Metadata: Identification_Information: Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: 200212 Title: Arsenic in Ground Water of the United States Publication_Information: Publication_Place: Reston, VA Publisher: National Atlas of the United States Online_Linkage: Description: Abstract: 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. Purpose: 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. Supplemental_Information: 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 Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 1973 Ending_Date: 200111 Currentness_Reference: Ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: 166 East_Bounding_Coordinate: -4 North_Bounding_Coordinate: 83 South_Bounding_Coordinate: 15 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: Geoscientific Information Theme_Keyword: Environment Theme: Theme_Keyword_Thesaurus: None Theme_Keyword: Arsenic Theme_Keyword: Water Theme_Keyword: Ground water Theme_Keyword: Groundwater Theme_Keyword: Well Theme_Keyword: Drinking water Theme_Keyword: Environment Theme_Keyword: Water quality Place: Place_Keyword_Thesaurus: None Place_Keyword: North America Place_Keyword: United States Place_Keyword: Puerto Rico Place_Keyword: Alabama Place_Keyword: Alaska Place_Keyword: Arizona Place_Keyword: Arkansas Place_Keyword: California Place_Keyword: Colorado Place_Keyword: Connecticut Place_Keyword: Delaware Place_Keyword: District of Columbia Place_Keyword: Florida Place_Keyword: Georgia Place_Keyword: Idaho Place_Keyword: Illinois Place_Keyword: Indiana Place_Keyword: Iowa Place_Keyword: Kansas Place_Keyword: Kentucky Place_Keyword: Louisiana Place_Keyword: Maine Place_Keyword: Maryland Place_Keyword: Massachusetts Place_Keyword: Michigan Place_Keyword: Minnesota Place_Keyword: Mississippi Place_Keyword: Missouri Place_Keyword: Montana Place_Keyword: Nebraska Place_Keyword: Nevada Place_Keyword: New Hampshire Place_Keyword: New Jersey Place_Keyword: New Mexico Place_Keyword: New York Place_Keyword: North Carolina Place_Keyword: North Dakota Place_Keyword: Ohio Place_Keyword: Oklahoma Place_Keyword: Oregon Place_Keyword: Pennsylvania Place_Keyword: Rhode Island Place_Keyword: South Carolina Place_Keyword: South Dakota Place_Keyword: Tennessee Place_Keyword: Texas Place_Keyword: Utah Place_Keyword: Vermont Place_Keyword: Virginia Place_Keyword: Washington Place_Keyword: West Virginia Place_Keyword: Wisconsin Place_Keyword: Wyoming 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. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: National Water-Quality Assessment Program, U.S. Geological Survey Contact_Address: Address_Type: Mailing address Address: 12201 Sunrise Valley Drive, MS-413 City: Reston State_or_Province: VA Postal_Code: 20192 Country: USA Contact_Voice_Telephone: 703-648-5716 Contact_Electronic_Mail_Address: nawqa_whq@usgs.gov Data_Set_Credit: This image incorporates field data collected by the U.S. Geological Survey, the Maine Department of Health, the Massachusetts Department of Environmental Protection, the Minnesota Pollution Control Agency, the New Hampshire Department of Environmental Services, the Rhode Island Department of Health, the Texas Water Development Board, and the Wisconsin Department of Natural Resources. Native_Data_Set_Environment: RGB (24-bit) compressed TIFF format created using Arc/INFO 8.0.2. Data_Quality_Information: Logical_Consistency_Report: No tests for logical consistency have been performed on this map layer. The data samples were collected from a variety of agencies over a span of 28 years, but were all processed with comparable laboratory techniques. Completeness_Report: This map layer includes arsenic measurements from ground water in 49 States and Puerto Rico. Arsenic data were not available for the Hawaiian Islands. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Ryker, S.J. Publication_Date: 2001 Title: Mapping arsenic in ground water Series_Information: Series_Name: Geotimes Newsmagazine of the Earth Sciences Issue_Identification: v. 46, no. 11, p. 34-36 Publication_Information: Publication_Place: Richmond, VA Publisher: American Geological Institute Type_of_Source_Media: Journal article Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2002 Source_Currentness_Reference: Publication date Source_Citation_Abbreviation: USARSENIC Source_Contribution: National distribution of arsenic concentrations in ground water. Source_Information: Source_Citation: Citation_Information: Originator: USDA Forest Service Originator: U.S. Geological Survey Publication_Date: 200205 Title: Forest Cover Types Publication_Information: Publication_Place: Reston, VA Publisher: National Atlas of the United States Type_of_Source_Media: Online Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 2000 Source_Currentness_Reference: Publication date Source_Citation_Abbreviation: Atlas-FCT Source_Contribution: Background and shoreline. Source_Information: Source_Citation: Citation_Information: Originator: U.S. Geological Survey Publication_Date: 200208 Title: Arsenic in Ground Water of the United States Publication_Information: Publication_Place: Reston, VA Publisher: National Atlas of the United States Type_of_Source_Media: Online Source_Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 1973 Ending_Date: 200111 Source_Currentness_Reference: Ground condition Source_Citation_Abbreviation: Atlas-AR200208 Source_Contribution: Spatial and attribute information. Source_Information: Source_Citation: Citation_Information: 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: Type_of_Source_Media: Online Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 1990 Source_Currentness_Reference: Publication date Source_Citation_Abbreviation: WVS Source_Contribution: Shoreline information. Process_Step: Process_Description: A detailed description of how this map layer was created, and discussion on interpreting the map layer, may be found in USARSENIC. Information on sources is included under Data Set Credit, above. The area of the United States was divided into a grid using equal-area hexagons 100 kilometers across (the median size of a U.S. county). For areas with a minimum data density of five wells per hexagon, the 75th percentile of arsenic concentration was computed. A moving 75th percentile was then approximated by "smoothing" across hexagon boundaries based on neighboring values. Source_Used_Citation_Abbreviation: USARSENIC Process_Date: 2001 Process_Step: Process_Description: The map layer was projected to a Lambert Azimuthal Equal Area projection, merged with the background information from Atlas- FCT, and converted to a GeoTIFF image. Source_Used_Citation_Abbreviation: USARSENIC Source_Used_Citation_Abbreviation: Atlas-FCT Process_Date: 2002 Source_Produced_Citation_Abbreviation: Atlas-AR200208 Process_Step: Process_Description: The coastline of Greenland was replaced by a new, corrected version derived from World Vector Shoreline (WVS). This image contains no thematic data for Greenland; the new data were inserted only to maintain consistency with other National Atlas data layers. Source_Used_Citation_Abbreviation: Atlas-AR200208 Source_Used_Citation_Abbreviation: WVS Process_Date: 200212 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Grid Cell Row_Count: 7273 Column_Count: 10366 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Lambert Azimuthal Equal Area Lambert_Azimuthal_Equal_Area: Longitude_of_Projection_Center: -100.00 Latitude_of_Projection_Center: 45.00 False_Easting: 0.0 False_Northing: 0.0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: Row and column Coordinate_Representation: Abscissa_Resolution: 1000.0 Ordinate_Resolution: 1000.0 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: None Ellipsoid_Name: Sphere Semi-major_Axis: 6370997.0 Denominator_of_Flattening_Ratio: 1.0 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: Arsenic concentration grid cell Entity_Type_Definition: Any of the grid cell elements in the arsenic concentration raster file. Entity_Type_Definition_Source: U.S. Geological Survey Attribute: Attribute_Label: Arsenic concentration grid cell value. Attribute_Definition: Each grid cell value is a color definition that represents an estimate of the 75th percentile of arsenic concentration in that region. The concentrations were recorded in micrograms per liter (ug/L; equivalent to parts per billion), and were converted to colors according to the following table. All arsenic concentrations greater than 50 micrograms per liter were recoded as 50 micrograms per liter. There may be intermediate colors in the image that are not included in this table. > 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 > Attribute_Definition_Source: U.S. Geological Survey Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: 0 Range_Domain_Maximum: 255 Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: Earth Science Information Center, U.S. Geological Survey Contact_Address: Address_Type: Mailing address Address: 507 National Center City: Reston State_or_Province: VA Postal_Code: 20192 Country: USA Contact_Voice_Telephone: 1-888-ASK-USGS (1-888-275-8747) Contact_Voice_Telephone: 703-648-5920 Contact_Instructions: In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at . Distribution_Liability: Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey in the use of these data. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: TIFF Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: Fees: There is no charge for the map layer. Metadata_Reference_Information: Metadata_Date: 20050923 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Peg Rawson Contact_Address: Address_Type: Mailing address Address: 12201 Sunrise Valley Drive Address: MS-561 City: Reston State_or_Province: VA Postal_Code: 20192 Country: USA Contact_Voice_Telephone: 703-648-4183 Contact_Electronic_Mail_Address: atlasmail@usgs.gov Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Security_Information: Metadata_Security_Classification_System: None Metadata_Security_Classification: Unclassified Metadata_Security_Handling_Description: None