1. METAL CONTAMINATION OF SEDIMENTS Cd, Pb AND Zn IN AURORA, MISSOURI
Amanda Bybee; Advisor: Dr. Melida Gutiérrez
Geology, Missouri State University, Springfield MO
ABSTRACT
Aurora is a historic mining town in the Tri-state Mining District.
Mining in the Tri-state district began in 1885 and ended by 1930.
Mining waste (chat) was disposed in-piles for the most part.
Remediation started in the area early in 2001, which continued
through 2006. Metals (lead, zinc, cadmium) present in those piles
might have reached sediments, posing a risk to water quality.
This study will use fluvial surface sediment samples to plot
current conditions of metal contaminants in the area and their
distribution using ArcMap, followed by comparing them with the
location where chat piles used to be. The sediment samples were
allowed to air dry, disaggregated then sieved with 2 mm and 1
mm sieves. The samples were then analyzed for metals in a
commercial lab.
There are seventy-nine sediment samples with the following
metal concentrations: cadmium with concentrations from 1.20 to
281.0 ppm with a median of 32.8 ppm, lead with concentrations
from 42.0 to 8200 ppm with a median of 196.0 ppm, zinc with
concentrations from 120.0 to 20400 ppm with a median of 3040
ppm.
We compared sediment metal concentration data with stream
sediment quality guidelines, to assess the possible threat to the
health of the aquatic systems. The sediment quality guidelines for
cadmium is values less than 4.98 have no effect, less than 10.0
have some effect and more than 10.0 found to be toxic. The
sediment quality guidelines for lead is values less than 128 have
no effect, less than 250 have some effect and more than 250
found to be toxic. The sediment quality guidelines for zinc is
values less than 458 have no effect, less than 821 have some
effect and more than 821 found to be toxic. Our maps show the
locations where the metal content exceeded these guidelines.
Table 1 Cadmium, Lead and Zinc are still present in a
wide range of values with a median of 32.8, 196 and
3040 respectively. The median for Cadmium and Zinc
far exceed probable effect concentrations with severe
effects set by MacDonald. (MacDonald, 2009)
MINERALIZATION
SEDIMENTS QUALITY GUIDELINES
Sediment guidelines are necessary because of the impact on
organisms directly and indirectly through the food chain.
Sediments hold a memory of current and historic toxicity of the
water. The toxic metal levels can affect the health of organisms in
many ways including survival, growth, and reproduction.
Sediment quality guidelines have been established for the Tri-
State Mining district (MacDonald, 2009).
There is a range of toxicity levels with each contaminant.
MacDonald reported guidelines for the Tri-State Mining district
for this range for several species. These metals include cadmium,
copper, lead, nickel and zinc. The criteria for each level of toxicity
is “<20% incidence of toxicity below the toxicity threshold, >50%
incidence of toxicity above the toxicity threshold, and >80% of
the samples correctly classified as toxic and not toxic”
(MacDonald, 2009). Cadmium values less than 4.98 have no
effect, less than 10.0 have some effect and more than 10.0 found
to be toxic. Lead values less than 128 have no effect, less than
250 have some effect and more than 250 found to be toxic. Zinc
values less than 458 have no effect, less than 821 have some
effect and more than 821 found to be toxic.
RESULTS
3
CONCLUSIONS
Mining in the area ended by
1930 and remediation ended
in 2006. Even though more
than 8 years have passed since
remediation finished metal
levels in area stream
sediments continue to affect
the stream quality and are
potentially toxic to aquatic life
and the food chain.
WATERSHEDS
REF ERENCES
GeoSTRAT – Geosciences Technical Resource Assessment Tool. Retrieved February 15, 2015, from http://dnr.mo.gov/geology/geostrat.htm
Gutierrez, M, Wu S, Peebles J. Geochemical mapping of Pb- and Zn-contaminated streambed sediments in southwest Missouri, USA, In review.
MacDonald, 2009, Development and Evaluation of Sediment and Pore-Water Toxicity Thresholds to Support Sediment Quality Assessments in the Tri-State
Mining District (TSMD), Missouri, Oklahoma, and Kansas.
Trimble JC, 2001, Spatial patterns and floodplain contributions of mining-related contaminants in Chat Creek watershed, southwest Missouri, M.S. Thesis,
Missouri State University, Springfield, MO
PICHER, OK
AURORA AREA MINING SITES
AURORA AREA AFTER REMEDIATION
Effects on Organisms (in ppm)
No
effect
Some
effect
# of Samples
above some effect/
# of Samples
tested
Severe
effect
Cd <4.98 >4.98 35/44 >10.0
Pb <128 >128 59/79 >250
Zn <458 >458 77/79 >821
Methods
The sediments were collected from the surface down 3 inches
below the surface. The samples were collected with a spade
and contained within plastic bags approximately 4 hours, until
we were able to get them back to the lab. Samples were
immediately put on wax paper to air dry. Rocks and organic
material like leaves were removed. Dried samples were then
disaggregated with a mortar & pestle then sifted with a 2mm
sieve then 1mm sieve. Samples were then sent to ALS USA
where they were analyzed using standard procedure of acid
digestion (aqua regia) and ICP-MS. I then plotted the
concentrations for Cadmium, Lead, and Zinc using ArcGIS.
SAMPLING IN CHAT CREEK
1
10
100
1000
10000
100000
Cd Pb Zn
ZINC
CADMIUM
LEAD
N=79
N=44
N=79
Gutierrez, Wu, Peebles
No effect
Some effect
Severe effect
No effect
Some effect
Severe effect
No effect
Some effect
Severe effect