Yeo Seul-Ki, Park Jun-Boum, Ahn Joo-Sung, Han Young-Soo
Korea Institutes of Geoscience and Mineral Resources, Gwahang-ro 124, Daejeon, Republic of Korea.
Environ Monit Assess. 2015 Jun;187(6):347. doi: 10.1007/s10661-015-4559-6. Epub 2015 May 13.
In the recent half century, numerous methods have been developed to assess ecological toxicity. However, the presence of solid-particle turbidity sometimes causes such tests to end with questionable results. Many researchers focused on controlling this arbitrary turbidity effect when using the Microtox® solid-phase toxicity system, but there is not yet a standard method. In this study, we examined four solid-phase sample test methods recommended in the Microtox® manual, or proposed from the literature, and compared the existing methods with our proposed method (centrifuged basic solid-phase test, c-BSPT). Four existing methods use the following strategies to control turbid particles: complete separation of liquid and solid using 0.45-μm filtration before contacting solid samples and bacteria, natural settlement, moderate separation of large particles using coarser pore size filtration, and exclusion of light loss in the toxicity calculation caused by turbidity after full disturbance of samples. Our proposed method uses moderate centrifugation to separate out the heavier soil particles from the lighter bacteria after direct contact between them. Among the solid-phase methods tested, in which the bacteria and solid particles were in direct contact (i.e., the three existing methods and the newly proposed one, c-BSPT), no single method could be recommended as optimal for samples over a range of turbidity. Instead, a simple screening strategy for selecting a sample-dependent solid-phase test method was suggested, depending on the turbidity of the solid suspension. The results of this study highlight the importance of considering solid particles, and the necessity for optimal selection of test method to reduce errors in the measurement of solid-phase toxicity.
在最近的半个世纪里，已经开发出了许多评估生态毒性的方法。然而，固体颗粒浊度的存在有时会导致此类测试结果存疑。许多研究人员在使用Microtox® 固相毒性系统时致力于控制这种任意的浊度影响，但尚未有标准方法。在本研究中，我们考察了Microtox® 手册中推荐的或文献中提出的四种固相样品测试方法，并将现有方法与我们提出的方法（离心基本固相测试，c-BSPT）进行了比较。四种现有方法采用以下策略来控制浑浊颗粒：在固体样品与细菌接触之前，使用0.45μm过滤将液体和固体完全分离，自然沉降，使用孔径较大的过滤器适度分离大颗粒，以及在充分扰动样品后排除浊度在毒性计算中造成的光损失。我们提出的方法是在细菌和固体颗粒直接接触后，通过适度离心将较重的土壤颗粒与较轻的细菌分离。在所测试的固相方法中，即细菌和固体颗粒直接接触的方法（即三种现有方法和新提出的c-BSPT），没有一种方法可以被推荐为在一系列浊度范围内对样品都是最优的。相反，根据固体悬浮液的浊度，提出了一种简单的筛选策略，用于选择依赖于样品的固相测试方法。本研究结果突出了考虑固体颗粒的重要性，以及为减少固相毒性测量误差而优化选择测试方法的必要性。
