Sedimentary records of polycyclic aromatic hydrocarbons from three enclosed lakes in China: Response to energy structure and economic development

Interactions between phenanthrene exposure and historical chemical stress: Implications for fitness and ecological resilience of the sentinel species Daphnia magna

Polycyclic aromatic hydrocarbons (PAHs) arise from incomplete combustion of oil, coal, and gasoline, with lipophilic properties facilitating their widespread distribution and persistence. Due to their biochemical attributes, PAHs can accumulate in animal tissues, potentially causing mutagenic and carcinogenic effects. Since the industrial revolution, PAH concentrations in the environment have risen, with lakes showing levels from 0.159 to 33,090 μg/kg sediment. Despite acute toxicity studies showing adverse effects on freshwater organisms, the long-term impacts and synergistic interactions with other pollutants remain largely unexplored. This study investigates the impact of phenanthrene (PHE), a prominent PAH found in aquatic environments, on Daphnia magna, a species of significant ecological importance in freshwater ecosystems globally, being both a sentinel species for chemical pollution and a keystone organism in freshwater aquatic ecosystems. Leveraging the dormancy of D. magna, which spans decades or even centuries, we exposed strains with diverse histories of chemical contaminant exposure to environmentally relevant concentrations of PHE. Initially, acute exposure experiments were conducted in accordance with OECD guidelines across 16 Daphnia strains, revealing substantial variation in acute toxic responses, with strains naïve to chemical pollutants showing the lowest toxicity. Utilizing the median effect concentration EC10 derived from acute exposures, we assessed the impacts of chronic PHE exposure on life history traits and ecological endpoints of the 16 strains. To elucidate how historical exposure to other environmental stressors may modulate the toxicity of PHE, temporal populations of D. magna resurrected from a lake with a well-documented century-spanning history of environmental impact were utilized. Our findings demonstrate that PHE exposure induces developmental failure, delays sexual maturation, and reduces adult size in Daphnia. Populations of Daphnia historically exposed to chemical stress exhibited significantly greater fitness impacts compared to naïve populations. This study provides crucial insights into the augmented effects of PAHs interacting with other environmental stressors.

Polycyclic aromatic hydrocarbon (PAH) phytoaccumulation in urban areas by Platanus × acerifolia, Celtis australis, and Tilia grandifolia leaves and branches

Polycyclic aromatic hydrocarbon (PAH) concentrations in the leaves and 1-year-old branches of three common tree species growing in a middle-sized city located in a moderate climate zone were estimated. For this purpose, PAH phytoaccumulation in Platanus × acerifolia, Celtis australis, and Tilia grandifolia species from highly urbanized, traffic congested, and highly PAH-contaminated streets was compared with trees from non-contaminated parks in the same urban core. The gathered data was used to define 17 PAH profiles, identify the main PAH pollution emission sources, and determine the organ and species specificity of PAHs accumulation. Due to the direct absorption of polluted air via stomata, the leaves accumulated up to 30% more PAHs compared to the 1-year-old branches. As expected, PAH concentrations were much higher in street trees, while heavy weight PAHs (with five and six rings) were accumulated in the highest concentrations. The highest foliar Σ17 PAH concentrations were detected in street-grown C. australis, followed by P. acerifolia and T. grandifolia (502.68, 488.45, and 339.47 ng g-1 dry weight (DW), respectively). The same pattern was noted for Σ17 PAHs in branches (414.89, 327.58, and 342.99 ng g-1 DW, respectively). Thus, T. grandifolia emerged as the least effective PAH sink as it accumulated up to ~ 40% less PAHs than P. acerifolia and C. australis leaves/branches. Among the 17 tracked PAHs, benzo[a]anthracene, benzo[a]pyrene, dibenzo[a,h]anthracene, and pyrene were found to have accumulated in the highest concentrations in all analyzed species irrespective of the site, and accounted for more than 50% of the total detected PAHs. Finally, a "black box" about species and organ specificity, as well as specific drivers that limit PAHs uptake capacity by trees, was opened, while this work provides insights into further PAH phytoremediation strategies.

Distribution, sources, partition behavior and risk assessment of polycyclic aromatic hydrocarbons (PAHs) in the waters and sediments of Lake Ulansuhai, China

This study represents the first comprehensive investigation of 16 polycyclic aromatic hydrocarbons (PAHs) in the waters and sediments of Lake Ulansuhai. It explores their occurrence, sources, transport behavior, and associated risks to human health and ecosystems. The results revealed that concentrations of ∑PAHs in dissolved phase and sediment with no significant seasonal differences. In contrast, ∑PAHs concentrations in suspended particulate matter were significantly higher during the ice-free period compared to the ice period. Spatially, the northern part of Lake Ulansuhai displayed higher PAHs content. Diagnostic isomeric ratios and PMF models indicated that the PAHs were primarily derived from combustion sources. The distribution of PAHs within water-sediment demonstrated that non-equilibrium status. Fugacity calculations indicated that 2-4 rings PAHs acted as secondary sources of sediment emissions. Toxicity assessment, indicated that PAHs posed no significant carcinogenic risk to humans. Risk quotient values showed that PAHs as low to high ecological risk.

The remediation of marine sediments containing polycyclic aromatic hydrocarbons by peroxymonosulfate activated with Sphagnum moss-derived biochar and its benthic microbial ecology

This research was to study the efficiency of Sphagnum moss-derived biochar (SMBC) in removing polycyclic aromatic hydrocarbons (PAHs) from marine sediment using a peroxymonosulfate (PMS)-based carbon-advanced oxidation process (PMS-CAOPs). Sphagnum moss-derived biochar (SMBC) was generated via a simple thermochemical process for PMS activation toward enhancing decontamination of sediments. At pH 6, the SMBC/PMS system achieved a PAH removal efficiency exceeding 78% in 12 h reaction time. Moreover, PAHs of 6-, 5-, 4-, 3-, and 2-ring structures exhibited 98%, 74%, 68%, 85%, and 91%, of removal, respectively. The SMBC activation of PMS generated both radicals (SO4•- and HO•) and nonradical (1O2), species responsible for PAHs degradation, attributed primarily to inherent iron and carbon moieties. The significant PAHs degradation efficiency showcased by the SMBC/PMS process holds promise for augmenting the performance of indigenous benthic microbial activity in sediment treatment contexts. The response of sediment microbial communities to PAH-induced stress was particularly associated with the Proteobacteria phylum, specifically the Sulfurovum genus. The findings of the present study highlight the efficacy of environmentally benign reactive radical/nonradical-based PMS-CAOP using pristine carbon materials, offering a sustainable strategy for sediment treatment.

Insight into the effect mechanism of sedimentary record of polycyclic aromatic hydrocarbon: Isotopic evidence for lake organic matter deposition and regional development model

Deciphering the temporal patterns of polycyclic aromatic hydrocarbons (PAHs) in sediment cores, and the effect mechanism of sedimentary organic matter (OM) and regional development model on PAHs are crucial for pollution control and environmental management. Herein, sediment core was collected from Chenhu international wetland in Wuhan, central China. Meanwhile, historical trend and source of PAHs and sedimentary OM were presented, respectively. Result demonstrated that the most significant growth of PAHs (increased by 158.8%) was attributed to the significant enhancement of traffic emission (5.57 times), coal combustion (4.59 times), and biomass burning (8.09 times). Similarly, the percentage of phytoplankton (stage Ⅲ: 37.9%; stage Ⅳ: 31.2%) and terrestrial C3 plants (stage Ⅲ: 24.6%; stage Ⅳ: 29.2%) to sedimentary OM hold the dominant position after the stage Ⅱ. The obvious shifts of historical trend and sources in PAHs were highly related to economic development models (r = 0.72, p < 0.001) and sedimentary OM (r = 0.82, p < 0.001). It demonstrated that eutrophication of lake accelerated the burial of PAHs. Redundancy analysis results suggested that TOC was dominating driver of sedimentary PAHs (16.56%) and phytoplankton occupied 9.58%. To further confirm the significant role of economic development models, three different historical trends of PAHs in different regions of China were presented. The result of this study provides the new insight into the geochemistry mechanism of lake sedimentary OM and PAHs. Meanwhile, the relationship of regional development model and sedimentary PAHs was highlighted in this study. Significantly, the main environmental implications of this study are as follows: (1) lake eutrophication of phytoplankton OM accelerated the burial of PAHs in lake sediment; (2) economic development models and energy structure significantly influence the sedimentary PAHs. This study highlights the coupling relationship between OM burial and PAHs sedimentation, and the importance of accelerating the transformation of economic energy structure.

Sediment core records and impact factors of polycyclic aromatic hydrocarbons in Chinese lakes

Lake sediment is a natural sink for polycyclic aromatic hydrocarbons (PAHs). PAH sedimentation characteristics and their impact factors of Chinese lakes have mainly been qualitative assessed. However, quantitative impacts of PAH sedimentation from different factors have not been well analyzed. To fill this gap, we screened PAH sedimentation records from the literature, for 51 lakes in China and other regions of the world, to identify historical concentration variation and the impact factors of PAHs in different regions, in lake sediment. The results show that PAH concentrations in the sediment core in the selected Chinese lakes (478 ± 812 ng/g dry weight (dw)) were significantly lower than those in North America (5518 ± 6572 ng/g dw) and Europe (3817 ± 4033 ng/g dw). From 1900 to 2015, most of the lakes in China showed an increasing trend of PAH sedimentation concentrations, with the lakes in Southeastern China showed a decreasing trend of PAH concentration in the period of 2001-2015, which was later than the peak times shown in Western countries (1941-1970). The 2-3-ring PAHs were the main components in the sediment core of Chinese lakes, but the proportion to the total PAHs decreased from 72% in 1900-1940 to 55% in 2001-2015. Generalized additive modeling (GAM) was adopted to simulate the associations between PAH sedimentation records and the impact factors. There are large regional variations of economic and industrial development in China. The impact factors of PAH accumulation in the lake sediments differ in different regions. However, population and the consumption of coal, pesticides, and fertilizer were identified to be the most important impact factors influencing PAH sedimentation. The Chinese government needs to strengthen control measures on pollutant discharge to reduce the anthropogenic impact of PAH sedimentation in lakes.