Effects of Mining Activities on Heavy Metal Concentrations in Water, Sediment, and Macroinvertebrates in Different Reaches of the Pilcomayo River, South America

Abstract

From 1997 until 1999 the extent and the ecological effects of zinc, copper, lead, and cadmium pollution were studied in different reaches of the South American Pilcomayo River. A comparison of metal concentrations in water, sediment, and chironomid larvae, as well as the diversity of macroinvertebrate species, was made between sites near the origin of the Pilcomayo River, with hardly any mining activities, sites in the Potosí region, with intensive mining, and sites located 500 km or further downstream of Potosí, in the Chaco plain. Samples were also collected in an unpolluted river (Cachi Mayu River) and in the Tarapaya River, which is strongly contaminated by mine tailings (1000 tons a day). The upper parts of the Pilcomayo River are strongly affected by the release of mine tailings from the Potosí mines where mean concentrations of lead, cadmium, copper, and zinc in water, filtered water, sediment, and chironomid larvae were up to a thousand times higher than the local background levels. The diversity of the benthic macroinvertebrate community was strongly reduced in the contaminated parts; 97% of the benthic macroinvertebrates consisted of chironomid larvae. The degree of contamination in the lower reaches of the river, however, was fairly low because of sedimentation processes and the strong dilution of mine tailings with enormous amounts of clean sediment from erosion processes. Analysis of sediment cores from the Ibibobo floodplain, however, reveal an increase of the heavy metal concentrations in the lower reaches since the introduction of the contaminating flotation process in the mine industry in 1985.

Seasonal variations of metal concentrations in periphyton and taxonomic composition of the algal community at a Yenisei River littoral site

“…Concentrations of Cu, Ni and Pb were practically the same as those reported for many unpolluted rivers [22][23][24]. Even the maximum concentration of Cu in the Yenisei water was 2.5 times less than limit of tolerance of highly sensitive stream algae [25].…”

“…Even the maximum concentration of Cu in the Yenisei water was 2.5 times less than limit of tolerance of highly sensitive stream algae [25]. The concentration of Zn in Yenisei water was about three times less than in some other unpolluted rivers [22,23], except for a South American river which had a very low Zn concentration [24]. In a Spanish river, concentrations of K, Na, Ca and Mg were about one order of magnitude higher than those detected in the Yenisei site [26], but aquatic concentrations of these metals in an undisturbed North Carolina forest stream were two-to four-fold less than those in the Yenisei River [27].…”

Analysis of benthic macroinvertebrates and biotic indices to evaluate water quality in rivers impacted by mining activities in northern Chile

“…Therefore, our results may suggest that the mining impact could be stronger than natural processes in affecting the benthic fauna, in line with the reports by Petrin et al (2007), who showed through a meta-analytic approach based on 60 datasets, that macroinvertebrate species richness declines three times more rapidly with increasing acidity when the water acidity is of human origin (by the release of acidifying substances and metal-rich drainage) than when it is natural. The effects of impacts related to mining activities on aquatic invertebrates are relatively well known (e.g., Smolders et al, 2003;Harding, 2005;Pond et al, 2008;Van Damme et al, 2008). Despite the fact that the effects of metal toxicity on invertebrates are complex and vary from taxon to taxon (Harding, 2005), large increases in certain ions can disrupt water balance and ion exchange processes and cause organism stress or death of some less tolerant groups (Pond et al, 2008).…”

Impact of heavy metals on water, fish (Cyprinus carpio) and sediments from a water tank at Tumkur, India

“…Thus, the BAFs appear to be largely independent of the bioavailability values. This means that some heavy metal accumulation in fish could depend not only on the concentration of the metal in the water column but also on the abiotic features of the environment (eg., pH, Redox potential, alkalinity and salinity), and the duration of exposure (Protasowicki and Chodyniecki 1988, Cain et al 2000, Jezierska and Witeska 2001, Martinez et al 2002, Witeska and Jerierska 2003, Smolders et al 2003.…”