Strategies to manage the risk of heavy metal(loid) contamination in agricultural soils

Abstract

Soil contamination with heavy metal(loid)s threatens soil ecological functions, water quality and food safety; the latter is the focus of this review. Cadmium (Cd) and arsenic (As) are the toxic elements of most concern for food safety because they are relatively easily taken up by food crops. Rice is a major contributor of both Cd and As intakes to the Chinese population. Contamination and soil acidification are the main causes of high Cd levels in rice grains produced in some areas of southern China. The risk of Cd and As accumulation in food crops can be mitigated through agronomic practices and crop breeding. Liming is effective and economical at reducing Cd uptake by rice in acid soils. Paddy water management can produce opposite effects on Cd and As accumulation. Many genes controlling Cd and As uptake and translocation have been characterized, paving the way to breeding low accumulating crop cultivars through marker-assisted molecular breeding or genetic engineering. It is important to protect agricultural soils from future contamination. Long-term monitoring of anthropogenic additions and accumulation of heavy metal(loid)s in agricultural soils should be undertaken. Mass-balance models should be constructed to evaluate future trends of metal(loid)s in agricultural soils at a regional scale.

Water and soil contaminated by arsenic: the use of microorganisms and plants in bioremediation

“…For reviews on plant responses to As excess, see, e.g. Clemens and Ma ( 2016 ), Kofronova et al ( 2018 ), Zhang et al ( 2018 ), Zhao ( 2020 ), and Wei et al ( 2021 ).…”

“…Obvious ways to alleviate pollutant linkages due to As excess are to avoid sources leading to As contamination and exposure, to select plant species and associated microorganisms for minimising As concentration in edible plant parts, and to reduce As in exposure pathways (Kofronova et al 2018 ; Zhao 2020 ). Physico-chemical technologies, e.g.…”

“…More than 600 As-contaminated sites require remediation in the USA (da Silva et al 2018a(da Silva et al , 2019a. Reducing As accumulation in rice is a top priority in the management of Chinese contaminated soils (Zhao 2020).…”

“…An acute or chronic exposure to As excess can cause many diseases, including various cancer forms. Its presence in water is one main source of contamination, but many studies have demonstrated its presence in fishes and crops from contaminated areas (Carlin et al 2016 ; Jackson et al 2012 ; Manjón and Ramírez-Andreotta 2020 ; Molin et al 2015 ; WHO 2011 ; Zhao 2020 ). In several Chinese provinces, As-contaminated farmland impairs rice production (Li et al 2019b ).…”

“…Various organic arsenicals are reported (Singh et al 2015 ). Soil flooding and aerobic-anaerobic transitions affect As speciation, sorption, and bioavailability in relation to the soil redox status and potential releases due to Fe oxyhydroxide dissolution (Li et al 2019b ; Zhao 2020 ). One option to reduce As exposure in contaminated soils and water is the use of Fe/Mn-based minerals and their derivatives in line with As speciation.…”