Cadmium Content In Rice Research Articles

Applying conditioners to address the issues of carbon loss and cadmium pollution in the karst paddy-oil crop system

The fragile ecosystem and unique parent material in the karst region lead to severe carbon loss and cadmium pollution. Additionally, the rice-oilseed rotation system exacerbates the accumulation of cadmium in crops. Therefore, it is necessary to find a sustainable land use approach that ensures crop quality while promoting soil carbon sequestration. This article provides an overview of cutting-edge technologies to enhance soil carbon sequestration capacity, and it discovers that the application of amendments has a significant effect on reducing cadmium content in crops and improving soil organic carbon levels. Through experimental analysis, The results indicate that the conditioner in group T4 (Humic acids) can effectively passivate cadmium elements in the soil, reducing the cadmium content in rice and rapeseed tissues. Overall, our research indicates that humic acid amendments not only enhance soil carbon sequestration capacity but also significantly reduce cadmium content in crops and increase crop yields. These findings highlight the significant value of humic acid amendments in the rice-oilseed rotation system in the karst region, providing scientific evidence and theoretical support for promoting sustainable development in the area.

Machine learning method for predicting cadmium concentrations in rice near an active copper smelter based on chemical mass balance

Identification the sources of heavy metals can effectively control and prevent agricultural soil pollution. Here we performed a three-year mass balance study along a gradient of soil pollution near a smelter to quantify the potential contribution and net cadmium (Cd) fluxes and predict Cd concentration in rice grains by multiple regression (MR) and back propagation (BP) neural network. The Cd inputs were mainly from the irrigation water (54.6–60.8%) in the moderately polluted and background sites but from atmospheric deposition (90.9%) in the highly polluted site. The Cd outputs were mainly from the surface runoff (55.8–59.5%) in the moderately polluted and background sites, but from Sedum plumbizincicola phytoextraction (83.6%) in the highly polluted site. The soil Cd concentrations, the annual fluxes of atmospheric deposition, pesticides and fertilizers, irrigation water, surface runoff, and leaching water were selected as the dependent factors to predict Cd concentrations in rice grains. The genetic algorithms (GA)-BP neural network model gives the best prediction accuracy compared to the BP neural network model and multivariate regression analysis. The major implication is that the health risks through the consumption of rice can be rapidly assessed based on the Cd concentrations in rice grains predicted by the model.

The lead and cadmium content in rice and risk to human health in China: A systematic review and meta-analysis.

Numerous studies have investigated concentrations of lead (Pb) and cadmium (Cd) in rice in China, but have come to divergent conclusions. Therefore we systematically reviewed and meta-analyzed the available evidence on levels of Pb and Cd in rice in different regions of China in order to assess the potential risk to human health. The meta-analysis included 24 studies of Pb levels and 29 studies of Cd levels, published in 2011-2021. The pooled Pb concentration in rice was 0.10 mg per kg dry weight (95% CI 0.08-0.11), while the pooled Cd concentration was 0.16 mg per kg dry weight (95% CI 0.14-0.18). These levels are within the limits specified by national food safety standards. However, the total target hazard quotient for both metals exceeded 1.0 for adults and children, suggesting that rice consumption poses a health risk.

Health risk assessment using in vitro simulation in assessing bioavailability of cadmium in rice from main producing areas across China

Rice is a recognized source of cadmium (Cd) exposure. In this study, a total of 102 rice samples were obtained from main producing rice regions of China, and the bioavailability of Cd in rice were assessed by using an in vitro digestion method combined with a Caco-2 cell monolayer model. The results revealed that the average (range of) concentration of Cd in the rice samples was 0.2840 (0.0123-2.4710) mg/kg, and the average (range of) bioavailability of Cd in the rice samples was 23.94% (7.47-39.73%). We analyzed the recent rice consumption data and calculated the target hazard quotients (THQs) to evaluate the noncarcinogenic health risk of Cd in rice consumption for adults and children, respectively. We suggested that the most of investigated regions showed low risks of Cd in rice for general population, and the regions of Cd in rice near the limit deserves might be attracted more attention after taking bioavailability into account. PRACTICAL APPLICATION: The cadmium content of rice itself will affect its corresponding bioavailability to a certain extent. By studying the in vitro bioavailability of cadmium rice with different pollution levels, it is helpful for the dose selection of animal experiments or toxicity tests, and finally, we may provide some references for the establishment of appropriate treatment scheme of rice Cd poisoning.

Nitrogen application practices to reduce cadmium concentration in rice (Oryza sativa L.) grains.

Cadmium (Cd) pollution in paddy soils creates challenges in rice grain production, thereby threatening food security. The effectiveness of different base-tillering-panicle urea application ratios and the combined basal application of urea and Chinese milk vetch (CMV, Astragalus sinicus L.) in minimizing Cd accumulation in rice grains was explored in a Cd-contaminated acidic soil via a field experiment. The results indicated that under similar nitrogen (N) application rates, an appropriate amount of urea applied at the panicle stage or the combined basal application of urea and CMV decreased Cd absorption by rice roots and its accumulation in rice grains, as compared with that of conventional N application (control). Furthermore, under a 3:4:3 base-tillering-panicle urea application ratio or under a high basal application of CMV (37,500kg hm-2), Cd concentrations in brown rice were significantly lower (40.7% and 34.1%, respectively) than that of control. Cadmium transport coefficient from root to straw was significantly higher than that of control when an appropriate amount of urea was applied at the panicle stage or when urea and CMV were applied basally, whereas the Cd transport coefficient from straw to brown rice was relatively lower. Moreover, soil pH, or the CEC and CaCl2-Cd concentrations under different N fertilizer treatment was not significantly different. However, the rice grain yield increased by 29.4% with basal application of a high CMV amount compared with that of control. An appropriate amount of urea applied at the panicle stage or the combined basal application of urea and CMV decreased Cd absorption by rice roots and inhibited its transport from straw to brown rice, thus reducing Cd concentration in brown rice. Therefore, combined with the key phase of Cd accumulation in rice, a reasonable urea application ratio or a basal application of high CMV amounts could effectively reduce Cd concentration in brown rice.

UJI KADAR CEMARAN LOGAM BERAT KADMIUM DARI DALAM TANAH SAWAH DAN BERAS (OryzasativaL.) DI KELURAHAN LAPE KECAMATAN AESESA KABUPATEN NAGEKEO

Cadmium heavy metal is one of the heavy metals that is harmful to human health and is widely found in agricultural land with the use of phosphorus-based fertilizers such as in rice fields. The research was conducted in Lape Village, Aesesa District, which produces Inpari and Ciherang varieties of rice. Rice samples were taken directly from the farmers who cultivate the two types of plants. Analysis of cadmium from rice samples using the Atomic Absorption Spectrophotometry (AAS) method and comparing it with the maximum limit of heavy metal contamination in rice set by the Indonesian National Standard (SNI) 6989.16:2009 . The results showed that the cadmium content in rice was < 0.001 ppm – 0.001 ppm. The content of cadmium in the rice is still below the set standard, this is closely related to soil conditions such as soil pH, C-organic at the study site, where high organic matter conditions affect low cadmium content.

Main Control Factors of Cadmium Content in Rice in Carbonate Rock Region of Guangxi Based on the DGT Technique

In order to explore the main controlling factors of Cd enrichment in rice under a geological high background in the Guangxi carbonate rock area, this study was based on rice grain-root soil samples from the carbonate rock areas in the southwest and north of Guangxi. Combined with diffusive gradients in thin films technology (DGT), the relationship between soil pH, organic matter, cation exchange capacity (CEC), DGT-Cd, and ω(rice-Cd)-BCF value in rice grains was analyzed and discussed. The main factors were determined by principal component analysis, and a quantitative model was established. The results showed that the average value of ω(soil-Cd) was 0.975 mg·kg-1, and the over-standard rate was 33.33%; the average value of ω(rice-Cd) was 0.020 mg·kg-1, and the average BCF value was 0.038, and the over-standard rate of Cd content in rice grains was 4.2%. The content of Cd in paddy soil was high, but bioavailability was low in the study area. The BCF value of rice grains in the study area was significantly negatively correlated with soil pH and cation exchange capacity at the level of 0.01, positively correlated with DGT-CD at the level of 0.01, and negatively correlated with organic matter at the level of 0.05. The results of principal component analysis showed that the total amount of Cd in the soil, pH, and DGT-Cd were the main factors affecting the accumulation of Cd in rice in the Guangxi carbonate rock area. Taking the total amount of Cd in the soil, pH, and DGT-Cd as variables, the fitting equation of BCF value of rice grains in the Guangxi carbonate rock region was established, and the determination coefficient of the model was 0.717, which could better predict the content of Cd in rice grains in this region.

Lime-Phosphorus Fertilizer Efficiently Reduces the Cd Content of Rice: Physicochemical Property and Biological Community Structure in Cd-Polluted Paddy Soil.

Due to the biomagnifying effect in the food chains, heavy metals will cause serious harm to the food produced in paddy soil, and then threaten human health. The remediation of soil heavy metals by the addition of amendments is a common method. However, the combination of the two amendments has been less studied and its effect is unknown. In this study, we investigated the effects of different concentrations of a lime and calcium-magnesium phosphate (CMP) amendments metal availability and paddy soil bacteria biodiversity. The experiment proves that the addition of 0.5 and 1.0‰ amendment can effectively reduce cadmium (Cd) availability and the cadmium content in rice to be below 0.2 mg/kg, meeting the national food safety level. The results demonstrate that increasing pH and phosphorous (P) in soil were two important factors decreasing available cadmium. Furthermore, biodiversity analysis of the treated soil showed that the amendment increased biodiversity. Proteobacteria and Chloroflex were the most abundant bacteria at the phylum level, followed by Acidobacterium and Nitrospirae. The abundance of Bacterodietes-vadinHA17, Syntrophaceae, and Thiobacillus increased as phosphorous increased. Cadmium passivation might induce those species.

NIR spectroscopy coupled with chemometric algorithms for the prediction of cadmium content in rice samples

Fast determination of heavy metals is necessary and important to ensure the safety of crops. The potential of near-infrared spectroscopy coupled with chemometric technology for quantitative analysis of cadmium in rice was investigated. A total of 825 rice samples were collected and scanned by NIRS. The Kennard–Stone method was applied to divide the samples into calibration and validation sets. Before modeling, the spectrum was preprocessed using first derivation to reduce the baseline shift. Different chemometric tools such as interval partial least squares, moving window partial least squares, synergy interval partial least squares, and backward interval partial least squares were proposed to extract and optimize spectral interval from full-spectrum data. The performance of the calibration models generated on the basis of different regression algorithms was compared and evaluated. Results showed that the PLS models based on four chemometric algorithms outperformed the full-spectrum PLS model. Among the tools, biPLS performed better with the optimal subinterval selection. The root-mean-square error of prediction and correlation coefficient (R) of the biPLS model were 0.2133 and 0.9020, respectively. In addition, the low root-mean-square error of cross-validation was obtained in biPLS, which was 0.1756. NIRS technology combined with biPLS could be considered as an effective and convenient tool for primary screening and measuring of cadmium content in rice. In comparison with classical methodologies, this new technology was beneficial because of its eco-friendliness, fast analysis, and virtually no sample preparation required.

Analisis Ketersediaan Kadmium di Tanah dan Beras Yang Berasal dari Desa Detusoko Barat

Cadmium is a heavy metal that is widely found in agricultural land because of the frequent use of inorganic phosphorus fertilizers. The use of high phosphorus inorganic fertilizers is also used by farmers who cultivate rice in Detusoko Barat Village. Therefore, research has been carried out with the aim of knowing the cadmium content in paddy soil and rice and its comparison with the minimum limit of cadmium in rice and soil. This research is survey research, in which the determination of soil and rice samples using a purposive sampling method. From this method, the soil samples taken are rice fields cultivating Palembang, Bengawan and Kental rice varieties. And the rice samples taken were rice from the three varieties. The variables observed were cadmium from the soil and rice and soil pH. The results showed that the cadmium content in Palembang rice soil was 0.015 ppm, Bengawan 0.006 ppm, and thick 0.001 ppm, while the results of the research on cadmium content in Palembang rice were 0.007 ppm, Bengawan rice was 0.008 ppm, and thick rice was 0.006 ppm. Where the cadmium content in rice is still below the minimum limit that has been set.

Application of Laser-Induced Breakdown Spectroscopy in Detection of Cadmium Content in Rice Stems.

The presence of cadmium in rice stems is a limiting factor that restricts its function as biomass. In order to prevent potential risks of heavy metals in rice straws, this study introduced a fast detection method of cadmium in rice stems based on laser induced breakdown spectroscopy (LIBS) and chemometrics. The wavelet transform (WT), area normalization and median absolute deviation (MAD) were used to preprocess raw spectra to improve spectral stability. Principal component analysis (PCA) was used for cluster analysis. The classification models were established to distinguish cadmium stress degree of stems, of which extreme learning machine (ELM) had the best effect, with 91.11% of calibration accuracy and 93.33% of prediction accuracy. In addition, multivariate models were established for quantitative detection of cadmium. It can be found that ELM model had the best prediction effects with prediction correlation coefficient of 0.995. The results show that LIBS provides an effective method for detection of cadmium in rice stems. The combination of LIBS technology and chemometrics can quickly detect the presence of cadmium in rice stems, and accurately realize qualitative and quantitative analysis of cadmium, which could be of great significance to promote the development of new energy industry.

Variations in Cadmium Concentrations in Rice and Oxidation-Reduction Potential at the Soil Surface with Supplementation of Fermented Botanical Waste-based Amendment in Large-scale Farmland.

We monitored the relationship between the cadmium (Cd) concentration uptake of rice and the oxidation-reduction potential (ORP) at the soil surface with the supplementation of fermented botanical waste-based amendment (FBWA), an organic fertilizer prepared from woody and food wastes. This study was carried out for 3 years in the western part of Jiangsu Province, China. It was found that the Cd concentration taken up by rice was correlated to a decreased the ORP of the cultivated soil. The yield of rice was ∼1.20 times higher than that of the control plot. The effects of reducing the Cd content in rice and increasing the rice yield remained for 2 years after FBWA application. Finally, Cd was immobilized in the soil with adsorption to FBWA or the decomposed products. The ORP measurement during rice cultivation might be a key index to predict the suppression effect of Cd uptake into the rice or limitation of the sustainable effect by the FBWA.

Control of Cadmium Migration and Transformation in Alkaline Paddy Soil-Rice Using Cotton Stalk Biochar

We investigated the effects of cotton stalk biochar addition on the soil nutrient characteristics of alkaline paddy soil and the migration and transformation of cadmium in a soil-rice system. An outdoor pot experiment was conducted with Tefengyou 2 rice as the testing material. We added cotton stalk biochar (0%, 1%, 2.5%, and 5%) in the alkaline paddy soil with cadmium content of 0, 1, 4, and 8 mg·kg-1. After rice harvesting, the effects of different concentrations of cotton stalk biochar on alkaline soil physical and chemical properties, cadmium enrichment and transfer in rice, and the occurrence of cadmium in soil were analyzed under different concentrations of cadmium stress. The results showed that ① adding cotton stalk biochar can effectively increase soil nutrient (P<0.05). After the addition of cotton stalk biochar, the organic matter increased by 25.74%-47.53%, and the available potassium content increased by 3.16-4.25 times. ② Cotton stalk carbon can reduce the cadmium content in soil and rice, especially after the application of 5% cotton stalk carbon, The cadmium content of brown rice at Cd4 and Cd8 concentrations decreased from 0.31 mg·kg-1 and 0.43 mg·kg-1 to 0.15 mg·kg-1 and 0.10 mg·kg-1, respectively, reaching the national standard. Cotton stalk biochar can significantly reduce the enrichment and transfer coefficient of cadmium in soil-rice systems and can increase the cadmium content in the residual cadmium but decrease the acid extractable cadmium, reducible cadmium, and oxidizable cadmium content (P<0.05). ③ Soil pH, conductivity, and nutrient indicators were significantly negatively correlated with cadmium content in rice and acid extractable cadmium, reducible cadmium, and oxidizable cadmium content in soil and were positively correlated with cadmium content in residual cadmium. The above results indicate that the application of cotton stalk biochar can significantly improve the soil nutrient of alkaline cadmium-contaminated paddy soil, and the application of cotton stalk biochar has a significant control effect on the migration and transformation of cadmium in alkaline soil and rice.

Silicon application improved the yield and nutritional quality while reduced cadmium concentration in rice.

Silicon (Si) is an essential nutrient for rice, but its effects on the yield and quality of rice under heavy metal stress remain uncertain. In this study, two typical paddy soils (acidic and calcareous purple soils) in the western region of Chongqing were selected for field plot experiment, with the purpose of understanding the effects of Si implementation methods on grain yields and cadmium (Cd) uptake, transport, and accumulation in the grain of a hybrid rice (Oryza sativa L, Changliangyou 772). Four treatments were set for the purposes including soil-based Si application, foliar spray of Si alone, foliar spray of selenium (Se)-containing Si fertilizer, and a control without Si application, respectively. The results indicated that the Si applications reduced Cd contents in brown rice by 11.45~51.85% in the slightly Cd-contaminated acidic purple soil (pH = 4.77, soil total Cd content 0.413 mg kg-1) and 26.93~43.77% in the purple calcareous paddy soil (pH = 7.77) with similar Cd-polluting levels. It is worth noting that the Cd content of conventional fertilized rice exceeds the Chinese National Food Safety Standard limit (0.2 mg kg-1, GB2762-2017) in the slightly Cd-contaminated acidic purple soil, and foliar spray treatments showed most effective effects that meets the safety threshold standard. Soil-based Si application reduced Cd accumulation in rice grains mainly by inhibiting the translocation of Cd from stem to the rice grain or root to stem, while foliar sprays of Si mainly by inhibiting the translocation of Cd from stem to brown rice. Si applications increased the rice yield by 17.15 to 25.45% in calcareous paddy soil with foliar spray being the best, while no significant yield increase was found in acidic paddy soil. Si and Se-containing Si fertilizer improved the nutritional quality of rice grain as indicated by the increases of Se, Si, and protein contents and the significant decreases of Cd contents in the rice grains. The comprehensive effects in improving the rice quality follow the order of foliar spray of Se-containing Si fertilizer > foliar spray of Si alone > soil-based Si application. Thus, foliar spray Si-containing fertilizer could be helpful in increasing rice yield while reducing the Cd uptake in rice grains, which might be a feasible approach in controlling Cd entry into the human body via crops.

Isolation, characterization and inoculation of Cd tolerant rice endophytes and their impacts on rice under Cd contaminated environment

Cadmium (Cd) contamination in paddy soil becomes increasingly prominent in recent years, which endangers the safe production of food crops. Cd-tolerant endophytes are ideal mediators for decreasing Cd content in rice plants, but their effects on the rice endophytic microbial community and gene expression profile have not yet been well elucidated. In this study, 58 endophytic bacteria from rice seeds were isolated and characterized. Five strains of them were selected based on their potential growth-promoting traits and strong Cd tolerance that could grow well under 4 mM Cd2+. By 16S ribosomal RNA (rRNA) identification, these five strains were designated as Enterobacter tabaci R2-7, Pantoea agglomerans R3-3, Stenotrophomonas maltophilia R5-5, Sphingomonas sanguinis R7-3 and Enterobacter tabaci R3-2. Pot experiments in relieving Cd stress in rice plants showed that the S. maltophilia R5-5 performed the strongest potential for reducing the Cd content in root and blade by 81.33% and 77.78%, respectively. The endophytic microbial community diversity, richness and composition were significantly altered in S. maltophilia R5-5 inoculated rice plants. Reverse-transcription qPCR (RT-qPCR) showed that the expression of Cd transporters, OsNramp5 and OsHMA2, were down-regulated in S. maltophilia R5-5-innoculated rice roots. The results indicate that the inoculation of endophytic bacteria S. maltophilia R5-5 provides a reference for alleviating the heavy metal contamination in paddy fields and can be a better alternative for guaranteeing the safe production of crops. Changes in the relative abundance of Cd-resistant microorganisms and the expression of Cd transporters might be the intrinsic factors affecting cadmium content in rice.

Nanoscale zerovalent iron particles for magnet-assisted soil washing of cadmium-contaminated paddy soil: proof of concept

Environmental contextCadmium contamination in paddy soil can lead to elevated cadmium concentrations in rice, potentially affecting millions of rice consumers worldwide. This study used nanoscale zerovalent iron to sequester cadmium from soil before using magnetic separation to retrieve cadmium-sorbed particles from the soil slurry. This approach hypothetically resulted in a 97% reduction of cadmium levels in rice, rendering the rice safe for human consumption. AbstractCadmium (Cd) exposure causes serious health effects, including osteopenia, itai-itai disease, kidney disease and cancer. Millions of people are at risk of Cd-contaminated rice consumption resulting from Cd-contaminated paddy soil. While several soil restoration techniques, including phytoremediation (time-consuming) and soil washing using calcium chloride (generating Cd-contaminated wastewater requiring further treatment), face technical challenges, there is room for nanotechnology to offer a rapid and low-cost restoration technique. Here, we propose novel magnet-assisted (ex situ) soil washing using nanoscale zerovalent iron (NZVI) to remove Cd from paddy soil. Conceptually, Cd-contaminated paddy soil is mixed with water and NZVI to create a soil slurry. The NZVI promotes a reduction condition, which accelerates the Cd desorption from the paddy soil to the aqueous phase in the soil slurry. Subsequently, desorbed Cd in water is resorbed onto the NZVI surface, which is retrieved from the soil slurry through magnetic separation, leaving behind treated paddy soil and treated washing water. In our laboratory feasibility study with actual Cd-contaminated paddy soil (191.51±5.54mgkg−1), we found that, although magnet-assisted soil washing using NZVI cannot remove all the Cd from the soil to meet the EU and Thai soil standards (78% removal of total Cd), it effectively removes mobile Cd (exchangeable and carbonate fractions) from the soil (93%), which potentially results in a 97% reduction of cadmium in rice, which is safe for human consumption. The proposed technique has no unacceptable effects on the decline of macro- and micro-nutrients or the germination of rice seed.

Identification of QTLs and Validation of qCd-2 Associated with Grain Cadmium Concentrations in Rice

Cadmium (Cd) is one of heavy metals harmful to human health. As rice is the main staple food in Asia and Cd is easily contaminated in rice, the molecular regulation of Cd accumulation should be explored. In this study, a recombinant inbred population derived from Xiang 743/Katy was grown in Cd-polluted fields and used to map the quantitative trait loci (QTLs) for Cd accumulation in rice grains. We identified seven QTLs distributed on chromosomes 2, 3, 6, 7, 8 and 10. These QTLs displayed phenotypic variances of 58.50% and 40.59% in 2014 and 2015, respectively. Two QTLs, qCd-2 and qCd-7, were identified in both the two years. qCd-2 was detected on the interval of RM250–RM207 on chromosome 2, with an LOD of 2.51 and a phenotypic contribution of 13.75% in 2014, and an LOD of 3.35 and a phenotypic contribution of 14.16% in 2015. qCd-7 co-localized with the cloned qCdT7 on chromosome 7 and may represent the correct candidate. The other five QTLs were detected only in one year. To further confirm the effects of qCd-2, a residual heterozygous line designated as RHL945, with a heterozygous interval of RM263–RM207 on chromosome 2, was selected from the recombinant inbred population and used to develop an F2 population consisting of 155 individual plants. By incorporating further simple sequence repeat markers into the segmental linkage map of the target region, qCd-2 was delimited in the interval of RM5404–RM3774, with an LOD value of 4.38 and a phenotypic contribution of 15.52%. These results reflected the genetic regulation of grain Cd in rice and paved the way for the future cloning of qCd-2.

Determination of Cadmium Concentration in Milled and Brown Rice Grains Using Graphite Furnace Atomic Absorption Spectrometry.

Heavy metal pollution is a growing public health concern since it poses a food risk to public health via metal transfer. Cadmium is of particular concern because it is a potential carcinogen if exceed tolerable limits in the grain. Hence, it is important to monitor the cadmium content of rice before it reaches the market to ensure public healthy safety, especially in areas known to have high cadmium levels in soil. In this chapter, the method used to determine the concentration of cadmium in milled and brown rice grain samples is described. This method involves sample digestion with concentrated nitric acid and hydrogen peroxide and analysis of cadmium by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS). Because cadmium concentrations are low in rice grains, quantification of cadmium content requires the use of a more sensitive instrument, such as GF-AAS.

Identification of weak peaks in X-ray fluorescence spectrum analysis based on the hybrid algorithm combining genetic and Levenberg Marquardt algorithm

Accurate measurement of cadmium content in rice is of utmost importance to determine if the inspected rice product is safe to people. X-ray fluorescence analysis is frequently used for multi-element analysis because it has characteristics of fast, accurate and nondestructive. However, due to the low content of cadmium in rice, its corresponding characteristics energy peak is relatively weak and is sensitive to the background information in the X-ray energy spectrum. Thus, it is very tough to obtain the accurate values of cadmium content by utilizing traditional X-ray fluorescence analysis. In this paper, the identification of weak peaks of cadmium is much improved by proposing a hybrid algorithm combining genetic algorithm (GA) and Levenberg-Marquardt algorithm (LM). The hybrid algorithm not only takes full advantages of GA and LM respectively but also inhibits their unwanted properties: poor local search ability of GA and locally convergent of LM. The proposed hybrid algorithm is employed to identify weak peaks in X-ray spectra of six contaminated rice samples with different contents of cadmium. Two comparative experiments are conducted to compare the performance between GA, LM and the proposed hybrid algorithm. One of the comparative experiments has the relative error varying with the number of calculations, which aims to verify the accuracy and stability. The results show that the hybrid algorithm is a better option in terms of accuracy and stability. Another comparative experiment of which the average relative error varies with the number of iterations is conducted to verify the computing efficiency. The experiments show that the hybrid algorithm exhibits a faster convergence rate. Two numerical experiments demonstrate that the proposed algorithm can well resolve the identification issue of the cadmium in the X-ray spectra and significantly improve the content measurement accuracy of cadmium in the quality evaluation experiment of rice products.

Sprinkler irrigation is effective in reducing cadmium concentration in rice (Oryza sativa L.) grain: A new twist on an old tale?

Literature reports that the adoption of intermittent irrigation techniques instead of continuous flooding irrigation (CF) dramatically increases cadmium content in rice grain. Since rice is the principal human intake source of cadmium, we have felt appropriate to verify the general veracity of this statement. Hence, results relative to the cultivation, in the same experimental site for two consecutive years, of 26 rice genotypes using three different irrigation techniques – namely, CF, sprinkler (SP) and saturation (SA) are reported in this work. As compared to CF, using SP reduced the average concentration of cadmium in rice by between 13% and 28%, whereas irrigating by SA caused an extraordinary increase of cadmium between 760% and 1000%. Indeed, the analysis of data from our experiment and from the literature revealed that the high amounts of cadmium often observed in rice kernels can mostly be explained by the use of SA-like irrigation methods. In light of the evident sensitivity of the bioaccumulation process of cadmium in rice to the adopted irrigation methods, we carefully describe all procedures employed for our study. Finally, a tentative explanation for the opposite effects of SP and SA irrigation methods on the bioaccumulation of cadmium in rice is proposed.