Entry_ID: (required) Entry_Title: Arsenic in Ground Water of the United States Group: Data_Set_Citation Originator(s): U.S. Geological Survey Title: Arsenic in Ground Water of the United States Publication_Date: 200212 Publication_Place: Reston, VA Publisher: National Atlas of the United States URL: End_Group Keyword: Geoscientific Information Keyword: Environment Group: Temporal_Coverage Start_date: 1973 Stop_date: 200111 End_Group Data_Set_Progress: Complete Group: Spatial_Coverage Southernmost_Latitude: 15 Northernmost_Latitude: 83 Westernmost_Longitude: 166 Easternmost_Longitude: -4 End_Group Location: North America Location: United States Location: Puerto Rico Location: Alabama Location: Alaska Location: Arizona Location: Arkansas Location: California Location: Colorado Location: Connecticut Location: Delaware Location: District of Columbia Location: Florida Location: Georgia Location: Idaho Location: Illinois Location: Indiana Location: Iowa Location: Kansas Location: Kentucky Location: Louisiana Location: Maine Location: Maryland Location: Massachusetts Location: Michigan Location: Minnesota Location: Mississippi Location: Missouri Location: Montana Location: Nebraska Location: Nevada Location: New Hampshire Location: New Jersey Location: New Mexico Location: New York Location: North Carolina Location: North Dakota Location: Ohio Location: Oklahoma Location: Oregon Location: Pennsylvania Location: Rhode Island Location: South Carolina Location: South Dakota Location: Tennessee Location: Texas Location: Utah Location: Vermont Location: Virginia Location: Washington Location: West Virginia Location: Wisconsin Location: Wyoming Group: Data_Resolution Latitude_Resolution: 1000.0 Longitude_Resolution: 1000.0 End_Group Access_Constraints: None. Use_Constraints: None. Acknowledgment of the National Atlas of the United States and (or) the U.S. Geological Survey would be appreciated in products derived from these data. Originating_Center: (required) Group: Data_Center Data_Center_Name: Earth Science Information Center, U.S. Geological Survey Group: Data_Center_Contact Last_name: Earth Science Information Center, U.S. Geological Survey First_name: N/A Phone: 1-888-ASK-USGS (1-888-275-8747) Phone: 703-648-5920 Group: Address 507 National Center Reston, VA 20192 USA End_Group End_Group End_Group Storage_Medium: RGB (24-bit) compressed TIFF format created using Arc/INFO 8.0.2. Group: Distribution Distribution_Media: online Distribution_Format : TIFF Fees: There is no charge for the map layer. End_Group Group: Reference End_Group Group: Summary This map layer is intended to provide national-scale, broad-brush answers to questions such as, "Where in the country might at least 25 percent of wells have high arsenic concentrations?" The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. The data should not be used to infer an arsenic concentration for an individual well. Although the data set shows that concentrations of arsenic are likely to be higher in certain geographic regions relative to others, there can be a high degree of local variability because of factors such as the well’s depth, the type of aquifer used by the well, and local geology and water chemistry. The only way to be certain of the arsenic concentration in the water supplied by any given well is to have the water tested. No responsibility is assumed by the U.S. Geological Survey in the use of these data. This image shows national-scale patterns of naturally occurring arsenic in potable ground-water resources of the continental United States. The image was generated from the most recent arsenic measurement available for each of 31,350 wells and springs across the United States. Over 20,000 of the water samples were collected by the U.S. Geological Survey between 1973 and 2001. The remainder of the samples were collected by State agencies and analyzed by comparable laboratory techniques. The data set shows a moving 75th percentile, which can also be described as the maximum arsenic concentration found in 75% of samples within a moving 50 km radius (the median size of a U.S. county). In other words, for any given 50-km-radius region in the data, lower concentrations of arsenic were found in 75% of sampled wells, while higher concentrations of arsenic were found in 25% of sampled wells. This is a revised version of the August 2002 map layer, with a corrected shoreline for Greenland. Some of the samples came from individual homeowner wells used, without treatment, for drinking water. Other samples came from wells supplying water for irrigation and other purposes. The data set does not include samples of saline or thermal water; all the samples represent aquifers used for drinking water supply, even if the specific well was not used to supply drinking water. The intent of this study was to describe the quality of the untreated ground-water resource itself, rather than to directly measure the quality of drinking water by monitoring water from taps and other "finished" water. Comparisons of these findings with those from previous drinking-water studies indicate that the concentrations reported here are comparable on a national scale to concentrations in untreated ground water tapped by water utilities across the Nation. These findings also reflect the quality of the ground-water tapped without treatment by homeowners and small community water systems. Arsenic concentrations are measured in units of micrograms per liter (ug/L), which is equivalent to parts per billion. The following table describes the display of the 75th percentile of arsenic concentrations in the GeoTIFF image: > Arsenic Color RGB values > Concentration >---------------------------------------------------------------- > 1 ug/L or less dark green 50.67328 150.3464 0.67328 > 3 ug/L light green 152 251 152 > 5 ug/L yellow 255 255 0 > 10 ug/L orange 255 165 0 > 50 ug/L or greater red 255 0 0 > Insufficient data white 255 255 255 > Non-US land grey 204 204 204 > Water light blue 132 193 255 > Further information on arsenic in ground water is available from the USGS Water Resources Discipline page about Arsenic in ground water in the United States, at . The associated world file is included as part of the GeoTIFF. The contents of the world file are: >1000.0000 >0.000000 >0.000000 >-1000.0000 >-6086629.0000 >4488761.0000 End_Group Group: Related_URL URL_Type: URL: Group: Description Originator: National Imagery and Mapping Agency Publication_Date: 1990 Title: World Vector Shoreline Publication_Information: Publication_Place: Bethesda, MD Publisher: National Imagery and Mapping Agency Online_Linkage: End_Group End_Group Group: DIF_Author Last_name: Rawson First_name: Peg Email: atlasmail@usgs.gov Phone: 703-648-4183 Group: Address 12201 Sunrise Valley Drive Reston, VA 20192 USA End_Group End_Group DIF_Revision_Date: 20050923 Science_Review_Date: