Content of PAHs in soil of a hazel orchard depending on the method of weed control

Fluorene-induced stress in the benthic oligochaete Tubifex tubifex: A multi-biomarker assessment of toxicological pathways and mechanisms under acute and subchronic exposures

This study examined the multifaceted impacts of fluorene exposure on Tubifex tubifex, encompassing acute (survival analysis and behavioral responses) and subchronic exposure regimens (antioxidant enzyme response and histopathology), molecular docking studies, and generalized read-across analysis. Survival analysis revealed concentration-dependent increases in toxicity over varying time intervals, with LC50 values decreasing from 30.072 mg/L at 24 h to 12.365 mg/L at 96 h, emphasizing the time-sensitive and concentration-responsive nature of the stressor. Behavioral responses were both concentration- and duration-dependent. While Erratic Movement and Clumping Tendency exhibited earlier responses (within 24 h) at lower concentrations, the wrinkling effect and mucus secretion) exhibited delayed onset, suggesting intricate regulatory mechanisms underlying adaptability to environmental challenges; moreover, the wrinkling effect was consistently induced at higher concentrations, indicating greater sensitivity to the toxic effects of fluorene. With sublethal environmentally relevant concentrations-1.24 mg/l and 2.47 mg/L i.e., 10% and 20% 96 h, respectively-the antioxidant enzyme response (i.e., upregulation of SOD, CAT, and GST) with increasing fluorene concentration, revealing a nonlinear, hormetic response, suggested adaptive protection at lower doses but inhibition at higher concentrations. Histopathological examination indicated that higher fluorene concentrations caused cellular proliferation, inflammation, and severe tissue damage in the digestive tract and body wall. Molecular docking studies demonstrated robust interactions between fluorene and major stress biomarker enzymes, disrupting their functions and inducing oxidative stress. Interactions with cytochrome c oxidase suggested interference with cellular energy production. Generalized Read-Across (GenRA) analysis unveiled shared toxicity mechanisms among fluorene and its analogs, involving the formation of reactive epoxides and the influence of cytochrome P450 enzymes. The diverse functional groups of these analogs, particularly chlorine-containing compounds, were implicated in toxicity through lipid peroxidation and membrane damage. Adverse outcome pathways and broader consequences for aquatic ecosystem health are discussed.

The Effect of Spring Barley Fertilization on the Content of Polycyclic Aromatic Hydrocarbons, Microbial Counts and Enzymatic Activity in Soil

Soil-dwelling microorganisms play an important role in the environment by decomposing organic matter, degrading toxic compounds and participating in the nutrient cycle. The microbiological properties of soil are determined mainly by the soil pH, granulometric composition, temperature and organic carbon content. In agricultural soils, these parameters are modified by agronomic operations, in particular fertilization. Soil enzymes participate in nutrient cycling and they are regarded as sensitive indicators of microbial activity and changes in the soil environment. The aim of the present study was to determine whether PAH content in soil is associated with the microbial activity and biochemical properties of soil during the growing season of spring barley treated with manure and mineral fertilizers. Soil samples for analysis were collected on four dates in 2015 from a long-term field experiment established in 1986 in Bałcyny near Ostróda (Poland). The total content of PAHs was lowest in August (194.8 µg kg^-1) and highest in May (484.6 µg kg^-1), whereas the concentrations of heavier weight PAHs was highest in September (158.3 µg kg^-1). The study demonstrated that weather conditions and microbial activity induced considerable seasonal variations in PAHs content. Manure increased the content of organic carbon and total nitrogen, the abundance of organotrophic, ammonifying and nitrogen-fixing bacteria, actinobacteria and fungi and enhanced the activity of soil enzymes, including dehydrogenases, catalase, urease, acid phosphatase and alkaline phosphatase.

The Influence of Crops on the Content of Polycyclic Aromatic Hydrocarbons in Soil Fertilized with Manure and Mineral Fertilizers

Polycyclic aromatic hydrocarbons (PAHs) are mainly accumulated in soil. Plants secrete enzymes that transform or biodegrade PAHs in soil. Some plant species are more effective in stimulating the biodegradation of these pollutants than other species. This study was undertaken to evaluate the influence of crop rotation on PAH concentrations in soil. Four crops were grown in rotation: sugar beets, spring barley, maize, and spring wheat. Soil samples for the study were obtained from a long-term field experiment established in 1986 in Bałcyny, Poland. The concentrations of PAHs were analyzed in soil samples gathered over a period of 12 years (1998-2009). An attempt was made to evaluate the effect of crop rotation (sugar beets, spring barley, maize, and spring wheat) on PAH concentrations in soil. The content of PAHs in soil samples was measured by gas chromatography with flame ionization detection. Data were processed statistically by repeated measures ANOVA. The concentrations of ∑16 PAHs were lowest in soil after sugar beet cultivation, and highest in soil after maize cultivation. It can be concluded that maize was the plant with the greatest adverse effect on the content of heavy PAH in the soil, a completely different effect can be attributed to spring wheat, which has always been shown to reduce the content of heavy PAH in the soil. Weather conditions affected PAHs levels in soil, and PAH content was highest in soil samples collected in a year with the driest growing season. This arrangement suggests a greater influence of weather conditions than of the cultivated plant.

Mulching as a Sustainable Water and Soil Saving Practice in Agriculture: A Review

This research was carried out in order to demonstrate that mulching the ground helps to conserve water, because agricultural sustainability in dryland contexts is threatened by drought, heat stress, and the injudicious use of scarce water during the cropping season by minimizing surface evaporation. Improving soil moisture conservation is an ongoing priority in crop outputs where water resources are restricted and controlled. One of the reasons for the desire to use less water in agriculture is the rising demand brought on by the world’s growing population. In this study, the use of organic or biodegradable mulches was dominated by organic materials, while inorganic mulches are mostly comprised of plastic-based components. Plastic film, crop straw, gravel, volcanic ash, rock pieces, sand, concrete, paper pellets, and livestock manures are among the materials put on the soil surface. Mulching has several essential applications, including reducing soil water loss and soil erosion, enriching soil fauna, and improving soil properties and nutrient cycling in the soil. It also reduces the pH of the soil, which improves nutrient availability. Mulching reduces soil deterioration by limiting runoff and soil loss, and it increases soil water availability by reducing evaporation, managing soil temperature, or reducing crop irrigation requirements. This review paper extensively discusses the benefits of organic or synthetic mulches for crop production, as well as the uses of mulching in soil and water conservation. As a result, it is very important for farmers to choose mulching rather than synthetic applications.

The potential risks and exposure of Qinling giant pandas to polycyclic aromatic hydrocarbon (PAH) pollution

Rapid industrialization and urbanization have created a substantial urban-rural gradient for various pollutants. The Qinling Mountains are highly important in terms of biodiversity, providing habitat for giant pandas, which are endemic to China and are a widely recognized symbol for conservation. Whether polycyclic aromatic hydrocarbon (PAH) exposure risks regarding in situ animal conservation zones are affected by environmental pollution or even enhanced by the mountain-trapping effect requires further research. Our group carried out a large-scale investigation on the area ranging from Xi'an to Hanzhong across the giant panda habitat in the Qinling Mountains by collecting atmosphere, soil, bamboo, and fecal samples from different sites over a two-year period. The total toxicity of atmospheric PAHs and the frequencies of soil PAHs above effect range low (ERL) values showed a decreasing trend from urban areas to the central mountains, suggesting a distance effect from the city. The proportions of total 5- and 6-ring PAHs in the atmosphere were higher in the central mountainous areas than in the urban areas, while this difference was reversed in the soil. Health risk assessments showed that the incremental lifetime carcinogenic risks (ILCR) of PAH exposure by bamboo ingestion ranged from 2.16 × 10^-4 to 3.11 × 10^-4, above the critical level of 10^-4. Bamboo ingestion was the main driver of the PAH exposure risks. The concentration difference between bamboo and fecal samples provided a reference for the level of PAHs absorbed by the panda digestive system. Since the Qinling Mountains possess the highest density of giant pandas and provide habitats to many other endangered animal and plant species, we should not ignore the probability of health risks posed by PAHs. Monitoring the pollution level and reducing the atmospheric emissions of toxic pollutants are recommended actions. Further detailed research should also be implemented on pandas' health effects of contaminant exposure.

Phylogenetic analysis of hyperaccumulator plant species for heavy metals and polycyclic aromatic hydrocarbons

Increasing concentration of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) in the soil may impose a serious threat to living organisms due to their toxicity and the ability to accumulate in plant tissues. The present review focuses on the phylogenetic relationships, sources, biotransformation and accumulation potential of hyperaccumulators for the priority HMs and PAHs. This review provides an opportunity to reveal the role of hyperaccumulators in removal of HMs and PAHs from soils, to understand the relationships between pollutants and their influence on the environment and to find potential plant species for soil remediation. The phylogenetic analysis results showed that the hyperaccumulators of some chemicals (Co, Cu, Mn, Ni, Zn, Cd) are clustered on the evolutionary tree and that the ability to hyperaccumulate different pollutants can be correlated either positively (Cd-Zn, Pb-Zn, Co-Cu, Cd-Pb) or negatively (Cu-PAHs, Co-Cd, Co-PAHs, Ni-PAHs, Cu-Ni, Mn-PAHs). Further research needs to be extended on the focus of commercializing the techniques including the native hyperaccumulators to remediate the highly contaminated soils.

Effect of manure and mineral fertilisers on the content of light and heavy polycyclic aromatic hydrocarbons in soil

A study was conducted to explore the effects of fertilisation with farmyard manure (FYM) and mineral fertilisers on the content of PAHs in soil. The analyses were made on soil samples (collected in 1998–2009) from a long-term field experiment set up in 1986 in Bałcyny near Ostróda. The content of light and heavy polycyclic aromatic hydrocarbons was determined on a gas chromatograph coupled with an FID detector. The analytical data were processed statistically according to an analysis of variance with repeated measurements. The content of light and heavy polycyclic aromatic hydrocarbons was significantly higher in soil fertilised with FYM than in soil nourished only with mineral fertilisers. The effect of increasing doses of potassium on total light PAHs in soil depended on a fertilisation system – there was either a distinct decrease in soil fertilised with mineral substances alone or a slight increase in soil fertilised with manure. Regular soil liming significantly raised the ∑ of heavy PAHs in soil treated with manure but significantly decreased it in soil supplied only mineral fertilisers.

Impact factor assessment of the uptake and accumulation of polycyclic aromatic hydrocarbons by plant leaves: Morphological characteristics have the greatest impact

Polycyclic aromatic hydrocarbons (PAHs) have toxic, teratogenic, mutagenic and carcinogenic effects on living organisms. Plants can function as pollutant bioindicators and bioaccumulators due to their wide surface distribution and specific responses to atmospheric pollutants. However, various plants exhibit significant differences in their capacities to accumulate PAHs. At present, research has mainly focused on the effects of leaf morphology and physiological characteristics, and few studies have evaluated the effects of the leaf surface on PAH accumulation. We aimed to assess the factors impacting the uptake and accumulation of PAHs by leaves. We selected 8 common tree species in Shanghai, China, and used supercritical fluid extraction technology to determine the content of PAHs in their leaves. Specific measurements of leaf area, width/length, wax content, and stomatal density were applied to index the morphological and physiological characteristics; surface roughness, surface free energy, polar components, and dispersion components were compiled into an adsorption performance index. Principal component analysis (PCA) and canonical correlation analysis (CCA) were used to assess the effects of different leaf characteristics on PAH accumulation. We found that the mean concentrations of ΣPAHs ranged from 300 to 2000 ng·g^-1 and that the proportions of different benzene rings were significantly different among the different tree species. Leaf morphology and physiological characteristics had more significant effects compared to surface adsorption. CCA showed a significant negative correlation between leaf morphological characteristics and wax content, but had no significant correlation with surface adsorption. Low-molecular-weight PAHs were found to be mainly affected by the morphological characteristics, while medium- and high-molecular-weight PAHs were influenced by wax content and adsorption. Our conclusions provide a theoretical basis for the establishment of a reliable plant atmosphere-monitoring system and a method for screening tree species with strong PAH adsorption capacity.