Zinc Sorption Behavior in Soils with Divergent Characteristics

Adsorption studies are important to determine the retention and release of applied plant nutrients and the efficiency of fertilization. The present study was conducted to delineate the zinc (Zn) adsorption behavior of soils with varying characteristics. In this study, adsorption behavior of Zn was studied at varying Zn concentrations and temperatures in three different soils collected from the Research Farm of Indian Agricultural Research Institute (IARI), New Delhi (Inceptisols, Typic Haplustepts), soil (Inceptisols, Typic Ustocrept) from a farmer’s field in Shamgarh, Karnal, Harayana, and the Hayathnagar Research Farm of Central Research Institute For Dryland Agriculture (CRIDA), Hyderabad, (Haplustalf). The results of this study revealed that the adsorption of Zn as well as differential buffering capacity (DBC) was greater in Typic Haplustepts of IARI and Typic Ustocrept of Karnal than Haplustalf of CRIDA, Hyderabad. However, the supply power as well as percentage saturation (% sat.) was greater in Haplustalf of CRIDA, Hyderabad, than Typic Haplustepts of IARI and Typic Ustocrept of Karnal The results also revealed that irrespective of the soil types, Zn adsorption increased with an increase in Zn concentration and increase in temperature from 20 °C to 35 °C. When the adsorption data were fitted to isotherms, Langmuir and Freundlich isotherm fits were excellent, as evidenced by high r² (0.71 to 0.99) values. Thermodynamic parameters such as standard free energy (ΔG) were negative in both Typic Haplustepts and Typic Ustocrept soils, indicating spontaneous Zn adsorption reaction, but nonspontaneous reaction was observed in the case of Haplustalf soils.. Interestingly, both standard enthalpy (ΔH) and standard entropy (ΔS) were negative in all the three types of soils studies. The analogy and results of the present study would be useful in deciding the Zn fertilizer needs for a given soil type.     

Sorption and Desorption Behavior of FTuoroquinolone Antibiotics in an Agricultural Soil

<正>Dear Editor,Fluoroquinolones(e.g.,ciprofloxacin(CIP),enrofloxacin(ENR),and levofloxacin(LEV))are an extensively used family of antibiotics prescribed for various infections;however,they are also increasingly used     

不同添加剂对土壤中乙草胺吸附／解吸的影响

采用批处理恒温振荡法,利用气相色谱一质谱联用仪研究了人工添加不同吸附物质对土壤中乙草胺的吸附／解吸作用。结果表明,人工添加不同吸附物质对土壤中乙草胺的吸附强度和吸附容量不同,不同的添加剂对土壤中乙草胺的吸附／解吸作用均呈现明显的非线性关系,可用Freundlich模型描述。并且随着土壤中添加量的增大,吸附强度增大、吸附容量增大、所得吸附等温线的非线性也逐步增大;另外,添加剂对乙草胺的解吸迟滞作用也随添加剂含量的增高而更加明显。但是不同添加剂对土壤中乙草胺的吸附能力有明显差异,其中煤粉的吸附能力最大,其次是壳聚糖,沸石最小。     

Sorption Behavior of Brilliant Blue FCF by a Fe-Zeolitic Tuff

The adsorption of Brilliant Blue FCF from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-ray diffraction. Sorption kinetic, isotherms, dose and pH effects were determined and the adsorption behavior was analyzed. Kinetic pseudo-first order and linear isotherm models were successfully applied to the experimental results, indicating that the sorption mechanism is physisorption. Experiments in columns were performed and breakpoint was found in 100 min using a concentration of 5 mg/l.     

暗棕壤中低分子有机酸的吸附与生物降解研究

低分子有机酸在森林生态系统中普遍存在,在根际和多种成土过程中发挥重要作用,但有机酸发挥作用的能力和效率与其在土壤中的吸附与降解等行为关系密切。本文研究了草酸、柠檬酸和苹果酸等低分子有机酸在森林暗棕壤A1层和B层的吸附及生物降解行为,结果表明,低分子有机酸加入到暗棕壤后迅速被土壤固相颗粒所吸附,其中对草酸的吸附远强于柠檬酸和苹果酸,三种低分子有机酸在暗棕壤A1层的吸附率强于B层;草酸、柠檬酸和苹果酸加入到森林暗棕壤后还能迅速被微生物降解,其中对草酸的降解远低于柠檬酸和苹果酸,暗棕壤对草酸较强的吸附作用可能是其生物降解率较低的主要原因,且三种低分子有机酸在A1层暗棕壤中的生物降解率高于B层。     

Differential Sorption Behavior of Cadmium,Lead, Zinc,and Copper in Some Tropical Soils and Their Environmental Implications

This study evaluated cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) sorption characteristics of three tropical soils. Data obtained conformed to Freundlich sorption model and the S-shaped isotherm curve. Sorption efficiency of Zn and Pb were highest in alkaline soil while slightly acid soil had the highest Cd and Cu sorption efficiency for monometal sorption. In competitive sorption, metals were more sorbed in slightly acid soil while the least efficiency was recorded in acid soil. Distribution coefficient; K_d (average across soil types) in monometal sorption followed the order: Pb > Zn > Cd > Cu. For competitive sorption, the order was Zn > Pb > Cu > Cd. When in competition, Cd was preferentially sorbed in slightly acid and alkaline soils and Zn for acid soil. Conclusively, lead is more in equilibrium solution when in competition with Cd, Zn and Cu making it potential agent of soil and groundwater pollution.     

Sorption Behavior of 4-Chlorophenol from Aqueous Solutions By a Surfactant-modified Mexican Zeolitic Rock in Batch and Fixed Bed Systems

The removal of 4-chlorophenol from aqueous solutions by both a Mexican clinoptilolite-heulandite zeolitic rock and the modified zeolitic material with the surfactant hexadecyltrimethylammonium bromide (HDTMABr), using batch and packed-bed (column) configurations, was investigated. The unmodified zeolitic rock did not show any adsorption of 4-chlorophenol. The effects of pH, contact time and concentration of 4-chlorophenol on the adsorption process by the surfactant modified material were examined. The sorption of 4-chlorophenol was not affected by the pH range from 4 to 9.5. 4-chlorophenol retention reached equilibrium in about 18 h and the rate of 4-chorophenol adsorption by the modified material was faster in the first 10 h than later. The experimental data were treated with the models: pseudo-first order, pseudo-second order, fractional power and Elovich models. Although, the last three gave correlation coefficients higher than 0.96, the pseudo-second order model was the best to describe the reaction rate. The experimental data follow a linear isotherm which is characteristic for sorption of organic solutes by the partition mechanism. The Bed Depth-Service Time Model was applied to the sorption results in order to model the column operation. The results showed that the surfactant modified zeolitic rock could be considered as a potential adsorbent for 4-chlorophenol removal from aqueous solutions.     

Kinetic and Thermodynamic Behavior on the Sorption of Clindamycin from an Aqueous Medium by Modified Surface Zeolitic Tuffs

Clindamycin (CLD), an antibiotic derivate of lincomycin, is widely used; the presence of this drug in the wastewater and the environment could produce resistance in bacteria. In this work, the sorption of this drug by two surfactant-modified zeolitic tuffs was studied considering contact time, initial concentration, pH, and temperature. The kinetic behavior indicates that the equilibrium times were between 15 and 12 h for all materials, and the results were best adjusted to Ho and Mc Kay model. The highest adsorption was obtained with the hexadecyltrimethylammonium-modified zeolitic tuff from Oaxaca, Mexico (1.56 mg/g). The sorption isotherms obtained showed a linear behavior, indicating a partition mechanism. The thermodynamic parameters were determined from the isotherms at different temperatures and Van Ho equation; the processes are exothermic and not spontaneous. The best pH for the adsorption is between 8 and 11. The results show that the modified zeolitic tuffs are potential materials for the adsorption of CLD from water.     

Sorption Behavior of Ofloxacin to Kaolinite: Effects of pH,Ionic Strength,and Cu(II)

Sorption of antibiotics to clay minerals is a key process controlling their transport and fate in environment. In this study, the effects of pH, ionic strength, and Cu(II) on ofloxacin (OFL) sorption to kaolinite were investigated by batch sorption experiments. The results of sorption edge experiments suggested that OFL sorption to kaolinite was pH and ionic strength dependent. Cation exchange was a major contributor to the sorption of OFL⁺ to kaolinite. The decreased OFL sorption with increasing ionic strength indicated the formation of outer-sphere complexation. When solution pH was lower than 7.0, Cu-OFL complexes facilitated OFL sorption through electrostatic attraction or formation of kaolinite-Cu-OFL and kaolinite-OFL-Cu ternary surface complexes. However, existence of free Cu(II) cation in solution competed for sorption sites, and thus suppressed OFL sorption. When solution pH was higher than 7.0, Cu(II) existed as Cu(OH)₂, and the Cu-OFL complexes in aqueous phase and solid phase (precipitation) enhanced OFL removal efficiency from solution. The results imply that Cu(II) effects should be taken into account in the evaluation of OFL mobility in environment.     

Thermodynamics of Lead Sorption and Desorption in Soils

Thermodynamics of Lead (Pb) sorption and desorption was investigated with samples of a clayic Torrifluvent, a sandy clayic Calciorthid, and sandy Quartzipsamment. The values of activation energy for Pb sorption on the Calciorthid (ranged from 20.7 to 27.7 kJ mol^?1) were higher than those of the Torrifluvent (ranged from 3.4 to 17.4 kJ mol^?1) and the Quartzipsamment (1.5 to 4.6 kJ mol^?1). The energies of activation for adsorption “E_a” were greater than those for desorption “E_d”, indicating that more energy was needed to sorb Pb than to desorb Pb. The enthalpy of activation (ΔH^*) values indicate that Pb sorption is endothermic reaction while Pb desorption is exothermic reaction. The entropy of activation (ΔS^*) values for Pb sorption were negative and increased with increasing surface coverage. The free energy of activation (ΔG^*) values ranged from 81.2 to 89.2 and from 83.6 to 84.0 kJ mol^?1 for Pb sorption and desorption respectively.     

Action of Oxidants on Water Sorption, 2H Nuclear Magnetic Resonance Mobility,and Glass Transition Behavior of Gluten

Oxidation of vital wheat gluten with potassium bromate and ascorbic acid significantly extends or broadens glassy-rubber transition to a higher final temperature range or moisture content. Thermomechanical and deuterium nuclear magnetic resonance (NMR) data show that the increased stiffness due to oxidation could be detected from the thermomechanical and deuterium NMR mobility level, indicating increased rigid fractions. The oxidation also resulted in increased water sorption, but no significant change in “freezable” water, and a much decreased mobile deuterium NMR signal. Room temperature sorption of water resulted in a glassy-rubbery transition over a ≈10–20% mc range for the control. For the oxidized sample, it started at ≈10%mc, but the transition was gradual and extended into much higher moisture ranges that corresponded to a more rigid fraction of deuterium (NMR) signal. This suggests that the oxidative interactions led to a more rigid gluten fraction, extending the transition to a higher temperature range, perhaps resulting in a more elastic dough.     

Sorption and fate of perchlorate in arid soils

The mobility of perchlorate in soils depends on several factors, including soil mineralogy and the presence of other oxyanions that compete with perchlorate for the retention sites. Currently, there are no studies that evaluate the mobility of perchlorate in arid soils. The present study evaluated the mobility of ClO₄^– in three arid soils, Canchones, Humberstone and Pica, exposed to two ClO₄^– concentration ranges and different ionic strengths. In Humberstone (non-agricultural) and Pica (agricultural) soils, the sorption processes were not important for both concentration ranges, while Canchones soil (agricultural) showed a decrease in perchlorate concentration associated with microbial degradation processes. The increase of medium ionic strength by addition of Ca(NO₃)₂ only had an important effect on Humberstone soil, associated with the presence of kaolinite and muscovite (variable charge). A competition effect was observed between perchlorate, nitrate and other anions presents in solution by absorption sites generated from variable charge mineral and calcium. Considering the quite low sorption capacity of the soils and the high solubility, perchlorate can be absorbed by fruit and vegetables of export in concentrations over the healthy levels established by international organization.     

Sorption Kinetics and Transformation of DDT in Sediment

The overall objective of this study was to investigate the sorption kinetics of DDT in sediment under similar experimental conditions employed in corresponding toxicity studies for bentic organisms. A batch of aerated Schoonrewoerdse Wiel sediment, initially spiked with DDT, was sampled over a period of seven days. Concentrations of DDT, DDD and DDE were determined in both the solid and the solution phase in the sediment/water system after separation by centrifugation. It was found that the extractable amount of DDT decreased with increasing contact time. This can partly be explained in terms of transformation of DDT into DDD. Furthermore, the present applied extraction procedure seems to be less effective with increasing contact time, indicating an increase in binding strength of DDT with the sediment material. Finally, on the basis of DDT, DDE and DDD concentrations in both the solid phase and the solution phase, partition coefficients were calculated, which appeared to be independent of the contact time. This points at a very rapid equilibrating between DDT in pore water and in the extractable forms adsorbed at the solid phase.     

四环素类抗生素在土壤和堆肥中的吸附和降解

Two agricultural soils were collected from Dahu and Pinchen counties and swine manure compost (SMC) from Ping-tung County in Taiwan, China to investigate the sorption and dissipation of three tetracyclines (TCs), i.e., oxytetracycline (OTC), tetracycline (TC) and chlortetracycline (CTC), in compost, soils and soil/compost mixtures with different organic carbon (OC) contents. There were seven treatments in total. TCs were most strongly adsorbed to SMC in all treatments due to the high OC content. When SMC was present in the soils, the sorption of TCs was significantly enhanced, which might be attributed to the increased OC content and CEC. The adsorption of TCs showed non-linear adsorption isotherms and fitted well to the Freundlich model. After 49 d of incubation at 25 ℃ in soils and soil/compost mixtures in the dark, TCs elapsed in all substrates, with the time required for 50% degradation (DT₅₀) between 20 and 41 d, and the time for 90% degradation (DT₉₀) between 68 and 137 d. Soil amended with compost enhanced the stability of TCs and reduced their mobility. The dissipation of TCs in a soil environment was slow, indicating that these compounds might be persistent in soil.     

Zinc Sorption in Selected Soils

Abstract

The adsorption of nutrient elements is one of the most important solid‐ and liquid‐phase interactions determining the retention and release of applied plant nutrients and the efficiency of fertilization. The study showed that the soils with high cation exchange capacity (CEC), CaCO₃, organic matter contents, and heavy texture adsorbed more zinc (Zn). The alkaline soils from Pakistan adsorbed more Zn than English acidic soils. Langmuir and Freundlich isotherm fit was excellent, and r² values for the Langmuir isotherm were highly significant (r²=0.84 to 0.99). The Langmuir b values, representing the adsorptive capacity of a soil, increased as the texture fineness increased in the soil, with increases in the concentration of adsorptive material (such as organic matter and CaCO₃) and with increases in CEC and pH. The alkaline soils from Pakistan had higher bonding energy constant and higher log Kf values than the acidic English soils. Sequential extraction of Zn in these soils showed that most of the Zn was held in CaCO₃ pool in the alkaline soils, whereas in acidic soils adsorbed Zn was in exchangeable form.     

铬在土壤中的吸附解吸研究进展

对铬在土壤中的吸附解吸研究进行了综述,土壤中铬的吸附解吸机理包括非专性吸附(离子交换吸附)、专性吸附以及物理表面吸附,分别对pH、氧化还原电位、土壤组分(土壤矿物和有机质)、竞争离子以及离子强度等因素对铬吸附解吸的影响作了论述。文章进一步描述了土壤中铬吸附解吸的数学模型Freundlich方程、Langmuir方程、一级动力学模型、金属-腐殖酸模型(one-sitemodel)和表面络合模型-扩散层模型(DLM)等的研究情况,并对今后的研究方向进行了探讨。     

Sorption and desorption of Zn on Ca-Kaolinite

Experiments on Zn²⁺ sorption-desorption by Ca-kaolinite using a wide range of Zn²⁺ concentrations and two acid pH values allowed us to reach the following conclusions: (1) For Zn²⁺ surface coverages below the kaolinite C.E.C., Zn²⁺ was sorbed mainly via ion exchange; (2) At Zn^2? sorption values above the C.E.C., Zn²⁺ was sorbed with higher affinity by a mechanism stronger than ion exchange, involving a strong association of Zn ions with silicate solid phases; and (3) Use of C.E.C. values and/or Langmuir's calculated maxima would greatly underestimate Zn²⁺ sorption capacity by kaolinite, even at acid pH values.     

Sorption and Degradation of Selected Fungicides in the Turfgrass Canopy

Microbial degradation of fungicides on leaf surfaces after repeated applications to turfgrass was investigated. Prior andcurrent work in our laboratory has identified two characteristicsof the turfgrass leaf system that may contribute to the enhanceddegradation of fungicides after repeated application to turfgrass:(1) The leaf surface is rich in microorganisms (～10⁸ g^-1 dr wt leaf), and (2) Leaf surface microorganisms may respond to repeated fungicide applications in a manner consistentwith the phenomena of enhanced biodegradation. Field studies wereconducted on ‘Penncross' creeping bentgrass with four fungicidesrepresenting three chemical families applied either two or eight times in one growing season. Biodegradation was estimated using data from both a field study and a parallel laboratory study thatfollowed the fate of ¹⁴C-labelled fungicides. For the laboratory incubations, the locations of the residual ¹⁴C fungicides were estimated using a sequential extraction protocolthat fractionated the materials into three pools: available,retained and bound. Data from both the field and laboratory studyrefuted our hypothesis that enhanced biodegradation would developfollowing repeated applications of the fungicides onto the leafsurface. Our studies support a conclusion that a two-stagephysical sorption process leads to plant incorporation and thiscontrols most of the fungicide's fate. Thus, our data suggestthat microbial activity plays a less important part in theprocess than would be indicated by considering the size of themicrobial population on the leaves.