Metal (Loid)s in Farmland Soils and Strategies to Reduce Bioavailability

Abstract

High concentrations of heavy metal (loid)s (HMs) in farmland soils reduces crop yield and contaminates the food chain. Exposure to HMs in the diet results in several adverse health effects such as cancer, reproductive health problems and cardiovascular diseases. Understanding the origin and fractionation of these toxic substances will provide direction for reducing their bioavailability in contaminated farmland soils. HMs are added to farmland soils through activities such as irrigation, organic and inorganic fertilization, pest control, and mining. Weathering of parent material and atmospheric deposition can also increase the levels of HMs in the soil. Fractionation of HM contaminated soils provides information on availability of HMs such as Pb, Cd, As, Cr and Cu to soil biota and plants. Several studies have reported that Pb is mostly associated with Fe and manganese oxides (reducible fraction) while Cd is mostly associated with the most mobile fraction (exchangeable fraction). The application of organic and inorganic soil amendments such as vermiculite, zeolite, composts and crop residue to contaminated farmland soils converts HMs from the plant available fractions to the less mobile fractions. HM resistant microbes can change HMs to a less mobile fraction or less mobile oxidation state. The combination of HM resistant microbes, HM tolerant plants, and soil amendments can be used to reduce mobility of HMs in contaminated farmlands. Capsule:The mobility of heavy metal (loid)s in polluted farmland soils depends strongly on its association with soil components.

Impact of Seasonal Variations and Oil Activities on the Total Concentrations, Geochemical Fractions, And Human Health Problems of Trace Metals in Soils Within the Oil-Bearing Communities of South-South Region of Nigeria

“…Table 4 indicates that, V occurred mostly as oxides of Fe and Mn in the studied soils in the dry and rainy seasons. This is similar to the results obtained by Agnieszka and Barbara (2012) and Fayiga and Nwoke (2017). The separation of V into the various soil fractions varied as follows: Red > Aex > Ox > Res.…”

Health risk assessment of toxic metal(loids) (As, Cd, Pb, Cr, and Co) via consumption of medicinal herbs marketed in Malawi

“…The concentrations of As observed in Malawian medicinal herbs in this study were compared to those reported in medicinal herbs from other African countries. For Moringa oleifera , the results revealed that the mean As concentration obtained in this study (range: 0.048–0.078 mg kg −1 ) fell within the range reported in Ghana (0.06–2.04 mg kg −1 ) [33] , but it was significantly lower than that from Nigeria (range: 0.17–1.21 mg kg −1 ) [2] , [27] , [34] , Ethiopia (range: 0.24–1.11 mg kg −1 ) [2] , [35] , [36] and Uganda (range: 0.29–0.99 mg kg −1 ) [2] , [28] . It is important to note that the US Food and Drug Administration (FDA) has established a maximum contaminant level (MCL) of 3.00 mg kg −1 for As in herbs and spices [37] .…”

Bio-based resources: systemic & circular solutions for (agro)environmental services

“…It was recorded that the ash-sewage sludge mixture can substantially enhance soil fertility, increase plant biomass and uptake of potassium and magnesium. However, even stabilised and aged BS are often (over)loaded with a range of persistent toxic (i) inorganic (metals/metalloids, metallic nanoparticles) 62 and (ii) emergent organic (furans, halogens, nonylphenols and nonylphenol ethoxylates, polyaromatic hydrocarbons, linear alkylbenzenesulfonates polychlorinated biphenyls, polychlorinated dibenzo- p -dioxins) contaminants, 44 hardly to be immobilised or removed from the BS matrix.…”