Contamination of surface waters by mining wastes in the Milluni Valley (Cordillera Real, Bolivia): Mineralogical and hydrological influences

This study is one of very few dealing with mining waste contamination in high altitude, tropical-latitude areas exploited during the last century. Geochemical, mineralogical and hydrological characterizations of potentially harmful elements (PHEs) in surface waters and sediments were performed in the Milluni Valley (main reservoir of water supply of La Paz, Bolivia, 4000 m a.s.l.), throughout different seasons during 2002-2004 to identify contamination sources and sinks, and contamination control parameters. PHE concentrations greatly exceeded the World Health Organization water guidelines for human consumption. The very acidic conditions, which resulted from the oxidation of sulfide minerals in mining waste, favoured the enrichment of dissolved PHEs (Cd > Zn » As >> Cu ∼ Ni > Pb > Sn) in surface waters downstream from the mine. Stream and lake sediments, mining waste and bedrock showed the highest PHE content in the mining area. With the exception of Fe, the PHEs were derived from specific minerals (Fe, pyrite; Zn, Cd, sphalerite, As, Fe, arsenopyrite, Cu, Fe, chalcopyrite, Pb, galena, Sn, cassiterite), but the mining was responsible for PHEs availability. Most of the PHEs were extremely mobile (As > Fe > Pb > Cd > Zn ∼ Cu > Sn) in the mining wastes and the sediments downstream from the mine. pH and oxyhydroxides mainly explained the contrasted availability of Zn (mostly in labile fractions) and As (associated with Fe-oxyhydroxides). Unexpectedly, Pb, Zn, As, and Fe were significantly attenuated by organic matter in acidic lake sediments. Hydrological conditions highly influenced the behaviours of major elements and PHEs. During wet seasons, major elements were diluted by meteoric waters, whereas PHEs increased due to the dissolution of sulfides and unstable tertiary minerals that formed during dry seasons. This is particularly obvious at the beginning of the wet season and contributes to flushes of element transport downstream. The high altitude of the study area compensates for the tropical latitude, rendering the geochemical behaviour of contaminants similar to that of temperate and cold regions. These results might be representative of geochemical processes in ore deposits located in the high Andes plateau, and of their influence on PHE concentrations within the upper Amazon basin. Although mining activities in this region stopped 10 years ago, the impact of mining waste on water quality remains a serious environmental problem

Integration of humanitarian migrants into the host country labour market

The objective of this paper is to identify the factors that influence the labour market integration of new humanitarian migrants in the host country. A number of employment outcomes are examined including access to employment, access to stable employment, the wage/earnings level and the education-occupation mismatch. By using a recently collected panel survey data in Australia, the study shows that pre-migration education, work experience, previous migration episodes, as well as English proficiency, English training, study/job training undertaken in Australia and social capital form important determinants of the labour market integration of refugees in the host country. The paper highlights the differentiated impacts of these resources on the refugees’ outcomes at six months and one year after arrival

Localization and chemical forms of cadmium in plant samples by combining analytical electron microscopy and X-ray spectromicroscopy

International audienceCadmium (Cd) is a metal of high toxicity for plants. Resolving its distribution and speciation in plants is essential for understanding the mechanisms involved in Cd tolerance, trafficking and accumulation. The model plant Arabidopsis thaliana was exposed to cadmium under controlled conditions. Elemental distributions in the roots and in the leaves were determined using scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX), and synchrotron-based micro X-ray fluorescence (μ-XRF), which offers a better sensitivity. The chemical form(s) of cadmium was investigated using Cd LIII-edge (3538 eV) micro X-ray absorption near edge structure (μ-XANES) spectroscopy. Plant μ-XANES spectra were fitted by linear combination of Cd reference spectra. Biological sample preparation and conditioning is a critical point because of possible artifacts. In this work we compared freeze-dried samples analyzed at ambient temperature and frozen hydrated samples analyzed at −170 °C. Our results suggest that in the roots Cd is localized in vascular bundles, and coordinated to S ligands. In the leaves, trichomes (epidermal hairs) represent the main compartment of Cd accumulation. In these specialized cells, μ-XANES results show that the majority of Cd is bound to O/N ligands likely provided by the cell wall, and a minor fraction could be bound to S-containing ligands. No significant difference in Cd speciation was observed between freeze-dried and frozen hydrated samples. This work illustrates the interest and the sensitivity of Cd LIII-edge XANES spectroscopy, which is applied here for the first time to plant samples. Combining μ-XRF and Cd LIII-edge μ-XANES spectroscopy offers promising tools to study Cd storage and trafficking mechanisms in plants and other biological samples

Cd localisation and speciation in a contaminated sediment and in the Znand Cd hyperaccumulating plant Arabidopsis halleri

International audienceThe purpose of this work was to characterise the chemical speciation of Cd in a Zn- and Cd-contaminated dredged sediment subjected to a phytoremediation treatment with the hyperaccumulator plant Arabidopsis halleri

Is phytoextraction a suitable green treatment for metal-contaminated sediments ?

International audienceThe cleaning of waterways by regular dredging generates great volumes of sediments and, owing to human activities, these sediments often contain large amounts of metals. These materials are usually spread on landfill sites. Phytoremediation could be a stategy for the reclamation of these polluted sediments. To our knowledge, phytoextraction with hyperaccumulating plants has been few tested on contaminated sediment. This work focuses on the mechanisms of Cd accumulation in Arabidopsis halleri, a Cd and Zn hyperaccumulator, and the effects of this species on a metal polluted sediment

Zinc distribution and speciation in Arabidopsis halleri x Arabidopsis lyrata progenies presenting various zinc accumulation capacities

The definitive version is available at http://www.blackwell-synergy.com/loi/nphInternational audienceThe purpose of this study was to investigate the relationship between the chemical form and localization of zinc (Zn) in plant leaves and their Zn accumulation capacity. * An interspecific cross between Arabidopsis halleri sp. halleri and Arabidopsis lyrata sp. petrea segregating for Zn accumulation was used. Zinc (Zn) speciation and Zn distribution in the leaves of the parent plants and of selected F1 and F2 progenies were investigated by spectroscopic and microscopic techniques and chemical analyses. * A correlation was observed between the proportion of Zn being in octahedral coordination complexed to organic acids and free in solution (Zn-OAs + Znaq) and Zn content in the leaves. This pool varied between 40% and 80% of total leaf Zn depending on the plant studied. Elemental mapping of the leaves revealed different Zn partitioning between the veins and the leaf tissue. The vein : tissue fluorescence ratio was negatively correlated with Zn accumulation. * The higher proportion of Zn-OAs + Znaq and the depletion of the veins in the stronger accumulators are attributed to a higher xylem unloading and vacuolar sequestration in the leaf cells. Elemental distributions in the trichomes were also investigated, and results support the role of carboxyl and ⁄ or hydroxyl groups as major Zn ligands in these cells

Fate of cadmium in the rhizosphere of Arabidopsis halleri grown in a contaminated dredged sediment

International audienceIn regions impacted by mining and smelting activities, dredged sediments are often contaminated with metals. Phytotechnologies could be used for their management, but more knowledge on the speciation of metals in the sediment and on their fate after colonization by plant roots is needed. This work was focused on a Zn, Cd-contaminated contaminated dredged sediment from the Scarpe river (North of France). Zn, Cd hyperaccumulating plants Arabidopsis halleri from metallicolous and non metallicolous origin were grown on the sediment for five months in a pot experiment. The nature and extent of the modifications in Cd speciation with or without plant were determined by electron microscopy, micro X-ray fluorescence and bulk and micro X-ray absorption spectroscopy. In addition, changes in Cd exchangeable and bioavailable pools were evaluated, and Cd content in leachates was measured. Finally, Cd plant uptake and plant growth parameters were monitored. In the original sediment, Cd was present as a mixed Zn, Cd, Fe sulfide. After five months, although pots still contained reduced sulfur, Cd-bearing sulfides were totally oxidized in vegetated pots, whereas a minor fraction (8%) was still present in non vegetated ones. Secondary species included Cd bound to O-containing groups of organic matter and Cd phosphates. Cd exchangeability and bioavailability were relatively low and did not increase during changes in Cd speciation, suggesting that Cd released by sulfide oxidation was readily taken up with strong interactions with organic matter and phosphate ligands. Thus, the composition of the sediment, the oxic conditions and the rhizospheric activity (regardless of the plant origin) created favourable conditions for Cd stabilization. However, it should be kept in mind that returning to anoxic conditions may change Cd speciation, so the species formed cannot be considered as stable on the long term

Essays on the Economic and Cultural Integration of Migrants

This thesis consists of three self-contained essays. The first, entitled "Integration of Humanitarian Migrants into the Host Country Labour Market: Evidence from Australia", aims at identifying the factors that influence the labour market integration of humanitarian migrants into the host country. A number of refugees' employment outcomes are examined including access to employment, access to stable employment, the wage/earnings level and the education-occupation mismatch. Using a recently collected panel survey data in Australia, the results show that pre-migration education, work experience, previous migration episodes, as well as English proficiency, English training, study/job training undertaken in Australia and social capital form important determinants of the labour market integration of refugees. Moreover, the essay highlights the differentiated impacts of these resources on the refugees' outcomes at six months, one year and two years after arrival in Australia. This essay provides a unique basis of knowledge for informed policy-making and helps identify the ways to facilitate the economic integration of refugees. The second essay, entitled "Ethnic Identity and the Employment Outcomes of Immigrants: Evidence from France", examines the relationship between economic and social integration. More specifically, it explores the influence that ethnic identity exerts on immigrants' labour market performance in the host country. The objective of this essay is twofold: first, to determine the immigrants' ethnic identity and second, to investigate the impact of ethnic identity on the immigrants' employment outcomes. Using a rich survey data from France and relying on a polychoric principal component analysis, this essay proposes two alternative measures of ethnic identity than the ones used in the literature, namely: i) the degree of commitment to the origin country culture and ii) the extent to which the individual holds multiple identities. The essay investigates the impact of the ethnic identity measures on the employment outcomes of immigrants in France. The results show that having multiple identities is associated with an improvement in the employment outcomes of the migrants. However, when addressing the endogenous nature of ethnic identity, there is no significant impact of ethnic identity on the employment outcomes of immigrants. The last essay, entitled "The Effect of 9/11 on Immigrants' Ethnic Identity and Employment: Evidence from Germany", aims at exploring the impact of terrorism on the economic and social integration of immigrants in the host country. Indeed, over the lifecourse of the migrants in the host country, there might be a number of identity shocks that would affect their social integration. This might as well have an effect on their labour market outcomes. This chapter investigates the effect of the 9/11 terrorist attacks on the identity choice and the employment outcomes of Muslim immigrants in Germany. Using longitudinal data from the German Socio-Economic Panel, this essay relies on a difference-in-differences strategy to compare the outcomes of Muslims with non-Muslim immigrants before and after the attacks. One concern is the lack of an appropriate comparison group. In order to address this issue, the essay relies on a regression-adjusted difference-in-differences matching strategy. The results show that Muslim immigrants have decreased their degree of identification with Germany after 9/11 compared to non-Muslims. There is no significant impact of the 9/11 terrorist attacks on Muslims' employment outcomes relative to non-Muslims. The results contribute to provide a better understanding of the process of social integration of immigrants

Interaction between childbearing and partnership trajectories among immigrants and their descendants in France : an application of multichannel sequence analysis

This project is led by Hill Kulu and funded by the European Research Council under the European Commission’s Horizon 2020 Framework Programme: H2020 Excellent Science (H2020 European Research Council, grant number 834103).While there is a large literature investigating migrant marriage or fertility, little research has examined how childbearing and partnerships are interrelated. In this paper, we investigate how childbearing and partnership trajectories evolve and interact over the life course for immigrants and their descendants and how the relationship varies by migrant origin. We apply multichannel sequence analysis to rich longitudinal survey data from France and find significant differences in family-related behaviour between immigrants, their descendants, and the native French. Immigrants’ family behaviour is characterized by stronger association between marriage and childbearing than in the native population. However, there are significant differences across migrant groups. Turkish immigrants exhibit the most conservative family pathways. By contrast, the family behaviour of European immigrants is similar to that of the native population. The study also demonstrates that the family behaviour of some descendant groups has gradually become indistinguishable from that of the native French, whereas for other groups significant differences in family behaviour persist.Publisher PDFPeer reviewe

Family formation and employment changes among descendants of immigrants in France : a multi-process analysis

Funding: This paper is part of a project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 834103).This paper investigates the association between family formation and the labour market trajectories of immigrants’ descendants over the life course. Using rich data from the Trajectories and Origins survey from France, we apply multilevel event history models to analyse the transitions in and out of employment for both men and women by parity. We account for unobserved co-determinants of childbearing and employment by applying a simultaneous-equations modelling. Our analysis shows that women’s professional careers are negatively associated with childbirth. There are differences across descendant groups. The female descendants of Turkish immigrants are more likely to exit employment and less likely to re-enter employment following childbirth than women from other groups. The negative impact of childbearing on employment is slightly overestimated among women due to unobserved selection effects. Among men, the descendants of European immigrants are less likely to exit employment after having a child than other descendant groups. The study demonstrates the negative effect of childbearing on women’s employment, which is pronounced for some minority groups suggesting the need for further policies to help women reconcile work with family life.Peer reviewe