Predicting Metal Uptake and Risk to the Human Food Chain from Leaf Vegetables Grown on Soils Amended by Long-Term Application of Sewage Sludge

Urban waste disposal occurred on fenland to the west of Manchester, England, between 1900 and 1964. The reclaimed fenland, Chat Moss, is now used for mixed arable farming. A total of 1.92 Mt of waste including privy midden, street sweepings, clinkers and slaughterhouse refuse was incorporated into the moss resulting in a modified topsoil with raised pH and reduced organic matter content compared with the subsoil. Elevated levels of potentially toxic elements (PTEs) are observed in the topsoil beyond the typical depth of atmospheric contamination; Cd and As concentrations exceed soil guideline values (SGVs) at 1.8 and 43 mg/kg, respectively. Sequential extraction indicates that waste‐derived Pb, Zn and Ni remain predominantly in the residual fraction, whereas Cu was mainly organically bound. Arsenic was predominately found in oxide and organic matter fractions with Cd in carbonate, oxide, organic matter and residual fractions. Pot trials indicated limited uptake of PTEs by vegetables grown on the waste‐amended soil, with the exception of Cd uptake by lettuce (0.22 mg/kg FW) and Pb uptake by radish (0.16 mg/kg FW), which exceeded current EU limits of 0.2 and 0.1 mg/kg FW, respectively. Hazard quotients (HQs) identified no risks to adults from consumption of vegetables grown in these soils with the exception of lettuce consumption with a HQ of 1.4. Risks to children were slightly greater with HQs >1 for Cd in lettuce, spinach, carrots and onion, As in lettuce, parsley and onion and for Zn in spinach.

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“…, 2004). Values of metal‐specific HQ were calculated according to Equation 1 (Datta & Young, 2005): .…”

Section: Methodsmentioning

confidence: 99%

Does returning sites of historic peri‐urban waste disposal to vegetable production pose a risk to human health? – A case study near Manchester, UK

Atkinson

Young

Tye

et al. 2012

Soil Use and Management

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“…Cadmium uptake by plants as a function of free and Cl-complexed ions in soil pore water was modeled by López-Chuken et al (2010) using a form of FIAM also called the "biotic ligand model" (BLM; Datta and Young 2005;Hough et al 2005). This approach assumes the initial sorption of free metal ions (M 2+ ), or defined metal complex species (e.g., MCl + ), from the solution onto hypothetical plant root sorption sites.…”

Section: Metal Bioavailability and Root Uptakementioning

confidence: 99%

Phytoextraction of Metals: Modeling Root Metal Uptake and Associated Processes

et al. 2014

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IntroductionPhytoextraction is a process which can remove the soluble (bioavailable) metal pool from soil or aqueous solutions using different kinds of terrestrial or aquatic plants. This transport may be divided into three different steps: (1) absorption from the solution (e.g., soil solution), (2) transport to the root xylem, and (3) transport to the shoots (Mench et al. 2009).A modern approach, how to evaluate the extraction potential of selected plants as well as how to plan and design the most effective metal phytoextraction, is the ability to relevantly model this process. There are many studies aimed at the modeling of metal transport. Nevertheless, there is a limited amount of present studies, which are focused on the modeling of the phytoremediation process. In general, developing an applicable model requires sufficient conceptual model description and a fundamental theoretical understanding of the studied system, as well as its experimental equipment and measurement; these are all crucial aspects required to create a relevant simulation of studied problem. This chapter attempts to describe the problems associated with metal phytoextraction modeling. The term "root metal uptake" is crucial for the simulation of phytoremediation of metals, which is a concrete modification of the general term "root uptake." Root uptake is one of the most important processes considered in numerical models because root surfaces represent the first-phase boundaries in nature for nutrients and toxic elements. In order to efficiently model the phytoextraction processes, it is essential to provide information about (1) the spatiotemporal concentration changes of metals in the root-influenced soil and (2) the cumulative uptake of metals per unit length of root over time (Darrah et al. 2006). Root UptakeDetermining water and metal uptake by plant roots and their subsequent translocation into the tissues of the aerial parts is obviously critical for assessing the modeling of phytoremediation options. Because metals are taken up by plants dissolved in water, it is crucial to have information about the transport of water and the hydraulic properties of the roots. Root Water UptakeWater is primarily absorbed by the root hairs and other root zones and then transported to the aerial parts in xylem tissues. Water absorption by the plants is mainly a response to the water potential gradient (from low to high energy) from the rhizosphere to the xylem of the roots. Soil water has a lower total solute concentration than plant water, and hence the osmotic gradient tends to drive water from the soil into the root. The rate of water uptake from the soil depends on rooting density, the hydraulic conductivity of the roots, and the difference between average soil-water suction and root suction. The root hydraulic conductivity is a measure of the amount of water transported by the root in an interval of time at a determinate pressure [mg g et al. 1987). It depends on osmotic potential gradients which result from differences in the composition and t...

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“…The conversion factor (C factor ) was used to convert fresh green vegetable weight to dry weight. Previous studies have used the C factor of 0.085 for all kinds of vegetables [35,36]. In this study, the difference of C factor between the three vegetable species (celery, Chinese cabbage and lettuce) was considered, which is defined as the ratio between dry weight and fresh weight.…”

Section: Risk Characterizationmentioning

confidence: 99%

Environmental impact and site-specific human health risks of chromium in the vicinity of a ferro-alloy manufactory, China

Wang

Chen

Chai

et al. 2011

Journal of Hazardous Materials

101

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Predicting Metal Uptake and Risk to the Human Food Chain from Leaf Vegetables Grown on Soils Amended by Long-Term Application of Sewage Sludge

Cited by 72 publications

References 25 publications

Does returning sites of historic peri‐urban waste disposal to vegetable production pose a risk to human health? – A case study near Manchester, UK

Does returning sites of historic peri‐urban waste disposal to vegetable production pose a risk to human health? – A case study near Manchester, UK

Phytoextraction of Metals: Modeling Root Metal Uptake and Associated Processes

Environmental impact and site-specific human health risks of chromium in the vicinity of a ferro-alloy manufactory, China

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