Cd In Rice Grains Research Articles

Heavy metal contamination in soils and food crops around Dabaoshan mine in Guangdong, China: implication for human health

This study was designed to investigate heavy metal (Cu, Zn, Pb, and Cd) contamination levels of soils, vegetables, and rice grown in the vicinity of the Dabaoshan mine, south China. The concentration of Cu, Zn, Pb, and Cd in paddy soil exceeded the maximum allowable concentrations for Chinese agricultural soil. The heavy metal concentrations (mg kg(-1), dry weight basis) in vegetables ranged from 5.0 to 14.3 for Cu, 34.7 to 170 for Zn, 0.90 to 2.23 for Pb, and 0.45 to 4.1 for Cd. The concentrations of Pb and Cd in rice grain exceeded the maximum permissible limits in China. Dietary intake of Pb and Cd through the consumption of rice and certain vegetable exceeded the recommended dietary allowance levels. The status of heavy metal concentrations of food crops grown in the vicinity of Dabaoshan mine and their implications for human health should be further investigated.

Genotypic Difference in Arsenic and Cadmium Accumulation by Rice Seedlings Grown in Hydroponics

ABSTRACT Genotypic differences in arsenic (As) and cadmium (Cd) uptake and their translocation within rice seedlings grown in solution culture were investigated. Arsenic uptake and its translocation differed significantly between eight cultivars. The largest shoot and root As concentrations were found in cultivar ‘TN1’ and ‘ZYQ8’, while cultivar ‘JX-17’ had the lowest As concentration. Arsenic concentration in shoot or root of ‘JX-17’ was about 50% of that in cultivar ‘ZYQ8’. Specific Arsenic uptake (SAU) was found significantly different between rice cultivars, which was about 2-fold higher of ‘ZYQ8’ than that of ‘JX-17’. The Cd accumulation also differed significantly between cultivars. Rice cultivar ‘JX-17’ had the highest ability in Cd uptake, but the lowest ability in Cd translocation from root to shoot. The transfer factor (TF) of Cd had an important effect on Cd accumulation by rice seedlings. Arsenic can competitively inhibit P uptake by rice seedlings, P concentrations in shoots, or roots treated with As were significantly lower than those without As addition. However, the concentrations of P and As were positively correlated within these genotypes. The Cd immobilization by cell wall was an important mechanism for Cd detoxification. The cell wall bound 21–44% of total Cd in shoots and 25–59% of total Cd in roots of these tested genotypes. The genotypic differences in As and Cd uptake and translocation within rice seedlings provide the possibility of selecting and breeding genotypes and /or cultivars with reduced levels of As and Cd in rice grains.

Foliar application of two silica sols reduced cadmium accumulation in rice grains

In the present study, pot experiments were conducted to investigate the effects of foliar application of two silica (Si) sols on the alleviation of cadmium (Cd) toxicity in contaminated soil to rice. Results showed that the foliar application of Si sols significantly increased the dry weight of grains (without husk) and shoots in rice grown in Cd contaminated soil, whereas the Cd concentration in the grains and shoots decreased obviously. The total accumulation of Cd in rice grains also decreased with the application of both of the Si sols, but no significant effect was found on the Cd accumulation in the shoots. For the optimal effect, Si-sol-B should be foliar applied at the tillering-stage during rice growth. The mechanism of Si foliar application to alleviate the toxicity and accumulation of Cd in grains of rice may be related to the probable Cd sequestration in the shoot cell walls.

Bioavailability of Cd in a soil–rice system in China: soil type versus genotype effects

Human exposure to toxic heavy metals via dietary intake is of increasing concern. In this regard, the bioavailability of heavy metals in the soil–crop system is considered to be a key factor controlling plant uptake and, therefore, public health risk through food chain transfer [J. Environ. Sci. Health B 34(4) (1999) 681]. In 2002, a pot experiment was conducted to elucidate the relative significance of soil types and rice genotype on the bioavailability, uptake and partitioning of Cd by two rice cultivars with distinct affinity for Cd. The results indicated that the total uptake of Cd and accumulation in grain was dependent on both soil type and genotype effects. Cd spiking enhanced high Cd uptake and partitioning in grain. Inherent differences in soil type effecting Cd bioavailability were less significant under the Cd spiking regime as compared to non-Cd spiking. In the case of Soil-P, with low Cd bioavailability as indicated by the comparatively lower MgCl2 extractable Cd, differences in metal affinity between genotypes dominated uptake. Conversely, inherent differences in soil type affecting Cd bioavailability dominated uptake in the low metal affinity cultivar treatments. Under the experimental conditions evaluated, the positive interaction between soil type and genotype results in elevated levels of Cd in rice grain with the Cd values exceeding the Chinese food guideline limit of 0.2 mg kg−1. The results indicated that Cd bioavailability and plant uptake is dependent on soil chemical and physical properties affecting Cd mobility, rice genotype and soil pollution status. The results further suggested that caution should be paid to rice production with the new high metal affinity genotypes on soils with inherent Cd bioavailability as with acidic Red Soils of Jiangxi Provinces, China.