Distribution Of Cadmium In Soils Research Articles

The distribution of cadmium in soil and cacao beans in Peru

Peru is the eighth largest producer of cacao beans globally, but high cadmium contents are constraining access to international markets which have set upper thresholds for permitted concentrations in chocolate and derivatives. Preliminary data have suggested that high cadmium concentrations in cacao beans are restricted to specific regions in the country, but to date no reliable maps exist of expected cadmium concentrations in soils and cacao beans. Drawing on >2000 representative samples of cacao beans and soils we developed multiple national and regional random forest models to develop predictive maps of cadmium in soil and cacao beans across the area suitable for cacao cultivation. Our model projections show that elevated concentrations of cadmium in cacao soils and beans are largely restricted to the northern parts of the country in the departments of Tumbes, Piura, Amazonas and Loreto, as well as some very localized pockets in the central departments of Huánuco and San Martin. Unsurprisingly, soil cadmium was the by far most important predictor of bean cadmium. Aside from the south-eastern to north-western spatial trend of increasing cadmium values in soils and beans, the most important predictors of both variables in nation-wide models were geology, rainfall seasonality, soil pH and rainfall. At regional level, alluvial deposits and mining operations were also associated with higher cadmium levels in cacao beans. Based on our predictive map of cadmium in cacao beans we estimate that while at a national level <20 % of cacao farming households might be impacted by the cadmium regulations, in the most affected department of Piura this could be as high as 89 %.

Content and Distribution of Cadmium in Soil and Fluvial Sediments in the Sea-Land Interaction Zone

Cadmium pollution poses a threat to human health. The examination of spatial distribution of Cd in soils can be used to assess the risks posed to humans and the environment. The enrichment characteristics and variation rules of heavy metal cadmium in the soil were revealed by analyzing the concentration and fractions of Cd in the soil at different depths in the sea-land interaction zone. The results showed that: ① the concentration of Cd in the surface water of Nansha was lower than 0.0001 mg ·L-1, and the physical and chemical properties of river sediments showed spatial differences with the boundary of "Shang Heng-li River". Cd was mainly deposited in the north of the "Shang Heng-li River", with the mean total Cd of 2.71 mg ·kg-1. The total Cd in the sediment of the "Shang Heng-li River" and the rivers south of it were 0.062-0.39 mg ·kg-1, which caused minimal harm to the marine environment. ② The content of Cd in the soil profile gradually decreased with an increase in soil burial depth. The median content of Cd in the five layers, including 0-20 cm, 20-50 cm, 50-90 cm, 90-140 cm, and 140-200 cm, were 0.51, 0.50, 0.45, 0.42, and 0.33 mg ·kg-1, respectively, and the dispersion degree gradually decreased with an increase in buried depth; the vertical migration amount and migration depth of Cd increased significantly in soils with pH less than 5. ③ The residual Cd in the soil accounted for approximately 40%, and the trend was typically flat with a change in buried depth. The median proportion of acid soluble Cd was consistent with the change in pH and increased with an increase in the buried depth of the profile, while the median proportion of reducible Cd was consistent with the change in iron and manganese content, and decreased with an increase in buried depth of section. These results have important guiding significance for the regional prevention and control of Cd pollution in farmland surrounding cities and the treatment and remediation of polluted soil.

Distribution of cadmium in soils along the altitude of riparian zone(Fengdu-Zhongxian section) in the Three Gorges Reservoir region

Distribution of cadmium in soils along the altitude of riparian zone(Fengdu-Zhongxian section) in the Three Gorges Reservoir region

The source and distribution of cadmium in soils on a regularly fertilised hill-country farm

Cadmium (Cd) accumulation in New Zealand pastoral soils is often attributed to application of Cd-containing phosphatic fertiliser. Other sources may, however, contribute to the Cd load of the topsoil, e.g. atmospheric deposition and residues from the clearing and burning of native bush prior to the establishment of pasture. A study was conducted to evaluate the source of Cd to pastoral soils by comparing Cd loads to a 30 cm depth in 2 soil types at 2 pedologically matched sites: one fertilised and the other unfertilised. The Cd load in the fertilised soils (420 and 482 g/ha) was markedly greater than in their unfertilised counterparts (16 and 189 g/ha). A review of local pollution sources discounted atmospheric deposition as a potential source of this additional Cd. Estimates of Cd concentrations in the above-ground biomass of the native bush indicated a Cd store of probably &lt;10 g/ha. Cadmium stores in the native bush and additions of Cd to the topsoil following clearing and burning of native bush were unlikely to account for differences in Cd load between the fertilised and unfertilised sites. Estimates of Cd additions from phosphatic fertiliser comfortably accounted for the difference, and indicated that fertiliser was the main Cd source for these soils.

The content and distribution of cadmium in soils as influenced by the soil properties

The total and soluble cadmium contents of 29 natural, uncultured, unpolluted soils from the province of Salamanca (Spain) were determined. The two forms of the metal were found to occur at concentrations over the ranges 0.07-0.33 and 0.004-0.061 μg/g, respectively. The total Cd contents found were somewhat low relative to reported values for worldwide soils in general and European soils in particular. No significant correlation was found between the total and soluble Cd contents or between the former and any chemical parameters of the soils. On the other hand, there was a highly significant correlation ( P < 0.001) between soluble Cd and the pH, sum of bases and exchangeable Ca, as well as a significant correlation ( P < 0.01) between soluble Cd and the cation exchange capacity, degree of saturation and exchangeable Mg content of the soils. Finally, there were virtually no similarities in the distribution patterns of Cd and the other soil parameters in a given soil profile.