Effects of different soil amendments on phytoremediation from a cadmium and DDTs co-contaminated soil by Sedum alfredii (Cd hyperaccumulator) co-cropped with Ricinus communis (DDT accumulator)

Soil pollution is a major environmental problem actually in China and in the world. It increases environmental risks and can affect humans through the food chain. Like solutions to clean-up the soils are generally expensive and can have side effects on environment, phytoremediation, an environmental friendly technology is a good alternative to traditional remediation. Nevertheless, some improvements must be done to increase its efficiency and make it economically viable. The goal of this work is to study two strategies respectful of the environment to improve the efficiency of phytoremediation: the co-cropping and the addition of amendments. Two Chinese species, Sedum alfredii (hyperaccumulator of cadmium) and Ricinus communis (accumulator of DDT) were co-cropped in pots with a soil contaminated by cadmium and DDT, in which different amendments (rapeseed waste, pig manure, a bio-surfactant: tea saponin, one of its by-product, and sulfur) were added to observe if they increase the efficiency of the phytoremediation. Bacteria were also used to improve DDT degradation. If the ricinus grew fast and easily, sedum biomass was very low and seems not suitable for co-cropping in these conditions. The rapeseed waste inhibit the growth of plants, suggesting that the dose was probably to high. Other amendments allowed a relatively similar growth with sensitively the best for tea saponin and microbes do not affect significantly the biomass. After determined in laboratory that tea saponin enhance the desorption of DDT and Cd in soil, an other pot experiment was started with Ricinus communis in soil amended with different concentrations of saponin to see if it also improve the phytoremediation. In the future, if the addition of amendments can enhance the phytoremediation as expected, analysis of parameters such as the quantity of nutrients or pollutants bioavailable or the structure of dissolve organic matter (DOM) might be done to see if they can explain this phenomenon. Further analysis in field conditions and with optimal concentrations of amendments are needed to determine if and in which conditions these strategies can be applicable at large scale.

Assainissement de la décharge de Colliare à Penthaz – Etude de variantes

Gabrielle Hack

The landfill of Colliare is situated on the left bank of the river « la Venoge », at the place of a former gravel pit in the municipality of Penthaz. It was exploited until 1995 and many different wastes were deposited in it, such as incineration slag of household waste, grinding of cars, residues of biostabilizer, waste of construction site and materials of excavation. A water pollution due to the presence of this landfill was noticed at the beginning of the nineties, mainly by ammonium and nitrite. In one measure chromium was also found in rather important concentration. The presence of these compounds in water reflects the existence of biodegradation of the organic matter present in the mass of waste. The concentration of ammonium being higher than the limit imposed by Swiss law, a remediation is necessary. Various projects of remediation were made during the last twenty years, the main being to clean up this former landfill in order to have the possibility of creating a new one for bioactive wastes. This project was rejected by the « Grand Conseil » and the remediation of the landfill was set aside during several years. Today, the question is to study various variants of remediation to define which one would be the best for Colliare. The choice of the variants was limited either to a containment of the landfill’s surface or to bioventing. This work studies the possible implantation of these two variants, by analysing their advantages and disadvantages so as to facilitate the choice of the final solution. For that purpose, laboratory analyses were made to define the list of contaminants present in the mass of waste that risk to contaminate the water near the landfill. It was demonstrated that beside the already turn out organic pollution, the landfill contains a huge quantity of PCB and PAH as well as several heavy metals such as chromium, lead or copper. Furthermore analyses to obtain information on the quantity of biodegradable organic matter were made. It was shown that organic matter constitues only a small percentage of the mass of waste. Landfill containment is not considered as a real remediation because the contaminants stay in the site. The solution is studied here because of the various types of contaminants present in the waste. Furthermore the time it takes to implement is relatively short and it is possible to put vegetation on the site just after the installation of the mineral cover. There are thus few impacts on the fauna and the flora and the contaminants are normally not a risk anymore for the water during all the life of the containment. Bioventing has as main advantage to be a real method of remediation. The problem of its implementation in the case of Colliare is the presence of PCB and PAH in the mass of waste. Indeed biodegradation would have no effect on these compounds and the risk of water contamination would not decrease thanks to bioventing. Furthermore the small percentage of organic matter does not justify the implementation of such an installation. Finally the costs of both variants were compared. Containment costs less than bioventing. Thus the cost of bioventing is too high to implement it in addition to containment except if the decrease of greenhouse gases emissions is enough important for being exchanged on the market of carbon. The solution chosen here is landfill containment, although it is not ideal for a real remediation of the site.

2011

Associative interplay of plant growth promoting rhizobacteria (Pseudomonas aeruginosa QS40) with nitrogen fertilizers improves sunflower (Helianthus annuus L.) productivity and fertility of aridisol

Muhammad Saleem Arif, Luca Bragazza, Alexandre Buttler, Vincent Eric Jules Jassey, Muhammad Riaz

The environmental and economic impacts of chemical fertilizer have encouraged farmers to integrate them with organic materials, an important nutrient management strategy for sustainable agriculture production. In the present study, we conducted field experiments to study the effects of nitrogen enriched compost (NEC) and mineral nitrogen (MN) fertilizer with a selected plant growth promoting rhizobacterial (PGPR) strain, Pseudomonas aeruginosa QS40, on productivity of sunflower and soil fertility. The results demonstrated that integrated application of PGPR with organic-inorganic N significantly increased shoot and root length, leaf area, total chlorophyll, head diameter, fresh biomass, straw-achene yield and N uptake in sunflower compared to unamended control and PGPR alone. The results also showed that integrated N biofertilizer regime enhanced soil microbial biomass, enzymatic activities and soil nitrogen contents. We also observed significant changes in rhizosphere soil pH, abundance of cultivable bacteria and arbuscular mycorrhizae fungi (AMF) root colonization. Treatment and year interaction was significant for dissolved organic carbon (DOC) and microbial biomass carbon (MBC) only. These results suggest that the efficiency of PGPR could be improved with increased availability of labile C substrate resource in NEC amended aridisol. We conclude that the application of NEC fertilizer with efficient PGPR biofertilizer may improve sunflower productivity and soil chemical and biological fertility in nutrient-poor agroecosystems of arid and semi-arid regions. (C) 2016 Elsevier B.V. All rights reserved.

Elsevier Science Bv2016

Assainissement de la décharge de Colliare à Penthaz – Etude de variantes

Gabrielle Hack

2011