Polyacrylamide as an organic nitrogen source for soil microorganisms with potential effects on inorganic soil nitrogen in agricultural soil

Linear polyacrylamide (PAM) is gaining considerable acceptance as an effective anti-erosion additive in irrigation water. The potential effects of repeated PAM application on soil microbial ecology and the potential for biotransformation of this polymer in soils are not completely known. Untreated and PAM-treated soils (coarse-silty, mixed, mesic Durixerollic Calciorthids) were collected from agricultural fields near Kimberly, ID. Soils were analyzed to determine the effects of PAM treatment on bacterial counts and inorganic N concentrations and the potential for PAM biotransformation. Culturable heterotrophic bacterial numbers were significantly elevated in PAM-treated soil for the plot planted to potatoes; this effect was not observed in the plot planted to dry pink beans. Total bacterial numbers, determined by AODC, were not altered by PAM treatment in any of the soils sampled. Polyacrylamide-treated soil planted to potatoes contained significantly higher concentrations of NO3 and NH 3 (36.7 ± 2.20 and 1.30 ± 0.3 mg kg-1 , respectively) than did untreated soil (10.7 ± 2.30 and 0.50 ± 0.02 mg kg-1, respectively). For bean field soil there was no difference between treated and untreated soil inorganic N concentrations. Enrichment cultures generated from PAM-treated and untreated soils utilized PAM as sole N source, but not as sole C source. While the monomeric constituents of PAM, acrylamide and acrylic acid, both supported bacterial growth as sole C source, the PAM polymer did not. Enrichment cultures that used PAM for N exhibited amidase activity specific for PAM as well as smaller aliphatic amides. Utilization of PAM for N, but not for C, indicates that ultimately PAM may be converted into long chain polyacrylate, which may be further degraded by physical and biological mechanisms or be incorporated into organic matter

Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides

t Polyacrylamide (PAM) is currently used as an irrigation water additive to significantly reduce the amount of soil erosion that occurs during furrow irrigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been reported in PAM-treated field soils; the substrate specificity of the induced amidase is uncertain. PAM-treated and untreated soils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene acetamide. Based on results obtained with a soil amidase assay, there was no difference between PAM-treated and untreated soils with respect to the rate of amide bond hydrolysis of any of the agrochemicals tested. It appears that under these assay conditions the PAM-induced soil amidase is not active toward the amide bonds within these molecules. However, carbaryl was hydrolyzed by a different soil amidase. To our knowledge, this is the first soil enzyme assay-based demonstration of the hydrolysis of carbaryl by a soil amidase

Polyacrylamide as a substrate for microbial amidase in culture and soil

High molecular weight, linear polyacrylamide (PAM) with anionic charge is added to agricultural soils as an anti-erosion additive. Research indicates that soil microorganisms are able to utilize PAM as a source of N and that inorganic N pools are altered in some PAM-treated soils. The potential role of hydrolytic amidase activity in the microbial utilization of PAM for N was investigated. Intracellular and extracellular amidase activity was measured over time in enrichment cultures which used PAM as sole N source. Enzyme activity increased concomitant with cell growth and N removal from PAM. Cell growth, N removal and amidase production were dependent upon readily-available C in the medium. Amidase activity and substrate specificity were determined for PAM-utilizing enrichment cultures exposed to various N sources. Polyacrylamide-specific amidase activity appears to be inducible, and not constitutive, based on the lack of amidase activity in cultures supplied with only ammonium nitrate for N versus substantial activity when PAM was added as an amendment with or without ammonium nitrate. Cultures amended with propionamide exhibited amidase activity largely specific for this small amide substrate, while cultures supplied with PAM as sole N source exhibited amidase activity specific for formamide, propionamide and PAM. Amidase activity and substrate specificity were determined for PAM-treated and untreated agricultural field soils. Polyacrylamide-specific amidase activity was higher in PAM-treated soil (14.86 ± 14.0 pg NH4 released soil) than in untreated soil (1.02 ± 2.3 pg NH4 released C I soil); activity specific for low molecular weight amides was slightly elevated or unchanged in PAM-treated soil as compared with untreated soil

Polyacrylamide as a substrate for microbial amidase in culture and soil

High molecular weight, linear polyacrylamide (PAM) with anionic charge is added to agricultural soils as an anti-erosion additive. Research indicates that soil microorganisms are able to utilize PAM as a source of N and that inorganic N pools are altered in some PAM-treated soils. The potential role of hydrolytic amidase activity in the microbial utilization of PAM for N was investigated. Intracellular and extracellular amidase activity was measured over time in enrichment cultures which used PAM as sole N source. Enzyme activity increased concomitant with cell growth and N removal from PAM. Cell growth, N removal and amidase production were dependent upon readily-available C in the medium. Amidase activity and substrate specificity were determined for PAM-utilizing enrichment cultures exposed to various N sources. Polyacrylamide-specific amidase activity appears to be inducible, and not constitutive, based on the lack of amidase activity in cultures supplied with only ammonium nitrate for N versus substantial activity when PAM was added as an amendment with or without ammonium nitrate. Cultures amended with propionamide exhibited amidase activity largely specific for this small amide substrate, while cultures supplied with PAM as sole N source exhibited amidase activity specific for formamide, propionamide and PAM. Amidase activity and substrate specificity were determined for PAM-treated and untreated agricultural field soils. Polyacrylamide-specific amidase activity was higher in PAM-treated soil (14.86 ± 14.0 pg NH4 released soil) than in untreated soil (1.02 ± 2.3 pg NH4 released C I soil); activity specific for low molecular weight amides was slightly elevated or unchanged in PAM-treated soil as compared with untreated soil

Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides

t Polyacrylamide (PAM) is currently used as an irrigation water additive to significantly reduce the amount of soil erosion that occurs during furrow irrigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been reported in PAM-treated field soils; the substrate specificity of the induced amidase is uncertain. PAM-treated and untreated soils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene acetamide. Based on results obtained with a soil amidase assay, there was no difference between PAM-treated and untreated soils with respect to the rate of amide bond hydrolysis of any of the agrochemicals tested. It appears that under these assay conditions the PAM-induced soil amidase is not active toward the amide bonds within these molecules. However, carbaryl was hydrolyzed by a different soil amidase. To our knowledge, this is the first soil enzyme assay-based demonstration of the hydrolysis of carbaryl by a soil amidase

Magnetic ion exchange drinking water treatment in a large-scale facility

The MIEX (c) (Magnetic Ion Exchange) process, which employs an anion exchange resin for removal of dissolved organic carbon (DOC), was introduced at the Wanneroo Groundwater Treatment Plant in Western Australia in 2001. In this pilot-scale study we examined a range of operational parameters for optimisation of biofiltration of MIEX (R)-clarified waterl. Granular Activated Carbon (GAC) outperformed anthracite as a filter medium. Increasing the empty bed contact time (EBCT) from 8 to 16 minutes improved performance. The GAC biofilters removed up to 20% of DOC and up to 25% of Biodegradable Dissolved Organic Carbon (BDOC), once they had stabilised in biological mode. Chlorine demand was reduced by 51 to 55% and trihalomethane formation potential (THMFP) was reduced by 35 to 50% in GAC biofilter effluent waters at 16 minutes EBCT when compared with their MIEX (R)-treated influent water. GAC biofilters developed more biomass on the surface than anthracite biofilters and this was associated with the greatest BDOC and DOC removals. Interestingly, neither biofilters developed populations of protozoans. Use of chlorinated influent water severely restricted biomass development in all biofilters at surface. Biofilter treatment of chlorinated influent water resulted in the poorest removal of Assimilable Organic Carbon (AOC). Biofiltration improved the water quality of MIEX (R)-clarified waters

Polyacrylamide as an organic nitrogen source for soil microorganisms with potential effects on inorganic soil nitrogen in agricultural soil

Linear polyacrylamide (PAM) is gaining considerable acceptance as an effective anti-erosion additive in irrigation water. The potential effects of repeated PAM application on soil microbial ecology and the potential for biotransformation of this polymer in soils are not completely known. Untreated and PAM-treated soils (coarse-silty, mixed, mesic Durixerollic Calciorthids) were collected from agricultural fields near Kimberly, ID. Soils were analyzed to determine the effects of PAM treatment on bacterial counts and inorganic N concentrations and the potential for PAM biotransformation. Culturable heterotrophic bacterial numbers were significantly elevated in PAM-treated soil for the plot planted to potatoes; this effect was not observed in the plot planted to dry pink beans. Total bacterial numbers, determined by AODC, were not altered by PAM treatment in any of the soils sampled. Polyacrylamide-treated soil planted to potatoes contained significantly higher concentrations of NO3 and NH 3 (36.7 ± 2.20 and 1.30 ± 0.3 mg kg-1 , respectively) than did untreated soil (10.7 ± 2.30 and 0.50 ± 0.02 mg kg-1, respectively). For bean field soil there was no difference between treated and untreated soil inorganic N concentrations. Enrichment cultures generated from PAM-treated and untreated soils utilized PAM as sole N source, but not as sole C source. While the monomeric constituents of PAM, acrylamide and acrylic acid, both supported bacterial growth as sole C source, the PAM polymer did not. Enrichment cultures that used PAM for N exhibited amidase activity specific for PAM as well as smaller aliphatic amides. Utilization of PAM for N, but not for C, indicates that ultimately PAM may be converted into long chain polyacrylate, which may be further degraded by physical and biological mechanisms or be incorporated into organic matter