The Potential of Clover Green Amendment, Associated with Biochar, Activated Carbon or Ochre, for the Phytoremediation, Using Populus x. canescens, of a Former Mine Technosol

Metal(loid) soil pollution resulting from past and present mine activities is a serious environmental and health issues worldwide. Therefore, the remediation of those polluted areas has been a growing research interest over the last decades, especially the assisted phytoremediation. In this study, a pot experiment was set up, using a former mine technosol, highly polluted by As and Pb, to which biochar, activated carbon, or ochre was applied, alone or in combination to clover green amendment. Following amendment application, Populus x. canescens cuttings were planted. Results showed that all four amendments reduced soil acidity. However only the first three amendments immobilized As and Pb, while the green amendment drastically mobilized those two pollutants and none of the amendments improved plant growth. In conclusion, the association of clover green amendment to biochar, activated carbon, or ochre did not appear as an efficient remediation strategy in this case; although the aging of the amendments and degradation of the green amendment in the soil with time could have positive outcomes

Soil microbial diversity in urban parks

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Effect of agroecological practices on cultivated lixisol fertility in eastern Burkina Faso

International audienceConservation and restoration of degraded agricultural soils are in fact two important factors of resilient agrosystems and food sovereignty in the context of global change in the Sudano-Sahelian zone. The objective of this study is to determine the effect of adaptive practices for the conservation and restoration of degraded agricultural lixisol. Soil organic carbon, total nitrogen, pH and soil microbiological activity were evaluated in soils surface layers on cultivated plots developed in zaï (Z) and in stone-rows (SR) with contribution of compost (C) since 2006, traditional practices (absolute witness AW) and uncultivated natural vegetation (NV) soils. The results showed that agroecological practices improve soil pH, organic carbon, total nitrogen, electrical conductivity and available phosphorous compared to the absolute witnesses. There was also a decrease in the C/N ratio on the agroecological field relative to the controls. These practices had a positive effect on soil mineralization potential and the soil microorganism's diversity. Substrate-induced respiration (SIR) for 15 carbon sources using the MicroResp technique under agroecological practices and natural vegetation were much higher than those under the absolute witness. Agroecological practices have a positive effect on the different parameters of soil fertility in the semi-arid zone and can thus restore degraded soils

The reduction of the As and Pb phytotoxicity of a former mine technosol depends on the amendment type and properties

International audienceIn remediation of metal(loid) polluted soils, it is crucial to improve soil conditions and reduce metalloid) toxicity to permit plant growth. To do that, amendments, such as biochar, activated carbon, and redmud, can be applied to the soil. Their effects are dependent on their type and properties. The aims of this study were thus to evaluate the potential of diverse biochars, activated carbons, and redmuds to reduce phytotoxicity of a former mine technosol polluted with As and Pb. Two pots experiments were set up. The first one applied on Pontgibaud technosol ten biochars, eight activated carbons, and three redmuds, at 2% for the biochars and activated carbons and 1% for the redmud. Soil pore water properties (pH, electrical conductivity), metal(loid) mobility, and Phaseolus vulgaris growth were monitored. In a second experiment, the five best amendments, one redmud associated with two biochars and two activated carbons, selected based on their ability to improve soil conditions, immobilize metal(loid)s and improve plant growth, were applied. The same plant species was used and soil and plant parameters were measured. Results demonstrated that not all amendments were capable of ameliorating soil conditions and reducing soil phytotoxicity. Moreover, the five selected amendments (biochars from oak bark sapwood and bamboo, activated carbons from vegetal feedstock chemically activated and physically activated, modified redmud) showed good sorption capacity towards Pb, with maximum sorption capacity between 63 and 217 mg g(-1), depending on the amendment, and their combined application led to better soil properties improvement than the single amendments. However, plant growth was only ameliorated further than a single application in the redmud-biochar combination but not in the association of redmud with activated carbon. This study is one of the first to deliver a rapid phytotoxicity test screening demonstrating that redmud associated with particular biochar could be beneficial in reducing the phytotoxicity of technosol polluted with As and Pb and thus allow plant growth and a phytomanagement process

Biochar Application Rate: Improving Soil Fertility and Linum usitatissimum Growth on an Arsenic and Lead Contaminated Technosol

International audienceThe remediation of metal(loid) contaminated sites often requires the application of an amendment, such as biochar. Biochar is the product of biomass pyrolysis and has been shown to reduce soil acidity, immobilize metal(loid)s and thus ameliorate plant growth. The beneficial effects of biochar are usually higher at a higher dose. However, an excessive dose can have negative outcomes due to nutrient loss. The application of an amendment to the soil comes at a financial cost, especially if the contaminated area is large, and therefore the optimum dose must be determined. In addition, to overcome the cost of biochar application, the use of a plant with economic benefits, such as flax, can be a suitable option. In this context, a mesocosm study, on a former mining soil polluted by As and Pb was performed, using flax and biochar applied at increasing concentrations. Results showed an increase in soil pH and the immobilization of Pb with increasing biochar doses. These ameliorations led to better plant growth. A higher biochar dose increased plant growth up to a 3% application rate, from which point dry weight no longer increased.Metal(loid) concentrations decreased between 1 and 3% biochar, and then increased at higher doses. It can thus be concluded that with 3% biochar, soil properties are ameliorated, metal(loid)s are immobilized, and plant growth increases, and a higher biochar application rate does not bring about better outcomes. Therefore, a 3% biochar application dose seems to be the best application dose to improve soil conditions and plant growth at a lower cost

Effect of nitrate and ammonium fertilization on Zn, Pb, and Cd phytostabilization by Populus euramericana Dorskamp in contaminated technosol

International audienceThis study aimed at assessing the effect of nitrogen addition under two forms, nitrate and ammonium, on the stabilization of Zn, Pb, and Cd by Populus euramericana Dorskamp grown in contaminated soils for 35 days under controlled conditions. Temporal changes in the soil pore water (SPW) were monitored for pH, dissolved organic carbon (DOC), and total dissolved concentrations of metals in the soils rhizosphere. Rhizospheric SPW pH decreased gradually with NH4 + addition and increased with NO3 − addition up to one unit, while it slightly decreased initially then increased for the untreated control soil DOC increased with time up to six times, the highest increase occurring with NH4 + fertilization. An increase in the metal concentrations in the rhizospheric SPW was observed for NH4 + addition associated with the lowest rhizospheric SPW pH, whereas the opposite was observed for the control soil and NO3 − fertilization. Fertilization did not affect plant shoots or roots biomass development compared to the untreated control (without N addition). Metals were mostly accumulated in the rhizosphere and N fertilization increased the accumulation for Zn and Pb while Cd accumulation was enhanced for NH4 + addition. Collectively, our results suggest metal stabilization by P. euramericana Dorskamp rhizosphere with nitrogen fertilization and are potential for phytostabilization of contaminated technosol

Effect of biochar and redmud amendment combinations on Salix triandra growth, metal(loid) accumulation and oxidative stress response

International audienceRemediation of metal(loid) polluted soils is an important area of research nowadays. In particular, one remediation technique is much studied, phytomanagement. Phytomanagement combines amendment application and plant growth in order to reduce the risk posed by contaminants. Salicaceae plants showed tolerance towards metal(loid)s and the ability to accumulate high amounts of metal(loid)s in their tissue. Amendments are often applied to counterbalance the reduced soil fertility and high metal(loid) concentrations. Two amendments gathered attention over the last decades, biochar (product of biomass pyrolysis), which can be activated for better effects, and redmud (by-product of alumina production). Those two amendments showed ability to improve soil conditions and thus plant growth, although few studied their combined application. Moreover, since metal(loid)s are known to induce the overproduction of reactive oxygen species, it is important to measure the level of oxidative stress in the plant, to which plants respond using enzymatic and non-enzymatic systems. But no studies evaluate the response of Salicaceae plants to metal(loid) stress and amendment application at the biochemical level in a real soil condition. Therefore, a mesocosm study was set up to evaluate the effect of amending a mine soil with redmud combined to diverse biochars on the soil properties and Salix triandra growth, metal (loid) accumulation and stress marker levels. Results showed that all amendment combinations improved the soil fertility, reduced metal(loid) mobility and thus ameliorated Salix triandra growth, which accumulated metal (loid)s mainly in its roots. Moreover, among the different amendment combinations, Salix triandra plants still suffered from oxidative stress when grown on PG soil amended with redmud and chemical activated carbon, showing elevated levels of phenolic compounds and salicinoids and important antioxidant and enzymatic activities. Finally, one treatment showed levels of these stress markers similar or lower than the control, the combination of redmud with steam activated carbon. In conclusion, this treatment seemed a good solution in a phytomanagement strategy using Salix triandra, improving soil conditions and plant growth and reducing oxidative stress level in the plant roots

Rhizosphere effects of Populus euramericana Dorskamp on the mobility of Zn, Pb and Cd in contaminated technosols

International audiencePurpose This study aimed at investigating the rhizosphere effects of Populus euramericana Dorskamp on the mobility of Zn, Pb and Cd in contaminated technosols from a former smelting site. Materials and methods A rhizobox experiment was conducted with poplars, where the plant stem cuttings were grown in contaminated technosols for 2 months under glasshouse conditions. After plant growth, rhizosphere and bulk soil porewater (SPW) were sampled together. SPW properties such as pH, dissolved organic carbon (DOC) and total dissolved concentrations of Zn, Pb and Cd were determined. The concentrations of Zn, Pb and Cd in plant organs were also determined. Results and discussion Rhizosphere SPWpH increased for all studied soils by 0.3 to 0.6 units compared to bulk soils. A significant increase was also observed for DOC concentrationsregardless of the soil type or total metal concentrations, which might be attributed to the plant root activity. For all studied soils, the rhizosphere SPW metal concentrations decreased significantly after plant growth compared to bulk soils which might be attributed to the increase in pH and effects ofroot exudates. Zn, Pb and Cd accumulated in plant organs and the higher metal concentrations were found in plant roots compared to plant shoots.Conclusions The restricted transfer of the studied metals to the plant shoots confirms the potential role of this species in the immobilization of these metals. Thus, P. euramericana Dorskamp can be used for phytostabilization of technosols

Biochar and compost effects on the remediative capacities of Oxalis pes-caprae L. growing on mining technosol polluted by Pb and As

International audienceSelection of plant species with a great remediating capacity and a high biomass production is an important step for depolluting soils especially mine soils. Hyperaccumulators are used in phytoextraction for extracting metals from soil to roots and to translocate them to aerial parts. While in phytostabilization that usually requires amendment, metals are accumulated in the plant roots. The purpose of this study is to investigate Oxalis pes-caprae L. tolerance to Pb and As from Pontgibaud mine soil in France amended with compost and/or biochar. Oxalis bulbils were harvested in three sites located around Algiers: (1) an agricultural land in Reghaia, (2) an area planted with Pines at the USTHB university campus, and (3) the polluted bank of the El Harrach river. The small and medium bulbil sizes were selected from each locality. Concerning the experimental soil, five mixtures of Pontgibaud technosol (P) with amendments compost (C) and biochar (Bc) were prepared: PC, PBc5, PBc10, PBc5 C, PBcC (w/w). The results indicate that amendments alter the soil physico-chemical characteristics and the mobility of metal(loid)s. They also reveal that As and Pb are differently distributed in plant organs. Medium bulbils especially from El Harrach river and the university campus have shown a better growth. Seedlings growth rate has been the highest in Pontgibaud amended with PC and the lowest in PBc10