**3. Geochemical mapping**

Mangrove forests such as *Rhizophora* sp. (**Figure 2**) are important ecosystems ecologically and economically toward human beings and organisms that live in the mangrove area. These forests provide breeding and feeding ground for various aquatic organisms such as fishes, shellfishes, reptiles, and some land organisms such as monkeys and snakes. For example, some fishes such as sea bass, the juvenile will stay in this mangrove area before they move to the ocean when they were adult. Besides that, mangrove forest also plays an important role in protecting shorelines from erosion or in some places, minimizing the strong current from tsunami. This protection indirectly can protect the communities that

**Figure 2.** Tropical mangrove ecosystem that can be found in Malaysia coastal. Photo by Mokhtar Ishak.

**Figure 1.** Tropical wetlands ecosystem in Malaysia. Photo by Ong Meng Chuan.

30 Wetlands Management - Assessing Risk and Sustainable Solutions

Unlike other pollutants, which may be visibly buildup in the environment, trace metals in the environment may accumulate unnoticed to toxic levels. These metals pollutants in the aquatic environment can come from natural or anthropogenic sources. Metals are serious pollutant in our natural environment due to their toxicity, persistence, and bioaccumulation problems

live in coastal area.

**2. Metals pollution**

Distribution of metals in surficial sediments from industrial effluents and urban sewage discharged into the wetlands ecosystem and aquatic environment without proper cleaning can easily be identified through metals spatial variations in sediments. Geochemical mapping can be used as a tool for visualization, which enhanced by computer-aided modeling using geographical information system (GIS) to make it easier to identify the possible locations of contaminated area. Nowadays, due to the rapid developments of computer technology, GIS applications are receiving increasing interest in environmental geochemistry study [4, 5]. It is becoming increasingly popular to incorporate digitized and computerized technologies in studies of marine environmental pollution. These technologies may include GIS and global positioning system (GPS) in the interpretation and presentation of data and in geochemical modeling (**Figure 4**).

and spatial interpolation utilizes measured points with known values to estimate an unknown value and to visualize the spatial patterns [10, 11]. For example, **Figure 5** shows the concentration map of Arsenic in surficial sediment from South Brittany waters analyzed by using

Metals Pollution in Tropical Wetlands http://dx.doi.org/10.5772/intechopen.82153 33

Sediments are widely used as geo-markers for monitoring and identifying the possible sources of pollution in the coastal environments since sediments are the main sink for various pollutants (**Figure 6**). Sediments can serve as a metal pool that can release metals to the overlying water via natural or anthropogenic processes, causing potential adverse health effects to the ecosystems. Most metals are bound in the fine-grained fraction (<63 μm), mostly because of its high surface area-to-grain size ratio and humic substance content, where they have a potentially greater biological availability than those in the larger (2 mm–63 μm) sediment fraction. Meanwhile, sediment cores (**Figure 7**) can provide chronologies of contaminant concentrations and a record of the changes in concentration of chemical indicators in the environment. Metal accumulation rates in sediment cores can reflect variations in metal inputs in a given system over long periods of time. Hence, the study of sediments core provides historical record of various influences on the aquatic system by indicating both natural background levels and the man-induced accumulation of metals over an extended period

**Figure 6.** Different types of sediment can be collected from wetlands ecosystem. Photo by Ong Meng Chuan.

**Figure 7.** Core sample collected from mangrove environment used for metals proxy study. Photo by Ong Meng Chuan.

ArcGIS software 9.3.

of time.

**4. Sediment as geo-marker**

**Figure 4.** Example of geographical information system (GIS) mapping in environmental studies. Photo adapted from https://technofaq.org/posts/2017/07/thoughts-on-the-future-of-gis-what-will-change-in-50-years/ [6].

GIS is a tool for decision making, using information stored in a geographical form. Some researchers defined major requirements and functions of GIS and mentioned spatial data handling tool for solving complex geographical problems [7–9]. Besides, GIS is increasingly used in environmental pollution studies because of its ability in spatial analysis and interpolation,

**Figure 5.** Concentration of Arsenic (As) in sediment of South Brittany waters (Bay of Quiberon and Gulf of Morbihan), France. Figure by Ong Meng Chuan using ArcGIS software 9.3.

and spatial interpolation utilizes measured points with known values to estimate an unknown value and to visualize the spatial patterns [10, 11]. For example, **Figure 5** shows the concentration map of Arsenic in surficial sediment from South Brittany waters analyzed by using ArcGIS software 9.3.
