Heavy Metal Contamination of Urban Mangrove Sediments and Their Environmental Significance in the Zhanjiang Bay

Abstract

Urban mangroves can be used to measure the impact of human activities on the urban ecological environment because mangroves are sensitive to human activities. However, studies on the evaluation of heavy metal elements in urban mangroves are still limited. Consequently, this study selected the urban mangroves in a central commercial area of Zhanjiang Bay as a case study to investigate the content and distribution of the heavy metal elements in mangrove sediments. Combined with the results of elemental analysis, grain size analysis, risk level, influencing factors, and sources of heavy metal pollution in the surficial sediments of the mangroves in the study area were evaluated based on mathematical models and multivariate statistical analysis. The results show that (1) concentration of heavy metals: V> Pb> Cu> Ni> As> Co> Cd> Hg; (2) the content of the eight heavy metal elements has a significant positive correlation with total organic carbon (TOC) and total nitrogen (TN) values, likely as a result of adsorption, complexation, or precipitation of heavy metals by organic matter in the sediments; (3) the mangrove sediments in the study area are affected by heavy metal pollution, among which Cd pollution is the heaviest, followed by Hg pollution; (4) comprehensive analyses of multiple heavy metals using Potential Ecological Risk Index shows that the risk level of the study area is slight to very strong ecological risk; (5) the heavy metals in the study area are mainly derived from human activities such as urban domestic sewage, transportation, and ship pollution.

Tidal variation modulates the dissolved silicate behavior and exchange flux across the semi-enclosed bay‐coastal water continuum, China

“…Excessive nutrient levels cause eutrophication of water bodies and even natural calamities like red tides (Liu et al, 2011;Guo et al, 2012). Conversely, very low nutrient levels may cause disturbances in nutrient stoichiometry, hinder phytoplankton normal growth, and affect the balance of marine ecosystems (Bricker et al, 2003;Zhou, 2021). Dissolved silicate (DSi) is a crucial nutrient for diatom breeding (DeMaster, 1981;Papush et al, 2009;Cao et al, 2020).…”