Assessment of heavy metal pollution in marine sediments from southwest of Mallorca island, Spain

Abstract

Anthropogenic activities in urban, agrarian, or industrial areas are the main cause of heavy metals in sediments worldwide. Since the 1960s, there have been submarine discharges through outfalls of poorly treated or untreated wastewater on the south coast of Mallorca island (Mediterranean Sea). In this study, the pollution of marine sediments is analyzed at a great number of points on the south of the seacoast. Heavy metal concentrations of As, Ba, Cd, Cr, Cu, Hg, Ni, Pb, Se, V, and Zn, total inorganic carbon (TIC), sulfur, mineralogy, and grain size were analyzed. The objective is to evaluate the concentrations of toxic substances and their spatial distribution and ranges that can negatively affect marine ecosystems and human health. In addition, the results obtained have been compared with standardized indices for marine sediments, and a regional index has been developed with the background values of heavy metals obtained in the sediments of the study area. To obtain consistent conclusions, concentrations of heavy metals were classified with the Igeo Index. The concentrations of heavy metals obtained show that a great number of samples exceeded the limits considered for uncontaminated sediments according to the index applied. Elements such as Hg, Ba, Pb, and Cu showed high concentrations close to the outfalls and lower concentrations in zones far from these points. To support the assessment, chemical processes such as dissolution or chemical precipitation have been studied. The results also show that marine sediments can be a good trap for chemical elements and a good proxy to analyze the impact of anthropogenic activities in areas heavily pressured by humans, and the risk to the environment and human health.

Assessment and Review of Heavy Metals Pollution in Sediments of the Mediterranean Sea

“…The study emphasizes, despite the abundance of available studies focused on the contamination of marine sediments [1,2,5,9,[14][15][16]21,[24][25][26][27][28] to date, that no comprehensive investigation has been found for the sources of discharges and processes in marine zones close to highly populated areas, which are considered complex. However, bibliography detailed that as the world population grows and human activities expand, it is essential to minimize anthropogenic impacts on coastal and marine ecosystems [1,2].…”

“…Coastal and marine environments represent a crucial interface between human society and the natural world. Moreover, they also function as the primary sink of heavy metals, making them valuable indicators of marine sediment pollution [1,2]. These accumulated elements could be a contamination risk, releasing toxics elements through chemical and biological processes [3][4][5].…”

“…For instance, tourist destinations such as Mallorca Island, southern Spain, Greece, and southern Italy witness an influx of more than 50 million visitors annually, mainly during the spring and summer seasons. In these periods of high population rates, a substantial volume of poorly treated wastewater is discharged, introducing heavy metals into the sea and later into the marine sediments [2,19,20].…”

“…These indices assume that there is a threshold concentration of chemicals in sediments, below which ecosystems are considered unharmed, thus serving as essential tools for detecting contaminated areas. Furthermore, the concentration of heavy metals in marine sediments is classified from highly to slightly contaminated based on background levels [2,27,28].…”

The long-term evolution model of metallic contamination of Monastir-Sayada Coast as deduced from the geochemical and statistical analysis

“…The Mediterranean Sea is facing a serious threat to its health and is considered the most endangered ecosystem (Xia et al 2020). This is primarily due to human activities such as intense development, agricultural practices involving chemicals, and the high number of tourists visiting the region (Juśkiewicz et al, 2022;Tlig et al, 2023;Ardila et al, 2023). Trace metal pollution is a major concern, as these pollutants are persistent, toxic, and can accumulate in organisms (Ahmed et al, 2022;Chen et al, 2018;Zhao et al, 2019).…”