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首页> 外文学位 >Fate of agrochemicals in wood chip denitrifying reactors and their impacts on wood chip microbial ecology.
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Fate of agrochemicals in wood chip denitrifying reactors and their impacts on wood chip microbial ecology.

机译：木屑反硝化反应器中农用化学品的命运及其对木屑微生物生态学的影响。

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摘要

Subsurface tile drainage systems have contributed towards increasing agricultural production, but have also contributed towards water pollution by rapidly transporting excessive nutrient and agrochemicals to surface water and ground water. One of the pollution control strategies is to treat the tile drainage water or the contaminated subsurface water with denitrifying bioreactors. Wood chips have been used in denitrifying bioreactors, providing organic carbon and attachment surface area for denitrifiers. The focus of this research is to investigate fate of agrochemicals in wood chips from the in situ reactors and their potential effects on denitrification and the denitrifiers. The selected agrochemicals for study are atrazine, enrofloxacin, monensin and sulfamethazine.;Partition coefficients of atrazine, enrofloxacin, monensin and sulfamethazine were determined by single-point sorption experiments by using wood chips from an in situ reactor. Of the four chemicals tested, enrofloxacin had the highest partition coefficient (Kow) while sulfamethazine had the lowest. Atrazine and monensin had moderate sorption coefficients. In addition, partition coefficients for the four chemicals for wood chips were larger than the partition coefficients for soils obtained close to the in situ reactor. Freundlich distribution coefficients (Kf) for isotherm studies for the four chemicals were in the order of (highest to lowest): enrofloxacin > monensin > atrazine > sulfamethazine. Desorption hysteresis were found for enrofloxacin, atrazine and sulfamethazine when the wood chips were desorbed by water. For monensin, the desorption aqueous phase concentrations were larger than the adsorption aqueous phase content. A possible reason for the larger desorption concentration was that the monensin adsorbed onto wood chips were on the eternal surface of the wood chips due to its larger molecular structure which allowed monensin to be easily desorbed. Only 5% of enrofloxacin, 14% of monensin, 23% of sulfamethazine and 25% of atrazine were recovered from the wood chips after two desorption and an acetonitrile-water extraction indicating the strong binding of the chemicals onto wood chips.;Degradation studies with atrazine, enrofloxacin, and sulfamethazine onto wood chips indicate that a large majority of the chemical mass was removed from the aqueous phase within the first 48 hours followed by a slow removal over time. Dissipation rates were estimated using the availability-adjusted first-order degradation model. Disappearance of sulfamethazine was slower than disappearance of enrofloxacin and atrazine. No impact on denitrifiers as measured by the denitrification potential assays, most-probable-number (MPN) and nosZ1 copy number was found for atrazine at an initial concentration of 5 mg L-1. The MPN was reduced under enrofloxacin treatment after 2 days of the incubation; however, at the end of the experiment the denitrifier MPN was similar to control treatment MPN. Sulfamethazine was found to initially impact the denitrification (both MPN, nosZ1 copy number and denitrification potential) but after 5 days the denitrification potential assays, most-probable-number (MPN) and nosZ1 copy number were found to be similar to that of the control.
机译：地下瓷砖排水系统有助于提高农业产量，但也通过将过量的营养物和农药快速输送到地表水和地下水中，从而对水污染做出了贡献。污染控制策略之一是用脱氮生物反应器处理瓷砖排水或受污染的地下水。木屑已用于生物反应器的反硝化，为反硝化器提供有机碳和附着表面积。这项研究的重点是调查原位反应堆中木片中农药的命运及其对反硝化和反硝化剂的潜在影响。用于研究的农用化学品为阿特拉津，恩诺沙星，莫能菌素和磺胺二甲基嘧啶。阿特拉津，恩诺沙星，莫能菌素和磺胺二甲嘧啶的分配系数是通过原位反应器中的木屑通过单点吸附实验确定的。在所测试的四种化学品中，恩诺沙星的分配系数（Kow）最高，而磺胺二甲嘧啶的分配系数最低。阿特拉津和莫能菌素具有中等的吸附系数。另外，四种木屑化学药品的分配系数大于靠近原位反应器获得的土壤的分配系数。四种化学物质的等温研究的弗氏分布系数（Kf）顺序为（从高到低）：恩诺沙星>莫能菌素>阿特拉津>磺胺二甲嘧啶。当木片被水解吸时，发现恩诺沙星，阿特拉津和磺胺二甲基嘧啶的解吸滞后。对于莫能菌素，解吸水相浓度大于吸附水相含量。较大的解吸浓度的可能原因是吸附在木片上的莫能菌素由于其较大的分子结构而使莫能菌素易于解吸，因此其在木片的外表面上。经过两次解吸和乙腈-水萃取后，从木片中仅回收了5％的恩诺沙星，莫能菌素14％，磺胺二甲嘧啶23％和阿特拉津25％，表明该化学物质与木片具有很强的结合力。阿特拉津，恩诺沙星和磺胺二甲嘧啶在木片上的现象表明，大部分化学物质在头48小时内从水相中去除，然后随时间缓慢去除。使用可用性调整的一阶退化模型估算耗散率。磺胺二甲嘧啶的消失比恩诺沙星和阿特拉津的消失要慢。通过反硝化潜能测定法对反硝化剂没有影响，初始浓度为5 mg L-1的阿特拉津没有发现最可能数（MPN）和nosZ1拷贝数。孵育2天后，在恩诺沙星治疗下MPN降低；然而，在实验结束时，反硝化剂MPN与对照处理MPN相似。发现磺胺二甲嘧啶最初会影响反硝化作用（MPN，nosZ1拷贝数和反硝化潜能），但在5天后，反硝化潜能分析，最可能数（MPN）和nosZ1拷贝数与对照相似。 。

著录项

  • 作者

    Ilhan, Zehra Esra.;

  • 作者单位

    Iowa State University.;

  • 授予单位 Iowa State University.;
  • 学科 Environmental Sciences.
  • 学位 M.S.
  • 年度 2010
  • 页码 113 p.
  • 总页数 113
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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