Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons

Impact of arsenic and PAHs compound contamination on microorganisms in coking sites: From a community to individual perspective

Arsenic (As) and polycyclic aromatic hydrocarbons (PAHs) are highly toxic, carcinogenic and teratogenic, and are commonly found in soils of industrial sites such as coking plants. They exert environmental stresses on soil microorganisms, but their compounding effects have not been systematically studied. Exploring the effects of compound contamination on microbial communities, species and genes is important for revealing the ecological damage caused by compound contamination and offering scientific insights into soil remediation strategies. In this study, we selected soil samples from 0 to 100 cm depth of a coking site with As, PAHs and compound contamination. We investigated the compound effects of As and PAHs on microbial communities by combining high-throughput sequencing, metagenomic sequencing and genome assembly. Compared with single contamination, compound contamination reduced the microbial community diversity by 10.68%-12.07% and reduced the community richness by 8.39%-18.61%. The compound contamination decreased 32.41%-46.02% of microbial PAHs metabolic gene abundance, 11.36%-19.25% of cell membrane transport gene abundance and 12.62%-57.77% of cell motility gene abundance. Xanthobacteraceae, the biomarker for compound contaminated soils, harbors arsenic reduction genes and PAHs degradation pathways of naphthalene, benzo [a]pyrene, fluorene, anthracene, and phenanthrene. Its broad metabolic capabilities, encompassing sulfur metabolism and quorum sensing, facilitate the acquisition of energy and nutrients, thereby conferring ecological niche advantages in compound contaminated environments. This study underscores the significant impacts of As and PAHs on the composition and function of microbial communities, thereby enriching our understanding of their combined effects and providing insights for the remediation of compound contaminated sites.

Ambient particle composition and toxicity in 31 major cities in China

Current assessment of air quality or control effectiveness is solely based on particulate matter (PM) mass levels, without considering their toxicity differences in terms of health benefits. Here, we collected a total of 465 automobile air conditioning filters from 31 major Chinese cities to study the composition and toxicity of PM at a national scale. Dithiothreitol assay showed that normalized PM toxicity (NIOG) in different Chinese cities varied greatly from the highest 4.99 × 10-3 for Changsha to the lowest 7.72 × 10-4 for Yinchuan. NIOG values were observed to have significant correlations with annual PM10 concentration (r = -0.416, p = 0.020) and some PM components (total fungi, SO4 2- and calcium element). The concentrations of different elements and water-soluble ions in PM also varied by several orders of magnitude for 31 cities in China. Endotoxin concentrations in PM analyzed using limulus amebocyte lysate assay ranged from 2.88 EU/mg PM (Hangzhou) to 62.82 EU/mg PM (Shijiazhuang) among 31 Chinese cities. Besides, real-time qPCR revealed 10∼100-fold differences in total bacterial and fungal levels among 31 Chinese cities. The concentrations of chemical (water soluble ions and trace elements) and biological (fungi, bacteria and endotoxin) components in PM were found to be significantly correlated with some meteorological factors and gaseous pollutants such as SO2. Our results have demonstrated that PM toxicity from 31 major cities varied greatly up to 6.5 times difference; and components such as fungi and SO4 2- in PM could play important roles in the observed PM toxicity. The city-specific air pollution control strategy that integrates toxicity factors should be enacted in order to maximize health and economic co-benefits. This work also provides a comprehensive view on the overall PM pollution situation in China.

AI-assisted systematic review on remediation of contaminated soils with PAHs and heavy metals

This systematic review addresses soil contamination by crude oil, a pressing global environmental issue, by exploring effective treatment strategies for sites co-contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAHs). Our study aims to answer pivotal research questions: (1) What are the interaction mechanisms between heavy metals and PAHs in contaminated soils, and how do these affect the efficacy of different remediation methods? (2) What are the challenges and limitations of combined remediation techniques for co-contaminated soils compared to single-treatment methods in terms of efficiency, stability, and specificity? (3) How do various factors influence the effectiveness of biological, chemical, and physical remediation methods, both individually and combined, in co-contaminated soils, and what role do specific agents play in the degradation, immobilization, or removal of heavy metals and PAHs under diverse environmental conditions? (4) Do AI-powered search tools offer a superior alternative to conventional search methodologies for executing an exhaustive systematic review? Utilizing big-data analytics and AI tools such as Litmaps.co, ResearchRabbit, and MAXQDA, this study conducts a thorough analysis of remediation techniques for soils co-contaminated with heavy metals and PAHs. It emphasizes the significance of cation-π interactions and soil composition in dictating the solubility and behavior of these pollutants. The study pays particular attention to the interplay between heavy metals and PAH solubility, as well as the impact of soil properties like clay type and organic matter on heavy metal adsorption, which results in nonlinear sorption patterns. The research identifies a growing trend towards employing combined remediation techniques, especially biological strategies like biostimulation-bioaugmentation, noting their effectiveness in laboratory settings, albeit with potentially higher costs in field applications. Plants such as Medicago sativa L. and Solanum nigrum L. are highlighted for their effectiveness in phytoremediation, working synergistically with beneficial microbes to decompose contaminants. Furthermore, the study illustrates that the incorporation of biochar and surfactants, along with chelating agents like EDTA, can significantly enhance treatment efficiency. However, the research acknowledges that varying environmental conditions necessitate site-specific adaptations in remediation strategies. Life Cycle Assessment (LCA) findings indicate that while high-energy methods like Steam Enhanced Extraction and Thermal Resistivity - ERH are effective, they also entail substantial environmental and financial costs. Conversely, Natural Attenuation, despite being a low-impact and cost-effective option, may require prolonged monitoring. The study advocates for an integrative approach to soil remediation, one that harmoniously balances environmental sustainability, cost-effectiveness, and the specific requirements of contaminated sites. It underscores the necessity of a holistic strategy that combines various remediation methods, tailored to meet both regulatory compliance and the long-term sustainability of decontamination efforts.

Health effects of air pollutant mixtures (volatile organic compounds, particulate matter, sulfur and nitrogen oxides) - a review of the literature

The health risks associated with individual air pollutant exposures have been studied and documented, but in real-life, the population is exposed to a multitude of different substances, designated as mixtures. A body of literature on air pollutants indicated that the next step in air pollution research is investigating pollutant mixtures and their potential impacts on health, as a risk assessment of individual air pollutants may actually underestimate the overall risks. This review aims to synthesize the health effects related to air pollutant mixtures containing selected pollutants such as: volatile organic compounds, particulate matter, sulfur and nitrogen oxides. For this review, the PubMed database was used to search for articles published within the last decade, and we included studies assessing the associations between air pollutant mixtures and health effects. The literature search was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A number of 110 studies were included in the review from which data on pollutant mixtures, health effects, methods used, and primary results were extracted. Our review emphasized that there are a relatively small number of studies addressing the health effects of air pollutants as mixtures and there is a gap in knowledge regarding the health effects associated with these mixtures. Studying the health effects of air pollutant mixtures is challenging due to the complexity of components that mixtures may contain, and the possible interactions these different components may have.

Combined pollution of heavy metals and polycyclic aromatic hydrocarbons in the soil in Shenfu Region, China: a case of three different cities

It is a challenging issue to investigate the combined pollution of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in urban soils. The purpose of this study was to determine the concentrations of these two pollutants in soils in Shenyang, Fushun, and Fushun New District, to analyze their distribution, their interaction, and co-contamination levels. The concentrations of heavy metals were measured by inductively coupled plasma mass spectrometry (ICP-MS), while the concentrations of 21 kinds of PAH were analyzed by gas chromatography-mass spectrometry (GC-MS). Based on the analysis of pollution concentrations and distribution patterns, the intrinsic links between heavy metals and PAHs in three different cities were assessed using a variety of multivariate analysis methods. Compared to Shenfu New District, the concentration of pollutants in Shenyang and Fushun shows a higher level. Moreover, the results of redundancy analysis (RDA) of samples may quantify the possibility of combined pollution of different heavy metal elements and PAHs. This study also affirms the important role of multivariate analysis in being used to reveal the complex interactions and spatial distribution of different pollutants.

Bioremediation of PAHs and heavy metals co-contaminated soils: Challenges and enhancement strategies

Systemic studies on the bioremediation of co-contaminated PAHs and heavy metals are lacking, and this paper provides an in-depth review on the topic. The released sources and transport of co-contaminated PAHs and heavy metals, including their co-occurrence through formation of cation-π interactions and their adsorption in soil are examined. Moreover, it is investigated that co-contamination of PAHs and heavy metals can drive a synergistic positive influence on bioremediation through enhanced secretion of extracellular polymeric substances (EPSs), production of biosynthetic genes, organic acid and enzymatic proliferation. However, PAHs molecular structure, PAHs-heavy metals bioavailability and their interactive cytotoxic effects on microorganisms can exert a challenging influence on the bioremediation under co-contaminated conditions. The fluctuations in bioavailability for microorganisms are associated with soil properties, chemical coordinative interactions, and biological activities under the co-contaminated PAHs-heavy metals conditions. The interactive cytotoxicity caused by the emergence of co-contaminants includes microbial cell disruption, denaturation of DNA and protein structure, and deregulation of antioxidant biological molecules. Finally, this paper presents the emerging strategies to overcome the bioavailability problems and recommends the use of biostimulation and bioaugmentation along with the microbial immobilization for enhanced bioremediation of PAHs-heavy metals co-contaminated sites. Better knowledge of the bioremediation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of PAHs and heavy metals co-contamination in the near future.