Crop Effects on Closed System Element Cycling for Human Life Support in Space

Nutrient recycling in a space-based Bioregenerative Life Support System (BLSS) will require an understanding of nutrient dosage effects on crop production, plant tissue partitioning, and geochemical fates within crop systems. Sodium (Na+), fluoride (F−), and iodide (I−) are found in human waste streams. These elements were examined using crops in hydroponic systems. Lettuce, radish, spinach, and beet were used to study Na+ uptake and tolerance. Spinach, lettuce, and radish growth were inhibited at 8.0 × 10−2 M Na+ compared to the control. Beet growth improved at 2.0 and 4.0 × 10−2 M Na+ compared to the control. Rice plants were used to study F− and I− uptake and tolerance. Rice growth was inhibited at 5.0 × 10−4 M F− and at 5.0 × 10−6 M I−. Solution redox and sorption reactions were predicted with the aid of a chemical equilibrium model. A simulation model was used to predict element fates

Pariette Wetlands Water, Sediment and Plant Total Selenium Concentration

We measured total Selenium in plants from July through November of 2012 and in water, macroinvertebrates, plants, and sediments from July of 2014 from Pariette Wetlands, Utah, U.S.A. to test for spatial, temporal, plant species and plant tissue distribution of Selenium

Oxidation of Pentachlorophenol in Manganese Oxide Suspensions Under Controlled Eh and pH Environments

Abiotic oxidation of pentachlorophenol (PCP) by manganese(IV) oxide (MnO2) was examined in order to understand the physiochemical environment(s) where PCP oxidation occurs. An Eh−pH potentiostat was used to simulate natural groundwater environments where MnO2 (0.025 g L-1) and PCP (0.020 g L-1) suspensions were incubated from Eh −300 to 300 mV and pH 4.5 to 7.0. The pH−Eh region where maximum PCP sorption occurred corresponded to the same region where the greatest concentrations of soluble Mn(II) where measured (Eh \u3e −100 mV and pH \u3c5.0). Reduced Mn species [Mn(II,III)] released by reductive dissolution were readsorbed and restricted further abiotic oxidation of PCP by the MnO2 surface. A greater transformation of PCP to primarily tetrachloro-1,4-benzoquinone (p-chloranil) and smaller amounts of lesser chlorinated phenols occurred under increasing pH and Eh conditions

Controlled Environment Potentiostat to Study Solid-Aqueous Systems

We designed a redox apparatus that controls electropotenial (Eh), pH, and temperature. The apparatus is fully automated and can be assembled from equipment found in most soil analytical laboratories. The reactor can maintain environmental conditions used to evaluate the chemical fate of contaminants under natural conditions (natural attenuation) or adjust them to a new steady state to evaluate the effect of engineered remediation on a subsurface system. It can operate within a wide range of redox potential values (−400 to 400 mV) and at any pH value. The stability and accuracy of the instrument was tested by performing Eh-pH titrations on MnO2 suspensions. Results indicated that Eh could be controlled within 1 to 2 mV, pH within 0.05 to 0.1 unit, and temperature within 0.1°C for weeks or months