Comparison of PAHs uptake by selected Monocotyledones and Dicotyledones from municipal and industrial sewage sludge

Phenanthrene-Induced Cytochrome P450 Genes and Phenanthrene Tolerance Associated with Arabidopsis thaliana CYP75B1 Gene

Polycyclic aromatic hydrocarbons (PAHs) form an important group of organic pollutants due to their distribution in the environment and their carcinogenic and/or mutagenic effects. In order to identify at the molecular level some of the players in the biodegradation and tolerance response to PAHs in plants, we have phenotyped 32 Arabidopsis thaliana T-DNA mutant lines corresponding to 16 cytochrome P450 (CYP) genes that showed to be differentially expressed under contrasted stress conditions induced by phenanthrene, a 3-ring PAH. This screening has allowed us to identify CYP75B1 (At5g07990) T-DNA mutants as the only ones being sensitive to phenanthrene-induced stress, supporting that CYP75B1 protein is necessary for PAH tolerance. CYP75B1 codes for a 3'flavonol hydroxylase. CYP75B1 gene was heterologously expressed on yeast in order to investigate whether it affects the A. thaliana response to phenanthrene by participating in its metabolization. Heterologously-produced CYP75B1 enzyme shows to be catalytically efficient against its physiological substrates (e.g., naringenin) but unable to metabolize phenanthrene or 9-phenanthrenol. In contrast, CYP75B1 seems rather involved in phenanthrene tolerance as a crucial element by regulating concentration of antioxidants through the production of 3'-hydroxylated flavonoids such as quercetin and cyanidin. In particular, we report a highly increased generation of reactive oxygen species (H2O2 and singlet oxygen) in cyp75b1 mutants compared to control plants in response to phenanthrene treatment. Overall, CYP75B1 shows to play an important role in the response to the deleterious effects of phenanthrene exposure and this is related to oxidative stress sensitivity rather than metabolization.

Persistent polycyclic aromatic hydrocarbons removal from sewage sludge-amended soil through phytoremediation combined with solid-state ligninolytic fungal cultures

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment, causing increasing concern because of their impact on soil health, food safety and potential health risks. Four bioremediation strategies were examined to assess the dissipation of PAHs in agricultural soil amended with sewage sludge over a period of 120 days: soil-sludge natural attenuation (SS); phytoremediation using maize (Zea mays L.) (PSS); mycoremediation (MR) separately using three white-rot fungi (Pleurotus ostreatus, Phanerochaete chrysosporium and Irpex lacteus); and plant-assisted mycoremediation (PMR) using a combination of maize and fungi. In the time frame of the experiment, mycoremediation using P. chrysosporium (MR-PH) exhibited a significantly higher (P < 0.05) degradation of total PAHs compared to the SS and PSS treatments, achieving a degradation rate of 52 %. Both the SS and PSS treatments demonstrated a lower degradation rate of total PAHs, with removal rates of 18 % and 32 %, respectively. The PMR treatments showed the highest removal rates of total PAHs at the end of the study, with degradation rates of 48-60 %. In the shoots of maize, only low- and medium-molecular-weight PAHs were found in both the PSS and PMR treatments. The calculated translocation and bioconversion factors always showed values < 1. The analysed enzymatic activities were higher in the PMR treatments compared to other treatments, which can be positively related to the higher degradation of PAHs in the soil.

Transfer and Degradation of PAHs in the Soil-Plant System: A Review

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, persistent organic pollutants that threaten ecosystems and human health. Consistent monitoring is essential to minimize the entry of PAHs into plants and reduce food chain contamination. PAHs infiltrate plants through multiple pathways, causing detrimental effects and triggering diverse plant responses, ultimately increasing either toxicity or tolerance. Primary plant detoxification processes include enzymatic transformation, conjugation, and accumulation of contaminants in cell walls/vacuoles. Plants also play a crucial role in stimulating microbial PAHs degradation by producing root exudates, enhancing bioavailability, supplying nutrients, and promoting soil microbial diversity and activity. Thus, synergistic plant-microbe interactions efficiently decrease PAHs uptake by plants and, thereby, their accumulation along the food chain. This review highlights PAHs uptake pathways and their overall fate as contaminants of emerging concern (CEC). Understanding plant uptake mechanisms, responses to contaminants, and interactions with rhizosphere microbiota is vital for addressing PAH pollution in soil and ensuring food safety and quality.

Potential ability of tobacco (Nicotiana tabacum L.) to phytomanage an urban brownfield soil

The ability of tobacco (Nicotiana tabacum L. cv. Badischer Geudertheimer) for phytomanaging and remediating soil ecological functions at a contaminated site was assessed with a potted soil series made by fading an uncontaminated sandy soil with a contaminated sandy soil from the Borifer brownfield site, Bordeaux, SW France, at the 0%, 25%, 50%, 75%, and 100% addition rates. Activities of sandblasting and painting with metal-based paints occurred for decades at this urban brownfield, polluting the soil with metal(loid)s and organic contaminants, e.g., polycyclic aromatic hydrocarbons, in addition to past backfilling. Total topsoil metal(loid)s (e.g., 54,700 mg Zn and 5060 mg Cu kg-1) exceeded by seven- to tenfold the background values for French sandy soils, but the soil pH was 7.9, and overall, the 1M NH4NO3 extractable soil fractions of metals were relatively low. Leaf area, water content of shoots, and total chlorophyll (Chl) progressively decreased with the soil contamination, but the Chl fluorescence remained constant near its optimum value. Foliar Cu and Zn concentrations varied from 17.8 ± 4.2 (0%) to 27 ± 5 mg Cu kg-1 (100%) and from 60 ± 15 (0%) to 454 ± 53 mg Zn kg-1 (100%), respectively. Foliar Cd concentration peaked up to 1.74 ± 0.09 mg Cd kg-1, and its bioconcentration factor had the highest value (0.2) among those of the metal(loid)s. Few nutrient concentrations in the aboveground plant parts decreased with the soil contamination, e.g., foliar P concentration from 5972 ± 1026 (0%) to 2861 ± 334 mg kg-1 (100%). Vulnerability to drought-induced embolism (P50) did not differ for the tobacco stems across the soil series, whereas their hydraulic efficiency (Ks) declined significantly with increasing soil contamination. Overall, this tobacco cultivar grew relatively well even in the Borifer soil (100%), keeping its photosynthetic system healthy under stress, and contaminant exposure did not increase the vulnerability of the vascular system to drought. This tobacco had a relevant potential to annually phytoextract a part of the bioavailable soil Zn and Cd, i.e., shoot removals representing here 8.8% for Zn and 43.3% for Cd of their 1M NH4NO3 extractable amount in the potted Borifer soil.

Soil PAHs contamination effect on the cellular and subcellular organelle changes of Phragmites australis Cav

The concentrations of ∑₁₆ priority polycyclic aromatic hydrocarbons (PAHs) for soils, roots, and above-ground parts of reed (Phragmites australis Cav.) were determined on different monitoring plots located near the city of Kamensk-Shakhtinsky, southern Russia, where historically received industrial sewage and sludge. The total PAHs concentration in monitoring soil plots was significantly higher than those in the background site which situated at the distance of 2 km from the contamination source. Accordingly, the maximum accumulation was found for phenanthrene and chrysene among the 16 priority PAHs in most of the plant samples collected in the impact zone. The effects of PAHs' pollution on changes of Phragmites australis Cav. cellular and subcellular organelles in the studied monitoring sites were also determined using optical and electron microscopy, respectively. The obtained data showed that increasing of PAHs contamination negatively affected the ultrastructural changes of the studied plants. Phragmites australis Cav. showed a high level of adaptation to the effect of stressors by using tissue and cell levels. In general, the detected alterations under the PAHs effect were possibly connected to changes in biochemical and histochemical parameters as a response for reactive oxygen species and as a protective response against oxidative stress. The obtained results introduce innovative findings of cellular and subcellular changes in plants exposed to ∑₁₆ priority PAHs as very persistent and toxic contaminants.

Dissipation of polycyclic aromatic hydrocarbons (PAHs) in soil amended with sewage sludge and sludge compost

In this study, greenhouse experiments were conducted under the condition of different amendment ratios and planting tall fescue (Festuca arundinacea). The amendment ratios of sewage sludge or sludge compost to soil were of 0, 10, 25, and 50% (w/w). The removal rates of PAH, catalase, and dehydrogenase activities of amended soil and accumulation of PAHs by vegetation were detected to investigate the differences of PAH dissipation in sludge-amended and compost-amended soils. The initial PAH concentrations in three amended soils increased with the more addition of sludge or compost. After 126-day experiment, maximum PAH removal rates were observed in sludge-amended and compost-amended soils with PAH concentration of about 200 μg kg^-1. And the removal of PAHs showed better efficiencies in compost soil rather than in sludge soil. The more catalase activity and dehydrogenase activity of soil were obtained, respectively, in sludge soil and compost soil. The results indicated that the mechanism of PAH dissipation in two types of amended soils were different. The abundant amount of microorganism dominated PAH dissipation in sludge soils, and PAHs dissipated mainly caused of intense activity of microorganism in compost soils. In addition, PAH accumulation in tall fescue suggested that the transference approach of PAHs was from soil to the roots, and then accumulated in the shoots of tall fescue. It was prone to store up more PAHs in vegetation in the condition of high molar weight of PAHs, more biomass of vegetation, and heavy PAH concentration in soil.

Ecological risk assessment for land contaminated by petrochemical industry

Contamination with harmful chemical substances, including organic compounds of the BTEX and PAH groups, constitutes one of the major threats to the functioning of soil habitat. Excessive contents of the above substances can exert adverse effects on soil organisms, reduce biodiversity, and thus deteriorate soil quality. The threat to soil ecosystems within areas particularly exposed to contamination with accumulating chemical compounds was assessed using the Ecological Risk Assessment (ERA) with a multi-stage Triad (triage rapid initial assessment) procedure (taking into account the different lines of evidence). The article presents the results of chemical and ecotoxicological study of soils sampled at sites affected by contamination from petrochemical industry. The study results provided foundations for developing the site specific ERA framework for the area examined.

Plant uptake and translocation of contaminants of emerging concern in soil

The advent of industrialization has led to the discovery of a wide range of chemicals designed for multiple uses including plant protection. However, after use, most of the chemicals and their derivatives end up in soil and water, interacting with living organisms. Plants, which are primary producers, are intentionally or unintentionally exposed to several chemicals, serving as a vehicle for the transfer of products into the food chain. Although the exposure of pesticides towards plants has been witnessed over a long time in agricultural production, other chemicals have attracted attention very recently. In this review, we carried out a comprehensive overview of the plant uptake capacity of various contaminants of emerging concern (CEC) in soil, such as pesticides, polycyclic aromatic hydrocarbons, perfluorinated compounds, pharmaceutical and personal care products, and engineered nanomaterials. The uptake pathways and overall impacts of these chemicals are highlighted. According to the literature, bioaccumulation of CEC in the root part is higher than in aerial parts. Furthermore, various factors such as plant species, pollutant type, and microbial interactions influence the overall uptake. Lastly, environmental factors such as soil erosion and temperature can also affect the CEC bioavailability towards plants.

Comparison of moss and pine needles as bioindicators of transboundary polycyclic aromatic hydrocarbon pollution in central Japan

Atmospheric pollution by polycyclic aromatic hydrocarbons (PAHs) has become a serious problem, especially in Asia, as PAHs can severely affect ecologically important mountainous areas. Using pine needles and mosses as bio-indicators, this study examined PAH pollution in a mountainous study area and evaluated the influence of transboundary PAHs. PAHs in urban areas were also evaluated for comparison. The study sites were alpine areas and urban areas (inland or coastal cities) across central Japan, in the easternmost part of Asia where atmospheric pollutants are transported from mainland Asia. The mean PAH concentrations of pine needles and mosses were 198.9 ± 184.2 ng g^-1 dry weight (dw) and 131.8 ± 60.7 ng g^-1 dw (mean ± SD), respectively. Pine needles preferentially accumulated PAHs with low molecular weights (LMW PAHs) and exhibited large differences in both PAH concentration and isomer ratios between alpine and urban sites. These differences can be explained by the strong influence of LMW PAHs emitted from domestic sources, which decreased and changed during transport from urban to alpine sites due to dry/wet deposition and photodegradation. In contrast, mosses accumulated a higher ratio of PAHs with high molecular weight (HMW PAHs). A comparison of isomer ratios showed that the PAH source for alpine moss was similar to that for northern coastal cities, which are typically influenced by long-transported PAHs from East Asia. Thus, these results indicate that alpine moss can also be strongly affected by the transboundary PAHs. It is likely that the uptake characteristics of moss, alpine climate, and alpine locations far from urban areas can strengthen the influence of transboundary pollution. Based on these results, the limitations and most effective use of bioindicators of PAH pollution for preserving alpine ecosystems are discussed.