Abstract
It is a well–known fact that heavy metal pollution in sediments causes serious problems not only in the Danube basin, but also in the large and small adjacent river streams. A suitable method for assessing the level of heavy metals and their toxicity in sediments is the calculation of pollution indices. The present research aims to assess heavy metal pollution in the Lower Danube surface sediments collected along the Danube course (between 180 and 60 km) up to the point where the Danube River flows into the Danube Delta Biosphere Reserve (a United Nations Educational, Scientific and Cultural Organization—UNESCO, protected area). In addition, this monitored area is one of the largest European hydrographic basins. Five heavy metals (Cd, Ni, Zn, Pb, Cu) were analyzed in two different seasons, i.e., the autumn of 2018 and the spring of 2019, using the Inductively Coupled Plasma Mass Spectrometry (ICP– MS) technique. Our assessment of heavy metal pollution revealed two correlated aspects: 1. a determination of the potential risks of heavy metals in sediments by calculating the Potential Ecological Risk Index (RI), and 2. an evaluation of the influence of anthropogenic activities on the level of heavy metal contamination in the surface sediments, using three specific pollution indices, namely, the Geo–Accumulation Index (Igeo), the Contamination Factor (CF), and the Pollution Load Index (PLI). The results of this pioneering research activity in the region highlighted the presence of moderate metal (Ni and Cd) pollution and a low potential ecological risk for the aquatic environment.
Highlights
The assessment of heavy metal concentration in aquatic ecosystems represents a topic of interest due to heavy metal’s toxicity and their special property of bio-accumulation in organisms [1,2,3]
A total of 15 sampling stations were selected to assess the level of heavy metals sediment contamination (Figure 1), according to the existing pollution sources located along the lower Danube River, between 180 and 60 km
K ∗ Bn where Igeo is the index of geo accumulation for each heavy metal; Cn is the concentration of heavy metals determined in the sediment sample; Bn refers to the background value of heavy metals, K = 1.5 represents a constant, which compensates for weathering and lithogenic effects [36]
Summary
The assessment of heavy metal concentration in aquatic ecosystems represents a topic of interest due to heavy metal’s toxicity and their special property of bio-accumulation in organisms [1,2,3]. A total of 23 heavy metals are commonly found in high concentrations in the environment, which can become toxic and dangerous [4], and it is known that population exposure to heavy metals may cause serious medical problems, such as cancer, organ and nervous system damage, autoimmunity, and even death in some instances [5]. The five metals studied in this paper (Cd, Ni, Zn, Pb, Cu) are the most frequently identified heavy metals in the environment, which, in high concentrations, are considered toxic to ecosystems and human health. Studies have shown that human exposure to high levels of Cd causes kidney disease, infertility, mental, intestinal disorders and cancer [6]. The ingestion of Zn high levels can cause pancreatic complications, anaemia and
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