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Central Indiana Water Resource Partnership
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Research Description and Methods A. Reservoir Surface Sediment Characterization Sampling Strategy and Field Methods Surficial sediments were collected throughout Eagle Creek, Geist, and Morse Reservoirs to describe the distribution and composition of sediments and the distribution of trace and minor elements and nutrients associated with the sediments. Samples were taken along transects throughout the main portions of the reservoirs, in inlets, and channels. Ninety surface sediment grab samples were collected in Eagle Creek Reservoir in September 2002 (Fig. VI-1). Fifty-one samples were collected in Geist Reservoir in March 2003 (Fig.VI-2). Samples will be collected in Morse Reservoir in spring 2003. Sample sites were located using a Global Positioning System (GPS) which provided location coordinates typically with accuracies of better than one meter. These coordinates were used to plot samples and results on all subsequent maps. Sample localities were also field located using bathymetric charts and aerial photographs. Surficial sediment samples were collected using a dredge consisting of a combination of two cut, stainless steel vessels bolted together, weighted, and coated with clear-coat epoxy enamel. Surficial sediments correspond to approximately the upper 5-10 cm of sediment and represent approximately the past 5-10 years of reservoir history. These are estimates that will be verified by determination of sediment accumulation rates in later planned studies. Samples were transferred to either 50 ml polypropylene centrifuge tubes for chemical analyses or plastic bags for grain size analysis. All samples were labeled, sealed, and stored at 4oC, transported to the laboratory, and stored under refrigeration until sample analyses.
Laboratory Methods Particle Size Analysis Particle size analysis was run on ~90 rservoir-bottom sediment samples from Eagle Creek Reservoir. Samples were freeze-dried at -40 degrees for 24 hours then disaggregated through a 2000 micron screen. Organic materials (leaves, twigs, roots) were picked out at this time. The remaining material >2000 microns was weighed and stored. A one-gram representative fraction of the <2000 micron fraction was then taken from each sample and boiled in 5 mL H2O2 (hydrogen peroxide, 32-35%) to remove organic matter. This H2O2 bath was repeated 3 times for each sample and upon completion, 8 mL MgCl (25g/L) was added to each sample. The sediment was then wet sieved through a 125 micron sieve to separate out any remaining organic pieces. The >125 micron fraction was recombined with the sample and then funneled into a 600 mL beaker with 500 mL water and left to settle for 24 hours. Water was then siphoned off, the sediment funneled into 50mL centrifuge tubes and centrifuged for 15 minutes. After centrifuging, the water was poured off and 20mL of the dispersant, sodium metaphosphate (2.5g/L) was added to each. Particle sizes were determined using a Mastersizer 2000 laser particle size analyzer by Malvern Instruments. Each sample was measured three times and these values were averaged. The data generated by the Malvern are reported as volume percentages of the analyzed fraction. Organic Matter Determinations Organic matter determinations were done on a Loss on Ignition (LOI) basis. This is the standard technique for sediments with organic matter contents above about 0.5 wt%. For this study, an accurately-weighed, dried (105°C overnight) sample mass (about 1 g) was weighed into dried and preweighed porcelain crucibles. The crucibles were ashed in a muffle furnace at 550°C for approximately 2.5 hours, cooled, and reweighed. The loss in sample mass is due to the incineration of organic matter, and thus the organic matter content, in weight percent, is a measure of the initial sample mass minus the residual mineral sample mass divided by the initial mass. To convert to percent organic carbon, a multiplicative of 0.4 can be used. Typical reproducibility in the organic matter measurement process is about 2%, with the main variables causing this error being sample dryness and analytical weighing errors. Phosphorus and Metals The biolimiting nutrient phosphorus (P) and the other geochemical parameters were measured by the same process. A standard EPA protocol (EPA SW3051) was used involving strong acid digestion (2N HCl, warm, for 24 hours) after sample ashing. The ashed residues from the organic matter determinations were used for this procedure, transferring the residues (typically between 0.8 and 0.99 g) into new 50 mL HDPE crucibles, then adding 40 mL of trace metal grade HCl diluted to 2N with Milli-Q (ultrapure) water. After capping tightly, the vessels were warmed and shaken for 24 hours, after which the vessels were centrifuged and stored for analysis. Geochemical analysis was performed on a Leeman Labs PS950 Sequential Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) fitted with a CETAC AT5000+ ultrasonic nebulization system for improved detection limits. For this analysis, approximately 0.2 mL of extractant from the digestion procedure was diluted 1:20 with acidified Milli-Q water and analyzed by ICP-AES, with typical analytical reproducibility of 0.5-2%, depending mainly on the initial elemental concentration. Care was taken to ensure that no elemental interferences (spectral) occurred, and the results (in ppm solution) were back-calculated to solid concentrations (also in ppm) taking into account sample dilution, extractant volume, and initial sample mass. Detection limits for sediment nutrient and metal analyses are given with the results in Section VII (Tables VII-3 and VII-5). B. Watershed Contribution to Reservoirs: Characterization of Suspended and Dissolved Sediment Loads Sampling Strategy and Field Methods In an effort to characterize the contribution of inputs to the three central Indiana reservoirs from their watersheds (Fig VI-3), we are documenting the watershed contribution of suspended sediment, dissolved and sediment-associated components. Samples are being collected quarterly from tributaries of Eagle Creek, Fall Creek, and Cicero Creek Watersheds following a regional rainfall event and during a non-event period. This will allow for the characterization of both base flow and storm flow (runoff) loadings from the watershed. Water sample collection began in winter 2003 and is ongoing. In each of the three watersheds, water was sampled from select stream segments. The main stream in each of the watersheds was sampled at several locations from near the head water to near the reservoir inlets with locations selected relative to subwatershed boundaries. In addition, other sampling locations were selected to assess contributions from major tributaries to Fall, Eagle, and Cicero Creeks. Sample stations were established in each watershed with eight stations in Eagle Creek Watershed (Fig. VI-4), nine stations in Fall Creek Watershed (Fig. VI-5), and six stations in Cicero Creek Watershed (Fig. VI-6). Sampling for dissolved and suspended sediments was conducted during low flow where the estimated discharge was approximately equal to the mean monthly discharge for the season. Suspended sediments were also sampled during high stream flow. High stream flow conditions were estimated to exceed three times the mean flow for the season. Stream
discharge was measured at the same time that water samples were
collected. Discharge was measured using a SONTEKTM
digital flow meter. A calibrated rope was stretched across the
stream channel and used to measure width of the stream channel and
for determining the number of stations to measure discharge. The
number of stations used for measuring discharge varied depending on
stream width. The stations were distributed such that no more that
5% of the discharge was measured at each station. At each station,
the flow measurement was made at 0.6 depth and discharge was
calculated by summing the flow for the station interval and
determining an averaged flow for the stream. Streamflow was also
measured at locations near USGS gauging stations when possible. The
locations of USGS gauge station are shown in Figures VI-4, VI-5, and
VI-6.
For each sampling location, water was sampled near the middle of the stream, or at a location within the stream segment representative of the averaged flow conditions. Physical water quality parameters including temperature, pH, dissolved oxygen (DO), specific conductance (SpC), and total dissolved solids (TDS) were measured in the field using a Hydrolab™ multi-parameter probe. Surface water grab samples were collected approximately 0.25 m below the water surface, and in most cases, upstream from the nearest bridge crossing. Water for suspended sediment characterization was collected in three 1-L HDPE containers. Water for dissolved water chemistry and other parameters measured by USFilter Indianapolis Water laboratories was collected in a suite of sample containers provided by USFilter. Laboratory Methods Nutrients, Major Ion, and Biological Analysis - USFilter Indianapolis Water Laboratories All water chemistry with the exception of isotopic analysis was analyzed by USFilter Indianapolis Water laboratories. CEES performed analysis of dissolved inorganic carbon (DIC), d13C, and d18O. Once collected and delivered to the labs, a portion of the water remained unfiltered and was chemically analyzed for alkalinity, TOC, TKN, and total phosphorus. The remaining water was filtered through 0.45 μm membrane filters to effectively separate suspended sediments from dissolved components in the water. Chemical analysis performed on filtered water included DOC, inorganic anions (Cl-, SO4, NO2, NO3, OrthoPO4), total hardness, inorganic cations (Na, Ca, Mg, K, NH3), and total phosphorus. Biological analysis of the water was performed on unfiltered water and included total coliform, E. coli, heterotrophic plate count (HPC), and chlorophyll a. Standard lab procedures were followed for each analysis and a list of the methods used along with the detection limits are shown in Table VI-1.
Suspended Sediment Analysis EPA Method 160.2 was used to separate particulates from dissolved constituents in water samples. A well mixed water sample was collected in one liter HDPE, acid cleaned bottles and refrigerated. The bottle was agitated, rinsed with milli-Q water, and the sample volume recorded using a graduated cylinder. The water sample was then filtered through a pre-weighed 0.45micron glass filter. The graduated cylinder, funnel wall, and filter were rinsed with three portions of milli-Q water. The filter was then carefully removed from filter support, placed on a watch glass and dried overnight in a 105oC oven. The sample was cooled in a desiccator and weighed. The mass of suspended sediments was determined and normalized to the volume of water filtered. The geochemical characteristics of these suspended sediments will be analyzed using the same protocols as for the surficial sediments from the reservoirs. The only potential differences is that due to small samples size, the filter may need to be processed along with the sample to maximize the total sample mass for analysis. Stable Isotopes Water for oxygen isotopic (d18O) analyses was collected and stored in leak proof 25 ml scintillation vials with inverted cone closures. For dissolved inorganic carbon (DIC) and carbon isotopic analysis, 10 ml of filtered water was collected using a syringe and injected into a pre-evacuated septum tube preloaded with phosphoric acid and a magnetic stir bar. For stable oxygen analyses, 2 mL of water sample was equilibrated with 0.5 atm CO2 at 25 0C (Socki et al., 1992). The equilibrated CO2 was extracted under vacuum and analyzed for d18O by mass spectrometry. Stable carbon was measured by extracting CO2 in the septum tubes using a modification of the gas evolution extraction technique (Atekwana and Krishnamurthy, 1998). CO2 yields from water samples were used to determine DIC concentrations and are reported in mg C/L. Stable isotope measurements (d 18O and d13C) were made using an isotope ratio mass spectrometer at Western Michigan University, Kalamazoo, MI. The isotope ratios are reported in the d notation: d (0/00) = ((Rsample / Rstandard) -1) x 103 Where R is 18O /16O or 13C/12C. The d values are reported relative to the VSMOW for oxygen and relative to VPDB for carbon. Routine d18O and d13C measurements have an overall precision of better than 0.10/00. C. Water Chemistry and Water Quality in Reservoirs Sampling Strategy and Field Methods Water quality and water characteristics are being measured in Eagle Creek, Geist, and Morse Reservoirs to document water chemistry and overall water quality. Sampling locations span the reservoir, inlets, coves, and outflow points in each reservoir. A select set of stations include samples taken along depth profiles. Depth profiles are designed to provide a snapshot of the physical and chemical conditions within the reservoir on a basin-wide scale. The information will be used to plan long-term water quality monitoring programs and is an important first step in understanding reservoir dynamics and further delineating research questions. At the time of the writing of this report, detailed water quality and water sampling was done over a five day period from September 13 to17, 2002 in Eagle Creek Reservoir (Fig. VI-7). In March 2003, physical water quality parameters were measured at 50 stations in Geist Reservoir (Fig. VI-8), but samples for water chemistry have not yet been collected.
Depth discrete sampling was conducted in Eagle Creek Reservoir for stations with water depth of more than 2 m. Near surface samples at each sampling location were measured and collected at a depth of about 0.25 m, while depth sampling was done at intervals that varied. Stations deeper than 2 m were sampled at 3m, 6m, and 9m depth or 50 cm above the sediment surface. Integrated water samples were collected in Eagle Creek Reservoir at each sampling location at each sampling location with a depth profile. Samples were obtained by inserting a ¾” by 10’ PVC schedule 40 conduit pipe into the water. A corded stopper was attached to the end of the pipe to achieve a true vertical section. The stopper created a suction to hold the water in the pipe as it was pulled up and released into a bucket for grab samples to be collected. These integrated water samples were then later analyzed in the lab for the same chemical parameters as the other water samples, as well as MIB and Geosmin. For each reservoir sampling site, physical water quality parameters including water temperature, pH, dissolved oxygen, specific conductance, and total dissolved solids were measured using a HydroLabÔ multiparameter probe. The probe was lowered to the desired water depth in the water column reservoir. Readings for the different parameters were recorded after stabilization. Secchi depth was also measured at each sampling station. Water was collected at discrete depths using a 2 L Wildco depth sampler (Wildco Instruments, Saginaw Michigan). Surface water grab samples were collected approximately 0.25 m below the water surface. For sampling locations upstream and downstream of the reservoir, water was sampled near the middle of the selected stream segment. Laboratory Methods Nutrients, Major Ion, and Biological Analysis - USFilter Indianapolis Water Laboratories All water chemistry with the exception of isotopic analysis was analyzed by USFilter Indianapolis Water laboratories. CEES performed analysis of dissolved inorganic carbon (DIC), d13C, and d18O. Water analyzed for major ions and nutrients were collected in 250 mL HDPE bottles and cooled to 4°C on ice. The samples were transported to the USFilter Indianapolis Water Laboratory where they were stored at 4°C until analyses. Once the Eagle Creek Reservoir samples were collected and delivered to the USFilter labs, chemical analysis was performed for alkalinity, inorganic anions (Cl-, SO4, NO2, NO3, OrthoPO4), inorganic cations (Na, Ca, Mg, K, NH3), total hardness, MIB. and Geosmin. Water collected for stable isotope analysis was filtered in the field and collected in pre-evacuated septum tubes to be analyzed later in the CEES hydrology lab. Standard lab procedures were followed for each analysis and a list of the methods used along with the detection limits are shown in Table VI-1. Water chemistry and water quality analyses for Geist and Morse Reservoirs will include alkalinity, TOC, TKN, and total phosphorus on unfiltered samples. The remaining water will be filtered analyses will include DOC, inorganic anions (Cl-, SO4, NO2, NO3, OrthoPO4), total hardness, inorganic cations (Na, Ca, Mg, K, NH3), and total phosphorus. Biological analysis of unfiltered water will include total coliform, E. coli, heterotrophic plate count (HPC), and chlorophyll a. Standard lab procedures will be followed for each analysis and a list of the methods used along with the detection limits are shown in Table VI-1. Stable isotopes Sampling and laboratory analyses for dissolved inorganic carbon and stable isotopes is the same as described for watershed sampling above.
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