Arsenic, cadmium, and lead pollution and uptake by rice (Oryza sativa L.) grown in greenhouse

Abstract

Purpose Hunan province is well-known for its extensive base-metal extraction and smelting industries. However, the legacies of excavation operations, transportation, and selective smelting activities within Hunan have resulted in the generation of large quantities of mine wastes, which will become the sources of metal contamination in the environment. Thus, there is an increasingly important health issue underlying the study of arable land pollution and transfer of As, Cd, and Pb in the paddy soil-rice system. Materials and methods Paddy soils collected from miningand smelting-impacted areas in Hunan province and rice seed (Oryza sativa L. cv Jia Hua-1) were used for pot experiments under greenhouse conditions. One 30-day-old seedling was transplanted into one pot containing 5.0 kg pretreated soil. At harvest, rice grains and shoots were washed with distilled water to remove surface soil, and oven-dried at 65°C for 96 h until a constant weight was reached. Roots were washed carefully with distilled water for the next process of extracting iron plaque using dithionite-citrate-bicarbonate solution. Total concentrations of As, Cd, and Pb in soil and rice plant tissues were measured by inductively coupled plasma mass spectrometer.Results and discussion Total concentrations of As, Cd, and Pb in the soils collected from 12 mining-and smeltingimpacted areas in Hunan province were much higher than Hunan background values and exceeded the maximum concentration limit for soils set by the Ministry of Environmental Protection. The yields of rice grain from Pb/Zn mining and smelting sites were negatively correlated to overall pollution scores. Distributions of As, Cd, and Pb in rice plant followed: root >> shoot > husk > whole grain. About 30.1-88.1% of As, 11.2-43.5% of Cd, and 14.0-33.9% of Pb were accumulated in iron plaque on root surfaces. Conclusions High concentrations of As, Cd, and Pb are observed in paddy soils from mining-and smeltingimpacted areas in Hunan province, indicating those paddy soils suffer serious combined heavy metal contamination. In particular, Cd is the dominant contaminant followed by As and Pb in paddy soils from most locations. The distributions of As, Cd, and Pb in rice tissue were: root >> shoot > husk > whole grain. Concentrations of Pb in all whole grain and of As and Cd in 50% of whole grain samples exceeded Chinese Hygienic Standard values for food.

Mitigating heavy metal accumulation into rice (Oryza sativa L.) using biochar amendment — a field experiment in Hunan, China

“…The high levels of Cd, Zn, Pb, and As contained in iron plaque supports the general consensus that iron plaque has a high adsorption capacity for metal(loid)s (Liu et al 2006;Lei et al 2011). However, iron plaque sequestered less Cd and Pb after BCs amendment though Zn and As concentrations in iron plaque were not significantly influenced (Fig.…”

The effects of biochars from rice residue on the formation of iron plaque and the accumulation of Cd, Zn, Pb, As in rice (Oryza sativa L.) seedlings

“…However, this extra iron plaque sequestered more Pb but not Cd, Zn and As (Fig. 2), despite the general consensus that iron plaque has a high adsorption capacity for all metals (Liu et al, 2008;Lei et al, 2011). For Cd and Zn, this is likely attributable to their C pw decreasing after biochar additions (Fig.…”

“…This iron plaque exhibits a high capacity to sequestrate certain metals. The proportion of As, Cd, and Pb distributed in iron plaque on rice root surface could reach 88%, 43% and 33% respectively (Lei et al, 2011). The presence of iron plaque on root surfaces has been reported to reduce the uptake of metals by plants because of the high adsorption capacity of its iron hydroxide functional groups (Greipsson and Crowder, 1992;Batty et al, 2000;Liu et al, 2011).…”

Combined effect of rice genotypes and soil characteristics on iron plaque formation related to Pb uptake by rice in paddy soils

“…Liu et al (2004) reported that the As sequestrated by iron plaques (i.e., dithionite-citrate-bicarbonate [DCB] extractable As) on root surfaces was about 75-89 % of the total rice plant As and suggested that iron plaques may act as a barrier to prevent As absorption and translocation by rice plants. More recently, Lei et al (2011) showed that As, Cd, and Pb accumulations in iron plaques on the root surface relative to rice plant total accumulation reached about 88, 44, and 34 %, respectively. It has been suggested that iron plaques on rice roots could provide a barrier to soil Pb stress and increase sequestration of Pb on the rice root surface (Liu et al 2011), and this has been further supported by Zheng et al (2012) who found that iron plaques sequestered much more Pb than Cd, Zn, and As.…”