The effect of interactions between particles on soil infiltrability

Journal of Soils and Sediments - Soil infiltrability is an important topic in environmental and agricultural research and influences plant growth, soil erosion and water runoff. In this study, the...     

The effect of solvent interactions on alpha-, beta-, and gamma-cyclodextrin/flavor molecular inclusion complexes

Three commonly used flavor industry solvents (propylene glycol, triacetin, and triethyl citrate) were tested for their capacity to interfere with the ability of alpha-, beta-, and gamma-cyclodextrin to form molecular inclusion complexes with flavors. Six flavor compounds (ethyl butyrate, ethyl heptanoate, l-menthol, methyl anthranilate, neral, and geranial) were measured by headspace gas chromatography above 2:1 water/ethanol containing appropriate additions of cyclodextrin and flavor solvent. The smallest and most polar solvent molecule represented by propylene glycol had the least effect on cyclodextrin/flavorant complex formation. In contrast, triacetin, intermediate in size among the three flavor diluents studied, had the greatest effect, even though, based on at least some computed molecular parameters, it appears to be more polar than triethyl citrate. The explanation for this apparent anomaly may lie in differences in the extent to which triacetin and triethyl citrate are able to interact with cyclodextrins by means of partial interaction with the hydrophobic cavities of the latter.     

Iodine bonding stabilizes iodomethane in MIDAS pesticide. Theoretical study of intermolecular interactions between iodomethane and chloropicrin

The results are reported of a theoretical study of iodomethane (H(3)C-I, 1) and chloropicrin (Cl(3)C-NO(2), 2), of the heterodimers 3-6 formed by aggregation of 1 and 2, and of their addition products 7 and 8 and their possible fragmentation reactions to 9-18. Mixtures of iodomethane and chloropicrin are not expected to show chemistry resulting from their reactions with each other. The structures and stabilities are discussed of the iodine-bonded molecular aggregates (IBMA) 3 and 4 and of the hydrogen- and iodine-bonded molecular aggregates (IHBMA) 5 and 6. The mixed aggregates 3-5 are bound on the free enthalpy surface relative to the homodimers of 1 and 2, and the IBMA structures 3 and 4 are most stable. This result suggests that the mixture of chloropicrin and iodomethane in the pesticide Midas is a good choice to reduce the volatility of iodomethane because of thermodynamically stabilizing iodine bonding.     

Correlations between soil ph and metal contents in needles of Norway spruce

The concentrations of 21 elements were determined in 1 yr old needles of Norway spruce (Picea abies) at 39 different sites: The following soil parameters were measured at 3 different depths: pH, loss on ignition, total and EDTA-extractable concentrations of 28 elements. Needle concentrations were tested for correlations with soil parameters. The following significant correlations were found with pH: Al, Co, Cs, Mn, and Rb in needles increased with decreasing soil pH, whereas Ba and Sr decreased. Needle concentrations of As, Ca, Cu, Fe, K, La, Mg, P, Sb, Sc, V, and Zn had no significant correlations with soil pH. AI and Ba in needles correlated also with A1 and Ba extracted from the soil. Needle concentrations of the pairs Co and Mn, Cs and Rb, and Ba and Sr showed significant positive interelement correlations, whereas concentrations of P and K had negative interelement correlations with Mn.     

Exploring the effect of organic matter on the interactions between mineral particles and cations with Wien effect measurements

Purpose

Understanding of the interactions between cations, mineral particles, and organic matter (OM) in soils is of paramount importance in plant nutrition and environmental science, and thus, these phenomena have been studied extensively. At present, an effective and simple tool to investigate these interactions does not exist. Based on previous studies of Wien effect in suspensions, the interactions of cations with soil mineral particles, complicated by the presence of organic matter, can be easily determined by means of Wien effect measurements, which was the objective of this study.

Materials and methods

A paddy soil originating from a yellow-brown soil, rich in organic matter, served as a test sample, from which the clay fraction of less than 2 μm in diameter was separated. Organic matter of aliquots of the clay fraction was removed by the oxidation with hot H₂O₂, and the natural and OM-free samples were saturated with various cations: Na⁺, K⁺, Ca²⁺, and Cd²⁺. The effects of OM present in the paddy soil on the interactions between the cations and the soil mineral particles were investigated by measuring the suspension Wien effect with a homemade apparatus, SHP-2.

Results and discussion

The weak electrical field electrical conductivities (EC₀) of suspensions of the natural soils saturated with various cations were higher than those of the OM-free soils. The rate of increase in electrical conductivity of suspensions of the OM-free soil, except that of suspensions saturated with Na⁺, at electrical field strengths >50～100 kV?cm^?1 was higher than those of the natural soil suspensions. The presence of OM increased the mean free binding energies of cations other than Na⁺. The increasing binding energies for K⁺ and Ca²⁺ were 0.56 and 0.57 kJ?mol^?1, respectively, which were significantly larger than the increase for Cd²⁺ as only 0.03 kJ?mol^?1. The binding energies of various cations on both natural and OM-free soils were all in the order: Na⁺?<?K⁺?<?Ca²⁺≈Cd²⁺. As opposed to its effect on the binding energies, the presence of OM reduced the mean free adsorption energies of the cations. Except for Na⁺, the adsorption energies of K⁺, Ca²⁺, and Cd²⁺ at field strengths >50 kV?cm^?1 were lower in the natural soil as compared with the OM-free soil, and the differences between the adsorption energies became larger with increasing field strengths. The presence of OM made the zeta potential of the soil particles saturated with Na⁺ and K⁺ positive, and the particles saturated with Ca²⁺ and Cd²⁺ negative.

Conclusions

Organic matter affected the interactions of cations with soil mineral particles significantly. Binding and adsorption energies, which were quantitative measures of the interactions between cations and soil particles, could be determined by Wien effect measurements in suspensions. The binding energies on natural soils were larger than those on the corresponding OM-free soils, and the adsorption energies on the natural soils were lower than those on OM-free soils.     

可变电荷土壤黏粒表面带电点与离子相互作用的Wien效应表征

To investigate the interactions of oppositely charged sites on the surfaces of variable-charge soil particles with cations and anions, and to evaluate the mean Gibbs free binding and adsorption energies of various cations on particles of red soil and latosol, clay fractions smaller than 2 μm were separated from samples of the two variable-charge soils. Ferric oxides were removed from part of the clay fractions, which were then saturated with various chlorides (NaCl, KCl, CaCl2, CdCl2 or LaCl3). Electrical conductivities (EC) of dilute suspensions of the original and of the iron oxides-free clay fractions in deionized water were measured with the SHP-2 short high-voltage pulse apparatus, which enables measurement of the Wien effect at field strengths (E) from 14 to 250 kV cm-1. The Wien effect (EC-E) curves revealed EC increases of red soil suspensions between 14 to 200 kV cm-1, of 8.3, 8.4, 12.1, 5.9, and 1.2 μS cm-1 for NaCl, KCl, CaCl2, CdCl2, and LaCl3, respectively, reflecting the differing interactions with the various cations and chloride. The EC increments with the iron-free red soil suspensions were higher, being 29.7, 17.2, and 15.3 μS cm-1 for NaCl, CaCl2, and CdCl2, respectively. In the natural latosol suspensions the EC increments were practically zero, whereas in the iron-free fractions there were significant EC increments of 10.3, 5.7, 5.0, and 1.6 μS cm-1 for NaCl, CaCl2, CdCl2, and LaCl3, respectively.     

The stoicheometry of interactions between phosphorus and nutrient cations

Various concentrations of Mg, NH₄, and K in the root solution were studied on uptake of radiophosphorus by the root mass, movement to the xylem sap, and accumulation in the top of intact bean plants. Cation levels ranged from 0.02 to 30.0 mM. Potassium had little effect on radiophosphorus in all three measurements, regardless of the level of cation in the root solution. Magnesium and NH4, on the other hand, increased isotope in the root mass, plant top, and xylem sap. Magnesium was more effective in this respect than NH₄. In all cases the increases in radiophosphorus occurred as an asymptote of cation level in the root solution.     

Relationship between ph measured in water and calcium chloride for soils of Southwestern Australia

Abstract

Soil pH in southwestern Australia (WA) is usually measured either in water (pH_w) or 0.01M CaCl₂ (pH_Ca). There are no published relationships to convert one pH to the other. This has been done in this paper for 236 WA soils: pH_Ca=0.918 pH_w‐0.3556, r²=0.9401. It is, therefore, concluded that, for the majority of soils within WA, it is likely that the linear model proposed for all soils would give the best relationship.     

Electrochemical investigation of the effect of pH and solvent on amitraz stability

The widespread use of the pesticide amitraz for pest control of crops, livestock and honeybees has warranted several studies aimed at understanding the degradation of this compound during storage and use. In particular the degradation of amitraz and the nature of the toxicologically significant intermediates formed owing to pH and solvent type has been examined. In this study we report on the use of electrochemical methods to monitor amitraz degradation and to identify the major intermediates formed. While this study examines the use of rapid voltammetric methods for such analyses, it also resolves earlier studies showing the rapid degradation of amitraz to 2,4-dimethylaniline without formation of intermediates first, and also suggests that the degradation of amitraz to 2,4-dimethylphenylformamide and to 2,4-dimethylaniline is more rapid than previously observed at pH above 3. These studies also showed that amitraz degrades to dimethylphenylformamide in ethanol and methanol, and is stable in both acetonitrile and dimethylsulphoxide.     

喷头类型对药液沉积和麦蚜防效的影响

为研究雾滴尺寸对药液沉积和麦蚜防效的影响,该试验通过选择不同喷头喷施吡虫啉来防治麦蚜。所选德国Lechler生产的3种喷头(LU120-02、AD120-02和IDK120-02)的VMD(volume median diameter,VMD)相差约100μm。试验结果表明:IDK喷头在小麦冠层的平均沉积量显著小于LU和AD,而LU和AD这2个喷头之间没有显著差异性,3种喷头在冠层下部的药液沉积量>中部>上部;LU喷头喷施的药液平均覆盖率显著好于AD和IDK,覆盖率随着雾滴粒径的增加而递减;LU喷头喷施的药液的地面损失最大,且显著高于其他两种喷头;3种喷头都体现了对麦蚜的良好防效;从沉积量、沉积均匀性及地面损失量来衡量,AD喷头优于其他2种喷头。     

Automated sample cleanup for pesticide multiresidue determination. I. Evaluation of solvent partitioning module

An automated continuous flow procedure is described that improves the cost effectiveness and precision of AOAC methodology for multiresidue pesticide determinations in nonfatty foods. Individual modules capable of performing automated solvent partitioning and automated column chromatography were constructed and integrated into a continuous flow system. Data are presented comparing the recoveries and precision for the determination of 8 pesticides (aldrin, dieldrin, p,p'-DDT, ethion, heptachlor epoxide, lindane, parathion, and ronnel) partitioned from 2 food crops (spinach and tomatoes) by both the manual and automated procedures.     

Flavor release and perception in hard candy: influence of flavor compound-flavor solvent interactions

The release kinetics of l-menthol dissolved in propylene glycol (PG), Miglyol, or 1,8-cineole (two common odorless flavor solvents differing in polarity and a hydrophobic flavor compound) were monitored from a model aqueous system via atmospheric pressure chemical ionization mass spectrometry (APCI-MS). Breath analysis was also conducted via APCI-MS to monitor release of l-menthol from hard candy that used PG and Miglyol for l-menthol incorporation. The quantities of l-menthol released when dissolved in PG or Miglyol from the model aqueous system were found to be similar and overall significantly greater in comparison to when dissolved in 1,8-cineole. Analogous results were reported by the breath analysis of hard candy. The release kinetics of l-menthol from PG or Miglyol versus from 1,8-cineole were notably more rapid and higher in quantity. Results from the sensory time-intensity study also indicated that there was no perceived difference in the overall cooling intensity between the two flavor solvent delivery systems (PG and Miglyol).     

植物源农药印楝素微胶囊化工艺及防虫效果

该试验采用界面聚合法,对植物源农药印楝素进行微胶囊化,并通过正交试验优化微胶囊制备的工艺条件,旨在提高印楝素的稳定性,延长其田间防虫持效期.结果表明:壁材采用3∶4(m∶m)的甲苯-2,4-二异氰酸酯(TDD与六亚甲基四胺,芯材与壁材的配比为30∶7(m∶m),溶剂采用3∶2(m∶m)的乙酸乙酯和二甲苯混合溶剂比效适宜,微胶囊中印楝素的包埋率为(83.16±1.22)%.所制得的印楝素微胶囊剂通过盆栽试验表明,对昆虫具有较好的防治效果和较长的持效期.     

用Wien效应研究土壤有机质对阳离子与黄棕壤型水稻土黏粒相互作用的影响

选择富含有机质的黄棕壤型水稻土,提取小于2μm的黏粒,将其中1/2黏粒去除有机质,分别制成为不同阳离子(Na+、K+、NH4+、Ca2+、Cd2+和La3+)饱和的土样,用Wien效应法研究土壤有机质对阳离子与土壤黏粒相互作用的影响。研究结果表明:原土悬液的起始电导率大于去有机质土者;除含Na+悬液外,去有机质土悬液的电导率随场强而增加的速率在50～100 kV cm-1以上,明显大于原土。有机质会使Na+以外的阳离子的平均结合自由能增大,Ca2+的结合能增加最大(增量为0.57 kJ mol-1),而Cd2+的结合能增加最小(增量为0.03 kJ mol-1)。对于供试土壤悬液,不同阳离子的结合能顺序均为Na+相似文献   

The effect of cation–anion interactions on soil pH and solubility of organic carbon

Alkaline soil is widely distributed and cultivated throughout the agricultural regions of the world. Organic carbon (OC) concentrations in alkaline soil are often small, partly because of the limitations of a high pH on the productivity of crops and pastures together with the effects of high pH on the chemistry of soil OC. Soil pH is often hypothesized to be a major factor in regulating OC turnover in agricultural soil, but there are few detailed studies on the effects of high pH on carbon cycling in alkaline soil. Sodium, K⁺, Mg²⁺ and Ca²⁺ are the major cations in alkaline soil, whereas Cl^?, , and are the major anions. The effect of different combinations of these cations and anions on soil pH and OC is not well described in the literature. The objectives of this study were to evaluate the effect of cations and anions on soil pH and to quantify the dissolution of OC in relation to these changes in pH. The results showed that (Na⁺, K⁺ and Mg²⁺) salts and CaCO₃ dominate in the pH range 7.0–8.5, and salts of Na⁺ and K⁺ dominate above pH 8.5. The amount of dissolved OC (DOC) increased significantly as pH increased. Therefore, the presence of large concentrations of and not only increased pH but also promoted the dissolution of soil OC. The concentration of Ca²⁺ modified this effect; large concentrations of Ca²⁺ increased the adsorption and reduced the concentration of DOC.     

The influence of ph on aluminium toxicity in the phytoplankton species Monoraphidium dybowskii and M. griffithii

The toxicity of aluminum on the phytoplankton species Monoraphidium griffithii and M.dybowskii (Chlorophyceae) was investigated. At pH 6.8 and low humus concentration, the growth of both species was reduced at 100–200 μg Al/l, whereas at pH 4.8 only the growth of M.griffithii was affected. The toxicity on the two species showed different relations to the pH-value. The results, supported by analyses of Al-fractions — total acid soluble, total monomeric and none-labile monomeric Al — indicate that the Al-toxicity is species-dependent, and that aluminium, soluble at neutral pH-conditions, can be toxic to the phytoplankton.     

Multiresidue method for the analysis of pesticide residues in fruits and vegetables by accelerated solvent extraction and capillary gas chromatography

An analytical procedure using accelerated solvent extraction and capillary gas chromatography with electron capture and flame photometric detections was developed to simultaneously determine residues of different pesticides in fruits and vegetables. Single laboratory validation of the method was carried out for 28 compounds selected from eight pesticide classes, in blank and fortified samples of fresh pear, cantaloupe, white potato, and cabbage. The method had to meet specific established validation criteria for regulatory purposes applicable to our laboratory. At each of the two fortification levels studied, 24 of the 28 pesticides gave recoveries of more than 70% with a coefficient of variation of less than 10%. With respect to existing procedures, the method showed acceptable limits of detection (from 0.0019 to 0.14 microg/g depending on the pesticide and matrix) while minimizing environmental concerns, time, and labor.     

Relationship of fertilizers on soil ph and fruit disorders of apples and pears

Abstract

In nutrition experiments of fruit‐growing areas of central Washington state, ‘Delicious’ and ‘Golden Delicious’ apple (Malus domestica) orchards and ‘d'Anjou’ pear (Pyrus communis L.) orchards with the lowest soil pH values had a high incidence of fruit disorders and the lowest concentration of leaf calcium (Ca). In contrast, orchards with the highest soil pH values had the highest concentration of soil Ca (meq 100 g^‐1) and the lowest incidence offrait disorders (bitter pit for apples and alfalfa greening, black end and cork spot for pears). Apple orchards with the highest soil pH values also had ‘Delicious’ and ‘Golden Delicious’ apples containing the highest concentration of Ca, but Ca concentrations in ‘d'Anjou’ pears were not significantly different among the different soil pH groups.     

Biostatic effect of fumigation and pesticide drenches on an endomycorrhizal-Rhizobium-legume tripartite association under field conditions

The effects of formaldehyde fumigation and pesticide drenching with Bavistin, Cuman, Copperthom, Sulfex, Furadon, and Termix at recommended rates on vesicular-arbuscular mycorrhizal (VAM) colonisation and Rhizobium sp. nodules were assessed regularly for a period of 90 days in the legumes Cajanus cajan, Dolichos biflorus, Vigna mungo, and V. unguiculata under field conditions. The fumigant and the pesticides initially reduced VAM fungal colonisation and the number of spores in all plants. Following the initial decrease there was a slow recovery, but by 90 days after emergence, root colonisation was either parallel to or still lower than the control, and the number of spores was still well below control levels for all species except C. cajan, which had more VAM spores than the control in all treatments except fumigation and Furadon. Although the number of nodules did not differ from control levels at 30 days after emergence, differences were evident during the later stages of plant growth for all species except V. unguiculata. The effect of pesticides on VAM fungi and root nodulation varied with the associated host plant species. Plant tissue P and VAM colonisation were significantly correlated in all host plants. The pesticide treatments had no marked effect on plant growth, but accumulations of nutrients in pesticide-treated plants were lower than those in untreated plants. Growth and nutrient status of the legumes varied with VAM fungal colonisation.