GEOS 3310 Lecture Notes: Water
Dr. T. Brikowski
ﬁle:waterQuality.tex,v (1.33, November 14, 2011), printed March 30, 2012
Water pollution is the “degradation of water quality
as measured by biological, chemical, or physical criteria.” Common sources of groundwater pollution are listed in Keller [Table 14.3, 2011]. Typical pollutants include:
• Oxygen-demanding waste: materials that produce a high
BOD [Fig. 11.2, Keller, 2000]
• Pathogens: disease-causing microorganisms
– often lead to eutrophication [Fig. 14.6a-c, Keller, 2011]. – see Gulf “Dead Zone” below and worldwide map of
reported dead zones
• Oil: e.g Exxon Valdez spill, BP Macondo Well blowout
• Toxic chemicals: organic compounds, heavy metals (e.g.
mercury), radioactive material
• Sediments: our greatest pollutant by volume
• Heat: cooling-tower water discharge can produce signiﬁcant environmental change, beneﬁcial if planned (e.g. Lake
Gulf of Mexico Dead Zone
The most severe nutrient pollution issue in U.S. is Gulf Coast “Dead Zone” (Fig. 1), with Chesapeake Bay a close second. • high nutrient loads in Mississippi River discharge ( USGS Circular ) lead to large algal blooms see NOAA animation)
• seasonal stratiﬁcation leads to hypoxia zone, killing marine life (Fig. 2) and Baltic images
• Gulf Dead Zone steadily growing , (see also LSU Current
• problem source
– this is an example of a distributed (“non-point”) source 4
– depends on land-use [Fig. 11.3, Keller, 2000]
– e.g. increased corn production for ethanol may cause larger dead zone, see CNN story )
• similar hypoxia from nitrate in groundwater in Cape Cod
• hurricanes can intermittently reduce dead zone area
re-aerating deeper waters
Gulf Dead Zone
Figure 1: Gulf of Mexico nitrate-generated “Dead Zone”, a byproduct of increased nitrate discharge from Mississippi River. Annually in summer this zone develops, and has been growing with time [Fig. 14.7, Keller, 2011].
Gulf Hypoxia Mechanism
Figure 2: Mechanism of formation of Gulf of Mexico “Dead
Zone”. After Louisiana Coastal Project . See also more
detailed depiction .
Increasing Nitrates to Gulf
Figure 3: Gulf of Mexico nitrate load vs. time [CENR, 2000, Fig. 2.4]. 8
Agricultural Nitrate Source
Nitrate load by sub-basin, Missippi River. “The principal sources of nitrate are river basins that drain
agricultural land in southern Minnesota, Iowa, Illinois, Indiana, and Ohio, where large amounts of nitrogen are applied to corn and soybean ﬁelds.” [CENR, 2000, Fig. 2.9]. See also USGS 1980-2008 summary .
Pollution Source Types
• two main categories of source:
– point: discrete and conﬁned, e.g. pipes or discharge from a single facility. Relatively easy to ﬁnd and control
– non-point: distributed, often cumulative eﬀects of runoﬀ from cities or farms. Harder to isolate and control.
• Reduction of pollution [Fig. 11.9, Keller, 2000]
– many initiatives, partly embodied in the Clean Water Act, have reduced point sources of pollution
– those laws inspired by severe cases like Cuyahoga River
ﬁres resulting from severe pollution
– most important has been the establishment of Maximum
Contaminant Levels for drinking water [Table 14.5, Keller,
– non-point sources are beginning to be controlled through widespread monitoring, e.g. all cities larger than 100,000
people must report storm-water quality (street runoﬀ)
– ultimately the most likely paths for movement of pollution into surface and groundwater must be identiﬁed and
controlled (Fig. 5)
Figure 5: Potential pathways for migration of pollutants into ground and surface water [Fig. 14.5, Keller, 2011].
• all island, most coastal and some inland aquifers have a lens of freshwater ﬂoating on seawater
Bibliography: Freese and Nichols, Inc. Region C Water Plan-2011. Regional Water Plan C, Texas
Water Development Board, Austin, TX, 2011
E. A. Keller. Environmental Geology. Prentice Hall, Upper Saddle River, NJ, 8th edition, 2000.
E. A. Keller. Introduction to Environmental Geology. Prentice Hall, 3rd edition, 2005.
E. A. Keller. Introduction to Environmental Geology. Prentice Hall, 4th edition, 2008.
E. A. Keller. Introduction to Environmental Geology. Prentice Hall, 5th edition, 2011.
from streams across the United States, 1998-2005. Scientiﬁc Investig. Rept. 2009-5109,
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