Water Tracing
Monitoring and Sampling Protocol for Karst Water Tracing Studies
Fluorescent tracer dyes all have some sorbtive tendencies and are subject to photochemical decay. The samples are usually stable for a period of several weeks if stored in the dark and not allowed to freeze or be subjected to excessive heat (over 90 degrees F). If our clients do the sampling, they may use any sample ID system that they choose. Some clients do not identify the sample locations to us and may include a “spiked” sample at random as part of their quality control. Samples may be kept refrigerated and shipped with cold packs. This is not usually needed, but all samples should be handled, stored, and shipped in a consistent manner. We will also need about a 1 gram or 1 ml sample of the undiluted tracer dyes that were injected – this is especially important if the recovery tracer concentrations are to be quantified. Some sampling of the monitoring sites prior to injection of the dyes is necessary to establish the natural fluorescent “background” at each site. Passive detectors (traps) should be left for about one week and then changed at the time the test is started.
Monitoring Locations The best places to monitor for tracer dyes are springs and cave streams. Actively pumping water wells may also be monitored. We do not recommend sampling unused wells or static monitoring wells in most karst studies. The direct water samples should be collected at points where ground water is believed to be rising and at points with good flow. Avoid sampling in eddies or in long deep pools if possible. Try and avoid locations with strong direct sunlight. We recommend placing some flagging with the station ID on a tree near the station, but not flagging the exact position of the detectors. Be sure to remember exactly where each detector is in the stream channel (photos may be helpful).
Sampling Water samples should be taken in glass or hard clear plastic bottles. Rinse the bottle twice and take the sample on the third filling. A small amount of air in the sample is acceptable. The sample size should be at least 10 ml. The sampling interval may range from about 15 minutes to 12 hours for most quantitative tests. Store the samples in the dark and avoid temperature extremes. The results of the fluorometric analysis of water samples may be quantified to express the concentration of dye present in the sample.
Passive detectors (packets of activated carbon or cotton balls) should be placed in moderate flow and may be concealed to prevent tampering. The packets (traps) may be anchored to rocks or metal railroad spikes with copper wire. Anticipate changes in water levels so the traps will remain submerged if the water drops and are still retrievable if it rises. The traps should be suspended somewhat above the streambed for muddy or silt channels, but may be directly on the streambed and covered by a rock for rocky channels with good flow. Traps used to sample water wells are usually inserted into a special holder attached to the end of a garden hose and the water is kept on at a trickle (about 0.2 gpm) for the duration of the study. The traps should be in shaded locations – try and avoid exposure to direct sunlight. The packets may be changed at intervals of one day to two weeks and placed in individual ziplock bags and stored in the dark. Remember that dye concentrations based on the analysis of the passive detectors are not really quantitative. The detectors collect and concentrate the dye over a period of time but results do not reveal the maximum dye concentration or anything about the percentage of the injected tracer recovered at the site. These qualitative tests can only confirm a connection between the injection site and the recovery point(s). The results are “positive” or “non detect”.
Shipping Samples may be shipped to us by any usual carrier. Enclose the “chain of custody” form if applicable. Protect from freezing and breakage of glass bottles. If shipping by UPS or Fed Ex, address:
Environmental Data
William K. Jones
718 Chimney Run Farm Road, Box 356
Warm Springs, VA 24484
540-839-3377
If using the US Postal Service:
William K. Jones
PO Box 356
Warm Springs, VA 24484
Monitoring and Sampling Protocol for Karst Water Tracing Studies
Fluorescent tracer dyes all have some sorbtive tendencies and are subject to photochemical decay. The samples are usually stable for a period of several weeks if stored in the dark and not allowed to freeze or be subjected to excessive heat (over 90 degrees F). If our clients do the sampling, they may use any sample ID system that they choose. Some clients do not identify the sample locations to us and may include a “spiked” sample at random as part of their quality control. Samples may be kept refrigerated and shipped with cold packs. This is not usually needed, but all samples should be handled, stored, and shipped in a consistent manner. We will also need about a 1 gram or 1 ml sample of the undiluted tracer dyes that were injected – this is especially important if the recovery tracer concentrations are to be quantified. Some sampling of the monitoring sites prior to injection of the dyes is necessary to establish the natural fluorescent “background” at each site. Passive detectors (traps) should be left for about one week and then changed at the time the test is started.
Monitoring Locations The best places to monitor for tracer dyes are springs and cave streams. Actively pumping water wells may also be monitored. We do not recommend sampling unused wells or static monitoring wells in most karst studies. The direct water samples should be collected at points where ground water is believed to be rising and at points with good flow. Avoid sampling in eddies or in long deep pools if possible. Try and avoid locations with strong direct sunlight. We recommend placing some flagging with the station ID on a tree near the station, but not flagging the exact position of the detectors. Be sure to remember exactly where each detector is in the stream channel (photos may be helpful).
Sampling Water samples should be taken in glass or hard clear plastic bottles. Rinse the bottle twice and take the sample on the third filling. A small amount of air in the sample is acceptable. The sample size should be at least 10 ml. The sampling interval may range from about 15 minutes to 12 hours for most quantitative tests. Store the samples in the dark and avoid temperature extremes. The results of the fluorometric analysis of water samples may be quantified to express the concentration of dye present in the sample.
Passive detectors (packets of activated carbon or cotton balls) should be placed in moderate flow and may be concealed to prevent tampering. The packets (traps) may be anchored to rocks or metal railroad spikes with copper wire. Anticipate changes in water levels so the traps will remain submerged if the water drops and are still retrievable if it rises. The traps should be suspended somewhat above the streambed for muddy or silt channels, but may be directly on the streambed and covered by a rock for rocky channels with good flow. Traps used to sample water wells are usually inserted into a special holder attached to the end of a garden hose and the water is kept on at a trickle (about 0.2 gpm) for the duration of the study. The traps should be in shaded locations – try and avoid exposure to direct sunlight. The packets may be changed at intervals of one day to two weeks and placed in individual ziplock bags and stored in the dark. Remember that dye concentrations based on the analysis of the passive detectors are not really quantitative. The detectors collect and concentrate the dye over a period of time but results do not reveal the maximum dye concentration or anything about the percentage of the injected tracer recovered at the site. These qualitative tests can only confirm a connection between the injection site and the recovery point(s). The results are “positive” or “non detect”.
Shipping Samples may be shipped to us by any usual carrier. Enclose the “chain of custody” form if applicable. Protect from freezing and breakage of glass bottles. If shipping by UPS or Fed Ex, address:
Environmental Data
William K. Jones
718 Chimney Run Farm Road, Box 356
Warm Springs, VA 24484
540-839-3377
If using the US Postal Service:
William K. Jones
PO Box 356
Warm Springs, VA 24484
Laboratory Analysis of Water and Carbon Samples
The presence and relative concentrations of tracer dyes are measured using a Shimadzu RF5000U recording spectrofluorophotometer. To determine the presence of the tracer dyes of interest, a synchronous scan is run of each sample using a 20 nm separation between the excitation and emission wavelengths. The output curves show the emission spectra or “curve” generated by this scan and the height of the curve at the appropriate wavelength is relative fluorescent intensity and is linearly related to the concentration of the dye in the sample. In general, a sample is considered positive for the presence of a dye when:
Dye is recovered from activated carbon (charcoal traps) by elution of the charcoal in a basic alcohol solution for about one hour and then pouring the elutant into a cuvet and running the analysis on the instrument as is done for water samples. Note that the characteristic emission peaks for the dyes in elutants are slightly different than for the same dyes in water. The typically used eluent is 5% KOH in 70% isopropyl alcohol. Emission peaks in water samples are about 516 nm for fluorescein and 576.8 nm for rhodamine. Emission peaks in elutant are about 522.8 nm for fluorescein and 574 nm for rhodamine.
Results of the analysis are reported as positive (P), none detected (ND), or (?) if a characteristic curve but at a lower apparent concentration developed for the dyes of interest. Instrument readings represent a measure of the relative fluorescent intensity of the sample at the expected spectra maximum for the dye of interest. This is the “height” of the spectra curve. These readings are generally linearly related to the concentration of the dye in the water sample, but a series of laboratory standards at different concentration must be prepared and analyzed to make a direct conversion between instrument readings and dye concentration.
Many variables including exposure time to the dye cloud, relative flow of water at the monitoring station, and dye concentration around the trap will all affect the apparent extracted concentrations of dyes in elutants. Use caution when comparing the relative dye concentrations from different stations based on the recovery concentrations from carbon. The results from the carbon traps are qualitative in nature and are best interpreted as “positive” or “none detected”.
The presence and relative concentrations of tracer dyes are measured using a Shimadzu RF5000U recording spectrofluorophotometer. To determine the presence of the tracer dyes of interest, a synchronous scan is run of each sample using a 20 nm separation between the excitation and emission wavelengths. The output curves show the emission spectra or “curve” generated by this scan and the height of the curve at the appropriate wavelength is relative fluorescent intensity and is linearly related to the concentration of the dye in the sample. In general, a sample is considered positive for the presence of a dye when:
- The spectra are typical for the dye(s) (emission peak wavelengths and shape of the spectra curves are comparable to laboratory standards).
- The relative fluorescent intensity of the sample is significantly above background fluorescence at the appropriate emission wavelengths. Environmental Data normally requires a reading three times background from carbon samples and two times background in water samples to consider a result positive (for samples with relatively low background fluorescence). However, if a typical spectra curve for a tracer is generated at a low apparent dye concentration the result will be interpreted as ambiguous and marked by a “?”. This is extremely conservative and makes the dye concentration required for a “positive” test to be equal to or greater than about 0.1 ppb (µg/l) from carbon samples and 0.04 ppb for water samples. Also note that in some tests with multiple tracer dyes, one dye may have a much stronger fluorescent signature than the other dyes present in the sample and cause the weaker dyes to appear as a “bump” on the shoulder of the emission spectra of the stronger dye.
Dye is recovered from activated carbon (charcoal traps) by elution of the charcoal in a basic alcohol solution for about one hour and then pouring the elutant into a cuvet and running the analysis on the instrument as is done for water samples. Note that the characteristic emission peaks for the dyes in elutants are slightly different than for the same dyes in water. The typically used eluent is 5% KOH in 70% isopropyl alcohol. Emission peaks in water samples are about 516 nm for fluorescein and 576.8 nm for rhodamine. Emission peaks in elutant are about 522.8 nm for fluorescein and 574 nm for rhodamine.
Results of the analysis are reported as positive (P), none detected (ND), or (?) if a characteristic curve but at a lower apparent concentration developed for the dyes of interest. Instrument readings represent a measure of the relative fluorescent intensity of the sample at the expected spectra maximum for the dye of interest. This is the “height” of the spectra curve. These readings are generally linearly related to the concentration of the dye in the water sample, but a series of laboratory standards at different concentration must be prepared and analyzed to make a direct conversion between instrument readings and dye concentration.
Many variables including exposure time to the dye cloud, relative flow of water at the monitoring station, and dye concentration around the trap will all affect the apparent extracted concentrations of dyes in elutants. Use caution when comparing the relative dye concentrations from different stations based on the recovery concentrations from carbon. The results from the carbon traps are qualitative in nature and are best interpreted as “positive” or “none detected”.