Essential and Non-essential Elements in an Herbaceous Karst Wetland: Inputs from Urban Dust

Wetlands play an important role in biogeochemical cycles, as their hydrological and edaphic properties drive chemical reactions that facilitate the storage or transfer of various elements. Some herbaceous wetlands are ecosystems dominated by grass-like communities, sedges and rushes, and the information available at international level reveals they are poorly studied ecosystems in terms of elemental analysis. This research seeks to contribute to the understanding of herbaceous wetlands producing an inventory of essential and non-essential elements, the latter expected to be increased from the direct interaction of the wetland with a road. Several elements, divided into four major groups (macro-elements, micro-elements, trace elements and non-essential elements), were quantitatively analyzed in five environmental matrices (interstitial water, sediments, vegetal aerial parts and roots, and snail shells) as well as urban dust, for the purpose of finding out whether urban dust from the road was a fixed source of non-essential elements for the wetland. Based on our findings, we report the presence of 24 elements (calcium, potassium, magnesium, phosphorus, iron, nickel, chromium, manganese, copper, zinc, silicon, barium, cobalt, molybdenum, selenium, vanadium, sodium, aluminum, cadmium, lead, antimony, arsenic, thallium and mercury), not all of them reported in all samples. We found several elements in highest concentrations in the portion of the wetland closest to the road, in water (Cu and Tl), sediments (Fe, Cr, Cu, V and Tl), aerial tissue of the plants (Mn, Co, V, Cd, Pb and As) and plants roots (Ni, Cr, Cu, Zn, Co, Mo, V, Al, Cd, Se, Pb and As). These elements overlap with those found in urban dust (Fe, Ni, Cr, Mn, Cu, Zn, Ba, Co, V, Cd, Pb, As, Tl), supporting the hypothesis that the road might be a source of both essential and non-essential elements to the wetland.