关键词: 硅氧烷, 农用助剂, 叶面肥添加剂, 环境安全风险

Abstract:

Organosiloxane-based adjuvant (or organosilicon adjuvant), one of the silicone-fluide products, is polysiloxane, predominantly composed of covalently bonded silicon and oxygen atoms. Organosiloxane-based adjuvants are widely used as additives for daily chemicals and textile products, but also as agrochemical adjuvants in agriculture due to their super spreading and penetrating abilities. At present, China’s production and sales of silicone products have reached above 2 million tons, accounting for more than 50% of the world’s total amount. China has become the world’s largest producer, consumer and net exporter of raw materials of silicone, and the production capacity of polysiloxane has reached more than 60% of the world’s total. As organosiloxane residues detected in environment (especially in water, sludge/soil and other environmental samples, aquatic food chain, as well as human tissues), their impacts on agricultural ecological environment are increasingly exposed due to the widely application of organosiloxane-based adjuvants, while the environmental risks from silicone-based agrochemical adjuvants, including ecotoxicity and environmental safety risks, have also attracted great concern. In recent years, volatile cyclomethylcyclosiloxanes (such as D4 (octamethylcyclotetrasiloxane), D5 (decamethylcyclopentasiloxane) and D6 (dodecylcyclohexasiloxane)) have been recognized as emerging organic pollutants, or listed as priority controlled chemicals by EU and other countries, because of their environmental persistence, bioaccumulation and potential toxicity. Based on the relevant scientific research literatures published since 1991 on the environmental residues of organosiloxane-based adjuvants and the ecological environmental safety risks in the use of organosiloxane-based adjuvant (including organosiloxane-based agrochemical adjuvants), this paper reviewed and analyzed the environmental residues of organosiloxane-based adjuvants, and their impacts directly or indirectly on agricultural ecological environmental safety. This review mainly focused on the following two aspects: (1) the organosiloxane residues in environment and their impacts on the agricultural ecological environment safety, including organosiloxane residues and fates in the process of wastewater treatment, aquatic food chain pollution risks from organosiloxane residues in water, soil ecological pollution risks from organosiloxane residues in sludge, and human health risks from organosiloxane residues in food; (2) the current situation and environmental safety risks for the use of organosiloxane-based agrochemical adjuvants, including organosiloxane residues and ecotoxicity risks from siloxane-based agrochemical adjuvants, and the management for the use of organosiloxane-based agrochemical adjuvants. This paper also discussed the management status and problems associated with siloxane-based products. For organosiloxane as agrochemical adjuvants, organosiloxane-based adjuvants were largely assumed to be “biologically inert”, and usually no risk assessment (such as ecotoxicity test and environmental monitoring) was required. Also, the adjuvant inert ingredients were generally protected as “trade-secrets” or confidential business information, and the inert ingredients were rarely identified on product labels. At present, there are no regulatory requirements for the use of organosilicone-based adjuvants in fertilizer products as agrochemical adjuvants (such as foliar fertilizer additives) in China, posing potential environmental safety risks. This paper discussed that over-addition with organosiloxane-based agrochemical adjuvants might increase their residues in soil-crop-water systems, and their ecotoxicity risks, as well as potential threats to food safety and human health. It is suggested that relevant management and research units need to pay more attention to environmental monitoring for organosiloxane residues and fates in the application process of organosiloxane-based adjuvants, and especially strengthen the research on the impacts of organosiloxane residues from organosiloxane-based agrochemical adjuvants on water, soil, animal and plant growth, as well as human health.

Key words: organosiloxanes (silicones), agrochemical adjuvants, foliar fertilizer additives, environmental safety risks