Dichlorodiphényltrichloroéthane

Le DDT (ou dichlorodiphényltrichloroéthane ou bis p-chlorophényl-2,2 trichloro-1,1,1 éthane ou encore le 1,1,1-trichloro-2,2-bis(p-chlorophényl)éthane pour la nomenclature chimique) est un produit chimique (organochloré) synthétisé en 1874 mais dont les propriétés insecticides et acaricides n'ont été découvertes qu'à la fin des années 1930. À partir de la Seconde Guerre mondiale, il est rapidement devenu l'insecticide moderne le plus utilisé, avec beaucoup de succès aussi bien militairement que civilement, dans les champs, dans les maisons et pour la lutte contre divers arthropodes vecteurs de maladie ( paludisme, typhus exanthématique, peste bubonique), et également comme insecticide agricole. Dès les années 1970, il est toutefois interdit dans la plupart des pays en raison de son impact environnemental et sanitaire élevé, mais, en raison de sa persistance élevée, on en retrouve encore des traces dans le sol aujourd'hui. C'est un solide incolore très hydrophobe, avec une légère ode

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)

Pauline Grandjean

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.

2011

Occurrence of persistent toxic substances in soils, sediments, fishes and human breast milk in southern Vietnam

Ngoc Vinh Nguyen

Global contamination and toxic effects of persistent toxic substances (PTSs) have been an emerging environmental issue and have received considerable attention during the past four decades. The rapid agricultural and industrial growths as well as the expansion of urban areas in Hochiminh City and Mekong River Delta, two of the most densely populated areas in the world with about 26 million peoples, result in the widespread contamination of PTSs in southern Vietnam. Due to adverse effects to human health and environment, more attention has been paid to PTSs in Vietnam since the early 1990s. However, these works mainly focused on PTSs in water, soil and sediment media. PTSs in animals, birds and human (blood, adipose tissue, breast milk, etc.) have drawn less attention due to high cost of research and the need of sophisticated analytical techniques. With the support of Swiss Agency for Development and Cooperation (SDC) project in the frame of a collaboration between Vietnam and Switzerland, we have carried out the research named "Persistent Toxic Substances in southern Vietnam; Development analytical methods, bioaccumulation and modeling". Our research has established suitable analytical methods, which is able to analyze simultaneously PCBs, PBDEs, OCls pesticides and especially, mirex and toxaphene, which are analyzed for the first time in Vietnam, in various matrices such as soil/sediment, fish and human breast milk samples by HRGC/LRMS. The sampling sites (including Hochiminh City, Dongnai – Baria Vungtau province and Mekong Delta) have been selected based on previous studies in Vietnam and collected documents from Vietnam Environment Administration and POPs Project of Vietnamese government. Twenty-one PCB congeners, twelve PBDE congeners and twenty-six organochlorine pesticides were chosen for research due to their high toxicities. Soil, sediment, fish tissue, and human breast milk were selected as the matrices to examine the PTSs residue. The obtained results showed that PTSs levels of soil and sediment samples in southern Vietnam are not so high, e.g. DDTs and PCBs levels are lower than those in previous studies in Vietnam. Endosulfans were found in almost all sites suggesting the widespread contamination due to their large usage in agriculture. Toxaphene was only found in soil close to agrichemical warehouse at high level indicating potential source of toxaphene from the pesticide stockpiles. PBDEs were detected in most of the samples but at the low levels, which shows a possibly atmospheric deposition source. Other PTSs were detected at low levels (< 5 ng/g dry wt.) or below LOD of the analytical method. PTSs concentrations in wild fish samples from Saigon and Tien Rivers are lower than those determined in previous studies in Vietnam and in the world. However, unlike DDTs, PCBs showed a slow decreasing in fish samples and this suggests a continuous contamination. Besides, due to large usage in agricultural activities, endosulfans were also found in almost all wild fish samples from Saigon and Tien River (23.9 and 8.3 ng/g lipid wt., respectively). Other PTSs were detected at low levels (< 5 ng/g dry wt.) or below LOD of the analytical method. PTSs levels in human breast milk of HCMC residents are lower than those in previous study (except PCBs and CHLs). The higher PCB residues observed in human breast milk from HCMC suggest continuously high exposure to PCBs via the food chain to human. In this study, PTSs levels in human breast milk of primiparous mother higher than those in multiparous mothers. This trend well agrees with previous study in Hanoi and HCMC. By using statistic methods for obtained results (cluster analysis and PCA), we have shown the similarity of PTSs profiles pattern between landfill soil, TN-SG River sediments and Saigon River fish samples. Logically, we might suggest that there is a transfer of PTSs compounds from landfill and TN-SG River to fish samples collected from Saigon river. Our results clearly demonstrate that municipal and industrial waste from landfill and urban activities of HCMC could be considered as PTSs pollution sources. The results of the present study have contributed to the improvement of PTSs research capability of Vietnam. This research also efficiently supports and serves the projects of monitoring, studying and evaluating impacts of PTSs on South Vietnam ecosystem during the implementation of NIP under Stockholm Convention.

EPFL2009

Occurrence of persistent toxic substances in soils, sediments, fishes and human breast milk in southern Vietnam

Ngoc Vinh Nguyen

EPFL2009