Analytical and chemometric characterization of the Cruces River in South Chile

The Cruces River, which is located in southwest Chile, suffered from dramatic changes after the opening of a large pulp mill in 2004. A large mass mortality of the vegetation occurred. In particular, the Brazilian elodea (Egeria densa), which is the main food source of many water birds in this ecosystem, disappeared. Because of this damage, different investigations took place and the goal of this research was a description of the water quality, including filtrate, suspended matter, and sediment. In this research, inorganic parameters were the main point of interest. Furthermore, finding relations between the sampling sites and the measured parameters by applying chemometric methods was another aim of this investigation.

Water and sediment samples were collected from 19 sampling sites at the Cruces River in summer (February) 2007. Fifteen elements were analyzed by atomic spectroscopic methods in filtrate, suspended matter, and sediment. Furthermore, the dissolved organic carbon, humic acids, and microbiological parameters were examined.

The quantitative description of the three different compartments indicates little influence of the pulp mill on the Cruces River. The comparison of the results with the Databank for Ecotoxicological Effect Data and Quality Targets illustrates the good quality of the water in the sanctuary. All quality targets, except for copper, are achieved. The amount of suspended matter increases with the beginning of the wetland. The multivariate statistical data analysis classifies the relations between the objects and variables.

The influence of the sewage, which is blamed to be the reason for increased amount of suspended matter, cannot be evaluated by this investigation. The slight increase of the concentrations of the earth alkaline and alkaline metals might cause changes in the chemical equilibrium and, therefore, the amount of suspended matter increases. Applying cluster analysis separates sampling sites by the determination of similarities between these sampling sites by means of the variables. Space-time factor analysis revealed relations between the examined parameters.

The sewage of the pulp mill is not significantly polluted by the analyzed parameters and a negative influence to the ecosystem cannot be proved.

The impact of copper should be examined in further investigations. The Pichoy River, with high concentrations of iron in the filtrate, should be examined as well. Studies about the chemical equilibrium of iron and manganese oxides in relation to the alkaline and earth alkaline elements should take place.