Daily Archives: December 13, 2011

Klotzbach and Gray 2011: Qualitative Discussion of Atlantic Basin Seasonal Hurricane Activity for 2012

Summary is below.  Click here for full report and click here for news article.

 

 

 

CFact Press Briefing: Durban Climate Change Conference Press Briefing – Dec 7, 2011

Click here to view the Press Briefing presented by the Committee For A Constructive Tomorrow (CFact) at the Durban UN Climate conference.  This link is provided for information only and viewers may draw their own conclusions. (click here for prior post.)

Fram and Belitz 2011: Probability of Detecting Perchlorate under Natural Conditions in Deep Groundwater in California and the Southwestern United States

M.S. Fram and K. Belitz. Probability of Detecting Perchlorate under Natural Conditions in Deep Groundwater in California and the Southwestern United States. Environ Sci Technol. 2011 Jan 19.

Abstract: We use data from 1626 groundwater samples collected in California, primarily from public drinking water supply wells, to investigate the distribution of perchlorate in deep groundwater under natural conditions. The wells were sampled for the California Groundwater Ambient Monitoring and Assessment Priority Basin Project. We develop a logistic regression model for predicting probabilities of detecting perchlorate at concentrations greater than multiple threshold concentrations as a function of climate (represented by an aridity index) and potential anthropogenic contributions of perchlorate (quantified as an anthropogenic score, AS). AS is a composite categorical variable including terms for nitrate, pesticides, and volatile organic compounds. Incorporating water-quality parameters in AS permits identification of perturbation of natural occurrence patterns by flushing of natural perchlorate salts from unsaturated zones by irrigation recharge as well as addition of perchlorate from industrial and agricultural sources. The data and model results indicate low concentrations (0.1-0.5 μg/L) of perchlorate occur under natural conditions in groundwater across a wide range of climates, beyond the arid to semiarid climates in which they mostly have been previously reported. The probability of detecting perchlorate at concentrations greater than 0.1 μg/L under natural conditions ranges from 50-70% in semiarid to arid regions of California and the Southwestern United States to 5-15% in the wettest regions sampled (the Northern California coast). The probability of concentrations above 1 μg/L under natural conditions is low (generally <3%).

Click here to obtain the article (fee).