Mobile Biomonitoring of Atmospheric Pollution: A New Perspective for the Moss-Bag Approach

In this work the potential of moving moss-bags, fixed to bicycles, to intercept particulate matter (PM) and linked metal(loid)s was tested for the first time. Seven volunteers carried three moss-bags for fifty days while commuting by bicycle in the urban area of Antwerp, Belgium. Moreover, one bike, equipped with mobile PM samplers, travelled along four routes: urban, industrial, green route and the total path, carrying three moss-bags at each route. The saturation isothermal remanent magnetization (SIRM) signal and chemical composition (assessed by HR-ICP-MS) of the moss samples indicated that the industrial route was the most polluted. Element fluxes (i.e., the ratio between element daily uptake and the specific leaf area) could discriminate among land uses; particularly, they were significantly higher in the industrial route for Ag, As, Cd and Pb; significantly lowest in the green route for As and Pb; and comparable for all accumulated elements along most urban routes. A comparison with a previous experiment carried out in the same study area using similar moss-bags at static exposure points, showed that the element fluxes were significantly higher in the mobile system. Finally, PM2.5 and PM10 masses measured along the four routes were consistent with element fluxes.

Assessing Human Imprints on Trace Element Fluxes in the Great Lakes

<p>The extraction and use of rare earth elements, platinum group elements and other trace metals is growing exponentially around the world. The occurrence of these trace elements in anthropogenic waste streams is increasing correspondingly. Yet, conclusive data on trace element concentrations in urban runoff and wastewater is scarce as these elements are typically not part of governmental surveillance programs and barely environmentally regulated. The human imprints on natural trace element fluxes and their potential environmental impacts therefore remain poorly quantified. We are working to quantify natural and anthropogenic trace element fluxes in the Great Lakes basin. The Great Lakes basin provides a globally unique setting to investigate human imprints on large-scale elemental cycling because it houses >60 million people, contains >20% of the world’s freshwater, and is divided into serially connected sub-basins that facilitate environmental system analyses at various scales.</p><p> </p><p>First, we established baseline estimates of current (natural) trace element fluxes in the Great Lakes by aggregating hydrometric and water quality data in simplified black-box mass-balances and dynamic reactor models. These models were informed by >100,000 hydrometric and >50,000 water quality measurements collected across the Great Lakes between 1980-2020 and were calibrated to existing long-term water level and water chemistry records. The bulk of the incorporated data stems from Canadian and US federal and provincial and state monitoring programs, including publicly available datasets from NOAA, EPA, ECCC, Ontario and Michigan state, municipalities, and local conservation authorities. Mass-balance could be achieved up to 94% for conservative elements (Cl, Na), while our dynamic models reveal significantly different source/sink behavior across the upper and lower lakes for more reactive elements. We are currently expanding our models with new ultra-trace level analyses of recent freshwater samples from cruise expeditions, major tributary rivers, and precipitation, as well as sediment records.</p><p> </p><p>Second, we considered municipal and industrial wastewater as a proxy for human activity. We collected and analyzed wastewater effluent and digested sludge samples from >40 US and Canadian wastewater treatment facilities (WWTF) and estimated, for >20 trace elements, average discharge rates into the Great Lakes basin. We compared average wastewater-effluent loads with large-scale natural biogeochemical fluxes in the Great Lakes, allowing us to rank the analyzed trace elements as well as individual lakes and tributaries by their apparent human imprint. Our results show anomalously high loading rates for select rare earth elements and precious metals in several tributary systems. Geospatial attributes of the sampled sewersheds (demographics, land use, industrial activity) serve as independent variables in our ongoing effort to source-track these anomalous loads and establish human imprints on catchment tributaries further upstream.</p>

Effects of snowmelt on the runoff dynamics in two catchments with different forest stands

<p>The forest stand can significantly affect the snow deposition and consequently the runoff during the melt period. This study focuses on water and element fluxes from snowpack in two Czech boreal headwater lake catchments with different forest stands (mature vs. regenerating after bark beetle tree dieback) using isotopic and hydrochemical tools. Sampling and analysis of the surface water, precipitation and snowpack throughout one  hydrological year enabled us to estimate the isotopic balance and chemical snowpack evolution, but also the snowmelt contribution in lakes inlets and outlets.</p><p>Isotopic signatures of the snowpack were seasonal, with δ<sup>2</sup>H amplitudes of -25‰ in the mature and -17‰ in the regenerating forest catchments. The mature forest had a ~1 month longer duration of snow cover and higher concentration of solutes in the precipitation and snowpack. In both catchments, heavier isotopes (<sup>18</sup>O and <sup>2</sup>H) preferentially left the snowpack, which was saturated with rainwater. This resulted in the final spring snowmelt being enriched with lighter isotopes (<sup>16</sup>O and <sup>1</sup>H). Ions were also eluted from the snowpack during rain-on-snow events and partial snow melting throughout the winter, causing fluxes of diluted water at the end of the snowmelt. Our results demonstrate the hydrological and hydrochemical variability of the snowpack, which in the future may even increase with rising temperatures and changes of precipitation patterns.</p>

250-year records of mercury and trace element deposition in two lakes from Cajas National Park, SW Ecuadorian Andes

Historical records of trace elements in lake sediments provide source-to-sink information about potentially toxic pollutants across space and time. We investigated two lakes located at different elevations in the Ecuadorian Andes to understand how trace element fluxes are related to (i) geology, (ii) erosion in the watersheds, and (iii) local point sources and atmospheric loads. In remote Lake Fondococha (4150 m a.s.l.), total Hg fluxes stay constant between ca. 1760 and 1950 and show an approximately 4.4-fold increase between pre-1950 and post-1950 values. The post-1950 increase in fluxes of other trace elements (V, Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) is lower (2.1–3.0-fold) than for Hg. Mostly lithogenic sources and enhanced soil erosion contribute to their post-1950 increase (lithogenic contribution: > 85%, Hg: ~ 58%). Average post-1950 Hg fluxes are approximately 4.3 times higher in peri-urban Lake Llaviucu (3150 m a.s.l.) than in the remote Lake Fondococha. Post-1950 fluxes of the other trace elements showed larger differences between Lakes Fondococha and Llaviucu (5.2 < 25–29.5-fold increase; Ni < Pb–Cd). The comparison of the post-1950 average trace element fluxes that are derived from point and airborne sources revealed 5–687 (Hg–Pb) times higher values in Lake Llaviucu than in Lake Fondococha suggesting that Lake Llaviucu’s proximity to the city of Cuenca strongly influences its deposition record (industrial emissions, traffic, caged fishery). Both lakes responded with temporary drops in trace element accumulations to park regulations in the 1970s and 1990s, but show again increasing trends in recent times, most likely caused by increase in vehicular traffic and openings of copper and gold mines around Cajas National Park.