Moser Duane P, Fredrickson James K, Geist David R, Arntzen Evan V, Peacock Aaron D, Li Shu-Mei W, Spadoni Tina, McKinley James P
Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA.
Environ Sci Technol. 2003 Nov 15;37(22):5127-34. doi: 10.1021/es034457v.
Biogeochemical processes within riverbed hyporheic zones (HZ) can potentially impact the fate and transport of contaminants. We evaluated a modified freeze core technique for the collection of intact cobble-bed samples from the Columbia River HZ along a stretch of the Hanford Reach in Washington State and investigated microbiological and geochemical parameters of corresponding frozen and unfrozen samples. During three sampling periods (March, May, and November 2000), relatively high numbers of viable aerobic heterotrophic bacteria were recovered from both unfrozen (10(6)-10(7) cfu/g) and frozen samples (10(5)-10(6) cfu/g). Relatively large populations of sulfate-, nitrate-, and iron-reducing bacteria were present, and significant concentrations of acid-volatile sulfide were measured in some samples, indicating that anoxic regions exist within this zone. Cr(VI), a priority groundwater pollutant on adjacent U.S. Department of Energy lands, was probably removed from solution in HZ samples by a combination of microbial activity and chemical reduction, presumably via products of anaerobic microbial metabolism. These results suggest that biogeochemical processes in the Columbia River HZ may contribute to the natural attenuation of Cr(VI). Although freezing modestly diminished recovery of viable bacteria, freeze core techniques proved reliable for the collection of intact hyporheic sediments.
河床潜流带（HZ）内的生物地球化学过程可能会影响污染物的归宿和迁移。我们评估了一种改良的冻芯技术，用于从华盛顿州汉福德河段沿线的哥伦比亚河潜流带采集完整的卵石床样本，并研究了相应冷冻和未冷冻样本的微生物和地球化学参数。在三个采样期（2000年3月、5月和11月），从未冷冻样本（10⁶ - 10⁷ cfu/g）和冷冻样本（10⁵ - 10⁶ cfu/g）中均回收了相对大量的可培养好氧异养细菌。存在相对大量的硫酸盐还原菌、硝酸盐还原菌和铁还原菌，并且在一些样本中检测到了显著浓度的酸挥发性硫化物，表明该区域内存在缺氧区域。六价铬是美国能源部相邻土地上的一种优先地下水污染物，在潜流带样本中可能通过微生物活动和化学还原的组合从溶液中去除，推测是通过厌氧微生物代谢产物。这些结果表明，哥伦比亚河潜流带中的生物地球化学过程可能有助于六价铬的自然衰减。尽管冷冻适度降低了可培养细菌的回收率，但冻芯技术被证明对于采集完整的潜流沉积物是可靠的。
