Abstract:

This paper reviews the recent progress in study of the variety, sources, conversion, and content organic acids(i.e. low molecular mass organic acids, OAs), as well as the methodology of their determination. The objective was to better understand ecological functions of OAs in temperate forest ecosystems. In summary, OAs in forest soils had about 40 varieties, including aliphatic and aromatic acids, among which the most were low molecular weight OAs. They were mainly the metabolites from decomposition of organic matters, secretion from tree roots and microorganisms. The litters played an important role. A series of conversions would happen once OAs released, including biodegradation, sorption by solid phase and complexation with metals, the sorption by complexation had especially more important ecological functions by affecting elements availabilities,such as phosphorus, iron; The concentration of individual OAs was the balances result between the processes of synthesis and the degradation, and ranged from micromolar to millimolar. The contents in O and A horizons were higher than those in B horizon, and mono carboxylic acids were higher than di tricarboxylic acids; In determining OAs, they usually needed to be extracted from various samples, and then the extract purified and concentrated before determining their variety and content done including extraction, purities and concentrations, OAs in liquid samples could be extracted by column chromatography or liquid liquid distribution, and in solid ones by extracting solvents. And then the extract is concentrated by such as rotary evaporator and nitrogen blowing concentrator, high performance liquid chromatography, ion chromatography and gas chromatography are mainly employed for determining of OAs, and the methods should be chosen on the applicability.

Key words: forest soils, low molecular mass organic acids, variety and source, conversion and concentrations, determination