Demand-Driven Model for Global Phosphate Rock Suggests Paths for Phosphorus Sustainability.

Phosphorus is required as a fertilizer for producing food, and there is no substitute. Losses between mine production and diet result in significant environmental harm. We used a demand-driven substance flow model to explore the sensitivity of global phosphorus production to interventions of the food system including: reduction in animal fraction in the diet (AFD); manure use efficiency (MUE); animal food yield (YA); phosphorus use efficiency (PUE); the fraction of food that is wasted (FWF); the fraction of food waste recycled (FRE); and the fraction of human waste recycled (WRE). The model indicated that AFD and YA are the most influential interventions, and they interact with PUE and MUE. Furthermore, there is a minimum in AFD and YA below which it becomes necessary to increase mining. Another result is that reducing food waste is about 80 times more effective than recycling food waste in reducing P demand. Finally, the model was used to explore the global carrying capacity for humans on the basis of P sources other than mining. These sources may satisfy P requirements for as many as 2.5 billion people. If significant improvements were made in all of the considered interventions simultaneously, as many as 14.7 billion people could be sustained.

Symbolic regression of upstream, stormwater, and tributary E. coli concentrations using river flows.

Symbolic regression was used to model E. coli concentrations of upstream boundary, tributaries, and stormwater in the lower Passaic River at Paterson, New Jersey. These models were used to simulate boundary concentrations for a water quality analysis simulation program to model the river. River flows from upstream and downstream boundaries of the study area were used as predictors. The symbolic regression technique developed a variety of candidate models to choose from due to multiple transformations and model structures considered. The resulting models had advantages such as better goodness-of-fit statistics, reasonable bounds to outputs, and smooth behavior. The major disadvantages of the technique are model complexity, difficulty to interpret, and overfitting. The Nash-Sutcliffe efficiencies of the models ranged from 0.61 to 0.88, and they adequately captured the upstream boundary, tributary, and stormwater concentrations. The results suggest symbolic regression can have significant applications in the areas of hydrologic, hydrodynamic, and water quality modeling.

Bioregeneration of spent anion exchange resin for treatment of nitrate in water.

Anion exchange resin treatment is a commonly used technique for removal of nitrate from water. However, spent anion exchange resins are themselves regenerated using brine solution, which produces spent solution containing a high concentration of nitrate and salt. The present study developed a bioregeneration technique for conversion of nitrate on the spent resins to nitrogen gas while eliminating the use of brine solutions. Batch experiments were conducted to investigate the effect of biomass content, pH, salinity, and molar ratio of exogenous organic carbon to nitrate on the kinetics of bioregeneration. The bioregeneration rate decreased when pH increased from 7 to 10. It increased with increasing microbial concentration from 8.3 to 13.8 g/L as volatile suspended solid (VSS) and with decreasing conductivity of the regeneration suspension from 31 to 9 mS/cm. Spent exchange resins were effectively regenerated within 5 h under the optimal conditions and the regenerated resins could be used repeatedly for filtration removal of nitrate from water. A desorption-denitrification model was developed to describe bioregeneration kinetics. Modeling results indicated that the bioregeneration was through desorption of nitrate from the spent resin and subsequent denitrification of the soluble nitrate. Denitrification was the rate-limiting process. This research demonstrated the feasibility of using a biological process to regenerate nitrate-saturated resins.

Extrapolating phosphorus production to estimate resource reserves.

Various indicators of resource scarcity and methods for extrapolating resource availability are examined for phosphorus. These include resource lifetime, and trends in resource price, ore grade and discovery rates, and Hubbert curve extrapolation. Several of these indicate increasing scarcity of phosphate resources. Calculated resource lifetime is subject to a number of caveats such as unanticipated future changes in resource discovery, mining and beneficiation technology, population growth or per-capita demand. Thus it should be used only as a rough planning index or as a relative indicator of potential scarcity. This paper examines the uncertainty in one method for estimating available resources from historical production data. The confidence intervals for the parameters and predictions of the Hubbert curves are computed as they relate to the amount of information available. These show that Hubbert-type extrapolations are not robust for predicting the ultimately recoverable reserves or year of peak production of phosphate rock. Previous successes of the Hubbert curve are for cases in which there exist alternative resources, which is not the situation for phosphate. It is suggested that data other than historical production, such as population growth, identified resources and economic factors, should be included in making such forecasts.

Developmental control of inositol phosphate biosynthesis is altered in the brain of both curly and phenotypically normal straight tail mutant mice.

BACKGROUND: Altered levels of inositol phosphate in the central nervous system (CNS) are hypothesized to produce distorted brain signaling and lead to numerous neurologic maladies. Little is known of mechanisms controlling the complex metabolic flux of inositol phosphate. Less is known of controls that regulate inositol-phosphate biosynthesis in the mammalian brain. The expression of 1L-myo-inositol-1 phosphate synthase (MIP), the only enzyme known to synthesize inositol phosphate, was studied in the brain of normal (CBA) and curly tail (CT) mutant mice. The CT strain exhibits a neural tube defect, spina bifida, responsive to inositol supplementation, but not to folic acid treatment. METHODS: Utilizing enzyme assays to determine the specific activity of MIP, Western blotting to detect expression, gas chromatography/mass spectrometry to measure inositol concentration, and statistical analyses to evaluate quantitative data, MIP expression was analyzed in newborn, young, and adult brains of CBA and CT (curly tail [ct-CT] and straight tail [st-CT]) mutant mice. RESULTS: Data analyses suggest there is a significant difference in MIP activity in the brain of CBA mice as compared to that of CT mutant mice and that temporal and spatial control of MIP expression and inositol concentrations are altered in the brain of both the ct-CT and phenotypically normal st-CT mutant. Moreover, two differentially expressed forms of MIP were identified in the adult mouse brain. CONCLUSIONS: These findings implicate a role for MIP in the maturation of the CNS and evoke a hypothesis regarding the regulation of inositol phosphate biosynthesis in brain development.