Heavy metals in soils and crops in Southeast Asia

Abstract

In a reconnaisance soil geochemical and plant survey undertaken to study the heavy metal uptake by major food crops in Malaysia, 241 soils were analysed for cation exchange capacity (CEC), organic carbon (C), pH, electrical conductivity (EC) and available phosphorus (P) using appropriate procedures. These soils were also analysed for arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) using aqua regia digestion, together with 180 plant samples using nitric acid digestion. Regression analysis between the edible plant part and aqua regia soluble soil As, Cd, Cr, Cu, Hg, Ni, Pb and Zn concentrations sampled throughout Peninsular Malaysia, indicated a positive relationship for Pb in all the plants sampled in the survey (R2 = 0.195, p < 0.001), for Ni in corn (R2 = 0.649, p < 0.005), for Cu in chili (R2 = 0.344, p < 0.010) and for Zn in chili (R2 = 0.501, p < 0.001). Principal component analysis of the soil data suggested that concentrations of Co, Ni, Pb and Zn were strongly correlated with concentrations of Al and Fe, which is suggestive of evidence of background variations due to changes in soil mineralogy. Thus the evidence for widespread contamination of soils by these elements through agricultural activities is not strong. Chromium was correlated with soil pH and EC, Na, S, and Ca while Hg was not correlated with any of these components, suggesting diffuse pollution by aerial deposition. However As, Cd, Cu were strongly associated with organic matter and available and aqua regia soluble soil P, which we attribute to inputs in agricultural fertilisers and soil organic amendments (e.g. manures, composts).

Relationships between Cadmium in Tissues of Cacao Trees and Soils in Plantations of Trinidad and Tobago

“…In addition, it was noted that some of these areas were either prone to flooding during the wet season, with the possibility of Cd contamination from industrial sources [10] [36], or in some cases had a long history of fertilizer applications. Phosphate fertilizers are known to be contaminated with Cd [37] and have contributed to elevated levels of Cd in soil in cacao plantations in Malaysia [38].…”

Photosynthetic activity in relation to chlorophylls, carbohydrates, phenolics and growth of a hybrid Salix purpurea × triandra × viminalis 2 at various Zn concentrations

“…Recently, there has been observed increasing concern about Zn concentration in the soil and water (Zarcinas et al 2004) due to natural and human activities, such as mining and industrial processes, as well as agricultural practicesuse of fertilizers containing various heavy metals (Dudka et al 1996). On the other hand, there has also been reported a deficiency of this element in agricultural areas of India (Singh 2009).…”

Multiscale analysis of heavy metal contents in Spanish agricultural topsoils

“…The characterization of the spatial variability of soil attributes is essential to achieve a better understanding of the complex relations between soil properties, environmental factors and land use (Veldkamp et al, 2001;Yemefack et al, 2005). The problems associated with the characterization of heavy metals in the majority of sites are often due to multiple sources of pollution (Serrano et al, 1984;Boluda et al, 1988;Hanesch et al, 2001;Zarcinas et al, 2004) which can act on different scales.…”