ABSTRACT: Extraction of K and Mg with boiling 1 mol L-1 HNO3 in an open system for predicting K and Mg uptake by plants is a method of low reproducibility. The aim of this study was to compare the extraction capacity of different acid methods relative to hydrofluoric acid extraction for K and Mg. A further objective was to develop a chemical extraction method using a closed system (microwave) for nonexchangeable and structural forms of these nutrients in order to replace the traditional method of extraction with boiling HNO3 on a hot plate (open system). The EPA 3051A method can be used to estimate the total content of K in the clay fraction of soils developed from carbonate and phyllite/mica schist rocks. In the clay fraction of soils developed from basalt, recoveries of K by the EPA 3051A (pseudo-total) method were higher than for the EPA 3052 (total hydrofluoric extraction) method. The relative abundance of K and Mg for soils in carbonate rocks, phyllite/mica schist, granite/gneiss, and basalt determined by aqua regia digestion is unreliable. The method using 1 mol L-1 HNO3 in an closed system (microwave) showed potential for replacing the classical method of extraction of nonexchangeable forms of K (boiling 1 mol L-1 HNO3 in an open system - hot plate) and reduced the loss of Si by volatilization.

Solos com alta acidez e baixos teores de bases trocáveis podem ser a causa da baixa produtividade de plantios de Pinus taeda, em Jaguariaíva, PR, Brasil. O objetivo deste estudo foi avaliar o efeito da calagem e adubação aplicadas sobre a serapilheira, em duas áreas com Pinus taeda. Foram avaliadas as concentrações de K+, Ca2+ e Mg2+ no solo, serapilheira e acículas, além dos parâmetros da acidez do solo. Sete tratamentos foram aplicados: (i) completo (N, P, K, Zn, Cu, B, Mo e calagem); (ii) omissão de N, P e K; (iii) omissão de Zn, Cu, B e Mo; (iv) omissão de K; (v) omissão de Zn; (vi) omissão de calagem; (vii) controle. As amostras de solo foram coletadas nas profundidades de 0-5, 5-10, 10-20, 20-40 e 40-60 cm, simultaneamente às amostras de serapilheira. Foram coletadas amostras de acículas do primeiro e segundo lançamentos. A calagem induziu ao aumento do pH, Ca2+ e Mg2+ no solo, ocorrendo o oposto com os teores de Al3+ e saturação por Al. A adubação promoveu incremento nos teores de K+ no solo, serapilheira e acículas. Não ocorreu variação nas concentrações de Ca e Mg nas acículas em relação aos tratamentos.

Soils with high acidity and low exchangeable bases may be responsible for low yields of Pinus taeda in a forest plantation at Jaguariaíva, Paraná State, Brazil. The aim of this study was to evaluate the effect of liming and fertilisation, applied over litter, on two selected areas with Pinus taeda plantations. Soil, litter and pine needles were evaluated for K, Ca and Mg concentrations and soil acidity parameters. Seven treatments were applied: (i) complete (N, P, K, Zn, Cu, B, Mo, and lime); (ii) without N, P, and K; (iii) without Zn, Cu, B, and Mo; (iv) without K; (v) without Zn; (vi) without lime; and (vii) control (without nutrients and lime). Soil samples were collected at five soil depths (0-5, 5-10, 10-20, 20-40 and 40-60 cm) simultaneously with litter samples. Needles were also collected from the first and second pine flushes. Liming induced soil pH, Ca2+, and Mg2+ increases, and the opposite was observed for Al3+ and Al saturation. Fertilisation increased soil exchangeable K+ concentrations and needle and litter K concentrations. The low Ca and Mg concentrations found in the plant needles might be attributable to their low mobility.

Lead metallurgy at Adrianópolis is the largest environmental problem of Paraná, Brazil. The objective of this study was to determine Pb and Zn levels in water and sediment in two catchments by different extraction methods. The high levels of lead in water in most of samples do not allow the human use. Total Pb concentration as high as 795.3 µg L-1 was observed in Ribeira River bank, in a pluvial water stream flowering from a abandoned factory. Due to the high Pb levels in sediments from some sites (maximum of 24,300 mg kg-1) is recommended to avoid the water turbulence.

O estudo de cinética de liberação de metais pesados é uma importante ferramenta de diagnóstico ambiental de áreas contaminadas, pois determina, além dos teores acumulados liberados após tempos crescentes de equilíbrio, a taxa (velocidade) de dessorção desses poluentes para a solução do solo. Com o objetivo de avaliar a cinética de liberação de Pb de solos da área de mineração e metalurgia de metais pesados, no município de Adrianópolis (PR), vale do rio Ribeira, selecionaram-se oito solos, submetidos a diferentes formas de contaminação (solos 2, 4 e 5 - incorporação de resíduos da metalurgia de metais pesados aos perfis; solos 3, 6 e 7 - adição de Pb particulado via chaminés da fábrica; solo 8 - contaminação por passagem da água pluvial pela fábrica desativada, que escorre em direção ao rio Ribeira). O solo 1, sob mata nativa, fora da direção de caminhamento das fumaças da metalurgia, localizado a 1.560 m de distância e a 380 m acima da cota da fábrica desativada, foi escolhido como referência dos teores naturais de Pb dos solos da região. As amostras de solo, coletadas em duas profundidades (0 a 10 e 20 a 40 cm), foram submetidas a extrações sequenciais com ácido cítrico 0,1 mol L-1 após diferentes períodos de contato (tempos acumulados: 2, 14, 38, 86, 182, 326, 518, 806 e 1.382 h). Os teores totais de Pb (extração com HF e HNO3 concentrados e H2O2 30 % v/v) foram altos (máximo de 24.755,6 mg kg-1) e indicaram intensa contaminação dos solos. Os dados da cinética de liberação foram ajustados às equações parabólicas de difusão, sendo a liberação do Pb gradual e bifásica, com velocidade de liberação maior na primeira fase. Os solos 3 e 5 foram considerados com elevado potencial de contaminação ambiental devido aos altos teores de Pb dessorvido acumulados nas extrações sequenciais com ácido cítrico (máximo de 18.577,4 mg kg-1). O solo 6, com baixos teores de argila, apresentou a maior velocidade (taxa) de dessorção de Pb.

Kinetics studies of heavy metal release are an important form of environmental diagnostics in contaminated areas, due to the possibility of determining, aside from the total release contents after increasing equilibrium times, the rate (velocity) of heavy metal to soil solution. The objective of this study was to determined Pb kinetics release from soils of the heavy metal mining and metallurgy area in Adrianópolis (PR), Brazil, in the Ribeira river valley. Eight soils were exposed to different contamination forms: (soils 2, 4 and 5 - residue incorporated in the soil profile; soils 3, 6 and 7 - sprinkled with particulate matter from the factory chimney; soil 8 - contamination by rain water flowing from the shut down factory towards the Ribeira river). Soil 1, under native forest, was chosen as reference of the natural soil Pb levels. The soil samples, collected from two layers (0-10 cm, 20-40 cm), were subjected to sequential extractions with 0.1 mol L-1 citric acid during different periods (2; 14; 38; 86; 182; 326; 518; 806; and 1,382 h). The high total Pb contents (extracted by concentrated HF and HNO3 and 30 % (v/v) H2O2) (maximum content of 24,755.6 mg kg-1) revealed intense soil contamination. The release kinetics data were fitted to parabolic equations of diffusion; lead release was gradual and biphasic (higher in the first phase). The environmental risks were considered high in the soils 3 and 5, where the evaluated levels of total Pb accumulated were high (reaching 18,577.4 mg kg-1). The Pb release rate was highest from soil 6, where clay content was low.