The Directive for Monitoring the Impact of Sulphur Dust on Soils (2015) specifies regulatory requirements and provides professional guidance for monitoring and mitigation of the impacts of sulphur dust on soils for those sulphur handling and processing facilities in Alberta whose EPEA approvals have the foregoing requirements.

The Directive can be viewed at:

The 2015 version of the Directive is an update and replacement of its earlier version (AEW, 2011) and the Soil Monitoring Guidelines under section II.C.3 and the Appendix A-7 of Government of Alberta’s 1989 Air Monitoring Directive.

General information

Changes to the 2015 version of the Directive

The Directive is a living document and subject to periodic revisions when new information becomes established. The 2015 version of the Directive was released largely to implement new extraction and analytical methods developed and validated in Alberta for determination of elemental sulphur in soils. This is necessary because work completed over the last few years in Alberta indicated the chloroform extraction and HPLC method (Watkinson et al, 1987) referenced in the 2011 version of the Directive was not suitable with the mainstream commercial laboratories in Alberta for reasons outlined under Question 17.

Other minor revisions include the following:

  • general information regarding policy roles of the Department and AEP
  • requirements for landowner notifications before conducting the field work outlined in this Directive
  • some refinements in reporting formats to facilitate efficient regulatory reviews of monitoring or mitigation proposals and reports, which are intended in the Directive

Effective date

The 2015 version of the Directive came into force on January 1, 2016 in the following ways:

  • For EPEA approvals that already have included the Directive for Monitoring the Impact of Sulphur Dust on Soils (AEW, 2011) as amended, no change in approvals will be needed as the 2015 version became effective automatically on January 1, 2016.
  • For EPEA approvals that still follow the Soil Monitoring Guidelines under Government of Alberta’s 1989 Air Monitoring Directive, the approvals must be amended to reflect the changes in monitoring and mitigation requirements as outlined in the Directive for Monitoring the Impact of Sulphur Dust on Soils (AEW, 2011) as amended. Prior to any EPEA approval amendment, the approval holders may voluntarily use the 2015 version of the Directive, but they will need to clarify the reporting requirements with the Director. In this case they must choose the 2015 version of the Directive or remain with the 1989 Soil Monitoring Guidelines in their entirety - they cannot use both.

Industrial operations that are required to conduct soil monitoring

The EPEA approval holders that handle solid elemental sulphur and also have the requirements in their approvals to monitor impacts of deposition of sulphur dust to soils, must conduct the soil monitoring program. Typically, these facilities handle and process solid elemental sulphur using blocks, base pads, drilling towers, granulating facilities, loading/unloading facilities, and/or store more than 100 tonnes of solid elemental sulphur.

Liquid elemental sulphur processing facilities

If a plant only operates liquid sulphur processing facilities, usually it is not required to conduct soil monitoring for sulphur dust and its potential impact on soils. Section 1.3 of the Directive has granted an exemption to this type of facility, provided that any historical impacts to soils by solid elemental sulphur operation have been remediated to appropriate standards. EPEA approval holders must follow the terms and conditions in their approvals.

When to use the 2015 Directive or the 2009 Soil Monitoring Directive

The Directive for Monitoring the Impact of Sulphur Dust on Soils (AEP, 2015) focuses on lands in the vicinity of plants that handle solid elemental sulphur. It may also extend to selected locations within the boundary of a plant site when the overall pattern of deposition of sulphur dust needs to be assessed. Monitoring for the release of sulphur to soils within the plant boundary and releases of other substances to soils in general, is otherwise addressed by the Soil Monitoring Directive (AENV, 2009), as amended, under the corresponding EPEA approvals.

Monitoring and sampling

Sampling in the field

As the Directive indicates, a minimum of five separate soil samples must be collected within a five meter radius of a sampling location. The depth intervals defined in section of the Directive must be followed. The samples must be composited within each depth interval for that location. Where it is possible, the composite samples should be mixed in the field.

Determining bulk soil density

Measurements of soil bulk density at one representative sub-location are adequate for the programs in the Directive. The bulk density data must be determined for each of the specified depth intervals as outlined in section As measurements of soil bulk density can cause significant disturbance to a sampling location, it may not need to be measured again in the subsequent soil monitoring and mitigation events, unless the site is disturbed by new construction or change in land use.

Absence of baseline data

Some clients have older plants and therefore do not have baseline soil data for prior to the introduction of the 1989 Soil Monitoring Guidelines. In these cases, where baseline soil data are not available, it is acceptable to use background locations as a surrogate baseline, provided that the locations are not affected by plant operations and the soil types are the same as the locations being monitored.

Monitoring frequency

The Directive specifies a monitoring frequency of every other year, at a minimum. The Routine Monitoring Program can be conducted by the plant on an annual basis in order to understand the deposition patterns of sulphur dust faster. This annual monitoring can be conducted as needed but the plant must follow the reporting frequencies in the EPEA approval.

Mitigation program

Operational threshold values

In the Directive, impacts of sulphur dust to soils are defined by comparison of soil data from each monitoring event against the operational threshold values in section Considering the dynamic nature of soil acidification, the most recent monitoring data should often give a more accurate assessment of the site. The trend in monitoring data will help to estimate the rates of soil acidification, or, where a mitigation plan is implemented, the rates of soil recovery.

Total sulphur analysis versus elemental sulphur analysis

Alberta Environment and Parks has kept a set of operational thresholds with multiple parameters in section 3.2.3 of the Directive. All of those parameters must be determined in a Routine Monitoring Program.

Alkaline baseline soils

Where the soil has an alkaline baseline or background condition and the measured soil pH values in the Routine Monitoring Program still remain above 6.5, the benefits of liming may be outweighed by an adverse effect on the availability of nutrients to vegetation. Instead the Mitigation Program should focus on source control and protection of other sensitive ecosystem components of the land. The proponents should contact the relevant AER or AEP staff members for site-specific solutions.

If the soil pH is below pH 6.5 for agricultural soil, or pH 5.0 for forest soils, liming is needed and the targeted pH should be within the optimal range (pH 6.0-7.0 for agricultural soils, and pH 5.0-6.5 for forest soils) for nutrient uptake.

Analytical methods

Old versus new methods

The 2015 version of the Directive requires some different analytical methods than its 2011 version and the 1989 Soil Monitoring Guidelines. The soil analytical methods are normally updated in about a 10-year period in scientific communities and improvements are often adopted along the way. Laboratory procedures for soil analyses need to be updated to remain relevant, and all relevant EPEA approval holders are required to use the new methods, or equivalent methods that are otherwise authorized by the Director. One exception is explained under the Water suspension method heading found below.

In general, it is not anticipated that the updated methods will result in drastically different analytical results. If a new laboratory method does produce distinctly different results with quality-control samples of known concentrations, the laboratory may use the new method to either:

  1. re-analyze any stored baseline samples, or
  2. analyze suitable background soil samples and use them as a surrogate baseline.

pH tests

The 1989 Soil Monitoring Guidelines specifically stated that pH test for organic soils and forest litter needed to be done at a 10:1 liquid to soil ration whereas for mineral soils a 1:1 ratio. These ratios have been widely used in determination of soil pH and are cited in the references of the Directive.

Water suspension method

The Directive has specified that the calcium chloride (CaCl2) method for determination of soil pH be used. If the water suspension method has been consistently used by an EPEA approval holder to determine soil pH in previous monitoring events, it should be followed in the future to get comparable data.

Extraction and analytical methods

The 2015 version of the Directive referenced two new extraction-HPLC analysis methods and their standard operating protocols for determination of elemental sulphur in soils while the 2011 version specified a chloroform extraction and HPLC determination method by Watkinson et al. (1987).

The new extraction and analytical methods and their standard operating protocols referenced in the 2015 version of the Directive should be used as they are recently developed to support this Directive and passed systematic validation procedures for quality assurance and quality control in analytical laboratories. Laboratory evaluations of the chloroform extraction-HPLC method by Watkinson et al. (1987), over the past three years in Alberta, indicated potential health concerns about chloroform to laboratory operators. Use of alternative chemicals is preferred as chloroform is toxic and caused damage to and leak from a HPLC equipment used to test that method.

Soil carbonates

The Directive cites both the acetic acid dissolution method and the carbon dioxide weight loss method for the determination of soil carbonates.

When mineral soils have a low carbonate content, the acetic acid method as modified by Ashworth (1997) works better. When mineral soils have a high carbonate content (5% or more) the acetic acid dissolution method will no longer be sensitive unless the amount of soil sample is markedly reduced. Alternatively, the carbon dioxide weight loss method can be used. For organic soil samples, follow the carbon dioxide weight loss method because high amounts of organic matter can make the acetic acid dissolution method inaccurate.

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