Accumulation of toxic metals and organic micro-pollutants in sediments from tropical urban rivers, Kinshasa, Democratic Republic of the Congo

Abstract

The increasing contamination of fresh water resource by toxic metals and Persistence Organic Pollutants (POPs) is a major environmental concern globally. In the present investigation, surface sediments collected from three main rivers named, Makelele, Kalamu and Nsanga, draining through the city of Kinshasa, Democratic Republic of the Congo, were characterized for grain size, organic matter, toxic metals, POPs (including organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs)), and polycyclic aromatic hydrocarbons (PAHs). Furthermore, enrichment factor (EF) and geoaccumulation index (Igeo) were performed to determine metal source and pollution status. The results highlighted high concentration of toxic metals in all sediment samples, reaching the values (mg kg) of 325 (Cu), 549 (Zn), 165 (Pb) and 1.5 (Cd). High values of PCBs and OCPs were detected in sediment samples, e.g. in Makelele river, PCB values ranged from 0.9 to 10.9 with total PCBs (∑7 PCBs × 4.3): 169.3 μg kg; OCPs from 21.6 to 146.8 with ∑OCPs: 270.6 μg kg. The PBDEs concentrations were higher in investigated rivers comparatively with values detected in many rivers from Sub-Saharan Africa. The ΣPAHs value ranged from 22.6 to 1011.9 μg kg. River contamination may be explained by local intense domestic activities, urban and agricultural runoff, industrial and hospital wastewaters discharge into the rivers without prior treatment. This research provides not only a first baseline information on the extent of contamination in this tropical ecosystem but also represents useful tools incorporated to evaluate sediment quality in the river receiving systems which can be applied to similar aquatic environments.

Occurrence, distribution and ecological risk of trace metals and organic pollutants in surface sediments from a Southeastern European river (Someşu Mic River, Romania)

“…Contrary to PCBs, we observe significant positive correlations between OM/TOC and ƩOCPs (Table S9), indicating that sediment OM and TOC could enhance the adsorption of these compounds and therefore affect their transport and redistribution in sediments. OCPs in SMR sediments samples were close to those found in the Bahlui River, Romania (Dragan et al, 2006), Ravi River, Pakistan (Syed et al, 2014) and River Po, Italy (Viganò et al, 2015), higher than those found in the Tonghui River, China (Zhang et al, 2004), Durance River and Arc River, France (Kanzari et al, 2012(Kanzari et al, , 2015), but lower than those observed in tropical urban rivers, Congo (Kilunga et al, 2017) (Table S11).…”

“…As ecologically and economically important water bodies for human living, riverine ecosystems have attracted the interest of authorities and researchers, especially after the continuous development of urban, industrial and agricultural activities, which have released into these ecosystems large amounts of contaminants (Islam et al, 2015;. Among these anthropogenic contaminants, metals, polycyclic aromatic hydrocarbons (PAHs) and persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) have caused deep concern for both developed and developing countries due to their toxicity, persistence, bioaccumulation, high long-range atmospheric transport and potentially adverse health effects on wildlife and humans (Kilunga et al, 2017;Resongles, 2014). Human activities such as mining, smelting, traffic emissions, industrial sewage and agriculture are the main sources of metals in sediments (Besser et al, 2008;Odhiambo et al, 2013).…”

Distribution and source analysis of heavy metal pollutants in sediments of a rapid developing urban river system

“…The PCA analysis provides additional support for a common source of Zn, Pb and Cd as several species of these heavy metals demonstrated a significant loading weight on PC1. Previous studies indicated that these metals could have a common source and similar transport pathways in urban rivers (Kilunga et al, 2017). Although significantly correlated with the other metals, Cu showed a different spatial pattern and high loading on PC2, which suggests a contrasting pollution source.…”

“…Metal concentrations in the Wen-Rui Tang River sediments were also elevated compared to several other rivers and lakes locally and globally (Table S2): Cu 3e14 Â , Zn 4e36 Â , Pb 1.1e10 Â times, and Cd 4e880 Â times higher than the concentrations in these other watersheds. Heavy metal contaminations in river sediments were much severer than that in Congo, which was identified with slight heavy metal pollution (Mwanamoki et al, 2014;Kilunga et al, 2017). In contrast, Cr concentrations were at levels similar to sediments from Dong Ting Lake (China), Yangtze River (China) and Red River (Vietnam), but 20 times higher than that in the Sinú River (Colombia).…”

Construction of a Self-Powered System for Simultaneous In Situ Remediation of Nitrate and Cr(VI) Contaminated Synthetic Groundwater and River Sediment

“…nitrate and Cr(VI) coexisting in groundwater using 3-dimensional bio-electrochemical systems (BES) has been achieved, but it still needs applied potentials [16].Aquatic sediment acts as a repository for multiple pollutants in rivers and lakes, and as a significant source of internal pollutants. Pollutants include organic matter, metal contaminants, and inorganic salts [17][18][19]. Organic substances play an important role in the deterioration of water quality because when it catabolized, the dissolved oxygen in water consumed, thus results in an anoxic or anaerobic condition of water.…”