Relative importance of organic- and iron-based colloids in six Nova Scotian lakes

Abstract Dissolved organic matter (DOM) concentrations have been increasing in parts of the northern hemisphere for several decades. This process—brownification—often accompanies iron and aluminum, but metal–DOM interactions these concurrent trends imply are poorly described. Here we used field-flow fractionation with UV ICP-MS detection to measure size distribution colloidal iron, manganese, copper, uranium, chromophoric DOM six lakes over months. Five browned some degree past three decades, linear increases carbon color ranging from 0.01 0.13 mg C L −1 yr 0.13–1.94 PtCo . Browning were more pronounced colloids abundant wetlands their catchments. Iron aluminum present two primary fractions, sized nominally at 1 1000 kDa. The kDa fraction included signal, while absorbed minimally 254 nm likely represents iron-rich (oxyhydr)oxides. Colloidal manganese was 1000+ kDa, whereas copper uranium occurred primarily These associations fit a pattern DOC, region’s lakes. They represent significant challenge drinking water treatment systems, especially those remote communities. Given that browning expected continue, monitoring plans would better inform process design operation by characterizing iron-rich, inorganic contribute adverse quality outcomes.