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Summary A detailed local-scale monitoring network was used to assess CFC distribution in an unconfined sand aquifer in southwestern Ontario where the zone of 1–5-year-old groundwater was known with certainty because of prior use of a bromide tracer. Groundwater ⩽5 years old was confined to an aerobic zone at ⩽5 m depth and had CFC concentrations consistent with modern atmospheric mixing ratios at recharge temperatures of 7–11 °C, as was observed in the 3-m thick vadose zone at the site. At depths below 6 m, the groundwater became progressively more reducing, however, with a denitrifying horizon at 6–7 m depth, and a Mn and Fe reducing zone below 7 m depth. In the anaerobic zone, 3H/3He ratios indicated that groundwater-age...
Socio-economic data by county subdivision in Vermont, New Hampshire and Maine. Includes population density, median age, education levels, vacation homes, incomes, poverty, unemployment, employment in key sectors.
Studies conducted since the late 1970s have estimated the net energy value (NEV) of corn ethanol. However, variations in data and assumptions used among the studies have resulted in a wide range of estimates. This study identifies the factors causing this wide variation and develops a more consistent estimate. We conclude that the NEV of corn ethanol has been rising over time due to technological advances in ethanol conversion and increased efficiency in farm production. We show that corn ethanol is energy efficient as indicated by an energy output:input ratio of 1.34.
This data set includes U.S. Census Bureau 1990 population information for the United States, presented by county. Included are total population counts; various statistics on race, ethnic, and gender distributions; income statistics; urban and rural statistics, and median age. This is a revised version of the July, 2004, data set, with data for urban and rural statistics added.

map background search result map search result map U.S. Census Database, 1990 Socio-economic data by county subdivision Socio-economic data by county subdivision U.S. Census Database, 1990