Progress 01/01/06 to 09/30/11
Outputs
OUTPUTS: Outputs produced as a result of this project were one referred journal article, one M.S. thesis, and one invited speaking engagement. PARTICIPANTS: Joeseph B. Staed is now operating an environmental services company in Colorado. W.P Miller is still at the University of Georgia in Athens. The current whereabouts of Paul DeLaune are unknown. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Arsenic (As) is a relatively rare element in soils (U.S. mean is 7.2 mg/kg), but higher levels are often found in soils exposed to As as a result of its usefulness in industry and agriculture. During the first half of the 20th century, when northwest Arkansas led the nation in apple production, lead arsenate was the principal insecticide used to control the apple coddling moth. Elevated levels of As have been found in old orchard soils in several other states, but little is known about soil As levels in northwest Arkansas. Another potential cause of elevated soil As levels is land application of poultry litter, which contains As because for many years As was added to poultry feed to help control coccidial parasites and improve feed efficiency. This study was conducted to determine the effect of prior land use as either orchard, littered pasture, or both, on current soil As levels. A total of 11 sites in Washington and Benton counties were sampled. Three of these were classified as controls, meaning that the bulk of the evidence suggested that they had never been used for apple production nor had they ever received litter. Two sites were old orchards that had never received litter, three sites had been heavily littered but had never been in orchard, and the remaining three sites were old orchard soils that had subsequently been converted to pasture and received litter. At each site, soils were sampled on either a 9 or 25 point grid at 0-2, 2-4 and 4-8 cm depths. Total recoverable As, lead (Pb) and phosphorus (P) were determined by ICP-MS following hot nitric acid/hydrogen peroxide digestion (EPA method 3050B). Arsenic levels in the control soils ranged from 2 to 12 mg As/kg soil. Values as high as 200 mg As/kg soil were found in the old orchard soils, but high in-field and between-field variability caused there to be no significant difference (α=0.1) between As levels in the control and orchard treatments. Soil As and Pb levels were highly correlated with one another in the old orchard soils. Soil P levels were elevated in all litter-only treatments, but soil As and Pb levels were not. The data indicate that some soils in northwest Arkansas do have elevated As levels, but these elevated levels are the result of lead arsenate applications to orchards in the early 20th century. They are not the result of poultry litter applications.
Publications
- Staed, J.B. 2008. Land use effect on arsenic concentrations in Benton and Washington counties. M.S. thesis, University of Arkansas, Fayetteville, AR.
|
Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: None this reporting period. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Laboratory adsorption/desorption experiments are being performed but are not yet completed. Batch adsorption isotherms are being constructed by exposing representative soils from northwest Arkansas to solutions containing arsenate, phosphate, and arsenate+phosphate. Surface (0-5 cm) as well as subsurface (15-20 cm) soils are being used in these experiments. In addition, previously arsenated soils are being exposed to solutions containing phosphate to study phosphate-induced desorption of arsenate. These studies will provide information on the effects of applying high levels of phosphate (such as in animal manures) to soils containing arsenic as a result of previous exposure to lead arsenate.
Publications
- No publications reported this period
|
Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: I was asked to present the results of this study to the local chapter of Sigma Xi, the Scientific Research Society. On February 27, 2009 I addressed a group of approximately 30 individuals at the society's monthly meeting in a room in the Arkansas Union. The talk was free and open to the public and several interested citizens were in attendance. Two attorneys requested additional information. PARTICIPANTS: Mr. Joseph B. Staed (D.M. Miller's M.S. former graduate student). Dr. Kristofor R. Brye, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. Tommy C. Daniel, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. Curt Rom, Horticulture Dept., University of Arkansas, Fayetteville. Dr. Edward E. Gbur, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. William P. Miller, Dept. of Crop and Soil Sciences, University of Georgia, Athens. TARGET AUDIENCES: State, regional and local governmental officials should be made aware of the results of this study. Also, individuals who own, or who are thinking about buying, land that used to be used for apple production should be made aware of the results of this study. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Additional analyses of the data were performed to determine whether or not subsequent addition of poultry litter to old orchard soils caused mobilization and thereby enhanced downward movement of arsenic (As) in these soils. It was found that soil As (and lead (Pb)) concentrations increased with depth (alpha = 0.15) in both the orchard only and orchard/litter treatments but not in the litter only and control treatments. It is still not possible, therefore, to conclusively determine if subsequent application of poultry litter to old orchard soils enhanced the mobilization and downward movement of As, as has been reported by numerous other researchers. Contingent upon additional funding, we would like to address this question by returning to some of these sites and sampling soil to greater depths.
Publications
- Staed, J.B., D.M. Miller, K.R. Brye, T.C. Daniel, C. Rom and E.E. Gbur. 2009. Land use effects on near-surface soil arsenic in the Ozark Highlands. Soil Sci. 174:121-129.
|
Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: I submitted a manuscript to a peer-reviewed scientific journal and the journal accepted the manuscript for publication in early 2009. In addition, I have described my research findings in an impact statement which will be disseminated to the public by the University of Arkansas. PARTICIPANTS: Mr. Joseph B. Staed (D.M. Miller's M.S. graduate student; graduated 8/08). Dr. Kristofor R. Brye, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. Tommy C. Daniel, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. Curt Rom, Horticulture Dept., University of Arkansas, Fayetteville. Dr. Edward E. Gbur, Crop, Soil and Environmental Sciences Dept., University of Arkansas, Fayetteville. Dr. William P. Miller, Dept. of Crop and Soil Sciences, University of Georgia, Athens. TARGET AUDIENCES: State, regional and local governmental officials should be made aware of the results of this study. Also, individuals who own, or who are thinking about buying, land that used to be used for apple production should be made aware of the results of this study. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Northwest Arkansas was the epicenter of the U.S. apple industry in the late 19th and early 20th centuries. At that time, the primary insecticide used in apple production was lead arsenate. Significantly elevated levels of soil As have been reported in other states that had large apple industries. In addition, much of the poultry litter applied to pastures in northwest Arkansas contained As because for many years As was added to poultry rations to control intestinal parasites in the birds. Therefore, in northwest Arkansas old orchard soils and/or soils heavily fertilized with litter may contain elevated levels of As. The purpose of this study was to determine if previous land use (apple production or littered pasture, or both) affected near surface As levels in northwest Arkansas soils. Near surface (0-2, 2-4 and 4-8 cm) soil samples were taken from a total of eleven sites in northwest Arkansas. These sites were divided into four treatment groups. Aerial photographs taken in 1940 and land owner interviews were used to identify old orchard sites not subsequently converted to pasture ("historic orchard") and old orchard sites subsequently converted to pasture ("historic orchard/pasture"). Property owner interviews were used to identify littered pastures that had never been in orchard ("pasture") and sites that had never been in orchard and had never received any litter ("control"). Acid-recoverable (EPA Method 3050B) As, lead (Pb) and phosphorus (P) were determined in all samples. The highest levels of As were found in soils in the historic orchard/pasture treatment, followed by soils in the historic orchard treatment, and then soils in the pasture and control treatments. The average soil As concentrations at all depths in the historic orchard/pasture treatment exceeded the USEPA's Preliminary Remediation Goal (PRG) for As in soil of 22 mg As/kg soil. Also, soil As concentrations increased with depth in this treatment. In the orchard only treatment, soil As levels were elevated relative to levels in the control treatment, and average soil As levels at all depths were very close to the USEPA's PRG of 22 mg As/kg soil. Historic orchard soils in northwest Arkansas have a high probability of containing elevated levels of As. While we will never know the precise extent of the acreage impacted, it has been estimated that in 1919 approximately 80,000 acres of land were being used for apple production in Benton and Washington Counties. Therefore, it is possible that this same number of acres of soil contains elevated levels of As. Northwest Arkansas is one of the fastest growing areas in the US, which means that it is quite possible that historic orchard soils containing elevated levels of As are being converted to residential areas, gardens, etc. Other states (e.g., Wisconsin) with similar concerns have developed soil As testing programs, and Arkansas may want to consider doing the same. Our results indicate that land application of broiler litter has no effect on soil As levels, although application of litter to historic orchard soils does appear to mobilize As and allow it to move deeper into the profile.
Publications
- No publications reported this period
|
Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: All of the landowners who allowed us to sample soil on their property have been informed of the results of the analysis of the soil samples taken from their land. In addition, the president and vice president of Grow Green, a registered student organization here at the University of Arkansas, have been informed of the results of the analysis of the soil samples taken from their organic garden plots.
PARTICIPANTS: The bulk of the work done in this project was done by Mr. Joseph B. Staed, a graduate student working on his Masters Degree in Soil Science. He was assisted by Ms. Rachael Arthur, an undergraduate student majoring in Soil Science.
TARGET AUDIENCES: Land owners and state regulatory agencies will eventually be our primary target audiences for this information. Similar work conducted in Wisconsin led to state legislation requiring that landowners test their soil for arsenic prior to selling it.
PROJECT MODIFICATIONS: We intend to make two major modifications. First, we underestimated the spatial variability in soil arsenic levels in old orchard soils, and we will intensify our sampling in an attempt to quantify and account for this variability. Second, the data suggest that application of poultry litter to old orchard soils may mobilize the arsenic and allow it to move to greater depths in the profile. We will therefore attempt to acquire soil from greater depths in subsequent samplings.
Impacts
Soil samples (0-2, 2-4 and 4-8 cm) were taken from eleven farms having different land use histories in Washington and Benton counties in northwest Arkansas. Two of the farms had been in orchard in the first half of the twentieth century but were not subsequently converted to pasture and hence had never received any poultry litter. Three farms had similarly been in orchard but were then converted to pasture and had been fertilized with poultry litter. Three farms had never been in orchard but had been fertilized with poultry litter for at least 15 years. Three farms had never been in orchard and had never been fertilized with poultry litter and served as the control treatment. The arsenic and lead contents of almost 1100 soil samples were determined by digestion in hot nitric acid + hydrogen peroxide (EPA Method 3050B) followed by inductively coupled plasma-mass spectrometry (ICP-MS). The preliminary results (statistical analysis of the results is not yet complete)
indicate that at the alpha = 0.15 level, soils that were once in orchard have greater arsenic contents than do soils that have never been in orchard. For example, at the 2-4 cm depth the mean arsenic content of old orchard soils was 22.3 mg As/kg soil while for the control soils it was 7.7 mg As/kg soil. The spatial variability in the arsenic content of old orchard soils was high. For example, values as high as 200.7 mg/kg and as low as 7.7 mg/kg were found at the 2-4 cm depth on the same farm. For comparison, the USEPA preliminary remediation goal for arsenic in residential soils is 22 mg As/kg soil. Additional sampling is needed, but at this point it appears that some soils in northwest Arkansas do contain elevated levels of arsenic, and the likely source of this arsenic is lead arsenate applications to apple trees in the early twentieth century.
Publications
- No publications reported this period
|
Progress 01/01/06 to 12/31/06
Outputs
Soil Arsenic (As) levels are usually low (<10 mg/kg) but may increase as a result of human activities such as ore smelting. The spraying of fruit trees with lead arsenate during the first half of the 20th century may have caused elevated levels of As in some northwest Arkansas soils. The practice of applying As-containing poultry litter to pastures may also be contributing As to soils in this area. The objective of this study is to establish background As levels in the soils of northwest Arkansas and to determine if the As levels in some soils are elevated as a result of either lead arsenate or poultry litter application. We identified 11 sites for soil sampling and have completed sampling on 7 of these sites. Two of the sites were apple orchards during the first half of the 20th century. Three of the sites were apple orchards initially but were later converted to pasture and have been receiving annual applications of litter for at least 20 years. Three of the sites
are pastures receiving annual applications of litter but have never been used for apple orchards. The final three sites have never been used for apple production and have never received litter and serve as our control treatment. Soil samples are air-dried, ground and sieved prior to digestion with hot nitric acid and hydrogen peroxide (USEPA Method 3050B). The digestate is analyzed for As, lead (Pb) and phosphorus (P) by inductively coupled argon plasma spectrometry-mass spectrometry (ICP-MS) at the Soil Analytical Laboratory at the University of Georgia, Athens, Georgia. Of the 500 or so samples we have sent to Georgia so far, we have received data back on approximately 150 samples. Based on this limited sample size, background levels of As in the soils of northwest Arkansas are in the 5 to 10 mg/kg range, which is similar to what has been reported elsewhere. In old orchard soils we have found As levels as high as 200 mg/kg, but there also appears to be a great deal of spatial
variability in the As levels in these soils. This is not altogether surprising, given the fact that lead arsenate was applied only to the trees, and that the trees were planted in rows with a 15 to 20 foot alley between them. In the orchard/litter treatments, As levels are comparable with background As levels. This is slightly surprising and may indicate that heavy applications of P (in the form of litter) mobilize As and allow it to move deeper into the soil profile. Arsenic levels in the litter only treatments are not yet available, but the data from the orchard/litter treatment strongly suggests that we will not see accumulations of As in the surface soils as a result of litter application. Background levels of Pb fall in the 30 - 35 mg/kg range. In old orchard soils we have found levels in excess of 700 mg/kg. Soil As and Pb levels are positively correlated with one another.
Impacts
Old orchard soils have As and Pb levels that are up to 25 times greater than background levels. This does not appear to be true, however, for soils in the orchard/litter treatment, where we are finding both As and Pb at background levels. Data for the litter only treatment is not yet available. We have spent roughly one quarter of our funds. What we have left should be sufficient to complete the project.
Publications
- No publications reported this period
|
|