Nitrogen flux reduction

As for CO2, VOCs can also be removed by using immobilized liquid membranes. Obuskovic et al. [35] immobilized a thin layer of silicone oil in the microporous of the hollow fiber polypropylene membrane beneath the dense-coated skin. The performance of the system has been proved for toluene, methanol, and acetone removal from N2. With respect to the simple hollow fiber, the presence of the oil layer led to a 2-5 VOC more enriched permeate (due to the reduction of nitrogen flux) with a separation factor of 5-20 times higher (depending on the VOC and the feed gas flowrate). The membrane was stable for 2 years. 

Figure 3. The general nitrogen model for illustrating the bio geochemical cycling in Forest ecosystems. Explanations for the fluxes 1, ammonia volatilization 2, forest fertilization 3, N2-fixation 4, denitrification 5, nitrate respiration 6, nitrification 7, immobilization 8, mineralization 9, assimilatory and dissimilatory nitrate reduction to ammonium 10, leaching 11, plant uptake 12, deposition N input 13, residue composition, exudation 14, soil erosion 15, ammonium fixation and release by clay minerals 16, biomass combustion 17, forest harvesting 18, litterfall (Bashkin, 2002).

Dissolved organic nitrogen also shows some reduction in mineral soil solution relative to the organic soil horizon. Although few data are currently available for mineral soil solution DON concentration and flux, DON reduction in mineral soil is comparable to that of DOC (Fig. 5). 

For the determination of arsenic in biological material approx. 300 mg of dried matter was sealed in ultraclean silica vials, irradiated at a thermal neutron flux of approximately 9x1 o n cm sec . After irradiation the vials were washed with concentrated nitric acid, frozen in liquid nitrogen to reduce the internal pressure and crushed in a plastic container. The samples were then decomposed under pressure with a mixture of concentrated nitric and sulphuric acid, evaporated to near dryness after opening the vessels, taken up in hydrochloric acidic solution, made up to volume and after reduction with Kl subjected to an arsine generation step. The evolved arsines were trapped, the trap sealed into a polyethene vessel and the 560 keV gamma photopeak from As counted. The authors reported absolute detection limits of either 0.5 fig or 0.05 fig depending on the detector used (Orvini and Delfanti, 1979)... 

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