Site-specific sediment quality values for the Gulf of Cadiz (Spain) and San Francisco Bay (USA), using the sediment quality triad and multivariate analysis

Sediment quality values need to be developed to help protect public health and the environment. Data derived from sediment chemistry, sediment toxicity tests and macrobenthic infaunal community structure from two separate integrative studies (sediment quality triad) conducted in the Gulf of Cadiz and in San Francisco Bay were analyzed by multivariate statistical techniques (principal component analysis [PCA] and factor analysis) to identify the concentration ranges of the chemicals associated with adverse effects. Application of PCA-factor analysis to the data matrix for the Gulf of Cadiz showed that the three data types could be represented by five principal factors, whereas for San Francisco Bay, there were four principal factors. These factors, as well as chemical concentrations and biological effects, were used to establish site-specific sediment quality values for each area studied. Positive prevalence of these factors in the cases studied (seven stations in the Gulf of Cadiz and nine in San Francisco Bay) was used to establish the ranges of chemical concentrations associated with adverse effects. The values proposed for the Gulf of Cadiz, in terms of concentrations at or below which biological effects have been shown to be minimal, are (in mg kg-1 of dry sediment): chromium, 101.2; lead, 66.8; linear alkylbenzenesulphonate, 12.8; silver, 1.2; and mercury, 0.46. The values proposed for San Francisco Bay are (in mg kg-1 of dry sediment): zinc, 156; chromium, 110; nickel, 88; copper, 68; arsenic, 58; lead, 49; tin, 8.0; silver, 4.0; mercury, 0.37; PCBs, 0.057; and DDTs, 0.00224.