The International Information Center for Geotechnical Engineers

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

SEDIMENT QUALITY GUIDELINES

 

Before the 1980s, the contamination level of sediments was determined by comparing the concentration of a chemical in sampled sediments to “background” or reference values.  It was recognized that this approach does not account for the types of biological resources in an aquatic environment or the concentration at which an adverse response would be observed in these organisms.   To improve on this method, sediment quality guidelines (SQGs) have since been developed for use in assessing sediment quality, meaning contaminant concentrations that cause adverse effects (SETAC, 2002).  

 

Numerous SQGs have been established since the 1980s, each incorporating different criteria, factors and approaches to try and account for the varied conditions in which sediment contamination occurs.  Generally, these approaches can be divided into two main categories (Burton, Jr., 2002):  

 

1.)Empirical relationships to determine sediment contamination concentrations at which a toxic response occurs

2.)Theoretical (equilibrium partitioning, EqP) relationships to describe bioavailability of  contaminants

 

Empirical SQGs are generally used for heavy metals and arsenic, but may incorporate other contaminats, like organics, although the available data is more limited. EqP SQGs are mainly used for organic compounds; however, we will also present an EqP example for heavy metals.  Both types predict adverse ecological effects from sediment contamination by the response of benthic organisms. Benthic organisms live on or in the sediments of aquatic systems and are used as an indicator of a toxic environment because of their function as an important food chain link and food source for fish, birds, and mammals residing in the same ecosystem (Batiquidos Lagoon Foundation).

 

SQGs generally outline two concentration thresholds, one in which a toxic response is unlikely and one for which a toxic response is likely.  The predictive capabilities of these guidelines leave great uncertainty in the “grey” region of contaminant concentrations that lie between the thresholds.  For this case, it may be necessary to perform a site-specific analysis by observing the health and behavior of benthic organisms at the site. It is also important to understand that SQGs tend to only incorporate one type of contaminant which may lead to inaccurate conclusions such as adverse effects being attributed to one type of contaminant when multiple are present or toxic response limit being underestimated for a mixture of contaminants.

 

Table 1 outlines the most current and popular SQGs in use in practice today. Additional information on each guideline may be found in papers by the developers. For the purpose of this paper, we will only look at two examples for each of theoretical and empirical SQGs as an introduction to their usage.

 

 

SQG Category

Approach

Developers

Theoretical

Equilibrium Partitioning

Di Toro, Mahony et al. (1991)

Di Toro, Zarba et al. (1991)

Ankley et al. (1996)

NYSDEC (1998)

Di Toro and McGrath (2000)

Empirical

Screening-Level Concentration

Persaud et al. (1993)

Von Stackelberg and Menzie (2002)

Empirical

Effects Range-Low (ERL) and Effects Range-Median (ERM)

Long et al. (1995)

USEPA (1996)

Empirical

Threshold-Effects Level (TEL) and Probable-Effects Level (PEL)

MacDonald et al. (1996)

Smith et al. (1996)

USEPA (1996)

Empirical

Apparent-Effects Threshold (AET)

Barrick et al. (1988)

Ginn and Pastorok (1992)

Cubbage et al. (1997)

Empirical

Consensus-Based Evaluation

Swartz (1999)

MacDonald, DiPinto et al. (2000)

MacDonald, Ingersoll et al. (2000)

Empirical

Logistic Regression Modeling (LRM)

Field et al. (1999, 2002)

Table 1. Types of SQGs in use today and their developers.

 

Add comment

NOTE: The symbol < is not allowed in comments. If you use it, the comment will not be published correctly.

Security code
Refresh
*Please insert the above-shown characters in the field below.

The Geoengineer.org Corporate Sponsors: