Environmental Monitoring Program

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Meteorological Data (Daily, Hourly, UV)

Meteorological and solar radiation data are collected using a Campbell Scientific, Inc. datalogger (21X 1M 1987-14 September 1993, 21XL 14 September 1993- 12 October 1999, 23X 12 Oct. 1999-December 2011, CR3000 Dec. 2011-present). All sensors are sampled every 2 seconds and all data except ultraviolet radiation data are summarized hourly and at the end of every 24-hour period. Ultraviolet radiation data are averaged at the end of every 3 minutes. Hourly summary data units are Eastern Standard Time (EST), where 100 is midnight to 1 a.m. EST and 2400 is 11 p.m. to midnight EST.

Hydrological Data

Stream gauging and temperature equipment is located on the East Branch of Wappinger Creek in the Fern Glen on the Cary Institute property. GPS coordinates for the site are N41.78707, W73.73317. The stream is a tributary to the main branch of Wappinger Creek, which flows into the Hudson River at Wappingers Falls. Approximately 1.6 km upstream from the gauging station is the Village of Millbrook sewage treatment plant. In addition to the sewage treatment plant, Dietrich Pond and its associated dam can influence the stream at the gauging station. The gauging equipment is situated in a stilling well, which is located on the leeward side of an old bridge abutment. Stream height is monitored using a float and pulley system with a graduated tape (formerly a wire). The pulley is connected to an incremental shaft encoder, which is monitored using a datalogger. Stream temperature is monitored using a temperature sensor, which sits on the bed of the stream near the stilling well. Instantaneous height and temperature measurements are recorded and stored every fifteen minutes. Rating curves for estimating stream discharge were developed in 1987-1988, 1993-1994, 1996, 1997-1998 and 2003-2005 with periodic points checked in intervening years.

Stream height was measured between 1986 and 1991 using a Leupold and Stevens, Inc. total flow meter (model 61R) connected to a float and pulley. Stream temperature was measured between 1987 and 1993 using a Weksler Instruments Corporation, Temperature Chart Recorder, 10 inch. Data collected prior to 1993 can be made available on request. In 1993, we began continuous collection of stream height and temperature using a Handar, Inc. 570A Data Acquisition System with an incremental shaft encoder (model 436A) and a water temperature sensor (Handar, Inc., model 433FN 1993-Sept. 2003, Campbell Scientific model CS547A May 2005-present). Stream height is checked weekly with a fixed staff gauge (Sept. 1997-present) and with a graduated tape on the pulley (July 2002-present). The Handar 570A datalogger was replaced with a Campbell Scientific CR510 datalogger in September 2003. We began continuous stream conductivity measurements in May 2005 using a Campbell Scientific CS547A conductivity and temperature probe.

Rating Curve Equations:

y = discharge (m^3/s) x = stage height (cm)
1993-1994 y = 0.0009x^2 + 0.0159x + 0.1192 R^2 = 0.9923, n=6
1996 y = 0.0024x^2 - 0.0168x + 0.1444 R^2 = 1, n=3
1997-1998 y = 0.0009x^2 - 0.0036x + 0.0557 R^2 = 0.9934, n=6
2001-2005 y = 0.0018x^2 - 0.0292x + 0.1178 R^2 = 0.9876, n=7

Precipitation Chemistry

Precipitation samples are collected using the wet side of an automatic wet-dry collector. The collector uses a moisture sensor that causes a motor to remove a cover from a clean bucket when it senses precipitated moisture. Samples are collected on an event basis; an event is defined as continuous precipitation that has not been interrupted by more than 6-hours. At the end of an event, the sample is collected, weighed, and transferred to a labeled sample bottle. If the sample is frozen, it is allowed to sit at room temperature until the entire sample is melted. After the sample is bottled, it is analyzed at the Cary Institute analytical laboratory for pH, sulfate, nitrate, ammonium, phosphate, chloride, sodium, calcium, magnesium and potassium ions. See Table 1 for analytical methods. If the quantity of sample is insufficient for all of these analyses, as many of the analyses as possible are completed with preference given to pH, sulfate, nitrate and ammonium in that order.

In 1999 we changed the sample-handling protocol as follows. A 60-ml aliquot of sample is preserved with 2 drops of chloroform and refrigerated. This aliquot is analyzed for phosphate, ammonium, and nitrate. Comparisons of phosphate, ammonium and nitrate were made for one year between samples treated with chloroform and samples left untreated. There was no significant difference between treated and untreated samples for ammonium and nitrate, but phosphate was higher in samples treated with chloroform. We made no adjustments to data collected prior to 1999. For estimation of monthly volume-weighted mean concentrations and total deposition, values that are below detection limits are replaced with one half of the detection limit. Datasets include monthly volume-weighted means and monthly total deposition. For a description of variables, see list with units below.

Low-Volume Filter Pack Air Chemistry

Aerosol concentrations, HNO3 and SO2 are sampled using Teflon filter packs. Three 47-mm diameter filters are placed in each filter pack: a Teflon filter (1988-February 2004 Zefluor, 2 micron, Gelman Sciences, Inc.; February 2004-present Whatman, 1 micron) for collection of aerosols, a Nylasorb 1 micron nylon filter (Gelman Sciences, Inc.) for collection of HNO3 vapor and a potassium carbonate-coated cellulose filter for collection of SO2. The cellulose filters are Whatman 41, >20-25 µm particle retention, coarse porosity, ASTM, 12 sec, (Whatman number 1441-047). The cellulose filters are cleaned before coating by rinsing and soaking overnight in double-deionized water. The three filters are placed in line so that the Teflon filter is exposed to incoming ambient air first, the nylon filter second and the carbonate filter last. The filter packs are placed in an inverted stainless steel pot (from 1988 - July 1993 it was an inverted plastic funnel) on a tower approximately 10 m above a mowed grass surface. A continuous flow of air is drawn through the filter pack at 3.00 lpm using a Gast, Inc. oil-less vacuum pump (model 1031, upgraded to model 1531-107B-6288 in 1998), which is regulated by a mass flow controller (Tylan General Inc., model FC280V, upgraded to model FC2604S in 1998 and to Aalborg model GFC 17 in September 2002). When the mass flow controller is off line for any reason, either a needle valve or another mass flow controller regulates flow. During this time, flow is measured using a rotameter (Gilmont Instruments, Inc., or Scienceware®), and the flow measurements are corrected for instantaneous temperature and atmospheric pressure. Clean filter packs are exchanged for exposed ones every Tuesday.

The Teflon filters are extracted in 50 ml of double deionized water for 24 hours in the dark at 2 degrees C after sonication for 15 minutes. The solution is then decanted into sample bottles and analyzed at the Cary Institute for pH, nitrate, sulfate, ammonium, phosphate, Chloride, Sodium, Calcium, Magnesium and Potassium for determination of aerosol chemistry (see Table 1 for analytical methods). Nitric acid vapor is determined by extracting each nylon filter in 50 ml of a mixture of NaHCO3 (0.28 M) and Na2CO3 (0.22 M) diluted 1:100 with double deionized water. The filters are sonicated for 15 minutes and then refrigerated for 24 hours before decanting the solutions and analyzing them for nitrate and sulfate. Sulfur dioxide is determined by extracting the carbonate-coated filters in 50 ml of double deionized water with 2 drops of hydrogen peroxide. The filters are sonicated and extracted as described above and the resulting solution is analyzed for sulfate. Concentrations of sulfate from the nylon and carbonate filters are added to determine total sulfur dioxide. After 1993 all sample extractions were preserved with 2 drops of chloroform.

Using the total amount of time that each filter was exposed and the average flow rate for the week, weekly concentrations of each component are calculated. For samples that returned less than detection limit concentrations, one half the detection limit is used to calculate air concentrations. Deposition velocities are estimated using a multi-layer dry deposition model (Meyers, T.P., Finkelstein, P., Clarke, J., Ellestad, T.G., Sims, P.F. 1998. A multilayer model for inferring dry deposition using standard meteorological measurements. Journal of Geophysical Research 103: 22645-22661). Weekly average deposition velocities are combined with weekly concentrations to estimate weekly fluxes. Data sets include monthly mean air concentrations, monthly mean deposition velocities and monthly total deposition. For a descriptions of variables, see variable list with units below.

Stream Chemistry

Stream samples are collected at the end of every month at two sites on the East Branch of Wappinger Creek at the Cary Institute of Ecosystem Studies. Before 1996, samples were collected at four sites. Redundancy in the data and cost of analysis prompted us to discontinue collecting samples at two of the sites. The two remaining sites are Site 2 (Fern Glen, GPS coordinates N41.78707, W73.73317) and Site 4 (Lowlands, GPS coordinates N41.79235, W73.74937). Sample collection began in November 1985 (Site 2) and January 1985 (Site 4). Samples are collected when the stream is as near base flow as possible, however, base flow varies seasonally and is generally higher in winter than summer. The samples are analyzed at the Cary Institute Analytical Laboratory for pH, conductivity, nitrate, sulfate, ammonium, phosphate, chloride, sodium, calcium, magnesium, potassium and silica and DOC (see Table 1 for analytical methods).

Samples collected between 1985 and 1998 were not preserved in any way and were stored in the light at room temperature before analyses were completed. Samples from January 1999 onward are preserved as follows. Samples are divided into three aliquots, one aliquot is filtered and preserved with Optima grade concentrated sulfuric acid (0.5 ml per 125 ml of sample) for analysis of nitrate, ammonium, phosphate, and DOC. Another aliquot is filtered and analyzed for sulfate, chloride, sodium, calcium, magnesium, potassium and silica. Silica analyses are completed within 4 days of sample collection. The third aliquot is untreated and analyzed for conductivity and pH.