Presenter: Prof. Nan Sun, School of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin, Heilongjiang
Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-6. Aquatic biodiversity protection
Body
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in the environment, especially in the sediments of field throughout the world, and they are of great interest due to their toxic effects on the environment. Rice-crab culture combines crab production in paddy rice systems. It is also an ecological and green agricultural mode. Due to its significant economic benefits, the rice-crab culture has become one of the most important agricultural models in China. However, the bioturbation of crabs is likely to lead to the secondary release of PAHs from sediment to water in rice-crab culture system. This brings new potential risks. As traditional agricultural waste, the annual production of rice straw exceeding 200 million tons. Rice straw biochar (RSC) has been extensively studied in heavy metal and inorganic contaminated soils/sediments, while relatively little information is available for organic pollution such as PAHs, and the inhibitory effect of biochar on the release of PAHs from sediments is still unclear. Therefore, the main objective of this study was (i) to prepare the new rice straw biochar for characterization and adsorption mechanism analysis and (ii) taking Phenanthrene (PHE) as the representative PAHs pollutant, to investigate the inhibition property of PHE in sediment release to overlying water, transfer to sediment, and bioaccumulation by RSC in rice-crab culture field based on the micro-universe experiment. The results showed that the prepared RSC had a rich pore structure and a high specific surface area. The optimum addition amount was 0.5% of soil mass. The adsorption mechanism of RSC on PHE was dominated by chemisorption and more inclined to the monolayer adsorption on the surface of RSC. After the addition of RSC in sediment of rice-crab culture field during the 30d experimental period, the content of PHE in sediment was increased by 40.41%~119.62%, the dissolved and particulate PHE contents in the overlying water were reduced by 54.67%~81.03% and 5.08%~55.20%, respectively. Meanwhile, RSC decreased the concentration of PHE enriched in crab and rice, and the distribution of PHE in various organs of rice was also altered. These results confirmed the RSC can effectively inhibit the transport and release of PHE from sediments to the surrounding environment while reducing the bioavailability of PHE under the integrated farming system. This study will provide the most important theoretical guidance and technical support on the PAHs pollution prevention and controlling, risk reduction in rice-crab culture field.