C-cycling in grazed wetlands: effect of cattle and an antiparasitic drug in soil carbon stocks

OLVELLI, MELISA; GARCÍA-BOLOQUY, JONATHAN; PIERRO REBOIRAS, JUAN; MESA, LETICIA; FLORES, DANIEL; LORENTE, CAMILA; QUINTANA, RUBÉN

Belfast

Congreso; Annual Conference of The British Society of Soil Science and The Soil Science Society of Ireland.; 2023

The British Society of Soil Science and The Soil Science Society of Ireland

Over the last 150 years enormous amounts of carbon have been lost from soil due to land usechange. The carbon lost from soil has had a dramatic impact on the amount of carbon in theatmosphere and has escalated climate change. The World Health Organization (WHO, 2018)states antibiotic (AB) resistance as “one of the biggest threats to global health” (O’Neill, 2016Review on AMR). When livestock are treated, ABs and other veterinary drugs can enter soilsgenerating an enhancement of C cycling in soils, contributing to GHG emissions and climatechange. Issues of veterinary drugs use and land degradation conflate in Argentina, wherewetlands are being exploited to support livestock production. This has led to wetlanddegradation and the influx of antibiotics and antiparasitics into the wetlands (Peluso et al.,2023, Environ. Res., 226, 115692). While there are many reports on soils stress, leading to Closs caused by AB inputs, no information was found for the widely used antiparasitic,Ivermectin. On a previous study we also analysed the environmental presence of ivermectinin three different soils from farms located in Delta del Parana, Argentina. Results indicatedthat all soils had ivermectin and its mobility in the environment was related to water solubleorganic matter.The aim of this work was to study the effect of cattle and ivermectin concentrations on Ccycling in soils with different hydrological regimes. In field GHG emissions were measuredin two different locations to evaluate the effect of livestock in soil carbon. GHG emissionswere collected every 15 days, during 6 months, using a static chamber model and GC MSwas used for determination of CO2 and CH4. Mesocosms experiments were instated toinvestigate soil ivermectin interactions in redox changing conditions, including the fate andpotential bioavailability of the compound; and GHG emissions. Hydrological regime wassimulated maintaining soil water up to 60% or 100% of the soil water holding capacity(WHC). Ivermectin was added to the soil in an environmentally relevant concentration (500ppb) and systems were maintained for 3 months. GHG emissions were collected every 15days. Samples were taken each month: organic matter was fractionated in soluble, free labileand occluded labile (water and heavy liquid fractionation, respectively). For partitioning ofthe contaminant, ivermectin was determined (HPLC MS) in the soluble fraction (waterextraction) or in the total soil fraction (solvent extraction).Results indicated that the presence of ivermectin, enhanced the mineralization of organicmatter and ivermectin mobility. Over time, the water soluble fraction increased in all soilstreated with ivermectin indicating rapid degradation of organic matter. This led to anincrease of GHG emissions. Mesocosms results evidenced the influence of these type ofveterinary drugs in wetland soils and provide insight into the linkages between ivermectinbioavailability and the pressure antiparasitics exert on soil C s tocks. Field GHG emissionsindicated that livestock had a more negative effect on soil C when the soil was drier and in more degraded environments where biogeochemical cycles are diminished. Establishingthese linkages is novel and will support better livestock management.