EFFECTS OF LONG-CHAIN ALIPHATIC-COMPOUNDS ON THE AGGREGATE STABILITY OF A LACUSTRINE SILTY CLAY

Microbial activity and soil aggregate stability of a waterlogged silty clay low in organic carbon were studied following the incorporation of a naturally occurring source of long chain aliphatic compounds (beeswax). The microbial activity was reduced significantly by the beeswax addition, irrespective of the amount added. The beeswax components were selectively adsorbed by the silty clay resulting in "free" and "associated" long chain aliphatic (LCA) fractions. The "free" LCA fraction which remained extractable with chloroform was composed of neutral hydrophobic aliphatic compounds, whereas the "associated" LCA were mainly compounds rich in acid and polar functional groups associated with charged sites of the clay. The "associated" LCA increased by 3.5 to 4 times the resistance of soil aggregates to slaking forces of water, whereas effects of "free" LCA were transient and accessory by coating and imbedding soil aggregates.