A model to predict concentration enrichment of contaminants on soil adhering to plants and skin

Abstract

Transfer of soil contaminants into the food chain has long been a concern. However, certain aspects of the pathways involved have not been fully investigated. One is the enrichment of contaminant concentrations through physical processes such as size-sorting of soil particles. Fine particles selected from soil by processes such as adhesion onto plants will have much higher contaminant concentrations than the original soil. A saturation kinetics model of the process of soil adhesion to leaf surfaces was developed. The model helps identify the parameters that are least-well known and need experimental support. The ratio of clay and sand wash-off half times was especially important. With nominal values for the input parameters, estimated enrichments agreed well with observations to date, and ranged from slightly over unity for medium- and fine-textured soils to about tenfold for sandy soils. With a few reasonable assumptions, the model was generalised to apply to other soil adhesion scenarios such as adhesion to skin. The generalised model can be applied with minimal need for setting-specific information.

Assessing the control exerted by soil mineralogy in the fixation of potentially harmful elements in the urban soils of Lisbon, Portugal

“…Studies on the effect of particle size on metal concentrations in the solid phase are essential in studies of risk assessment because: (1) metals are preferentially adsorbed by fine particles and to the shaping and implementation of directives is important to know which grain sizes are dominant the immobilization of pollutants, (2) fine particles in PTE's carry an increased risk to health because they are more soluble than the coarse particles that have higher specific surface, (3) fine particles are more likely to cross the gastric mucosa and be adsorbed (Wang et al 2006), (4) the 0-50 l fraction has the greatest likelihood of being accidentally ingested by children (Sheppard 1995), (5) fraction \2 mm is the one that is more likely to be voluntarily ingested by children (Ljung et al 2007). …”

Plant/soil concentration ratios for paired field and garden crops, with emphasis on iodine and the role of soil adhesion

“…Clearly soil adhesion to leaves can predominate over root uptake for insoluble elements. Additionally, as indicated by Sheppard (1995), the soil particles most likely to resiliently adhere to plant leaves are claysized, and for many elements the concentrations on clay-size particles can be 20-fold or more higher than the bulk soil.…”

Appropriate sampling strategy and analytical methodology to address contamination by industry: Part 1. Conceptual model of a sampling design and sampling types

“…Plants developed upon ultramafic formations are known to be adapted to high concentrations of Cr, Ni and Mg as shown in Shallari et al [35]. In contaminated sites the deposition of dust particles rich in heavy metals upon leaves and incorporation within the leaf structure results in higher concentrations in plant leaves as shown by Sheppard [36]. Therefore addition of leaves in autumn/winter to the soils may result in a supplement of heavy metals especially in the top soils.…”

“…According to Nriagu et al [28] and Nriagu and Pacyna [65] at any particular time and location, the amount of inorganic contaminants in the atmosphere depends on: 1. the intensity of the production processes and/or proximity to the source; 2. the amount of contaminants released; 3. the degree of mixing with other particles present in the atmosphere which is determined by meteorological factors; 4. the age (deposition time) and 5. the transportation rate and mechanism of the suspended particulate matter. The large number of variables often leads to large variations in the geographical distribution of pollutants in the atmosphere [28,36]. Moreover air quality both indoors and outdoors influences the respiratory and cardiovascular diseases as stated by Han and Naeher [66].…”