Análise Geoquímica dos Sedimentos de Fundo do Arroio do Salso, Porto Alegre - RS - Brasil

摘要: This paper presents the results of a study performed on bedload samples from Salso Creek in Porto Alegre City (Rio Grande do Sul State) rural area where agricultural and pastoral activities are carried out within urban areas. Sediment sampling took place 16 th September 2001 (winter) 21 January 2002 (summer), at five sites along Creek. The bed load changes granules pebbles (upstream reaches), through coarse- to medium-grained sand (mid reaches) fine-to very fine-grained mouth region. Organic matter content increases throughout summer low discharge due accumulation suspended creek surface. Grains larger then 0.062 mm feature following estimated mineralogical composition: feldspar (55-50%), quartz (30-40%), opaque (5-10%) acessory minerals. Among fine- grained sediments (< mm) kaolinite dominates being followed by minor amount muscovite/illite as well quartz, smectite traces. chemical composition reveals that, among major (Al, Fe, Mn, Ca, Mg, Na K) trace (Cr, Cu, Ni, Pb Zn) analyzed elements, Al is high, probably result kaolinite-rich (Al 4(Si4O10)(OH)8) fraction. Geo- Accumulation Index calculation shows no significant any elements fraction, hence indicating slightly moderately polluted sediments. On other hand Contamination Factor computation for fraction pointed Ni Zn enrichment, considerable high contamination, especially those places directly under domestic sewerage influence. These concentrated load.