Rates of biogeochemical phosphorus and copper redistribution in young floodplain soils

Abstract

Abstract. Nutrients and trace metals in river-floodplain systems may originate from anthropogenic activities and/or geogenic sources. Here, we analyze a soil chronosequence on a floodplain at the Danube River (Austria) to quantify the rates of P and Cu redistribution among biogeochemical pools during 600 years of soil formation under temperate continental climate. While bulk and clay mineralogy remained unchanged over the studied age gradient, we found considerable (mostly non-linear) redistribution of P and Cu among biogeochemical pools. The calcium-associated P and Cu pools decreased rapidly during the initial decades of soil formation. The dissolution of the calcium-associated pools was mirrored by marked accumulation of organic P, but was not accompanied by changes in organic matter-associated Cu. The dissolution rates of calcium-associated (primary mineral) P showed an exponential decrease with increasing soil age, and were almost an order of magnitude higher than rates reported for tropical environments. Our study demonstrates that on riverine floodplains, substantial biogeochemical redistribution can occur within the first centuries of soil formation, and that, even under temperate climatic conditions, biogeochemical transformation rates can be exceedingly high in these ecosystems.