Research Project 1: Detailed inventory of contaminants (organics and trace
metals) in sediments in the Kalamazoo River watershed.
The primary analytical tools to be employed in these studies are an inductively
coupled argon plasma/mass spectrometer (ICP/MS) system for major and trace
elements and a gas chromatograph/mass spectrometer (GC/MS) system for organic
analyses. Both of these instrument systems have the advantage that multiple
elements or compounds may be quantified simultaneously on a single sample.
Repetitive analyses are not required. This means, in the case of the ICP-MS system,
that data on as many as 55 elements can be obtained for approximately the same
cost as only a few elements determined by atomic absorption spectrometry or
conventional ICP techniques. In addition, data can be obtained on multiple isotopes
of certain elements such as lead, beryllium or rare earths, and the information used
to understand various geochemical processes occurring in the plume during transport
and deposition, as well as during resuspension events. Table 1 lists a summary of
the analytes that are incorporated into the present study.
Table 1. Scope of Analyses
Number
65
13
16
55
Analyte
Pyrogenic & Petrogenic PAH
Herbicides
Chlorinated Pesticides
PCBs by chlorination group and 32 individual
congeners
Elements (including major, minor, trace and rare
earth)
Likewise, the use of multiple selected ion mass spectrometry on extracts of the three
phases of interest in this system will allow the quantification, at ppb levels, of several
classes of pollutants in a single analysis without extensive sample fractionation or
cleanup techniques. Thus, both pyrogenic and petrogenic PAHs, total hydrocarbons,
chlorinated pesticides, herbicides and PCBs, may be analyzed simultaneously. In
ongoing and completed studies of the fate and transport of contaminant plumes
under MMS, DOE and EPA funding, our research group has been able to use these
techniques to follow the chemical signature of a single discharge for up to 5 km and
has been able to describe transport processes over scales as large as the coastal
shelf of Northwestern Gulf of Mexico.
During the 2003 sampling season a series of sediment core samples were collected
in Allegan Lake (contaminated site) and Morrow Pond (relative control site) at sites
were surface grabs had been collected in 2001. In addition, cores samples were
collected in each of the other major impoundment regions of the river including
Trowbridge, Otsego, and Plainwell. In addition, samples were collected in regions
upstream of the Morrow Lake at Ft. Custer, and Ceresco. Figure 1 shows a map of
the watershed indicating the sampling sites. These samples were analyzed for the
full spectrum of analytes listed in Table 1. The intent of these analyses was to
establish a better picture of the overall contaminant load in Kalamazoo River water
shed sediments apart from the Superfund process that focuses exclusively upon PCB
contamination.
Figure 1. Map showing locations of sediment core samples collected
and analyzed during 2003-2004 grant period.
A major chemodynamics study was conducted in the Saugatuck Harbor region at the
mouth of the Kalamazoo River where it discharges into Lake Michigan (Figure 2).
This study involved the collection and analysis of samples sediment cores, suspended
sediment, colloidal phase and dissolved phase samples in May, July and September,
2003. These samples have been analyzed for the full spectrum of PAHs, PCBs
chlorinated pesticides as well as trace, minor and rare earth elements. These sample
collections were coordinated with the collection of hydrographic, water quality and
depth profiles to allow estimation of the discharge fluxes of each contaminant class
detected as a function of season and fraction (particulate, colloid-bound and truly
dissolved).
Figure 2. Detailed map of Saugatuck Harbor and near-shore discharge region of Lake
Michigan showing locations of hydrographic, water quality and contaminant samples.
A summary of one of these characterization and flux determination studies is
presented in the following several pages. The example presented is that for PAHs
discharging from Saugatuck Harbor into Lake Michigan.
We first examined the bedded sediments taken from the top 2CM of each core to
determine the distribution of PAHs (and other contaminants) in sediments that are
likely to be resuspended due to weather (storm) and anthropogenic (boating)
events. Figure 3 shows the distribution of parent (combustion source) PAHs. The
lowest concentrations are found in Kalamazoo Lake and the Lake Michigan
sediments, while intermediate and high levels are in the harbor channel and the
inner harbor regions.
Figure 3. Parent PAH concentrations in sediments from Saugatuck Harbor and Near-shore
Lake Michigan Receiving Waters. All concentrations are in ppb (ng/g) dry sediment.
Analyses of the alkylated polycyclic aromatic hydrocarbons in these same sediment
samples revealed that these petroleum source hydrocarbons were present at
significant levels relative to the ubiquitous combustion source hydrocarbons. Lower
concentrations were found in sediments to the south of the harbor channel discharge
and at some sandy sediment location in the channel, while moderate to high
concentrations were observed to the north of the harbor exit channel, in the channel
and at all locations within the harbor. Moderate concentrations were also observed
in Kalamazoo Lake upstream of the harbor.
The presence of these alkylated PAHs at concentration equal to and in some cases
higher than the parent PAHs suggests that there is an anthropogenic source for these
compounds, since this region is not associated with petroleum exploration,
extraction, or refining operations. The most likely source in this case is the chronic
discharge, leakage or disposal of petroleum products such as fuel oil. Another
possible source may be runoff from storm drains from the City of Saugatuck.
Figure 4. Alkylated PAH concentrations in sediments from Saugatuck Harbor and Near-shore
Lake Michigan Receiving Waters. All concentrations are in ppb (ng/g) dry sediment.
The molecular weight distribution of the alkylated PAHs in this case is primarily more
highly substituted naphthalenes and phenanthrenes. In cases where a mixture of
both parent and alkylated PAHs are present in samples it is useful to use indices to
determine the relative contribution of the combustion sources vs. the petroleum
sources that may be contributing to the overall contaminant load in a particular
watershed or region. The Fossil Fuel Pollution Index (FFPI) is on for the indices
commonly used to assess the relative contribution of the combustion sources vs. the
petroleum sources.
Figure 5 shows the FFPI values for the surface sediments in the Saugatuck Harbor
and near-shore regions of Lake Michigan. In this index, calculated from
concentrations of individual parent and alkylated groups, values near zero (0) are an
indication that the PAHs present are from combustion sources, while values
approaching 1.0 indicate that petroleum hydrocarbons dominate the PAHs present in
a sample. In the of the Saugatuck Harbor/Lake Michigan sediments analyzed here,
Almost all of the sediments have FFPI values which are at 0.4 or above and many
values exceed 0.6 indicating that the majority of the PAHs present are from
petroleum. This is true of samples throughout the harbor as well as the sediments in
Lake Michigan.
Figure 5. FFPI values for Sediment in Saugatuck Harbor and Near-shore Lake Michigan
Receiving Waters.