Abstract
The determination of background levels of tracemetals in soils and sediments is a key point for the proper assessment
of pollution degree. This study demonstrates the suitability of integrating geological and statistical methods
for the reliable determination of background levels, applying it to the sediments of Lake Albufera, a wetland of international
importance that is highly eutrophic. The procedure followed includes sampling of sediment cores at
different points of the lake, including reference sites, and the subsequent statistical analysis of the data, comprising
descriptive statistics, probabilistic plots and modal analysis. The final proposal of background levels considers the
data subset separated by the statistical analysis and the spatial and age characteristics of sediments, proving the
usefulness of jointly using geological and statisticalmethods. The upper limits of the background populations, defined
as themean+2σ and expressed in mg/kg, are Cd (0.38), Cu (28.8), Ni (25.9), Pb (25.5), Zn (88.6), Fe (2.2%)
and Mn (345.7). Background levels proposed for different parts of Spain, found in an extensive literature review,
are also provided in this article. Once determined the background levels, the assessment of pollution degree of sediments
using pollution indexes indicates that the top 25 to 30 cmof sediments has a pollution level betweenmoderate
and severe in the peripheral sites, which are nearest to the pathways of contamination, and that the north
zone of the lake is the most polluted by the group of the fivemetals, including Cd, Cu,Ni, Pb and Zn.
