Institute of Environmental Science and Research, PO Box 29181, Christchurch 8540, New Zealand.
Institute of Environmental Science and Research, PO Box 29181, Christchurch 8540, New Zealand.
Sci Total Environ. 2022 Oct 20;844:157146. doi: 10.1016/j.scitotenv.2022.157146. Epub 2022 Jul 4.
Synthetic DNA tracers are gaining interest as tools for tracking contamination pathways and hydraulic connections in surface water and groundwater systems. However, few quantitative data exist that describe DNA tracer degradation and adsorption in environmental matrices. We undertook laboratory experiments to quantify the degradation of multiple double-stranded DNA tracers in stream water, groundwater, and domestic and dairy-shed effluent, and adsorption to stream sediments, soils, coastal sand aquifer media and alluvial sandy gravel aquifer media. Faster DNA tracer degradation seemed to be associated with high bacterial concentrations in the liquid phase. Overall, the degradation of the 352 base pair (bp) DNA tracers in the aqueous phase was significantly (P = 0.018) slower than that of the 302 bp DNA tracers. Although the tracers' internal amplicon lengths were similar, the longer non-amplified flanking regions of the 352 bp tracers may better protect them from environmental degradation. Thermodynamic analysis suggests that longer flanking regions contribute to greater tracer stability. This finding may explain our previous field observations that 352 bp tracer mass reductions were often lower than 302 bp tracer mass reductions. The 2 sets of DNA tracers did not differ significantly regarding their adsorption to stream sediment-stream water or aquifer media-groundwater mixtures (P > 0.067), but the 352 bp tracers showed significantly less adsorption to soil-effluent mixtures than the 302 bp tracers (P = 0.005). The DNA tracers' adsorption to soil-effluent mixtures was comparatively less than their adsorption to the aquifer media-groundwater and stream sediment-stream water mixtures, suggesting that DNA tracers may compete with like-charged organic matter for adsorption sites. These findings provide insights into the fate of DNA tracers in the environment. The DNA tracers' degradation rate constants determined in this study for a range of environmental conditions could assist the design of future field investigations.
合成 DNA 示踪剂作为追踪地表水和地下水系统污染途径和水力联系的工具越来越受到关注。然而，描述 DNA 示踪剂在环境基质中降解和吸附的定量数据很少。我们进行了实验室实验，以量化多种双链 DNA 示踪剂在溪流水中、地下水中以及家庭和奶牛场污水中的降解情况，以及在溪流沉积物、土壤、沿海砂含水层介质和冲积砂卵石含水层介质中的吸附情况。在液相中，细菌浓度越高，DNA 示踪剂的降解速度似乎越快。总的来说，352 个碱基对（bp）DNA 示踪剂在水相中的降解速度明显（P = 0.018）慢于 302 bp DNA 示踪剂。尽管示踪剂的内部扩增子长度相似，但 352 bp 示踪剂较长的非扩增侧翼区域可能更好地保护它们免受环境降解。热力学分析表明，较长的侧翼区域有助于提高示踪剂的稳定性。这一发现可能解释了我们之前的野外观察结果，即 352 bp 示踪剂质量的减少通常低于 302 bp 示踪剂质量的减少。两组 DNA 示踪剂在吸附到溪流沉积物-溪流水或含水层介质-地下水混合物方面没有显著差异（P > 0.067），但 352 bp 示踪剂对土壤-污水混合物的吸附明显小于 302 bp 示踪剂（P = 0.005）。与含水层介质-地下水和溪流沉积物-溪流水混合物相比，DNA 示踪剂对土壤-污水混合物的吸附相对较少，这表明 DNA 示踪剂可能与带相同电荷的有机物竞争吸附位点。这些发现为 DNA 示踪剂在环境中的命运提供了一些见解。本研究在一系列环境条件下确定的 DNA 示踪剂降解速率常数可协助未来现场调查的设计。
