Correlation analysis as a tool to investigate the bioaccessibility of nickel, vanadium and zinc in Northern Ireland soils

Abstract

Correlation analyses were conducted on nickel (Ni), vanadium (V) and zinc (Zn) oral bioaccessible fractions (BAFs) and selected geochemistry parameters to identify specific controls exerted over trace element bioaccessibility. BAFs were determined by previous research using the Unified BARGE Method. Total trace element concentrations and soil geochemical parameters were analysed as part of the Geological Survey of Northern Ireland Tellus Project. Correlation analysis included Ni, V and Zn BAFs against their total concentrations, pH, estimated soil organic carbon (SOC) and a further eight element oxides. BAF data were divided into three separate generic bedrock classifications of basalt, lithic arenite and mudstone prior to analysis, resulting in an increase in average correlation coefficients between BAFs and geochemical parameters. Sulphur trioxide and SOC, spatially correlated with upland peat soils, exhibited significant positive correlations with all BAFs in gastric and gastrointestinal digestion phases, with such effects being strongest in the lithic arenite bedrock group. Significant negative relationships with bioaccessible Ni, V and Zn and their associated total concentrations were observed for the basalt group. Major element oxides were associated with reduced oral trace element bioaccessibility, with Al 2 O 3 resulting in the highest number of significant negative correlations followed by Fe 2 O 3. Spatial mapping showed that metal oxides were present at reduced levels in peat soils. The findings illustrate how specific geology and soil geochemistry exert controls over trace element bioaccessibility, with soil chemical factors having a stronger influence on BAF results than relative geogenic abundance. In general, higher Ni, V and Zn bioaccessibility is expected in peat soil types.

Soil-geochemical factors controlling the distribution and oral bioaccessibility of nickel, vanadium and chromium in soil

“…Using generic bedrock types ensures that sample sizes remain sufficiently robust during analysis and EDA, as defining discrete minor geologic formations present in Northern Ireland would reduce sample sizes to a prohibitively narrow range of statistical significance. Such an approach also reduces variance and increases normality in the distribution of geochemistry data (Jordan et al, 2007;Zhang et al, 2007;Palmer et al, 2013).…”

“…Previous trace element bioaccessibility research in Northern Ireland has shown that oral bioaccessibility is not primarily a function of total trace element concentrations in soil (Barsby et al, 2012;Palmer et al, 2013;Cox et al, 2013), diminishing the suitability of reliance on total soil contaminant concentrations as a driver for contaminated land management decisions. Following from these findings, specific geochemical factors accounting for the variability in trace element bioaccessibility across the country ϯ require further investigation.…”

“…Following from these findings, specific geochemical factors accounting for the variability in trace element bioaccessibility across the country ϯ require further investigation. Correlation studies exploring relationships between trace element bioaccessibility and other geochemical variables found statistically significant relationships which varied across different underlying bedrock types (Palmer et al, 2013;Cox et al 2013). For example, sulphur measured as sulphur trioxide (SO 3 ) and loss on ignition (LOI) data showed strong positive associations with Ni and V bioaccessibility throughout Northern Ireland, whilst calcium appeared to exert either positive or negative influences over bioaccessibility depending upon the underlying bedrock type (Palmer et al, 2013).…”

Investigating relations between environmental toxins in Northern Irish soils and streams and Chronic Kidney Disease prevalence

“…represented across Northern Ireland (Barsby et al 2012;Palmer, et al 2013). The method used for assessing the bioaccessibility of soil samples was the Unified BARGE Method (Wragg et al 2009;BARGE -INERIS, 2011).…”

“…The method represented the oral exposure pathway through the stomach, and stomach with intestine using synthetic materials in place of the digestive system including gastric fluid, saliva, duodenal fluid and bile (Barsby, et al 2012). This research used the bioaccessible fraction (BAF %) analysed by Barsby et al (2012) and Palmer, et al (2013) which was calculated from the Unified BARGE Method test for each sample using the highest bioaccessible PTE concentration of the digestive extracts. Full details of the Unified BARGE Method used to produce the BAF data used in this study are provided in Barsby et al (2012).…”