Trace Metal(oid) Accumulation in Edible Crops and Poplar Cuttings Grown on Dredged Sediment Enriched Soil.

The development of a biomonitor in the context of multiple-element contamination in urban environments was tested by comparing element transfer in edible crops and poplar ( Torr. × A. Henry cutlivar 'Skado'). A multielemental analysis was performed with various common edible crops (cucumber [ L.], pepper [ L.], cabbage [ L.], and lettuce [ L.]) and the Skado poplar cultivar grown on soils that received sediments dredged from water canals in the 1960s. Sediments were distributed unevenly on the soil, allowing us to sample two types of areas that were either weakly (Area 1) or highly (Area 2) contaminated, mainly by Cd, Pb, and Zn. We registered an accumulation of Cd and Zn in the edible parts of crops, with higher values recorded for leafy vegetables than for fruit vegetables. We did not detect any accumulation of Pb in the plant species studied. We calculated the fresh mass that must be consumed daily to reach tolerable daily intake (TDI) recommendations for each element and found evidence that Cd could be ingested in sufficient amounts to reach the TDI in this context. Poplar and pepper leaves accumulated more Cd and Zn than the edible parts of the study crops grown on both substrates, which suggests that poplar and pepper may be suitable species for biomonitoring element transfer to vegetation in this context.

Accumulation of trace elements in edible crops and poplar grown on a titanium ore landfill.

Urban gardening has recently experienced rapid development; however, the risk of the transfer of toxic elements from neighboring industry needs to be evaluated. We performed a multi-elemental analysis with several common edible crops (cucumber, pepper, cabbage, and lettuce) and poplar grown directly on a titanium ore landfill as a maximized scenario of exposure. Despite elevated concentrations of soil Ca, Fe, Mn, and Ti resulting from the industrial process, we did not register higher accumulation of these elements in the edible parts of crops or in poplar leaves grown on red gypsum compared with the control soil. Only S concentrations were higher in plants grown on the red gypsum, especially for cabbage. The principal component analysis among elements for plants grown on red gypsum indicated that S and Mn were accumulated by different plant species than Cd, Cu, and Zn. The poplar clone had a significantly higher transfer of S and Cr than the control and is a suitable tree species for monitoring element transfer to vegetation in this industrial context. By comparing our data with tolerable daily intake (TDI) recommendations, we demonstrated the low risk of cultivating edible crops directly on an industrial substrate in a maximized scenario of exposure, except for Cr, for which the toxicity depends on the bioavailable form. However, we did not consider the cumulative effects of the various elements because there are no current guidelines, and further research is needed to address this question.

Dendrochemical assessment of mercury releases from a pond and dredged-sediment landfill impacted by a chlor-alkali plant.

Although current Hg emissions from industrial activities may be accurately monitored, evidence of past releases to the atmosphere must rely on one or more environmental proxies. We used Hg concentrations in tree cores collected from poplars and willows to investigate the historical changes of Hg emissions from a dredged sediment landfill and compared them to a nearby control location. Our results demonstrated the potential value of using dendrochemistry to record historical Hg emissions from past industrial activities.

Mercury uptake into poplar leaves.

Tailings dumps require mercury stabilization to prevent air pollution by evaporated mercury, which can be achieved through plant covers. Plants are considered a net sink for atmospheric Hg via incorporation into leaf tissues. However, most studies related to Hg uptake by plants have considered plants exposed to only atmospheric Hg, whereas in the case of tailings dumps, plants are potentially exposed to both soil and atmospheric Hg. The goal of this work is to evaluate the relative contributions of root and atmospheric pathways by growing poplar (Populus trichocarpa X Populus maximowiczii/var Skado) cuttings on either control or polluted substrates and under either natural or controlled exposure conditions. We showed that foliar Hg concentrations significantly increased with age, reaching 120 ng g(-1) dry mass when poplars were exposed to Hg-contaminated substrate under natural exposure. Remarkably, we did not observe significantly different Hg concentrations in poplar leaves grown on either the control or polluted substrates when cultivated together in growth chambers. Our set of data prompted us to conclude that Hg entry into poplar leaves is exclusively through an atmospheric pathway. Our results are discussed in line with existing literature.