The recent history of the Chester River has been one of change and population growth. The population of the two counties that surround the Chester has grown phenomenally in the past century: from a total of 37,150 in 1900, to a total of 62,448 in 2002 (Maryland Department of Planning). Land use in the estuary remains primarily agricultural with nearly half (200,000 acres) of the total land area of the two counties being used for small grain farming (corn and soybeans). Small grain farming is primarily a phenomenon of the last half of the past century: just after World War II only 50,000 acres were devoted to grains, the remaining acreage was primarily devoted to small dairy farms. It is believed that this change in landuse has impacted the water quality in the Chester River.

The Chester River has been identified by a number of surveys as suffering from an overabundance of nutrients, primarily nitrogen. Among the results of this overabundance are seasonal algal blooms, seasonal areas of low dissolved oxygen, and declining acreage of subaquatic vegetation. In 1993, The Chester River Association (a citizens 501c-3 group formed as an advocate for the River) instituted a water quality monitoring program at a number of sites on the Chester River to develop a long term data record. Monitoring of water quality in the river was initiated in 1993, and the dataset can be seen at the Chester River Association website.

The parameters monitored include pH, dissolved oxygen, secchi depth, salinity and nitrate nitrogen. Recognizing the importance of identifying the different sources of nitrogen in the watershed, a rainfall nitrate/nitrite monitoring program was instituted at a single station (Site "A") in 2003 and expanded to a second station in 2004 (Site "B"). In addition, a subset of the samples from sSite A was also tested for pH and ammonia-nitrogen. Other major sources of nitrogen in the watershed include agriculture, point source sewage treatment plants, and non-point diffuse sources such as septic systems.

Monitoring results indicate that aerial deposition of nitrate and ammonia nitrogen are significance in this watershed when compared to other sources of nitrogen. The results establish a lower limit for the total nitrogen deposited to the watershed from aerial phenomena that ranks it of equal importance to point source wastewater treatment plants discharges of nitrogen.

See the Related Publications section below for sources of information on the monitoring program.

Precipitation/Air Sampling and Analysis

A rainfall nitrate/nitrite monitoring program was instituted at a single station (Site "A") in 2003 and expanded to a second station in 2004 (Site "B"). Site A is located approximately 5 miles south-south-west of Chestertown, MD (N39 09' 25", W76 06' 45") in an area in which the land use is primarily agricultural and forest with light residential use. Prevailing winds range from southwest in late spring through early fall to northwest the remainder of the year. The nearest major highways (U.S 301 and U. S. 50) lie approximately 25 miles to the northeast and east and 15 miles to the south and east respectively. The sampling site is located on the edge of a mown field of 4 acres surrounded by wooded areas. This site is located in the middle Chester River watershed. Site B, added in 2004, is located approximately 3 miles east of Millington, MD (N39 14' 30", W75 47' 25") in an area of like land use. This site is located in the upper Chester River watershed and is in close proximity to one major highway (U. S. 301~ 3 miles to the west).

Rainfall samples are collected in a sampling device that consists of a sample bottle topped with a plastic funnel of 3" diameter. The funnel is used to magnify small rain events so that a sample of at least 10 ml is obtained for each rainfall event. Samples are analyzed for nitrate+nitrite nitrogen using the cadmium reduction method in which cadmium powder is used to reduce nitrate present to nitrite, the total of which is determined by diazotization of sulfanilamide and nitrite followed by coupling with N-(1naphthyl)-ethylenediamine dihydrochloride. This forms a bright azo dye the concentration of which is proportional to the amount of nitrite present. This is measured colorimetrically with a Lamotte Company "Smart Colorimeter" that photoelectrically determines the amount of color present. The working range of this method is 0-3.0 ppm nitrate-nitrogen. Ammonia nitrogen is measured by the salicylate method, in which salicylate and ammonia at high pH and in the presence of a chlorine donor and an iron catalyst form a blue indophenol dye in proportion to the ammonia present in the sample. The amount of dye present is determined by the Smart Colorimeter, with the working range 0-1.0 ppm ammonia nitrogen. Out of range samples are diluted with a fixed amount of distilled water and retested. The Lamotte Smart Colorimeter is an EPA-Accepted instrument (Lamotte Company Smart Colorimeter Operators Manual).

Whenever possible samples are analyzed within 24 hours of collection. When necessary, samples are stored at approximately 4° C and analysis is performed later. Samples are never stored longer than 48 hours. Rainfall amounts are simultaneously monitored and recorded, and combined with the chemical analysis to produce a nitrate nitrogen loading rate in pounds per acre per year.

The techniques and methods detailed here do not account for all aerial nitrogen depositions into the watershed. Neither ammonia nitrogen (on a regular basis) nor organic nitrogen is measured, though it is hoped to add ammonia nitrogen tests in 2004. Additionally, a significant amount of nitrogen deposition into the watershed is dry deposition, not associated with rainfall events. The mobility of the nitrate ion in the watershed however, makes it one of the most important nitrogen species to quantify.

Quality Assurance (QA)

Quality control is maintained by adhering to the following protocols. To minimize contamination by dry deposition, washed samplers are not put out until just prior to rainfall events are predicted. Samplers are always placed at the same spot-an open area at each station, away from trees and buildings. To ensure the reliability of the tester and the equipment, standard samples are run at periodic intervals under the supervision of technicians from Lamotte Company (the manufacturer of the equipment), based in Chestertown, MD, and they service the equipment as needed. They have been an integral part of the project since its inception.

Results

Results to date indicate that wet deposition of nitrate/nitrite to the Chester River watershed is 2.6 pounds of nitrogen/acre/year when adjusted to a normal rainfall year (43"). With a surface area of 35,583 acres, nearly 93,000 pounds of nitrogen/year are deposited directly into the Chester River as a result. An additional amount (though probably significant, due to the mobility of the nitrate ion) enters the river through surface runoff and groundwater infiltration from deposition on the 281,600 acres of land in the watershed. This is of the same magnitude as the loading from point source sewage treatment plants to the Chester River. Using data from the year 2000, nearly 54,000 lbs. of nitrogen were released from the nine treatment plants that discharge directly into the Chester River and 87,900 lbs. were released from one additional plant that discharges just beyond the mouth of the river (data from the Maryland Department of the Environment). Limited results to date indicate that ammonia-nitrogen deposition may be of the same magnitude as nitrate/nitrite deposition. It is clear that when wet deposition of ammonia and organic nitrogen, and dry deposition of all forms of nitrogen are included, aerial deposition of nitrogen would rank even higher as a source of nitrogen to the Chester River.

These findings are significant from a water quality control standpoint in that nitrate/nitrite nitrogen in the atmosphere mostly originate from automobile exhaust and the burning of fossil fuels and may travel several hundred miles before entering the Chester River System. As a rural area the Chester River basin has limited vehicular traffic, with two major highways (U. S. 301 lies to the north and east, U. S. 50 lies to the south and east) and most of the nitrate/nitrite are coming from sources upwind, to the west. As a result, control measures become regional, crossing political boundaries (even state lines), and the people having to take the control measures don't directly benefit. Control measures to alleviate the other major sources of nitrogen into the watershed (agriculture, point sources, non-point sources) can be dealt with on the local level.

Related Publications/Reports

• Chester River Monitoring Program Homepage
• Chester River Continous Monitoring