Research Project 2: Investigation of contaminant fate and transport

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Research Project 2: Investigation of contaminant fate and transport in the
Kalamazoo River
Understanding what controls the fate and transport of contaminants in aquatic
ecosystems is of substantial interest to researchers examining basic scientific
questions as well as scientists involved in pollution control evaluation and monitoring
of water quality for human health and ecotoxicity purposes. Various components of
the organic carbon pool have been shown to be an important link in controlling the
bioavailability of contaminants in natural waters (Figure 2). The aquatic organic
carbon pool can be viewed as having the following three constituents: particulate
(>0.20 um) (POC), truly dissolved (<0.2 um) (DOC), and high-molecular weight
DOC (<0.2 to > 1000 Da) (HMW DOC) or colloidal (Carlson et al., 1985; Santschi et
al., 1995) fractions. The HMW DOC (or colloidal) fractions of this carbon pool has
been shown to be particularly important in controlling the bioavailability of organic
(Means and Wijayaratne, 1982; Means and Wijayaratne, 1984; Brownawell and
Farrington, 1986; Lores et al., 1993; Burgess et al., 1996) and inorganic (Honeyman
and Santschi, 1989; Rees, 1991; Benoit et al., 1994; Moran et al., 1996; Stordal et
al., 1996; Wen et al., 1996a, b) contaminants in aquatic systems.
One of the fundamental questions in carbon cycling is the formation of different size
fractions of DOC, especially HMW DOC (i.e. > 1000 Da). While DOC in the open
ocean consists mostly of planktonic signatures from lipids, carbohydrates and
polysaccharides (Pakulski and Benner, 1994; Bianchi et al., 1995; Guo et al., 1994;
Guo and Santschi, 1996), lakes, continental margins and estuaries contain additional
sources of organic carbon from terrestrial systems such as rivers and wetlands (e.g.
Hedges and Parker, 1976; Hedges and Ertel, 1984; Moran et al., 1991; Bianchi et al.,
1996a, b).
Much of the research in DOC dynamics has centered in the "true" water column
without much regard to sediments playing a significant role in DOC cycling with the
water column (Burdige et al., 1992; Burdige and Homstead, 1994). Furthermore, it
has been suggested that DOC from sediment pore-waters may represent an
important source of organic carbon to the deep ocean (Williams and Druffel, 1987;
Mopper et al., 1991; Hedges, 1992). This is especially important in shallow systems
where DOC flux may equal allochthonous inputs of organic carbon into a system
(Argyrou et al., 1997). Several possible mechanisms may explain the formation of
HMW DOC via flux from sediments: 1) aggregation of truly dissolved particles onto
each other to form larger particles either by shear stress or bubbling action
(Honeyman and Santschi, 1989; Alber and Valiela, 1994a, b); and 2) break down of
particulate matter to form smaller particles either physically, chemically, or
biologically (Bianchi et al., 1996). Sediment mixing (via physical and biological
processes) is likely to be important in the formation of HMW DOC. The relative
importance of benthic macrofauna in the formation of HMW DOC in pore waters has
been largely ignored.
Figure 1. Regional Map showing the boundaries of the Kalamazoo and St. Joseph River
Watersheds.
Figure 2 Schematic of geochemical processes affecting contaminant partitioning in aquatic
environments
While there have been numerous studies that have examined the effects of HMW
DOC on the photoreduction of metal oxides, the speciation of metals, partitioning of
metals, and overall bioavailability of metals similar studies involving organic
contaminants have been sparse. Moreover, few studies have attempted to examine
both the effects of HMW DOC on ecotoxicity (organics and inorganics) as well as the
effects that test organisms may have on the chemical composition of HMW DOC. In
this study our objectives are as follows: determine the partitioning of PAHs in the
natural organic carbon pool (i.e., POC, DOC, and HMW DOC) in two highly polluted
aquatic systems - in both sediments and the water column; determine the effects of
benthic organisms on the molecular weight distribution of HMW DOC; examine the
effects of HMW DOC on the bioavailability of PAHs on benthic organisms.
In order to assess the fluxes of contaminants leaving the Saugatuck Harbor and
being discharged into Lake Michigan, a study which involved the collection of large
volume (20L) sample at several locations within the harbor and near-shore receiving
waters was undertaken in 2003 in May, July and September. Samples were
preserved in the field and returned to the laboratory where they were first filtered
(0.4mm Nuclepore) to remove particulates from the bulk water samples. Once this
was done the filtrate was transferred to a high volume Amicon ultra-filtration unit
where the colloidal size particles were isolated from the truly dissolved fraction.
Each of these three fractions was then prepared for analysis of organic and inorganic
contaminants using mass spectrometry methods. Figure 3 shows the stations where
these collections occurred.
Figure 3. Water Quality and Chemodynamic Study Sample Collection Sites.
In order to perform a detailed analysis of the fate and transport processes occurring
in this or any watershed a detailed survey of the bathymetry or depth profiling of the
waterway needs to be performed. In May of 2003, we conducted a detailed
bathymetric survey with the assistance of Drs. Guy Meadows and Lorelle Meadows
both from the University of Michigan. Figure 4 shows the depth profile developed for
the Saugatuck Harbor, Kalamazoo Lake and the channel leading into Lake Michigan.
In addition to this survey, a detailed bathymetric map (not shown) was developed
for the coastal Lake Michigan receiving waters covering an area of a few kilometers
off-shore and several kilometers to the north and south of the channel exit.
Figure 4. Bathymetric Survey data for Saugatuck Harbor, Kalamazoo
Lake and the exit channel into Lake Michigan.
The next step in the process was to determine the hydrodynamics in the Saugatuck
Harbor system so that the flow and volume of water exiting the river into Lake
Michigan can be determined at different seasons of the year. In order to gather this
information, GPS-equipped buoys with current drifters were deployed at different
location in the harbor system and followed as they moved through the system. Time
and location of each buoy is recorded automatically allowing for modeling of the
rates of water movement during each deployment. Figure 5 shows these buoys
deployed in the harbor. Figure 6 shows the trajectories of three buoy deployments
in Saugatuck Harbor and Figure 7 shows three buoy deployments in the exit channel
from the Harbor.
Figure 5. Current monitoring buoys deployed in Saugatuck Harbor.
Figure 6. Current buoy trajectories projected on map of Saugatuck Harbor
Figure 7. Current buoy trajectories projected on the exit channel fro Saugatuck Harbor into
Lake Michigan.
Drift Buoy
Buoy 1
Buoy 2
Buoy 3
Means
Discharge (m3/s)
May 2003
0.088
0.101
0.079
0.089
30.5
July 2003
0.028
0.033
0.020
0.027
10
Table 2 shows the buoy drifter velocities calculated for three deployments in
Saugatuck Harbor during May and July of 2003. From these data and the
Bathymetric survey data a volumetric measure of river discharge is calculated.
Chemical data determined for samples collected during the 2003 field campaign can
then be utilized to determine the fluxes of individual contaminants from the river into
Lake Michigan.
Table 4 and Table 4 show the concentrations parent and alkylated PAHs and total
PAH determined for suspended particulate fraction of selected water samples in May
and July of 2003, respectively. Figure 8 and 9 show the values of FFPI projected on
the station map of Saugatuck Harbor, the channel and near-shore Lake Michigan in
May and July, 2003, respectively. As was observed in the bedded sediment data
reported earlier, the proportion of alkylated aromatic hydrocarbons equaled or
exceeded the parent aromatic fraction and the FFPI values were mostly greater than
0.5. This observation was repeated in July, 2003. These results demonstrate that
petroleum source hydrocarbons a major contributor to the overall loading of aromatic
hydrocarbons to coastal Lake Michigan in the region of the discharge of the
Kalamazoo River.
Table 3. Aromatic Hydrocarbon Concentrations on Suspended Particulates
Collected in May 2003 in Saugatuck Harbor.
Station
TOTAL PARENT
PAH
ng/g
TOTAL ALKYLATED
PAH
ng/g
TOTAL
PAH
ng/g
FFPI
Saug 31
1220
3019
4240
0.765
Saug 32
3519
9020
12539
0.755
Saug 33
91195
147799
238994
0.669
Saug 34
25990
37478
63467
0.628
Saug 35
5606
9257
14863
0.328
Saug 36
17525
22242
39767
0.603
Saug 37
61963
83896
145859
0.563
Saug 38
20810
4092
24901
0.356
Saug 39
3945
6194
10139
0.699
Mean
25528
28957
54485
0.585
Minimum
578
1086
1665
Maximum
92687
147799
238994
Figure 8. FFPI Values for Suspended Particulates collected in May, 2003.
Table 4. Aromatic Hydrocarbon Concentrations on Suspended Particulates Collected in July
2003 in Saugatuck Harbor.
TOTAL
PARENT
PAH
TOTAL
ALKYLATED PAH
TOTAL
PAH
ng/g
ng/g
ng/g
Saug 31
235
547
782
0.745
Saug 32
89158
228495
317652
0.755
Saug 33
3869
5365
9234
0.460
Saug 34
2201
3762
5962
0.751
Saug 35
21864
36102
57966
0.693
Saug 36
8329
10570
18899
0.603
Saug 37
3790
9379
13170
0.765
Saug 38
14998
23263
38261
0.892
Saug 39
10570
16596
27166
0.699
Saug 40
5615
7498
13114
0.478
Mean
0.654
Station
6368
13133
19501
Minimum
192
547
782
Maximum
89158
228495
317652
FFPI
Figure 9. FFPI Values for Suspended Particulate Samples Collected in July, 2003
Combining the concentration data with volumetric data and hydrodynamic data
collected at this site fluxes of chemical contaminants were calculated for the
Saugatuck Harbor. Tables 5 and 6 show the fluxes calculated for parent, alkylated
and total PAHs in the Saugatuck Harbor system.
Table 5. Fluxes of PAH from Saugatuck Harbor into Lake Michigan-May, 2003
Flux,
g/hr
PARENT PAH
ALKYLATED
PAH
TOTAL
PAH
Saug 31
1.92
4.76
6.69
Saug 32
1.44
3.70
5.15
Saug 33
5.91
9.58
15.49
Saug 34
4.77
6.88
11.65
Saug 35
2.36
3.90
6.26
Saug 36
4.54
5.77
10.31
Saug 37
6.69
9.06
15.75
Saug 38
22.92
4.51
27.43
Saug 39
3.03
4.75
7.77
Table 6. Fluxes of PAH from Saugatuck Harbor into Lake Michigan-July, 2003
Flux,
g/hr
PARENT PAH
ALKYLATED
PAH
TOTAL PAH
Saug 31
1.18
0.82
1.18
Saug 32
63.39
162.46
225.85
Saug 33
2.03
2.82
4.85
Saug 34
1.33
2.27
3.61
Saug 35
2.07
3.42
5.49
Saug 36
1.51
1.92
3.44
Saug 37
0.64
1.59
2.23
Saug 38
0.73
1.13
1.86
Saug 39
1.01
1.58
2.59
Saug 40
9.76
13.03
22.79