Assessing soil contamination in automobile scrap yards by portable X-ray fluorescence spectrometry and magnetic susceptibility.

A by-product of industrialization and population growth, automobile scrap yards are a potential source of metal contamination in soil. This study evaluated the use of portable X-ray fluorescence (pXRF) spectrometry and magnetic susceptibility (χ) analysis in assessing metal soil contamination in scrap yards located in Brazil. Five automobile scrap yards were selected in Curitiba, Paraná State (CB1, CB2, and CB3) and Lavras, Minas Gerais State (LV1 and LV2). By evaluating metal concentrations and geoaccumulation index values, we verified moderate Cu, Pb, and Zr contamination and moderate to high Zn contamination, primarily in the topsoil (0-10 cm). Soil Zn concentrations in automobile scrap yards were on average four times higher than in reference soils, suggesting that galvanized automobile parts may be the primary source of this soil contaminant. Although other elements (i.e., As, Cr, Fe, Nb, Ni, and Y) were slightly increased compared to reference values in one or more soils, concentrations did not constitute contamination. Automobile scrap yard topsoil had higher χ values (5.8 to 52.9 × 10-7 m3 kg-1) at low frequency (χlf) compared to reference soil (3.6 to 7.5 × 10-7 m3 kg-1). The highest values of χlf occurred in LV soils, which also represented the highest Zn contamination. Magnetic multidomain characteristics (percent frequency-dependent susceptibility between 2 and 10) indicated magnetic particle contributions of anthropogenic origin. The use of pXRF and χlf as non-destructive techniques displays potential for identifying soil contamination in automobile scrap yards.

Clay mineralogy affects the efficiency of sewage sludge in reducing lead retention of soils.

Recent studies have shown the feasibility of using of sewage sludge for the remediation of heavy metal-contaminated soils. However, there are no researches to check the influence of clay mineralogy on the efficiency of the sewage sludge to remediation of contaminated soils with heavy metals. For this purpose, we use two contrasting soils: Oxisol rich in hematite and gibbsite and Inceptisol rich in kaolinite. Thermal-treated sludge was applied to Pb-contaminated soil samples and incubated for 40 days. The soil samples were submitted to seven sequential extractions: soluble-Pb, exchangeable-Pb, precipitated-Pb, organic matter-Pb, Fe and Mn oxide-Pb, gibbsite and kaolinite-Pb, and residual-Pb. The reduction of soluble Pb forms by thermal sludge application was more pronounced in the Oxisol than in the Inceptisol because of the conversion of soluble-Pb into more stable forms, such as precipitated-Pb and oxides-Pb. For Inceptisol was necessary to apply high rates of thermal sludge to reach a significant reduction in soluble-Pb contents. The addition of humic fractions in the form of thermal sludge increased the concentration of organic matter-Pb. In confined area, the use of sewage sludge to reduce the heavy metals levels in soils must be better considered, mainly in more weathered soils.

Elemental composition and nutritional value of Araucaria angustifolia seeds from subtropical Brazil.

Consumed by populations in South America, Araucaria angustifolia seeds have received little study regarding elemental composition and nutritional value. Thirty-five seed sites from subtropical Brazil were sampled and seed concentrations of C, N, K, Ca, Mg, P, Fe, Zn, Mn, Cu, Mo, Ni, Co, Cr, Ba, and Cd were determined. The highest concentration of N was observed in samples from regions with Cfa climate (humid subtropical, oceanic climate, without dry season with hot summer) and igneous rock, which was superior to regions with Cfb climate (humid subtropical, oceanic climate, without dry season with temperate summer) and metamorphic rock. Seeds can be a source of nutrients: K (11.8 g kg-1), P (4.1 g kg-1), Mn (9.1 mg kg-1), Cu (7.2 mg kg-1), Mo (0.93 mg kg-1), and Cr (0.65 mg kg-1). Values for Ba (0.93 mg kg-1) and Cd (0.19 mg kg-1) indicated no risk to human health. This study expands knowledge regarding the elemental composition of A. angustifolia. Results indicate that these seeds have nutritional value, and their consumption can be a good strategy to improve overall human nutrition in this region of South America.

Modeling and prediction of sulfuric acid digestion analyses data from PXRF spectrometry in tropical soils

Sulfuric acid digestion analyses (SAD) provide useful information to environmental studies, in terms of the geochemical balance of nutrients, parent material uniformity, nutrient reserves for perennial crops, and mineralogical composition of the soil clay fraction. Yet, these analyses are costly, time consuming, and generate chemical waste. This work aimed at predicting SAD results from portable X-ray fluorescence (pXRF) spectrometry, which is proposed as a “green chemistry” alternative to the current SAD method. Soil samples developed from different parent materials were analyzed for soil texture and SAD, and scanned with pXRF. The SAD results were predicted from pXRF elemental analyses through simple linear regressions, stepwise multiple linear regressions, and random forest algorithm, with and without incorporation of soil texture data. The modeling was developed with 70 % of the data, while the remaining 30 % was used for validation through calculation of R2, adjusted R2, root mean square error, and mean error. Simple linear regression can accurately predict SAD results of Fe2O3 (R2 0.89), TiO2 (R2 0.96), and P2O5 (R2 0.89). Stepwise regressions provided accurate predictions for Al2O3 (R2 0.87) and Ki - molar weathering index (SiO2/Al2O3) (R2 0.74) by incorporating soil texture data, as well as for SiO2 (R2 0.61). Random forest also provided adequate predictions, especially for Fe2O3 (R2 0.95), and improved results of Kr - molar weathering index (SiO2/(Al2O3 + Fe2O3)) (R2 0.66), by incorporation of soil texture data. Our findings showed that the SAD results could be accurately predicted from pXRF data, decreasing costs, time and the production of laboratory waste.(AU)

Tracing the origin of reservoir sediments using magnetic properties in Southeastern Brazil / Traçando a origem de sedimentos de reservatórios usando propriedades magnéticas no Sudeste do Brasil

Determining the origin of eroded soil is essential to design effective soil erosion control strategies which preserve the soil resource, enhance agricultural productivity, and reduce the negative impacts of soil erosion, in-field and off-field. Magnetic properties have been widely used in temperate environments to identify sediment sources, pathways and links, but there have been very few applications in tropical and subtropical environments. Therefore, in this paper we investigated reservoir sediment sources in the Upper Grande River Basin, Southeastern Brazil, using sediment tracing techniques based on magnetic parameters (low and high frequency magnetic susceptibility, frequency dependent susceptibility). The different parent materials and subtropical weathering conditions resulted in soils having different Fe oxide minerals and Fe oxide contents, promoting magnetic variability that allowed comparison and identification of possible sources of reservoir sediments in order to reduce water erosion impacts. The results indicate the suitability of magnetic properties as a tracer for soil erosion studies in tropical environments.(AU)

Determinar a origem de solos erodidos é essencial para projetar estratégias efetivas de controle da erosão do solo que preservem os recursos do solo, aumentem a produtividade agrícola e reduzam os impactos negativos da erosão do solo, em campo e fora dele. As propriedades magnéticas têm sido amplamente utilizadas em ambientes temperados para identificar fontes, vias e elos de sedimentos, mas existem pouquíssimas aplicações em ambientes tropicais. Portanto, neste trabalho investigamos fontes de sedimentos de reservatórios na Bacia do Alto Rio Grande, Sudeste do Brasil, utilizando técnicas de rastreamento de sedimentos baseadas em parâmetros magnéticos (suscetibilidade magnética de baixa e alta freqüência, susceptibilidade dependente da freqüência). Os diferentes materiais de origem e condições de intemperismo tropical resultaram em solos com diferentes minerais de óxido de Fe e teores de óxidos de Fe, promovendo variabilidade magnética que permitiu a comparação e identificação de possíveis fontes de sedimentos de reservatórios para reduzir os impactos da erosão hídrica. Os resultados indicam a adequação das propriedades magnéticas como um traçador para estudos de erosão do solo em ambientes tropicais.(AU)

Tracing the origin of reservoir sediments using magnetic properties in Southeastern Brazil / Traçando a origem de sedimentos de reservatórios usando propriedades magnéticas no Sudeste do Brasil

Determining the origin of eroded soil is essential to design effective soil erosion control strategies which preserve the soil resource, enhance agricultural productivity, and reduce the negative impacts of soil erosion, in-field and off-field. Magnetic properties have been widely used in temperate environments to identify sediment sources, pathways and links, but there have been very few applications in tropical and subtropical environments. Therefore, in this paper we investigated reservoir sediment sources in the Upper Grande River Basin, Southeastern Brazil, using sediment tracing techniques based on magnetic parameters (low and high frequency magnetic susceptibility, frequency dependent susceptibility). The different parent materials and subtropical weathering conditions resulted in soils having different Fe oxide minerals and Fe oxide contents, promoting magnetic variability that allowed comparison and identification of possible sources of reservoir sediments in order to reduce water erosion impacts. The results indicate the suitability of magnetic properties as a tracer for soil erosion studies in tropical environments.

Determinar a origem de solos erodidos é essencial para projetar estratégias efetivas de controle da erosão do solo que preservem os recursos do solo, aumentem a produtividade agrícola e reduzam os impactos negativos da erosão do solo, em campo e fora dele. As propriedades magnéticas têm sido amplamente utilizadas em ambientes temperados para identificar fontes, vias e elos de sedimentos, mas existem pouquíssimas aplicações em ambientes tropicais. Portanto, neste trabalho investigamos fontes de sedimentos de reservatórios na Bacia do Alto Rio Grande, Sudeste do Brasil, utilizando técnicas de rastreamento de sedimentos baseadas em parâmetros magnéticos (suscetibilidade magnética de baixa e alta freqüência, susceptibilidade dependente da freqüência). Os diferentes materiais de origem e condições de intemperismo tropical resultaram em solos com diferentes minerais de óxido de Fe e teores de óxidos de Fe, promovendo variabilidade magnética que permitiu a comparação e identificação de possíveis fontes de sedimentos de reservatórios para reduzir os impactos da erosão hídrica. Os resultados indicam a adequação das propriedades magnéticas como um traçador para estudos de erosão do solo em ambientes tropicais.

Modeling and prediction of sulfuric acid digestion analyses data from PXRF spectrometry in tropical soils

Sulfuric acid digestion analyses (SAD) provide useful information to environmental studies, in terms of the geochemical balance of nutrients, parent material uniformity, nutrient reserves for perennial crops, and mineralogical composition of the soil clay fraction. Yet, these analyses are costly, time consuming, and generate chemical waste. This work aimed at predicting SAD results from portable X-ray fluorescence (pXRF) spectrometry, which is proposed as a “green chemistry” alternative to the current SAD method. Soil samples developed from different parent materials were analyzed for soil texture and SAD, and scanned with pXRF. The SAD results were predicted from pXRF elemental analyses through simple linear regressions, stepwise multiple linear regressions, and random forest algorithm, with and without incorporation of soil texture data. The modeling was developed with 70 % of the data, while the remaining 30 % was used for validation through calculation of R2, adjusted R2, root mean square error, and mean error. Simple linear regression can accurately predict SAD results of Fe2O3 (R2 0.89), TiO2 (R2 0.96), and P2O5 (R2 0.89). Stepwise regressions provided accurate predictions for Al2O3 (R2 0.87) and Ki - molar weathering index (SiO2/Al2O3) (R2 0.74) by incorporating soil texture data, as well as for SiO2 (R2 0.61). Random forest also provided adequate predictions, especially for Fe2O3 (R2 0.95), and improved results of Kr - molar weathering index (SiO2/(Al2O3 + Fe2O3)) (R2 0.66), by incorporation of soil texture data. Our findings showed that the SAD results could be accurately predicted from pXRF data, decreasing costs, time and the production of laboratory waste.

A hydropedological approach to a mountainous Clayey Humic Dystrudept in the Mantiqueira Range, southeastern Brazil

The Mantiqueira Range region is one of the most important headwaters in southeastern Brazil. In this context, the relationship between pedology and hydrology has been debated and analyzed in recent years, contributing to the creation of a multidisciplinary science call hydropedology. Therefore, the aim of this study was to evaluate the hydropedological properties of a mountainous Clayey Humic Dystrudept in the Mantiqueira Range region, in the state of Minas Gerais, Brazil, comparing two land-uses, native forest and pasture. The hydraulic conductivity results demonstrated that native forest (MFO) has a strong influence on this parameter, offering conditions for movement of water in the soil that are more adequate in this profile than in pasture. These results were supported by pore size distribution analyses which showed that soil from native forest has a greater amount of macropores than soil from pasture as well as greater connectivity between the macropores. In general, the MFO site had greater S index values than the micro-catchment taken from pasture, offering favorable physical conditions for the formation of preferential flowpaths in the soil profile and, therefore, better conditions for groundwater recharge. Soil erosion and water quality results confirmed the importance of native forest areas in the interaction between interception of the direct impact of intense precipitation on the soil surface, and hydropedological attributes, such as saturated hydraulic conductivity and porosity.

A hydropedological approach to a mountainous Clayey Humic Dystrudept in the Mantiqueira Range, southeastern Brazil

The Mantiqueira Range region is one of the most important headwaters in southeastern Brazil. In this context, the relationship between pedology and hydrology has been debated and analyzed in recent years, contributing to the creation of a multidisciplinary science call hydropedology. Therefore, the aim of this study was to evaluate the hydropedological properties of a mountainous Clayey Humic Dystrudept in the Mantiqueira Range region, in the state of Minas Gerais, Brazil, comparing two land-uses, native forest and pasture. The hydraulic conductivity results demonstrated that native forest (MFO) has a strong influence on this parameter, offering conditions for movement of water in the soil that are more adequate in this profile than in pasture. These results were supported by pore size distribution analyses which showed that soil from native forest has a greater amount of macropores than soil from pasture as well as greater connectivity between the macropores. In general, the MFO site had greater S index values than the micro-catchment taken from pasture, offering favorable physical conditions for the formation of preferential flowpaths in the soil profile and, therefore, better conditions for groundwater recharge. Soil erosion and water quality results confirmed the importance of native forest areas in the interaction between interception of the direct impact of intense precipitation on the soil surface, and hydropedological attributes, such as saturated hydraulic conductivity and porosity.(AU)

Tropical soils characterization at low cost and time using portable X-ray fluorescence spectrometer (pXRF): Effects of different sample preparation methods / Caracterização de solos tropicais a baixo custo e tempo usando espectrômetro portátil de fluorescência de raios-X (pXRF): Efeitos de diferentes métodos de preparo de amostras

ABSTRACT Portable X-ray fluorescence spectrometer (pXRF) has been recently adopted by the Soil Science community for uses in both field and laboratory, obtaining the total content of several chemical elements in a few seconds. Sulfuric acid digestion is an expensive and time-consuming laboratory analysis that provides contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5, important for soil studies. Due to few pXRF studies in tropical soils, this work aimed to compare contents of Fe2O3, Al2O3, SiO2, TiO2 and P2O5 obtained by pXRF with sulfuric acid digestion results, and to evaluate the effects of varying forms of preparing soil samples and scanning with pXRF on the resulting values in Brazilian soils. Soils were scanned in five conditions in-field (in situ) and in laboratory, evaluating varying sample preparation methods, particle sizes and soil moisture. Four pXRF scanning operational modes were tested. Linear regressions were adjusted between results of pXRF and sulfuric acid digestion. Equations were validated with an independent set of samples. Statistical analyses compared the methods of preparing the samples. Adequate linear models reached R2 of 0.99 and 0.89 for Fe2O3 and TiO2, respectively. Validation promoted R2 greater than 0.97 and RMSE and ME close to zero for both oxides. Statistical differences of pXRF results were found among the methods of preparing samples. pXRF spectrometer has great potential to obtain Fe2O3 and TiO2 content rapidly and economically with high correspondence with laboratory results of sulfuric acid digestion analysis. Varying methods of preparing the samples promote differences in the results of pXRF.

RESUMO O espectrômetro portátil de fluorescência de raios-X (pXRF) foi recentemente adotado pela Ciência do Solo, para uso em campo e laboratório, para obtenção do conteúdo total de vários elementos químicos em poucos segundos. A digestão com ácido sulfúrico é uma análise laboratorial cara e demorada que fornece teores de Fe2O3, Al2O3, SiO2, TiO2 e P2O5, importantes para estudos sobre solos. Devido aos poucos estudos sobre o pXRF em solos tropicais, este trabalho objetivou comparar os teores de Fe2O3, Al2O3, SiO2, TiO2 e P2O5 obtidos pelo pXRF com os resultados de digestão com ácido sulfúrico e avaliar os efeitos de diferentes formas de preparo de amostras de solo e leitura com o pXRF sobre seus resultados para solos brasileiros. Os solos foram submetidos a leituras com o pXRF em cinco condições, em campo (in situ) e em laboratório, avaliando variados métodos de preparo de amostras, tamanhos de partículas e umidade do solo. Quatro modos de operação do pXRF foram testados. Regressões lineares foram ajustadas entre os resultados do pXRF e digestão com ácido sulfúrico. As equações foram validadas com um conjunto independente de amostras. Análises estatísticas compararam os métodos de leitura de amostras. Modelos lineares adequados atingiram R2 de 0,99 e 0,89 para Fe2O3 e TiO2, respectivamente. A validação promoveu R2 maior que 0.97 e RMSE e ME próximos a zero para ambos os óxidos. Foram encontradas diferenças estatísticas dos resultados do pXRF entre os métodos de preparo de amostras. O pXRF possui um grande potencial para obter rápida e economicamente os teores de Fe2O3 e TiO2 com elevada correspondência com os resultados laboratoriais da análise da digestão com ácido sulfúrico. Métodos variáveis ​​de preparo das amostras promovem diferenças nos resultados de pXRF.

Zinc, copper and manganese availability in soils treated with alkaline sewage sludge from Paraná state (Brazil) / Disponibilidade de Zn, Cu e Mn em solos tratados com lodo de esgoto alcalinizado do estado do Paraná (Brasil)

ABSTRACT In Paraná, most of the sludge generated in sewage treatment plants is subjected to the prolonged alkaline stabilization process. Although it is known that the alkaline sewage sludge contains micronutrients such as Zn, Cu and Mn, little is known about the availability of these elements in soils treated with this type of sewage sludge. Thus, the objective of the study was to evaluate the influence of alkaline sewage sludge from Paraná on Zn, Cu and Mn availability in soils. Twenty sewage treatment plants were selected throughout Paraná, where alkaline sewage sludge and the most representative agricultural soil of the each region were collected. Each soil was incubated for 60 days with alkaline sewage sludge rates (0, 10, 20, 40, and 80 Mg ha-1) from their region. Subsequently, Zn, Cu and Mn availability was determined using the Mehlich-1 extractant. The alkaline sewage sludge increased Zn availability and decreased Mn availability in most soils. Cu showed intermediate results, with increased availability, primarily in medium texture soils and decrease in most of the clayey soils. In soils with pH close to ideal for the plant growth, the alkaline sewage sludge rate should be carefully calculated so that there is no excessive increase in the pH and Zn, Cu and Mn imbalance.

RESUMO No Paraná, a maioria do lodo de esgoto gerado em estações de tratamento é submetida ao processo de estabilização alcalina prolongada. Embora seja conhecido que o lodo de esgoto alcalinizado contém micronutrientes como Zn, Cu e Mn, pouco se conhece sobre a disponibilidade desses elementos em solos tratados com esse tipo de lodo de esgoto. Assim, o objetivo do estudo foi avaliar a influência de lodos de esgoto alcalinizados do estado do Paraná sobre a disponibilidade de Zn, Cu e Mn no solo. Foram selecionadas vinte estações de tratamento de esgoto ao longo do Paraná, onde foram coletadas amostras de lodo de esgoto alcalinizado e amostras do solo agrícola mais representativo da região. Cada solo foi incubado por 60 dias com doses de lodo de esgoto (0, 10, 20, 40, e 80 Mg ha-1) da sua região. Posteriormente, foi determinada a disponibilidade de Zn, Cu e Mn no solo usando o extrator Mehlich-1. A aplicação de lodo de esgoto alcalinizado ao solo aumentou a disponibilidade de Zn e diminuiu a disponibilidade de Mn na maioria dos solos. Já o Cu apresentou resultados intermediários, com aumento de disponibilidade basicamente em solos de textura média e com diminuição para a maioria dos solos muito argilosos. Em solos com pH próximo ao ideal para o cultivo agrícola, a dose de lodo de esgoto alcalinizado deve ser cuidadosamente calculada para que não ocorra o aumento excessivo do pH e desbalanço nos teores de Zn, Cu e Mn.

Urochloa decumbens growth and P uptake as affected by long-term phosphate fertilization, mycorrhizal inoculation and historical land use in contrasting Oxisols of the Brazilian Cerrado / Crescimento e absorção de P por Urochloa decumbens afetado por longos períodos de adubação fosfatada, inoculação micorrízica e histórico de uso em Latossolos contrastantes do Cerrado brasileiro

ABSTRACT In the fertility management of highly weathered-leached Brazilian Oxisols, P is the most limiting macronutrient. A greenhouse experiment was conducted with the objective to evaluate the influence of the interaction between P doses, mycorrhizal inoculation and historical land use on Urochloa decumbens growth and P uptake in four Oxisols with contrasting chemical, physical and mineralogical properties. The plants were cultivated in plastic pots containing 4 kg of soil in a completely randomized design, four replications and 2x2x2 factorial scheme: with two P doses; with and without mycorrhizal inoculation; soils cultivated for long periods and non-cultivated (under native vegetation). There were two plantings of ten weeks each. Shoot dry mater, concentration and accumulation of P in the shoot were evaluated. In the first planting, the Urochloa response was greater in non-cultivated soils associated with inoculation and P addition. However, in the second planting, the inoculation had a greater effect in all soils compared to the first planting associated with the lowest P dose. As the P concentration in the soil increased, P in the shoot dry matter increases. The inoculation did not affect the P concentration and accumulation in the shoot of Urochloa. The growth of Urochloa decumbens was strongly influenced by the interaction among soil class x history of land use x dose of P x inoculation.

RESUMO No manejo da fertilidade de Latossolos brasileiros altamente intemperizados e lixiviados, o P é o macronutriente mais limitante. Assim, conduziu-se um experimento em casa de vegetação, objetivando-se avaliar a influência da interação entre doses de P, inoculação micorrízica e histórico de uso do solo no crescimento de Urochloa decumbens e absorção de P, em quatro Latossolos com atributos químicos, físicos e mineralógicos contrastantes. As plantas foram cultivadas em vasos contendo 4 kg de solo, dispostos em um delineamento inteiramente casualizado, com quatro repetições e esquema fatorial 2x2x2: duas doses de P; com e sem inoculação micorrízica; solos cultivados por longos períodos e não cultivados (sob vegetação nativa). Realizaram-se dois cultivos com duração de 10 semanas cada. Após cada cultivo avaliaram-se a matéria seca da parte aérea, teor e acúmulo de P na parte aérea. No primeiro cultivo, maior resposta ao P aconteceu nos solos sob vegetação nativa em associação à inoculação e adição de P. No segundo cultivo, a inoculação teve maior efeito em todos os solos, associada à menor dose de P. O aumento do P no solo aumenta a concentração desse nutriente na parte aérea. A inoculação não teve efeito na concentração e no acúmulo de P na parte aérea de Urochloa. O crescimento de Urochloa decumbens foi fortemente influenciado pela interação entre classe de solo x histórico de uso da terra x dose de P x inoculação.

Alkalinized sewage sludge application improves fertility of acid soils / Aplicação de lodo de esgoto alcalinizado melhora a fertilidade de solos ácidos

ABSTRACT Although it is known that alkalinized sewage sludge raises the pH of acid soils, there is limited knowledge regarding its effects on other soil fertility indicators, such as P and K availability and soil organic C content. Thus, the goal of this study was to evaluate how the application of alkalinized sewage sludge affects the fertility of acid soil. Twenty sewage treatment plants were selected throughout Paraná State (Brazil), and samples of alkalinized sewage sludge and samples of the most representative agricultural soil of the region were collected (covering soils with medium, clayey or very clayey texture). Each soil was incubated for 60 days with doses of sewage sludge (0, 10, 20, 40, and 80 Mg ha-1) from its region and equivalent doses of limestone. The alkalinized sewage sludge was superior to limestone in the correction of soil acidity (pH, Al3+, and H + Al3+) and P and Ca2+ availability. The sludge also increased Mg2+ availability in all soils, K+ in seven soils and organic C in three soils. The very clayey soils (higher buffering capacity) supported higher sludge doses than did clayey and medium texture soils. The alkalinized sewage sludge application in acid soils proved to be an interesting alternative to recycling this type of waste, because it improved soil fertility and could reduce costs associated with soil management and crop fertilization.

RESUMO Embora seja conhecido a capacidade do lodo de esgoto alcalinizado em elevar o pH de solos ácidos, tem-se um limitado conhecimento sobre o efeito em outros indicadores da fertilidade do solo, como disponibilidade de P e K e, teor de C orgânico no solo. Assim, o objetivo do estudo foi avaliar como a aplicação de lodo de esgoto alcalinizado afeta a fertilidade de solos ácidos. Foram selecionadas vinte estações de tratamento de esgoto ao longo do Paraná (Brasil), onde foram coletadas amostras de lodo de esgoto alcalinizado e amostras do solo agrícola mais representativo da região (abrangendo solos com textura média, argilosa ou muito argilosa). Cada solo foi incubado por 60 dias com doses de lodo de esgoto (0, 10, 20, 40, e 80 Mg ha-1) da sua região e com doses equivalentes de calcário. O lodo de esgoto alcalinizado foi superior ao calcário na correção da acidez do solo (pH, Al3+ e H+Al3+) e na elevação da disponibilidade P e Ca2+. O lodo também aumentou a disponibilidade de Mg2+ em todos os solos, K+ em sete solos e C orgânico em três solos. Os solos muito argilosos (alta poder tampão) suportam maior dose de lodo em comparação aos solos de textura argilosa e média. A aplicação de lodo de esgoto alcalinizado em solos ácidos demonstrou ser uma interessante alternativa para reciclar esse tipo de resíduo, pois melhorou a fertilidade dos solos e pode vir a reduzir custos com manejo do solo e adubação das culturas.

Lodos de esgoto alcalinizados em solos do estado do Paraná: taxa de aplicação máxima anual e comparação entre métodos para recomendação agrícola / Alkaline sewage sludge on soils of Paraná state: maximum annual application rate and comparison between methods for agricultural recommendation

Para o uso agrícola do lodo de esgoto higienizado por processo de estabilização alcalina prolongada (lodo EAP), além de estabelecer limites de aplicação máxima conforme a legislação, é necessário estudar atributos dos lodos e dos solos que favoreçam as metodologias de sua recomendação. Objetivou-se determinar a taxa de aplicação máxima anual (TAMA) de lodo EAP pelo critério de elevação do pH para 20 lodos e solos do estado do Paraná; determinar a influência dos atributos desses solos nos valores da TAMA de lodo EAP; avaliar o uso dos métodos de saturação por bases (V%) e pH referência (SMP), utilizando como padrão o método da incubação. Empregou-se o ensaio de incubação para lodo EAP aplicado ao solo, conforme metodologia oficial. Os resultados indicam que as TAMA de lodo EAP variaram de 10 a >80 Mg.ha-1 para as 20 regionais estudadas; Os atributos químicos (capacidade de troca de cátions, H+Al e carbono) e físico (argila) são os que melhor definem a determinação da TAMA, apresentando relação diretamente proporcional. Os métodos do V% e do pH referência (SMP) para pH H2O 5,5 mostraram-se seguros quanto à recomendação agrícola.

For agricultural use of alkalinized sludge (AS), beyond to establish the maximum application limits to comply with the legislation, it is necessary to study the attributes of sludges and soils that favor the methodologies of its recommendation. The objectives of this study were to determine the maximum annual application rate (MAAR) of alkalinized sludge (AS) according to the pH elevation criterion for 20 sludge origins and soils of the Paraná state; to determine the influence of soil attributes over the MAAR of AS; to evaluate two methods rate calculation for AS, the base saturation (V%) and pH reference (SMP) by comparing with the standard incubation methodology for AS sludge application. It was used incubation test for AS applied to soil, following official methodology. The results indicated that the MAAR were ranged 10 to >80 Mg.ha-1, for the 20 regions; the chemical properties (cation exchange capacity, H+Al and carbon) and physical properties (clay) were the best parameters to the determination of the MAAR, showing direct relationship; the V% and SMP (pH H2O 5,5) methods were safe to the agricultural recommendation.