Hidden dangers in 'acid rain' soils
Biochar Editorial Office, Shenyang Agricultural University
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Acid deposition fuels pathogen risk through a coupled ecological and evolutionary cascade
view moreCredit: Liliang Wang, Yunhao Wang, Yonghui Xing, Chunhui Gao, Yichao Wu, Chenchen Qu, Ke Dai, Ming Zhang, Qiaoyun Huang & Peng Cai
Acid rain from fossil fuel pollution may be quietly training soil bacteria to become longer-lived, more transmissible, and more deadly, according to a new study in the journal New Contaminants that tracks how a notorious foodborne pathogen rapidly evolved under simulated acid deposition.
Acid deposition from burning coal, oil, and other fossil fuels has long been known to damage forests, lakes, and crops, but its impact on disease-causing microbes in soil has been largely overlooked. The new research shows that acid rain can destabilize the native soil microbiome in ways that make it easier for the pathogen Escherichia coli O157:H7 to invade and persist. In global soil metagenomic data from 2,874 sites, the team found that E. coli abundance peaks in mildly acidic soils around pH 5, pointing to soil acidification as a powerful ecological pressure shaping this pathogen’s success.
“Pollution is not just stressing ecosystems, it is also giving dangerous bacteria a chance to adapt, spread, and become more harmful to humans,” said senior author Peng Cai of Huazhong Agricultural University. “Our results suggest that acid deposition can act as an unseen accelerator for the evolution of high-risk pathogens.”
A 150-day “evolution experiment” in soil
To probe this risk, the researchers ran a 150-day greenhouse experiment using forest soil from Henan Province, China, repeatedly treated with simulated rain at three acidity levels and inoculated with E. coli O157:H7, a major cause of severe foodborne illness. While pathogen numbers declined over time in all treatments, acid rain significantly slowed the die-off, with mildly acidic rain maintaining up to 100 times more bacteria than normal rain at certain time points and leaving several-fold higher populations after five months.
Surprisingly, the overall composition and diversity of the native bacterial community remained relatively stable, but its internal interaction network changed dramatically. Acid rain and pathogen invasion simplified the network and increased negative interactions, indicating intensified internal competition that weakened the community’s natural “biotic resistance” to invaders and opened ecological space for E. coli O157:H7 to persist.
From soil survivor to “super colonizer”
By the end of the experiment, the team isolated multiple independently evolved E. coli lineages that had adapted to the acid-stressed soil environment. These strains showed altered colony color, enhanced biofilm formation, and changes in motility, as well as shifts in how they used different carbon sources. When the evolved strains were returned to soil, they outcompeted their ancestor, reaching 6- to 450-fold higher abundances after 60 days, demonstrating a major boost in long-term colonization ability.
Phenotypic analyses revealed that the most successful lineages balanced moderate biofilm formation with efficient movement, rather than maximizing a single trait. Biofilm and motility together explained most of the variation in soil colonization, showing how acid rain had nudged the pathogen toward an optimized “survival toolkit” for life in disturbed soils.
Deep genetic rewiring under pollution stress
Gene expression profiling showed that evolved strains switched on a coordinated module of functions that govern movement, biofilm building, chemical communication, and virulence. Key quorum sensing and biofilm regulators sat at the center of a highly connected expression network, tightly linked to motility and pathogenicity genes, indicating a systemic upgrade rather than isolated changes.
Whole-genome sequencing of the top colonizers revealed that this rapid evolution was driven largely by structural genome changes. Independent lineages shared a convergent chromosomal inversion near an acid-response regulator, while one highly fit strain carried a deletion that removed a major stress-sensing regulatory system thought to restrain biofilm production, potentially freeing downstream virulence and colonization traits from tight control.
Stronger threats to the food chain and health
Crucially, the evolved environmental adaptations translated directly into greater risk along the food chain and in animals. In lettuce pot experiments mimicking contamination from irrigated soil, evolved strains reached up to eight times higher levels in edible leaves compared with the ancestral strain, indicating a much greater chance of reaching consumers on fresh produce.
In mouse infection tests, the adapted lineages grew to higher levels in the gut and caused far more severe disease. Mortality rose from about 10 percent in animals exposed to the original strain to around 50 percent for some evolved strains, which produced extensive intestinal damage and lesions beyond the gut. These outcomes matched the observed upregulation of virulence genes, confirming that acid rain–driven adaptation had created not just tougher environmental survivors, but more lethal pathogens.
Pollution and pathogen evolution: a feedback loop
Together, the results outline a three-step eco-evolutionary cascade: acid deposition destabilizes soil microbial defenses, this disturbance favors the survival and rapid evolution of invading pathogens, and the resulting strains are better at colonizing crops and causing severe disease. The authors argue that industrial pollution and pathogen evolution can form a dangerous positive feedback loop, in which environmental stressors unintentionally train “super pathogens” with heightened public health impact.
The study highlights the need to integrate microbial evolution into environmental and food safety risk assessments, especially in regions with ongoing acid deposition and intensive agriculture. Reducing emissions that drive acid rain, the researchers suggest, could help protect not only ecosystems but also human populations from emerging, pollution-fueled disease threats.
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Journal reference: Wang L, Wang Y, Xing Y, Gao C, Wu Y, et al. 2025. Acid deposition fuels pathogen risk through a coupled ecological and evolutionary cascade. New Contaminants 1: e012
https://www.maxapress.com/article/doi/10.48130/newcontam-0025-0012
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About the Journal:
New Contaminants is an open-access journal focusing on research related to emerging pollutants and their remediation.
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Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Acid deposition fuels pathogen risk through a coupled ecological and evolutionary cascade
Article Publication Date
22-Nov-2025
New electrochemical strategy boosts uranium recovery from complex wastewater
Biochar Editorial Office, Shenyang Agricultural University
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Synergistic parameter optimization in electrochemical upcycling of uranyl: mechanisms and perspectives of self-standing COF electrodes
view moreCredit: Tao Wen, Muhammad Wakeel
Researchers have unveiled a promising new method that could transform how uranium is recovered from challenging wastewater streams. By combining a specially engineered covalent organic framework with an indirect electrochemical process, the approach delivers high efficiency, long term stability, and strong tolerance to chemically complex environments. The findings provide fresh insight into how advanced functional materials and optimized operating conditions can work together to support cleaner and more sustainable nuclear energy development.
Uranium is a vital resource for nuclear power generation, yet conventional mining faces growing environmental and economic pressures. Scientists worldwide are exploring new ways to extract uranium from unconventional sources such as wastewater, seawater, and contaminated industrial effluents. Electrochemical uranium extraction has emerged as an attractive alternative because it allows controllable operation, rapid response, and high selectivity. However, the technology still struggles with issues like electrode passivation, interference from competing ions, and the high cost of fabricating efficient electrodes.
A recent study addressed these limitations by creating a self standing covalent organic framework electrode capable of performing two tasks simultaneously. Built on a carbon cloth support, the electrode contains a polyarylether backbone that drives the oxygen reduction reaction to produce hydrogen peroxide, along with amidoxime groups that selectively bind uranyl ions. The combination provides a coordinated chemical and electrochemical pathway that greatly improves the extraction process.
One of the strengths of the study is its systematic evaluation of the factors that influence extraction performance. The researchers found that solution pH plays a central role. In acidic environments, protonation of the amidoxime groups reduces their ability to attract uranium. In contrast, neutral to alkaline conditions promote stronger binding and support the formation of studtite, a crystalline uranium peroxide compound that forms during extraction. When the pH is maintained within a favorable range, the system achieves extraction efficiencies above 90 percent.
Applied voltage is another key parameter. The rate of hydrogen peroxide production depends directly on the voltage, which controls the two electron oxygen reduction reaction. Increasing the applied potential significantly improves uranium recovery by elevating the local concentration of hydrogen peroxide near the electrode surface. This accelerates studtite formation and boosts extraction efficiency, especially at high uranium concentrations.
The system also shows excellent resistance to interference from sodium ions and organic additives commonly found in real wastewater. Even in solutions with high ionic strength or complex organic components, the electrode maintains uranium extraction efficiencies above 85 percent. This resilience reflects the strong intrinsic selectivity of amidoxime groups for uranyl ions.
Long term performance tests further illustrate the durability of the approach. In organic rich radioactive wastewater, the electrode accumulated more than nine thousand milligrams of uranium per gram of material over 450 hours of continuous operation, which ranks among the highest values reported for electrochemical uranium extraction systems.
The synergistic mechanism behind this success involves two interconnected steps. First, amidoxime groups chelate uranyl ions and initiate nucleation. Second, electro generated hydrogen peroxide drives sustained crystal growth. Together, these processes enable stable and efficient extraction even under difficult chemical conditions.
The authors note that several challenges remain before the technology can be widely deployed, including improving electrode fabrication, reducing sensitivity to pH fluctuations, and preventing blockage of active sites during long term operation. They highlight future directions such as machine learning guided material design, advanced voltage control strategies, operando characterization, and modular flow system engineering to support large scale applications.
This research provides an important step toward practical, high performance uranium recovery systems that can operate in complex real world environments. It also offers valuable guidance for designing next generation electrochemical materials and processes for environmental remediation and resource recovery.
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Journal reference: Wen T, Wakeel M. 2025. Synergistic parameter optimization in electrochemical upcycling of uranyl: mechanisms and perspectives of self-standing COF electrodes. Sustainable Carbon Materials 1: e008
https://www.maxapress.com/article/doi/10.48130/scm-0025-0009
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About Sustainable Carbon Materials:
Sustainable Carbon Materials is a multidisciplinary platform for communicating advances in fundamental and applied research on carbon-based materials. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of carbon materials around the world to deliver findings from this rapidly expanding field of science. It is a peer-reviewed, open-access journal that publishes review, original research, invited review, rapid report, perspective, commentary and correspondence papers.
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Method of Research
News article
Subject of Research
Not applicable
Article Title
Synergistic parameter optimization in electrochemical upcycling of uranyl: mechanisms and perspectives of self-standing COF electrodes
Article Publication Date
26-Nov-2025
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