Progress 11/02/16 to 09/30/21
Outputs
Target Audience:
Nothing Reported
Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?A referred journal article has been accepted for publication. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The Mulberry River, a National Wild and Scenic River in Arkansas, has been listed as impaired due to low pH since 2008. To date, there have been no long-term monitoring studies on the Mulberry River. The objective of this study was to identify potential changes in chemistry and possible causes of acidification in the Mulberry River watershed. Eleven locations on the Mulberry River and 10 tributaries of the river were sampled monthly from March 2015 to March 2019 (48-mo) and 34 physicochemical parameters were measured. Trend analyses indicated that there were declines (P<0.05) in specific conductance, total suspended solids, total organic C, total N, SO4, and flow-adjusted soluble Ca and Mg and an increase in Cl and total Al, Fe, and Na. Out of the 21 locations sampled, there were no significant decreases in pH suggesting that regions of the watershed have not been acidified during the duration of this study. The decrease in specific conductance and several constituents suggests that the surface waters of the watershed have become more dilute over time. An increase in streamflow and precipitation has been observed throughout Arkansas and an increase in flow within the Mulberry River watershed may be causing this dilution. The results of this study suggests the watershed has not been acidified. Instead, the postulated dilution makes the watershed more susceptible to sudden changes in pH. Further routine sampling will be needed to fully understand these long-term trends on stream chemistry and the aquatic community of this watershed. Stream chemistry is directly related to land use and changes in land use can result in degradation of surface waters. Growth of conifers, through afforestation or conversion of native hardwood stands, has been attributed to basin acidification in several regions and may be contributing acid to the Mulberry River basin. The objective of this study was to examine the relationship between land use (i.e., coniferous forest, deciduous forest, mixed forest, and pasture) and stream chemistry of 11 tributaries of the Mulberry River over a 2-year period. Mean pH of the 11 tributaries increased with distance from the headwater sub-basin and ranged from 5.6 to 6.5. Coniferous forest land use was not correlated with stream pH (P > 0.05), neither was stream pH predicted (P > 0.05; R2 < 0.01) by coniferous forest land use. Acid neutralizing capacity (ANC) and stream discharge were negatively correlated (P < 0.05) with and partially predicted by coniferous land use (P < 0.05). Acid neutralizing capacity was also positively correlated with total organic carbon (r = 0.68) which was negatively correlated with coniferous land use (r = -0.27) and positively correlated with deciduous land use (r = 0.20). Deciduous land use was positively correlated with SO4 (r = 0.24) and negatively correlated with total N (r = -0.28) and NO3 (r = -0.31). Spearman's rank correlation and principal component analysis identified significant inverse relationships between stream pH and NO3 (r = -0.17) and between ANC and NO3 (r = -0.44), which may suggest that HNO3 may be the primary source of acidity within the Mulberry River basin. Although no relationships were observed between coniferous land use and pH, conifer growth may be affecting the stream buffering capacity of the basin which would increase the susceptibility of the river to acidification.
Publications
- Type:
Journal Articles
Status:
Accepted
Year Published:
2022
Citation:
J. Burgess-Conforti, et al. 2022. Relationships between Land Use and Stream Chemistry in the Mulberry River Basin, Arkansas. Accepted for publication in River Research and Applications
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Progress 10/01/19 to 09/30/20
Outputs
Target Audience:Native Health Matters Foundation is a 501(3)(c) Cherokee community organization and educational foundation dedicated to ensuring sustainable agronomics, environmental safety, farm development, health and wellness, home grown energy, cultural preservation, and stewardship and conservation for all of Indian Country. Changes/Problems:Because we have concluded that the Mulberry is not, in fact, undergoing acidification, the emphasis of the project has shifted away from the question of how afforestation with pines affects soil chemistry, and therefore stream chemistry, to the question of how the growing of industrial hemp on metal-contaminated soils affects soil chemistry, specifically the metal content of the soil. This is consistent with the overall goal of the project, which is to determine how changes in land use affect soil chemical properties. What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest?
Nothing Reported
What do you plan to do during the next reporting period to accomplish the goals?The pH and other water quality paramters of the river will continue to be monitored in order to test the hypothesis that the river is not, in fact being acidified. Also, because the emphasis of the project has now changed, a greenhouse study will be initiated to determine how the growing of hemp on metal-contaminated soils that have been amended with biochar affects soil chemical properties.
Impacts
What was accomplished under these goals?
We have concluded that previously observed declines in pH of water in the Mlberry represent natural fluctuations in the water chemistry of this river and are not indications of acidification of the river as a whole over time. Our new hypothesis is that the water chemistry of this river changes naturally over cycles of up to a year and that the reductions in pH that were observed were simply a manifestation of one of these cycles. This hypothesis is being tested by continuing to monitor the pH and other water quality parameters of the river. For the time being, efforts to identify a cause of the supposed acidification have been suspended.
Publications
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Progress 10/01/18 to 09/30/19
Outputs
Target Audience:We communicated our findings to the president of the Mulberry River Society, a group of concerned citizens who either live or own property within the Mulberry River watershed. In addition, we communicated our findings to the professional scientific community by publishing one article and submitting two more for review in which we describe the results of the project. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A Ph.D. graduate student who was working full-time on the project graduated in May 2019. A post-doc continues to work part-time on the project, as does one research technician and three undergraduate hourly lab assistants. How have the results been disseminated to communities of interest?A Ph.D. dissertation and a referred journal article were published. Two additional manuscripts have been submitted for publication and are currently in review. What do you plan to do during the next reporting period to accomplish the goals?We plan to continue routine monitoring of the Mulberry at multiple locations along the river for at least two more years.
Impacts
What was accomplished under these goals?
Despite measured decreases in pH along some portions of the river, the results of this research suggest that the pH of the Mulberry River watershed has not changed over the past 4 years. However, changes in chemistry being observed throughout the watershed may be the result of a changing climate rather than changes in land use. Throughout the state of Arkansas and portions of the conterminous United States, there has been a statistically significant increase in the amount of precipitation and subsequently the amount of streamflow. This increase in water movement throughout a watershed has the potential to decrease residence time in soil and parent material and cause a dilution of surface water. Over the duration of this study numerous physicochemical parameters changed significantly, and these changes could be attributed to a changing hydrology. Over the approximately 4 years of this study there were significant decreases in TOC, TN, TSS, SO4, soluble Ca and Mg and a subsequent decrease in SpC. This decrease in numerous constituent concentrations apparently was the result of dilution of the surface water that was already quite dilute. The average SpC of the Mulberry River decreased from 35.1 to 18.4 µS/cm from 2015 to 2019 and increases the vulnerability of the watershed to greater shifts in pH. This research also tested the hypothesis that growth of conifers, either through afforestation or conversion of native hardwood stands, was a source of acidification. Soil samples were collected from 10 paired deciduous and coniferous stands throughout the Mulberry River watershed and five measures of soil acidity (pH in H2O, pH in KCl, TEA, base saturation, and ANC) indicated no significant differences between stands. Average soil pH(H2O) of both deciduous (pH = 5.2) and coniferous (pH = 5.3) stands was less acidic than other forest soils reported in the literature. Concentrations and contents of water-extractable, Mehlich-3 extractable, and exchangeable Ca and Mg were also significantly greater in soil beneath the coniferous soil compared to the deciduous soil. Similar to the watershed soils, there were no significant differences in the pH of streams draining sub-watersheds containing primarily conifers or deciduous forest. Coniferous forest land use was not correlated with stream pH; neither was stream pH predicted by coniferous forest land use. Instead, ANC and stream discharge were negatively correlated. This decrease in buffering capacity and stream flow may negatively affect stream chemistry but this was not observed in this study. Nitrate was inversely related to both stream pH and ANC which may indicate that HNO3 is the primary acid cycling throughout the watershed. Land use data for the Mulberry River watershed is not available from 2012 to the present, but there was a decrease in the amount of coniferous forest land use from 1991 to 2011. This decrease in the area of pine tree density reduces the likelihood that conifer growth has been detrimental to the watershed. While the changes observed over the duration of this study indicate the watershed has become more dilute, the changes in chemistry observed do not currently warrant remedial efforts. Four years is not enough time to fully understand watershed dynamics and future efforts should instead focus on continued monitoring of the Mulberry River and should also include monitoring of a neighboring, non-impaired watershed. It is still unknown why only segments of the Mulberry River have shown change in pH over the last 20 years. The Mulberry River was designated a National Wild and Scenic River due to the outstanding natural, cultural, and recreational value it provides and continued monitoring will be necessary in order to ensure this value remains.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2019
Citation:
Burgess-Conforti, J.R., P.A. Moore Jr., P.R. Owens, D.M. Miller, A.J. Ashworth, P.D. Hays, M.A. Evans-White, K.A. Anderson. 2019. Are soils beneath coniferous tree stands more acidic than soils beneath deciduous tree stands?. Environ. Sci. Pollut. 26(15) 14920-14929.
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Progress 10/01/17 to 09/30/18
Outputs
Target Audience:We met with a local group, The Mulberry River Society, on two occasions to update them on our findings. We also met with a group of scientists from the U.S. Forest Service and presented our results to them. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?A Ph.D. graduate student is working full-time on the project. In addition, a post-doc is working part-time on the project. Three undergraduate students have worked on the project as hourly lab assistants. How have the results been disseminated to communities of interest?Burgess-Conforti, J.R., P.A. Moore Jr., E.D. Pollock, P.R. Owens, D.M. Miller, A.J. Ashworth, P.D. Hays, M.A. Evans-White, K.A. Anderson. Potential Sources of Acidity within the Mulberry River Watershed. Mulberry River Earth Day Celebration. April 20, 2018 Burgess-Conforti, J.R., P.A. Moore Jr., E.D. Pollock, P.R. Owens, D.M. Miller, A.J. Ashworth, P.D. Hays, M.A. Evans-White, K.A. Anderson. Mulberry River Water Quality Trends. Mulberry River Acidity Discussion - U.S. Forest Service/Mulberry River Society Joint Meeting, Russellville AR, October 29 2018. Burgess-Conforti, J.R., P.A. Moore Jr., E.D. Pollock, P.R. Owens, D.M. Miller, A.J. Ashworth, P.D. Hays, M.A. Evans-White, K.A. Anderson. Spatial and Temporal Variability in pH and Water Chemistry of the Mulberry River, February 2018 Update. Mulberry River Society, February 10, 2018. What do you plan to do during the next reporting period to accomplish the goals?We have three manuscripts describing our results that are in various stages of preparation. These should all be published in the coming year. In addition, we intend to focus our attention now on acid precipitation and groundwater as potential sources of acidity that may be impacting the chemistry of the Mulberry River.
Impacts
What was accomplished under these goals?
We examined the relationship between land use (i.e., coniferous forest, deciduous forest, mixed forest, and pasture) and stream chemistry of 11 tributaries of the Mulberry River over a 2-year period. Mean pH of the 11 tributaries increased with distance from the headwater sub-basin and ranged from 5.6 to 6.5. Coniferous forest land use was not correlated with stream pH (P > 0.05) neither was stream pH predicted (P > 0.05; R2 < 0.01) by coniferous forest land use. Acid neutralizing capacity (ANC) and stream discharge were negatively correlated (P < 0.05) with and partially predicted by coniferous land use (P < 0.05). Acid neutralizing capacity was also positively correlated with total organic carbon (r = 0.68) which was negatively correlated with coniferous land use (r = -0.27) and positively correlated with deciduous land use (r = 0.20). Deciduous land use was positively correlated with SO4 (r = 0.24) and negatively correlated with total N (r = -0.28) and NO3 (r = -0.31). Spearman's rank correlation and principal component analysis identified significant inverse relationships between stream pH and NO3 (r = -0.17) and between ANC and NO3 (r = -0.44), which may suggest that HNO3 may be the primary source of acidity within the Mulberry River basin. Although no relationships were observed between coniferous land use and pH, conifer growth may be affecting the stream buffering capacity of the basin which would increase the susceptibility of the river to acidification.
Publications
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Progress 11/02/16 to 09/30/17
Outputs
Target Audience:Some of the results of the project were presented to other professional soil scientists at the annual meeting of the Soil Science Society of America. Changes/Problems:Prelimiary results suggest that acidification of the river is not being caused by conversion of deciduous forest to coniferous forest in the watershed. Our attention will now focus on other possible causes, such as acid rain, ammonia deposition, and increased oxidation of sedimentary pyrite, which may be related to increased fracking for natural gas in the southern half of the watershed. What opportunities for training and professional development has the project provided?A Ph.D. graduate student is working full-time on the project. In addition, a post-doc is working part-time on the project. Three undergraduate students have worked on the project as hourly lab assistants. How have the results been disseminated to communities of interest?Burgess-Conforti, J.R., P.A. Moore Jr., D.M. Miller, P.R. Owens, M.A. Evans-White, A.J. Ashworth, K.A. Anderson. Comparison of Litter & Soil Chemical Properties Beneath Paired Deciduous and Coniferous Tree Stands. Soil Science Society of America, Tampa, FL, October 24 2017. What do you plan to do during the next reporting period to accomplish the goals?Two other possible causes of the observed acidification of the river are acid rain and/or atmospheric ammonia deposition. Ammonia released from confined animal feeding operations can reach the soil in precipitation and generate acidity when it undergoes nitrification. In 2018, rain samples will be collected from two locations within the watershed to evaluate the potential presence of acid rain. In addition to the monthly sampling of the Mulberry River, samples will be collected at tributaries throughout the watershed to further characterize the chemistry of the watershed. Stable isotopes of N, S, and O will be analyzed on collected rain and stream samples to distinguish between sources of H2SO4 (i.e., acid rain or geochemical oxidation of pyrite) and NH4+/NO3- (i.e., acid rain or animal waste-derived ammonia). Comprehensive statistical analysis of water quality data will also begin to quantify the extent of changes in water quality between 2015 and 2018.
Impacts
What was accomplished under these goals?
The Mulberry River is a 110 km long tributary of the Arkansas River and is located within the Ozark National Forest. The Mulberry river has been designated a "National Wild and Scenic River" since 1992. In 2008, the Mulberry River was placed on the EPA's 303(d) list of impaired water bodies by the Arkansas Department of Environmental Quality (ADEQ) due to the low pH of a 9.1 mile segment of the river. In response to the acidification of the river, intensive stream monitoring began in March 2015. Water samples are collected monthly from 11 locations on the Mulberry River and 10 tributaries that feed into the river. River pH, temperature, dissolved oxygen, and electrical conductivity are measured in-situ. Acid neutralizing capacity, chlorphyll-α, suspended solids (total, inorganic, and organic), NO3-, and concentrations of 21 elements (i.e., Al, As, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, S, Se, Ti, and Zn) are measured upon returning to the laboratory. It is not known at this time what is causing the acidification of the river. One possibility is the conversion of deciduous forests to pine plantations throughout the river watershed. Soils supporting coniferous vegetation tend to be more acid than soils supporting deciduous vegetation because coniferous litter (pine needles) contains a lower basic cation:acid cation ratio than does deciduous litter. In or4der to test this hypothesis, over the past year 400 soil samples were collected to analyze the effects of forest type (e.g., deciduous, coniferous, mixed vegetation) on soil chemical characteristics. Preliminary statistical analysis indicates that there is no significant effect of tree stand or species on soil acidity. Furthermore, preliminary analysis of four measures of acidity (i.e., water pH, KCl pH, base saturation, and total exchangeable acidity) indicates that the soil is not acidic enough to cause acidification of the Mulberry River watershed.
Publications
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