U.S. Salinity Laboratory USDA, ARS, 450 W. Big Springs Road, Riverside, California 92507-4617, United States.
Department of Mineral Resources and Energy Engineering, Chonbuk National University , 664-14 Duckjin, Jeonju, Jeonbuk 561-756, Republic of Korea.
Environ Sci Technol. 2016 Feb 2;50(3):1295-303. doi: 10.1021/acs.est.5b05296. Epub 2016 Jan 13.
The U.S. Environmental Protection Agency has recommended the use of aerobic spores as an indicator for Cryptosporidium oocysts when determining groundwater under the direct influence of surface water. Surface properties, interaction energies, transport, retention, and release behavior of B. subtilis spores were measured over a range of physicochemical conditions, and compared with reported information for C. parvum oocysts. Interaction energy calculations predicted a much larger energy barrier and a shallower secondary minimum for spores than oocysts when the solution ionic strength (IS) equaled 0.1, 1, and 10 mM, and no energy barrier when the IS = 100 mM. Spores and oocysts exhibited similar trends of increasing retention with IS and decreasing Darcy water velocity (qw), and the predicted setback distance to achieve a six log removal was always larger for spores than oocysts. However, low levels of observed spore and oocyst release significantly influenced the predicted setback distance, especially when the fraction of reversibly retained microbes (Frev) was high. An estimate for Frev was obtained from large release pulses of spore and oocyst when the IS was reduced to deionized water. The value of Frev always increased with qw, whereas an opposition trend for Frev with IS was observed for spores (decreasing) and oocysts (increasing).
美国环境保护署建议在确定地表水直接影响下的地下水时，使用需氧孢子作为隐孢子虫卵囊的指示物。在一系列物理化学条件下测量枯草芽孢杆菌孢子的表面特性、相互作用能、传输、保留和释放行为，并与报道的小隐孢子虫卵囊信息进行比较。当溶液离子强度（IS）等于 0.1、1 和 10 mM 时，与卵囊相比，相互作用能计算预测孢子的能垒大得多，二次势能最小；当 IS = 100 mM 时，没有能垒。孢子和卵囊都表现出随着 IS 和达西水流速度（qw）的增加而保留率增加的趋势，并且预测达到六对数去除的后退距离对于孢子总是大于卵囊。然而，观察到的孢子和卵囊的低水平释放显著影响了预测的后退距离，尤其是当可逆保留的微生物分数（Frev）较高时。从将 IS 降低至去离子水时的孢子和卵囊的大释放脉冲中获得了 Frev 的估计值。Frev 总是随着 qw 的增加而增加，而对于孢子（减少）和卵囊（增加），Frev 与 IS 呈相反趋势。
