Chemical Analysis of Sediments in Tecolote Canyon

Starting in the beginning of the World War Two period, many organochlorine pesticides were created to replace inorganic pesticides to reduce the amount of pesticide sprayed and to target specific pests as the specificity of these new pesticides increased.  Thus, as less total pesticide was sprayed, it was thought that these organochlorine pesticides would have a lesser negative on the environment and ecological systems as a whole.  Here is just one example of how these new organochlorine pesticides were used.  However, these organochlorine pesticides were found to have high persistence levels and would take extremely long to breakdown.  While these pesticides remained in the environment they continued to induce negative effects to humans and the environment, such as being known carcinogens, contaminating ground water, and bioaccumulating to toxic levels in the fatty tissues of organisms.  Some examples of these persistent organochlorine pesticides are DDT, heptachlor, aldrin, dieldrin, mirex, and chlordane. 


Chlordane was used in San Diego, California until it was banned in 1988, and was primarily used to eliminate termites.  Thus, “today, people receive the highest exposure to chlordane from living in home that were treated with chlordane for termites” (Chlordane).  Also recent findings have shown that it remains to be present in Tecolote Canyon sediments.  Due to chlordane’s low polarity, it is found in highest concentrations in organic soil and sediments.  Testing of these sediments in 2005, 2007, and 2010 have illustrated the presence of chlordane within sediments in the canyon and Mission Bay, where Tecolote Creek empties.  Due to the historical presence of chlordane in sediments in Tecolote Canyon, University of San Diego students enrolled in Environmental Chemistry under the guidance of Dr. David O. De Haan sampled and tested sediments this year for the presence of chlordane.  Chlordane was spatially variable between all of the sampling sites, with the highest values found within Mission Bay.  However, as the chlordane was found in the sediment, other physical and chemical properties (water content, organic matter content, calcium carbonate content, pH level, and sediment particle size) of the sediments were analyzed to determine any potential correlations these factors might have with the retention of chlordane at these sampling sites. 

Overall chlordane concentration levels at all sampling sites did not appear to show any definitive correlations with any of the physical and chemical parameters analyzed, as positive and negative correlations were found between chlordane concentrations and each physical and chemical factor (See Table).  Thus, it could not be said with much certainty from the analysis if any of these physical or chemical factors were a factor in the retention of chlordane in Tecolote sediments.  While these results were inconclusive and indicate the need for repeated sampling and testing to achieve the goal of this experimental design, other sources of error could have led to these inconclusive results, such as other minerals being present in the sediment, as well as the oxidation of samples from their open-air storage.  Therefore, from these inconsistent results, the physical and chemical factors are not likely to be the primary factors in the retention of chlordane in the sediments in Tecolote Canyon.