摘要:

Solubility and kinetic data indicated that concentrations of aluminum (Al) extracted with 1MKCl are determined by the solubility of a precipitated A1(OH)3phase in soils dominated by variable charge minerals. Kinetic studies examining the release of Al on non‐treated and KCl treated residues indicated the precipitation of an acid‐labile Al phase during the extraction procedure. The log ion activity products estimated for the KCl extracts ranged between 8.1–8.6 for the reaction Al(OH)3+ 3H+< = > Al3++ 3H2O, which was similar to the solubility product of several Al(OH)3phases. The mechanism proposed for Al precipitation indicated that Al released by exchange with added K+hydrolyzed and released H+that was readily adsorbed on surfaces of variable charge minerals. The increased ionic strength of the extracting solution further increased the amount of H+adsorbed to the variable charge surface and reduced the H+concentration in the aqueous phase. Consumption of H+induced further hydrolysis of Al, resulting in supersaturation of the extracting solution and formation of polynuclear hydroxy Al species. It was concluded that the 1MKCl extraction does not quantitatively extract salt exchangeable Al from variable‐charge soils.

ISSN:0010-3624    

DOI:10.1080/00103629409369182

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

To assess the interaction of water soluble stabilizing agents with soil particles, soil microaggregation was studied after treatments with two uncharged organic conditioners, Polyvinyl alcohols (PVAs) and Dextrans, of different molecular weight. The size distribution of microaggregates (diameter <250 pm) was determined on two soils of low organic matter contents with differing texture by means of a laser light technique. PVAs and Dextrans modified the microaggregate size distribution, increasing the proportion of >75 μm aggregates. The extent of this modification increased with the molecular weight of the conditioners and, for the same molecular weight, decreased with increasing amount of conditioner used. The aggregating effect of PVAs was stronger on particles smaller then 5 μm, which formed microaggregates in the range 10–100 μm which were not broken down even by ultrasonication. S.E.M. micrographs of soil aggregates confirmed the results reported above. PVAs and Dextrans appeared to produce a more porus structure with more aggregates of about 100 μm size, both in the clay soil and, to a lesser extent, in the sandy soil.

ISSN:0010-3624    

DOI:10.1080/00103629409369183

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103629409369161

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor