Impacts of Human Activities and Environmental Changes on Spatial-Seasonal Variations of Metals in Surface Sediments of Zhanjiang Bay, China

Abstract

This study investigated the total concentrations and geochemical compositions of metals (Cd, Cr, Cu, Ni, Pb, Zn, Fe and Mn) in surface sediments of Zhanjiang Bay (ZJB) in spring and summer, to assess the contamination status, mobility and influencing factors of spatial-seasonal changes of these metals. The average total concentration for each studied metal in the surface sediments of ZJB was 0.173 μg/g for Cd, 58.25 μg/g for Cr, 17.11 μg/g for Cu, 16.89 μg/g for Ni, 28.70 μg/g for Pb, 67.91 μg/g for Zn, 30.18 mg/g for Fe, and 275.5 μg/g for Mn during the investigation period. Generally higher total concentrations of metals were found in the channel and coastal sediments of ZJB compared with those in the central ZJB, which may be probably resulted by the input of Suixi river, domestic sewage and industrial wastewater. The grain size compositions and TOC contents also had influences on the distributions of metals in ZJB. In the channel, total metals and reducible and bioavailable fractions of metals generally showed decreased concentrations in summer compared with those in spring, suggesting the release of metals from sediments. Organic matter degradation and Fe and Mn (hydr)oxides reduction processes may contribute much to this phenomenon. Relatively high proportions of Cd and Zn (average of 21.7% and 14.6%, respectively) were associated with the acid soluble fraction, indicating their high risk to the environment. The combined assessment results of enrichment factor, contaminated factor and the percentages of acid soluble fraction indicated that Cd and Zn in the surface sediments of ZJB were generally contaminated and they had medium to high risk to the environment. The average values of pollution load index in the channel, coastal and central ZJB were 1.28, 0.93 and 0.81, respectively, indicating the deterioration of surface sediments in the channel of ZJB. More attention should be paid on the metals in surface sediments of the channel of ZJB.

Spatial distribution of trace elements and potential contamination sources for surface sediments of the North-Western Black Sea, Romania

“…Numerous studies in the related literature reported that clay, silt, and organic matter particles are important carriers of TEs in sediments (Rubio et al, 2000;Vaalgamaa and Korhola, 2004;Selvam et al, 2012;Özkan, 2012;Dou et al, 2013;Hu et al, 2013;Xu et al, 2016;Zhao et al, 2017;Perina et al, 2018;Remeikaite-Nikienėet al, 2018;Sun et al, 2020; Values of Pearson correlation coefficient (r) highlighted in bold are different from 0 with a significance level a = 0.05. Wang et al, 2021;Zhou et al, 2022). On the one hand, the finer sediment fractions (clay and silt) have a higher specific surface area than the coarser fraction (sand), giving them more binding sites for the adsorption of TEs and organic matter (Rubio et al, 2000;Xu et al, 2016;Zhou et al, 2022).…”

“…Wang et al, 2021;Zhou et al, 2022). On the one hand, the finer sediment fractions (clay and silt) have a higher specific surface area than the coarser fraction (sand), giving them more binding sites for the adsorption of TEs and organic matter (Rubio et al, 2000;Xu et al, 2016;Zhou et al, 2022). On the other hand, the organic matter coatings in these fine-grained sediments retain a variety of TEs (Rubio et al, 2000).…”

“…Trace elements (TEs) found in the coastal and marine ecosystems have become a serious concern towards ecological and human health risks due to their multiple sources, nonbiodegradability, toxicity, bioaccumulation, and biomagnification along the aquatic food chain (Zhao et al, 2017;Wu et al, 2022;Zhou et al, 2022). They come from either natural sources (e.g., river discharges, rainwater runoff, volcanic eruptions, wildfires, sand/ dust storms, rock/soil weathering and erosion) or anthropogenic ones (including port activities, coastal tourism, discharges of domestic, municipal, agricultural, and industrial effluents into water bodies, burning of fossil fuels, waste incineration, construction, mining, and quarrying activities, crude oil refining and other industrial processes, offshore drilling for crude oil/gas and related transport) (Sańchez-Garcıá et al, 2010;Romano et al, 2022).…”

“…Accumulation of TEs in marine sediments depends on various factors, e.g., water depth, water physicochemical properties (pH, salinity, temperature, dissolved oxygen and organic matter content), sediment composition and texture, intensity/direction of winds, waves, and currents, fluvial, atmospheric, and other natural or anthropogenic inputs (Oros, 2019;Constantinescu et al, 2023). Multivariate analysis, especially PCA, is widely used to identify the main factors affecting the concentration of TEs in sediments and possible pollution sources/transport pathways (Martins et al, 2012;Kahal et al, 2018;Remeikaite-Nikienėet al, 2018;El-Sorogy et al, 2020;Perumal et al, 2021;Vilhena et al, 2021;Wang et al, 2021;Kubra et al, 2022;Zhou et al, 2022).…”

Spatial and seasonal characteristics of dissolved heavy metals in the seawater of Beibu Gulf, the Northern South China Sea

“…Previous studies have reported that higher heavy metal contaminations were observed around the southern coast of Hainan Island, which likely originated from pollution discharge by intensive human activities, such as industrial discharges from port and shipping facilities, agriculture wastes, domestic sewage and frequently fishing activities (Yang et al, 2004;Li and Huang, 2012;Wang et al, 2013;Yang et al, 2019). In addition, with the rapid development of urbanization and industrialization, higher heavy metal contaminations have also been found in the Pearl River Estuary and the coastal waters of western Guangdong Province (Li et al, 2007;Zhang et al, 2010;Zhang et al, 2015;Zhang et al, 2018;Zhang et al, 2022b;Zhou et al, 2022). The higher heavy metal contamination in those regions would enter into the Beibu Gulf with the water masses, resulting in higher concentrations of heavy metals occurring in the offshore areas of the Beibu Gulf.…”