A Novel Conductometric Urea Biosensor with Improved Analytical Characteristic Based on Recombinant Urease Adsorbed on Nanoparticle of Silicalite

Development of a conductometric biosensor for the urea detection has been reported. It was created using a non-typical method of the recombinant urease immobilization via adsorption on nanoporous particles of silicalite. It should be noted that this biosensor has a number of advantages, such as simple and fast performance, the absence of toxic compounds during biosensor preparation, and high reproducibility (RSD = 5.1 %). The linear range of urea determination by using the biosensor was 0.05–15 mM, and a lower limit of urea detection was 20 μM. The bioselective element was found to be stable for 19 days. The characteristics of recombinant urease-based biomembranes, such as dependence of responses on the protein and ion concentrations, were investigated. It is shown that the developed biosensor can be successfully used for the urea analysis during renal dialysis

Phosphorus between soil, soil water and overland flow for established and laser graded, border-check irrigation systems

Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affecting water resources worldwide. The effects of soil disturbance on P exports have not been widely reviewed. In February 2004, four established and four recently laser graded (<4 yrs) border-check irrigation bays on the Macalister Research Farm (38°00'S 146°54'E) were sampled during and after irrigation. Samples were taken at the channel inlet and every 60 m thereafter. Overland flow was sampled at the wetting front and back up the bays, and soil samples were recovered from the sampling locations two days after irrigation. Overland flow was analysed for total P (TP), the soil samples were analysed for soil Olsen P (0-20 and 0-100 mm depths) and soil water, dissolved reactive P (SWDRP) and total P (SWTP) (0-20 mm depth)

Changes in nitrogen and phosphorus concentrations in soil, soil water and surface run-off following grading of irrigation bays used for intensive grazing

Soil tests are often used to identify areas at risk of excessive phosphorus (P) exports. We investigated the changes in soil P (0-20 mm) in four recently laser-graded (<1 year) and four established (>10 years) irrigated pastures in south-eastern Australia before and after 3 years of irrigated dairy production. At the second sampling, soil water P and nitrogen (N), and P and N in surface run-off (overland flow) were also measured enabling comparison of P in surface run-off with measures of soil P. In surface soil (0-20 mm), grading reduced measures of soil P, while P sorption increased. Over 3 years, in the graded bays, Olsen P, Colwell P and P sorption decreased and water extractable P and P sorption saturation increased, while Olsen P and Colwell P decreased in the established bays. After 3 years, total dissolved P (TDP) concentrations in soil water were greater in the established bays, but dissolved reactive P (DRP) concentrations were unaffected. Organic P in soil water comprised 70 and 32% of TDP in the established and graded bays, respectively. The soil water analyses were reflected in surface run-off. After 3 years, laser grading decreased TDP, TDN, TP and TN exports in wetting front run-off by 40, 29, 41 and 36%, respectively, compared with established bays. This is an important result for the management of dairy systems as it suggests that the regular cultivation used to renovate pasture on more intensive dairy farms decreases the exports of P and N