Abstract
The aims of this experiment are to explore the accumulation of metal contamination of different varieties of rice planted in paddy fields and to provide a basis for the further research. The rice specimens were grown in and collected from a total area of 8.24 acres of rice planting fields where local farmers cultivated 50 different kinds of rice. The crops were grown using the methods of seedling, transplanting, fertilizing, and irrigation, under the guidance of professional and technical personnel. The 50 kinds of paddy rice contain 20 kinds of conventional rice, 15 kinds of two-line hybrid rice, 15 kinds of three-line hybrid rice, and the whole experiment lasted 100 days. To begin our analysis of the data, we first gathered 15 irrigation water samples respectively from the first day of the experiment. This was then followed by gathering water samples from the tillering stage, then the development stage, the solid phase, and finally, the last day of the experiment. On the first day and at the end of the experiment, we had respectively gathered 6 mud samples from the rice paddies, with a total 12 parts of it. In addition to this, by the end of the experiment, we had gathered 6 samples of rice spike from each type of the investigated rice, with a total 300 parts of it. These samples were then analyzed in the laboratory to detect the contents and amounts of lead, cadmium, chromium, arsenic, copper, calcium, fluoride, nitrogen, phosphorus, potassium in the samples, and the pH quality of the samples. The quality of irrigation water was evaluated according to irrigation water quality standards (GB 5084-2005); the rice paddy mud samples were detected and evaluated respectively according to farmland soil environment quality monitor technology standards (NY/T 395-2012) and the journal of environmental quality assessment standard of edible agricultural products (HJ 332-2006); the rice grains were detected and evaluated according to the limited food standards (GB 2762-2012); the bioaccumulation factors (BCFs) were adopted to evaluate the accumulation ability of metal contamination in rice. As a result, the test values of the irrigation water samples were within irrigation water quality standards. Only the content of cadmium was beyond the environmental quality assessment standard of edible agricultural products, by 0.07 mg/kg. The content of lead and cadmium in 50 different rice were 0.41 ± 0.01~0.49 ± 0.01 mg/kg and 0.22 ± 0.01~0.25 ± 0.01 mg/kg, respectively. The varietal differences were not statistically significant (P>0.05). Lead BCFs, cadmium BCFs, and chromium BCFs in 50 different kinds of rice had no statistical difference (P>0.05). For the content of lead, cadmium, chromium, inorganic arsenic and copper in the conventional rice samples, two-line hybrid rice samples, and three-line hybrid rice samples, there was no statistical difference (P>0.05). Lead BCFs, cadmium BCFs, chromium BCFs, arsenic BCFs, and copper BCFs also had no statistical difference (P>0.05). This means the content of cadmium and lead contaminant in the 50 kinds of rice exceeded food quality and limits. The content of cadmium of mud samples exceeded the assessment standard by 0.07 mg/kg, the content of cadmium, of the 50 kinds of rice, exceeded the limited food standard by 0.04 mg/kg. The content of lead in the paddy mud was within the limited value, but the content of lead exceeded the limited food standard by 0.24 mg/kg. For the lead BCFs, cadmium BCFs, and chromium BCFs of the 50 kinds of rice, there was no statistically significant difference. This was the same for lead BCFs, cadmium BCFs, chromium BCFs, arsenic BCFs, and copper BCFs during conventional rice, two-line hybrid rice, and three-line hybrid rice. For the above, the rice had a strong adsorption capacity of lead. The conclusions of this data lead us to not only implement measures of control but also to conduct research on the suitable levels of lead in edible agricultural products.
Highlights
Heavy metal pollution of crops has become a global issue
Through a farmland cultivation experiment in the same environment, we explored heavy metal enrichment situations in 50 different kinds of rice, providing a reference for further study about the safety of heavy metals detected in rice and providing additional data support for controlling said detected metals
The cadmium contents found in 50 different kinds of rice exceeds the contaminant limit standard 0.04 mg/kg
Summary
Heavy metal pollution of crops has become a global issue. The potential hazards and solutions are a widespread concern of scholars (Li et al 2004). Researches both domestically and abroad have been conducted on the heavy metal accumulator situation in different types of rice. Through a farmland cultivation experiment in the same environment, we explored heavy metal enrichment situations in 50 different kinds of rice, providing a reference for further study about the safety of heavy metals detected in rice and providing additional data support for controlling said detected metals.
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