Occurrence and Distribution of Ground Water Arsenic in Public Water - PowerPoint PPT Presentation

Occurrence and Distribution of Ground Water Arsenic in Public Water Supply Wells in Ohio Michael W. Slattery Christopher Kenah Division of Drinking and Ground Waters Program Development Unit

Acknowledgments Data : OEPA District Ambient Network Field Personnel OEPA District Drinking Water Field Personnel GIS Support : Brian Gara and Dick McClish of the DDAGW GIS Unit

Arsenic in Ohio’s PWS • Arsenic Rule driven by health concerns Reduction of MCL to 10 ug/L from 50 ug/L Understanding As provenance can help optimize reduction strategies • State-wide As appears widespread Analysis suggests that redox controls are more important than lithologic or stratigraphic controls Regional patterns do not support anthropogenic source

Data Sources • Ambient Monitoring Network 214 Wells, Untreated Water Single modern MDL = 2.0 ug/L Good (electronic) locational, geologic control • Public Water Supply Database 2922 PWSs, Treated Water Multiple MDLs = 2, 3, 5, 10 and 20 ug/L Poor (electronic) locational, geologic control

Mean Ambient and PWS As Concentrations S # # S S # # S S # # S S # S # S # # S S # S # # S S # S # # S # S # S # S S # S # S # S # S S # # S # S # # S # S S # # # S# S # S # # S S S S # S # # S # S S # # # S # # S S S S # S # S # # # # # S # # S S S S S S # S # # # S S # # S S # S # # # S S # # S # S S S S # # S # S # # # S S S # S # S # S S # # S # S # # S S # # S S # S S # S # # # S S S S # # S # S # S # S # # S # # S # # S S# S # S # S # S # S # # S S # # # S S S S # # S S # S # S # S # S # S # # S # S # S # S S # S S # S S # S # # S # S # # # S # S # S # S S # S # S S # # S # S # S # # S S # # S # # # S S # S # # S # S # S S # S # S # S S S # S # S S # S # # S S # S # # S # S # # # S # S S # S # S S S # S # # S # S # S # # # S S # S S # # S # S S # # S S # # S # S # # S Y # S # S # # S S # S # S # S S # S # S # S # # S S # S # S S # # S # S # S S # # S # S # # # S # S # S S S # # # S S # S # # S S # S # S S # S S # # S # S S # S # S # S # # S S # # S # # S # S # # S # S S S # S # S S # S # # S # # S S # S # S # S S # # S # S # S # S # # S S # S S # S # # S # S # # S # S # S S # # S S S # # S S # # S S # # S # S # S # S # S # # S # # # # S S # S S # S S S # S S # S # # # S # S # # S S # # S # S S # S S # # S # S S # # # # S # S# # # S# S # # # # # S # S S # S # S S S S # S S S # S # S # S # # # # S S S # # S S # # S # # # S # S # S S # # S # S S S S S S S # S # S # S S # S S S S # # # S S # S # # S S # # # # S # S # # S S # S # S # S S S # # S # S# # # S S # # S S S # S # S # S S # # S # # S S # S # # S # S # S S # # # S # S S S # S # S # # S # # S S # S # S S # S # S # S # # S # # S # S # S # S # # S S # S S # # S S # S S # # S S # # S # S S # S # Y # S S # # S # # S S S # # S # # S # S # S S # S S # # S S # # # S # # S S # # S # S S S # S # S S# # S # # S S # S S # # S # S S # # S # S # S # # S S # # S # S S # # S # S # S # S # # S # S # S # S # S S S S # # S # S S # S # # S S # S # S # # S # S # # S S # # S # # S S S # # S S S # S S # # S # S # S # S # # # # # # S S # S S S # S # S S # S S # S # S # # # S # S # S S S # S # # S S # # S # S # S # # S # S # S # # S # S S S S # S # # S # S # S # # # S # S S # S S # S # S # S # # S S # S S # # # S # # S S S # S # S # # S # S # S S S # S # S S # # # S # # # S S # # S S # S # S S # S # S # S # # S S # S # # S # S S # S # # S S # S S # # S S # S # # S # # S # # S S # S S # S # S # S S # # S # S # S # # S S # S # S # S # S # S # S # # S# # S S # # S # # S S S # S # S # S # # S # S S # # S # S S # S S # # S # S S # S # # # S S # S # # # Y # S S # S S S # S S # # # S S # S # # # S # S # S # S S # # S # # S S # S S S # # S S S # # # S S S S # # S # # # # S S # # S S S # # S S # S # S # S # # Y # # # S S # # S # S # S # # S S # S # Y S # S # S # # # S # S S S S S # # # S # S S # # S # S # S # # # S S S # S S # S # S # Y # Y S # # S S # # # S # S S # # S # S # S # S # S # # # S S # S # # S # S S S S S S # # S # S # S # S # # # S S # S S # S # S # S # # S # # S # S # S # S # S S # Y # # S S S # S S # S S # # S # # S # S # S # # S S # S S # S # S # S # S # S # # S # S S # # S S # # # S # S # # S # # S # # S # # # S # S # S S S S S # S # # S # # S S # S S S # # S # # S S # S S # S S # # S S # # S S # # S # # # S S S S S # S S # # S S # S # # S S # # # S # # # # # S # S S # S # S # S S # # S S # S S # Y S # S S # S # # S # # # # # S # S # S S S S # # # # S # S S # S S S # # S # # S # # S S # S S # # # Y # S S S # S S # S # S # S S # # S # # S # S # S # # S # S # S # # S S # S S S # S # # S S S S # # S S # # S # S # # S # # S # # S S S S S # S # # S # S # S # S # # S # S S # # S # # S S # # S S # S # S # S # # S # # S S S S S # S # S # # S S # # S S # S # # S # S # # # S S S S # S # # S # S # S # # # S S # # S S # S # S # S S S # S S # # S S # # S # S # # # S # S # S S S # # S # S S # # # S # S S # S # S S # # S # S S # # S S # S # S # # # S S # S # S # S S # # S # S # S # S # S # S # S # S S # S # S # # S # # S S # S # S S # N # S S # # S # # S S # S # S S # # # S S # S # # S S # S # # S S S # # S # S # # S S # S S # # S S # # S # S S # S # S # S # S # # S S # S # S # # S Mean Ambient and PWS # # S S # 20 0 20 40 Miles S # S # S S # As Concentrations (ug/L) 0 - 3 S # 3.1 - 5 # S Aquifer Type/Lithology 5.1 - 10 Sand and Gravel Aquifers # S Sandstone Aquifers 10.1 - 20 Ohio Environm ental # S Protection Agency Carbonate Aquifers 20.1 - 91 # Y Div ision of Drinking and Ground Waters Program Dev elopment Unit Car tography by: Michael Slattery Interbedded Shale and Carbonates

Histogram of Mean Ambient Arsenic Concentrations 2 N = 214 sites Proposed MCL = 5 g/L 10 2.0 9 8 7 6 5 4 3 Counts 2 10 1.0 9 8 7 6 5 4 3 2 10 0.0 0 8 16 24 32 40 48 56 64 72 Average As concentration ( g/L

Mean As Concentration by Lithology Ambient Monitoring Network 9 8 7 Current MCL = 50 g/L 6 5 4 Arsenic Concentration ( g/L) 3 New MCL = 10 g/L 2 10 1 8 7 6 5 4 3 2 (31) (43) (114) 10 0 median = 2.16 median = 2.00 median = 2.95 Carbonates Sandstones Sand and Gravel

Histogram of Mean PWS Arsenic Concentrations, 1980-1999 7 6 N = 2922 PWSs 5 4 5 g/L 3 10 g/L 2 Historical Detection Limits 10 2.0 9 3 g/L 7 20 g/L 6 Counts 5 4 3 2 10 1.0 9 7 6 5 4 3 2 10 0.0 0 4 8 12 16 20 24 28 32 Average As concentration ( g/L

Mean PWS As concentrations, 1980-1999 100 8 7 6 5 Current 4 MCL = 50 ug/L 3 2 10 8 Proposed As ( µg/L) 7 MCL = 10 ug/L 6 5 4 current 3 detection limit = 2 ug/L 2 1 Mean: 7.23 8 7 Median: 6.09 6 5 Max: 90.11 4 Std Dev.: 5.1 (2922)

Histogram of Mean PWS Arsenic Concentrations, 1996-1999 2 N = 2175 PWSs 5 g/L 10 3.0 8 6 Historical Detection Limits 5 4 3 2 3 g/L Counts 10 2.0 8 6 5 4 3 2 10 1.0 8 6 5 4 3 2 10 0.0 0 4 8 12 16 20 24 28 32 Average As concentration ( g/L

Mean PWS As concentrations, 1996-1999 100 8 7 6 5 4 Current 3 MCL = 50 ug/L 2 10 8 Proposed 7 MCL = 10 ug/L 6 5 As ( µg/L) 4 3 current detection limit = 2 ug/L 2 1 8 7 6 5 Mean: 5.59 4 Median: 5.00 3 Max: 90.34 2 Std Dev.: 4.56 (2175)

Mean Arsenic in Ohio PWSs as a function of PWS Type and Number of Service Connections 10 2 7 6 5 Mean Total Arsenic Concentration ( g/L) 4 3 proposed As MCL = 10 g/L 2 10 1 7 6 5 4 3 2 10 0 7 6 Community PWSs 5 4 Transient PWSs Non-Community NT PWSs 2 3 4 5 67 2 3 4 5 67 2 3 4 5 67 2 3 4 5 67 2 3 4 5 67 10 0 10 1 10 2 10 3 10 4 Number of Service Connections