Pot experiments were conducted to evaluate plant contribution during remediation of the polycyclic aromatic hydrocarbons (PAH)-contaminated soil of Dagang Oilfield by Fire Phoenix (a mixture of Festuca L.). The results showed that Fire Phoenix could grow in soil contaminated by high and low concentrations of PAHs. After being planted for 150 days, the total removal rate of six PAHs in the high and low PAH concentrations was 80.36% and 79.79%, significantly higher than the 58.79% and 53.29% of the unplanted control group, respectively. Thus, Fire Phoenix can effectively repair the soil contaminated by different concentrations of PAHs. In high concentrations of PAHs, the results indicated a positive linear relationship between PAH absorption in tissues of Fire Phoenix and the growth time in the early stage. In contrast, the contents of PAHs were just slightly increased in the late period of plant growth. The main factor for the dissipation of PAHs was plant-promoted biodegradation (99.04%–99.93%), suggesting a low contribution of PAH uptake and transformation (0.07%–0.96%). The results revealed that Fire Phoenix did not remove the PAHs in the soil by accumulation but promoted PAH dissipation in the soil by stimulating the microbial metabolism in the rhizosphere.

Mining activities generate spoils and effluents with extremely high metal concentrations of heavy metals that might have adverse effects on ecosystems and human health. Therefore, information on soil and plant metal concentrations is needed to assess the severity of the pollution and develop a strategy for soil reclamation such as phytoremediation. Here, we studied soils and vegetation in three heavily contaminated sites with potential toxic metals and metalloids (Zn, Pb, Cd, As, TI) in the mining district of Les Malines in the Languedoc region (southern France). Extremely high concentrations were found at different places such as the Les Aviniéres tailing basins (up to 160,000 mg kg–1 Zn, 90,000 mg kg–1 Pb, 9,700 mg kg–1 of As and 245 mg kg–1 of Tl) near a former furnace. Metal contamination extended several kilometres away from the mine sites probably because of the transport of toxic mining residues by wind and water. Spontaneous vegetation growing on the three mine sites was highly diversified and included 116 plant species. The vegetation cover consisted of species also found in non-contaminated soils, some of which have been shown to be metal-tolerant ecotypes (Festuca arvernensis, Koeleria vallesiana and Armeria arenaria) and several Zn, Cd and Tl hyperaccumulators such as Anthyllis vulneraria, Thlaspi caerulescens, Iberis intermedia and Silene latifolia. This latter species was highlighted as a new thallium hyperaccumulator, accumulating nearly 1,500 mg kg–1. These species represent a patrimonial interest for their potential use for the phytoremediation of toxic metal-polluted areas.

The extensive use of copper-bearing fungicides in vineyards is responsible for the accumulation of copper (Cu) in soils. Grass species able to accumulate Cu could be cultivated in the vineyard inter-rows for copper phytoextraction. In this study, the capacity of Festuca rubra cv Merlin and Sinapis alba to tolerate and accumulate copper (Cu) was first investigated in a hydroponic system without the interference of soil chemical–physical properties. After the amendment of Cu (5 or 10 mg Cu l⁻¹) to nutrient solution, shoot Cu concentration in F. rubra increased up to 108.63 mg Cu kg⁻¹DW, more than three times higher than in S. alba (31.56 mg Cu kg⁻¹DW). The relationship between Cu concentration in plants and external Cu was dose-dependent and species specific. Results obtained from the hydroponic experiment were confirmed by growing plants in pots containing soil collected from six Italian vineyards. The content of soil organic matter was crucial to enhance Cu tolerance and accumulation in the shoot tissues of both plant species. Although S. alba produced more biomass than F. rubra in most soils, F. rubra accumulated significantly more Cu (up to threefold to fourfold) in the shoots. Given these results, we recommended that F. rubra cv Merlin could be cultivated in the vineyard rows to reduce excess Cu in vineyard soils.

Two kinds of common turfgrass, fescue and ryegrass, were grown in soils amended with 20 x 80% sludge compost (SC) in this research. The effects of SC on two kinds of soil and response of fescue and ryegrass to the SC amendment were studied. The results showed that urease activity, extractable content of Cu and Zn and Electrical conductivity of both soils increased while pH decreased with the increase of SC amendment. However, the change of these parameters also depended strongly on soil characteristics. Sludge compost at the <=40 and <=60% levels can improve growth of fescue and ryegrass, respectively. The biomass of fescue grown in substrate with 40% SC increased 27% in a red soil and 44% in a yellow loamy soil compared to the control. The biomass of ryegrass grown in substrate with 60% SC increased 120% in the red soil and 86% in the yellow loamy soil. Sludge compost amendment at these levels did not significantly affect soluble salt contents of soil or Cu and Zn in plant tissue. Therefore, rational use of sludge compost can take advantage of its beneficial effect as a nutrient source for plant production while avoiding the potential deleterious effects on soil and plant.

Given the rising nitrous oxide (N₂O) concentration in the atmosphere, it has become increasingly important to identify hot spots and hot moments of N₂O emissions. With field measurements often failing to capture the spatiotemporal dynamics of N₂O emissions, estimating them with modeling tools has become an attractive alternative. Therefore, we incorporated several semi-empirical equations to estimate N₂O emissions with the Soil and Water Assessment Tool from nitrification and denitrification processes in soil. We then used the model to simulate soil moisture and the N₂O flux from grassland soils subjected to long-term grazing (> 60 years) at different intensities in Alberta, Canada. Sensitivity analysis showed that parameters controlling the N₂O flux from nitrification were most sensitive. On average, the accuracy of N₂O emission simulations were found to be satisfactory, as indicated by the selected goodness-of-fit statistics and predictive uncertainty band, while the model simulated the soil moisture with slightly higher accuracy. As expected, emissions were higher from the plots with greater grazing intensity. Scenario analysis showed that the N₂O emissions with the recommended fertilizer rate would dominate the emissions from the projected wetter and warmer future. The combined effects of fertilization and wetter and warmer climate scenarios would increase the current N₂O emission levels by more than sixfold, which would be comparable to current emission levels from agricultural soils in similar regions.

The effects of Fire Phoenix (a mixture of Festuca L.) and Purple coneflower (Echinacea purpurea (L.) Moench) on the remediation of two different high concentrations of PAH-contaminated soils were studied under the effect of strain N12 (Mycobacterium sp.), and the changes in rhizosphere enzymatic activity were preliminarily studied. The results of three culture stages (60 d, 120 d, and 150 d) showed that N12 has a promotional effect on the biomass of Fire Phoenix and E. purpurea, and the effect of N12 on the biomass of Fire Phoenix is better. Under the strengthening of N12, the maximum removal rates of Fire Phoenix reached 86.77% and 67.82% at two high PAH concentrations (A and B, respectively). The activity of dehydrogenase (DHO) is positively correlated with the degradation rate of PAHs at the A concentration (P < 0.05). The activity of DHO in soil will continue to increase at a higher level of the B concentration, but the positive correlation between the activity of DHO and the degradation rate of PAH is weakened. In the rhizosphere soil of the two plants, the change in polyphenol oxidase (PPO) activity with time has a significant negative correlation with the degradation rate of PAHs (P < 0.05). The experiment proved that Fire Phoenix is more suitable for the remediation of heavy PAH-contaminated soil under the condition of microorganism-strengthening, and it can achieve a better degradation effect when the concentrations of PAHs are < 150 mg·kg⁻¹. Results provide a further scientific basis for the remediation of contaminated sites.

L-meta-tyrosine is an herbicidal nonprotein amino acid isolated some years ago from fine fescue grasses and characterized by its almost immediate microbial degradation in soil (half-life <24 h). Nine monohalogenated or dihalogenated analogs of this allelochemical have been obtained through a seven-step stereoselective synthesis from commercial halogenated phenols. Bioassays showed a large range of biological responses, from a growth root inhibition of lettuce seedling similar to that noted with m-tyrosine [2-amino-3-(2-chloro-5-hydroxyphenyl)propanoic acid or compound 8b] to an increase of the primary root growth concomitant with a delay of secondary root initiation [2-amino-3-[2-fluoro-5-hydroxy-3-(trifluoromethyl)phenyl]propanoic acid or compound 8h]. Compound 8b was slightly less degraded than m-tyrosine in the nonsterilized nutritive solution used for lettuce development, while the concentration of compound 8h remained unchanged for at least 2 weeks. These data indicate that it is possible to manipulate both biological properties and degradation of m-tyrosine by halogen addition.

Several amendments were tested on soils obtained from an arsenopyrite mine, further planted with Arrhenatherum elatius and Festuca curvifolia, in order to assess their ability to improve soil's ecotoxicological characteristics. The properties used to assess the effects were: soil enzymatic activities (dehydrogenase, β-glucosidase, acid phosphatase, urease, protease and cellulase), terrestrial bioassays (Eisenia fetida mortality and avoidance behaviour), and aquatic bioassays using a soil leachate (Daphnia magna immobilisation and Vibrio fischeri bioluminescence inhibition). The treatment with FeSO₄1 % w/w was able to reduce extractable As in soil, but increased the extractable Cu, Mn and Zn concentrations, as a consequence of the decrease in soil pH, in relation to the unamended soil, from 5.0 to 3.4, respectively. As a consequence, this treatment had a detrimental effect in some of the soil enzymatic activities (e.g. dehydrogenase, acid phosphatase, urease and cellulase), did not allow plant growth, induced E. fetida mortality in the highest concentration tested (100 % w/w), and its soil leachate was very toxic towards D. magna and V. fischeri. The combined application of FeSO₄1 % w/w with other treatments (e.g. CaCO₃1 % w/w and paper mill 1 % w/w) allowed a decrease in extractable As and metals, and a soil pH value closer to neutrality. As a consequence, dehydrogenase activity, plant growth and some of the bioassays identified those as better soil treatments to this type of multi-contaminated soil.