Detecting trends in freshwater trace element concentrations: methodological issues and data treatment

Abstract

Despite the fact that the increased use of elements linked to the Anthropocene is frequently assumed to lead to an increase in the concentrations of the elements in surface waters, temporal trends of trace element (TE) concentrations have rarely been checked. A temporally extended, traceable dataset of TE concentrations in the waters of Lake Geneva, Switzerland (1996–2015) has been used here to explore methodological and data treatment issues that arise when attempting to rigorously determine temporal trends in freshwater TE concentrations. The trace elements studied (Cd, Co, Gd, Mo, Pb, Sb, Sr) have been chosen to cover a wide range of chemical and utilisation conditions. We show that detecting temporal trends from monitoring program data is feasible, even when trends are weak, provided that rigorous data treatment methods are applied. Aspects related to the effect of data quality are discussed in detail. However, ascertaining the statistical significance of any trends calculated remains a difficult issue. With the exception of Co and Sr, that show no significant changes, and Pb, that shows a general decrease, concentrations in lake waters of the trace elements considered have increased significantly, particularly between 2006 and 2015.

Arsenic in Lake Geneva (Switzerland, France): long term monitoring, and redox and methylation speciation in an As unpolluted, oligo-mesotrophic lake

“…The effect of the change of instruments on measured trace element concentrations has already been discussed for other chemical elements. 47 While improvement in precision is expected, the observed change in concentration median values remains difficult to explain. Some extent of positive error due to isobaric interferences cannot be excluded in older instruments, especially in the case of the pre-2006 instrument, a quadrupole ICP-MS without collision cell technology.…”

Functional Feeding Groups of Aquatic Insects Influence Trace Element Accumulation: Findings for Filterers, Scrapers and Predators from the Po Basin

“…These substances are derived from the dissolution of rocks or from solid or liquid atmospheric depositions [ 1 ]. Added to these natural vehicles of water enrichment is the anthropogenic input, which constitutes a major factor in environmental alteration [ 2 , 3 ]. Metal mining and industrial metal processing transfer huge masses of elements from the lithosphere (where they are immobilized in the mineral state) to the air, water, soil, and biosphere [ 4 ].…”

Water geochemical markers allow estimation of the impact of climate change on the hydrological regime of an Alpine river (River Arve, France, Switzerland)

“…ch/fr/2170.html). This data set has been used for detecting temporal trends in Lake Geneva's trace element concentrations (Rodríguez-Murillo et al 2018) and for the establishment of a methodology for water typisation according to a geochemical signature based on the concentration ratio of two chemical elements, barium and uranium (Filella et al 2014). The use of elemental ratiosa dimensionless parameterhas the unique advantage of suppressing the need for knowing water discharge.…”