**2.1 Description of the study area**

Physical environment: Carmen City (**Figure 1**), is located southwest of the state of "Campeche", bordered to the north by the Gulf of Mexico and the municipality of "Champotón", to the south by the state of Tabasco, to the east by the municipalities of "Escarcega and Candelaria" and to the west by the municipality of "Palizada" [20].

The area of the "Terminos" lagoon includes Terminos lagoon and the adjacent fluvial -lagoon systems ("Palizada" from the east, "Chumpan-Balchacah", "Candelaria-Palau"), the lagoon complex of "Pom Atasta", "Puerto Rico", "Los Negros" and the estuary of "Sabancuy", the "Chacahito" lagoon, Carmen Island, and estuary Pargo. The study area is shown in **Figure 2**. The "Palizada" river delta-lagoon fluid system (SLFS) is in the southwestern portion of the Terminos lagoon hydrological basin between geographic coordinates 18°19′13″ and 18°29′04″ north latitude and 91°44′36″ and 91°51′31″ west longitude [20].

To carry out this study, ten points were included in the extraction of sediment samples, during two climatic seasons (2: rainy, 3: dry) in the year, which allowed obtaining significant information on the state of contamination of this important ecosystem (**Table 1**).
