Cadmium In Rice Research Articles

Modeling the spatial relationship between rice cadmium and soil properties at a regional scale considering confounding effects and spatial heterogeneity

Most previous studies have indicated inconsistent relationships between rice cadmium (Cd) and the soil properties of paddy fields at a regional scale under the adverse effects of confounding factors and spatial heterogeneity. In order to reduce these effects, this study integrates Geodetector, a stepwise regression model, and a hierarchical Bayesian method (collectively called GDSH). The GDSH framework is validated in a large typical rice production area in southeastern China. According to the results, significant stratified heterogeneity of the bioaccumulation factor is observed among different subregions and pH strata (q = 0.23, p < 0.01). Additionally, the soil-rice relationships and dominant factors vary by the subregions, and the available soil Cd and pH are found to be the dominant factors in 64% and 50% of subregions, respectively. In the entire region, when the pH < 6, the dominant factors are organic matter and available Cd, and when pH ≥ 6 they are organic matter, pH, and available Cd. Furthermore, these factors presented different sensitivity to the spatial heterogeneity. The results indicate that, at the subregional level, the GDSH framework can reduce the confounding effects and accurately identify the dominant factors of rice Cd. At the regional level, this model can evaluate the sensitivity of the dominant factors to spatial heterogeneity in a large area. This study provides a new scheme for the complete utilization of regional field survey data, which is conducive to formulating precise pollution control strategies.

Evaluation of manganese application after soil stabilization to effectively reduce cadmium in rice

In order to produce safe rice from cadmium (Cd) contaminated soils, a special pot experiment in the field was proposed to facilitate the study of multiple remediation measures. In the field experiments, four treatments were selected for the first half of the year: rice without soil treatment (R); rice with zeolite stabilization (RZ); oilseed rape phytoremediation (OR); and inter-cropping Sedum alfredii and maize phytoremediation (IC). As the early rice with zeolite stabilization still contained elevated Cd, manganese (Mn) fertilizer was added in the late rice with a special pot experiment in the field. Results showed that, in the first crops, the grains of maize and oilseed rape contained Cd below the food standard limit, while Cd in rice grain exceeded the limit of 0.2 mg/kg. The RZ treatment did not reduce Cd in rice but decreased significantly Mn in rice straw. In the late rice, Mn fertilizer additionally reduced Cd in rice grain to 0.12 mg/kg in combination with the RZ treatment. Mn accumulation in rice straw was enhanced by Mn fertilizer. These results indicate that the pot experiment in the field provides a useful tool to further evaluate effective treatment combinations to reduce Cd in rice.

Do brassinosteroids and iron plaque affect the accumulation of As and Cd in rice (Oryza sativa L.)?

Brassinosteroids (Brs) are a class of plant polyhydroxysteroids and play pivotal roles in plant growth and development. Furthermore, Brs are involved in the responses of plants to various heavy metal stresses. However, the role of Brs in the translocation and uptake of arsenic (As) and cadmium (Cd) in rice ( Oryza sativa L.) remains largely unknown. The present study was performed to examine the impacts of 24-epibrassinolide (Br24: 10 −10 and 10 −8 M), 28-homobrassinolide (Br28: 10 −10 and 10 −8 M), FeSO 4 addition (1 g kg −1 Fe) and their interactions on the accumulation of As and Cd by rice in pot trials. The results showed that the Fe content in iron plaque was increased by Fe addition but not by Br24/Br28. The interactions of Br24/Br28 and Fe enhanced the Fe contents in roots and stems. Br24/Br28 or Fe addition decreased the translocation and accumulation of As and Cd in rice grains. The interactions of Br24/Br28 or Fe further reduced the contents of As and Cd in rice grains. The As contents in grain were reduced by 60% under Fe addition, 18%–63% under Br24, 56%–73% under Fe+Br24, and 66%–72% under Fe+Br28. The grain Cd contents were reduced by 65% under Fe addition, 33%–61% under Br24, 56%–67% under Fe+Br24, and 43%–66% under Fe+Br28. These results suggest that the application of Fe, Br24/Br28 or their combination is effective in reducing the contents of As and Cd in rice grains, which has strong implications for agricultural production and food security. • Br24/Br28 + Fe enhanced the Fe contents in rice stems, roots and pore water. • Exogenous Fe addition decreased As and Cd in rice grains and pore water. • Br24/Br28 + Fe reduced grain As by 56%–73% and grain Cd 43%–67%.

Study on the bioaccessibility and bioavailability of Cd in contaminated rice in vitro and in vivo.

Cadmium (Cd) is a widespread heavy metal pollutant in the environment that damages human health. In this study, the bioaccessibility and bioavailability of Cd in different Cd-contaminated rice (low pollution level cadmium rice (Rice-L, 0.111mg/kg),mediumpollutionlevelcadmiumrice(Rice-M, 0.400mg/kg), and high pollution level cadmium rice (Rice-H, 0.655mg/kg)) were estimated and determined by an in vitro digestion model Rijksinstituut voor volksgezondheiden milieu (RIVM), Caco-2 cell model, and mouse model. The results indicated that Cd in the oral cavity (15.65-28.28%) displayed the lowest bioaccessibility comparing with small intestine (90.04-94.73%) and the stomach (99.30-100.70%) in vitro after cooking. In addition, the results showed that the bioaccessibility of Cd in CdCl2 , CdCl2 +normal rice (Rice-N), Rice-H, Rice-M, Rice-L group were 99.29%, 92.57%, 90.04%, 94.73%, and 91.11%, respectively; the in vitro bioavailability of Cd in CdCl2 , CdCl2 +Rice-N, Rice-H, Rice-M, and Rice-L group were 27.50%, 20.78%, 21.90%, 26.90%, 36.46%, respectively, we found that the group of CdCl2 is significantly higher than CdCl2 +Rice-N and Rice-H (p<0.05), while the targets hazard quotient (THQ) value of rice ingested without considering the in vitro bioavailability is 2.7-4.6 times than the THQ value with considered and the relative bioavailability (RBA) of Cd in Rice-L, Rice-M, Rice-H are 80.25%, 64.32%, and 60.91%, respectively. These results indicate that the rice substrate has impact on the bioaccessibility and bioavailability of Cd, and might overestimate the health risks of Cd if bioavailability was not considered. PRACTICAL APPLICATION: Studying the bioaccessibility and bioavailability of cadmium in rice is a promising strategy to obtain a more accurate human health risk assessment of cadmium exposure in rice, as well as provide a theoretical basis for the formulation of cadmium limit standard in grain, which was also conducive to the rational and full utilization of rice resources in China.

Lateral roots but not root hairs contribute to high uptake of manganese and cadmium in rice.

Rice (Oryza sativa L.) can accumulate high manganese (Mn) in the shoots through uptake by the roots, which consist of crown roots, lateral roots and root hairs. We investigated the role of lateral roots and root hairs in Mn and cadmium (Cd) uptake by using two indica rice mutants defective in formation of lateral roots (osiaa11) and root hairs (osrhl1). The uptake of Mn and Cd in osiaa11 was significantly lower than that in wild type 'Kasalath', but there was no difference between wild type and osrhl1. Furthermore, a kinetic study showed that Mn uptake in osiaa11 was much lower than that in wild type and osrhl1 across a wide range of Mn concentrations. The role of lateral roots in Mn and Cd uptake was further confirmed in a japonica rice mutant defective in lateral root formation. We found that expression of Mn transporter gene Natural Resistance-Associated Macrophage Protein 5 (OsNRAMP5), but not of Metal Tolerance Protein 9 (OsMTP9), was lower in osiaa11 than in wild type; however, there were no differences between osrhl1 and the wild type. Immunostaining showed that OsNRAMP5 and OsMTP9 were localized in the exodermis and endodermis of crown roots and lateral roots, but not in the root hairs. Taken together, our results indicate that lateral roots, but not root hairs, play an important role in high Mn and Cd uptake in rice.

Determination of inorganic arsenic, heavy metals, pesticides and mycotoxins in Indian rice (Oryza sativa) and a probabilistic dietary risk assessment for the population of Saudi Arabia

In this study, total arsenic (As), inorganic arsenic (iAs), cadmium (Cd), lead (Pb), mercury (Hg), pesticides, and aflatoxins (B1, B2, G1, G2) in Indian rice (Oryza sativa) and their dietary exposure risks for the general Saudi population were evaluated. A total of 483 samples were acquired from various ports and supermarkets throughout the country. Average elemental concentrations were found to be in the following order: As (0.1 ± 0.024)>iAs (0.038 ± 0.015)>Pb (0.023 ± 0.008)>Cd (0.019 ± 0.005)>Hg (0.002 ± 0.0004), and results did not exceed maximum residue limits (MRLs). Out of the 294 analyzed pesticides, 15 were detected in rice, of which six were fungicides, and nine were insecticides with a detection frequency of 22% and 26%, respectively. Eight of the detected pesticides were non-approved by the European Union (EU) commission, but their detection frequencies were low. Surprisingly, rice samples analyzed for aflatoxins were below the limit of quantification (LOQ). Risk assessment coupled with Monte Carlo simulation based on the hazard quotient (HQ) and incremental lifetime cancer risk (ILCR) approaches revealed that exposure to metal(loid)s and pesticides in rice were below levels that might pose a health risk.

Rhizosphere bacterial community composition affects cadmium and arsenic accumulation in rice (Oryza sativa L.)

Cadmium (Cd) and arsenic (As) contamination in paddy soils poses serious health risks to humans. The accumulation of Cd and As in rice (Oryza sativa L.) depends on their bioavailability, which is affected by soil physicochemical properties and soil microbial activities. However, little is known about the intricate interplay between rice plants and their rhizosphere microbes during the uptake of Cd and As. In this study, different bacterial communities were established by sterilizing paddy soils with γ-radiation. A pot experiment using two paddy soils with different levels of contamination was conducted to explore how the bacterial community composition affects Cd and As accumulation in rice plants. The results showed that the sterilization treatment substantially changed the bacterial composition in the rhizosphere, and significantly increased the grain yield (by 33.5–38.3%). The sterilization treatment resulted in significantly decreased concentrations of Cd (by 18.2–38.7%) and As (by 20.3–36.7%) in the grain, straw, and root of rice plants. The accumulation of Cd and As in rice plants was negatively correlated with the relative abundance of sulfate-reducing bacteria and iron-oxidizing bacteria in the rhizosphere. Other specific taxa associated with the accumulation of Cd and As in rice plants were also identified. Our results suggest that regulating the composition of the rhizosphere bacterial community could simultaneously reduce Cd and As accumulation in rice grain and increase the grain yield. These results would be useful for developing strategies to cultivate safe rice crops in areas contaminated with Cd and As.

Effects of sulfur application on cadmium accumulation in brown rice under wheat-rice rotation

We investigated how sulfur (S) application prior to wheat cultivation under wheat-rice rotation influences the uptake of cadmium (Cd) in rice grown in low- and high-Cd soils. A pot experiment was conducted with four S levels (0, 30, 60, 120 mg S kg−1) and two Cd rates (low and high, 0.35 and 10.35 mg Cd kg−1) supplied to wheat. Part of the wheat straw was returned to the soil before planting rice, which was cultivated for 132 days. To explore the key mechanisms by which S application controlled Cd accumulation in brown rice, (1) soil pore water at the key growth stages was sampled, and dissolved Cd and S species concentrations were determined; (2) rice plant tissues (including iron plaque on the root surface) were sampled at maturity for Cd and S analysis. With increasing S level, Cd accumulation in brown rice peaked at 60 mg S kg−1, irrespective of soil Cd levels. For high-Cd soils, concentrations of Cd in brown rice increased by 57%, 228%, and 100% at 30, 60, and 120 mg S kg−1, respectively, compared with no S treatment. The increase in brown rice Cd by low S levels (0–60 mg kg−1) could be attributed to (1) the S-induced increase in soil pore water sulfate increasing the Cd influx into rice roots and (2) the S-induced increase in leaf S promoting Cd translocation into brown rice. However, brown rice Cd decreased at 120 mg S kg−1 due to (1) low Cd solubility at 120 mg S kg−1 and (2) root and leaf S uptake, which inhibited Cd uptake. Sulfur application to wheat crop increased the risk of Cd accumulation in brown rice. Thus, applying S-containing fertilizers to Cd-contaminated paddy soils is not recommended.

Study on toxicological effect and the mechanism of cadmium in rice and inorganic cadmium on ICR mice.

Cadmium (Cd) exposure may induce chronic intoxication, but the harm of cadmium in rice to human at chronic low-level Cd exposure remains unclear. This study employed a mouse model to investigate the toxicity and mechanism of cadmium in rice and CdCl2. After 8-week exposure to Cd (CdCl2 and Cd-contaminated rice), the biochemical indicators and oxidation indicators in the serum and liver of mice were determined, and used mRNA sequencing to investigate the mechanism of different forms of Cd. Results showed that the cadmium concentration of the liver in the CdCl2+Rice-N group (CdCl2 mixed with feed and normal rice, 0.4mg/kg.bw) was higher than that in the Rice-H group (0.4mg/kg.bw). However, the cadmium concentration of the kidneys in the Rice-H group was higher than that in the CdCl2+Rice-N group. Our study demonstrated that Cd-treated (Cd in rice and CdCl2) ICR mice generated obviously tissues injury, such as the increased biochemical studies, the activity of antioxidant enzymes debasement. Simultaneously, our data also indicated that there existed difference of the hepatic toxicity between Cd in rice and CdCl2. By means of transcriptomics, we discovered that CdCl2 and Cd in rice may affect different gene expression at the molecular level. We hope to provide some theoretical basis for the revision of food security standards.

Effects of Pseudomonas TCd-1 on rice (Oryza sativa) cadmium uptake, rhizosphere soils enzyme activities and cadmium bioavailability under cadmium contamination

Microbial remediation is a promising technique to reduce Cd accumulation in rice (Oryza sativa). In present study, a set of pot experiments were conducted to evaluate the effects of Cd-tolerate Pseudomonas TCd-1 inoculation on rice Cd uptake, soil enzyme activities and Cd bioavailability in the rhizosphere soils under Cd contaminated conditions. The results showed that at the ripening stage, with the inoculation of TCd-1, Cd contents in root, culm, leaf, hull and brown rice significantly reduced by 60.7%, 47.7%, 50.6%, 58.1% and 47.9%, respectively, and the cadmium bioconcentration factor (BCF) of rice lowered by 66.2% under 5 mg kg−1 Cd treatment. At the meantime, in the rhizosphere soils, pH increased by 0.05, the contents of exchangeable Cd (EX-Cd) and Fe-Mn oxides (OX-Cd) increased by 107.8% and 33.5%, whereas organic matter (OM-Cd) and residual (Res-Cd) decreased by 31.9% and 60.0%, respectively. The activity of acid phosphatase (ACP) increased by 28.3%, catalase (CAT), saccharase (SUC) activity decreased by 28.5% and 26.0%. Similarly, the Cd contents in root, culm, leaf, hull and brown rice reduced by 42.1%, 42.5%, 58.0%, 50.3%, and 68.8%, respectively, and the BCF lowered by 57.1%, under 10 mg kg−1 Cd treatment. Simultaneously, the soil pH increased by 0.06, the activities of CAT, SUC, urease (URE), ACP decreased by 26.4%, 34.6%, 63.8% and 15.3%, respectively. Furthermore, the correlation analysis showed that the inoculation of TCd-1 changed the correlation between rice Cd content and the biomass of roots, leaves, soil pH, CAT, PPO, URE activities, OM-Cd in rhizosphere soils. It suggested that Pseudomonas TCd-1 effectively reduced Cd uptake and Cd accumulation in rice was closely linked to the changes of soil pH, enzyme activities and Cd availability.

Photosynthetic Parameters and Growth of Rice, Lettuce, Sunflower and Tomato in an Entisol as Affected by Soil Acidity and Bioaccumulation of Ba, Cd, Cu, Ni, and Zn.

The bioaccumulation of trace elements (TEs) in crops consumed by humans can reduce food production as a consequence of photosynthetic damage in plants and cause several diseases in humans. Liming is a soil management strategy designed to alleviate soil acidity and mitigating these problems by reducing the TE bioavailability. In this study, we evaluated the effect of liming on photosynthesis, growth, and bioaccumulation of barium (Ba), cadmium (Cd), copper (Cu), nickel (Ni), or zinc (Zn) in lettuce (Lactuca sativa L.), rice (Oryza sativa L.), sunflower (Helianthus annuus L.), and tomato (Solanum lycopersicum L.) grown in a sandy Entisol. The crops were grown in either uncontaminated or contaminated Entisol, at two base saturation (BS%) ratios: 30% for all crops or 50% for rice and 70% for lettuce, sunflower, and tomato. The photosynthesis-related parameters varied depending on the metal and the crop, but in general, increasing BS% did not attenuate photosynthetic damage induced by Ba, Cd, Cu, Ni, and Zn in the crops. There was no strong correlation between the photosynthetic parameters and biomass production, which indicates that the suppression of biomass induced by Ba, Cd, Cu, Ni, or Zn is related to other metabolic disorders in addition to the impairment of CO2 assimilation or chlorophyll synthesis in the crops assayed, with the exception of Ni and Zn in lettuce. In conclusion, increasing BS% was not consistent in reducing Ba, Cd, Cu, Ni, and Zn accumulation in the edible parts of lettuce, rice, sunflower, and tomato grown in the sandy soil, which is probably related to the low capacity of this soil to control TE bioavailability.

Effects of Different Organic Materials on Absorption and Translocation of Arsenic and Cadmium in Rice

A pot experiment was carried out to study the impacts of five organic materials (rape straw, broad bean stalk, peat, pig manure compost, and biochar) on the availability of arsenic (As) and cadmium (Cd) in soil, the amount of iron plaque on the root surface, as well as the uptake and translocation of As and Cd in rice grown in an As/Cd co-contaminated yellow paddy soil. The results indicated that the application of organic materials significantly increased the contents of the soil organic matter and the yield of rice. The application of broad bean stalk, peat, pig manure compost, and biochar remarkably increased the soil pH, while the application of rape straw exerted no significant influence. The addition of organic matter reduced the available Cd content by 34.77%-82.69%. However, the effects of organic materials on the availability of As varied with the organic materials. The soil-available As content was significantly increased by the application of pig manure compost and biochar, while it was significantly decreased by adding rape straw and peat. The application of organic materials increased As and Cd contents in the Fe plaques on rice root surface by 28.49%-94.86% and 17.73%-151.03%, respectively. It also reduced the As and Cd contents in brown rice by 27.04%-82.51% and 15.87%-79.45%, respectively. The largest decrease was observed in the biochar treatment. The application of organic materials also remarkably reduced the translocation efficiency of Cd from the root-stem-leaf-grain and that of As from the stem to grain. The correlation analysis revealed that the soil pH, available Cd, and Cd content in the Fe plaques are the major factors influencing the accumulation of Cd in the rice grain. Furthermore, the soil pH, soil organic matter, and As content in the Fe plaques are the major factors influencing the accumulation of As in the rice grain. Therefore, it has been concluded that organic materials could influence the uptake and translocation of As and Cd in rice through changing the soil pH, organic matter content, and As and Cd contents in the Fe plaques.

Quantitative analysis of cadmium in rice roots based on LIBS and chemometrics methods

BackgroundExcessive cadmium can damage cell structure, inhibit enzyme activity, and affect metabolic process, thus, leading to decline of rice yield and quality. Root is an important organ of crops, the detection of cadmium in root is essential for limitation of cadmium in rice grains.ResultsIn this study, laser-induced breakdown spectroscopy (LIBS) was applied for cadmium quantitative analysis. Pretreatment methods, including median absolute deviation, wavelet transform, area normalization, were used to improve spectral stability. Scanning electron microscope and energy-dispersive X-ray spectrometer (SEM/EDS) was first used to analyze ablation pit surface characteristics and the results showed significant positive correlation with spectral lines of Cd II 214.44, Cd II 226.50 and Cd I 228.80 nm. Univariable models of spectral lines showed that three Cd spectral lines have good prediction for cadmium. Fitting methods including linear, logarithmic, and polynomial were used to propose characteristic input variables, and univariable models based on variable of polynomial fitting of I214.44 nm have achieved the best effect (Rp = 0.9821 and RMSEP = 31.1 mg/kg). Besides, partial least squares regression (PLSR), least squares support vector machine (LS-SVM) and extreme learning machine (ELM) were used for multivariate analysis. Compared with univariate analysis, ELM model based on the full spectrum (Rp = 0.9896 and RMSEP = 26.0 mg/kg) had more advantages for cadmium detection.ConclusionCompared with traditional methods (150 min), the quantitative detection method based on LIBS technology (less than 5 min) greatly reduces the detection time of heavy metals. The results showed that LIBS has proved to be a reliable method for quantitative detection of cadmium in rice roots. The research can provide theoretical support for timely detection of heavy metals in crop and food production.

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.

Levels of heavy metal cadmium in rice (Oryza sativa L.) produced in Taiwan and probabilistic risk assessment for the Taiwanese population

Cadmium (Cd) is a toxic pollutant that is widely spread through industrial production and agricultural practices. Epidemiological data has revealed that lifetime exposure to environmentally relevant levels of Cd increases the risk of developing various organ diseases, including chronic kidney, heart, and lung diseases, as well as nervous tissue disorders. This study assessed Cd levels in rice to determine the health risks associated with rice consumption in various age-gender subgroups in Taiwan. The distribution of Cd concentration, the lifetime average daily dose (LADD), and the hazard index (HI) were estimated by Monte Carlo simulation. In the general population, the 50th percentile LADD of Cd for male rice consumers between the ages of 19–65 years was 0.06 μg/kg body weight per day, and the hazard index (HI) 50th, 90th, and 95th percentiles were 0.16, 0.69, and 1.54, respectively. According to the HI heat map for the exposure of the general population to Cd from rice in Taiwan, the highest exposure to Cd was noted in the Yilan area (HI 0.64). Therefore, rice production in the Yilan area should be further monitored to evaluate the levels of Cd contamination.

Retraction: Determination of cadmium in rice using nanoparticle-enhanced laser-induced breakdown spectroscopy combined with film preparation

Retraction of ‘Determination of cadmium in rice using nanoparticle-enhanced laser-induced breakdown spectroscopy combined with film preparation’ by Jinming Niu et al., J. Anal. At. Spectrom., 2020, 35, 2990–2996, DOI: 10.1039/D0JA00354A.

Integration of cobalt ion assisted Fenton digestion and photochemical vapor generation: a green method for rapid determination of trace cadmium in rice

Integrating Fenton-like digestion as well as metal ion assisted photochemical vapor generation for analysis of Cd in rice samples, coupled with inductively coupled plasma-mass spectrometry (ICP-MS) measurements.

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.

Effects of Fe and Mn cations on Cd uptake by rice plant in hydroponic culture experiment.

Iron (Fe) and manganese (Mn) are nutritional components of rice, plays an important role in its physiological processes and can minimize absorption of cadmium (Cd) in rice. Fe, Mn, and Cd transporters such as CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, OsHMA3, and OsNAAT1 regulate uptake of Cd in rice. However, the effect of exogenous application of Fe, and Mn on the accumulation of Cd and relative expression (RE) of these transporters in rice has not been investigated. Therefore, a hydroponic culture experiment was conducted to investigate the impact of Fe and Mn on Cd uptake and RE of these transporters in rice. The results showed that the Fe and Mn application significantly decreased Cd in the roots and shoots of rice. Whereas, Cd concentration in the rice significantly increased with increasing Cd concentration in the solution. The addition of manganese in the culture medium can reduce the cadmium content of rice roots by 11.9–82.3% and shoots by 11.6–85.0%, while the addition of iron in the culture medium can reduce the cadmium content of rice roots and shoots by 26–65% and 9–683% respectively. Meanwhile, application of sufficient doses of Fe and Cd in solution culture increased RE of CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, and OsNAAT1 in roots, whereas expression level of OsHMA3 was decreased. Similarly, expression level of CAL1, OsNRAMP5, and OsNRAMP1 significantly increased in roots in high Cd and Mn deficient treatments. This may be concluded that the Cd increases expression of CAL1, OsNRAMP5, OsNRAMP1, OsIRT1, and OsNAAT1 but decreases OsHMA3 expression in rice roots, which resulted in increased Cd uptake in hydroponically grown rice.