Sizeable net export of base cations from a Carpathian flysch catchment indicates their geogenic origin while the 26Mg/24Mg, 44Ca/40Ca and 87Sr/86Sr isotope ratios in runoff are indistinguishable from atmospheric input.

Nutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base-poor flysch turbidites using magnesium (Mg), calcium (Ca) and strontium (Sr) isotope composition of 10 ecosystem compartments. Our objective was to constrain conclusions drawn from long-term hydrochemical monitoring of inputs and outputs. Annual export of Mg, Ca and Sr exceeds 5-to-15 times their atmospheric input. Mass budgets per se thus indicate sizeable net leaching of Mg, Ca and Sr from bedrock sandstones and claystones. Surprisingly, δ26Mg, δ44Ca and 87Sr/86Sr isotope ratios of runoff were practically identical to those of atmospheric deposition and soil water but significantly different from bedrock isotope ratios. We did not find any carbonates in the studied area as a hypothetical, easily dissolvable source of base cations whose isotope composition might corroborate the predominance of geogenic base cations in the runoff. Marine carbonates typically have lower δ26 Mg and 87Sr/86Sr ratios, and silicate sediments often have higher δ26Mg and 87Sr/86Sr ratios than runoff at the study site. Mixing of these two sources, if confirmed, could reconcile the flux and isotope data.

Accumulation and within-mushroom distribution of elements in red cracking bolete (Xerocomellus chrysenteron) collected over the extended period from compositionally contrasting substrates.

We conducted a study of elemental compositions of Xerocomellus chrysenteron samples accompanied by samples of related substrate soils. All samples were collected during the harvesting seasons 2021 and 2022 from three forested sites almost unpolluted by recent human activities and underlain by contrasting bedrock (granite, amphibolite, and serpentinite). Elements such as Ag, Cd, K, P, Rb, S, Se, and Zn were the main elements enriched in the mushroom's fruiting bodies relative to the substrate. Concentrations of most elements in mushrooms were not site-dependent, with only Ag, As, Rb, and Se concentrations significantly depending on the bedrock composition. Some elements analyzed in mushrooms displayed temporal features, but such features were not systematic and varied for each element. Most analyzed elements were distributed unevenly within the mushroom's fruiting bodies, with apical parts generally enriched in mobile elements. Mushrooms influenced concentrations of Ag, Cd, K, and Rb and a few other elements in the substrate via uptake, but such influence was very limited and can be responsible for only 2.5-11.5% of total depletion of the affected substrate in the named elements.

Translocation of elements and fractionation of Mg, Cu, Zn, and Cd stable isotopes in a penny bun mushroom (Boletus edulis) from western Czech Republic.

Boletus edulis mushroom behaved as an accumulating biosystem with respect to Ag, Rb, Zn, and K. The mushroom was not an efficient accumulator of toxic As, Pb, and Cr, but Se and Cd displayed much higher concentrations in the mushroom than in the substrate samples. Other elements were bioexclusive. Different elements had different within-mushroom mobilities. The highest mobilities were displayed by Zn and Ag, and the lowest by Ti. The mushroom's fruiting body preferentially took up lighter Mg, Cu, and Cd isotopes (Δ26MgFB-soil = -0.75‰; Δ65CuFB-soil = -0.96‰; Δ114CdFB-soil = -0.63‰), and the heavier 66Zn isotope (Δ66ZnFB-soil = 0.92‰). Positive within-mushroom Zn isotope fractionation resulted in accumulation of the heavier 66Zn (Δ66Zncap-stipe = 0.12‰) in the mushroom's upper parts. Cadmium displayed virtually no within-mushroom isotope fractionation. Different parts of the fruiting body fractionated Mg and Cu isotopes differently. The middle part of the stipe (3-6 cm) was strongly depleted in the heavier 26 Mg with respect to the 0-3 cm (Δ26Mgstipe(3-6)-stipe(0-3) = -0.73‰) and 6-9 cm (Δ26Mgstipe(6-9)-stipe(3-6) = 0.28‰) sections. The same stipe part was strongly enriched in the heavier 65Cu with respect to the 0-3 cm (Δ65Custipe(3-6)-stipe(0-3) = 0.63‰) and 6-9 cm (Δ65Custipe(6-9)-stipe(3-6) = -0.42‰) sections. An overall tendency for the upper mushroom's parts to accumulate heavier isotopes was noted for Mg (Δ26Mgcap-stipe = 0.20‰), Zn (Δ66Zncap-stipe = 0.12‰), and Cd (Δ114Cdcap-stipe = 0.04‰), whereas Cu showed the opposite trend (Δ65Cucap-stipe = -0.08‰).

First data on isotope and trace element compositions of a Xerocomus subtomentosus mushroom sample from western Czech Republic.

A study of a sample of Xerocomus subtomentosus revealed that the fruiting body behaved as an accumulating biosystem with respect to Rb (BF = 36), K and Ag (BF = 5.0 for both), and, to a lesser extent, Mg, Cu, Zn, and Se (BF = 1.7-3.1). A Xerocomus mushroom has not shown to be a good accumulator of toxic As (BF = 0.64), Cd (BF = 0.65), and Pb and Cr (BF < 0.1 for both) from the soil. Within-mushroom distribution of the trace elements showed very high mobility of Ag (TF = 54) and As (TF = 16); moderate mobility of K, Ti, Pb, and Rb (TF = 2.1-3.1); and low mobility to immobility of other elements. A mushroom preferentially intakes isotopically heavy Mg (Δ26Mgstipe-soil = 0.22‰) and Zn (Δ66Znstipe-soil = 0.68‰), and isotopically light Cu (Δ65Custipe-soil = - 1.04‰). The fruiting body has shown insignificant but measurable within-mushroom isotope fractionation with the higher parts of the fruiting body accumulating isotopically lighter Cu (Δ65Cucap-stipe = - 0.06‰), Zn (Δ66Zncap-stipe = - 0.18‰), and Mg (Δ26Mgcap-stipe = - 0.31‰). Such a behavior is overall similar to that displayed by the higher plants.

Catchment Runoff in Industrial Areas Exports Legacy Pollutant Zinc from the Topsoil Rather than Geogenic Zn.

In highly industrialized, densely populated parts of Central Europe, mobilization of legacy Zn pollution from forest ecosystems may negatively affect the quality of water resources. To test this hypothesis, we determined the 66Zn/64Zn isotope ratios of 15 Zn reservoirs and fluxes in an acidified, spruce die-back affected mountain-slope catchment in northern Czech Republic. The δ66Zn values of precipitation, organic horizon, and runoff were statistically indistinguishable. In contrast, δ66Zn values of bedrock orthogneiss and mineral soil were significantly different from δ66Zn values of runoff. The magnitude of within-site Zn isotope fractionations appeared to be relatively small. Despite the large potential source of Zn in bedrock, runoff exported mostly young pollutant Zn that had been temporarily stored in the organic horizon. This conclusion was corroborated by comparing Zn input-output mass balances in the polluted northern catchment and in a relatively unpolluted catchment situated 250 km to the south. Seven-times higher Zn export via runoff at the northern site was controlled by a combination of 10-times higher atmospheric Zn input and five-times higher DOC leaching, compared to the southern site. In industrial areas, atmospherically deposited Zn is leached from headwater catchments in a direct analogy to leaching of highly toxic pollutant Pb.