5th Swiss Geoscience Meeting, Geneva 2007
Deposition of atmospheric copper and pollution history
since ca. 1850 in Central Chile
von Gunten Lucien*, Eggenberger Urs**, Grob Philipp*, Morales Arturo***,
Sturm Michael****, Urrutia Roberto ***** & Grosjean Martin*,******
* Institute of Geography, University of Bern, Erlachstr. 9a, CH-3012 Bern
(lucien.vongunten@giub.unibe.ch)
** Institute of Geological Sciences, University of Bern, Baltzerstr. 1-3, CH-3012 Bern
*** Superintendencia Geología-División El Teniente, CODELCO, Chile
**** Department of Surface Waters (SURF), Swiss federal Institute Environmental
Science and Technology (EAWAG), CH-8600 Dübendorf
***** Universidad de Concepción, Centro EULA-Chile, Concepcion, Chile
****** NCCR Climate, Erlachstr. 9a, CH-3012 Bern
In the past century, Chile has evolved to become a highly industrialized country.
Primary export good is copper, of which the government-owned company
CODELCO is the world largest producer. Mining activities begun already at the
end of the 19th century but was dramatically intensified in the middle of the 20th
century. Recently a first record of fossil fuel pollution in central Chile was
presented by Chirinos et al. (2006), showing that near industrial centres a clear
pollution signal peaking in the early 1990’s due to the burning of oil is recorded
in lake sediments. However the presence of a long distance transport to remote
areas of fly-ashes (SCP’s, spheroidal carbonaceous particles) which are used
as indicators for combustion of fossil fuels (Rose 2001), could not be
corroborated in this study. Furthermore, there is an environmental concern
about excess atmospheric Cu deposition due to the large Cu mines in Central
Chile and the North. Long-term data are not available and the pre-industrial
background (natural environmental baseline) of Cu deposition and
concentration in soils and lakes is not known.
In addition to the industrialization, population grew rapidly during the last
century to reach 16 Mio of citizens nowadays, of which 85% live in the major
urban centres. Approximately 6.5 Mio live in the capital, Santiago de Chile.
Eutrophication of the lakes near populated area in Central Chile due to
recreation activities and agriculture is well documented (e.g. L. Aculeo, Jenny et
al. 2002), but little is still known about atmospheric deposition in the more
pristine areas in the high Andes.
The aim of this study is to investigate if a signal of the rapidly growing copper
mining industry in the past centuries is recorded in the sediments of two small
high Andean lakes situated relatively closely to mines, and of a larger lake
situated near Santiago. Furthermore, we analyse the sediments for pollution
and eutrophication in order to infer differences of the human impact in remote
mountain regions and in the metropolitan region near large cities.
Laguna el Ocho (34°02'S/70°19'W, 3250m a.s.l.) and Laguna Ensueño
(34°02'S/70°20'W, 3180m a.s.l.) are situated in the vicinity of the biggest
underground copper mine in the world (El Teniente, CODELCO, >400’000 tons
of copper per year). Due to its remote location in high elevation and with difficult
access, the direct human impact is expected to be small. On the other hand, the
5th Swiss Geoscience Meeting, Geneva 2007
influence of air transported copper from the mine should be observable, as the
distance (beeline) to the smelting area is only approx. 10 km.
Laguna Aculeo (33°50'S/70°54'W, 350m a.s.l.) is in contrast situated in a more
densely populated region surrounding Santiago and further away from the
copper mine (50km, beeline). There we expect a strong eutrophication signal,
whereas the copper deposition should, if recorded, be much weaker.
During field campaigns in the years 2005 and 2006, we collected sediments
cores in the deepest part of the lakes. The ongoing analysis on the sediment
samples include XRF (x-ray fluorescence) to measure the copper content, C/N
analysis to record changes in the organic carbon and nitrogen flux, and the
counting of SCP’s to infer changes in the deposition due to fossil fuel
combustion. To date the sediments, Pb-210 and Cs-137 are measured.
First results show a doubling of the copper excess (standardized against Rb
and Zr) in the lake sediments of Laguna Ensueño compared to the
environmental baseline and even a factor 3 to 4 increase in Laguna el Ocho
since the onset of the mining activities at the beginning of the last century. In
Laguna el Ocho, in the uppermost part of the sediments copper excess
however shows a decreasing trend which is probably related to the impact of
technology changes in recent years with the installation of dust filters and fume
traps in two gas treatment plants built in the smelting and Cu processing line.
An eutrophication signal is also recorded, but the major nutrient enrichment
does not occur simultaneously with the main raise in the copper concentration,
but seems to have begun only in the second half of the 20th century.
REFERENCES
Chirinos, L. et al. 2006: Environmental evidence of fossil fuel pollution in
Laguna Chica de San Pedro lake sediments (Central Chile). Environmental
Pollution 141, 147-256.
Jenny, B. et al. 2002: Moisture changes and fluctuation of the Westerlies in
Central Chile during the last 2000 years. The Laguna Aculeo record (33°50’S).
Quarternary International 87, 3-18.
Rose, N. 2001: Fly-ash particles. In: Tracking environmental change using lake
sediments. Volume 2: Physical and geochemical methods (Ed. by Last, W.M. &
Smol, J.P.). Kluwer academic publishers, The Netherlands