Uncertainty and Sensitivity Analysis of Spatial Predictions of Heavy Metals in Wheat

Abstract

Heavy metals seriously threaten the health of human beings when they enter the food chain. Therefore, policymakers require precise predictions of heavy metal concentrations in agricultural crops. In this paper we quantify the uncertainty of regression predictions of Cd and Pb in wheat (Triticum aestivum L.) and the contributions to the uncertainties in these predictions associated with inputs to the regression model. For each node of the 500- x 500-m grid covering the arable soils in The Netherlands, a latin hypercube sample size of 1000 is constructed from the uncertainty distributions of the explanatory variables (pH, soil organic matter [SOM], and heavy metal concentration in soil), the regression coefficients, and the random term of the regression model. This sample is used as input for the regression model to obtain 1000 values from the uncertainty distributions of the log(Cd) and log(Pb) concentration in wheat. There were no nodes where the recent EU quality standards for Cd and Pb (0.2 mg kg(-1) fresh wt.) in wheat were almost certain to be exceeded. For most nodes with clay soils, the quality standard for Cd in wheat almost certainly will not be exceeded; for Pb this is much less certain. The uncertainty in the Cd concentration in soil contributes most to the uncertainty in the predicted Cd concentrations in wheat (36% on the average), followed by the random term of the regression model (23%). For Pb the contribution of the random term is by far the largest (52%).

Insuring Eggs in Baskets: Should the Government Insure Individual Risks?

“…Thus, the marginal distribution for each data series remains unchanged, but the correlations among the series are adjusted. The Iman and Conover (1982) method has been employed in a variety of practical applications; for example, see Maia and Neto (2004), Brus and Jansen (2004), and Wu and Tsang (2004).…”

Uncertainty and stochastic sensitivity analysis of the GeoPEARL pesticide leaching model

“…soil properties and climatic data) (e.g. Diaz-Diaz and Loague, 2000), in pesticide properties (particularly the pesticide half-life and the coefficient for sorption on organic matter) (Boesten, 1991;Dubus et al, 2003), it can result from the use of imperfect pedotransfer functions (Tiktak et al 1999;Dubus et al, 2003) or be caused by spatial interpolation errors (Brus and Jansen, 2004). Model structure and the numerical solution of the model provide additional sources of uncertainty (Addiscott et al, 1995;Refsgaard et al, 2006).…”

Long-term fertilization with pig-biogas residues results in heavy metal accumulation in paddy field and rice grains in Jiaxing of China

“…Moreover, comparing the accumulation levels between two years, the HMs in both soil and rice plants increased significantly in the second year, especially for As, Cd, Cu and Zn. The observation that regular PBR fertilization resulted in increasing levels of HMs in soils and crops over time was also reported in some other areas (Brus and Jansen 2004;Hough et al 2004). Therefore, increasing HM accumulation in soil and crops caused by long-term PBR fertilization should be an important issue which needs very careful consideration.…”

“…In this study, the HM levels in the PBR-fertilized soil were found to be within the Chinese soil quality standards (Chinese Environmental Quality Standard for Soils 1995) (Table 1) Table 2). There are many other studies also reporting that biogas slurry fertilization for vegetables, wheat (Triticum aestivum L.) or maize (Zea mays L.) did not result in excessive HM levels in food (Cheung and Wong 1983;Brus and Jansen 2004;Berenguer et al 2008;Islam et al 2010). However, the results of these studies, including the present one, do not imply that HMs in the PBR can be ignored during longterm PBR application.…”