美国科罗拉多大学的微生物科学家与美国地质调查部门的科学家合作研究发现，微量的杀菌剂磺胺甲恶唑（ sulfamethoxazole ）会使地下水中硝酸根还原能力下降，最终导致地下水富化。美国《 CEN 》以及《 Environ. Sci. Technol. 》 的相关报道如下 Antibiotic Pollution May Increase Groundwater Nitrate Water Pollution: Compound slows growth of nitrate-reducing bacteri a Charlie Schmidt Decades after spawning a health care revolution, antibiotics are now common pollutants. Scientists' biggest concern about these emerging contaminants is that they promote the spread of resistance. But new research suggests they also harm the microbes that cleanse groundwater of dangerous compounds, particularly nitrates ( Environ. Sci. Technol. , DOI: 10.1021/es103605e ). High nitrate levels in drinking water can cause methemoglobinemia, a disease that decreases the blood's oxygen carrying capacity. Naturally-occurring bacteria in groundwater, such as Pseudomonas putida , can remove nitrates by reducing them to nitrogen gas. In Cape Cod, Mass., very high nitrate levels co-occur in groundwater with one of the most common antibiotics in the clinical arsenal: sulfamethoxazole (SMX). For nearly a decade, microbiologist Ronald Harvey and colleagues from the U.S. Geological Survey have tracked SMX and other groundwater pollutants at an aquifer that originates at the Otis Air National Guard Base, a heavily polluted site on Cape Cod. Other researchers had shown that high doses of SMX can interfere with bacterial nitrate reduction. But no one knew if a similar response might occur at environmentally-relevant concentrations. To answer that question, Harvey's team first cultured bacteria from a non-contaminated portion of the aquifer. Next, they added nitrate to the cultures at levels measured in the environment, along with SMX at doses ranging from 0.005 to 2,000 M. Bacterial growth rates dropped at all doses. At the environmentally relevant concentration of 0.005 M SMX, the amount of total nitrate that the bacteria removed from the culture fell by nearly half. "We're demonstrating a clear biological effect," Harvey says. "And we're showing that in the same bacteria that live in this particular aquifer." Harvey says that the next step would be to study the bacteria's response to SMX exposure in the aquifer itself. USGS research hydrologist Dana Kolpin , who didn't participate in this study, thinks the results suggest that SMX contamination might account at least in part for high nitrate levels in the aquifer. "We can't jump to that conclusion yet," he says. "But the data suggest that's a hypothesis worth pursuing." 下面是原文摘要： Effects of the Antimicrobial Sulfamethoxazole on Groundwater Bacterial Enrichment The effects of “trace” (environmentally relevant) concentrations of the antimicrobial agent sulfamethoxazole (SMX) on the growth, nitrate reduction activity, and bacterial composition of an enrichment culture prepared with groundwater from a pristine zone of a sandy drinking-water aquifer on Cape Cod, MA, were assessed by laboratory incubations. When the enrichments were grown under heterotrophic denitrifying conditions and exposed to SMX, noticeable differences from the control (no SMX) were observed. Exposure to SMX in concentrations as low as 0.005 μM delayed the initiation of cell growth by up to 1 day and decreased nitrate reduction potential (total amount of nitrate reduced after 19 days) by 47% ( p = 0.02). Exposure to 1 μM SMX, a concentration below those prescribed for clinical applications but higher than concentrations typically detected in aqueous environments, resulted in additional inhibitions: reduced growth rates ( p = 5 × 10−6), lower nitrate reduction rate potentials ( p = 0.01), and decreased overall representation of 16S rRNA gene sequences belonging to the genus Pseudomonas . The reduced abundance of Pseudomonas sequences in the libraries was replaced by sequences representing the genus Variovorax . Results of these growth and nitrate reduction experiments collectively suggest that subtherapeutic concentrations of SMX altered the composition of the enriched nitrate-reducing microcosms and inhibited nitrate reduction capabilities.
由于水资源紧缺，塔里木河下游生态正处于严重退化之中。大批胡杨树死亡、沙漠化加剧。为了减缓生态退化，国家从2000年起，花费巨资（107亿元）实施跨流域调水工程。迄今已经累计调水23亿方。在内陆干旱区开展大规模人工补给地下水的生态修复工程，举世罕见。然而，这项史无前例的生态工程给塔里木河下游地下水带来了什么样的变化？未来生态走势如何？这是政府和科技界普遍关注的重大问题。 在国家自然科学基金、中科院知识创新工程重要方向项目、水资源项目资助下，地质与地球物理研究所工程地质与水资源研究室庞忠和研究员课题组自2005年起对塔里木河流域水循环与生态开展了系统的同位素水文学研究。该课题组培养的博士生黄天明与庞忠和研究员合作发表的关于塔河下游地下水的文章最近发表于国际水文学权威刊物 Journal of Hydrology （Huang T and Pang Z. 2010. Changes in groundwater induced by water diversion in the Lower Tarim River, Xinjiang Uygur, NW China: Evidence from environmental isotopes and water chemistry. Journal of Hydrology 387: 188-201）。，该成果对于评估调水对于缓解生态退化的效果、调水方式的优化等提供了科学依据。 基于对下游9个地下水监测剖面的40个观测井开展的现场观测，作者对大气水、地表水、地下水、6个土壤剖面开展了系统的水化学、氢氧稳定同位素和氚含量采样和综合研究，得出以下结论： （1）经过8次应急输水，在距离河道700m以内地下水位呈上升趋势； （2）地下水的含盐量受河水含盐量、前期地下水含盐量、含水层含盐量、包气带含盐量及水动力条件综合影响，总体呈下降趋势； （3）下游河岸地下水受现代水补给（包括调水补给和1960s以来补给）的范围十分有限，从上到下分别距河道600-200m以内，小于水位上升区域，说明水位上升是由压力传导而非水分子本身补给； （4）下游地下水的氢氧同位素位于大气降水线以下，又平行于降水线，表明入渗过程中的等量蒸发作用； （5）适于下游主要植被（胡杨、红柳）生长的最小地下水埋深（小于5m）面积十分有限，在距离河道200m以内，且向下游逐渐减少； （6）干旱河岸生态系统是历史时期由于季节性洪水等形成的。调水虽然在一定程度上缓解，但仍不能阻止其退化的总趋势。 作者据此对塔里木河调水修复生态工程提出以下建议：（1）从全流域水资源统一利用和管理着眼，制定可持续的水资源利用和生态保护方案，保证输水的继续；（2）进一步对塔里木河下游地下水水动力条件、包气带、水化学及与生态系统相互作用进行研究。
标签: 地下水
