Institute of Geography and Earth Sciences, Aberystwyth University, Ceredigion, SY23 3DB, UK,
Environ Sci Pollut Res Int. 2013 Dec;20(12):8729-38. doi: 10.1007/s11356-013-1826-3. Epub 2013 Jun 1.
For sheep grazing pastures in areas of mineralisation and former metalliferous mining activity, an excessive intake of potentially harmful elements (PHEs) such as fluorine (F) and lead (Pb) can result in clinical and subclinical toxicity. The prime aim of our work was to calculate the intakes of both of these PHEs by sheep grazing pastures in the mineralised/mined Peak District area of Derbyshire. The bi-monthly sampling of topsoils (0-15 cm depth) and the faeces of sheep from fields at seven farms was undertaken for a 1-year period. These samples were analysed for titanium that allowed the rates of soil ingestion (and hence also herbage ingestion since we assume that the sheep have an overall diet of 1 kg dry matter (DM)/day) to be determined. Our findings were then combined with previously published soil and soil-free pasture herbage F and Pb concentrations determined from the seven farms to calculate the intakes of both PHEs. The results show seasonal variations of soil ingestion at the seven farms ranging from <0.1 to 20.1 % of the DM intake (median=3 %), with the highest rates of ingestion being associated with the winter-spring (i.e. December-April) period. Our calculations show that at some farms, sheep can be exposed to dietary concentrations in excess of recommended guidelines potentially throughout the whole year, though livestock movement to less-contaminated pastures would lessen any toxic impact. Because the soil concentrations are greater than those associated with soil-free pasture herbage, ingested soils are the main dietary source of Pb and (especially) F to sheep. However, subjecting freshly sampled topsoils to sequential extraction procedures undertaken in the laboratory indicates that the majority of Pb and (especially) F may not be readily soluble in the ovine digestion system, so reducing the quantities of both PHEs available for absorption.
对于在矿化和以前的金属矿区放牧的绵羊，过量摄入潜在有害元素（PHEs），如氟（F）和铅（Pb），可能会导致临床和亚临床毒性。我们工作的主要目的是计算在德比郡峰区矿区放牧的绵羊对这两种 PHE 的摄入量。我们对来自七个农场的田间表层土壤（0-15 厘米深度）和绵羊粪便进行了为期一年的双月采样。这些样本经过钛分析，从而可以确定土壤摄入量（因此也可以确定牧草摄入量，因为我们假设绵羊的总体饮食为 1 公斤干物质（DM）/天）。然后，我们将我们的发现与先前从七个农场发表的土壤和无土壤牧草 F 和 Pb 浓度相结合，计算出这两种 PHE 的摄入量。结果显示，七个农场的土壤摄入量存在季节性变化，范围为 DM 摄入量的<0.1-20.1%（中位数=3%），摄入率最高与冬春（即 12 月至 4 月）期间有关。我们的计算表明，在某些农场，绵羊可能全年都面临超过建议指南的膳食浓度，尽管牲畜转移到污染较少的牧场会减轻任何毒性影响。由于土壤浓度高于与无土壤牧草相关的浓度，因此摄入的土壤是绵羊摄入 Pb 和（特别是）F 的主要膳食来源。然而，将新采集的表层土壤进行实验室中进行的连续提取程序表明，大部分 Pb 和（特别是）F 可能不易溶解于绵羊消化系统中，因此减少了两种 PHEs 的可吸收量。
