Abstract
This work appraises the extent of toxic trace metals and seasonal pollution degree in Damietta branch sediments of the River Nile of Egypt. The toxic trace metals Fe, Mn, Cd, Co, Cu, Ni, Pb, and Zn were analysed in sediments from six sites during the summer and winter seasons. The metal concentrations and organic matter were determined using inductively-coupled-plasma mass spectrometry and loss-on-ignition, respectively. Multivariate statistical methods were used in order to allocate the possible metals sources and their relationships in sediments. The seasonal mean sequence of toxic trace metals was: Fe > Mn > Zn > Pb > Cu > Ni > Co > Cd. The mean Cd, Pb, and Zn values exceeded the sediment quality guidelines and average shale and they represent severe potential toxicity for aquatic organisms. Cu and Co were enriched during winter. The geo-accumulation index stipulated that metal pollution degree in the sequence of: Pb > Zn > Cd > Co > Cu > Mn > Ni > Fe. The highest metal pollution index reported in winter in sites S4/S5 and during summer in sites S4–S6. Different agricultural, wastewater discharge, fisheries, and industrial activities, as well as the effect of dilution/concentration during summer/winter seasons, are the main factors that contributed to metal accumulations in Damietta branch sediments. Continuous monitoring and evaluation of toxic trace metal concentrations of the Damietta sediments and similar localities worldwide can help to protect the ecosystem from harmful metal contaminations.
Highlights
Pollution of the aquatic system by toxic trace metals is a worldwide problem, because of their toxicity, persistence, and bio-accumulation [1]
The toxic trace metal values are higher in the winter season (Table 2, Figure 2)
The results expressed in this study provide toxic trace metal data and risk research in Damietta Branch of the Nile River, which may have definite implications for toxic trace metal pollution regulation
Summary
Pollution of the aquatic system by toxic trace metals is a worldwide problem, because of their toxicity, persistence, and bio-accumulation [1]. Toxic trace metals that are added to the river bottom sediments are affected by various chemical changes. Precipitation, sorption, and organism activities can affect toxic trace metals distribution [2]. Bedrocks and bank leaching are the main lithogenic sources of toxic trace metals. Wastewater discharge, mining operations, fossil fuel combustion, manufacturing industries, etc., are the principal anthropogenic toxic trace metal pollution sources [4,5,6]. Some toxic trace metals and metalloids in high doses can be detrimental to the body while others, such as cadmium, lead, chromium, and arsenic, in little quantities, can cause acute and chronic toxicities in humans [7]
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