# Presentation: 407483

## An Overview and Preliminary Data of a Five-year Water Quality Study of the Yukon River

**An Overview and Preliminary Data of a Five-year Water Quality Study of the Yukon River**
*P.F. Schuster**1**, R.G. Striegl**1**, G.R. Aiken**1**, T.P. Brabets**1**, R.P. Hooper**1**, D.P. Krabbenhoft**1**, M.M. Reddy**1**, H.E Taylor**1**, R.L Michel**1**, A.M. Shiller**2**, *
*D.D Eberl**1**, M.A. Voytek**1**, T.F. Kraemer**1**, C. Kendall**1**, and J. Finlay**3**	*					1) USGS		2) USM		3) U of MN

- Abstract

- The U.S. Geological Survey is conducting a five-year water quality study of a 3000 km reach of the Yukon River from its headwaters in the Yukon Territory, Canada to Pilot Station, Alaska near its mouth and just above tidal influence.  The water quality of the Yukon River, the fourth largest river system in North America, is poorly documented and may be changing in response to warmer temperatures.  Permafrost regions in the Yukon River drainage basin are melting.  As permafrost melts, the frozen soil is transformed into biogeochemically active zones. Runoff moving through and across these active zones is hypothesized to increase the flux of solutes to Yukon tributaries and the main stem, ultimately changing the Yukon River water chemistry. The objectives of the five-year study are: 1) Establish a baseline describing the general water quality of the Yukon River and its major tributaries as a reference to measure future changes.  This objective will be achieved by sampling the Yukon River and two of its major tributaries at five fixed sampling sites approximately seven times from March through September for a total of five years; 2) Identify processes that affect or control the water quality of the Yukon River and its tributaries.  This objective will be achieved by intensive sampling campaigns at high flow in June and low flow in late August during 2002-2004. The first reach and its tributaries from Eagle, AK to the Dalton Highway were sampled during the summer of 2002.  The second reach, from the highway to Pilot Station will be sampled during the summer of 2003. The third reach from Whitehorse, Canada to Eagle, AK will be sampled during the summer of 2004.
- Along with discharge, a suite of geochemical parameters, including suspended sediment, quantitative mineralogy, major ions, trace elements and nutrients are being measured with emphasis on dissolved and particulate carbon, gas flux and generation of methyl mercury. Discharge and water quality sampling using equal discharge increments provide instantaneous fluxes. In addition, the occurrence and fate of constituents of environmental concern, such as mercury and other toxic metals, are being addressed.  Identification of the sources and sinks of these constituents, in addition to the processes controlling their fate and reactivity, will provide an important frame of reference to assess water quality changes in the basin that may result from permafrost melting and a warmer climate.  Preliminary data from fixed station sampling and the 2002 summer sampling campaign indicate that water quality in the Yukon River drainage basin is sensitive to the hydrologic state of the river.  Seasonally and spatially, dissolved organic carbon (DOC) ranges from 1 to 54 mg/L, carbon dioxide partial pressure ranged from <200 to several thousand uatmospheres, and major ions such as sulfate and calcium range from 4 to 74 mg/L.

***Will a warming climate affect the water quality of the Yukon River ***
***and the Bering Sea?***

**Melting permafrost**

**Surface water/soil water/ground water interaction**

**Increased carbon, nutrients, metals, sediment fluxes**

**Increases/changes in carbon and sediment**

**Increases in metal mobility and loads**

***The Problem***

***National Stream Quality Accounting Network (NASQAN)***
***NASQAN Yukon River Project: http://water.usgs.gov/nasqan/yukon/***

**Study Approach:**
**NASQAN is performing fixed station sampling at five sites during 2001-2005 (see map below) to estimate annual mass fluxes.  Scientists will also conduct boat-based intensive sampling the river and its major tributaries to create a broader spatial and temporal characterization**
**          ****of the Yukon basin and it’s sub-basins.****  **

**Fixed Site Network:**
***Baseline data***
**     ****The five fixed sites will be sampled for a variety of organic and inorganic **
**constituents over a five year period to establish a baseline database.  Each year, these sites will be sampled **
**approximately seven times, including one under-ice measurement.  Mass fluxes calculated for the fixed sites **
**will be used to identify source areas of contaminants, and to estimate delivery of these contaminants to the Bering Sea.**

**Intensive Sampling:**
***Process-based data***
**     ****Scientists will conduct intensive boat-based sampling of the Yukon river twice per year, once near peak flow conditions in early June and once near base flow conditions in August/September.  The entire Yukon River will be sampled by this method over a three year period.  **
**The intensive sampling will increase the interpretability of the flux measurements, and will provide an alternate data set that may be a more sensitive indicator of change.**

**2002****	****	****    (completed)**
**between Eagle and Stevens Village**
**2003****	****	****     (proposed)**
**between Stevens Village and Pilot Station**
**2004**
**between Whitehorse, Canada, and Eagle**

***Sampling the Tanana River***

***USGS volunteers collected grab samples during Kayak trip, July 2001***
***providing insight for large-scale sampling strategies***

**Yukon watershed is very dynamic:**
**High spatial variability**
**Some Flats tribs may be a significant**
**source of DOC**
**The Flats as a whole appears to be a**
**source of DOC**

**Specific UV Absorbance (SUVA)**
**is an indicator of the “quality” of**
**The DOC **
**SUVA’s do not vary spatially at **
**large scale, suggesting similar**
**carbon sources**

***Maximum sunset on the Yukon in July***

***Sampling the Tanana River***

**Carbon Cycling**
-   **Climatic warming of the Yukon River basin has resulted in **
**lengthening of the growing season, melting of permafrost, **
**deepening of the soil active layer, drying of upland soils, **
**shrinking of wetlands, and increased fire frequency.  **
**These mostly terrestrial effects will result in change in the**
**timing, magnitude and fate of carbon and nutrient delivery**
**to the Yukon River and its tributaries.  Within the Yukon **
**basin, carbon inputs are expected to increase most **
**dramatically downstream of large wetland areas presently **
**having substantial carbon storage, such as Yukon Flats.**

***Provisional data***

***The Yukon Flats: Source or sink?***

-  Distinct hydrologic connection to the transport of carbon
-  Reflects the contribution of organic carbon from the
-      watershed (at large scale) to the river
-  Snowmelt is one likely transport mechanism moving
-      carbon from the terrestrial environment to the river.
-  Consistent SUVAs suggest a common source of carbon
-  Yet to be determined:
-      rainfall overland flow or glacial melt contributions

***What is the role of carbon dioxide and methane emissions***
***in the carbon cycle of the Yukon River Drainage Basin?  ***
***Where and when are the sources and sinks?***

***Calibrating the IRGA in the field***
***to measure dissolved CO******2****** ***
***concentrations and CO******2****** flux (using ***
***chambers) from the river***

**In June 2002, all locations on the **
**Yukon River main stem sampled **
**between Eagle and Stevens Village, **
**and major tributaries, had above **
**atmospheric concentrations of **
**CO****2****, ranging from ~2.5 to 7 times **
**atmospheric concentration **
**(~370 uatmospheres CO****2****).**** **

***What role does carbon play in the mobilization and transport of trace metals***
***in the Yukon River Drainage basin?   Is there a DOC-metal correlation? ***
***Does this relation exist at the large watershed scale?***

**Mercury**
-      **Mercury is a serious potential **
**threat to humans, as well as to our **
**Nation’s aquatic resources. Nearly **
**all of the mercury in fish is methyl-**
**mercury, a highly neurotoxic form **
**that biomagnifies to high concentrat-**
**ions toward the top of aquatic food **
**webs.  Small quantities of methylmer-**
**cury in the diet can adversely affect **
**wildlife and humans.  Aerial transport **
**is a major anthropogenic source of metals, specifically mercury and cadmium, to interior and**
**western Alaska streams and adjacent marine areas.  Based on lake sediment core data, modern fluxes **
**of mercury to northern Canada and Alaska exceed pre-industrial fluxes by as much as seven-fold. **
**Little is known about the contamination levels in truly remote areas such as the Yukon River basin, **
**where some historic and current mining activities, in addition to atmospheric loading, may be **
**contributing mercury to the aquatic environment.**
**     **
**     ****Dissolved organo-mercury species can form by interactions of the metal with soluble**
**aquatic humic substances.  Such interactions are clearly of interest given the potential release**
**of DOC with respect to permafrost melting.  The significance and strength of such DOC-metal**
**ion interactions in the Yukon River will be assessed.**

**Dissolved trace-metal processing**
**Clean-hands technique (0.02 um filter)**
***Can changes in redox sensitive dissolved***
***Trace elements be used as indicators of***
***Changes in carbon cycling? (Shiller, USM)***

- 4

- 1

- 3

***Filtering samples at camp***

**>SUVA > aromaticity > “more reactive”**