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The aim of the present study is to assess soil Cd and Pb contamination in kale (Brassica oleracea var. acephala) production sites in mountain agroecosystem, as well as its potential risk to human health. The study was carried out within 24 kale-production sites located in mountainous region of Rio de Janeiro (Brazil). Soil, plant, and fertilizer samples were collected in all assessed properties. Pseudo-total and bioavailable soil Cd and Pb content and their concentration and amount accumulated in plants were analyzed. The recorded results were used to calculate the pollution index. Risks to human health associated with kale consumption were assessed by comparing the limits set by the Brazilian regulating agency and by calculating estimated daily intake (EDI), noncarcinogenic target hazard quotient (THQ), and carcinogenic risk factor (CRF). Soil Cd and Pb enrichment was observed. Inappropriate management adopted in the assessed sites and terrain slope and the intensive use of mineral (phosphate and potassium) and organic (poultry litter) fertilizers were the main factors contributing to increase soil Cd and Pb pseudo-total and bioavailability contents. Most Cd and Pb contents in leaves, in natura, exceed the maximum values set by the Brazilian regulating agency. The present EDI, THQ, and CRF results recorded for these metals were within the tolerable ranges.

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Clubroot disease, caused by Plasmodiophora brassicae, limits the production of Brassica spp. worldwide. Little is known about the factors related to the development of the disease in kale (Brassica oleracea var. acephala) plants and in crops in mountainous areas under tropical conditions. This study examined the severity of clubroot in kale crops as well as identify potential flaws in management and the soil and relief factors related to its occurrence. The study was conducted in 24 kale fields in the mountainous region of Rio de Janeiro (Brazil). Soil and kale growth management practices adopted in the region were identified and samples of soil and plants were collected. Subsequently, soil and relief attributes, disease severity, biomass and nutrient and Al contents and accumulation in the plants were determined. There was a high spread of the pathogen in the areas. Inappropriate and recurrent practices in the region were detected, e.g., sequential cultivation of host species, low adoption of soil fertility analysis and liming and conservation practices, and community use of agricultural machinery and implements without prior cleaning. The disease was associated with more acidic soils, subject to greater water accumulation and with high levels of Al³+ as well as with higher Al contents and accumulation in the roots. Management practices must be adopted in the region to reduce the potential inoculum of P. brassicae and to increase soil fertility.

A hérnia das crucíferas, causada por Plasmodiophora brassicae, é limitante à produção de Brassica spp. em todo o mundo. Pouco se conhece sobre os fatores relacionados ao desenvolvimento da doença em plantas de couve-comum (Brassica oleracea var. acephala) e em cultivos em áreas de montanha sob condições tropicais. Objetivou-se avaliar a severidade da hérnia das crucíferas em lavouras de couve-comum, identificar potenciais falhas no manejo e os fatores de solo e relevo relacionados a sua ocorrência. O estudo foi conduzido em 24 lavouras de couve-comum da Região Serrana do Rio de Janeiro (Brasil). Registraram-se as práticas de manejo do solo e da couve-comum adotadas na região e coletaram-se amostras de solo e plantas. Em seguida, determinaram-se os atributos do solo e do relevo, a severidade da doença, biomassa e os teores e acúmulo de nutrientes e Al nas plantas. Observou-se alta disseminação do patógeno nas áreas. Foram identificadas práticas inadequadas e recorrentes na região como o cultivo sequencial de espécies hospedeiras, baixa adoção a análise de fertilidade, calagem e de medidas de conservação do solo, e o uso comunitário de máquinas e implementos agrícolas sem limpeza prévia. Identificou-se associação da doença com solos mais ácidos, sujeitos a maior acúmulo de água e com elevados teores de Al³+; e a maior teor e acúmulo de Al nas raízes. Práticas de manejo devem ser adotadas na região visando a redução do potencial de inóculo de P. brassicae e o aumento da fertilidade do solo.

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Studies to assess variability factors of heavy metals in soils are essential to understand their behavior in the environment and for the assessment of contaminated areas. In this context, this research aimed to study the factors that influence the variability of heavy metal levels and their bioavailability in pasture areas in the Alturas de Nazareno region, Mayabeque, Cuba, as well as the transfer to plants. Forty-five points were distributed in a natural pasture and at two depths (0-20 and 20-40 cm) as a function of relief and soil type. Pseudo-total heavy metal contents were determined according to method 3051A of USEPA, geochemical fractionation according to the Community Bureau of Reference method, and plant digestion according to method 3052 of USEPA. Soil samples were separated into two groups, according to cluster analysis. The type of soil associated with the pH and Ca attributes were the factors that most influenced the variability of the total and bioavailable levels of metals in natural pasture soils in the region of Alturas de Nazareno. Group 1 showed the lowest heavy metal contents and the highest pH and calcium values, which were predominantly associated with carbonate soils. Group 2 had the highest contents of heavy metals and Fe, corresponding mainly to the soil Ferralítico Rojo. The concentration of metals in plants was directly related to their bioavailable content in the soil, where G2 represents the group with the highest risk of transferring metals to the food chain.

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The objectives of this study was to diagnose Cd and Pb contamination in soil and to identify the main factors that contribute to the transfer of these elements to tomato plants and fruits and contamination levels of the fruits in tropical mountain conditions. Contamination of the study area soils by Cd and Pb was verified. This contamination stemmed from the intensive use of agricultural inputs, mainly organic fertilizers and soluble mineral fertilizers. The relief of the terrain and inadequate soil management influenced the spatial distribution of these two metals. The Cd concentration in tomato fruits was very low, but the Pb contamination detected in approximately 80% of the fruit samples was considerably higher than the limits that pose a danger to human health. The translocation of Pb to the tomato fruits was associated with the use of organic fertilizer, mainly poultry litter.

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Two greenhouse experiments were carried out to evaluate the phytoremediation potential, physiological responses and zinc (Zn) uptake kinetics of water lettuce (Pistia stratiotes L.). The phytoextraction experiment evaluated four doses of Zn (0.7 mg L-1 - represented the Zn in the nutrient solution, 1.8, 18 and 180 mg L-1 - corresponded to ten, hundred and a thousand times, respectively, the maximum permitted content for fresh water) at four different culture times (24, 48, 72 and 168 h). The Zn uptake kinetics of water lettuce were evaluated at two concentrations of Zn (1.8 and 18 mg L-1). The water lettuce attained the highest percentage removal at the lowest evaluated doses (0.7 and 1.8 mg L-1), reaching a maximum value of approximately 72% removal (when cultivated in 1.8 mg L-1 of Zn after 168 h of culture). The Zn uptake increased with culture time, increasing the synthesis of carotenoids at all doses evaluated. The highest doses of Zn resulted in a reduction in photosynthetic efficiency. The results showed a high potential of water lettuce to absorb and tolerate Zn, accumulating preferably in the roots, demonstrating that these plants are able to absorb large quantities of Zn in contaminated solution.

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The increasing concern regarding the preservation of soil quality suggests the adoption of quality reference values as a first step in environmental monitoring actions. In this context, the objective of this study was to establish soil quality reference values for Al, Zn, Mn, Cd, Fe, Pb, Ni, Cr, and Cu and to correlate several soil properties with the occurrence of these elements in the hillslope region of Rio de Janeiro State. Sixty-two samples were collected at depths of 0-20 and 20-40 cm and analyzed using the USEPA method 3051A. After clustering analysis, the samples were separated into three groups. Classification functions were obtained based on the variables pH - Mg - Fe - Mn, i.e., the variables that were best related to heavy metal content. We determined to establish the quality reference values for the 75th percentile of the three groups. The relief forms of the area, which facilitate the transport of soil fine-particle fractions and accumulation in lowlands, were revealed to be one of most important factors in understanding the distribution of soil heavy metals.

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The petroleum industry generates a range of wastes which is often are disposed in soil close to the well location, negatively affecting soil and water quality. The objective of this study was to evaluate the solubility and map the spatial variability of barium in a potentially contaminated area. The study area consisted of a petroleum well-drilling waste disposal site located in the municipality of Mato Rico-PR. A large georeferenced sampling grid was organized. Soil samples were collected at depths of 30, 60, 90, and 120 cm for determination of the "pseudo-total" concentrations and geochemical fractionation of barium. The barium concentrations showed spatial dependence, which permitted the use of geostatistical interpolators. Regarding depth, the depth of 0-30 cm showed the largest contaminated area; however, higher concentrations of barium were found at the depth of 60-90 cm. The results of geochemical fractionation showed that the analyzed samples contained percentages higher than 99% in the non-labile fraction (residual). These results indicate clearly that the barium was in a condition of low solubility, even for samples that had the highest concentrations, presenting low-environmental risk.

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Determination of the natural background levels of trace elements in organosols and the proposal of quality reference values (QRVs) for these elements are essential for monitoring these soils because they are fragile and subject to change more intensely and rapidly than other soil classes. Given the above information, the objectives of this study were to determine the QRVs of trace elements for organosols and to correlate some soil properties with the occurrence of these elements. Forty organic soil horizon samples from different regions of Brazil were selected to determine the pseudo-total content of trace elements. The samples were separated into three groups according to a cluster analysis. The soil variable Fe and C contents had the strongest influence on the trace element contents in the organosols and were therefore used in the group classification functions. QRVs were proposed according to the 75th percentiles of the groups. The classification functions are a suitable tool for the allocation of new samples into previously established groups and may potentially be used to estimate the degree of organosol degradation.

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