The key growth period of cadmium and arsenic accumulation in rice grains revealed

The key growth period of cadmium and arsenic accumulation in rice grains revealed

The key growth period of cadmium and arsenic accumulation in rice grains revealed

Recently, the research group of Professor Wang Peng from the School of Resources and Environmental Sciences of Nanjing Agricultural University revealed the key growth period for the accumulation of cadmium and arsenic in rice grains
.

Related research results were published in "Environmental Pollution"

Heavy metal pollution of agricultural products threatens people's health, and rice is the main source of cadmium and inorganic arsenic intake
.

Cadmium and arsenic in farmland soil can enter rice grains through two ways: root absorption, redistribution and transportation

In response to this problem, Wang Peng’s research team used pot experiments to set various water treatments at different growth stages of rice to adjust the soil redox status and the content of cadmium and arsenic in the pore water.
The relative contribution rate to the accumulation of cadmium and arsenic in rice during the growth period
.

Studies have shown that under conventional rice field water management conditions (from flooding in the vegetative growth stage of rice to drainage in the middle and late stages of grain filling, and short-term drainage in the late tillering stage), the key period for cadmium accumulation in rice is the grain filling stage
.

During this period, the cadmium absorbed by the rice roots from the soil contributed 98% of the cadmium in the grains, while the cadmium accumulated in the stems and leaves during the vegetative growth stage of rice contributed little to the redistribution and transport to the grains

An important reason for this result is that due to the changes in soil cadmium and arsenic availability at different growth periods, paddy field drainage in the middle and late stages of rice filling will greatly increase the availability of soil cadmium and reduce the availability of soil arsenic
.

Earlier studies also found that the activation rate of cadmium on different soils varies greatly during the oxidation stage of paddy field drainage, which is mainly controlled by the galvanic effect between metal sulfides and the oxidation effect of ferrous free radicals mediated by hydroxyl radicals

The difference in the contribution of different growth stages of rice to the accumulation of cadmium and arsenic in grains provides a water management strategy that can simultaneously control the accumulation of cadmium and arsenic in the contaminated paddy field, that is, segmented water management
.

By flooding or delaying drainage as much as possible in the middle and late stages of rice filling, the accumulation of cadmium in the grains can be effectively reduced, and the accumulation of arsenic in the grains can be effectively reduced by multiple drainage or intermittent irrigation and drainage during the rice tillering to heading stage

The difference in the contribution of different growth stages of rice to the accumulation of cadmium and arsenic in the grain explains many field phenomena
.

For example, why the water treatment in the rice filling stage has a greater impact on the cadmium content of grains than on the arsenic in the grains, while the water management before the filling stage has a greater impact on the arsenic in the grains

The above research results have deepened the understanding of the biogeochemical processes of cadmium and arsenic in paddy soils, and have important guiding significance for controlling soil cadmium activation after paddy field drainage
.

(Source: Wang Fang, China Science News)

Related paper information: https://doi.

https://doi.
org/10.
1016/j.
envpol.
2021.
118497