Abstract
AbstractThe aim of this study was to determine the effects of biochar addition on agrochemical leaching in tropical soils of Belize. Biochars were produced from mixed softwood, rice husk and miscanthus straw, each pyrolysed at 700°C. Loam, sandy silt loam and clay loam tropical soils were amended with 0, 1, 2.5 and 5% (w/w) biochar to determine atrazine, diuron, enrofloxacine, oxytetracycline and tetracycline absorption in batch studies following OECD 106 guidelines. FOCUS groundwater modelling was performed with the results of the batch‐sorption study and alterations to the soil profiles to explore the effect of biochar amendment on the leaching of atrazine in a risk assessment context. Results showed that agrochemical sorption was higher in biochar‐amended soils than soils without biochar amendment. Soil organic matter content and biochar amendment contributed to the agrochemical sorption increase in soils. The FOCUS modelling showed a significant reduction in predicted environmental concentration in groundwater (PECgw) of atrazine when biochar was applied as a soil amendment. However, a trade‐off was identified between the sorptive capacity of the biochar and the changes in hydrology in the soil as a result of the biochar incorporation. The amendment of Belizean tropical soils with rice husk biochar was shown to be an effective method to reduce the leaching of the selected agrochemicals, although widespread implementation should be conducted carefully, taking account of the potential trade‐offs with biochar use identified in our modelling.Highlights Biochar‐amended soil is a feasible method to increase sorption and reduce agrochemical leaching to groundwater. Environmental fate modelling demonstrated that 1% and 2.5% biochar amendment could reduce atrazine leaching in soil. Modelling identified a biochar performance trade‐off: altered soil hydrology could lead to greater leaching. Biochar implementation must account for trade‐offs identified to ensure the mitigation works in each circumstance.
Highlights
Agricultural production in Belize, as in many other developing tropical countries, continues to advance with the assistance of agrochemicals
There is in effect, a trade-off between sorping more agrochemical to reduce leaching and not compromising soil integrity, leading to increased leaching. This trade-off makes it difficult to generalize the benefit of biochar in mitigating agrochemical leaching in all cases and, as such, we identify that biochar amendment appears a potentially effective tool to mitigate leaching, whilst cautioning against a generalization that all biochar will act to mitigate the risk from leaching in all cases
This study determined the effects of rice husk, miscanthus and softwood biochar types upon absorption of atrazine, diuron, enrofloxacine, oxytetracycline and tetracycline
Summary
Agricultural production in Belize, as in many other developing tropical countries, continues to advance with the assistance of agrochemicals. There is evidence that in some circumstances biochar has the potential to increase sorption of agrichemicals and reduce leaching to groundwater Taking this hypothesis further, modelling has been suggested as a suitable approach to identify the full implications of biochar for agrochemical sorption in the soil (Queyrel, Habets, Blanchoud, Ripoche, & Launay, 2016) in a “realworld” scenario. The aim of this study was to determine the effects of biochar addition to agrochemical leaching in various tropical soils from Belize, by (a) performing batchsorption studies with different biochars to explore their performance in sorption of different chemicals present in a mixture and (b) exploring the real-world implications of pesticide sorption with regards to risk assessments and the potential of biochar to mitigate leaching risk associated with some widely used, yet contentious, pesticides
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