Diel cycles in dissolved metal concentrations in streams: Occurrence and possible causes

Abstract

[1] Substantial diel (24-hour) cycles in dissolved (0.1-mm filtration) metal concentrations were observed during low flow for 18 sampling episodes at 14 sites on 12 neutral and alkaline streams draining historical mining areas in Montana and Idaho. At some sites, concentrations of Cd, Mn, Ni, and Zn increased as much as 119, 306, 167, and 500%, respectively, from afternoon minimum values to maximum values shortly after sunrise. Arsenic concentrations exhibited the inverse temporal pattern with increases of up to 54%. Variations in Cu concentrations were small and inconsistent. Diel metal cycles are widespread and persistent, occur over a wide range of metal concentrations, and likely are caused primarily by instream geochemical processes. Adsorption is the only process that can explain the inverse temporal patterns of As and the divalent metals. Diel metal cycles have important implications for many types of water-quality studies and for understanding trace-metal mobility.

Food for Thought: A Critical Overview of Current Practical and Conceptual Challenges in Trace Element Analysis in Natural Waters

“…Many studies have noted that diel cycles confound efforts to monitor contamination in streams using once-per-day sampling strategies [79]. Since sunlight is the main energy source of the ground surface, many biogeochemical phenomena affecting water follow a 24-h photocycle in response to sunlight.…”

Assessing contaminated sediments in the context of multiple stressors

“…Diurnal concentration ranges of several hundred percent have been documented [107]. Fluctuation varies by metal type and site conditions, and are driven by processes such as bioturbation, surface water and hyporheic flow, redox and photochemical reactions, precipitation/dissolution of solid mineral phases, and sorption processes.…”

“…A rapidly growing body of literature documents the common occurrence of the diurnal flux of metals and organometals between sediments, biofilms, and overlying fresh and marine waters due to a number of processes [82,83,[100][101][102][103][104][105][106][107]. Diurnal concentration ranges of several hundred percent have been documented [107].…”

Preliminary assessment of total dissolved trace metal concentrations in Sava River water

“…It was previously reported that, in some rivers, the dissolved Zn concentrations increase from late afternoon to early morning (Jones et al, 2004;Nimick et al, 2003).Therefore, the pronounced variability of total dissolved Zn can be partly a result of the river water sampling at different times of the day, or it can be a consequence of the sample handling. Further investigation is thus required to clarify the causes for high short-term variability of total dissolved Zn in river water.…”