Dendrochemistry of Gadolinium in Effluent Dependent Waterways of Arizona

1. Title: Spatial and Temporal VariabillityVariability of Clogging on Stream-Aquifer Interaction in the UpperSanta CruzValley

2 . Project Summary

In water-limited environments, effluent is an increasingly viable water source for riparian restoration and aquifer recharge. Based on results from an existing TRIF supported project we have been able to document that effluent is an important component of the groundwater resources in the system, that clogging does occur and influence both surface and sub surface processes and that the impact of clogging varies over time. In extending this previous research we seek to document the importance of effluent and clogging to the riparian vegetation of the system and gain some insight into the variability of clogging and effluents influence in time and space. Our research will focus on the UpperSanta CruzRiver where effluent aids in maintaining safe-yield conditions in the Santa Cruz AMA (SCAMA). In the current study we seek to determine influence of effluent quality on vegetation, use that influence to demonstrate the lateral extent of effluents influence on trees and estimate the temporal and spatial influence of clogging on recharge rates through the stream bed of the Santa Cruz. We will do so by addressing three questions. First, how effectively are contaminants in the effluent transferred into tree tissue? Second, how does the influence of effluent on vegetation vary with distance from the river? Third, what is the spatial and temporal variability of streambed clogging and recharge within the Santa CruzRiver?

3. Duration: July 2008 – July 2009

4. Principle Investigators:

Tom Meixner, Assoc. Prof., Dept. HWR, 520.626.1532

Paul Sheppard, Assoc. Prof. Tree-Ring Laboratory, 4

5. TRIF Funds Requested:

6. Leverage (matching) funds pledged:

7. State of critical regional or state water problems:

In arid and semi-arid regions, effluent has great potential as an additional water source that can support riparian vegetation, augment aquifer recharge, and sustain perennial surface flow in otherwise ephemeral streams. Additionally the chemical composition of effluent can have an impact on the health of ecosystems and humans through acute and chronic toxicity effects, alterations of ecosystems processes and through biologically induced clogging which can alter

8. Statement of Results or Benefits

Through the proposed research, we hope to document the processes and patterns that influence the effects that effluent dominated rivers can have on their surrounding ecosystems. We will do so in a way that will provide knowledge of how both the quantity and quality aspects of effluent affect ecosystem processes. Our study will document the influence of the space and time variability of clogging on recharge rates and thus water sustainability and water resource availability in the Santa Cruz AMA. Additionally the information we gain on the influence of effluent quality on the chemical composition of tree rings will indicate how effluent moves through ecosystems and the spatial and temporal extent of its influence on drinking water sources as well as the sources of water preserving the ecosystems of the Santa Cruz valley. Furthermore, given the knowledge gaps that exist in understanding the functioning of effluent-dominated streams, this research will provide the foundation for a larger interdisciplinary research initiative addressing the dynamics of riparian ecohydrology.

Part II

1. Nature, Scope, and Objectives of the Research

Effluent dominated rivers are a critical and growing resource in the desert southwest of the United States (ref). In fact in Arizona, Phoenix, Tucson and Nogales/Santa Cruz County all have significant wet river reaches that are dominated by effluent (ref). Often these effluent river reaches are critical ecosystem resources for wildlife and humans and thus are increasingly utilized to provide certain biodiversity and aesthetic ecosystem services to society. Additionally effluent dependant rivers also recharge local and regional groundwater systems (ref). For these reasons it is critical to understand the biological and hydrological processes occurring in effluent dependant dependent rivers and how that might influence aquifer recharge and stream ecosystem biota.

The Water Sustainability program funded a TRIF proposal in the 2007-2008cycle that supported a project directed by Tom Meixner on “Stream Aquifer Interactions in Effluent Dominated Riparian Systems”. This research has produced useful knowledge about the UpperSanta CruzRiver that the project focused on. First, the project identified that indeed effluent is far and away the dominant source of water to the river itself and is an important recharge source in the near-stream zone. Second the project demonstrated that a clogging layer does develop in the stream bed of the Santa Cruz and, that this clogging varies in space with distance downstream of the Nogales International Wastewater Treatment Plant (NIWTP), and that this clogging seems to be removed or at least relieved following flooding. Third, dendrochronology work shows that the effluent began having an influence on tree growth starting in the early 1970’s and that this influence continues to this day[s1].[TM2] For more details on this project and these preliminary results please see an attachment at the end of this proposal summarizing our results thus far. The current proposal is not a renewal of this current project but rather an extension beyond the original aims of that project.

In parallel to the documentation of effluent’s importance and the affect effect of clogging on the Santa Cruz, preliminary work to investigate the use of trees to identify the influence of effluent in the Santa Cruz system has been completed (Paul Sheppard unpublished data). Since, riparian trees have been shown to take up and remove certain nutrients, pollutants, and natural elements from surface and subsurface water (Marler et al. 2001), this preliminary work has sought to identify potential effluent markers that could be used in tree rings. The aim of the work is thus to enable the coupled use of dendrochronology (tree-ring science), and specifically dendrochemistry (chemical analysis of tree rings), as a tool for monitoring spatial and temporal changes in surface and groundwater quality along effluent-dependent waterways. The pPreliminary data shows elevated levels of both europium (Eu) and gadollinium (Gd) in tree rings of cottonwood trees of the Upper Santa Cruz . [s3]The Gd elevation is expected and a likely indicator of effluent influence since because Gd is used in medical magnetic resonance imaging and is a micropollutant that enters waterways from wastewater treatment plants (Bau et al. 2006). The Eu spike is less expected but and [s4]indicates a need to develop a transfer function relating river and groundwater conditions to what is observed in tree rings.

Our preliminary results show elevated levels of Gd in the Upper and LowerSanta CruzRiver, thus indicating good potential for developing dendrochemistry to detect the presence and temporal and spatial distribution of micropollutants in effluent-dependent waterways of Arizona. A preliminary chemical analysis of two increment core samples from cottonwood trees found along the Upper and Lower Santa Cruz River revealed that the element europium (Eu) is noticeably elevated relative to natural abundance compared to other REEs (Figure 1A & C). This Eu signal is unexpected, and we are not sure what it means; learning more about environmental Eu will be a secondary objective of this research. Notwithstanding Eu, Gd is noticeably elevated relative to natural abundance compared to the remaining REEs (Figure 1B & D). Furthermore, both trees indicate biannual variation in Gd as well as in the other REEs (Figure 2A & B). These Gd results confirm that this proposed project is likely to succeed in using trees to document Gd, and potentially other micropollutants, in effluent-dependent waterways. The project outlined in this proposal will therefore expand data collection to effluent-dependent waterways throughout Arizona and will focus on sample analysis to quantify the presence, abundance, and temporal and spatial distribution of Gd in riparian trees.

Coupled together, the existing upper Santa Cruz results and the dendrochemistry work point in an new and innovative research direction. If we can demonstrate a link between the tree ring chemistry and effluent conditions, it should be possible for us to back out how the influence of effluent varies in space and has varied in time along the Upper Santa Cruz. Additionally, we need to understand how clogging evolves temporally and spatially at a more detailed level to understand how river and effluent conditions influence aquifer recharge. Our proposed research thus focuses on three questions- : First, how effectively are contaminants in the effluent transferred into tree tissue? Second, how does the influence of effluent on vegetation vary with distance from the river? Third, what is the spatial and temporal variability in streambed clogging and recharge within the Santa CruzRiver?

2. Approach, Methods, Procedures, and Facilities

Answering[s5] these questions requires three research approaches. First, we need to continue to quantify river and groundwater quality and to quantify rare earth elements in the surface and groundwaters of this system. Second, we need to focus on several transects of trees to understand how river, vegetation, and groundwater conditions along with distance from the river. Finally, we will need to investigate the spatial and temporally variability of the clogging layer in more detail than we have done to date. This research will focus on three river reaches of the Santa Cruz AMA (Figure 2[s6]). O, one reach will be in the non-effluent dominated reach upstream from the NIWTP at Kino Springs. The other two reaches will be in the effluent dominated reach of the river. O; one at Rio Rico road just 3km downstream of the outfall and the other at Santa Getrudis Lane some 15km downstream from the outfall. The reason for the selection of these two reaches is that our existing geochemical results in surface and groundwater indicate that the Rio Rico reach is losing while the Santa Getrudis site is gaining. Additionally through the National Park Service we have access at Santa Getrudis Lane, at Kino springs we have the cooperation of the landowner, and at Rio Rico we are confident through cooperation with the Santa Cruz AMA we can gain access to the site. Additionally there are groundwater wells that we have already sampled in cooperation with either the Arizona Department of Water Resources and with the National Park Service at each of these sites.

At each reach, surface water samples will be collected monthly for the duration of this project and be analyzed for major ions as well as rare earth element concentrations. Similarly, at the wells in and near these river reaches will be analyzed for rare earth elements to assess the background concentrations as well as the potential influence of effluent.

Once forested effluent-dependent reaches of streams have been identified, increment core samples will be taken from suitable, mature and healthy riparian trees (Populus fremontii and Celtis reticulata) growing therein. The tree-ring samples will be crossdated and measured for REEs, with a focus on Gd. Samples will be measured using inductively coupled plasma, mass spectroscopy (ICP-MS) at UA Soil, Water, and Environmental Sciences, who are experienced in ICP-MS and have worked with Dr. Sheppard on previous dendrochemical analysis. This research augments previous work conducted by doctoral candidate Amy McCoy (UA Arid Lands Resource Sciences) on riparian dynamics and will constitute a chapter of her dissertation. This research will also contribute to Dr. Sheppard’s on-going dendrochemistry research and innovation. Furthermore, we will work with Friends of the Santa CruzRiver and Arizona Department of Environmental Quality to obtain long-term records of water quality monitoring data along selected stream reaches. [TM7]

Geophysical approach - ERT and temperature

[TM8]

3. Related Research

In many de-watered rivers in the western United States, discharges of effluent, or treated wastewater, can augment surface flow in ephemeral or intermittent streams and enhance riparian habitat (Tellman 1992, Marler et al. 2001, Bouwer 2002, Brooks et al. 2006)[s9]. In addition to providing additional water to riparian systems, effluent is also high in nutrients and supplies additional nitrogen to the river system (Stromberg et al. 1993). This additional water source may expand in the future as more groundwater is pumped to support growing populations and is available for re-use in habitat restoration projects and for aquifer reclamation. Ultimately, these effluent flows may be critical to riparian survival in arid and semi-arid river systems where surface water and groundwater have been de-coupled due to anthropogenic changes and drought impacts (Patten et al. 1998).

Riparian ecosystems have been shown to be effective nutrient sinks that can rapidly remove nitrogen (N) and other nutrients from water flowing through floodplain soils, particularly in agricultural and effluent-dominated systems (Schade et al. 2002). Nitrogen enters most natural riparian systems through importation of silt-laden floodwaters, surface runoff, and groundwater recharge from the surrounding watershed (Adair et al. 2004). Effluent-dominated streams receive additional infusions of nutrients through daily inflows of nutrient-rich effluent. However, the role of riparian vegetation in nutrient removal mechanisms remains unclear and patterns of nutrient accumulation and turnover are also poorly understood (Schade et al. 2002, Adair et al. 2004). For riparian vegetation specifically, Marler et al. (2001) demonstrated in a controlled environment that Fremont cottonwood (Populus fremontii), Goodding willow (Salix gooddingii), and exotic saltcedar (Tamarix ramosissima) increased their shoot:root biomass ratio as nitrogen increased. In a field experiment, Adair and Binkley (2002) demonstrated that cottonwood germinants were co-limited by both water and nitrogen, indicating that nitrogen may play an important role in riparian vegetation productivity and composition. Therefore, additional inflows of nutrients into riparian systems may impact the rate of nutrient cycling as well as phreatophytic growth and abundance.

One yet unanswered question in riparian ecology is the degree to which riparian trees uptake other elements and pollutants, in addition to nutrients, found in effluent-dominated stream ways. Recent research on emerging contaminants indicates that the presence of endocrine disruptors and other micro-pollutants in effluent-dominated streams impacts fish and macro-invertebrate populations (La Point and Waller 2000[s10]). While numerous methodologies can be used to detect the presence of emerging contaminants, dendrochronology can offer valuable insights into not only the presence or absence of certain elements, but can help decipher temporal patterns and variations as well. In additional, there are many additionalother unresolved ecohydrological issues regarding the release of effluent, a third source of water, into ground-water dependent riparian systems. Few if any studies have studied how native riparian vegetation responds to continued inflows of nutrient-rich effluent and the possible associated changes in riparian community composition and structure. No studies have examined this from the perspective of climate variability and the potential for prolonged droughts and rising temperatures to increase freshwater demands, further degrade riparian systems, and potentially increase the number of streams reliant upon effluent to maintain surface flows and associated riparian habitats. Ultimately, a lack of understanding about the dynamics of effluent-dominated streams has created a void in methods suitable for evaluating the ecological integrity of these systems (Brooks et al. 2006). The research outlined in this proposal aims to fill a methodology void by pioneering the use of dendrochronology in detecting and documenting changes in groundwater quality in effluent-dominated streams in Arizona.

4. Training Potential

In collaboration with PI, Dr. Paul Sheppard, this research will be conducted between March 2008 – December 2008 by Amy McCoy, a doctoral candidate in Arid Lands Resource Sciences. Additional opportunities for graduate student training include a collaboration with Meg White, a PhD candidate in Julie Stromberg’s laboratory at ArizonaStateUniversity in the School of Life Sciences.

5. Information Transfer

Participatory, bi-directional knowledge transfer will be critical to the success of this project. Using local knowledge to help inform research efforts, the results of this multi-disciplinary project will have the potential to influence local decision making and provide the foundation for policy development. The results of this research will need to be disseminated widely and will be of interest and utility to a great number of stakeholders, many of whom have already expressed an interest in the project, including Santa Cruz County, Arizona Department of Water Resources, SCAMA, Pima County, Friends of the Santa Cruz River, Sonoran Institute, Tumacácori National Historical Park, The University of Arizona (SAHRA, WRRC, Office of Arid Land Studies), and landowners along the Santa Cruz River. Individual meetings with landowners will be scheduled, to ensure that they are kept up-to-date on the research being done on their land. In addition, longer-term impacts will be derived from educational materials developed from this case study to support public education initiatives including the Riparian Ecology Extension Program, the Geospatial Extension Program, and the Master Watershed Stewards Program.

As an inherently inter-disciplinary project, the research results will be submitted for publication in several thematic journals. In addition, the graduate students will present the results at one or more technical conferences. An executive summary of the results will be made available via the websites of: the Laboratory of Tree-Ring Research ( SAHRA (sahra.arizona.edu), the Office of Arid Land Studies ( and the Friends of the Santa CruzRiver (friendsofsantacruzriver.org). Tree-ring data developed for the project will be made available to the paleoclimatic research community through the WorldDataCenter of the

NationalClimaticDataCenter (

[s11]

Section 3

1. Interaction with Centers