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Sediment Quality Guidelines (SQGs): A Review and Their Use in Practice

 

 

LIMITATIONS OF SQGS

 

SQGs are often described as a useful, predictive tool in the assessment of sediment quality and contamination.  While many organizations believe this to be true, it is important to consider the limitations of SQGs for use in practice.

 

A.) Empirical SQGs predict thresholds at which a toxic response of benthic organisms is probable.  However, SQGs, in general, do not provide perspective on the risk and possible negative outcomes associated with toxic concentration levels which requires a separate risk assessment.

 

B.) The factors used in the development of SQGs, especially older ones, is not well-documented and limited guidance is available on which SQGs are applicable for criteria (MacDonald, 2000).  For this reason the use of SQGs is somewhat controversial in practice, and are not standardized across environmental agencies.

 

C.) Research and development of new SQGs is expensive and their future practicality and performance are uncertain.

 

D.) EqP SQG predict concentrations based on equilibrium conditions.  In addition, available relationships do not model release of contaminants trapped in pores of sediments where they can be sorbed on interstitial walls.

 

E.) As with any empirical model, it is important to be aware of the types and rates of test errors present in each empirical SQG.

 

Even though SQGs may leave something to be desired, they are a useful tool that can provide a first guess at the nature of a sediment contamination problem.  Combined with engineering judgement, research on the SQG being used, and appropriate field and laboratory sampling and testing, SQGs are an important tool in practice for sediment contamination, remediation, and risk assessments..

 

In conclusion, Table 8 provides a matrix of advantages and disadvantages associated with the practical use of both types of SQGs discussed herein, empirical and theoretical (EqP).  This list is not exhaustive, but provides a summary of the advantages and disadvantages explored in this paper in regards to SQGs.

 


 

Empirical SQGs

Theoretical (EqP) SQGs

Advantages

  • large database of lab and field tests

  • predicts toxic response

  • simple to use

  • theoretical formulation

  • predicts bioavailibility

  • good for most organic contaminant scenarios

Disadvantages

  • most data for metals

  • difficult to separate effects from a mixture of contaminants

  • “grey” area between thresholds

  • test errors

  • poor documentation for formulations

  • more important to understand assumptions such as sorption and pore water

  • more difficult to use

  • always assumes equilibrium

Table 8. Summary of advantages and disadvantages for empirical and theoretical SQGs.

 

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