The benefits of an electron-transfer mechanism for petroleum biodegrading have been widely acknowledged, but few have studied the spatial pattern of microbial community diversity in groundwater fields, and few discuss the bacterial community’s diversity in relation to electron donors-acceptors distribution, which is largely determined by groundwater flow. Eleven samples in different groundwater fields are collected at a petroleum-contaminated site, and the microbial communities are investigated using 16S rRNA gene sequences with multivariate statistics. These are mainly linked to the chemical composition analysis of electron donor indexes COD, BTEX and electron acceptor indexes DO, NO₃⁻, Fe²⁺, Mn²⁺, and SO₄²⁻, HCO₃⁻. The spatial pattern of the bacterial community’s diversity is characterized and the effect of the electron redox reaction on bacterial community formation in different groundwater field zones is elucidated. It is found that a considerable percentage (>65%) of the bacterial communities related to petroleum degrading suggest that petroleum biodegrading is occurring in groundwater. The communities are subject to the redox reaction in different groundwater field zones: The side plume zone and the upstream of the source zone are under aerobic redox or denitrification redox, and the corresponding bacteria are Rhodoferax, Novosphingobium, Hydrogenophaga, and Comamonas; the source zone and downstream of the source zone are under Fe³⁺, Mn⁴⁺, and SO₄²⁻ reduction redox, and the corresponding bacteria are Rhodoferax, Treponema, Desulfosporosinus, Hydrogenophaga, and Acidovorax. These results imply that groundwater flow plays a definitive role in the bacterial community’s diversity spatial pattern formation by influencing the distribution of electron donor and acceptor.

To ensure adequate oil supply and mitigate geopolitical uncertainties, China has diversified its sources of crude oil imports in recent years. Central Asia is a neighbor region of China, rich in oil and natural gas reserves, which can play an important role in China’s strategy to reduce its dependence on energy supplies from the Middle East. The geopolitical attributes of energy and the geopolitical situation in Central Asia determine that Central Asia’s energy development and cooperation are disturbed by domestic and foreign factors, and also face the risks of complex energy structural evolution and geopolitical games, which create a unique energy geopolitical pattern in Central Asia. This study proposes an analysis framework for energy geopolitics in Central Asia, arguing that the complexity of energy geopolitics in Central Asia can be demonstrated from the perspectives of both the main countries of energy development (game actors) and the whole-industry-chain of energy development (game themes). The most obvious feature of Central Asian energy geopolitics is the fierce game that is played between key countries and regions, Russia, the United States, China, the European Union (EU), Japan, India, Iran, and Turkey. Strategic geopolitical considerations and resource requirements necessitate the active participation of these players in Central Asian energy development and mean that the foreign policy agendas of states in this region are likely to become ever more crowded. Therefore, the energy cooperation between China and Central Asia faces the geopolitical risks of the great power games. It is necessary to develop reasonable and effective policies to establish guarantee mechanisms to minimize the risks of energy cooperation. This study characterizes the energy geopolitical strategies of Russia, the United States, China, and other related powers in Central Asia. It also assesses the country risks faced by energy cooperation between China and Central Asian countries. To withstand possible geopolitical and country risks, this study develops a series of policy frameworks which can be used to fortify the stability of the energy cooperation between China and Central Asian countries, and can also be effective in responding to the array of risks that might be encountered in the coming years.

In petroleum-contaminated aquifers, iron (III) serves as an electron acceptor, enabling microbial degradation of organic matter. While previous studies have focused on iron reduction and organic matter degradation under laboratory conditions, research on iron-associated microorganisms in petroleum-contaminated aquifers is limited. To explore the diversity and distribution of such microorganisms in natural settings, this study used metagenomic analysis of an iron-rich, petroleum-contaminated aquifer. Sixteen groundwater samples from both pollution source and background areas were collected for species annotation and functional gene identification. Results show more than 7000 species were identified as iron-reducing microorganisms (IRMs), including several previously well-characterized iron-reducing species (e.g., Geobacter luticola and Geobacter sulfurreducens). However, the majority of IRMs were not found in existing iron-reducing microbial databases. Some of them, such as Sulfurospirillum sp. and Extensimonas perlucida, could be taxonomically classified at the species level, while most were only annotated as unclassified bacteria. In the contamination source zone, these microorganisms proliferated extensively, which led to hydrocarbon degradation predominantly driven by iron reduction in the aquifer. This study enhances our understanding of hydrocarbon-degrading microorganisms and supports the management of petroleum-contaminated sites.