Accumulation patterns and pedological significance of boron, molybdenum, and zinc in floodplain agroecosystems subject to sedimentation processes

Periodic sedimentation in floodplain agroecosystems creates unique conditions for the redistribution of trace elements between alluvial soils and incoming flood deposits. This study examined the transport dynamics and accumulation behavior of boron, molybdenum, and zinc delivered via flood sediments to reclaimed arable lands in the Oka River floodplain of the Ryazan region over a four year period from 2022 to 2025. Field monitoring employed sediment traps installed across a 20 hectare experimental site. Mobile fractions of the three microelements in both sediment deposits and underlying alluvial soil were analyzed using photometric methods for boron and molybdenum and atomic absorption spectrometry for zinc. Results revealed that average annual sediment load during flood years reached 10.8 tonnes per hectare with substantial interannual variability driven by flood intensity. Zinc concentrations in flood sediments exceeded those in the underlying alluvial soil by a factor of 2.5, indicating pronounced enrichment. In contrast, boron and molybdenum concentrations in sediments were reduced by 16 percent and 50 percent respectively relative to soil background levels. Regression models with coefficients of determination ranging from 0.999 to 1.0 were developed to describe the nonlinear relationships between sediment load and microelement concentrations in deposited material. The observed accumulation sequence of zinc exceeding boron exceeding molybdenum reflects differential geochemical mobility and sorption affinities during sediment transport. These findings advance understanding of biogeochemical cycling for key micronutrients in floodplain agroecosystems and provide a scientific framework for incorporating natural sediment inputs into adaptive soil fertility management strategies.