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United States Department of Agriculture (USDA) 2007

PHOTOCHEMICAL TRANSFORMATION REACTIONS ON DESERT SOIL SURFACES

Desert Soil

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)

Titre : PHOTOCHEMICAL TRANSFORMATION REACTIONS ON DESERT SOIL SURFACES

Identification : NEV052SD

Pays : Etats Unis

Durée : Aug 1, 2007 à Nov 30, 2008

Domaine : soil/sand ; nitrate ; perchlorate ; titanium dioxide ; photocatalystic reactions

Partenaire : UNIVERSITY OF NEVADA RENO,NV 89557

Objectifs
This project seeks to investigate the factors that affect semiconductor photocatalyzed reactions and how these processes affect formation and loss of perchlorate and nitrite. This will be done through three specific aims. 1) Investigate the extent of nitrate and perchlorate photogeneration on TiO2 and desert soil surfaces. 2)Determine the photocatalytic formation mechanisms of nitrite and perchlorate. 3) Examine various factors which quantitatively affect the photocatalysis rate on desert sand, including organic content, water content, length of exposure, grain size distribution, titanium and metal oxides contents.

Descriptif
Various locations in Nevada and California will be selected for soil/san sampling. Samples of 1 kg each will be obtained from the top 2 cm and initially analyzed for NO3-N and CIO4. Sands will be further characterized for grain size distribution, organic content, extractable metals and x-ray diffraction for surface minerals and oxides identification. For aim 1, suspensions of the anatase form containing 4, 8 and 16 gm of TiO2 will be evenly distributed on Petri dishes to form thin and inform layers of TiO2. 15 grams of sand will be placed in Petri dishes, spread evenly and covered with borosilicate covers and exposed to UV irradiation and sunlight similar to the suspensions. For aim 2, intermediate will be added to the Petri dishes from aim 1 after irradiation. The Petri dishes will also receive known concentrations of chloride, hypochlorite, chlorite, chlorate and perchlorate. For aim 3, we will examine their proposed role of chloride in the photocatalytic reactions of both nitrite and perchlorate, establish relationships between the formation mechanisms of both, and correlate their vertical concentrations in the top 1m of the soil column.

Présentation : USDA

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