**1. Introduction**

Currently, coastal ecosystems are exposed to a large load of pollutants from urban activities; this problem is because significant amounts of waste are dumped that generally has no treatment, which contributes to increasing the concentration of certain

pollutants as heavy metals are of particular interest because they are highly persistent, toxic and can bioaccumulate in exposed organisms.

The sediments allow lies to determine, from the geochemical point of view, the content of trace metals, their possible origin (anthropogenic or natural), and the mobility that serves to infer the potential risks of toxicity for the biota. The study of sediments in an aquatic ecosystem allows a comprehensive estimation of pollution; metals associated with the organic fraction can form solutions and remain available to aquatic organisms [1].

An earlier study [2] shows the behavior of heavy metals; copper (Cu), nickel (Ni), chrome (Cr), lead (Pb), cadmium (Cd), and zinc (Zn) in sediments and organisms in Terminos Lagoon, Campeche, Mexico. The results for the sediments showed that the total levels of metals were higher on the west side of the lagoon, except for Cd and Pb, which had a high level on the east side. For the oyster (*Crassostrea Virginica*), metal levels increase in the rainy season except for Pb, which presents higher values during the northern season. The results show a tendency to increase in the levels of Cr and Pb and are related to human and industrial activities.

Petroleum hydrocarbons, heavy metals, and pesticides are the main contaminants in Mexican coastal [3]. These elements have generated harmful effects for the organisms, coastal ecosystems, and public health; however, certain metals are part of the biochemistry of living beings, are required by organisms, and are part of various metabolic processes. Some metals, such as Fe, Cu, Zn, and others, are essential elements. The problem arises when these essential elements and other nonessential elements such as Hg, Pb, and Cd are found at high levels in the organs or tissues of aquatic organisms.

Another studio [4] showed levels of heavy metals in water and sediment samples; the water samples were within the national standards for river water. However, the presence of all metals considered in the study was confirmed in the sediments, which indicates that the sediments are a reserve source of pollutants. In this same study, Cr, Pb, Fe, Ni, and Cu were very high in the sediments, mainly in summer and winter.

In Mexico, other studies [5] determined levels of Cu, Mn, Fe, Ni, Cd, Pb, and Zn in samples of oysters, water, and sediments from "San Andrés", lagoon to determine and understand the bioaccumulation mechanisms of the species and identify the potential risk for the consumption of oysters.

Several factors can predispose to the presence of heavy metals in certain studies [6], the bioavailable contents of Zn, Fe, Mn, Cu, Cr, Cd, Pb, and Ni in superficial sediments of the "Bocaripo" coastal lagoon were evaluated in two climatic periods. Showing the importance of the size and diameter of particles, the content of organic matter (OM), and the pH of the sediments.

Finally, the authors conclude that the bioavailable content of Cu may represent a potential risk of contamination and affect the mobility of other metals.

Studies carried out in the Bay of "Chetumal", Mexico [7] confirm that organic matter and other physicochemical parameters are essential in a global study of heavy metals; the authors determined the levels of Cd, Pb, Hg, and As, in surface sediments as well as organic matter and nutrients. The environmental disturbance was related to discharges of water from the "Deep River" and from the city. In spring, the highest levels were for Cd, Pb, Hg, and As. The parameters analyzed: PO4, NO3, CO3, and organic matter (OM), did not show significant variation concerning reference values of the official Mexican standards.

### *Quantification of Heavy Metal Levels in Sediments of the "Palizada" River in a Protected… DOI: http://dx.doi.org/10.5772/intechopen.104657*

The study of contamination in sediments must include the analysis of the texture and determine the relationships with the levels of heavy metals; In this sense, in studies carried out in Chile [8], the granulometric and geochemical aspects of superficial and subsurface marine sediments were analyzed; with this value, the authors determined the environmental quality of the sediments. In this sense, areas with environmental deterioration were established, generated by enrichment or contamination of some metals such as Ni, Zn, Pb, Cd, Cu, Hg, and As. The main textural fractions: are silt, sand, and clay. In this same study, high values of OM were found. The authors conclude that this area is susceptible to contamination due to its sedimentological characteristics and geomorphology.

Gonzalez et al. [9] determined significant components such as organic and inorganic matter (IM), silica, and carbonates, as well as heavy metals (Al, Fe, Mn, Cu, Zn, Pb, Cr, and Ni), sedimentation, and texture studies. The authors conclude; that the environmental problems presented by the "Copper River", like most water bodies, are due to the contributions of residual waters (the majority without treatment). One of the sources of contamination has been the "Large Copper Mine", which continues to have an impact although it is not currently being exploited. A clear example is that sediments are a reservoir of heavy metals and other pollutants.

Several authors [10] have studied the spatial and seasonal distribution of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the dissolved fractions and particles of the Port of Mazatlán (a lagoon system coast in northwestern Mexico). The authors emphasize the effect of the anthropogenic contributions of heavy metals on the concentrations in the port and the adjacent seawater, finding that the effect of said agents in both fractions is limited to the immediate area of the discharge, with concentrations from outside of the port indistinguishable about the coastal waters. It is a verifiable fact that the sediments are temporary integrators of pollution [9–11] and are affected by different physical and chemical processes, which makes the concentration of the pollutant vary between climatic seasons.

Aguilar et al. [12] demonstrated in their studies that the climatic season has a great influence on metal levels; the contents of Cd, Cu, Zn, and Fe were analyzed in surface sediments of a "The Caleta" stream in the City of Carmen, Campeche. The experimental results indicated that there was no significant difference by time and sampling site, which was an expected behavior pattern since in the dry season there are no significant contributions of water.

Certain metals such as Pb, Cd, Hg, and Ni; are a significant risk to human health, are not classified as essential, and are often toxic at low concentrations. The Cd is considered a potent carcinogen according to the International Agency for Research on Cancer (IARC) [13]. These elements are found in the soil, air, and water and can reach man through the food or water he consumes.

The damage they cause is so severe that many species show no symptoms, but they accumulate large amounts in their internal tissues and organs [14–17], from this fact derives the importance of studying marine sediments and classifying pollution and the risk to which aquatic organisms are exposed; Likewise, sediments reflect the environmental quality of an ecosystem [18, 19].

This chapter shows the results of determining the levels of Cr, Cd, Fe, Cu, Zn, and their relationship to climatic seasons in the fluvial lagoon system of the "Palizada" river, which flows into the "Terminos" lagoon.

This area constitutes one of the Natural Protected Areas of Mexico and is the habitat of various species of flora and fauna endemic to Mexico.
