Table 4.3. Heavy Metal Concentrations in Galveston Bay Sediments. 
Proposed EPA 
Bay Sediments (muds, ppm) 
Screening 
Buffalo Bayou/ 
Level 
Bay 
Houston Ship Channel 
Metal 
(ppm) 
mean 
high 
high 
Chromium (total) 
100 
55 
120 
150 
Copper 
50 
28 
130 
160 
Lead 
50 
34 
140 
260 
Nickel 
50 
26 
113 
Zinc 
75 
89 
275 
590 
Source: 1. 
the chemical form of the metal, other chemicals or chelating agents, and the redox potential of the 
sediment, will influence the amount of bioaccumulation that will occur. 
Local concentrations of chromium, copper, lead, nickel and zinc can exceed the proposed 
screening levels for dredged-sediment disposal established by the U.S. Environmental Protection 
Agency (Table 4.3). Abnormally high trace metal concentrations in sediments at many locations 
probably result from anthropogenic contributions. Highest concentrations were found in channel 
sediments, such as the Buffalo Bayou/Houston Ship Channel and Texas City Channel, where 
industrial and municipal discharges have been reported and widely publicized previously (1). A 
probable source of trace metals in Trinity Bay and East Bay is the Trinity River, where higher than 
normal levels of heavy metal particulates have been reported in river water. Simulated flow patterns 
indicate that predominate net flow is from Trinity Bay around Smith Point into East Bay during 
several months of the year. 
Other, less obvious, sources of contaminants also impact the bay. Copper, for example, is a potent 
algacide and one very soluble form in estuarine water can have an impact on the phytoplankton 
community. Copper and tributyltin are used in antifouling paints on ships, bulkheads and sub¬ 
merged structures. Tributyltin leaches from these paints and is so toxic to shellfish that Virginia, 
Maryland and several European countries have banned this compound. Concentrations in water as 
low as 1 part per trillion can adversely affect the reproductive cycle of oysters. Hundreds of fishermen 
and pleasure boaters on Galveston Bay are now painting their boats with the repellent. Oysters 
recently collected from four locations in Galveston Bay contained 120 to 1,000 parts per billion 
tributyltin. 
Hundreds of petroleum compounds (aliphatic and aromatic hydrocarbons) are discharged, 
dumped or spilled each day into the Galveston Bay system. These petroleum compounds vary in 
their toxicity to bottom-dwelling organisms and juvenile stages of shellfish and finfish. Generally, 
these compounds do not cause visible fish kills, but they are likely to induce liver damage and 
promote tumor growth in fish. There are more than 200 oil and gas wells in or near Galveston Bay 
that produce up to 8 barrels of saltwater for each barrel of oil. This wastewater (brine or produced 
water), discharged into the bay system, is heavily contaminated with water soluble fractions of oil 
as well as small droplets of crude oil. More than 1 million barrels of produced water are discharged 
per day. At the permitted level of 20 ppm oil, there is a minimum of 20 barrels of oil per day being 
discharged into the bay system. These oil droplets generally get bound to sediment particles in the 
water and settle into the sediment layer. Benthic organisms are excluded from these discharge points 
in all directions for up to 50 meters. Petroleum hydrocarbons can be accumulated by living organisms 
but biomagnification is rare. These hydrocarbons are known to be metabolized in the liver and form 
reactive intermediate compounds that are carcinogenic and also disrupt the mixed-function oxidase 
systems in vertebrates. Reduced production and survivability is the end result of chronic exposure 
to petroleum hydrocarbons. 
Sediments in many shellfish and finfish nursery areas also contain industrial contaminants, for 
example, petroleum waste hydrocarbons such as chlorinated phenols, chlorinated styrenes, phtha- 
late esters, and degreasing solvents. These chemical compounds are potent biocides, long-lasting in 
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