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Transcript of Contamination and other issues Source Point sources Point sources Non-point sources Non-point...
Contamination and other issues
Source Point sources Non-point sources Naturally occurring
Reactions (chemical and biological) Transport
Potential sources of contamination
Point sources
Fuel storage tanks
Landfill
Septic tank Leaking
tank in gas station
Truck fuel spill
Dry cleaner
Factory wells, spills, emissions
Households
Non-Point sources
Naturally occurring
FarmBrought by river
Brought from outside area by groundwater
• Cannot be traced to a specific spot
• Multiple sources
• Large area
• Source activities related either to land or water use
• Examples• water runoff from urban areas• construction sites• agricultural• failing septic tanks• improper animal-keeping practices• Improper forestry practices
Non-Point source pollution
How Does Groundwater Contamination Move?
Can be filtered if flows slowly, like through sands
With groundwater down water table
Not filtered if flows rapidly, like in
limestone caves
17.10.a
http://techalive.mtu.edu/meec/module04/ContaminationMovement.htm
• LNAPL - Light Non-Aqueous Phase Liquids • lighter than water• generally petroleum
NAPL - Non-Aqueous Phase Liquids
http://toxics.usgs.gov/definitions/lnapls.html
• DNAPL - Dense Non-Aqueous Phase Liquids• denser than water• chlorinated compounds • PAHs
http://water.usgs.gov/ogw/karst/kigconference/wjw_preliminaryconcept.htm
(from USGS WRIR 02-4105)
Arsenic in groundwater
Depends on rock type (sulfide minerals) Oxidation state pH Presence of Fe
Arsenic accumulation over time
Tiles on cement block
Increased coating on tiles with time
Arsenic Accumulation on Tiles
0
0.5
1
1.5
2
2.5
3
3.5
4
PC-1 PC-1a PC-2 PC-2a PC-3 PC-3a Portis Portis2
Sample Location
As:
ppb/s
q c
mFirst Quarter
Second Quarter
Third Quarter
http://portal.ncdenr.org/c/document_library/get_file?uuid=34d44ecd-33f1-41a7-9cc7-164389e7de5e&groupId=38364
Bottom:Reducing
Top:Oxidizing
Arsenic accumulation
10 cm
Reid, Haven, Eudy, Milosh, Stafford, 2007, Arsenic in Groundwater Investigations – Eastern Slate Belt (ESB): Nash and Halifax Counties, North Carolina
Source: DENR “North Carolina State of the Environment Report 2011”
2010 State-Wide Private Well Sampling Results
Nitrate pH Arsenic Chromium Iron ManganeseState Groundwater Standard
10 mg/L
6.5-8.5
10 ug/L 10 ug/L 300 ug/L 50 ug/L
Number of samples4,110 4,901 4,870 4,892 4,896 4,900
Percent of samples exceeding standard
0.7% 18.4% below pH
of 6.5
2.4% 1.5% 57.6% 39.9%
NC population 10,000,000½ drink groundwater
2/4% of 5,000,000 people is 120,000 people
Arsenic Probability from Private Well Data (Pippin, 2005)
Probability of a groundwater sample exceeding 0.001 mg/L
0.2 1
Pippin, 2005, Arsenic Occurrence in the Unconfined Fractured Bedrock Aquifer System of the North Carolina Piedmont
Arsenic Probability from Private Well Data (Pippin, 2005)
Probability of a groundwater sample exceeding 0.001 mg/L
0.2 1
Carolina Slate BeltKings Mountain Belt
Charlotte Belt Inner Piedmont Belt
Eastern Slate Belt
Probability of a groundwater sample exceeding 0.001 mg/L
0.2 1
Data Source: USGS Estimated Use of Water in the United States County-Level Data for 2010, http://water.usgs.gov/watuse/data/2010/. Accessed February 11, 2015
0 60 12030Miles
4Legend
Population (in thousands)
1.32 - 20.3
20.3 - 41.8
41.8 - 80.3
80.3 - 147
147 - 276
Population Using Self-Supplied Groundwater
Data Source: USGS Estimated Use of Water in the United States County-Level Data for 2010, http://water.usgs.gov/watuse/data/2010/. Accessed February 11, 2015
0 60 12030Miles
4Legend
Population (in thousands)
1.32 - 20.3
20.3 - 41.8
41.8 - 80.3
80.3 - 147
147 - 276
Population Using Self-Supplied Groundwater
USGS Estimated Use of Water in the US County-Level Data for 2010
Population using private wells
Take-aways
It’s easier to keep groundwater clean than to clean up contamination
Groundwater – Surface Water all one thing Understanding the geology is critical to Public
Health Not all contamination is caused by humans Well construction is different under certain
geologic conditions
Take-aways
Test your well! Learn what to test for – • Depends on geology• Land use practices• History of land use• Contamination events
Porosity and permeability - https://www.youtube.com/watch?v=zrewtz42GmgThe space between the grains - https://www.youtube.com/watch?v=tt-mx25t7rA“best extreme caving video” - https://www.youtube.com/watch?v=TucYTJe1WsAMammoth Cave, Kentucky - https://www.youtube.com/watch?v=fTNlZl7-s4wGeology of Mammoth Cave - https://www.youtube.com/watch?v=VFLDvzc5P2kGroundwater – good, but long - https://www.youtube.com/watch?v=ci-ABWPG7LQWish we had this for eastern NC - https://www.youtube.com/watch?v=Z2HQY5A3o-s
How Do We Depict the Water Table?
Contour: water table at same elevation; blue arrows show flow
Numbers show elevations of the water table: what is the pattern?
Compare water table to other features
17.07.b
Amy Keyworth
919-807-6460
NCDENR Division of Water Resources
Division of Water Resources