Calcium Enhancement in Downeast Area Rivers 03-04
Steve Kahl, Ken Johnson
The agencies responsible for recovery of Atlantic salmon are considering a project that would mitigate periods of low pH in one or more downeast salmon rivers in Maine. Low pH may be a factor that influences the survival of juvenile salmon. As part of this effort, the Mitchell Center at the University of Maine provided analysis, field support, and data assimilation and interpretation. This project accessed base flow and event water chemistry for three downeast Maine rivers, the Pleasant, Cathance, and Dennys, to determine if conditions exist that may affect salmon health. Sample collection concentrated on both base-flow and event sampling, and targeted areas with significant juvenile salmon habitat.
The two main objectives of this project focused on chemical conditions under the full range of hydrologic conditions for three Downeast rivers. The first objective was to quantify chemical concentrations in the Dennys, Cathance, and Pleasant rivers to determine which of the three was suitable for a chemical manipulation. The second objective was to identify the interaction between discharge and analyte concentrations, and between different analytes in large river systems.
List of Figures
Figure 1a: Map of Pleasant River Sample Sites
Figure 1b: Dennys and Cathance River Sample Sites
Figure 2: Graph of EqpH, ClpH, and ANC in the Dennys River
Figure 3: Graph of DOC Concentration on the Dennys River
Figure 4: Graph showing Dennys River discharge compared to Ca, EqpH, ANC and DOC
Figure 5: Graph of EqpH, DOC, and SO4 at the Dennys River
Figure 6: Graph Ca and Cl at Pleasant-Saco Falls and Pleasant-Columbia Falls
Figure 7: Graph of unfiltered-Al vs filtered-Al for two samples
Project Design and Summary of Field Season
The Pleasant, Cathance, and Dennys rivers were identified as sites with chemical conditions that may adversely affect salmon health. We chose upstream and downstream sites for each river, above and below a potential mitigation site, and analyzed samples from these sites throughout 2003-04. Sample sites were chosen based on the amount of salmon habitat and access considerations: Pleasant – Saco Falls, Pleasant – Columbia Falls, Cathance – Flume at Dodge Rd, Cathance – Lower site, Dennys – Robinsons Camps, Dennys – Lower site. After discussion with the Maine Atlantic Salmon Commission (ASC) the Dennys – Weir site was added to monitor water chemistry below the confluence of the Cathance and Dennys rivers (Figure 1a and Figure 1b). Grab samples were taken on two-week to one month intervals depending on season and hydrologic conditions starting in October of 2003. ISCO autosamplers were installed at the downstream site on each river and programmed to sample once per day at 16:00 as determined by an analysis of the USGS hydrographs for these rivers. The samplers hold 24 bottles, which reduced the risk of missing major events. Sampling was stopped in December 2003 due to ice and resumed on 3/3/04, when the ISCO on the Pleasant at Columbia Falls was moved upstream of the Addison Rd. bridge to prevent ice damage. Five ISCO samples were discarded from the Pleasant and Dennys (Table 1) from the November and December collections because data indicated the samples came from on top of the ice due to sample tube breakage (conductivities <8 µS/cm). During the period Oct 31, 2003 to Sept 30, 2004, 162 samples were collected and analyzed (90 grab and 72 ISCO samples from the seven sites).
ISCO samples discarded due to sample line breakage.
The sampling for this project is continuing, with major changes to the field sampling regime. The Denny’s River is now the sole candidate for pH alternation. Therefore, both Pleasant River sites were discontinued as well as the Cathance – Lower site. The Cathance ISCO will move to the Cathance – Flume at Dodge Rd. site and the Pleasant – Columbia Falls ISCO will be relocated to the Dennys or to another project. Sampling will continue at all three sites on the Dennys (Robinsons Camps, Lower site, Weir) with sample collection focusing on events and early snow melt.
Water samples were analyzed by the Mitchell Center Water and Watershed Laboratory for major cations (Ca, Mg, K, Na), anions (Cl, NO3, SO4), dissolved organic carbon (DOC), aluminum (Al) and exchangeable aluminum (Al-x), conductivity, acid-neutralizing capacity (ANC), air-equilibrated pH (EqpH), and closed-system pH (ClpH) (grab samples only). Analytical procedures were EPA methods used for 20 years by this team of investigators and the George Mitchell Center Laboratory (Morrison, 1989; Peck et al., 1993; Kahl and Webster, 1999). Aluminum analysis is being redeveloped due to instrument issues and is continuing for this project. Full aluminum analysis is expected by May, 2005.
Data for 162 samples are reported here for the analytes listed above. The original proposal called for 138 total samples, 78 grab and an estimated 60 ISCO samples. The samples from the Dennys – Weir site accounted for the extra 12 grab samples, at no additional cost to the funding agency. The proposed 60 ISCO samples was an estimate on precipitation for the year – 72 event samples is within the scope of this project. We also investigated the relationship between total-unfiltered-aluminum and total-dissolved-aluminum in a small value-added project, results of which are presented here.
Presentation of findings
Data collected to date have been presented to the Project SHARE, NOAA Fisheries, and the ASC in quarterly reports, in graphic form, and in a presentation at the 11-19-04 CEDAR meeting at the ASC office in Bangor, ME, as well as at other smaller meetings throughout the year. The complete dataset for CEDAR, minus aluminum, for the dates October 1, 2003 to September 30, 2004 is attached on paper and has been provided to the agency in electronic format. Data will continue to be delivered approximately quarterly. This report will serve as the final report for the first year funding cycle of the CEDAR project.
Upcoming Field Activities
Sample collection will continue with major changes in the sampling regime as noted above. Sampling will cease on the Pleasant River and the ISCO will be redeployed on the Dennys at a site and time to be determined. ISCO’s and batteries have been removed from the field for maintenance and will be re-deployed in the spring.
Results and Discussion
One primary objective of this research was to measure acidity related parameters through the yearly hydrologic cycle and report any patterns. Seasonal pH patterns were similar to Mitchell Center research on small streams, i.e. Bear Brook Watershed Maine (BBWM). The first CEDAR sampling fell on the tail end of a very large event in fall, 2003, with extreme flows, very high DOC (42.6 mg/L for the Pleasant), and diluted base-cations. Fall events are typical for this area and the chemical response is similar amongst all sites.
Summer flows are typically low resulting in a concentration of base-cations. Differences in ClpH and EqpH decreased in the summer as a result of increased ANC (Figure 2) and the conductivity increased for all three rivers from spring melt until the end of September. Winter and spring flow tends to be of lower ionic strength than other seasons. Closed cell pH (field pH) is often substantially depressed in winter because carbon dioxide is much more soluble at low temperature (Figure 2).
Pre-treatment Background Chemistry
Pre-treatment background chemistry confirms that these three downeast rivers are fairly dilute (<52 µS/cm) with low Ca (<4 mg/L) and prone to episodic acidification. Significant changes in water chemistry were noted with changes in discharge for all rivers, especially for DOC, which exhibits the largest change based on flow for all rivers (Figure 3). These data represent the range of chemical conditions in these rivers because of the good temporal coverage provided by the ISCO automated samplers. DOC tends to increase with flow, whereas some other constituents (Ca, EqpH, ANC) decrease with flow, presumably because of dilution (Figure 4). Sulfate concentrations do not appear to effect large changes in EqpH. DOC concentrations are inversely related to EqpH (Figure 5), suggesting that DOC influences EqpH more than SO4 in these systems. DOC is an indicator of organic acid concentrations, which contribute H+ to solution. Based on these results and prior work by this research team (Kahl et al., 1989) DOC appears to be a major control on EqpH.
The analyses from the upstream and downstream sites matched well for the Dennys and Cathance for all analytes indicating little change or contribution from tributaries between the sites. The Pleasant River – Saco Falls showed consistently lower base-cations (Ca, Mg, Na, K), concentrations (and subsequently lower ANC and pH values) and lower acid-anion (SO4, NO3, Cl) concentrations, than the Pleasant River – Columbia Falls site indicating a significant source of these analytes between the upper and lower sites (Figure 6). DOC values were not different between the Pleasant River sites. Between the two Pleasant River sites there are two road crossings (Cross Road, US Rt. 1), one railroad crossing (no longer active), 4 named tributaries (Little River, Flanders White Brook, West Little River, Coffin Brook), multiple unnamed tributaries, and large expanses of operating blueberry fields. These river crossings and tributaries may be the cause of the difference in chemistry between the two sites.
Filtered vs. Unfiltered Total Aluminum
Al analysis is normally divided into three fractions: total dissolved-Al, organically bound Al, and exchangeable (ionic Al or Al-x). Total dissolved Al is filtered in the lab through a 0.45 µm polycarbonate filter, acidified, and analyzed. Al-org (organically bound Al) samples are poured through a cation-exchange resin, acidified, and analyzed. Al-org is NOT filtered because the pressure differential in a vacuum filter would change the pH of the solution, re-speciating the Al. Al-x is the exchangeable or the biologically active form and is calculated by subtracting Al-org from total dissolved-Al. We measure filtered total Aluminum for two important reasons: 1) we have 20 years of record for comparison for trends and for reference to other sites; 2) Total filtered Al is the only truly defined and reproducible analysis of Al. All the other methods are operationally defined and subject to measurement errors that depend on the laboratory operator.
The GMC investigated the difference between filtered and unfiltered total-Al. We analyzed two samples for three species/separations: total unfiltered-Al, total dissolved-Al, and Al-x. We calculated Al-x in two ways; subtracting Al-org from the unfiltered (Unfiltered - Org) and by subtracting Al-org from total dissolved-Al (Diss-Org) (Figure 7). Total dissolved-Al is lower than either the unfiltered or the Al-org sample for both rivers, indicating that particulate Al that is filtered out prior to normal analysis is an important component of the total Al transported by the rivers. The difference between the unfiltered, filtered, and organically bound Al concentrations was less than 17 µg/L (ppb) for both samples, suggesting that nearly all the Al in the Dennys and Narraguagus rivers is bound to organic material. There is very little Al-x in these systems.
We recommend continued sampling on the Dennys River to further characterize the chemical characteristics prior to pH mitigation. The sampling should continue at all three sites for continuity and to determine the actual output to the estuary system. A site for pH mitigation should be finalized and the sampling scheme should be agreed upon so equipment and materials can be put in place for the next season. We also recommend continuing the sampling on the Cathance to track the contributions of this tributary to downstream chemistry in the Denny’s River.
Kahl, J.S., and K. Webster, 1999. Evaluating the effect of the Clean Air Act on lake and stream chemistry in the northeastern US. QA plan for EPA proposal for EMAP-SW long-term monitoring program.
Kahl, J.S., S.A. Norton, R.K. MacRae, T.A. Haines, and R.B. Davis, 1989. The influence of organic acidity on the chemistry of Maine surface waters. Water, Air, and Soil Pollution 46:221-234
Morrison, M, 1989. Quality Assurance Plan for the Long Term Monitoring Project. U.S. Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR.
Peck, D. V., M. Morrison, W. Mader, D. J. Chaloud (eds), 1993. Environmental Monitoring and Assessment Program: Integrated quality assurance project plan for the surface waters resource group. EPA 600/X-91/080, Rev. 1.01, June, 1993.