June 2003 Sampling and Analysis Protocol for Ontario Regulation 267/03 Made under the Nutrient Management Act, 2002

Part 2 - Sampling Methods

Table of Contents

  1. Soils In-situ
  2. Fluid Materials in Tanks and Lagoons – Mixed Materials
  3. Sampling Fluids in Tanks or Lagoons when Agitation is not Feasible
  4. Solid Materials in Piles or Large Containers
  5. Solid and Mixed Materials from Continuous Processes and Unloaders
  6. Field Quality Control (QC)
  7. Cleaning and Prevention of Cross Contamination

2.1 Soils In-situ

Collection of Soil Samples

The goal in collecting soil samples is to provide a small volume of soil for analysis that is representative of the whole volume of soil within the area of interest. There are a number of different ways to accomplish this goal. This section describes the minimum sampling requirements for information purposes and outlines some of the more detailed techniques.

To be representative, the samples collected must include the depth of soil that would normally be tilled. For contaminants and most nutrients this depth is approximately 15 centimeters (6 inches). This depth is appropriate even where no tillage is used, as it represents the part of the soil where most roots are present and most nutrient absorption occurs. The exception to this is the soil nitrate sample, which is collected to a depth of 30 cm (12 inches) to include nitrate which may have been leached from the surface soil to the lower part of the rooting zone. To collect samples to the proper depth, the easiest equipment to use is a sampling tube or auger, which is simply inserted to the proper depth and then removed, bringing the sample with it. A shovel or spade can be used instead, but it is much more labour intensive to collect samples with a shovel or spade than with a sampling tube, and it is much more difficult to keep each sub-sample of uniform size.

The pattern of sample collection must provide a representative sample of the entire area. It means: 1) sufficient grab samples (e.g. cores) must be collected, 2) the grab samples must be collected so as not to introduce bias into the sample, 3) the area being sampled must be reasonably uniform, and 4) the area being sampled must not be too large.

Number of Grab Samples

There is significant small scale variation in the nutrient content of soil, so a relatively large number of grab samples must be collected to provide an accurate average value. In small fields (less than 5 hectares, 12.5 acres), collect a minimum of twenty grab samples (about 50 - 75 cm3 each), and mix them together thoroughly to produce the composite sample that is too be submitted for analysis. In larger fields (more than 5 hectares, 12.5 acres), at least two additional cores must be taken for each additional hectare (2.5 acres).

Avoiding Bias

Grab samples collected from areas in the field where past management practices may have significantly changed the nutrient content of the soil should not be mixed with those from other parts of the field. This includes areas where manure, fertilizer or lime have been stockpiled, laneways, and old exercise yards. These areas may have much higher nutrient contents than the field as a whole, and should be sampled separately. Also avoid sampling dead furrows, as the sample would include a significant portion of subsoil which is normally much lower in nutrient content.

Maintaining Field Uniformity

In areas that have been farmed, the largest source of variation in soil nutrient content is the past management of the field, so any sampling design must take this into account. Any areas that have received different nutrient applications in the past, if this is known, should be sampled separately. Other factors that could affect the nutrient content include topography, soil texture, erosion, or large variations in crop yield.

Maximum Field Size

Even in fields that appear uniform, there can be significant variation in nutrient content. Normally, the largest area that can be represented by a single sample is ten hectares (25 acres). Larger fields should be divided, where possible, according to previous field boundaries. Failing this, divisions should be made according to distance from existing or previous barns or manure storages, or according to topography or soil type.

Fields larger than 10 hectares, up to a maximum of 20 hectares (50 acres) may be permitted where there is evidence to show that the nutrient content of the field is uniform (within 15% of the mean value), and that the management of the field is uniform.

Where samples for metal analysis must be collected (for example, where application of sewage biosolids is planned), a larger field size, up to 40 hectares (100 acres) is permitted.

Sample Collection

The best way to ensure a representative sample of the field is to traverse the field in a zig-zag pattern, collecting grab samples (e.g. cores) randomly from the entire field area. Take separate samples for analysis from any parts of the field that differ markedly in appearance of the soil or the crop. Clean equipment between collecting different samples to avoid cross-contamination (see Section 2.7).

In some situations, particularly for high value crops, more intensive sampling techniques are used. If this practice is used, each sampling area should be treated as a small field for the purposes of defining any application limitations. Further information on sampling techniques can be found in OMAF Publications 611 (Soil Fertility Handbook) and 811 (Agronomy Guide for Field Crops).

Collect the soil grab samples in a clean pail or other suitable clean container, break up the lumps and mix the soil well. Place a sub-sample of the soil in an appropriate, properly labeled container for shipment to the analytical laboratory.

Where non-agricultural source materials are to be applied to soils, the sampling locations must be geo-referenced. At a minimum, this means providing the GPS co-ordinates of one corner of the field, and the distance and direction of the area encompassed by the samples. While co-ordinates for each grab sample are not required, this can be included with the sample information.

Sample Handling

A variety of containers are available for shipping sub-samples to a laboratory for analysis. The receiving laboratory may have a preference for the type of container. Plastic bags or plastic lined paper are generally favoured because they keep each sample separated from the other, and prevent moisture from soaking any information sheets included with the samples. Samples to be analyzed for trace contaminants will require special handling and containers that are specific to each contaminant. The laboratory will provide information on the handling requirements for trace contaminants.

No special handling is required for samples to be analyzed for pH, metals, or most nutrients. It is desirable to air dry the samples if they are to be held for a long period of time. The samples should be held in a cool, dry location. The exception to this is samples to be analyzed for nitrate nitrogen, which must be cooled to below 10°C (preferably to below 4°C), and kept cool until analysis. If the samples for nitrate nitrogen are stored at room temperature, nitrification can occur within the sample and distort the analytical results.

2.2 Fluid Materials in Tanks and Lagoons – Mixed Materials

Fluid and semi-solid materials pose special challenges in collecting representative samples. Most of the fluid materials considered for application to land are suspensions rather than true liquids, and tend to settle into layers of varying density and nutrient content. Where these are to be applied to land in separate applications (for example, the supernatant and the sludge from a lagoon), each layer must be sampled separately. In most situations, however, the material will be agitated prior to application to produce a relatively uniform mixture. It is easiest to obtain a representative sample of the material in the tank or lagoon after it has been thoroughly agitated. These materials need to be sampled so that the sample represents the entire volume of material. Where agitation prior to sampling is not feasible, the procedures in Section 2.3 must be used.

Grab samples can be collected either directly from the storage following agitation, or as the material is being loaded onto the hauling or application equipment. A minimum of five grab samples must be collected from each storage. Lagoons or tanks containing more than 1,000 m3 should have additional grab samples taken at a rate of at least one additional grab per 200 m3 of material above 1,000 m3. Samples must be collected using a clean, non-metallic container (a 20 liter plastic pail works well). Place these grab samples in a larger non-metallic container, and keep the container covered except when the next grab sample is being added. Mix the resulting composite sample thoroughly to ensure homogeneity. Collect composite samples from it as required. Sample bottles must not be filled more than 1/2 to 2/3 full, so that there is enough headspace in the bottle to allow for the build-up of pressure and prevent bursting. Normally one 500 mL sample bottle will suffice for nitrogen, phosphorus and total solids analyses, and an additional 500 mL sample bottle, which can be taken from the composite mixture already collected, is required for metals analyses when these are required.

At large facilities, on-site nitrogen analyses may be useful to provide accurate information to individual farmers. Portable testing equipment can have advantages. If such equipment is used, source material from each storage location should be sampled at the time the material is being removed for spreading. Samples may be taken either from the spreader or from the tanker that conveys the material to the spreader.

2.2.1 Sampling Patterns for Use in Lagoons

Transect Method

When using the transect method, two transects should be carried out: one (1) transect across the length of the lagoon; and (1) transect perpendicular to the other across the width. The point where both transects intersect should be near the centre of the lagoon. Sampling along each transect should be carried out at a minimum of five (5) pre-determined sampling locations (e.g. take samples every 15 m along the transect ).

Grid Method

When using a grid approach, the lagoon should be divided into blocks and sampling should be carried out at a minimum of five (5) pre-determined locations equally spaced within the blocks. Additional sampling at a greater number of equally spaced locations within a greater number of blocks will improve the accuracy of the results.

2.3 Sampling Fluids in Tanks or Lagoons when Agitation is not Feasible

There are two situations where tanks or lagoons may be sampled without agitation: first, the materials will be agitated prior to application, or second, the stratified materials will be applied without mixing (i.e. supernatant, and sludge). Sampling requirements in each case will be similar. However, in the special case of materials in tanks with vertical sides, which will be agitated prior to land application, a simplified sampling method can be used (see Section 2.3.3).

Samples for analysis must be representative of the contents of tanks or lagoons.

Special care is required to obtain representative samples from materials that have stratified. Each layer to be land applied separately should be sampled separately, and it may be appropriate to subdivide these layers. Because of the inherent variability in taking this type of sample, a minimum number of 10 grab samples should be taken for each composite, and at least 2 composite samples should be taken and analyzed separately for each identified layer. Lagoons or tanks containing more than 1,000 m3 of material should have additional grab samples taken at the rate of at least one additional grab per 100 m3 of material above
1,000 m3.

Lagoons with sloping sides present an even greater challenge, because the stratification will not be consistent across the entire area of the lagoon. A sample transect will need to be established to accurately represent the entire volume of material in the lagoon, with proportionately more samples from the deeper parts of the lagoon than from the shallow parts. All precautions must be taken to protect workers from injury when this type of sampling is carried out.

2.3.1 Supernatant Materials

When a fluid material containing suspended solids is stored in a tank or lagoon, the heavier suspended solids will settle to the bottom leaving a low-solids fluid that is commonly referred to as supernatant. For sampling purposes, supernatant is the fluid material between the settled solids sludge at the bottom and the scum on the surface. When only the supernatant is to be removed (i.e. irrigated on to land), the depth and thickness of the supernatant above the lower sludge interface, and the number of layers within the supernatant, must be determined in order to sample the supernatant.

2.3.1.1 Sampling Supernatant Materials in Enclosed Tanks

Sampling a supernatant material in an enclosed tank should be carried out from at least one sampling port (or hatch) at the top of the tank. If a second sampling port is available, repeat the sampling procedure. Sampling an enclosed fluid material from a sampling port at the top of the tank may be hazardous depending on the material stored in the tank and the potential for toxic or explosive vapours in the headspace of the tank. Before proceeding to sample an enclosed tank, sampling personnel should follow all appropriate health and safety procedures, including, but not limited to, the following:

  • review all information concerning the tank, such as the type and capacity of tank, condition of tank, and known/suspected contents;
  • inspect the ladder, stairs, catwalk or other structure to be used to access the sampling port to ensure that they will support the person(s) doing the sampling;
  • inspect all sampling equipment (i.e. do you have all of the necessary sampling equipment?; has it been properly cleaned?);
  • review all safety procedures and emergency contingency plans with regard to potential toxic or explosive vapours in the tank headspace;
  • if the tank is metal, ensure that the tank is properly grounded; and
  • remove all sources of ignition from the immediate area.

Where toxic or explosive vapours are likely to be present in the tank headspace, air quality measurements should be taken and sampling should only proceed if the readings meet acceptable air quality standards. In addition, before sampling commences, the tank headspace should be cleared of any toxic or explosive vapours using a high volume explosion proof blower.

Sampling Procedure

First determine the depth of the supernatant at the sampling location, from the upper scum interface to the lower sludge interface, using a weighted tape measure, probe line or other suitable measuring device. Then collect one (1) sample of supernatant from 30 cm below the upper interface with the scum layer, one (1) sample from mid-depth, and one (1) sample from 30 cm above the bottom interface with the sludge layer. These samples can be collected using various sampling equipment such as a subsurface grab sampler or bacon bomb sampler. For supernatants that are less than 1.5 m in depth, use a glass thief or Composite Liquid Waste Sampler (COLIWASA) to collect the sample.

Three (3) to five (5) samples taken at a sampling location usually will suffice for supernatants in a tank or lagoon where the original fluid material has been subjected to a prolonged settling period. Additional mid-point samples may be necessary for materials recently placed in a tank or lagoon, or which contain solids that have a tendency to remain in suspension for long periods.

Mark the sample identification number, location and depth on the outside of each sample container. The sample container should be non-reactive with the sample material (see Table 2.1).

The three samples should then be compared for visual phase differences. If there is a readily observable difference in colour or viscosity between the upper and mid-point samples, or between the mid-point and lower samples, an additional sample should be taken at the mid-point (half-way) depth between the two samples. By halving the distance between two discrete sample points, the person doing the sampling can then determine the depth of each phase change and, more importantly, the thickness of each distinct layer.

A minimum of one sample from each phase or layer within the supernatant material must be collected and placed in a glass or plastic sample bottle or container. Sample bottles must not be filled more than 1/2 to 2/3 full, so that there is enough headspace in the bottle to allow for the build-up of pressure and prevent bursting. Normally one 500 mL sample bottle will suffice for nitrogen, phosphorus and total solids analyses, and an additional 500 mL sample bottle, which can be taken from the mixture already collected, is required for metals analyses when these are required.

Transport all collected samples to the laboratory for analysis as soon as possible after sampling to minimize potential sample transformations within the container.

Determining the Weighted Mean Concentrations of Test Parameters

The purpose of multi-layer sampling of a supernatant is to determine the concentrations of test parameters in the various layers on a volumetric basis. This information can then be used to determine the weighted mean concentrations of test parameters in the total volume of supernatant.

When the sampling is completed at all sampling locations, determine the measurements of the containing structure (i.e. inside diameter of the tank), and then use the layer depth and thickness information previously determined to calculate the volume of each layer of supernatant. Using the volume determined for each layer and the analytical results for the test parameters for each layer, calculate the weighted mean concentrations of the test parameters in the total volume of supernatant. Where replicate samples are taken from two or more sampling locations, first determine the mean depth and thickness of each layer, and mean concentrations of the test parameters in each layer, before calculating the weighted mean concentrations.

2.3.1.2 Sampling Supernatant Materials in Open Tanks

The procedure for sampling a supernatant material in an open (non-enclosed) tank is the same as that outlined in the 'Sampling Procedure' description in Section 2.3.1.1, except for the number of sampling locations. A minimum of two different locations must be sampled in order to characterize the supernatant material. Where there is a walkway over the tank, the locations may consist of randomly selected sites below the walkway. If there is no walkway, the sites should be randomly selected around the perimeter of the tank. Sampling locations should not be located close to inflow pipes or other inlets.

While the potential for toxic or explosive vapours is not as great as for enclosed tanks, they may still occur above an open tank. Sampling personnel should therefore follow the same safety procedures and take the same safety precautions as outlined in Section 2.3.1.1. At no time should sampling be carried out from above an open tank containing hazardous material. Where a material to be sampled is considered hazardous, sampling should only be undertaken from outside the perimeter of the tank using appropriate protective equipment.

The procedure for determining the weighted mean concentrations of test parameters in the total volume of supernatant is the same procedure as outlined in the 'Determining the Weighted Mean Concentrations of Test Parameters' description in Section 2.3.1.1

2.3.1.3 Sampling Supernatant Materials in Lagoons

Sampling supernatant materials in lagoons poses a challenge because the sides are sloping rather than vertical, as is the case for tanks. The length and width of the lagoon and the steepness and length of the side slopes, must be known when determining the volume of each layer of supernatant.

When supernatant is only pumped from the upper portion of a lagoon (e.g. the top 60 cm), it is only necessary to take samples from that portion. Samples taken from this upper layer should represent the contents of the layer for several weeks. However, the surface contents of a lagoon will change from month to month due to precipitation, evaporation, and temperature fluctuations. Therefore, time of sampling should be as near as possible to when the supernatant is to be pumped out or removed. Two simple methods for sampling follow.

Bucket-Toss Method

Attach a rope to a small plastic bucket and then throw the bucket out into the lagoon and let it sink. Then carefully pull the bucket back to shore making sure that it does not contain surface scum or solids. Swirl the bucket and then pour about 1 litre of the contents into a second clean plastic bucket. Repeat this four (4) more times from different locations around the perimeter of the lagoon. Then swirl the bucket with the composite sample and pour a subsample into a clean, plastic or glass container such as a 500 ml wide mouth amber glass jar with a Teflon-lined screw cap. The number and amount of samples required for various analyses are outlined in the 'Sampling Procedure' description in Section 2.3.1.1. More than one subsample may be required.

Dipper Method

Tape a clean plastic bottle securely to a pole that is long enough to reach over any scum collected at the edge of the lagoon. Dip out at least five (5) individual samples at different depths and locations and pour them into a clean plastic bucket. Swirl the bucket and then pour a subsample into a clean plastic or glass container. The number and amount of samples required for various analyses are outlined in the 'Sampling Procedure' description in Section 2.3.1.1. More than one subsample may be required.

Sampling deep supernatant materials (e.g. 3 to 4 m deep) in lagoons, particularly in large lagoons, should be carried out from the surface by boat using either a transect or grid sampling approach (see Section 2.2.1). Large lagoons containing liquid manure or sewage biosolids should be sampled using one of these methods. Lagoons that contain potentially hazardous materials, however, should never be sampled from a boat. Instead, they should be sampled from the perimeter banks or piers using appropriate protective equipment.

When sampling from a boat at a sampling location, follow the sampling procedures outlined in the 'Sampling Procedure' description in Section 2.3.1.1.

When the sampling is completed at all sampling locations, determine the surface area of the lagoon (i.e. length and width) and the steepness of the side slopes underneath the stored material (i.e. 3:1) by referring to the engineering design or by consulting with the owner. This information, along with the mean depth and thickness of each layer (determined by averaging the depths and thicknesses obtained at all sampling locations), should then be used to calculate the volume of each layer of supernatant. Then combine the volume determined for each layer with the analytical results for the test parameters for each layer, and calculate the weighted mean concentrations of the test parameters in the total volume of supernatant.

2.3.2 Sludge Materials

When a fluid material containing suspended solids is stored in a tank or lagoon, the heavier suspended solids settle to the bottom resulting in a high-solids material called sludge. For sampling purposes, sludge is the settleable solids at the bottom of a tank or lagoon that have separated from a liquid either during processing or as a result of prolonged storage in a tank or lagoon.

2.3.2.1 Sampling Sludge Materials in Enclosed Tanks

Sampling a sludge material at the bottom of an enclosed tank should be carried out from at least one sampling port (or hatch) at the top of the tank. If a second sampling port is available, repeat the sampling procedure. Sampling any fluid or high-solids materials in an enclosed tank from a hatch at the top of the tank may be hazardous depending on the material stored in the tank and the potential for toxic or explosive vapours in the headspace of the tank. Therefore, before proceeding to sample a sludge in an enclosed tank, sampling personnel should undertake the same assessments and take the same precautions as outlined in Section 2.3.1.1.

Sampling Procedure

The concentrations of settleable solids in sludge at the bottom of a tank or lagoon will vary both horizontally and vertically. And, while the sludge at the bottom of a tank or lagoon will separate into layers, it is often difficult to make visual distinctions between layers. Therefore, grab sampling of the sludge at different depths should be undertaken.

Sludge samples should be taken using a bacon bomb sampler, sludge judge or other suitable sampling device.

First determine the depth of the sludge at the sampling location. This can be accomplished using a weighted tape measure, probe line or other suitable measuring device. Then collect one (1) sample of sludge at 50 cm depth intervals (e.g. at 50 cm, 100 cm, 150 cm, etc.). Pour each sample into a clean plastic bucket or other suitable container. Then mix the composite sample in the container and pour a subsample into smaller container for transport to the laboratory. Mix the resulting composite sample thoroughly to ensure homogeneity. Collect composite samples from it as required. Sample bottles must not be filled more than 1/2 to 2/3 full, so that there is enough headspace in the bottle to allow for the build-up of pressure and prevent bursting. Normally one 500 mL sample bottle will suffice for nitrogen, phosphorus and total solids analyses, and an additional 500 mL sample bottle, which can be taken from the composite mixture already collected, is required for metals analyses when these are required.

Transport all collected subsamples to the laboratory for analysis as soon as possible after sampling to minimize potential transformations within the container.

Determining the Mean Concentrations of Test Parameters

When sampling is completed at all sampling locations, determine the measurements of the containment structure (e.g. inside diameter of the tank). Then determine the mean depth and thickness of the sludge using the values recorded at all sampling locations. The volume of sludge can then be determined using this information. Next determine the mean concentrations of test parameters in the sludge by averaging the analytical results obtained for all subsamples.

2.3.2.2 Sampling Sludge Materials in Open Tanks

The procedure for sampling a sludge material in an open (non-enclosed) tank is the same as that outlined in the 'Sampling Procedure' description in Section 2.3.2.1, except for the number of sampling locations. A minimum of two different locations must be sampled in order to characterize the sludge material. Where there is a walkway over the tank, the locations may consist of randomly selected sites below the walkway. If there is no walkway, the sites should be randomly selected around the perimeter of the tank.Sampling locations should not be located close to inflow pipes or other inlets.

While the potential for toxic or explosive vapours is not as great as for enclosed tanks, they may still occur above an open tank. Sampling personnel should therefore follow the same safety procedures and take the same safety precautions as outlined in Section 2.3.1.1. At no time should sampling be carried out from above an open tank containing hazardous material. Where a material to be sampled is considered hazardous, sampling should only be undertaken from outside the perimeter of the tank using appropriate protective equipment.

The procedure for determining the mean concentrations of test parameters in the sludge as a whole is the same procedure as outlined in the 'Determining the Mean Concentrations of Test Parameters' description in Section 2.3.2.1.

2.3.2.3 Sampling Sludge Materials in Lagoons

Sampling sludge materials in lagoons poses a challenge because the sides are sloping rather than vertical, as is the case for tanks. The steepness and length of the side slopes, and overall depth of the lagoon, must be known when determining the depth and volume of sludge in a lagoon.

Sampling sludge materials, particularly in large lagoons, should be conducted by boat using either a transect or grid sampling approach (see Section 2.2.1). Lagoons that contain potentially hazardous materials, however, should never be sampled from a boat. Instead, they should be sampled from the perimeter banks or piers using appropriate protective equipment.

When sampling from a boat at a sampling location, follow the sampling procedures outlined in the 'Sampling Procedure' description in Section 2.3.2.1.

When the sampling is completed at all sampling locations, determine the surface area of the lagoon (i.e. length and width) and the steepness and length of the side slopes underneath the stored material (i.e. 3:1) by referring to the engineering design or by consulting with the operator. This information, along with the mean depth and thickness of sludge (determined by averaging the depths and thicknesses of sludge obtained at all sampling locations), should then be used to calculate the total volume of sludge in the lagoon.

Then determine the mean concentrations of test parameters in the total volume of sludge by averaging the analytical results obtained at all sampling locations.

2.3.3 Sampling Materials In Straight Walled Tanks

In the special case where the material is not mixed prior to sampling, but will be mixed prior to land application, and is in a tank with vertical sides, a simplified sampling procedure may be used. The layers do not need to be sampled or analyzed separately, but samples can be taken to include the entire depth of the tank. This can be accomplished with a pipe or tube that is inserted vertically to the entire depth of the tank, and then sealed at the bottom end to collect a complete sample.

2.4 Solid Materials in Piles or Large Containers

Sampling from large piles of materials, such as solid manure or paper fibre biosolids, can pose problems with respect to obtaining samples that are representative of the piles. It is difficult to collect any samples other than surface samples. Since some materials have a tendency for fine and coarse fractions to separate when piled, surface samples are not likely to be representative. Because many piled materials have a large amount of inherent variability collecting a representative sample will be difficult at any time.

The preferred method of sampling piles is for samples to be obtained from different depths and mixed together such that the resulting composite sample is representative of the pile. This is most easily accomplished when the storage is being emptied, as grab samples can be collected as the material is being loaded. If the piles must be sampled in situ, then some form of equipment to extract cores from the entire depth of the pile will be necessary.

Solid materials can be highly variable in their chemical or bacterial concentrations, and it is therefore necessary that for such materials at least 10 grab samples for piles of 100 m3 or less be collected and composited to form the sample. For larger piles, proportionately more grab samples should be taken. Place the grab samples in a clean container (see table 2.1) that can be covered or sealed between sample additions to prevent moisture loss. Once all the grab samples have been collected, empty them onto a large surface (of appropriate composition) for mixing. The most efficient way of obtaining a representative sample is to mix and chop the material with a clean shovel, then divide the pile into quarters. Discard two opposite quarters, combine the remaining two, and repeat the process until a composite sample of the desired size is obtained. The composite sample should total approximately 1 kg. The same result can be obtained by taking small sub-samples from all sections of the sample until a sample of approximately 1 kg has been obtained. Alternate methods approved by a recognized standards organization may also be followed. Place the composite sample in a container or bag (see Table 2.1), then place in an appropriate container for shipping to the laboratory for analysis.

2.5 Solid and Mixed Materials from Continuous Processes and Unloaders

In some situations it may be necessary or desirable to sample a material that is resulting from a continuous process or from an unloader. It is likely that proper sampling from the waste stream will produce more accurate and representative samples at less cost than sampling of the final large pile or hopper. The main principle in sampling waste streams is that the sample must be representative of the entire waste stream.

Discharges from a belt should be sampled with a scoop or shovel which has been chosen or fabricated to match the width and general contour of the belt as closely as possible. Grab samples can be taken at any convenient point along the belt as long as the entire width of the belt is being sampled. Any fines or liquid present on the belt must be included in the sample.

For any sampling strategy for waste streams, the sampling frequency and the number of grab samples combined into composite samples depend on the variability of the waste over time. Possibilities for taking representative samples include taking samples every hour over eight to twenty four hours (depending on the process schedule) and combined to form daily composites, as well as taking daily samples for a week and combining them into a weekly composite. Since the sampling period and number of samples will vary for each process, it is important that sampling personnel be familiar with the variability of the waste stream both over time and at different locations in the process. The sampling program must result in characterization of this variability as well as in the ability to properly classify the waste.

Often, solid discharges fall into a hopper or storage area directly from a process. In these situations, long-term composites may be obtained by sampling the material after it has accumulated. Random grab samples can be taken from the hopper or storage area provided that the sampling strategy provides samples that are representative of the material. It may be necessary to mix materials prior to sampling if separation of materials has occurred in the container.

2.6 Field Quality Control (QC)

Table 2-1 provides a summary of the field quality control procedures that must be used for sampling for nutrient management activities.

Table 2-1. Field Quality Control Procedures
Type of Sample Nutrients
Composite
Metals
Composite
Organics
Composite
E. coli
Composite
Container Plastic, glass Plastic, glass with plastic or Teflon lined lids Solvent rinsed, amber glass with foil or Teflon lined lids Sterilized plastic bags/appropriate container
Field QC samples Recommend that QC program uses duplicates. Recommend that QC program uses duplicates. Recommend that QC program uses duplicates. Recommend that QC program uses duplicates.
Storage For nitrogen, in field keep cool and out of sun and refrigerate <10°C for storage   In field keep cool and out of sun and refrigerate <10°C for storage In field, keep cool and out of sun and refrigerate at 0- 10°C for storage.
Additional Requirements     No contact of sample with plastics during sampling or storage N/A

2.7 Cleaning and Prevention of Cross Contamination

For all forms of sampling, equipment and containers must be cleaned and rinsed between collection of separate samples for analysis (that is, between sites, locations or sampling times), such that cross contamination of samples is minimized. Thorough washing of equipment with soap or detergent followed by a thorough rinse with clean water (preferably distilled or deionized) should be adequate for the standard parameters to be analyzed.

2.7.1 Special Cleaning Procedures for Sampling for Trace Organic Analysis

Analysis for trace organic compounds is not normally required; however there may be situations where materials proposed for land application are suspected of containing specific trace organic compounds due to the particular process used to produce them. Special considerations regarding prevention of cross contamination apply should there be a need to sample for trace organic constituents. The basic methodology for sampling for trace organics is the same as that for inorganics described in the preceding sections. However, samplers must adhere to the following additional procedures:

a) Control of Cross-contamination

Soil sampling for trace organic contaminants requires special techniques in order to avoid contamination both from other samples and from sampling equipment and containers. Where potentially dangerous levels of contaminants are suspected, the sampler should wear protective gloves made of solvent-resistant material (e.g., latex). Neither gloves nor bare hands should contact the sample directly.

b) Equipment Cleaning Procedures

The sampler must carefully clean all sampling equipment which contacts material directly (i.e. samplers, corers, knives) between sites. The recommended cleaning procedure is as follows:

    1. Remove adhering particles of the material by scrubbing with dilute laboratory soap solution.
    2. Rinse thoroughly with distilled water.
    3. Rinse with acetone. *
    4. Rinse with hexane. *
    5. Allow equipment to air-dry before sampling. Do not use a paper towel or cloth.

    * Use methanol as the rinsing solvent where acetone or hexane are potential contaminants of concern.

The sampler should place all grab samples in a stainless steel bowl and mix the soil prior to placing it in the sample jars. The bowl and mixing spoon/rod are cleaned as per the usual wash/rinse procedure described above. For analysis for volatile organic compounds (VOCs), grab samples must not be mixed or composited, as these processes cause losses of the compounds of interest. Rather, the samples should be placed immediately into the appropriate containers.

c) Sample Containers and Sample Preservation

Solvent (hexane and /or acetone) rinsed, wide-mouthed amber-coloured glass jars with foil or Teflon lined lids are suitable for all classes of organic compounds (including PAH's, PCB's pesticides, and VOC's).

The samples, with lids screwed on tightly, must be kept cool (preferably refrigerated, otherwise in coolers out of the direct sunlight) until delivery to the analytical laboratory.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 30 June 2003
Last Reviewed: 30 June 2003