LOW-MOLECULAR ORGANIC-ACIDS IN THE RHIZOSPHERE SOIL SOLUTION OF BEECHFOREST (FAGUS-SYLVATICA L) CAMBISOLS DETERMINED BY ION CHROMATOGRAPHYUSING SUPPORTED LIQUID MEMBRANE ENRICHMENT TECHNIQUE

Soil solution from the A-horizon (0-5 cm) beneath six different plant cover types of beech forest Dystric Cambisols, south Sweden, was expel led by high-speed centrifugation using freshly sampled soil at field m oisture. Concentrations of low molecular weight organic acids (LOAs) w ere determined by an application of ion chromatography using a support ed liquid membrane enrichment technique. This method facilitates the d etection of LOAs at 60-200 nM in complex matrices and (most important in acid soil solutions) minimizes interferences from Al and Fe. To tes t the capacity of soils to immobilize LOAs from solution, the recovery of added LOAs was also studied. Between 8 and 10 LOAs were detected i n measurable concentrations in most soil solutions. Monocarboxylic aci ds (acetic, lactic and formic acid) were the most abundant, though rat her consistent differences were measured in several acids among the ve getation types, partly related to vascular plant species and soil acid ity. There were also consistent differences between seasons (late spri ng and summer). However, recovery tests (20 min) with several of the s oils clearly demonstrated that added LOAs were to a great extent rapid ly immobilized, with the exception of acetic and lactic acid. probably a main reason for the high share of these monocarboxylic acids in soi l solutions. The ecological relevance of determining LOAs in soil solu tions is discussed briefly. Copyright (C) 1996 Elsevier Science Ltd