POLYACRYLAMIDE CHARACTERISTICS RELATED TO SOIL APPLICATIONS

Water soluble polyacrylamides (PAMs) have been proposed as soil amendments for various agricultural purposes. Recent interest has centered on very high molecular weight (10-20 g mol-1), low to moderate charge (10-20 mol %) anionic materials, added to irrigation water to prevent silt loss from irrigated fields. These PAMs are within a broad spectrum of commercially available compounds employed for a variety of applications in other industries. These include solid-liquid separations in clarification of potable and waste waters, dewatering of sludges, mining separations, food processing and paper making, as well as petroleum recovery, textile additives, friction reduction, personal care products, and cosmetics. This paper reviews PAM characteristics (chemistry, synthesis, molecular weight, product form), residual monomer concentrations, 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 biodegradable in soil and aquatic environments. Anionic PAMs exhibit low toxicity to mammalian systems (oral and dermal LD50 > 5 mg Kg-1) and fish (LC50 > 100 mg L-1).