Analysis of residual acrylamide in field crops

Polyacrylamide (PAM) is a widely used product for a large number of applications. Many of the emerging applications are in the area of agriculture. PAM is blended with pesticides as a thickening agent, added to irrigation water to minimize soil erosion, and used as a medium for hydroponically grown crops. Although PAM is stable and considered to be safe, residual acrylamide (AMD) monomer is a neurotoxin and animal carcinogen. In this work, residual AMD is analyzed in a variety of crops that were grown under PAM treatment to stabilize soil erosion. Corn, potatoes, sugar beets, and beans are analyzed for AMD. A sample of the crop is homogenized with water, and the water layer is filtered and derivatized with bromine to form 2,3-dibromopropionamide. The derivative is then extracted with ethyl acetate and converted to the more stable 2-propenamide prior to gas chromatographic analysis using an electron capture detector. Capillary Carbowax columns were used. All tested crops show < 10 ppb AMD. Furthermore, it seems that AMD is not stable when it comes in contact with the crop tissues. In the presence of plant tissues, AMD will disappear as a function of time. Beans blended with 100 ppb AMD for 10 min yield a recovery of only 22%. For a bean sample that was soaked with 500 ppb AMD solution for 18 h, the recovery is 7%. Other crops show different AMD recoveries

Impacts of acid precipitation on decomposition and plant communities in lakes

Over the past few decades the acidity of lakes and rivers has been increasing in several areas of the world. In southern Norway, western Sweden, the Canadian Shield, and the northeastern United States, acidification of fresh waters has become a major environmental problem. It has been clearly established that acid precipitation is the cause of decreasing pH levels in waters of the affected areas. Over most all of northern Europe, southern Scandinavia, and essentiallly all of the U.S. east of the Mississippi River, the mean annual H/sup +/ concentrations in precipitation, expressed as pH, are below 5.0. Furthermore, the regions affected by very acid precipitation (pH &lt; 4.5) are rapidly expanding. The effects of acid precipitation on aquatic ecosystems depend primarily on the geology of the region, but also on the evaluation (orographic precipitation). The regions now known to be the most seriously affected are mountainous districts of southern Scandinavia and the northeastern United States which are located hundreds of kilometers from SO/sub 2/ and NO/sub x/ emissions sources. Regions of the United States which are potentially sensitive to acid inputs because of their geology and surface water alkalinity are also found in the western United States. Local acid precipitation problems are now known on the West Coast, and some lakes in the Puget Sound region appear to be acidified aquatic flora and fauna at all ecosystem levels are greatly impoverished in acidified freshwaters. The numbers of species are reduced and changes in the biomass of some groups of plants and animals have been observed. Decomposition of leaf litterand other organic substrates is hampered, nutrient recycling appears to be retarded, and nitrofication inhibited at pH levels frequently observed in acid-stressed waters

Analysis of residual acrylamide in field crops

Polyacrylamide (PAM) is a widely used product for a large number of applications. Many of the emerging applications are in the area of agriculture. PAM is blended with pesticides as a thickening agent, added to irrigation water to minimize soil erosion, and used as a medium for hydroponically grown crops. Although PAM is stable and considered to be safe, residual acrylamide (AMD) monomer is a neurotoxin and animal carcinogen. In this work, residual AMD is analyzed in a variety of crops that were grown under PAM treatment to stabilize soil erosion. Corn, potatoes, sugar beets, and beans are analyzed for AMD. A sample of the crop is homogenized with water, and the water layer is filtered and derivatized with bromine to form 2,3-dibromopropionamide. The derivative is then extracted with ethyl acetate and converted to the more stable 2-propenamide prior to gas chromatographic analysis using an electron capture detector. Capillary Carbowax columns were used. All tested crops show < 10 ppb AMD. Furthermore, it seems that AMD is not stable when it comes in contact with the crop tissues. In the presence of plant tissues, AMD will disappear as a function of time. Beans blended with 100 ppb AMD for 10 min yield a recovery of only 22%. For a bean sample that was soaked with 500 ppb AMD solution for 18 h, the recovery is 7%. Other crops show different AMD recoveries

Condicionadores químicos e orgânicos na recuperação de solo salino-sódico em casa de vegetação.

A salinização vem promovendo a degradação de solos no Semiárido do Brasil, os quais precisam ser recuperados para que possam ter utilização agrícola. Este trabalho teve como objetivo avaliar o efeito de condicionadores orgânicos e químicos em atributos físico-hídricos de um Neossolo Flúvico salino-sódico, no Sertão de Pernambuco. O experimento foi instalado em colunas de solo, sendo aplicados 10 tratamentos: esterco ovino, esterco bovino, gesso, seis doses de polímero sintético e a testemunha, em delineamento em blocos casualizados. As colunas foram submetidas a lixiviação durante 70 dias e analisadas as soluções percoladas aos sete e 70 dias e os solos após a lixiviação. Nos lixiviados foram medidos o pH e a CE e determinados os teores de Na+, K+ e Cl-; no solo foram medidos o pH e a CE e determinado o teor de Na+ do extrato de saturação, o teor de Na+ trocável e a CTC, para cálculo da PST, além das variáveis físico-hídricas do solo. Os resultados foram submetidos a análise de variância e teste de Scott Knott a 0,05 de probabilidade. Os tratamentos, especialmente os estercos, o gesso e o polímero na menor concentração, diminuíram a CE, a PST e o Na+ solúvel, aumentando a condutividade hidráulica do solo