negligible over 120 hours. Thus, applying sorption-derived K_d values for transport modeling may significantly overestimate the flux of explosives from MMR soils. Based on multiple component column transport tests, RDX will be the most mobile of these contaminants in MMR soils. In saturated columns packed with uncontaminated soil, RDX broke through rapidly, whereas the nitroaromatics were significantly attenuated by irreversible sorption or abiotic transformations.     

Decomposition and sorption characterization of plant cuticles in soil

The sorption of organic compounds by plant cuticular matter has been extensively investigated; however, little has been studied regarding the effect of plant cuticle degradation on their role in the sorption of organic compounds in soils. The sorption of phenanthrene was studied in soil samples which had been incubated for up to 9 months with three different types of plant cuticle isolated from tomato fruits, pepper fruits and citrus leaves. The main change in the diffuse reflectance Fourier-transform infrared (DRIFT) spectra during incubation of the cuticles was related to cutin decomposition. The peaks assigned to methyl and ethyl vibration and C=O vibration in ester links decreased with decomposition. In general, with all samples, the phenanthrene sorption coefficients calculated for the whole incubated soils (K _d) decreased with incubation time. In contrast, the carbon-normalized K _d values (K _oc) did not exhibit a similar trend for the different cuticles during incubation. The origin of the cuticle also affected the linearity of the sorption isotherms. With the tomato and citrus cuticle samples, the Freundlich N values were close to unity and were stable throughout incubation. However with the green pepper cuticle, the N values exhibited a significant decrease (from 0.98 to 0.70). This study demonstrates that the structural composition of the plant cuticle affects its biodegradability and therefore its ability to sorb organic compounds in soils. Of the residues originating from plant cuticular matter in soils, the cutan biopolymer and lignin-derived structures appear to play a dominant role in sorption as decomposition progresses. Responsible Editor: Alfonso Escudero.     

Copper Sorption Behavior of Selected Soils of the Oasis in the Middle Reaches of Heihe River Basin,China

The mobility and bioavailability of copper (Cu) depends on the Cu sorption capacity of soil and also on the chemical form of Cu in soils. Laboratory batch experiments were carried out to study the sorption and distribution of Cu in nine soils differing in their physicochemical properties from the oasis in the middle reaches of Heihe river basin, China: desert soil (S-1), agricultural soils (S-2, S-3, S-8, and S-9), marshland soil (S-4), and hungriness shrub soils (S-5 and S-6). Copper sorption behavior was studied using the sorption isotherm and sequential extraction procedure. In general, the sorption capacity for Cu decreased in the order: S-4 > S-9 > S-2 > S-8 > S-3 > S-6 > S-5 > S-7 > S-1. The correlation results suggest that soils with higher CEC, silt, clay, CaCO3, and organic matter will retain Cu more strongly and in greater amounts than soils that are sandy with lower CEC, CaCO3, and organic matter. pH is not an important impact factor to Cu sorption in experimental soil samples because pH in soils used in this study had a narrow range. The distribution of sorbed Cu varied between nine soils studied and depended on both soil properties and initial added Cu concentration. There are significant differences in the distribution of Cu in each soil with the increase of initial Cu concentration. The predominance of Cu associated with the available fraction, which was over 50% of the total sorbed Cu in most cases, indicates that the change of geochemical conditions might promote the release of Cu back into soil solution thus impacting organisms in the soils. The added Cu has also the tendencies to locate in the residual fraction, which was larger than 5% of the total amount extracted from the four fractions in most soils.     

Geochemistry and clay mineralogy of soils eaten by Japanese macaques

Three groups of soils from two Japanese monkey parks at Arashiyama (Honshu) and Takasakiyama (Kyushu) were analyzed for their geochemistry and clay and primary mineral content. Two groups (Y and T) of soils are regularly eaten by Japanese macaques; a third group (N) is not eaten. Of the elements analyzed, soil group N (not eaten) is within the range of all elements in the Y group, and is very different from the T group. These preliminary data suggest there is no chemical stimulus in soil eating behaviour. We also analyzed the mineralogy of the clay fraction (<2 μm) but could find only a possible stimulus from ingesting plagioclase and orthoclase minerals. The clay mineral content consists of small to trace amounts of metahalloysite that might play a role in countering the effects of diarrhea. However, from the available data there are no clear trends that would provide a stimulus for geophagic behaviour.     

Hysteretic Behavior of Imidacloprid Sorption-Desorption in Soils of Croatian Coastal Regions

Sorption and desorption are important processes that influence the transport, transformation, and bioavailability of imidacloprid in the soils. Equilibrium batch experiments were carried out using six coastal Croatian soils. The equilibrium sorption and desorption experimental data showed the best fit to the Freundlich equation. Sorption parameters predicted with the Freundlich model, K_F ^sor and 1/n ranged from 2.92 to 5.74 (mg/kg)/(mg/L)^1/n, and 0.888 to 0.919, respectively. The sorption of imidacloprid was found to be sensitive to organic carbon (OC) content. The highest sorption was observed in Krk soil (OC 4.74%) and the lowest in Zadar soil (OC 1.06%). Fitted desorption parameter values, K_F ^des , were consistently higher than those associated with sorption. The opposite trend was observed for the exponential parameter 1/n. Results also suggested that imidacloprid sorption-desorption by soil is concentration-dependent, i.e. at lower imidacloprid concentrations a greater sorption percentage and lower desorption percentage occurred. Desorption studies revealed that there was a hysteresis effect in all the tested soils. Hysteresis coefficient values (H) varied from 0.656 to 0.859. The study results emphasize that the controlled application of imidacloprid is obligatory, especially in soils with a low organic carbon content, in order to minimize a risk of environmental and groundwater pollution.     

Short-term effects of biological and physical forces on aggregate formation in soils with different clay mineralogy

The mechanisms resulting in the binding of primary soil particles into stable aggregates vary with soil parent material, climate, vegetation, and management practices. In this study, we investigated short-term effects of: (i) nutrient addition (Hoagland's solution), (ii) organic carbon (OC) input (wheat residue), (iii) drying and wetting action, and (iv) root growth, with or without dry–wet cycles, on aggregate formation and stabilization in three soils differing in weathering status and clay mineralogy. These soils included a young, slightly weathered temperate soil dominated by 2:1 (illite and chlorite) clay minerals; a moderately weathered soil with mixed [2:1 (vermiculite) and 1:1 (kaolinite)] clay mineralogy and oxides; and a highly weathered tropical soil dominated by 1:1 (kaolinite) clay minerals and oxides. Air-dried soil was dry sieved through a 250 m sieve to break up all macroaggregates and 100 g-subsamples were brought to field capacity and incubated for 42 days. After 14 and 42 days, aggregate stability was measured on field moist and air-dried soil, to determine unstable and stable aggregation respectively. In control treatments (i.e., without nutrient or organic matter addition, without roots and at constant moisture), the formation of unstable and stable macroaggregates (> 250 m) increased in the order: 2:1 clay soil < mixed clay soil < 1:1 clay soil. After 42 days of incubation, nutrient addition significantly increased both unstable and stable macroaggregates in the 2:1 and 1:1 clay soils. In all soils, additional OC input increased both unstable and stable macroaggregate formation. The increase in macroaggregation with OC input was highest for the mixed clay soil and lowest for the 1:1 clay soil. In general, drying and wetting cycles had a positive effect on the formation of macroaggregates. Root growth caused a decrease in unstable macroaggregates in all soils. Larger amounts of macroaggregates were found in the mixed clay and oxides soil when plants were grown under 50% compared to 100% field capacity conditions. We concluded that soils dominated by variable charge clay minerals (1:1 clays and oxides) have higher potential to form stable aggregates when OC concentrations are low. With additional OC inputs, the greatest response in stable macroaggregate formation occurred in soils with mixed mineralogy, which is probably a result of different binding mechanisms occurring: i.e., electrostatic bindings between 2:1 clays, 1:1 clays and oxides (i.e. mineral-mineral bindings), in addition to OM functioning as a binding agent between 2:1 and 1:1 clays.