Progress 10/01/05 to 09/30/07
Outputs
A recently completed water quality study analyzed water quality monitoring data collected over the last two decades in Washington County, Maine. The groundwaters and surface waters of the region contain varying concentrations of the broad spectrum herbicide hexazinone. Hexazinone is widely used to eliminate weed competition in Downeast blueberry fields. It is highly soluble in water; has low organic carbon partition; and a long half-life in the groundwater (up to 8 years in sand and gravel soils). It moves to groundwater rapidly after application to the blueberry fields which are all located on coarse textured glacial outwash soils. Hexazinone use in Maine's blueberry fields began in 1983 and water quality monitoring began in 1990. Concentrations of hexazinone in surface water and groundwater over time have ranged from 145 ug/L to below detection. Since 1990, there has been a four-fold decrease in hexazinone application rates. Despite the change in managment, the
concentrations of hexazinone in groundwater have changed very little. We used the hexazinone concentration data, groundwater models and precipitation data to model the movement of hexazinone in groundwater over time. The manuscript from this research is in preparation. In another soil and water quality study, we quantified the nutrient inputs into the Taunton Bay estuary from the surrounding watershed. This research determined that nutrient inputs from the uplands were not great enough to have caused the recent (1996-2002) eelgrass die-off in the Taunton Bay estuary. Next we studied eleven sets of aerial photographs of the estuary and quantified the area and crown cover density of eelgrass between 1955 and 2005. The data illustrated that eelgrass area and crown cover declined steadily in Taunton Bay estuary from 1955 to 1995. When the die-off occurred, (first observed in 2002) the loss rate was three times higher than the previous four decades. In the next phase of this work we will
investigate the role of nutrient inputs from a pen aquaculture business that occupied a portion of the estuary between 1993 and 1997. The manuscripts from this research are also in preparation.
Impacts
Seagrasses are important to estuarine ecosystems. They support biological growth, provide critical habitat for marine organisms and physically stabilize benthic substrates. The most common cause of seagrass loss is light limitation caused by eutrophication. In most southern New England estuaries, decades of nutrient additions have greatly reduced seagrass communities. However, most of the estuaries in Northern New England have watersheds that are largely forested. Because these estauries have only a small fraction of their watersheds used for agricultural, industrial, or residential land use, Maine's estuaries are excellent locations to observe vegetation changes caused by human induced climate change.
Publications
- Thornton, T., and L. J. Osher. Hexazinone Movement from Uplands to Surface Waters via Groundwater, Maine Water Conference, Augusta, March 2005.
- Osher, L. J. Unraveling the Mystery of Rapid Recent Eelgrass Decline in Taunton Bay, Maine Water Conference, Augusta, March 2005.
- Goodrich, T and L. J. Osher. Tools for monitoring changes in eelgrass (Zostera marina) distribution over time, 7th Shallow Water Science and Management Conference, Atlantic City, New Jersey, September 2006.
- Keats, R., and L. J. Osher. 2007. The macroinvertebrates of Ruppia beds in an estuary. Forthcoming in Northeastern Naturalist.
- Osher, L. J., J. L. Jespersen, and P. Rouleau. Isotopic investigations of the benthos in a Downeast Maine estuary: Quantification of terrestrial nutrient inputs and impacts over space and time. Estuarine Research Federation Biennial Conference, Norfolk, Virginia, October 2005.
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Progress 10/01/05 to 09/30/06
Outputs
A recently completed water quality study analyzed water quality monitoring data collected over the last two decades in Washington County, Maine. The groundwaters and surface waters of the region contain varying concentrations of the broad spectrum herbicide hexazinone. Hexazinone is widely used to eliminate weed competition in Downeast blueberry fields. It is highly soluble in water; has low organic carbon partition; and a long half-life in the groundwater (up to 8 years in sand and gravel soils). It moves to groundwater rapidly after application to the blueberry fields which are all located on coarse textured glacial outwash soils. Hexazinone use in Maine's blueberry fields began in 1983 and water quality monitoring began in 1990. Concentrations of hexazinone in surface water and groundwater over time have ranged from 145 ug/L to below detection. Since 1990, there has been a four-fold decrease in hexazinone application rates. Despite the change in managment, the
concentrations of hexazinone in groundwater have changed very little. We used the hexazinone concentration data, groundwater models and precipitation data to model the movement of hexazinone in groundwater over time. The manuscript from this research is in preparation. In another soil and water quality study, we quantified the nutrient inputs into the Taunton Bay estuary from the surrounding watershed. This research determined that nutrient inputs from the uplands were not great enough to have caused the recent (1996-2002) eelgrass die-off in the Taunton Bay estuary. Next we studied eleven sets of aerial photographs of the estuary and quantified the area and crown cover density of eelgrass between 1955 and 2005. The data illustrated that eelgrass area and crown cover declined steadily in Taunton Bay estuary from 1955 to 1995. When the die-off occurred, (first observed in 2002) the loss rate was three times higher than the previous four decades. In the next phase of this work we will
investigate the role of nutrient inputs from a pen aquaculture business that occupied a portion of the estuary between 1993 and 1997. The manuscripts from this research are also in preparation.
Impacts
Seagrasses are important to estuarine ecosystems. They support biological growth, provide critical habitat for marine organisms and physically stabilize benthic substrates. The most common cause of seagrass loss is light limitation caused by eutrophication. In most southern New England estuaries, decades of nutrient additions have greatly reduced seagrass communities. However, most of the estuaries in Northern New England have watersheds that are largely forested. Because these estauries have only a small fraction of their watersheds used for agricultural, industrial, or residential land use, Maine's estuaries are excellent locations to observe vegetation changes caused by human induced climate change.
Publications
- Thornton, T., and L. J. Osher. Hexazinone Movement from Uplands to Surface Waters via Groundwater, Maine Water Conference, Augusta, March 2005.
- Osher, L. J. Unraveling the Mystery of Rapid Recent Eelgrass Decline in Taunton Bay, Maine Water Conference, Augusta, March 2005.
- Goodrich, T and L. J. Osher. Tools for monitoring changes in eelgrass (Zostera marina) distribution over time, 7th Shallow Water Science and Management Conference, Atlantic City, New Jersey, September 2006.
- Keats, R., and L. J. Osher. 2007. The macroinvertebrates of Ruppia beds in an estuary. Forthcoming in Northeastern Naturalist.
- Osher, L. J., J. L. Jespersen, and P. Rouleau. Isotopic investigations of the benthos in a Downeast Maine estuary: Quantification of terrestrial nutrient inputs and impacts over space and time. Estuarine Research Federation Biennial Conference, Norfolk, Virginia, October 2005.
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Progress 10/01/04 to 09/30/05
Outputs
Land application of biosolids has caused concern because of perceived potential negative environmental impacts. Currently, composted biosolids are unregulated as waste materials. Some long-term biosolids applications have resulted in increased concentrations of metals in soils and additions of metals as metal salts with soluble organics or in biosolids have resulted in increased metal concentrations in groundwater. Applications have been found to increase the mobility of metals in soil due to a combination of high ionic strengths of the soil solutions, high background concentrations, and complexation of metals in the soils and biosolids by dissolved organic compounds. In addition, biosolids applications to soils has resulted in elevated concentrations of nickel (Ni), Cu, chromium (Cr), Zn, cadmium (Cd), and manganese (Mn) in plants growing in those soils. When biosolids are applied to soil surfaces, the leachable metals in the biosolids are transported down into the
soil profiles with precipitation. The greatest concentrations of metals are found in the surface horizon, and metal concentrations decrease with depth. Complexation of metals with biosolids organic matter facilitates the movement of the metals through the soil profile and beyond. In a column study in which soil porosity created by wormholes and root channels allowed preferential flow, high concentrations of metals were observed in leachate. Others found lead (Pb) and Ni concentrations in leachate above European Union maximum admissible standards for drinking water quality. We designed a column study to determine if application of composted biosolids to land may have a considerable negative impact on groundwater quality. We collected and analyzed the leachate from two biosolids treatments, one topsoil treatment, and a set of untreated (control) columns. Concentrations of ammonium nitrate and metal cations were measured. Biosolids application also resulted in increased NH4+ and NO3-
leaching. Nitrate leachate exceeded ammonium leachate, indicating a well-aerated environment. Metals in leachates from undisturbed profiles may be considerably higher because leachates follow macropores and bypass much of the sites of soil CEC.
Impacts
Our results indicate that leachates from biosolids mixed with sand had higher metal concentrations than those from biosolids applied on top of sand. These results support the suggestion of Camobreco et al. (1996) that metals in sewage sludge may be more mobile in course-textured soils. Mixing biosolids with coarse materials improves structural integrity, compaction resistance and permeability. This practice should be minimized in close proximity to drinking water wells.
Publications
- Osher, LJ and Seymour, RM. 2005. Biosolids as soil amendments in architectural landscapes: potential impacts to ground water. In review.
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Progress 10/01/03 to 09/30/04
Outputs
Soil quality research completed this year included a study of Polyacrylamide (PAM) as a soil amendment used to reduce soil erosion in agricultural fields. PAM reduces erosion by enhancing water infiltration, improving soil aggregate stability, reducing the negative effects of raindrop impact, and decreasing soil crusting. Investigations included quantification of soil loss after heavy rains onto PAM treated and untreated soils and the ability of PAM to maintain soil aggregate stability after raindrop impact and inundation. Final results indicate that PAM additions to potato fields will reduce soil erosion and associated loss of soil organic matter.
Impacts
Proper application and utilization of PAM in potato fields will reduce soil erosion and thus help to maintain soil carbon.
Publications
- Osher, L J, and L LeClerc, 200_. Polyacrilamide use for improvement of physical properties of agricultural soils. (submitted)
- Osher, L J, and Boucher, J.R., 200_. Determination of the optimum application rate of polyacrilamide for reducing erosion from Maine agricultural soils. (submitted)
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Progress 10/01/02 to 09/30/03
Outputs
Soil quality research completed this year included a study of Polyacrylamide (PAM) as a soil amendment used to reduce soil erosion in agricultural fields. PAM reduces erosion by enhancing water infiltration, improving soil aggregate stability, reducing the negative effects of raindrop impact, and decreasing soil crusting. Investigations included quantification of soil loss after heavy rains onto PAM treated and untreated soils and the ability of PAM to maintain soil aggregate stability after raindrop impact and inundation. Preliminary results indicate that PAM additions to potato fields will reduce soil erosion and associated loss of soil organic matter.
Impacts
Proper application and utilization of PAM in potato fields will reduce soil erosion and thus help to maintain soil carbon.
Publications
- No publications reported this period
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Progress 10/01/01 to 09/30/02
Outputs
This project has three sub-projects. The 1st is the study of the impact on soil & water quality after land use from forest to intensively landscaped estates. The landscapers create planting beds by adding up 2 m of biosolids to the soil surface. The hydrology is changed by the addition of water from drip irrigation systems. A column study was designed to compare the leachate from irrigated, biosolid-amended soils to similar, non-biosolid amended soils. Eighteen columns were packed with field soils such that horizon bulk densities were similar to those observed in the field. Three different biosolid treatments (x 5 replicates) were packed into columns on top of the model field soils. The remaining columns were controls. The experiment was set-up in a temperature-controlled room equipped with an irrigation system and sun-simulating lighting. The columns were irrigated with simulated rainwater at intervals that mimic rainfall at the field site. The biosolid-amended soils
are also irrigated at a rate of 2.5 cm per week. Leachate was collected at monthly intervals and analyzed for metals, N and organic carbon compounds. The experiment was completed in 2002. The columns were dismantled and soil subsamples were analyzed for metals and nitrogen. The 2nd project is designed to identify the role of inorganic soil amendments in improving the response of agricultural soils to water stress and reducing soil erosion. The majority of Maine's farms are not irrigated and thus are highly susceptible to drought conditions. Polyacrilamide (PAM) is an inorganic soil amendment commonly used in the western US to reduce erosion in irrigated potato agroecosystems. Experiments were designed to identify the amount of PAM that should be added to Maine's potato soils to provide optimum flocculation, moisture holding capacity, aggregate stability and infiltration rate. All experiments will be conducted in the spring of 2003. The soil moisture release experiments will be
completed on the PAM treated soils using pressure plate and pressure membrane apparati (Klute 1986). The 3rd project investigated the impact of N to the organisms and detrital carbon load in an estuary. Intensification of residential development in coastal Maine has resulted in increased use of fertilizers and has accelerated erosion of soils. The leaching of fertilizers results in increases of dissolved N in groundwater, riparian zones and coastal streams and estuaries. Researchers at the United States Geological Survey are working to create a monitoring program and a decision support system for prediction of how watershed development will affect the estuaries of Acadia National Park. This research complemented this project by investigating the faunal community in a Maine estuary over the 2001growing season. We used an in situ experiment with enclosures to determine the ecological response of dominant estuarine consumers of the to nutrient enrichment using a stable isotope
approach.
Impacts
The column study investigated the potential environmental impact of the biosolid additions to coastal soils and watersheds. The results will be made available to local watershed managers, landscape contractors, and companies and municipalities that produce biosolids. The data will be used to educate people about the benefits of using this material to improve soil properties for specific land uses. Plowing and harvesting associated with conventional agricultural land management have a negative impact on many soil physical properties. Documenting improved soil physical properties with polyacrylamide additions will provide valuable information to Maine's potato farmers. Results will include quantification of moisture holding capacity, infiltration rate, aggregate stability, and soil moisture release for soils treated with various concentrations of PAM. This research will determine the optimum application rate for PAM to Maine's to improve soil quality and reduce soil
erosion. Experimental nutrient additions to an estuary resulted in a shift in the community of primary producers, with losses of R. maritima and increases in epiphytic and planktonic algae. Increased nutrients altered the fractionation of C and N stable isotopes by estuary organisms. Assessment of food web structure using stable isotopes showed a dependence of consumers on epiphytic algae as well as terrestrial detrital pools. Increased nutrient loading could result in significant faunal community shifts in similar estuaries and could lead to reductions in detrital C being added to (and stored in) estuary soils.
Publications
- Osher, L.J., H. McLaughlin, and R.M. Seymour, (2003) Biosolids as soil amendments: potential impacts to groundwater. In preparation for Journal of Environmental Quality.
- Osher, L.J and L.G. Leclerc, (2003) Polyacrilamide use for improvement of soil physical properties in Maine's potato agro ecosystems. In preparation for Soil Science Society of America Journal.
- Osher, L.J and L.G. Leclerc, (2003) Polyacrilamide; a soil amendment used to improve soil physical properties. (review paper) In preparation for Soil Science.
- Keats, R., L.J. Osher, and H. Neckles, (2003) The effect of nutrient loading on estuarine foodwebs: a stable isotope approach. In preparation for Estuaries.
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Progress 10/01/00 to 09/30/01
Outputs
This project has two sub-projects. The first is the study of the impact on soil and water quality after land use change. The change is from forest to intensively landscaped estates. The landscapers change the topography of the sites and create planting beds by adding up 0.3m of biosolids to the soil surface. The hydrology of the soils is changed by the addition of water from drip irrigation systems. The biosolids (composted municipal wastewater treatment sludge) are high in organic matter. A column study was designed to compare the leachate from irrigated, biosolid-amended soils to similar, non-biosolid amended soils. Eighteen 10 cm diameter, 1-meter tall Plexiglas columns are being used in this study. All columns were packed with field soils such that horizon bulk densities were similar to those observed in the field. Three different treatments (mixtures of biosolid amendments) were packed into 15 of the columns on top of the model field soils with five replicates of
each treatment. The remaining columns have no additives on top of the model soils. The experiment is set-up in a temperature-controlled room that is equipped with an irrigation system and sun-simulating lighting. The columns are "rained on" with simulated rainwater at intervals that mimic rainfall at the field site. The biosolid-amended soils are also irrigated at a rate of 2.5 cm per week, the usual rate added to landscaped soils in the field area. The experiment began in the summer of 2001. Leachate is being collected at monthly intervals and analyzed for metals, nitrogen and organic carbon compounds. The second sub-project involves identifying the role of organic amendments in improving the response of agricultural soils to water stress. The preliminary work was completed on samples from a soil management study where manure and compost was applied for eight (8) years to 48 plots, while 48 plots in the same study were managed without manure or compost additions. Soil samples were
analyzed to determine the moisture holding capacity under conditions of simulated drought stress using both pressure plate and pressure membrane systems. Results of the soil moisture studies are being analyzed and will be written-up during the next few months. Also during this year, soils will be analyzed from other cropping system studies being completed on U Maine Experiment Stations. This work will determine which amendments improve soil quality by imparting the greatest carbon content over time, and the greatest resistance to water stress.
Impacts
The column study is investigating the potential environmental impact of the biosolid additions to coastal soils and watersheds. The results of the column study will be made available to local watershed managers, landscape contractors, and companies and municipalities that produce biosolids. We hope to identify and minimize any potential negative impacts to soil (or water) quality as a result of using this material. The data will be used to educate people about the benefits of using this material to improve soil properties for specific land uses. Soil organic matter plays an important role in soil quality. It is a source of nutrients for plants and also holds moisture, another important component for healthy plant growth. Plowing and harvesting associated with conventional agricultural land management cause losses of soil organic matter. Additions of organic matter to agricultural soils result in improved soil quality. This research will determine if the increased
organic matter is helping hold moisture. Greater moisture holding capacity will allow these soils to be more drought resistant than soils without the amendments.
Publications
- No publications reported this period
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