POLYACRYLAMIDE CHARACTERISTICS RELATED TO SOIL APPLICATIONS

Water soluble polyacrylamides (PAMs) have been proposed as soil amendm ents for various agricultural purposes. Recent interest has centered o n very high molecular weight (10-20 g mol-1), low to moderate charge ( 10-20 mol %) anionic materials, added to irrigation water to prevent s ilt loss from irrigated fields. These PAMs are within a broad spectrum of commercially available compounds employed for a variety of applica tions in other industries. These include solid-liquid separations in c larification of potable and waste waters, dewatering of sludges, minin g separations, food processing and paper making, as well as petroleum recovery, textile additives, friction reduction, personal care product s, and cosmetics. This paper reviews PAM characteristics (chemistry, s ynthesis, molecular weight, product form), residual monomer concentrat ions, toxicology, regulations, and fate and effects in soil and plant systems. Anionic PAMs for soil systems have residual acrylamide (AMD) concentrations of <0.05%. AMD has been found to be readily biodegradab le in soil and aquatic environments. Anionic PAMs exhibit low toxicity to mammalian systems (oral and dermal LD50 > 5 mg Kg-1) and fish (LC5 0 > 100 mg L-1).