The research grant supported by the Center for Latino and Latin
American studies was to evaluate sorption and biodegradation of
methyl tert-butyl ether (MTBE) on
lacustrine
clays from Mexico. MTBE is an additive in gasoline that allows
for cleaner burning of fuels to improve air quality. However,
the use of MTBE has resulted in contamination of groundwater and
is currently the largest ground water contaminant in the USA.
In Mexico, MTBE has been blended in the two types of gasoline
(Magna-Sin and Premium) and is sold by the state oil company (PEMEX).
The aquifer that underlies Mexico D.F. stores a great volume of
water, but is strictly restricted due to subsidence that affects
this zone. Consequently, other sources of uncontaminated drinking
water are needed to supply water in the metropolitan area. One
of these alternative sources is the Chalco Basin. The research
grant allow us to survey the Chalco Basin (August 13-21) and to
collect lacustrine clay samples from the aquitard to determine
if this clay will sorb MTBE thus protecting the underlaying aquifer.
In addition, it was possible to connect a geological perspective
with the social aspects and the problems of public administration
that affect this zone.
The fieldwork started at the southeast
of the Chalco plain, at an industrial corridor close to the Mexico-Puebla
highway. In this location one continuous aquitard core sample
was collected from the surface to a depth of 2.5 m. This area
has an industrial infrastructure consisting of an electronic plant,
a palette construction company, and jeans manufacturing company
just to name of few. A sewage canal surrounds the zone with an
agua potable pumping station located just 300 m away. Over the
last few years the area has also seen bigger domestic settlements
within meters of the sewage canals. The presence of many new gas
stations and the increase of traffic demonstrate the importance
of this study. 
The second core sample was obtained in the town of Chalco, which
is a semi-urban zone where the water supplies, sewage drainage
and other public services are scarcely present. The quality of
the groundwater is directly related with the quality of life and
the well being of the population. In this area, groundwater studies
by the government and other institutions have focused on the distribution
of water and the number of supply wells but very few have focused
the potential for contamination. Since the groundwater level is
shallow (around 1.5 m) the potential for contamination can directly
affect the inhabitants, especially the children.
The third day, we collected two core samples in locations at the
central and the edge of the basin at San Miguel Xico and Sta.
Cruz Mixquic. In this area, the groundwater quality is influenced
by surface agricultural practices and increased population density.
The clays in this region were richer in organic matter and were
formed under different geological conditions from the two first
samples. Gas stations were not located in this area, however,
these locations are growing in population and there is a strong
presence of transport activities.
The Chalco Basin represents different social situations with different ways to obtain water. In the town of Chalco and the industrial corridor, the delivery of water is by trucks (pipas) distributing water to homes that originated from the agua potable pumping station located in the industrial corridor or from local wells. One concern expressed from the local people is that they think that contamination is present in the water. They have detected bad smells, bad colors, and people get sick easily if then they do not boiled the water. Even though the distribution of water is an immense problem for the whole area, the people around the Xico and Mixquic have the opportunity to use artesian wells that makes a positive difference in the quality of their life.
Overall, the fieldwork was successful and will allow for completion
of research on sorption of MTBE to clays. Beyond the goal of obtaining
samples, it was clear from visiting these areas the importance
of environmental geological studies at the Chalco Basin and the
necessity to continue with this type of research.