Application of Sediment Quality Guidelines in the Mapping of Metal Pollution in Rhumel, Boumerzoug, Enja and Kebir Rivers, and their Tributaries (Algeria): Case of One Hydrological Year Sampling
There have been numerous Sediment Quality Guidelines (SQGs) which developed to monitor the sediments. SQGs are very useful to screen sediment pollution by comparing sediment contaminant concentrations with the corresponding guidelines, provide useful tools for screening sediment chemical data to identify pollutants of concern and priorities problem sites and relatively good predictors of contaminants.
This investigation presents assessment of metal pollution in Rhumel, Boumerzoug, Enja and Kebir rivers in Kebir-Rhumel basin which occupies 8815 km² in north eastern Algeria. We apply SQGs approach to assess how well they predict sediment toxicity and mapping of polluted sites. Surficial sediments (0-5cm) were sampled in winter, spring, summer and autumn from 37 sites. Our investigations related to assessing metal pollution focused on: cadmium, chromium, copper, nickel, lead, zinc, cobalt and manganese.
Trace metal concentrations followed the order: Mn>Zn>Pb>Cr>Cu>Ni>Co>Cd. The applied guidelines verify that one or more metal are above background levels for all investigated sites. The results reveal a discrepancy between sediments quality in rivers suggesting different origins of metals. As Co present similar situations in all rivers, it can be considered as elements of natural origin. Sediments are considered moderately polluted by nickel and cadmium, and moderately to heavily polluted by chromium, copper, lead and zinc. Changing seasons and hydrological conditions seem to have little influence on the concentrations of chromium, cobalt, copper, nickel, zinc and manganese. Nonetheless, we recorded a significant increase of cadmium and lead levels in winter, probably due to soils runoff.
SQGs approach should understand how well those guidelines predict the presence or absence and extent of pollution and toxicity in sediment samples and to identify priority polluted sites. However, biological testing and ecological analysis of existing benthic community structure related to sediment pollution are needed for final decision making in the case of the studied rivers.
Keywords - Metal pollution, Mapping, Seasonal variation, Sediment Quality Guidelines, Kebir Rhumel basin