IP09 Persistent Organic Pollutants (POPs)
B113 & B114
1:20 PM - 4:40 PM, Wednesday
(IP075) Historical trends of POPs and heavy metals deposition in the region of the Zempoala Lagoons, Central Mexico.
Hansen, A.1, van Afferden, M.1, 1 Mexican Institute of Water Technology, Jiutepec, Morelos, Mexico
ABSTRACT- To determine priorities for and track progress in the management of environmental contaminant reduction programs such as the Stockholm Convention, deposition trends should be identified and evaluated by comparing current concentrations with past levels of pollutants. Since historical monitoring data on Stockholm Convention persistent organic pollutants (POPs) are not available for Mexico, there is no possibility to establish deposition inventories, background concentrations and trends in environmental health risks. There exists only one possibility to recover and reconstruct these data: through sediment core analysis of POPs and other priority contaminants. The high mountain lake Zempoala in the center of Mexico was selected as a first intent to reconstruct "background" atmospheric historical deposition. Sampling stations were selected using bathymetric data and six cores were obtained from the deepest parts of the lake. Frozen cores were cut vertically to evaluate stratification. The most suitable core was sectioned and the segments analyzed for dating by isotopic methods using 137Cs and 210Pb. Subsamples of the same sections were analyzed for organochlorine pesticides and heavy metals. Sedimentation rate was determined in 0.124 g cm-2 yr-1, corresponding to a maximum age of the 44 cm core of approximately 60 years. The first presence of total DDT occurred in a depth between 28 and 32 cm of the sediment profile, corresponding to the time period of the 1960s, with a concentration of 5.3 
g kg-1. The maximum concentration of total DDT (13.0 g kg-1) was found in the section between 20 and 24 cm depth that represents late 1970s and early 1980s. Subsequently, the concentrations decrease towards the present level of 1.6 g kg-1. Similar patterns occurred for the 
-Lindane and lead depositions. The results suggest that the Mexican environmental policies of the last decades have contributed to the reduction of environmental concentrations of these substances in the center of Mexico.
Key words: Lindane, DDT, Lead, sediment cores