Heavy Metals in Surface Sediments of the Coastal Area Around Daerah Istimewa Yogyakarta, Indonesia: Their Relations to Land-Use Types

The province of Daerah Istimewa Yogyakarta (DIY) has experienced significant changes in urbanization, industry, and tourism, making it one of Indonesia's fastest-growing areas. Increased anthropogenic activity in the coastal region may cause heavy metal contamination in that zone to grow. Based on different land-use types, this study examined the distribution of heavy metals, namely cadmium (Cd), lead (Pb), copper (Cu), and zinc (Zn), in surface sediment. It assessed the feasibility of sediment quality standards based on the Canadian Sediment Quality Guidelines (CSQG). Nine stations made up the sampling site, each representing a different land-use type, including mangrove ecosystem, tourist attraction, airport, harbor, mining area, bare land, shrimp pond, agricultural land, and settlement. The concentrations of Cd in bare land, shrimp pond, agricultural land, and settlement (with values of 2.707, 2.955, 2.983, and 2.873, respectively), and Cu in the mangrove ecosystem (with values of 42.893) slightly exceeded the corresponding Threshold Effect Level (TEL) value of CSQG. Meanwhile, the content of other heavy metals in all land use types tends to be low, even below the Limit of Detection (LOD). The data on the level of heavy metal pollution in the study area shows no connection between heavy metal contamination and different land-use types. It is brought on by a variety of circumstances, such as the fact that human activity in the study area did not significantly contribute to heavy metal contamination or that heavy metals were contaminated and then spread to other forms of land-use types, in this case, the mangrove ecosystem, by runoff and wind. This is because variations in salinity, estuary flushing, physical mixing and dilution, and chemical processes, including sorption, complexation, cation exchange, and redox reactions, all affect how heavy metals are transported by water. The government should create environmental regulations, laws, quality norms and standards, more funding for cutting-edge scientific research, and technical tools to prevent heavy metal pollution in coastal areas.