Introduction
There are various industrial
activities along the
Procedure
Collection of
Samples
Thirty five drainage sediment samples
were collected along
All drainage samples were collected within a 3 week period during February to March, 2003. The samples were wet sieved in the stream and only the coarse silt-fine sand size fraction was saved for analyses in small labeled bottles. The pH of the water was taken at each collection site. To obtain accurate locations of each sample site a GPS unit was used. The sample locations were plotted on maps using GIS.
Physical and
Chemical Preparation of the Samples and Chemical Analyses
The following procedures to prepare samples for chemical analyses are those used often in other researches;
All samples were taken to the lab and added to beakers containing double de-ionized water, swirled and the unwanted suspended finer sediment discarded to further purify the desired sediment fraction size. The samples were dried. A 1.000 gram portion of each sample was placed in a labeled centrifuge bottle to which 20 milliliters of acid was added. The acid was comprised of 3N nitric and 0.5 hydrochloric. The samples were placed in a hot shaker bath at 80 degrees C for 24 hours. The samples were then centrifuged and the aqueous portion of each was added to labeled analyses bottles.
Appropriate standards and a blank solution were prepared for chemical analysis. The ICP machine was programmed and the concentrations of each element in the study were ascertained.
Results
Click here to see a table representing the individual concentrations of all the elements in all the test and control samples. Also included is the pH of the stream water at each sample site. Significant concentrations at specific locations along the stream are shown in bold type.
Trend charts for the concentrations of
each element in the sediments along the stream course were prepared. The concentrations trends for Cu,
Pb, Zn, Cd, Ni and P are shown. Mean element concentrations in the
sediments of the Test and Control Samples are shown to the right of the trend
charts. The mean concentrations of Cu,
Pb, Zn, Cd, Ni and P are higher in the Test Samples (samples 19-1) than in the
Control Samples (samples 20-35). However, the mean concentration of P is only
slightly higher. The concentrations of all 6 elements peak at samples 18 and 19
and would seem to represent an area of higher industrial activity. Samples 18 and 19 were collected near the
confluence of the north and south branches of
Trend charts for the concentrations of As, Cr and Ag are shown. These elements do not show peaked concentrations at Samples 18-19 as those on Page 6. The mean concentrations of the Test and Control Samples for each metal are shown to the right of each trend chart. The concentration of As and Cr are slightly higher in the Test Samples as compared with the same in the Control Samples. The concentration of Ag is higher in the Control Samples because of the presence of 2 significant peaks.
Interesting element concentration peaks
in the sediments occur along the stream.
Near
The trends of element concentrations along
the stream could be affected by the variance of the pH of the stream
water. The pH values of the water along
According to the correlation coefficient tables there seems to be a high correlation between concentrations of Cu, Pb, Zn and Cd. An especially high correlation exists between Zn and Cd. The high correlations between the 4 elements are present in the Test and Control Samples. A reason for this dependency between the 4 elements could be that they share a common type of emission source in both the Test and Control Areas. As mentioned before activities of metal recycling and electrical and supply companies could be the emission source.
Element Concentrations in the Sediments of
This table compares
the element concentrations in this study with that of other local streams. The concentrations of the elements in
sediments from other streams were taken from studies by other researches.
The mean element concentrations in the drainage
sediments in the Test (downstream from
Toxic Concentrations or Preliminary
Remediation Goals (PRG)
The EPA has not established safe levels for elements in stream
sediments. However, they have done so
for soils. If the same PRG’s values for
elements in soils were applied to stream sediments, some of the concentrations
of elements in this study may be considered toxic or close to toxic. The PRG’s reported for As and Pb are 22 ppm
and 400 ppm, respectively. One lead
sample (
Conclusion
The drainage sediments in
A further extension of the research on
sediments in