Groundwater Research Group

Jennie Munster

jmunster@notes2.cc.sunysb.edu 

My research interest are in understanding nitrate and perchlorate contamination in Suffolk County groundwater. The approach I am using can be applied to other areas as well, especially areas with similar hydrogeology and climate conditions. 

For my master's thesis I used major element chemistry to determine sources of nitrate contamination. This data showed a clear relationship between nitrate source and land use. The data allowed estimates but do not allow precise measurements of mixing proportions due to the large range in source concentrations. My master's work also measured nitrate concentrations beneath maintained turfgrass systems of different fertilizer practice and site/soil properties. We concluded that nitrate leaching was less dependent on type of fertilizer used but more dependent on infiltration rate, soil organic matter, the age of the turfgrass and thatch thickness.

For my Ph.D. work I plan to use more sophisticated tools to identify nitrate contamination, namely Br, I, Cl, B concentrations and boron isotopes. High precision measurements of these elements should reduce the concentration ranges in the sources. These elements are useful tracers since they are predominantly conservative in the Long Island aquifer. 
In addition I will be explore probable non-point sources of perchlorate by measuring concentrations of rain water, soil water influenced by fertilizer, wastewater and road runoff. 

Please take the time to read in more detail about my project, and feel free to contact me with any questions, concerns, suggestions or comments. 

Nitrate

My research on nitrate has been co-advised by Marty Petrovic in the Department of Horticulture at Cornell University and Henry Bokuniewicz in the Marine Sciences Department at Stony Brook University. 

The current dirking water standard set by the Environmental Protection Agency (EPA) is 10 ppm NO₃-N. It is know to be toxic to young infants above this level by causing blue baby syndrome. Health implications for children and adults are less well understood.

The main sources of nitrate in urban areas are fertilizer used on turfgrass and leaching from septic tank/cesspool systems.

Turfgrass leaching

Figure 1 Map of the six sampling locations set up to understand nitrate leaching below maintained turfgrass sites. The sites are sampled monthly and have been since January 2003 (except forest/native sites). 

Figure 1 is a map of Suffolk County showing the 10 sites we are currently sampling. All sites have maintained lawns; four are treated with organic fertilizer, two are treated with chemical fertilizer, two receive no fertilization and two are native vegetation. The type of treatment has developed over time (Table 1) as we learned more about the study. Initially we installed soil water samples, called suction lysimeters, at 100 cm below turfgrass sites treated with chemical or organic fertilizer to test the difference in nitrate leaching. After the first two years of data we noticed that site properties, i.e. infiltration rate, thatch thickness, controlled the nitrate concentration at 100 cm more than type of fertilizer used. In the beginning of 2005 we split three of the lawns in half and treated one side with chemical fertilizer and one site with organic fertilizer and added E.Hampton as an additional control site. We also installed rain gauges in 2005 at each of the sites since precipitation can vary around 6 cm locally. 
 
                            Table 1. Summary of site treatment types

Figure 2. Nitrate as nitrogen data collected at 100 cm below the surface of treated turfgrass sites and control sites from January 2002 to September 2005. Yellow data points are time of fertilization or compost treatment.

Data for most of the study is shown in Figure 2. Check out my abstracts and master's thesis on the publication page for interpretation of this data.

Wastewater

Two-thirds of the population in Suffolk County operate on private wastewater systems (Figure 3). Those constructed after the mid 1970's include both a septic tank and cesspool system, where older ones usually only have a cesspool. 

Figure 3. Private wastewater system.

Surprisingly wastewater did not contribute more nitrate than turfgrass fertilizer (Table 2) as a function of land use. Calculated estimates are based on a water budget for a given groundwater well capture zone as well as mass balance calculations using nitrate, chloride and sulfate concentrations.  

Table 2. Calculated estimates of nitrate sources as a function of primary land use in the groundwater

Perchlorate

Perchlorate is an emerging contaminant in Suffolk County. There is an increasingly amount of wells which test positive for perchlorate that do not have a know anthropogenic source near by. Due to this fact non-point sources must be prevalent and need to be examined. I plan to examine possible non point sources such as rain water, soil water influenced by fertilizer, wastewater and road runoff. 

Background

Perchlorate is a strong oxidizer and is commonly used in explosives such as rocket propellant and fireworks. Perchlorate is mobile in the environment as it does not readily sorb onto surfaces or react in the natural environment. Perchlorate has been shown to be reduced by specific microbiological communities under conditions with little dissolved oxygen and high organic matter. Molybdate is a nutritional requirement for such reduction. 

In 2001 the EPA required monitoring of perchlorate in all large public water systems and some small systems. As of Sept. 2004 perchlorate releases have been confirmed in 35 states. Today over 11 millions people have perchlorate in their public drinking water supplies at concentration of 4 ppb or higher. New York state has set a guidance level of 5 ppb and an action level of 18 ppb. Perchlorate has been detected in food sources such as lettuce. 

Perchlorate can affect the thyroid function because it is an ion that competitively inhibits the transport of iodide into the thyroid. The EPA recommends a maximum level of 0.007 mg/kg/day assuming a 70-kg body weight. 

Sources of perchlorate include nitrate fertilizers from Chile, desert deposits, potash, atmospheric deposits and anthropogenic sources which include soil rocket propellant, industrial and pyrotechnics. 

Natural perchlorate is found in arid to semi-arid climate with semi-permeable to impermeable organic poor soils/sediments. Mechanism to form natural perchlorate are actively being studied but likely include a source of Cl exposure to ozone and/or UV light. Accumulation is similar to Cl and NO₃ and it is thought that a long term atmospheric deposition plus storage in dry desert locations lead to large deposit of perchlorate and a flushing event such as irrigation or large storm will transport this perchlorate to the groundwater. 

Initial results

Initial samples shown that some rain water, soil water and wastewater test positive for perchlorate. We do not have enough samples yet to say anything about trends in the data or sources of perchlorate. These samples have been analyzed by Todd Anderson at TIEHH using EPA method 314.1 "Determination of perchlorate in drinking water using inline column concentration/matrix elimination ion chromatography with suppressed conductivity detection." 

Proposed method for testing road runoff

It has been shown that one un burnt road flare is enough to contaminate 240,000 gallons of groundwater to 4 ppb perchlorate. I plan to locate two intersections in Suffolk County with high accident ratings and set up storm water samplers in a near by recharge basin to capture road runoff from these areas.

This perchlorate study is still in the initial stages details will be updated this spring.  

Last updated: April 12, 2006.