ABSTRACT Atrazine is a herbicide widely used in agriculture; however, because of its toxicity, alternatives are needed to remove this compound from the environment. In this study, we investigated the adsorption process and the atrazine-adsorbing ability of three biochars produced at different pyrolysis temperatures from byproducts of the wood industry. The biochars were characterized by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and their physical characteristics were evaluated by Brunauer-Emmett-Teller (BET) analysis. The biochar pyrolyzed at 350 °C (BM350) adsorbed 26.04% of the herbicide, showing the best performance among the three biochars tested, even though it had the lowest specific surface area (1.467 m2 g–1). It also had a greater quantity of organic functional groups, which may have influenced the adsorption. The kinetics of the adsorption process were best explained by the pseudo-first-order model and by the Freundlich isotherm model. However, the biochar is not suitable for the removal of the herbicide atrazine, having a lower adsorption capacity than those of others described in the literature.

ABSTRACT The contamination of aquatic environments with chemical trace elements can be evaluated by their accumulation in sediments of the water body. Studies on mercury require the use of exclusive extraction techniques that have relatively high costs when compared to the analysis of other trace elements. This study was conducted aiming at determining the mercury concentration in sediments of the Upper Parnaíba River basin, located in a region of agricultural expansion between the states of Piauí and Maranhão. The sediment was collected at 12 sites in the basin. After drying, the quantification of total mercury was performed by the Zeeman atomic absorption spectrometry coupled to a pyrolysis reactor. Mercury concentrations in sediments of the Parnaíba River ranged from 4.2 to 58.5 ng g−1 and presented a low probability of adverse effects on biota. Mercury had no correlation with the variables clay, silt, sand, total organic carbon, iron, and aluminum, demonstrating its possible anthropogenic origin. Although mercury concentrations have a low probability to disturb the balance of the local ecosystem, there is a need for monitoring the region in order to quantify the risks to biota and human health.

ABSTRACT: The use of animal-origin residues as a nutrient source without prior and proper investigations on their positive and negative impacts can affect the quality of agricultural soils and the environment into which they are inserted. In this sense, the aim of this study was to assess the impact of swine wastewater and mineral fertilization application on soil, soybean crop, and leachate characteristics. The experiment was developed in drainage lysimeters under field conditions. The following doses of swine wastewater were applied: 0, 100, 200, and 300 m3 ha−1, both with and without mineral fertilization. Swine wastewater application contributed to increasing soil nutrients; however, a special attention should be paid to Cu+ and Zn+ accumulation, which may interfere with soil quality in the long-term. In addition, Na+, K+, and N can be leached into groundwater and cause impacts on water quality. Wastewater supplied soybean crop requirements with some nutrients such as K+ and Zn2+, without the need for an additional mineral supplementation. Thus, once the above conditions are monitored, swine wastewater can be applied to soil.

ABSTRACT: Soil application of swine wastewater for nutrient cycling may represent a correct destination of these residues and reduction in production costs. However, when applied to soil, such residue may cause environmental impacts. This study aimed to analyze the chemical characteristics of the soil, corn, and leachate after successive swine wastewater applications associated with mineral fertilization. The experiment was developed in drainage lysimeters under field conditions. Wastewater doses applied were 0, 100, 200, and 300 m3 ha−1 with and without mineral fertilization. The results were submitted to analysis of variance and Tukey's test. After nine years of application, a special attention should be taken regarding water quality from a dose of 200 m3 ha−1 since some elements may leach into the soil. In addition, a synchronism between residue application and crop requirements needs to be taken into account. Doses of 200 and 300 m3 ha−1 are considered as satisfactory to meet corn nutritional requirements. Moreover, an increase in fertility characteristics was observed, but a caution regarding Cu and Zn contents should be taken since these elements produce a cumulative effect in the soil.

ABSTRACT Hog raising generates a large amount of residues that is commonly discarded into the soil as fertilizer even with environmental risks. In this context, the aim of this study was to assess the application effects of different doses of swine wastewater (SW) associated with mineral fertilization on the abundance and diversity of organisms of soil meso- and macrofauna in two soybean crops. Treatments consisted of four doses (0, 100, 200, and 300 m3 ha−1) of SW with or without mineral fertilization in two soybean crop, totaling 24 experimental units. Soil meso- and macrofauna were sampled using pitfall traps installed at each plot. Samples were sorted and the organisms were separated and identified. The highest abundances were found between groups of springtails and spider mites. Soil meso- and macrofauna differed between soybean crops influenced by soil physical and chemical parameters. Doses of swine wastewater between 0 and 300 m3 ha−1 and mineral fertilization do not have effects on ecological indices of soil meso- and macrofauna. However, periodic applications over time change soil physicochemical variables, which may lead to negative effects in the long term.

Os resíduos gerados em suinoculturas possuem alto potencial poluidor, porém, devido à grande carga orgânica, apresenta-se como boa opção na fertilização de solos agrícolas. O objetivo deste trabalho foi estudar os efeitos ambientais decorrentes do uso de águas residuais de suinocultura em diferentes solos usando como bioindicador minhocas da espécie Eisenia andrei, por meio dos parâmetros de letalidade, fuga e reprodução. Estudou-se a aplicação de água residual de esterqueira e biodigestor em quatro doses (0, 100, 200 e 300 m³ ha-1) em três solos: Latossolo Vermelho distroférrico típico, Nitossolo Vermelho eutroférrico e Solo Artificial Tropical. Os resíduos estudados não provocaram qualquer letalidade nem fuga. Nos testes de reprodução, na maioria dos experimentos as parcelas com tratamentos obtiveram valores médios de juvenis eclodidos acima das parcelas controlo. A aplicação de água residual de esterqueira e biodigestor até a dose de 300 m³ ha-1 não afeta negativamente as populações de minhocas nos três solos analisados.

The waste generated by pig farmings has high toxic potential, however, its high organic load, makes them a good product for fertilization of agricultural soils. The aim of this work was to study the environmental effects arising from the use of swine wastewater using as bioindicators earthworms of the species Eisenia andrei through the parameters of lethality, avoidance and reproduction. We studied the application of biodigester wastewater and manure storage tanks wastewater in four doses (0, 100, 200 and 300 m³ ha-1) in three different soils (Oxisol, Kandiudox and Artificial Tropical Soil). The studied wastes did not cause any lethality or escape. The reproduction test showed, in most of the experiments that the plots with treated soil had an average number of hatched juveniles above those of control plots. The application of biodigester wastewater and manure storage tanks wastewater up to the dose of 300 m³ ha-1 does not negatively affect earthworm populations in the three soils analyzed.

RESUMO Em longo prazo a água residuária da suinocultura pode oferecer benefícios à relação solo-planta, quando planejado o uso e monitorados possíveis impactos ambientais. O objetivo do trabalho foi investigar os efeitos da aplicação continuada de água residuária de suinocultura associada com adubação mineral após seis anos de manejo em plantio direto e sucessão de culturas (14 ciclos de produção) acerca das condições químicas do solo e da cultura do milho. As doses de água residuária foram 0, 100, 200, 300 m3 ha-1 durante o ciclo. Simultaneamente foram avaliados os efeitos da associação de adubação mineral na semeadura com água residuária de suinocultura. A água residuária da suinocultura na dose de 100 m3 ha-1 proporcionou disponibilidade e absorção de P, K+, Mg2+ e Zn2+ sem causar toxicidade às plantas ou danos ao solo constituindo viabilidade de reúso de água e fertilização alternativa de baixo custo ao produtor. Os nutrientes N, P, K+ e B devem ser complementados com adubação mineral. Atenção especial deve ser direcionada ao acúmulo de Zn2+ no solo, ao longo do tempo de aplicação de água residuária da suinocultura.

ABSTRACT In the long run, swine wastewater can provide benefits to the soil-plant relationship, when its use is planned and the potential environmental impacts are monitored. The objective of this study was to investigate the effects of continuous application of swine wastewater, associated with mineral fertilization, after six years of management in no-tillage and crop rotation (14 production cycles), on the chemical conditions of the soil and the corn crop. The doses of wastewater were 0, 100, 200, 300 m3 ha-1 during the cycle. The effects of the association between mineral fertilization at sowing and swine wastewater were evaluated simultaneously. Swine wastewater at the dose of 100 m3 ha-1 promoted availability and absorption of P, K+, Mg2+ and Zn2+ without causing toxicity to plants or damage to the soil, constituting a viable, low-cost alternative of water reuse and fertilization for farmers. The nutrients N, P, K+ and B must be complemented with mineral fertilization. Special attention should be directed to the accumulation of Zn2+ in the soil along the time of swine wastewater application.

RESUMO A disposição de água residuária da suinocultura é uma prática que se pode tornar viável à agricultura, por minimizar custos com fertilização e melhorar as condições do solo. Para tanto, é fundamental o estabelecimento de critérios que definam doses de aplicação adequadas do ponto de vista agronômico e ambiental. O objetivo do presente trabalho foi avaliar o efeito de doses de água residuária de suinocultura associada à adubação mineral no estado nutricional da planta e na qualidade fisiológica da semente da soja. O experimento, conduzido no ano agrícola 2010/2011, foi realizado em 24 lisímetros de drenagem, em delineamento em blocos casualizados em esquema fatorial 4 x 2, sendo quatro doses de água residuária da suinocultura, 0, 100, 200 e 300 m3 ha-1 aplicadas antes da semeadura, combinadas com a presença e ausência de adubação mineral em três repetições. Folhas em estádio de florescimento foram coletadas para a determinação de N, P, K+, Ca+2, Mg+2, Cu+2, Zn+2, Mn e Fe. Sintomas de toxicidade e deficiências nutricionais na cultura foram detectados. Além disto, o aumento da dose de água residuária da suinocultura propiciou menor qualidade fisiológica nas sementes de soja.

ABSTRACT Swine wastewater application is a practice that can become viable in agriculture, for minimizing fertilization costs and improving soil conditions. Therefore, it is essential to establish criteria that define appropriate application doses from the agronomic and environmental perspectives. The objective of this study was to evaluate the effects of swine wastewater doses associated with mineral fertilization on soybean nutritional status and physiological quality of seed. The experiment was conducted in the agricultural year of 2010/2011, using twenty-four drainage lysimeters in randomized block design in 4 x 2 factorial scheme, with four swine wastewater doses (0, 100, 200 and 300 m3 ha-1) applied before sowing, associated with presence and absence of mineral fertilization, in three replicates. Leaves at the flowering stage were collected for determinations of N, P, K+, Ca+2, Mg+2, Cu+2, Zn+2, Mn and Fe. Symptoms of toxicity and nutritional deficiency were observed in the crop. Furthermore, higher doses of swine wastewater caused lower physiological quality in soybean seeds.