tailieunhanh - Uptake of organic chemicals in plants Human exposure assessment

Natural groundwater quality changes start in the soil, where infiltrating rainfall dissolves carbon dioxide from biological activity in the soil to produce weak carbonic acid that may assist removal of soluble minerals from the underlying rocks, . calcite cements. At the same time, soil organisms consume some of the oxygen that was dissolved in the rainfall. In temperate and humid climates with significant recharge, groundwater moves relatively quickly through the aquifer. Contact time with the rock matrix is short and only readily soluble minerals will be involved in reactions. Groundwater in the outcrop areas of aquifers is. | Uptake of organic chemicals in plants Human exposure assessment PhD thesis M. Sc. Environmental Chemistry Charlotte N. Legind LC 2430 October 2008 Department of Agriculture and Ecology Faculty of Life Sciences University of Copenhagen National Environmental Research Institute University of Aarhus Department of Environmental Engineering Technical University of Denmark Summary This work gives an insight into the assessment of human exposure to xenobiotic compounds in food stuffs all the way from experiments to the use of model tools. In focus are neutral organic compounds primarily from petroleum and their uptake into plants. A new analytical method was developed for the determination of chemical activity of volatile compounds in plant tissue and soil. Chemical activity is a valuable concept. Chemical activity is related to the chemical potential and is a measure of how active a substance is in a given state compared to its reference state. It is the difference in chemical activity that drives diffusion. The analytical method employs SPME solid-phase microextraction is automated fast reliable uses almost no solvents compared to traditional methods and reduces the contact between sample and the person handling it. The method was applied for the determination of BTEX benzene toluene ethylbenzene o- m- and p-xylene and naphthalene in willows from a growth chamber experiment and birch from a fuel oil polluted area. The uptake of xenobiotic compounds in plants is described. In spite of the large differences between plants and the vast amount of organic chemicals in use general uptake pathways to plants have been described. Also process oriented model tools exist for the calculation of uptake into plants. Model tools are needed to answer the following question Do chemicals in our daily diet pose a risk to human health Here crop-specific models were used to estimate the daily exposure to selected chemicals with the diet for both adults and children. The exposure of children