Progress 08/01/06 to 05/31/09
Outputs
OUTPUTS: The location and importance of nitrogen loading and associated nutrient limitation were studied in the Lower Truckee River across an urban gradient. The bioavailable fraction of wastewater and urban dissolved organic nitrogen (DON) was compared to "naturally derived" and downstream DON in the receiving river system using seasonal 67 day bioassays in 2007 and 2008. Wastewater derived DON consistently had a higher bioavailable fraction (20-51 percent) than "naturally derived" and downstream DON, usually a small fraction. Wastewater DON had a consistently recalcitrant fraction of DON (49-80 percent). During summer 2007, the fraction of bioavailable DON was similar for wastewater, natural, and downstream samples (40 , 41 , and 42 percent, respectively). Urban runoff DON had the highest degree of variation in bioavailability (3-70 percent). Wastewater DON loss was consistently fit with a biphasic exponential decay model (R spared equal 0.86-0.94) with lost DON converted into ammonium or particulate nitrogen. Periphyton nutrient limitation assays demonstrated variations in significant limitation (p 0.05) between seasons and sites with the most frequent limitation being N and P, followed by N, then N with a secondary P limitation. Across the urban gradient, a significant increase in baseline (control) periphyton growth was observed for spring, summer, and fall 2008 (p 0.05). A shift from co-limitation (N and P) to no limitation with concurrent increases in baseline periphyton production across the urban gradient occurred during three seasons which suggests that urban nutrient loads significantly affect this river system. PARTICIPANTS: Robert G. Qualls, Associate Professor. Neil Bertrando, graduate in 2008, this work constituted his M.S. Thesis Katie L. Dean, 2009 graduate, assisted in all aspect of the project. Mike brisbin, City of Sparks, collaborated on the the conception, proposal, data form the TMWRF, and logistics of the project. Community Foundation of Northern Nevada, funded the project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
This study coincides with current concerns regarding nutrient loads in river systems and highlights important techniques useful in monitoring and delineating the relative contributions of nitrogen and phosphorous from various sources. Several important considerations regarding DON in aquatic systems are highlighted by this study: 1) DON pools and their bioavailability vary seasonally, 2) bioavailability of DON can be modeled using a biphasic exponential decay curve when a labile fraction is present, 3) inputs of wastewater DON should carefully consider the ratio of bioavailable DON to recalcitrant DON which may vary seasonally and between individual treatment plants, and 4) inputs of bioavailable wastewater DON may not significantly alter the pool of bioavailable DON in the immediate receiving system depending on the scale of input and dilution. However, it is unwise to disregard impacts of total N loading into aquatic systems because the ultimate receiving bodies represent a sink for these loads. When residence times equal decades to centuries, recalcitrant compounds may be cycled into the available N pool. It is therefore necessary to elucidate sources of nutrient inputs along the entire watershed then consider them within a large-scale, combined perspective in order to develop both large and small-scale management and restoration strategies. The strategic placement of NDS bioassays along urban gradients in coordination with water quality sampling can provide critical insights into targets for source mitigation of anthropogenic impacts on lotic and associated lacustrine ecosystems.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: It has been suggested that implementation of the Clean Water Act might be further refined to recognize differences in biological availability of Nitrate-N, Ammonium-N, and Dissolved Organic-N (DON) in the regulation of Total Nitrogen (TN) Total Maximum Daily Loads (TMDL). This study was conducted to assess the location and importance of N loading and associated nutrient limitation in the Truckee River across the urban gradient. To refine understanding of nutrient loading effects, periphyton nutrient limitation assays were performed across the urban gradient. Since the variety of constituents in DON have not been thoroughly identified and may vary based on source and season, 67 day bioassays were performed to measure the fraction of DON that is mineralized or converted to particulate matter. Specifically, the bioavailable fraction of wastewater and urban DON was compared to "naturally derived" DON in the receiving river system. Seasonal bioassays in 2007 and 2008 demonstrated that wastewater derived DON consistently had a higher bioavailable fraction (20-51 %) than naturally derived DON (~0%). However during summer 2007 the fraction of bioavailable DON was similar for wastewater and natural sources (40 % and 41 %, respectively). DON derived from urban runoff had the highest degree of variation in bioavailability (3-70 %) as opposed to the more consistent bioavailability of wastewater DON or the summer pulse of bioavailblity in naturally derived DON . Downstream from the wastewater infall, the bioavailable fraction of DON varied seasonally (0-42 %). Periphyton nutrient limitation assays demonstrated variations in significant limitation (p<0.05) between seasons and sites: (1) upstream of the urban gradient during the summer 2007 (N) and spring-fall 2008 (N+P), (2) within the urban gradient during the spring (N,N+P), summer(N,N+P), and fall 2008 (N), (3) in the urban outfall during winter 2008 (N+P), and (4) downstream during spring 2008 (N+P). A significant increase in baseline (control) periphyton growth across the urban gradient was observed for spring, summer, and fall 2008 (p<0.05). It appears that wastewater DON consistently has a significant bioavailable fraction (20-51%) and a recalcitrant fraction (49-80%) which suggests TMDLs could be altered to regulate the bioavailable fraction of TN. In-stream DON bioavailability varies seasonally and across the urban gradient. The co-occurrence of N and N+P limitation and increases in baseline periphyton production during several seasons suggests that appropriate N TMDLs are important and that urban nutrient loads significantly affect this river system. PARTICIPANTS: Robert G. Qualls, Associate Professor Neil Bertrando, Graduate Student, (graduated Dec., 2008) Katie Dean, Graduate Student TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
It appears that wastewater DON consistently has a significant bioavailable fraction (20-51%) and a recalcitrant fraction (49-80%) which suggests TMDLs could be altered to regulate the bioavailable fraction of TN. In-stream DON bioavailability varies seasonally and across the urban gradient. The co-occurrence of N and N+P limitation and increases in baseline periphyton production during several seasons suggests that appropriate N TMDLs are important and that urban nutrient loads significantly affect this river system.
Publications
- Bertrando, N. (Presenter & Author), Qualls, R. G., Dean, K. L. (Author Only), Springer, M. (Author Only), Brisbin, M. (Author Only), AGU Fall Meeting, "Bioavailability of Dissolved Organic Nitrogen Originating From Natural Sources and Wastewater Effluent in the Truckee River", San Francisco, CA. (December 4, 2008).
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Recognition of the importance of nitrogen and phosphorus as pollutants lead to the implementation in 1994 of total maximum daily load standards for both total N and total P under the Clean Water Act. The watershed protection efforts are aimed at both point sources of N and P, such as the TMWRF and at non-point sources. The Truckee River TN Total Maximum Daily Load (TMDL) is 1,000 pounds per day (lbs/day) monitored at Lockwood below the effluent discharge. This standard includes all forms of nitrogen, nitrate, ammonia, and organic forms of N. It was recognized in the 1994 implementation, and subsequently (NDEP, 2005) that the TMDL might be further refined to recognize the differing effects of the biological availability of different forms of nitrogen. The current DON project being researched in the Qualls' Lab consists of two primary parts: a laboratory based biodegradation experiment and an in river nutrient limitation experiment. 1. DON Biodegradation experiment For the
first run of the biodegradation experiment, we inoculated filtered water sampled from the Truckee River above Reno (just downstream of Mogul), below TMWRF (past the mixing zone), at the mouth of the North Truckee Drain (Urban runoff), and directly from the TMWRF effluent faucet. The inoculant was collected from soil at sites along the river corridor and 100 uL was pipetted into 500 mL of sample. Samples were placed in UV transparent Teflon bottles and incubated at constant laboratory room temperature and exposed the samples to 4 hrs per day of simulated solar UV light per day at an intensity approximating 20% of the maximum UV-A and UV-B radiation at noon on a clear day at the summer equinox (Q-Lab Corp., UVA-340 lamps). We and collected 0.45 um filtered samples on days 0, 3, 7, 14, and 67. Each sample was analyzed for TDN, NH4, and NO2 + NO3. DON was then calculated from the difference between TDN and DIN. We also analyzed the initial and day 67 samples for particulate N. The data
suggest the levels of DON stayed constant (within statistical variability) for the above town site, while approximately 48 % of the DON in the effluent was degraded biologically (see Figure 1). The fate of the degraded DON was primarily an increase in [NH4] from ~50 ug/L to ~400 ug/L, but some was also accounted for by an increase in [Particulate N] of ~200 ug/L. These increases corresponds well to the ~550 ug/L decrease in [DON]. There was a similar exponential decrease in [DOC] observed for the effluent samples. The samples taken from the Truckee River just past the mixing zone showed a 20% decrease in [DON] at day 67, with the fate of the DON distributed between increases of particulate N and NO2+NO3. In addition, calculations of Truckee River flow rates and TMWRF daily discharge suggest that on the day the sample was taken the [DON] contributed to the river from TMWRF was ~35-45% of the total [DON] present past the mixing zone. Consequently, the decrease in DON was approximately
consistent with the decrease expected from a mixture of the effluent and Truckee River water.
PARTICIPANTS: Robert G. Qualls P.I. Mike Brisbin, TMWRA Neil Bertrando, graduate research assistant Katie Dean, undergraduate research assistant Michael Springer, undergraduate research assistant
TARGET AUDIENCES: Target audiences are other scientists engaged in analyzing the effectiveness of total maximum load regulalation, as well as State and local agencies responsible for deciding and carrying out TMDL regulations.
Impacts
2. Nutrient Limitation in the Truckee River The importance of TDN and DON availability to aquatic microbes is dependent upon whether microbial growth (algae in particular) in the river is limited by N, P, or the combination of N+P. To test nutrient limitation of periphyton growth in the Truckee River, we placed nutrient diffusing substrates (NDS) at four locations along the river. The locations were upstream of Reno (A: near Mogul), just past the S. McCarran Bridge (B), in the North Truckee Drain (C: just upstream from the mouth of the Drain), and downstream of TMWRF (D: near the weir for the Lockwood irrigation ditch). The nutrient enrichments tried were 0.5 M of inorganic N (a mixture of sodium nitrate and ammonium chloride, referred to as DIN), 0.5 M PO4-P, 0.5 M DIN + 0.5 M PO4, 0.5 M (as N) hydrolyzed amino acids, and a control with no nutrients. They were collected from the river after 21 days. The second round of NDS sampling was conducted in the late summer
using the 1M nutrient enrichments and collected after 8 days in the river due to the high levels of algae observed on the substrates. These data show a slight increase in periphyton growth due to nitrogen enrichment and a much larger increase due to N+P and amino acid enrichment for the Mogul. However, by the East McCarran Bridge, only a slight increase in growth was seen due to N+P enrichment and a large increase due to AA enrichment. We observed no enhanced growth over the control at the Truckee Drain site or downstream of TMWRF due to any of our enrichments (Figure 6). These data suggest that for the month of August phosphate alone is not limiting at any site and nitrogen alone was limiting at only the Mogul site. The drastic increase due to N+P enrichment at the Mogul site suggests that an N+P co-limitation occurs after moderate nitrogen enrichment. There may be a slight co-limitation occurring at the East McCarran Bridge site, but no limitation due to N, P, or N+P was observed at
the site downstream from TMWRF or in the North Truckee Drain where rates of algal growth were high even on the control substrates. Interestingly, growth due to amino acid enrichment was remarkably higher than any other treatment at both upstream sites. It is odd that this response was observed while inorganic N enrichments showed only a slight response or no response, at sites A and B respectively. These findings have prompted the city and state to reconsider TMDL limits to condier the bioavailability of DON.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
The objective of this project are: (1 ) to determine what fraction of the dissoloved organic N in Truckee River water, wastewater effluent, and urban runoff can be considererd as available for mineralization and subsequent algal uptake, and (2) what nutrients are limiting algal production in the river (inorganic N, inorganic P, N and P together, or amino-acids). This project is in the initial stages with the account being set up in late August. Two undergraduate assistants were hired and one graduate student was recruited to begin in January 2007. Sites were chosen evaluated in the field based on access, security, presence of riffles, and nutient background. Students were trained in optimizing the difficult analyses for organic N and initial samples were analyzed. a solar UV light simulator was purchased and constructed in the laboratory for exposure and incubation of samples under constant temperture. Apparatus for constructing in situ nutrient diffusing substrates
(to determine Objective 2) were purchased and constuction began.
Impacts
This work will be expected to be used to determine more refined water quality regulations for total maximum daily flows of nitrogen.
Publications
- No publications reported this period
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