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Recebido em 7/7/97; aceito em 19/11/98 STUDY OF ADSORPTION/DESORPTION OF HERBICIDE 2,4D IN SOIL. The herbicides are being used in huge quantities for various porpouses. Once the herbicide finds its way into the environment, a major part of it comes in contact with soil. Humic substances are major organic constituents of soil. These substances may interact with herbicides in different modes and adsorption is probably the most important one. Adsorption will control the quantity of herbicide in the soil solution, and determines its persistence, leaching, mobility and bioavailability. In this work we studied the interaction between the herbicide 2,4D and soil in the presence and absence of organic matter. The methodology utilized for the determination of 2,4D was gas chromatography with eletron capture detector. The behavior of 2,4D was evaluated through Freundlich isotherms. It was verified that the herbicide 2,4D has a large adsorption in the humic acid.Keywords: humic substances; herbicide; 2,4D; adsorption; dessorption. ARTIGO INTRODUÇÃOOs objetivos primários de aumentar a colheita e melhorar a qualidade dos alimentos foram atingidos nos últimos anos, mas o uso indiscriminado sem os devidos critérios e sem conhecimento da ação e dos efeitos secundários por parte dos pesticidas pode acarretar danos ao meio ambiente e, conseqüentemente, a qualidade de vida do homem ficou comprometida.Há vários fatores que contribuem direta e indiretamente para a redução da colheita agrícola. As ervas daninhas têm uma contribuição expressiva causando efeitos negativos na produção, uma vez que competem com a cultura por espaço, água, luz e principalmente nutrientes e muitas vezes são hospedeiras de pragas (insetos).O solo é considerado como sendo um dos reservatórios finais dos herbicidas. Ao mesmo tempo ele é também fonte da qual os resíduos podem ser liberados para a atmosfera, lençol freático e organismos vivos.O comportamento dos herbicidas no solo é bastante complexo e é resultante de vários fatores, sendo um deles a interação com os constituintes das diferentes frações contidas no solo (áci-do húmico, ácido fúlvico, humina, argila, óxidos e etc.).A adsorção é a interação do soluto (herbicida) da fase lí-quida com a superfície das partículas da fase sólida do solo. É um processo determinante para se entender o comportamento dos herbicidas, pois está relacionado diretamente aos processos de transporte, adsorção e bioatividade deste no solo, influenciando diretamente na disponibilidade dos produtos para as plantas e na ação seletiva dos herbicidas pela interferência no seu deslocamento. HERBICIDA ESTUDADONeste estudo utilizou-se o herbicida ácido 2,4 diclorofenoxiacético (2,4D) grau técnico com 99% de pureza, procedente da Poly Science. O herbicida 2,4D é um ácido orgânico, com pKa 2,6, e possui uma solubilidade de 45 g/L em água. Este herbicida é cancerígeno acarretando danos ao fígado e ao coração. Ataca o sistema nervoso central, provocando convulsões. Sua dose letal (DL 50 ) oral é de 370 mg/kg (em coelhos) e por via derme é ...

Recebido em 14/6/12; aceito em 20/11/12; publicado na web em 6/3/13 THE ORGANIC WASTE STABILIZATION PROCESS: COMPOSTING VERSUS VERMICOMPOSTING. Two processes are used to stabilize organic wastes: composting and vermicomposting.There are no studies in the literature showing which process is most effective over the short term. In this study, 3 organic wastes were composted and vermicomposted for 90 days, and the parameters pH, effective cation exchange capacity, total organic carbon, total Kjeldahl nitrogen, P total , E 4 /E 6 ratio, hydrophobicity and aromaticity indexes were determined. In all experiments, vermicomposted materials showed higher stability, proving a superior tool for stabilization of these organic wastes.

The fungi Aspergillus sydowii Ce15, Aspergillus sydowii Ce19, Aspergillus sydowii Gc12, Bionectria sp. Ce5, Penicillium miczynskii Gc5, Penicillium raistrickii Ce16 and Trichoderma sp. Gc1, isolated from marine sponges Geodia corticostylifera and Chelonaplysylla erecta, were evaluated for their ability to grow in the presence of DDD pesticide. Increasing concentrations of DDD pesticide, i.e., 5.0 mg (1.56 × 10⁻¹² mmol), 10.0 mg (3.12 × 10⁻²) mmol) and 15.0 mg (4.68 × 10⁻² mmol) in solid and liquid culture media were tested. The fungi Trichoderma sp. Gc1 and Penicillium miczynskii Gc5 were able to grow in the presence of up to 15.0 mg of DDD, suggesting their potential for biodegradation. A 100% degradation of DDD was attained in liquid culture medium when Trichoderma sp. Gc1 was previously cultivated for 5 days and supplemented with 5.0 mg of DDD in the presence of hydrogen peroxide. However, the quantitative analysis showed that DDD was accumulated on mycelium and biodegradation level reached a maximum value of 58% after 14 days.

The biotransformation reactions of α-bromoacetophenone (1), p-bromo-α-bromoacetophenone (2), and p-nitro-α-bromoacetophenone (3) by whole cells of the marine fungus Aspergillus sydowii Ce19 have been investigated. Fungal cells that had been grown in artificial sea water medium containing a high concentration of chloride ions (1.20 M) catalysed the biotransformation of 1 to 2-bromo-1-phenylethanol 4 (56%), together with the α-chlorohydrin 7 (9%), 1-phenylethan-1,2-diol 9 (26%), acetophenone 10 (4%) and phenylethanol 11 (5%) identified by GC-MS analysis. In addition, it was observed that the enzymatic reaction was accompanied by the spontaneous debromination of 1 to yield α-chloroacetophenone 5 (9%) and α-hydroxyacetophenone 6 (18%) identified by GC-FID analysis. When 2 and 3 were employed as substrates, various biotransformation products were detected but the formation of halohydrins was not observed. It is concluded that marine fungus A. sydowii Ce19 presents potential for the biotransformations of bromoacetophenone derivatives.

Intraspecific genetic variation might limit the relevance of environmental factors on plant traits. For example, the interaction between genetics and (a-)biotic factors regulating pollen production are still poorly understood. In this study, we investigated pollen production of 28 birch (Betula pendula Roth) individuals in the years 2019–2021. We sampled catkins of eleven groups of genetically identical trees, which were partially topped, but of the same age and located in a seed plantation in southern Germany characterized by similar microclimatic conditions. Furthermore, we monitored environmental factors such as air temperature, characterized air quality (NO2, NOx and O3), and assessed potential solar radiation. We especially checked for differences between years as well as between and within clones and assessed the synchronicity of years with high/low pollen production. We present a robust mean for the pollen production of Betula pendula (1.66 million pollen grains per catkin). Our findings show temporal (H(2) = 46.29, p < 0.001) and clonal variations (H(4) = 21.44, p < 0.001) in pollen production. We conclude that synchronized high or low pollen production is not utterly site-specific and, in addition, not strictly dependent on genotypes. We suggest that appropriate clone selection based on application (seed plantation, urban planting) might be advantageous and encourage a long-term monitoring.

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agriculture for the control of a variety of weeds. These herbicides are quite mobile in soil and there is a concern that they may contaminate the environment, specially surface and ground water and soils. The results suggest that alachlor and atrazine present similar behavior in the environment, but alaclhor dissipates with greater rate.