Localization, ligand environment, bioavailability and toxicity of mercury in Boletus spp. and Scutiger pes-caprae mushrooms

Mass spectrometry imaging reveals flavor distribution in edible mushrooms

The spatial distribution of molecules and compounds responsible for the flavor profile of edible button mushrooms (Agaricus bisporous) has never been determined. The food industry is interested in knowing the localization of these compounds. Such knowledge would enable extraction of flavor compounds from a particular regions of the mushroom, which is safer for consumption compared to alternatives such as synthetic flavoring agents. The present study utilizes matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI), to determine the spatial distribution of flavor compounds in a mushroom. As MALDI-MSI requires very thin sections, a sample preparation protocol was optimized and sectioning fresh frozen mushrooms at 35 µm thickness was considered the best method to evaluate the distribution of flavor compounds. Further, the effect of heat on the spatial distribution of flavor compounds was investigated by heating whole mushrooms to 140 ℃ prior to sectioning. Heating reduced the water content of the mushroom and thus enabled the generation of even-thinner 17 µm thick sections. MALDI-MSI measurements performed on underivatized and on-tissue derivatized fresh frozen and heat-treated mushroom sections elucidated the spatial distribution of several flavor-related compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-023-05883-0.

The potential of microorganisms as biomonitoring and bioremediation tools for mercury-contaminated soils

Mercury (Hg) pollution is a global issue due to the high toxicity and wide dispersion of Hg around the world. Whether due to anthropogenic activities or natural processes, Hg emissions are steadily increasing, with very high levels in some regions, directly threatening human and ecosystem health. However, bacteria and fungi have evolved and adapted in response to Hg-induced stress and have developed tolerance mechanisms, notably based on the mer operon system that is involved in Hg uptake and biovolatilization via Hg reduction reactions. Other processes, such as bioaccumulation or extracellular sequestration, are involved in Hg resistance, and the study of contaminated soils has allowed the isolation of a number of microorganisms capable of these mechanisms, with strong potential for the implementation of bioremediation approaches. In addition to playing an important role in determining the fate of Hg in the biogeochemical cycle, these microorganisms can indeed be applied to reduce Hg concentrations or at least stabilize Hg for the remediation of polluted soils. Moreover, thanks to the development of biotechnological tools, bioremediation based on Hg-tolerant microorganisms can be optimized. Finally, these microorganisms are relevant candidates for biomonitoring, for example, through the engineering of biosensors, because the detection of Hg is a major issue in preserving the health of living beings.

Feasibility study for mercury remediation by selenium competition in Pleurotus mushrooms

Mushrooms may incorporate significant levels of Hg making its consumption harmful to human health. Mercury remediation induced by Se competition in edible mushrooms represents a valuable alternative since Se plays effective roles against Hg uptake, accumulation, and toxicity. In this way, Pleurotus ostreatus and Pleurotus djamor were cultivated on Hg-contaminated substrate simultaneously supplemented with Se(IV) or Se(VI) under different dosages in this study. The protective role of Se was assessed taking into account morphological characteristics and Hg and Se total concentrations determined by ICP-MS, as well as proteins and protein-bound Hg and Se distribution by SEC-UV-ICP-MS, and Hg speciation studies (Hg(II) and MeHg) by HPLC-ICP-MS. Both Se(IV) and Se(VI) supplementation were able to recover the morphology mainly of Hg-contaminated Pleurotus ostreatus. The mitigation effects induced by Se(IV) stood out more than Se(VI) in terms of Hg incorporation, decreasing the total Hg concentration up to 96 %. Also, it was found that supplementation mainly with Se(IV) reduced the fraction of Hg bound to medium molecular weight compounds (17-44 kDa) up to 80 %. Finally, it was shown a Se-induced inhibitory effect on Hg methylation, decreasing MeHg species content in mushrooms exposed to Se(IV) (51.2 µg g^-1) up to 100 %.

Quantitative mapping of mercury and selenium in mushroom fruit bodies with laser ablation-inductively coupled plasma-mass spectrometry

This work describes the development of a novel method for quantitative mapping of Hg and Se in mushroom fruit body tissues with laser ablation coupled to inductively coupled plasma-mass spectrometry (LA-ICP-MS). Different parameters of the protocol for preparation of the standards used for quantification via external calibration were assessed, e.g., the dissolution temperature of gelatin standards and the addition of chitosan and L-cysteine as additives to the gelatin-based calibration droplets to better match the sample matrix. While chitosan was not suited for this purpose, the presence of L-cysteine considerably improved the figures of merit of the calibration, leading to limits of detection of 0.006 and 0.3 µg g-1 for Hg and Se, respectively, at a pixel size of 20 × 20 µm. Further, an in-house reference material, ideally suited for the validation of the method for application to mushroom samples, was successfully prepared from a paste of Boletus edulis. The newly developed method was used to investigate the distribution of Hg and Se in tissue sections of five porcini mushroom individuals of three different species (Boletus edulis, Boletus aereus, and Boletus pinophilus) and one sample of a parasol mushroom (Macrolepiota procera). For one sample, additional areas were ablated at higher spatial resolution, with a laser spot size down to 5 µm, which allows a detailed investigation of the spatial distribution of Hg and Se in mushrooms.

A method for the analysis of methylmercury and total Hg in fungal matrices

The aim of the study was to develop an efficient method for the determination of monomethyl-mercury (MeHg) and total mercury (THg) content in materials such as fungal sporocarps and sclerotia. Certified Reference Materials (CRMs) with the assigned values of MeHg and THg as well as the control materials (dried mushrooms) with known content of THg were evaluated for method validation. Recovery of MeHg from reference materials was at the following levels: from tuna fish at 87.0 ± 2.3% (THg at 101.9 ± 1.2%), from fish protein at 99.4 ± 1.3% (THg at 92.70 ± 0.41%), and from dogfish liver at 96.45 ± 0.73%. Recovery of THg from the fungal control material CS-M-5 was at 104.01 ± 0.60% (contribution of MeHg in THg content was at 6.2%), from CS-M-4 at 101.1 ± 2.0% (contribution at 3.2%), from CS-M-3 at 100.55 ± 0.67% (contribution at 0.6%), and from CS-M-2 at 101.5 ± 2.7% (contribution at 3.7%). The content of MeHg in randomly selected wild fungi and their morphological parts was in the range from 0.006 to 0.173 mg kg^-1 dry weight (dw). In the case of THg, the concentration values were in the range from 0.0108 to 10.27 mg kg^-1 dw. The MeHg content in the control materials with the assigned THg values was determined. Since the control materials play an important role in all elements of the quality assurance system of measurement results, they can be used to analyse MeHg as the first control material for fungi. KEY POINTS: • An extraction procedure for MeHg analysis in fungi was developed and optimized. • Recovery of MeHg from the certified reference non-fungal materials was > 87%. • Fungal control materials with assigned THg concentration can serve also for MeHg analysis.

Occurrence and Health Risk Assessment of Cadmium Accumulation in Three Tricholoma Mushroom Species Collected from Wild Habitats of Central and Coastal Croatia

This study deals with the biomonitoring of cadmium (Cd) heavy metal in the three selected Tricholoma mushroom species collected from wild habitats of central and coastal Croatia. For this, mushroom (T. columbetta: n = 38, T. portentosum: n = 35, and T. terreum: n = 34) and surface soil samples were collected from nine forest localities of Croatia and analyzed for Cd concentration using inductively coupled plasma−optical emission spectrometry (ICP−OES) through the acid digestion method. The findings revealed that Cd was present in Tricholoma spp. and surface soil. However, the maximum mean Cd concentration (mg/kg dry weight) was recorded in T. portentosum (cap: 0.98; stipe: 0.72), followed by T. columbetta (cap: 0.96; stipe: 0.73) and T. terreum (cap: 0.81; stipe: 0.63). The bioconcentration factor (BCF) value (>1) revealed that the selected Tricholoma spp. had the potential for Cd accumulation. Moreover, the principal component (PC) and hierarchical cluster (HC) analyses were used to derive the interactions and similarities between Cd levels Tricholoma spp. and sampling localities. The multivariate analysis suggested that central sampling localities had higher Cd levels as compared to coastal localities. However, the daily intake of metals (DIM < 0.426) and health risk index (HRI < 1) showed that there was no potential health risk associated with the consumption of selected Tricholoma spp. The findings of this study are helpful to understand the Cd accumulation behavior of wild edible Tricholoma spp. collected from Croatia.

Mercury in scarletina bolete mushroom (Neoboletus luridiformis): Intake, spatial distribution in the fruiting body, accumulation ability and health risk assessment

In the present work, we focused on two aspects of mercury (Hg) bioconcentration in the above-ground parts of Neoboletus luridiformis. In the first part, we monitored the bioconcentration potential of individual anatomical parts of a particular fruiting body and evaluated the obtained data by the spline interpolation method. In the second part, we focused on assessing the mercury content in 378 samples of N. luridiformis and associated samples of substrates from 38 localities with different levels of Hg content in Slovakia. From the obtained data of Hg content in samples of substrate and fungi, we evaluated ecological indicators (geoaccumulation index - Igeo, contamination factor - Cf a potential ecological risk - PER), bioconcentration indicators (bioconcentration factor - BCF; cap/stipe quotient - Qc/s) and health indicators (percentage of provisional tolerable weekly intake - %PTWI a target hazard quotient - THQ). Based on the Hg distribution results, the highest Hg content was found in the tubes & pores (3.86 mg/kg DW), followed by the flesh of cap (1.82 mg/kg DW). The lowest Hg content was in the stipe (1.23 mg/kg DW). The results of the BCF values indicate that the studied species can be included in the category of mercury accumulators. The results of the ecological indices representing the state of soil pollution pointed out that two localities (Malachov and Nižná Slaná) stood apart from all monitored localities and showed a state of an extremely disturbed environment. This fact was also reflected in the values of Hg content in the fruiting bodies of the studied mushroom species. In the case of the consumption of mushrooms from these localities, it can be stated that long-term and regular consumption could have a negative non-carcinogenic effect on the health of consumers. It was confirmed by the %PTWI (Malachov: 57.8%; Nižná Slaná: 53.2%) and THQ (Malachov: 1.11 Nižná Slaná: 1.02). The locality Čačín-Jelšovec is interesting from the bioconcentration characteristics point of view, where the level of environmental pollution was the lowest (Hg content in the soil was below the background value) compared to other localities, however, the THQ value was the highest (1.29).

Total mercury and methylmercury (MeHg) in braised and crude Boletus edulis carpophores during various developmental stages

We collected and processed Boletus edulis (King Bolete) carpophores grouped in four batches based on their developmental stage (button stage, young-white, large-white, and large-yellow). The study aimed, for the first time, to examine the B. edulis content and effect of braising and to estimate the intake of total mercury (THg) and methylmercury (MeHg) from a single meal based on whole (wet) weight (ww) and dry weight (dw). In braised carpophores, THg concentrations ranged from 0.2668 ± 0.0090 to 0.5434 ± 0.0071 mg kg^-1 ww at different developmental stages, whereas crude products concentrations ranged from 0.1880 ± 0.0247 to 0.2929 ± 0.0030 mg kg^-1 ww. The button stage crude carpophores were more highly contaminated with THg than at later stages of maturity, but MeHg levels were lower (p < 0.0001). On the other hand, braised button stage carpophores showed more MeHg than at later maturity stages. MeHg contributed at 1.9 ± 0.7% in THg in crude mushrooms and at 1.4 ± 0.3% in braised meals. The effect of braising was to increase the average THg and MeHg contents in fresh mushroom meals by 52 ± 31% and 53 ± 122% respectively, but a reduction of 40 ±14% and 40 ± 49% respectively was seen on a dw basis. The potential intakes of THg and MeHg from braised meals of B. edulis studied were small and considered safe.

Cadmium and Lead Content in Selected Fungi from Poland and Their Edible Safety Assessment

Mushrooms are able to accumulate toxic trace elements. This study investigates the content of cadmium (Cd) and lead (Pb) in selected species of fungi (Boletus badius, Boletus edulis, and Cantharellus cibarius) from the northeastern part of Poland and estimates their edible safety. The amount of Cd and Pb was determined by flameless atomic spectrometry using the iCE 3000 Series-Thermo. The mean content of Cd in analyzed mushrooms ranged from 0.370 to 2.151 mg/kg d.w., while Pb was found at the level of 0.243–0.424 mg/kg d.w. Boletus edulis was characterized by the highest content of Cd, whereas Cantharellus cibarius contained the biggest amount of Pb. Estimated exposure to the Cd intake expressed as percentage share in TWI (Tolerable Weekly Intake) was at the highest level in Boletus edulis (30.87%), which could be associated with the risk of excessive Cd accumulation in the body.

Mercury and selenium in developing and mature fruiting bodies of Amanita muscaria

Both mercury (Hg) and selenium (Se) occur in many mushroom species, but the morphological distribution of these elements during different developmental stages of the fruiting bodies is not known. Although Amanita muscaria can be consumed after suitable processing, they are often ignored by mushroom foragers, leaving an abundance for investigative study. Multiple specimens in each of six developmental stages (button to fully mature) were collected in excellent condition during a single morning from the same forested location and composited. With an average of 30 specimens per composite, and low temporal, spatial, and measurement uncertainty, the data are likely to be representative of the typical concentrations of Hg and Se for each developmental stage. Hg (range 0.58-0.74 mg kg^-1 dry weight cap; 0.33 to 0.44 mg kg^-1 dw stipe) and Se (range 8.3-11 mg kg^-1 dw cap; 2.2 to 4.3 mg kg^-1 dw stipe) levels were observed to vary during the developmental stages, and the variability may relate to the demands in growth. In common with some other species, the lower stipe concentrations may be consistent with nutrient/contant transport and support functions. Both Hg and Se levels were lowest during periods of maximum sporocarp growth. Selenium occurs at almost an order of magnitude greater levels than Hg. Due to its role in mitigating the effects of Hg toxicity, this property is of significance to those who consume the species either for nutritional, medicinal, or recreational purposes, although the losses of both these elements during processing are not known.

Lithiation of white button mushrooms (Agaricus bisporus) using lithium-fortified substrate: effect of fortification levels on Li uptake and on other trace elements

High doses of lithium salts are used for the treatment or prevention of episodes of mania in bipolar disorder, but the medication is rapidly excreted and also shows side effects. Li may also be beneficial in people with mood disorders. Nutritionally, popular foods such as wild and cultivated mushrooms have low Li contents. This study evaluated the Li enrichment of white Agaricus bisporus mushrooms using Li₂CO₃ solutions to fortify the commercial growing substrate at various concentrations from 1.0 to 500 mg kg^-1 dry weight (dw). Fortification of up to 100 mg kg^-1 dw resulted in a significant (p < 0.01) dose-dependent increase in the accumulation of Li in mushroom, but the highest fortification level was found to be detrimental to fruitification. The median values of Li in fortified mushrooms corresponded to the fortification levels, increasing from 0.49 to 17 mg kg^-1 dw relative to the background concentration of 0.056 mg kg^-1 dw (control substrate contained 0.10 mg kg^-1 dw). The potential for Li uptake in fruiting bodies was found to decrease at higher levels of fortification, with saturation occurring at 100 mg kg^-1. Resulting lithiated mushrooms were up to 300-fold richer in Li content than specimens grown on control substrate. The fortification showed some effects on the uptake of other trace minerals, but concentrations of co-accumulated Ag, Al, As, Ba, Cd, Co, Cr, Cs, Cu, Hg, Mn, Ni, Pb, Rb, Sr, Tl, U, V and Zn were similar or lower than values reported in the literature for commercial A. bisporus. These lithiated mushrooms could be considered as a pro-medicinal alternative to treatments that use Li salts.

Lithiation of Agaricus bisporus mushrooms using compost fortified with LiOH: Effect of fortification levels on Li uptake and co-accumulation of other trace elements

This study investigated the lithiation of white Agaricus bisporus (common button) mushrooms using compost fortified with LiOH solutions at concentrations from 1 to 500 mg kg^-1 compost dw. Apart from the highest level of fortification, the median Li concentrations in the cultivated mushrooms were elevated from 0.74 to 21 mg kg^-1 dw (corresponding to compost fortification from 1.0 to 100 mg LiOH, kg^-1 dw), relative to control mushrooms at 0.031 mg kg^-1 dw. The bio-concentration potential for Li uptake in fruiting bodies was found to decrease at higher levels of fortification e.g. 50 - 100 mg kg^-1 dw, and at the highest level - 500 mg kg^-1, the mycelium failed to produce mushrooms. The fortification of the compost with LiOH appears to have had little, if any, effect on the co-accumulation of other elements such as Ag, Al, As, Ba, Cd, Co, Cr, Cs, Cu, Hg, Mn, Ni, Pb, Rb, Sr, Tl, U, V and Zn in the fruiting bodies, which generally occurred at the lower range of the results reported in the literature for cultivated A. bisporus. Thus compost fortification with LiOH provides an effective means of lithiating A. bisporus for potential pro-therapeutic use.

The use of Li2O fortified growing compost to enhance lithiation in white Agaricus bisporus mushrooms: Li uptake and co-accumulation of other trace elements

In an attempt to enrich the fruiting bodies with Lithium (Li), this study cultivated mushrooms using growing sets that were fortified with Li2O at 1.0, 5.0, 10, 50, 100 and 500 mg·kg−1 dw. Compost fortification up to 100 mg·kg−1 dw induced a dose-dependent increase in Li accumulation with resulting median mushroom concentrations of 2.0, 8.6, 16, 29 and 38 mg·kg−1 dw, respectively, relative to the unfortified control at 0.087 mg·kg−1 dw. The dose dependency appears to level off as Li2O addition approaches 100 mg·kg−1, suggesting that there is a limit to the ability of the species to accumulate/tolerate Li. Mushrooms did not grow at the 500 mg·kg−1 dw fortification level. At the highest viable level of fortification (100 mg·kg−1 dw), the fruiting bodies were around 440-fold richer in Li content than the control mushrooms. Additionally, the fortification at all levels up to 100 mg·kg−1 dw showed very low, if any, effect on the co-accumulation of the other, studied trace mineral constituents, with concentrations occurring at the lower range of those reported for commercial A. bisporus mushrooms.

Analytical Methodologies for Agrometallomics: A Critical Review

Agrometallomics, as an independent interdiscipline, is first defined and described in this review. Metallic elements widely exist in agricultural plants, animals and edible fungi, seed, fertilizer, pesticide, feedstuff, as well as the agricultural environment and ecology, and even functional and pathogenic microorganisms. So, the agrometallome plays a vital role in molecular and organismic mechanisms like environmetallomics, metabolomics, proteomics, lipidomics, glycomics, immunomics, genomics, etc. To further reveal the inner and mutual mechanism of the agrometallome, comprehensive and systematic methodologies for the analysis of beneficial and toxic metals are indispensable to investigate elemental existence, concentration, distribution, speciation, and forms in agricultural lives and media. Based on agrometallomics, this review summarizes and discusses the advanced technical progress and future perspectives of metallic analytical approaches, which are categorized into ultrasensitive and high-throughput analysis, elemental speciation and state analysis, and spatial- and microanalysis. Furthermore, the progress of agrometallomic innovativeness greatly depends on the innovative development of modern metallic analysis approaches including, but not limited to, high sensitivity, elemental coverage, and anti-interference; high-resolution isotopic analysis; solid sampling and nondestructive analysis; metal chemical species and metal forms, associated molecular clusters, and macromolecular complexes analysis; and metal-related particles or metal within the microsize and even single cell or subcellular analysis.

Comparative study of As (V) uptake in aqueous medium by a polymer inclusion membrane-based passive sampling device and two filamentous fungi (Aspergillus niger and Rhizopus sp.)

In this work a polymer inclusion membrane (PIM) is proposed as passive sampler material and compared with two filamentous fungi for As (V) uptake to evaluate its ability as chemical surrogate material for the monitoring of this metalloid in aquatic environments. Results show excellent passive sampling characteristics of the device since a linear uptake profile as a function of time was observed. The correlation coefficients between the PIM passive sampler with Aspergillus niger (r = 0.83) and Rhizopus sp. (r = 0.13) uptake, show that the first species is the best modeled by the PIM, suggesting its potential as a chemical substitute in bioavailability studies.

The level of selected organochlorine compounds residues in popular edible mushrooms from north-eastern Poland

Although DDT, γ-HCH and PCBs have been almost completely withdrawn from world production and use, they are still present in the environment. Mushrooms are eagerly collected and consumed local raw material in north-eastern part of Poland. The aim of the study was to determine the content of DDT, γ-HCH and PCB residues in popular species (Boletus badius, Boletus edulis, Cantharellus cibarius) and to estimate the human exposure of uptaking of these compounds with mushrooms. The content of γ-HCH, DDT and PCB was determined using gas chromatography. The presence of analyzed compounds was observed in all the species under study. The highest content of γ-HCH and ΣDDT was determined in C. cibarius - 7.19 and 180.37 µg/kg of lipids, respectively, whereas the highest amount of ΣPCB was observed in B. edulis - 20.89 µg/kg of lipids. The contents were low and did not pose a threat to human health.

Mercury in traditionally foraged species of fungi (macromycetes) from the karst area across Yunnan province in China

The objective of this study is to better quantify the occurrence, intake, and potential risk from Hg in fungi traditionally foraged in SW China. The concentrations and intakes of Hg were measured from 42 species including a "hard" flesh type polypore fungi and a" soft" flesh type edible species that are used in traditional herbal medicine, collected during the period 2011-2017. Three profiles of forest topsoil from the Zhenyuan site in 2015 and Changning and Dulong sites in 2016 were also investigated. The concentrations of Hg in composite samples of polypore fungi were usually below 0.1 mg kg-1 dry weight (dw) but higher levels, 0.11 ± 0.01 and 0.24 ± 0.00 mg kg-1 dw, were noted in Ganoderma applanatum and Amauroderma niger respectively, both from the Nujiang site near the town of Lanping in NW Yunnan. Hg concentrations in Boletaceae species were usually well above 1.0 mg kg-1 dw and as high as 10 mg kg-1 dw. The quality of the mushrooms in this study in view of contamination with Hg showed a complex picture. The "worst case" estimations showed probable intake of Hg from 0.006 μg kg-1 body mass (bm) ("hard" type flesh) to 0.25 μg kg-1 bm ("soft" flesh) on a daily basis for capsulated products, from 17 to 83 μg kg-1 bm ("soft" flesh) in a meal ("hard" type flesh mushrooms are not cooked while used in traditional herbal medicine after processing), and from 0.042 to 1.7 and 120 to 580 μg kg-1 bm on a weekly basis, respectively. KEY POINTS: • Polypore species were slightly contaminated with Hg. • Hg maximal content in the polypore was < 0.25 mg kg-1 dry weight. • Many species from Boletaceae family in Yunnan showed elevated Hg. • Locals who often eat Boletus may take Hg at a dose above the daily reference dose.

Interactions between Hg and soil microbes: microbial diversity and mechanisms, with an emphasis on fungal processes

Mercury (Hg) is a highly toxic metal with no known biological function, and it can be highly bioavailable in terrestrial ecosystems. Although fungi are important contributors to a number of soil processes including plant nutrient uptake and decomposition, little is known about the effect of Hg on fungi. Fungi accumulate the largest amount of Hg and are the organisms capable of the highest bioaccumulation of Hg. While referring to detailed mechanisms in bacteria, this mini-review emphasizes the progress made recently on this topic and represents the first step towards a better understanding of the mechanisms underlying Hg tolerance and accumulation in fungal species and hence on the role of fungi within the Hg cycle at Hg-contaminated sites. KEY POINTS: • The fungal communities are more resilient than bacterial communities to Hg exposure. • The exposure to Hg is a threat to microbial soil functions involved in both C and nutrient cycles. • Fungal (hyper)accumulation of Hg may be important for the Hg cycle in terrestrial environments. • Understanding Hg tolerance and accumulation by fungi may lead to new remediation biotechnologies.

Contamination, bioconcentration and distribution of mercury in Tricholoma spp. mushrooms from southern and northern regions of Europe

The contamination, bio-concentration and distribution of mercury (Hg) in wild mushrooms of the genus Tricholoma such as T. equestre, T. portentosum, T. columbeta, and T. terreum were studied, and the possible dietary intake and risk for human consumers in Europe was estimated. Mushrooms, together with the associated forest topsoils were collected from 10 unpolluted and geographically distant areas, far from local or regional emission sources, in Poland (2 sites) and Croatia (8 sites). The Hg contents were in the range 0.10 ± 0.06 to 0.71 ± 0.34 mg kg^-1 dry matter in caps and 0.04 ± 0.02 to 0.38 ± 0.13 mg kg^-1 in stems. The corresponding topsoil concentrations varied over a relatively narrow range between sites, from 0.013 ± 0.003 to 0.028 ± 0.006 mg kg^-1 dry matter. Overall, the study results showed low levels of mercury both, in edible Tricholoma mushrooms and forest topsoils from background (unpolluted) forested areas in Croatia and Poland. The morphological distribution showed considerably greater concentrations of mercury in the caps relative to the stems with ratios ranging from 1.6 ± 0.6 to 3.9 ± 1.8. T. equestre showed good ability to bioconcentrate Hg, with bioconcentration factors (BCF) values in the range 18 ± 7 to 37 ± 18. The data suggests that Tricholoma mushrooms from unpolluted areas in southern and northern regions of Europe can be considered as a low risk food from the point of view of the tolerable Hg intake.

Occurrence, distribution and estimated intake of mercury and selenium from sclerotia of the medicinal fungus Wolfiporia cocos from China

The contamination and distribution of mercury and selenium in the Chinese medicinal fungus Wolfiporia cocos was investigated. The sclerotial mercury concentrations ranged from 0.0043 to 0.027 mg kg¹ dry biomass (db) in the inner white part and 0.019-0.074 mg kg^-1 db in the shell (outer part), while selenium concentrations ranged from < 0.00048 to 0.0040 mg kg^-1 db (white) and 0.0034-0.038 mg kg^-1 db (shell). Positive correlations were found for mercury, as well as for mercury and selenium but they were not consistent for both morphological parts. Mercury concentrations exceeded selenium in 16 of 17 white part pools (molar quotient 0.53 to > 10) and in 11 of 17 shell pools (quotient 0.37 to 3.2). The estimated maximal exposure to mercury contained in sclerotial products based on 45 g per capita daily intake for a 60 kg individual over one week, was 0.000020 mg kg^-1 body mass (bm; white) and 0.000055 mg kg^-1 bm (shell) on a daily basis, and 0.00014 mg kg^-1 bm (white) and 0.00039 mg kg^-1 bm (shell) on a weekly basis. Relative to mercury, the corresponding intake rates of selenium were considered very low, i.e., they averaged on a daily basis at 0.00075 μg kg^-1 bm (white) and 0.0097 μg kg^-1 bm (shell) with maximum intake at 0.0030 μg kg^-1 bm (white) and 0.028 μg kg^-1 bm (shell).

Metallic and metalloid elements in various developmental stages of Amanita muscaria (L.) Lam

There is growing evidence that mushrooms (fruiting bodies) can be suitable for biogeochemical prospecting for minerals and as indicators of heavy metal and radioactive contaminants in the terrestrial environment. Apart from the nutritional aspect, knowledge of accumulation dynamics and distribution of elements in fruiting bodies, from emergence to senescence, is essential as is standardization when choosing mushroom species as potential bioindicators and for monitoring purposes. We studied the effect of fruitbody developmental stage on the contents of the elements (Li, K, V, Cr, Mn, Mg, Co, Ni, Cu, Zn, As, Rb, Sr, Ag, Al, Cd, Sb, Cs, Ba, Pb, Tl and U) in the individual parts of the Amanita muscaria fruiting body. Elements such as K, Mg, Mn, Ni, Co, Cu, Zn and Se remained similar throughout all developmental stages studied, however for K, differences occurred in the values of caps and stipes, as expressed by the cap to stipe concentration quotient (index Q_C/S). The other elements quantified, i.e., Li, V, Cr, As, Rb, Sr, Ag, Al, Cd, Sb, Cs, Ba, Pb, Tl and U are considered as nonessential or toxic (with the exception of V in A. muscaria). Their accumulation in the fruiting bodies and their distribution between cap and stipe did not show a uniform pattern. Pb, Sb, Tl, Ba, Sr, Li, Rb and Cs decreased with increasing maturity of the fruitbodies, implying that translocation, distribution and accumulation in stipes and caps was not a continuous process, while V, Cr, As, Ag, Cd, and U remained at the same concentration, similarly to the essential elements. Our results for A. muscaria confirm that elemental distribution in different parts of fruiting bodies is variable for each element and may change during maturation. Soil properties, species specificity and the pattern of fruitbody development may all contribute to the various types of elemental distribution and suggest that the results for one species in one location may have only limited potential for generalization.

The effects of selenium biofortification on mercury bioavailability and toxicity in the lettuce-slug food chain

The effects of foliar Se biofortification (Se+) of the lettuce on the transfer and toxicity of Hg from soil contaminated with HgCl2 (H) and soil collected near the former Hg smelter in Idrija (I), to terrestrial food chain are explored, with Spanish slug as a primary consumer. Foliar application of Se significantly increased Se content in the lettuce, with no detected toxic effects. Mercury exerted toxic effects on plants, decreasing plant biomass, photochemical efficiency of the photosystem II (Fv/Fm) and the total chlorophyll content. Selenium biofortification (Se+ test group) had no effect on Hg bioaccumulation in plants. In slugs, different responses were observed in H and I groups; the I/Se+ subgroup was the most strongly affected by Hg toxicity, exhibiting lower biomass, feeding and growth rate and a higher hepatopancreas/ muscle Hg translocation, pointing to a higher Hg mobility in comparison to H group. Selenium increased Hg bioavailability for slugs, but with opposite physiological responses: alleviating stress in H/Se+ and inducing it in I/Se+ group, indicating different mechanisms of Hg-Se interactions in the food chain under HgCl2 and Idrija soil exposures that can be mainly attributed to different Hg speciation and ligand environment in the soil.

137Cs and 40K in Cortinarius caperatus mushrooms (1996-2016) in Poland - Bioconcentration and estimated intake: 137Cs in Cortinarius spp. from the Northern Hemisphere from 1974 to 2016

Cortinarius caperatus grows in the northern regions of Europe, North America and Asia and is widely collected by mushroom foragers across Europe. This study shows that in the last three decades since the Chernobyl nuclear accident, C. caperatus collected across much of Northern Poland exhibited high activity concentrations of radiocaesium (¹³⁷Cs) - a long-lived radionuclide. The mushroom appears to efficiently bioconcentrate ¹³⁷Cs from contaminated soil substrata followed by sequestration into its morphological parts such as the cap and stipe which are used as food. The gradual leaching of ¹³⁷Cs into the lower strata of surface soils in exposed areas are likely to facilitate higher bioavailability to the mycelia of this species which penetrate to relatively greater depths and may account for the continuing high activity levels noticed in Polish samples (e.g. activity within caps in some locations was still at 11,000 Bq kg^-1 dw in 2008 relative to a peak of 18,000 in 2002). The associated dietary intake levels of ¹³⁷Cs have often exceeded the tolerance limits set by the European Union (370 and 600 Bq kg^-1 ww for children and adults respectively) during the years 1996-2010. Human dietary exposure to ¹³⁷Cs is influenced by the method of food preparation and may be mitigated by blanching followed by disposal of the water, rather than direct consumption after stir-frying or stewing. It may be prudent to provide precautionary advice and monitor activity levels, as this mushroom continues to be foraged by casual as well as experienced mushroom hunters.