Kinetic study of phytotoxicity induced by foliar lead uptake for vegetables exposed to fine particles and implications for sustainable urban agriculture

At the global scale, foliar metal transfer occurs for consumed vegetables cultivated in numerous urban or industrial areas with a polluted atmosphere. However, the kinetics of metal uptake, translocation and involved phytotoxicity was never jointly studied with vegetables exposed to micronic and sub-micronic particles（PM）. Different leafy vegetables（lettuces and cabbages） cultivated in RHIZOtest？ devices were, therefore, exposed in a greenhouse for 5, 10 and 15 days to various Pb O PM doses. The kinetics of transfer and phytotoxicity was assessed in relation to lead concentration and exposure duration. A significant Pb accumulation in leaves（up to 7392 mg/kg dry weight（DW） in lettuce） with translocation to roots was observed. Lead foliar exposure resulted in significant phytotoxicity, lipid composition change, a decrease of plant shoot growth（up to 68.2% in lettuce） and net photosynthesis（up to 58% in lettuce）. The phytotoxicity results indicated plant adaptation to Pb and a higher sensitivity of lettuce in comparison with cabbage. Air quality needs, therefore, to be considered for the health and quality of vegetables grown in polluted areas, such as certain megacities（in China, Pakistan, Europe, etc.） and furthermore, to assess the health risks associated with their consumption.

Effects of meteorological conditions and topography on the bioaccumulation of PAHs and metal elements by native lichen(Xanthoria parietina)

The bioaccumulation of PAHs and metal elements in the indigenous lichens Xanthoria parietina was monitored during two years at a quarterly frequency,in 3 sites of contrasted anthropic influence.The impact of the meteorological factors(temperature,relative humidity,rainfall,wind speed)was first estimated through principal component analysis,and then by stepwise multilinear regressions to include wind directions.The pollutants levels reflected the proximity of atmospheric emissions,in particular from a large industrial harbor.High humidity and mild temperatures,and in a lower extent low wind speed and rainfall,also favored higher concentration levels.The contributions of these meteorological aspects became minor when including wind direction,especially when approaching major emission sources.The bioaccumulation integration time towards meteorological variations was on a seasonal basis(1–2 months)but the wind direction and thus local emissions also relied on a longer time scale(12 months).This showed that the contribution of meteorological conditions may be prevalent in remote places,while secondary in polluted areas,and should be definitely taken into account regarding long-term lichen biomonitoring and inter-annual comparisons.In the same time,a quadruple sampling in each site revealed a high homogeneity among supporting tree species and topography.The resulting uncertainty,including sampling,preparation and analysis was below 30%when comfortable analytical conditions were achieved.Finally,the occurrence of unexpected events such as a major forest fire,permitted to evaluate that this type of short,although intense,events did not have a strong influence on PAH and metals bioaccumulation by lichen.