FY 2001 ABSTRACTS

• Developing Phosphorus Management Guidelines For Agriculture In The Connecticut River Watershed
• Effect Of Surface Coatings And Ionic Strength On Bacterial Removal Rates In Porous Media
• Effects Of Land Use On Water Quality In A Changing Landscape

DEVELOPING PHOSPHORUS MANAGEMENT GUIDELINES FOR AGRICULTURE IN THE CONNECTICUT RIVER WATERSHED
Principal Investigators: Dr. Elizabeth A. Rochette, Dr. Thomas E. Buob, University of New Hampshire

Problem and Research Objectives:
A summary of soil test phosphorus levels in New Hampshire soil samples submitted to the UNH Analytical Services Lab during the past 3 years indicates that greater than 70% of soils from participating growers are in the high or greater range (greater than 50 mg P kg -1 , Mehlich III extraction) (Buob, unpublished data). It appears that P in New Hampshire's agricultural soils could pose a greater risk to the environment than originally thought. Furthermore, it is important that high P soils be identified, as there should be little or no yield response (increase) to added P in these agricultural soils. There is currently a need to determine at what level of soil test P, and on which soil types, the risk of nonpoint source pollution from P in runoff, erosion, and leaching is greatest.

Several states are adapting an assessment tool, the Phosphorus Site Index, for determination of P contamination risks from agriculture. This approach considers environmental features controlling the fate of phosphorus at any location: site characteristics and transport factors such as soil texture, erosion, runoff potential and proximity to water bodies; chemical features such as the form of phosphorus and its association with soil components, and release of P into solution; and site management factors such as fertilizer types and application rates that influence soil P content (soil test P) (Lemunyon and Gilbert, 1993; NRCS, 1994). In 2002, New Hampshire will begin determining P Site Indices for agricultural areas. As in other states, this tool will be useful for community planners, soil surveyors, cooperative extension specialists, crop consultants, and growers.

Soil test phosphorus values must be included in the New Hampshire P Site Index, and it will be necessary to determine an appropriate test for "environmentally mobile" soil phosphorus. The most appropriate approach will be convenient, cost-effective, and accurate for New Hampshire soils. New Hampshire agricultural soils are dominantly Entisols, Inceptisols, and Spodosols. Spodosols can have relatively high P sorption capacities due to relatively high iron and aluminum sesquioxide contents (Simard et al., 1994). Due to the influence of soil pedologic characteristics on the relationship between soil test P and P sorption characteristics (Beauchemin and Simard, 1999), and the variety of soil test approaches proposed for use in environmental assessments of P in soils, this study was undertaken to determine the most appropriate soil test approach for P Site Indices in New Hampshire.

The objectives of this study were to:

• Chemically and physically characterize representative agricultural soils from the Connecticut River Watershed (CRW) in New Hampshire to allow comparison of soil types within the state and New England, and estimate the behavior of P in untested soils with known characteristics.
• Determine the relationships between soil test methods used in New Hampshire and Vermont (Mehlich 3, and Modified Morgan), using the CRW/New Hampshire soils.
• Determine the relationship between water-extractable P and soil test P for the CRW/NH soils. This relationship will provide information to help predict sites that may be "susceptible" to phosphorus due to a high or very high levels of P in the soil test results.
• Produce P sorption and desorption curves for a subset of the soils. The curves (i.e., the equations describing them) will be used to help group soil types based on their native abilities to hold or release phosphorus.

Principal Findings and Significance:
A suitable approach for testing New Hampshire soils for environmentally-mobile P appears to include a combination of Mehlich III extractions for soil test P, PSI measurements to determine sorption capacities, and water/calcium chloride extractions to estimate P concentrations released to soil solutions. Rather than a single soil test P value as is typical in Phosphorus Site Indices, all three of the parameters could be considered as P quantity, P capacity, and immediate P release terms, respectively.

The Spodosols examined had both the highest sorption affinity for P, and currently the lowest extractable P (including water/calcium chloride-extractable P). If agricultural management of P does not change on these soils, assuming that the soils obtained for this study are representative of all agricultural Spodosols in New Hampshire, P associated with Spodosols may pose minimal threat to the environment. If, however, additional P is added to these soils in the future, they could pose a threat to the environment where erosion is an issue, because these soils can retain relatively high quantities of P that could be carried to surface water on soil particles. Seasonally-saturated Spodosols were not sampled in this study, and may not fit the pattern observed. Entisols and Inceptisols were variable with respect to sorption capacities and extractable P. The relatively lower sorption capacities of Entisols and Inceptisols, coupled with their higher P contents (especially for samples of the Hadley and Windsor soils) suggest that P runoff and leaching are potential considerations for these soil orders.

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EFFECT OF SURFACE COATINGS AND IONIC STRENGTH ON BACTERIAL REMOVAL RATES IN POROUS MEDIA
Principal Investigators: Dr. Carl Bolster, University of New Hampshire

Problem and Research Objectives:
The transport of pathogenic viruses and bacteria in the subsurface poses a potential threat to public health. Contamination of water supplies by fecal material is the most common source of waterborne pathogens. In the 1980's, the use of untreated ground water was responsible for 43% of waterborne disease outbreaks occurring in the U.S. In New England, greater than 96% of all drinking water supplies in violation of drinking water standards are contaminated with bacteria (USEPA 2000). Failing septic systems are considered by EPA to be one of the biggest problems today for New England water bodies and have been suggested as the source of bacterial contamination in surface waters of New Hampshire (Margolin and Jones 1991).

The prevention of microbial contamination of drinking water supplies and surface waters requires an understanding of the processes controlling microbial transport and removal within the subsurface. Among the most important factors shown to influence bacterial transport through porous media are ionic strength (e.g. Fontes 1991) and the presence of metal-oxyhydroxide coatings on sediment surfaces (e.g. Scholl, 1990 #62). In circumneutral pH waters, bacteria and quartz sand grains both exhibit a net negative charge leading to unfavorable conditions for bacterial attachment to sediment surfaces. Increasing ionic strength has been shown to increase this attachment by increasing van der Waals attractive forces. In addition to high ionic strength waters, the presence of metal-oxyhydroxide coatings has also been shown to result in greater attachment rates of bacteria to sediment surfaces owing to the charge reversal imparted by the oxyhydroxide coatings at circumnuetral pH.

While numerous studies have been conducted looking at the effects of ionic strength and surface coatings independently on bacterial deposition rates, no systematic study yet exists looking at the combined effects of ionic strength and surface coatings on bacterial attachment rates. To better understand bacterial attachment and transport in NH aquifers, research needs to be conducted on the combined effects of high ionic strength waters and metal-coated sands. This project examines the effects of ionic strength on bacterial attachment rates to iron-coated sands.

Principal Findings and Significance:
To date we have only collected and analyzed data from one set of column experiments. In numerous studies in the literature it has been observed that increasing ionic strength increases attachment of bacteria to clean quartz sand by increasing sticking efficiency. This enhanced attraction between two like-charged particles is a result of the compression of the double layer allowing attractive van der Waals forces to dominate. However, we observed opposite behavior of bacterial attachment to positively charged iron-coated sand. A clear log-linear decrease in sticking efficiency with increase in ionic strength was observed (figure 1). We plan on additional experiments to verify these findings.

Figure 1. Effect of increasing ionic strength on sticking efficiency of an e. coli isolate to iron-coated Unimin sand grains.

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EFFECTS OF LAND USE ON WATER QUALITY IN A CHANGING LANDSCAPE
Principal Investigators: Dr. Jeffrey Schloss, Dr. William McDowell, University of New Hampshire
Descriptors: lake, stream, water quality, nutrients, land use

Problem and Research Objectives:

Objectives

• The continued collection and analysis of long-term water quality data in selected watersheds.
• The dissemination of the results of the analysis to cooperating agencies, water managers, educators and the public on a local, statewide and regional basis.
• To offer undergraduate and graduate students the opportunity to gain hands-on experience in water quality sampling, laboratory analysis, data management and interpretation.
• To further document the changing water quality in the College Brook Watershed in the face of land use changes and management efforts.
• To document the effectiveness of constructed BMPs in the Chocorua Lake Watershed
• To determine the next steps for further analysis of long-term data sets.

Principal Findings and Significance:
Ongoing collection of ambient water quality data across the state continues. We added new sites for our statewide lake study. We saw an 8% increase in monitoring samples collected statewide with an over 25% increase in samples collected specifically in the Lakes region of NH: In all, we saw the addition of 3 new lakes, and the expansion of programs on 9 other lakes with the addition of 11 new or reactivated sampling sites (Table 1). We provided training for 29 new volunteer monitors!

* LWA= Lake Winnipesaukee Association

The Lake Chocorua BMP Evaluation Study disclosed that a significant reduction in the phosphous loading was due to the road drainage mitigation techniques. The combination of the use of plunge pools, diversions to settling areas and a large collecting swale reduced loadings during storm events by 82-94%. The P concentration range from the runoff was also reduced significantly (pre-range of 34 to 281ppb post range of 13 to 23 ppb). Further monitoring will be done to capture spring runoff and additional storm events in the upcoming year.

Analysis of the Squam Lake Watershed nutrient budget disclosed that subwatersheds with construction activity or active agriculture were the largest contributor of phosphorous on an aerial basis. Further study will be done on analysis of the effect of riparian buffer extent and updated nutrient export coefficients will be calculated in the upcoming year.