SCANNING ELECTRON MICROSCOPY INVESTIGATION OF STREET SEDIMENT FROM AKUMAL, A TOURIST VILLAGE ADJACENT TO THE MESO-AMERICAN REEF IN THE YUCATAN

Akumal is a mid-sized tourist village located approximately 100 km south of Cancun on the eastern coast of the Yucatan Peninsula that receives a minimum of 10,000 tourists per year. A main attraction for the village is the Meso-American Reef which is approximately 100 to 200 m offshore from the village. The village is recognized for environmental efforts to preserve the reef, largely in the form of wide spread installation of constructed wetlands to treat sewage effluent, turtle conservation programs, reef surveys and recycling promotion. One environmental aspect that has not been investigated is the nature of metal pollution in street sediment. There is extensive vehicular traffic in the village from both tourists themselves and supporting industry traffic. A modest infrastructure exists, however no stormwater drainage system is present. Owing to the close proximity to the Meso-American reef, significant potential exists for non-point source pollution to occur.

Street sediment was collected (n=15 samples) from throughout the village to ascertain if metal particulate pollution is present. Back-scatter scanning electron microscopy (BSEM) indicates that a variety of metal–rich pollutant particles occur in samples. Zn-rich, Cr-rich and Pb-rich particles were observed. Barite was also observed. Zn and Cr-rich particles are consistent with corrosion particulate from vehicular sources. Pb-rich particles are ambiguous in origin and may be vehicular, related to fishing activities or diving activities. Barite is interpreted to be recrystallized from natural aragonite from Holocene sediment, however a coal combustion source cannot be ruled out. Particle size of metal pollutants is commonly on the order of a few to several micrometers and thus can be remobilized easily to the Meso-American reef. Results indicate that studies of stormwater runoff and some form of storm water retention should be explored. Owing to the large carbonate and carbonate sand components of sediment, Akumal provides a potentially unique setting to evaluate sourcing of urban pollution components. This investigation serves a basis for comparison to other similar settings in Mexico and the Caribbean.