# Integrative Assessment of Sediment Quality in the Sao Francisco River (Mina Gerais, Brazil)
###### Abstract  
The Sao Francisco River (one of the most important South American rivers) has many contamination sources, but just a few environmental assessments have been conducted. A weight-of-evidence approach identified the pollution sources (industrial activities, mineral processing, fisheries, and tourism) in the river and the city of Tres Marias based on two different lines of evidence: the structure of the benthic community (biological monitoring working party score system, abundance of taxa, number of individuals, Margalef species richness, Pielou evenness, and Shannon-Wiener diversity) and the physicochemical determination of sediments (%fines, TOC, nitrate, ammonium, ammonia, ammoniacal nitrogen, metalloids, and SEM/AVSs). The results show that the wastewater treatment plant was the most important source of pollution. A factory was also detected as a source of contamination, with related adverse effects having been measured downstream. Other sources of contamination and stress were detected in the studied area. The macro-bentlein identification study identified three different sentinel species (_Tanytasus_ sp., _Crydichironomus_ sp., and _Polypedilium_ sp.) for future monitoring assessments of the sediment quality in riverine areas. Thus, an improvement in the management of river effluents and more measures focused on cutting contaminant emissions from the waste treatment plant are recommended. s +
Footnote †: journal: Applied sciences  
these indicators show alterations in the communities in the studied areas [9; 10; 11]. This kind of study provides realistic information about the environmental health of aquatic ecosystems. The macro-benthic fauna plays a fundamental role in sediment processes, providing an important measure of the response of a community to environmental perturbation [12; 13; 14; 15; 16] and exhibiting the greatest potential for monitoring conditions at a particular site [17]. Biotic indices are useful tools in decision-making processes [18], and those indices synthesize complex scientific data. The structure of the macro-benthic community was analyzed using univariate measures (biological monitoring working party score system, the abundance of taxa, the number of individuals, Margalef species richness, Pielou evenness, and Shannon-Wiener diversity). The biological monitoring working party (BMWP) score system is very useful for water quality management due to its adaptability. However, the use of biotic indices has limitations, since natural variability can be difficult to establish. Therefore, reliable environmental assessment studies must integrate as much information as possible. Another line of evidence (LOE) was selected in order to establish the cause of potential alteration and/or pollution. This LOE is based on the physicochemical determination of sediments: grain size (fines), organic carbon content (TOC), chemical nitrogen (nitrate, ammonium, ammonia, and ammoniacal nitrogen), metal concentrations in sediments (Al, As, Co, Cr, Cu, Fe, Ni, Pb, Zn, and Hg), and simultaneously extracted metals-acid volatile sulfides (SEM-AVSs). The USEPA [19] establishes some benchmarks for metal(loid)s Cd, Cu, Pb, Ni, Ag, and Zn in freshwater sediments. Ref. [3] classified the toxicity of the sediments according to benthic organisms in total organic carbon fraction (f\({}_{\text{toc}}\)), but also additional elements or factors affecting the area, such as chemical nitrogen or other metals. Therefore, chemical nitrogen was analyzed mainly due to the sewage discharge and agricultural pollution in the Barreiro Grande stream. Furthermore, the concentrations of Al, As, and Fe were measured due to the proximity of the VM-TM refining factory. The main objective of this study was to establish the sediment quality in this river, addressing the main causes of the potential alteration and/or pollution with an integrative assessment. It was conducted by linking the results of the LOEs of sediment contamination and the descriptive parameters of macro-benthic community.