ASTM F1738-15
(Test Method)Standard Test Method for Determination of Deposition of Aerially Applied Oil Spill Dispersants
Standard Test Method for Determination of Deposition of Aerially Applied Oil Spill Dispersants
SIGNIFICANCE AND USE
3.1 The deposition of an aerially applied dispersant is defined as the amount of an aerially applied dispersant that contacts the surface; whereas, application dosage (frequently referred to as application rate) is the amount of material that is released per unit area by the delivery system. The units of deposition are litres per hectare or U.S. gallons per acre. The deposition may differ from the application dosage (volume of material per unit area) for many reasons, such as, the effects of wind on the spray and the evaporation of the dispersant after it has been released from the aircraft.
3.2 This test method describes the measurement of the ability of a spray system to deposit a dispersant on oil. It is not intended that this test method be used at the time of a spill. These techniques are intended to determine the equipment performance during the development of new systems and after the repair or significant modification of a system.
3.3 The data obtained from the use of this test method can be directly related to the deposition of dispersant on an oil slick, and thus can serve to determine both the dispersant deposition and the droplet size.
3.4 Surrogate deposition and droplet size data can be used as a technical basis for the optimization of dispersant application equipment and its use.
3.5 The choice of a dispersant surrogate may vary, typically water is chosen along with a marker dye.
SCOPE
1.1 This test method covers the measurement of the deposition of an aerially applied dispersant surrogate, typically dyed water, on the surface of the ground or water. The test method of obtaining these measurements is described, and the analysis of the results, in terms of dispersant use, is considered. There are a number of techniques that have been developed, and this test method outlines their application. These measurements can be used to confirm or verify the specifications of a given equipment set, its proper functioning, and use.
1.2 This test method is applicable to systems used with helicopters or airplanes.
1.3 This test method is one of four related to dispersant application systems. Guide F1413_F1413 covers design, Practice F1460/F1460M covers calibration, Test Method F1738 covers deposition, and Guide F1737/F1737M covers the use of the systems. Familiarity with all four standards is recommended.
1.4 There are some exposure and occupational health concerns regarding the methods described. These are not discussed in this test method since they are a function of dispersant formulation. Anyone undertaking such experiments should consult the occupational health experts of the dispersant manufacturer regarding the precautions to be used.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: F1738 − 15
Standard Test Method for
Determination of Deposition of Aerially Applied Oil Spill
Dispersants
This standard is issued under the fixed designation F1738; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2.1 ASTM Standards:
1.1 This test method covers the measurement of the depo-
E642 Practice for Determining Application Rates and Dis-
sitionofanaeriallyapplieddispersantsurrogate,typicallydyed
tribution Patterns from Aerial Application Equipment
water, on the surface of the ground or water. The test method
E1260 Test Method for Determining Liquid Drop Size
of obtaining these measurements is described, and the analysis
Characteristics in a Spray Using Optical Nonimaging
of the results, in terms of dispersant use, is considered. There
Light-Scattering Instruments
are a number of techniques that have been developed, and this
F1413_F1413 Guide for Oil Spill Dispersant Application
testmethodoutlinestheirapplication.Thesemeasurementscan
Equipment: Boom and Nozzle Systems
be used to confirm or verify the specifications of a given
F1460/F1460M Practice for Calibrating Oil Spill Dispersant
equipment set, its proper functioning, and use.
Application Equipment Boom and Nozzle Systems
1.2 This test method is applicable to systems used with
F1737/F1737M Guide for Use of Oil Spill Dispersant Ap-
helicopters or airplanes.
plication Equipment During Spill Response: Boom and
Nozzle Systems
1.3 This test method is one of four related to dispersant
2.2 ASAE/ASABE Standard:
application systems. Guide F1413_F1413 covers design, Prac-
ASAE/ASABE S561.1 (R2013) Procedure for Measuring
tice F1460/F1460M covers calibration, Test Method F1738
Drift Deposits from Ground, Orchard, andAerial Sprayers
covers deposition, and Guide F1737/F1737M covers the use of
- Standard by The American Society of Agricultural and
the systems. Familiarity with all four standards is recom-
Biological Engineers
mended.
3. Significance and Use
1.4 There are some exposure and occupational health con-
cernsregardingthemethodsdescribed.Thesearenotdiscussed
3.1 The deposition of an aerially applied dispersant is
in this test method since they are a function of dispersant
defined as the amount of an aerially applied dispersant that
formulation. Anyone undertaking such experiments should
contacts the surface; whereas, application dosage (frequently
consult the occupational health experts of the dispersant
referred to as application rate) is the amount of material that is
manufacturer regarding the precautions to be used.
released per unit area by the delivery system. The units of
deposition are litres per hectare or U.S. gallons per acre. The
1.5 The values stated in SI units are to be regarded as
deposition may differ from the application dosage (volume of
standard. No other units of measurement are included in this
material per unit area) for many reasons, such as, the effects of
standard.
wind on the spray and the evaporation of the dispersant after it
1.6 This standard does not purport to address all of the
has been released from the aircraft.
safety concerns, if any, associated with its use. It is the
3.2 This test method describes the measurement of the
responsibility of the user of this standard to establish appro-
ability of a spray system to deposit a dispersant on oil. It is not
priate safety and health practices and determine the applica-
intended that this test method be used at the time of a spill.
bility of regulatory limitations prior to use.
These techniques are intended to determine the equipment
1 2
This test method is under the jurisdiction of ASTM Committee F20 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Hazardous Substances and Oil Spill Response and is the direct responsibility of contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Subcommittee F20.13 on Treatment. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved March 1, 2015. Published April 2015. Originally the ASTM website.
approved in 1996. Last previous edition approved in 2010 as F1738 –10. DOI: Available from American Society of Agricultural and Biological Engineers
10.1520/F1738-15. (ASABE), 2950 Niles Road, St. Joseph, MI 49085, http://www.asabe.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1738 − 15
performance during the development of new systems and after group. The data are collected in the memory of the units and
the repair or significant modification of a system. analyzedandprocesseduponcompletionofthetest.Withsome
units, it is possible to conduct multiple tests before recovery of
3.3 The data obtained from the use of this test method can
the data as the data are time-stamped.
be directly related to the deposition of dispersant on an oil
slick, and thus can serve to determine both the dispersant 5.1.2 Coated Cards—Standard cards specifically designed
deposition and the droplet size. for the purpose (for example, Kromekote cards) of known area
are placed in a line perpendicular to the flight path, and
3.4 Surrogate deposition and droplet size data can be used
extendingoveradistance25%greaterthantheexpectedswath
as a technical basis for the optimization of dispersant applica-
width.Thecardstypicallyhavedimensionsof5by7cm.There
tion equipment and its use.
should be about twenty cards placed across the flight path in
3.5 The choice of a dispersant surrogate may vary, typically
order to have an adequate number of sampling points. In a
water is chosen along with a marker dye.
typical experimental setup, the distance between sampling
cards should be greater than one metre and less than three
4. Apparatus and Materials
metres.Thiscriteriamayrequiremoreorlessthantwentycards
4.1 The basic concept is to provide a collection surface on
depending on the spray system being tested. Each card should
which the aerially applied material is deposited.The amount of
be identified by a unique label, indicating its place on the
material and the deposition pattern and its droplet size can be
sampling line and the number of the spray pass. The marking
measured using this surface. Several systems and methods
should be made in such a fashion that it will not be removed by
have been developed, and each has its own advantages and
the dispersant surrogate, as well as Garrco Vision Pink dye
disadvantages.
mixed at a ratio of 1:400 to provide color to the Kromekote
4.2 Thesemeasurementsrequirealarge,flatopenarea(such
cards.Thecardsarekeptcovereduntiljustbeforethesprayrun
as a field or an airport) which is suitable for low-level flying
to reduce the possibility of contamination. The cards are place
and maneuvering. The location should be away from human
in holders if wind can move these cards out of position. The
habitation or environmentally sensitive areas in order to
placement, uncovering, and retrieval of these cards is labor
minimize problems due to noise and drifting spray.
intensive. After the spray run, the cards are collected and
analyzed by machine (Practice E642, ASAE/ASABE S561.1
4.3 These field programs should be conducted under low-
wind conditions in order to minimize drift. Near-surface (R2013). The cards may be used to provide both droplet size,
turbulence due to thermal gradients or atmospheric instability spray width and deposition pattern. This method may also be
cancontributetoavariationintheresults.Thesemeasurements used in combination with other methods to provide data.
cannot be carried out in the presence of precipitation or in
5.1.3 Glass Petri Dishes or Similar Containers—Flat dishes
heavy concentrations of dust.
of known area are placed in a line perpendicular to the flight
path, and extending over a distance 25 % greater than the
4.4 All tests are to be conducted with the flight path in an
upwind direction. The upwind direction is chosen to simplify expected swath width. Dishes of a diameter of 120 to 140 mm
are typically used. There should be about twenty dishes placed
the interpretation of the data and to conform with typical field
practice. It may be necessary to alter the flight path slightly for across the flight path in order to have an adequate number of
changes in wind direction during the course of an experimental sampling points. In a typical experimental setup, the distance
program.
between sampling dishes should be greater than one metre and
less than three metres. This criteria may require more or less
4.5 Itiscommonpracticetouseasurrogate,typicallywater,
thantwentydishesdependingonthespraysystembeingtested.
rather than the dispersant itself. Dye can be added to the water
Each sampling dish should be identified by a unique label,
to provide a measurement target. This dye should respond to
indicating its place on the sampling line and the number of the
the analytical method used in Section 5. Special permission
spray pass. The marking should be made in such a fashion that
wouldberequiredtouseadispersantandpermissionsmayalso
it will not be removed by the dispersant surrogate, or rough
be required to apply a surrogate, and special precautions may
handling. The sampling dishes are kept covered until just
be required to protect and clean the area afterwards.
before the spray run to reduce the possibility of contamination.
5. Deposition Measurement Methods
The placement, uncovering, and retrieval of these dishes is
laborintensive.Afterthesprayrun,thedishesarecollectedand
5.1 These techniques involve the use of a collecting surface
washed with a suitable solvent, such as methanol or hexane, to
of known area and the measurement of the amount and
collect the deposited material. The amount of dye present can
character of the dispersant deposited on this area. A variety of
be determined by using a colorimeter sensitive to the dye used.
systems may be used, such as the following:
The system must be calibrated using a sample of the dyed
5.1.1 Laser Measuring Instrumentation—The use of laser-
surrogate and solvent mixture for that experimental pass. For
based measuring techniques is becoming more common and
thesemeasurements,caremustbetakentoensurethatthesame
can provide both droplet size and deposition distribution. This
dilution factors are used for both the calibration and material
method employs laser scattering devices deployed in an array
on a flat surface (Test Method E1260), the number of these from the sampling dishes, since the measurement instruments
are only linear over about an order of magnitude of concen-
devices depends on the specified horizontal range of these
devices and the amount of surface coverage desired by the test tration. From these sets of data, the amount of material
F1738 − 15
deposited on the surface in any units required, such as momentum. It is the momentum that is critical for the
litres/hectare (U.S. gal/acre), can be calculated. dispersant, since this determines the probability of the droplet
penetrating the slick.
5.1.4 Metal Troughs—A variation of the sampling dish is a
V-shaped metal trough, divided into sections and placed
6.2 Most techniques developed for pesticide drop-size mea-
perpendicular to the flight path. Each section is about two
surements fail since the deposition for dispersants is several
metres long with a cross section of about 6 cm. A number of
orders of magnitude greater than those used for pesticides.
troughs, connected end-to-end, are used to cover a length of
When these techniques are used for dispersants, the flux of
about25 %greaterthanthetotalspraywidth.Afterasprayrun,
droplets are so dense that they overlap, and thus, individual
the troughs are washed with a solvent, such as methanol or particles cannot be measured.
hexane, and the eluent from each section is collected for
6.3 There are a number of methods that have been used in
analysis. The concept is similar to that of the glass dishes, but
the measurement of drop size. One modern method is to use
this system has the advantage of sampling the total spray
laser particle instrumentation which can directly provide drop-
width, and providing an average dose over the discrete section.
let diameter along with statistics on these. Traditional methods
Onemajoradvantageofthetroughsisthattheyremaininplace
oftenusepaperastheabsorbingmaterial.Onecommonsystem
during a number of experimental runs, thus reducing the time
uses specially coated cards (Kromekote). There are two prod-
between runs. This allows for more runs per day.
ucts that are typically used: a water-sensitive paper, that is
5.1.5 String Measurement—The string method is often used
yellow in color and stains blue when exposed to water and the
to provide information on spray width and pattern. This
other is white which stains blue when exposed to organic
method uses a cord or string that is either stretched across the
materials. These materials can be used to measure spray
width of the spray or is supported on a series of stands. Except distributions and swath widths as well as droplet size. Special
for very narrow-width application systems, the string is sup-
paper that is used by the printing industry for color reproduc-
ported about every two metres by a stand. The surrogate is tion can be used for the same purpose.Another system collects
Rhodamine WT dye mixed with water at a ratio of about
the drops on rolls of paper tape. All such methods require the
1:7500. The surrogate is collected by the string, and thus the calibration of the detection medium in terms of the relationship
needed data are obtained. Since the cross section of the string
between droplet size and the drop area on the material. This is
is much smaller than that of the Petri dish or trough, more dye done in the laboratory.
may be needed in the sprayed dispersant. The string is then
6.4 Using the paper method drop size can be determined by
allowed to dry.The amount of material that the string collected
measuring the size of the projected image of the drop.
is determined by a fluorometric or colormetric technique.
Counting the drops and determining the drop size can be done
Automated devices are available for this application. This
either manually or using electronic image analysis systems. A
method measures the relative deposition only, and not the
large number of drops must be examined in order to achieve
absolute deposition.
good statistics.
5.1.6 Data Determination—The data collected from these
6.5 T
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F1738 − 10 F1738 − 15
Standard Test Method for
Determination of Deposition of Aerially Applied Oil Spill
Dispersants
This standard is issued under the fixed designation F1738; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the measurement of the deposition of an aerially applied dispersant surrogate, typically dyed water,
on the surface of the ground or water. The test method of obtaining these measurements is described, and the analysis of the results,
in terms of dispersant use, is considered. There are a number of techniques that have been developed, and this test method outlines
their application. These measurements can be used to confirm or verify the specifications of a given equipment set, its proper
functioning, and use.
1.2 This test method is applicable to systems used with helicopters or airplanes.
1.3 This test method is one of four related to dispersant application systems. Guide F1413F1413_F1413 covers design, Practice
F1460F1460/F1460M covers calibration, Test Method F1738 covers deposition, and Guide F1737F1737/F1737M covers the use
of the systems. Familiarity with all four standards is recommended.
1.4 There are some exposure and occupational health concerns regarding the methods described. These are not discussed in this
test method since they are a function of dispersant formulation. Anyone undertaking such experiments should consult the
occupational health experts of the dispersant manufacturer regarding the precautions to be used.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
E642 Practice for Determining Application Rates and Distribution Patterns from Aerial Application Equipment
E1260 Test Method for Determining Liquid Drop Size Characteristics in a Spray Using Optical Nonimaging Light-Scattering
Instruments
F1413F1413_F1413 Guide for Oil Spill Dispersant Application Equipment: Boom and Nozzle Systems
F1460F1460/F1460M Practice for Calibrating Oil Spill Dispersant Application Equipment Boom and Nozzle Systems
F1737F1737/F1737M Guide for Use of Oil Spill Dispersant Application Equipment During Spill Response: Boom and Nozzle
Systems
2.2 ASAE/ASABE Standard:
ASAE/ASABE S561.1 (R2013) Procedure for Measuring Drift Deposits from Ground, Orchard, and Aerial Sprayers - Standard
by The American Society of Agricultural and Biological Engineers
3. Significance and Use
3.1 The deposition of an aerially applied dispersant is defined as the amount of an aerially applied dispersant that contacts the
surface; whereas, application dosage (frequently referred to as application rate) is the amount of material that is released per unit
This test method is under the jurisdiction of ASTM Committee F20 on Hazardous Substances and Oil Spill Response and is the direct responsibility of Subcommittee
F20.13 on Treatment.
Current edition approved April 1, 2010March 1, 2015. Published April 2010April 2015. Originally approved in 1996. Last previous edition approved in 20072010 as
F1738 – 96F1738(2007). –10. DOI: 10.1520/F1738-10.10.1520/F1738-15.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Society of Agricultural and Biological Engineers (ASABE), 2950 Niles Road, St. Joseph, MI 49085, http://www.asabe.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F1738 − 15
area by the delivery system. The units of deposition are litres per hectare or U.S. gallons per acre. The deposition may differ from
the application dosage (volume of material per unit area) for many reasons, such as, the effects of wind on the spray and the
evaporation of the dispersant after it has been released from the aircraft.
3.2 This test method describes the measurement of the ability of a spray system to deposit a dispersant on oil. It is not intended
that this test method be used at the time of a spill. These techniques are intended to determine the equipment performance during
the development of new systems and after the repair or significant modification of a system.
3.3 The data obtained from the use of this test method can be directly related to the deposition of dispersant on an oil slick, and
thus can serve to determine both the dispersant deposition and the droplet size.
3.4 DispersantSurrogate deposition and droplet size data can be used as a technical basis for the optimization of dispersant
application equipment and its use.
3.5 The choice of a dispersant surrogate may vary, typically water is chosen along with a marker dye.
4. Apparatus and Materials
4.1 The basic concept is to provide a collection surface on which the aerially applied material is deposited. The amount of
material and the deposition pattern and its droplet size can be measured using this surface. Several systems and methods have been
developed, and each has its own advantages and disadvantages.
4.2 These measurements require a large, flat open area (such as a field or an airport) which is suitable for low-level flying and
maneuvering. The location should be away from human habitationshabitation or environmentally sensitive areas in order to
minimize problems due to noise and drifting spray.
4.3 These field programs should be conducted under low-wind conditions in order to minimize drift. Near-surface turbulence
due to thermal gradients or atmospheric instability can contribute to a variation in the results. These measurements cannot be
carried out in the presence of precipitation or in heavy concentrations of dust.
4.4 All tests are to be conducted with the flight path in an upwind direction. The upwind direction is chosen to simplify the
interpretation of the data and to conform with typical field practice. It may be necessary to alter the flight path slightly for changes
in wind direction during the course of an experimental program.
4.5 It is common practice to use a dye, soluble in the dispersant, which will assist in the detection of the dispersant by the
analysis system. Oil Red B and Rhodamine WP have been used at concentrationssurrogate, typically water, rather than the
dispersant itself. Dye can be added to the water to provide a measurement target. This dye should respond to the analytical method
used in Section 5of 0.1 to 2.0 %. The sensitivity of current detection systems allows the use of concentrations at the 0.1 % level
or less. Special permission would be required to use a dispersant and permissions may also be required to apply a surrogate, and
special precautions may be required to protect and clean the area afterwards.
4.6 The area used will become covered with dispersant spray, and it is suggested that the area not be used for agricultural
purposes at least until any evidence of the dispersant or dye is no longer observable. The length of time depends on the weather
conditions, especially precipitation that occurs after the spray program has been completed.
5. Deposition Measurement Methods
5.1 These techniques involve the use of a collecting surface of known area and the measurement of the amount and character
of the dispersant deposited on this area. A variety of systems may be used, such as the following:
5.1.1 Laser Measuring Instrumentation—The use of laser-based measuring techniques is becoming more common and can
provide both droplet size and deposition distribution. This method employs laser scattering devices deployed in an array on a flat
surface (Test Method E1260), the number of these devices depends on the specified horizontal range of these devices and the
amount of surface coverage desired by the test group. The data are collected in the memory of the units and analyzed and processed
upon completion of the test. With some units, it is possible to conduct multiple tests before recovery of the data as the data are
time-stamped.
5.1.2 Coated Cards—Standard cards specifically designed for the purpose (for example, Kromekote cards) of known area are
placed in a line perpendicular to the flight path, and extending over a distance 25 % greater than the expected swath width. The
cards typically have dimensions of 5 by 7 cm. There should be about twenty cards placed across the flight path in order to have
an adequate number of sampling points. In a typical experimental setup, the distance between sampling cards should be greater
than one metre and less than three metres. This criteria may require more or less than twenty cards depending on the spray system
being tested. Each card should be identified by a unique label, indicating its place on the sampling line and the number of the spray
pass. The marking should be made in such a fashion that it will not be removed by the dispersant surrogate, as well as Garrco
Vision Pink dye mixed at a ratio of 1:400 to provide color to the Kromekote cards. The cards are kept covered until just before
the spray run to reduce the possibility of contamination. The cards are place in holders if wind can move these cards out of position.
The placement, uncovering, and retrieval of these cards is labor intensive. After the spray run, the cards are collected and analyzed
F1738 − 15
by machine (Practice E642, ASAE/ASABE S561.1 (R2013). The cards may be used to provide both droplet size, spray width and
deposition pattern. This method may also be used in combination with other methods to provide data.
5.1.3 Glass Petri Dishes or Similar Containers—Flat dishes of known area are placed in a line perpendicular to the flight path,
and extending over a distance 25 % greater than the expected swath width. Dishes of a diameter of 120 to 140 mm are typically
used. There should be about twenty dishes placed across the flight path in order to have an adequate number of sampling points.
In a typical experimental setup, the distance between sampling dishes should be greater than one metre and less than three metres.
This criteria may require more or less than twenty dishes depending on the spray system being tested. Each sampling dish should
be identified by a unique label, indicating its place on the sampling line and the number of the spray pass. The marking should
be made in such a fashion that it will not be removed by the dispersant, the material used to dissolve the dispersant, water,
dispersant surrogate, or rough handling. The sampling dishes are kept covered until just before the spray run to reduce the
possibility of contamination. The placement, uncovering, and retrieval of these dishes is labor intensive. After the spray run, the
dishes are collected and washed with a suitable solvent, such as methanol or hexane, to collect the deposited material. The amount
of dye present can be determined by using a colorimeter sensitive to the dye used. The system must be calibrated using a sample
of the dyed dispersantsurrogate and solvent mixture for that experimental pass. For these measurements, care must be taken to
ensure that the same dilution factors are used for both the calibration and material from the sampling dishes, since the measurement
instruments are only linear over about an order of magnitude of concentration. From these sets of data, the amount of material
deposited on the surface in any units required, such as litres/hectare (U.S. gal/acre), can be calculated.
5.1.4 Metal Troughs—A variation of the sampling dish is a V-shaped metal trough, divided into sections and placed
perpendicular to the flight path. Each section is about two metres long with a cross section of about 6 cm. A number of troughs,
connected end-to-end, are used to cover a length of about 25 % greater than the total spray width. After a spray run, the troughs
are washed with a solvent, such as methanol or hexane, and the eluent from each section is collected for analysis. The concept is
similar to that of the glass dishes, but this system has the advantage of sampling the total spray width, and providing an average
dose over the discrete section. One major advantage of the troughs is that they remain in place during a number of experimental
runs, thus reducing the time between runs. This allows for more runs per day.
5.1.5 String Measurement—Another method The string method is often used to provide information on spray width and pattern.
This method uses a cord or string that is either stretched across the width of the spray or is supported on a series of stands. Except
for very narrow-width application systems, the string is supported about every two metres by a stand. The dispersant is surrogate
is Rhodamine WT dye mixed with water at a ratio of about 1:7500. The surrogate is collected by the string, and thus the needed
data are obtained. Since the cross section of the string is much smaller than that of the Petri dish or trough, more dye may be needed
in the sprayed dispersant. The string is then allowed to dry. The amount of material that the string collected is determined by a
fluorometric or colormetric technique. Automated devices are available for this application. This method measures the relative
deposition only, and not the absolute deposition.
5.1.6 Data Determination—The data collected from these types of measurements is the same in character. The amount of
dispersant that reaches the ground is measured as a function of the position along the swath of the spray. From this, spray patterns
can be determined and plotted. Data gathered using dishes and the metal troughs can be used to compute the actual deposition.
6. Drop-Size Determination
6.1 While the techniques of Section 5 provide an accurate measurement of the deposition, they do not give any indication of
the drop size or drop-size distribution
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.