Bianchini I, Silva R H, Cunha-Santino M B, Panhota R S
Departamento de Hidrobiologia, Universidade Federal de São Carlos - UFSCar, São Carlos, SP, Brazil.
Braz J Biol. 2010 Aug;70(3):559-68. doi: 10.1590/s1519-69842010000300012.
The present study discussed the kinetic aspects of leachate decomposition from an aquatic macrophyte, Pistia stratiotes L (water lettuce). This species was collected from Barra Bonita Reservoir located in the State of São Paulo (Brazil). Decomposition chambers were prepared with high molecular weight (HMW), low molecular weight (LMW) and integral (INT = HMW + LMW) dissolved organic matter (DOM) diluted with reservoir water. The samples were incubated at 20 degrees C, in darkness and under aerobic or anaerobic conditions. For 79 days, the concentrations of dissolved oxygen (DO) and organic carbon (OC) were measured. For calculating the deoxygenation coefficients (k d) and maximum oxygen consumption (COmax) the concentration of DO was integrated and fitted to a first-order kinetics model, which also applied to the depletion of OC concentrations. The COmax of INT incubations were 4% higher than the sum of HMW and LMW fractions. The deoxygenation coefficients, k d, had the same order of magnitude for all treatments. In relation to carbon decay, regardless of the availability of oxygen, the INT DOM also showed higher mineralisation. These results suggest that the leachate mineralisations are short-term processes; when the fractionation of the leachates occurs, the LMW had organic compounds with more accessibility for heterotrophic metabolism. On the other hand, when compared to INT DOM, the HMW and LMW were less consumed suggesting an interaction of the reactivity of the leachate. Our data suggest that in the Barra Bonita Reservoir the mineralisation of P. stratiotes leachates occurs through two competitive pathways (i.e. mineralisation of the labile compounds and formation of recalcitrant organic resources and their mineralisation) in which the oxygen availability and the molecular mass of DOM can interfere in the rates of reactions.
本研究探讨了水生植物大薸（水浮莲）渗滤液分解的动力学方面。该物种采自巴西圣保罗州的巴拉博尼塔水库。用高分子量（HMW）、低分子量（LMW）和整体（INT = HMW + LMW）溶解有机物（DOM）与水库水稀释制备分解室。样品在20℃下、黑暗中、有氧或厌氧条件下孵育。在79天内，测量溶解氧（DO）和有机碳（OC）的浓度。为了计算脱氧系数（kd）和最大耗氧量（COmax），对DO浓度进行积分并拟合到一级动力学模型，该模型也适用于OC浓度的消耗。INT孵育的COmax比HMW和LMW组分的总和高4%。所有处理的脱氧系数kd具有相同的数量级。关于碳衰减，无论氧气是否可用，INT DOM也显示出更高的矿化作用。这些结果表明渗滤液矿化是短期过程；当渗滤液发生分馏时，LMW具有更易被异养代谢利用的有机化合物。另一方面，与INT DOM相比，HMW和LMW的消耗量较少，表明渗滤液的反应性存在相互作用。我们的数据表明，在巴拉博尼塔水库中，大薸渗滤液通过两种竞争途径发生矿化（即易分解化合物的矿化和难降解有机资源的形成及其矿化），其中氧气可用性和DOM的分子量会影响反应速率。
