439490.fig.003
Figure 3: Data are from public published water quality reports from the Metropolitan Water District, Los Angeles, for sodium as a function of year. The concentration increased progressively after 2007 when industrial fluorosilicic acid with caustic soda injections began. Every 24 tons of fluorosilicic acid require 14 tons of sodium hydroxide to maintain pH at 8.4 (two H+ ions from H2SiF6 require two sodium ions). Sodium at 116 ppm has been found to decrease yields and affect vegetable and fruit quality. Sodium is released into the Colorado River by scores of industries lining the river. The EPA Salt Abatement Program limits releases from companies to one ton daily each, but the existence of numerous sites have led to this level. The EPA secondary standard for TDS (500 ppm) is exceeded but is not enforced—plants can tolerate natural TDS from 800 to 1000 ppm. No MCL has been developed by EPA for sodium, since fresh water has historically been low in sodium. Sodium is absent from pristine fresh drinking water, and the National average is 15 ppm. The Colorado River winds 700 miles from Western Wyoming to Southern California and the Mexico border. The speed of the river flowing at a typical width of 900 ft. is 4.5 ft/sec. with an estimated travel time of 9.5 days along its course. The source of fluoride along its length that produces the fluoride level of 0.2 ppm is presumably natural but has not been identified.