Mercury Reservoir Research Articles

Quantifying soil accumulation of atmospheric mercury using fallout radionuclide chronometry

Soils are a principal global reservoir of mercury (Hg), a neurotoxic pollutant that is accumulating through anthropogenic emissions to the atmosphere and subsequent deposition to terrestrial ecosystems. The fate of Hg in global soils remains uncertain, however, particularly to what degree Hg is re-emitted back to the atmosphere as gaseous elemental mercury (GEM). Here we use fallout radionuclide (FRN) chronometry to directly measure Hg accumulation rates in soils. By comparing these rates with measured atmospheric fluxes in a mass balance approach, we show that representative Arctic, boreal, temperate, and tropical soils are quantitatively efficient at retaining anthropogenic Hg. Potential for significant GEM re-emission appears limited to a minority of coniferous soils, calling into question global models that assume strong re-emission of legacy Hg from soils. FRN chronometry poses a powerful tool to reconstruct terrestrial Hg accumulation across larger spatial scales than previously possible, while offering insights into the susceptibility of Hg mobilization from different soil environments.

Process of mercury accumulation in urban strip river artificial wetland ecosystems: a case study of Changchun, a typical industrial city in Northeast China.

Mercury (Hg), as a global pollutant, is persistent, migratory, insidious, highly biotoxic and highly enriched, and is widely distributed in the atmosphere, hydrosphere, biosphere and lithosphere. Wetland ecosystems, as active mercury reservoirs, have become the most important sources and sinks of heavy metal mercury. Distinguished from natural wetlands, artificial wetlands located in urban sections of rivers face problems such as diverse urban pollution sources and complex spatial and temporal changes. Therefore, in this study, five intermittently distributed artificial wetlands were selected from the upstream to the downstream of the Changchun section of the Yitong River, a tributary of the Songhua River basin in the old industrial base of Northeast China. The mercury levels in the water bodies, sediments and plants of the artificial wetlands were collected and tested in four quarters from April 2023 to analyse the spatial and temporal distribution characteristics of total mercury. The results showed that the mercury levels in the water bodies, sediments and plants of the five wetlands showed a fluctuating trend with the river flow direction and had certain spatial and temporal distribution characteristics. This phenomenon was attributed to the sinking of external mercury pollution sources. In general, the wetland ecosystems showed a decreasing trend in the total Hg output of the downstream watershed. This may be due to the retention of particulate matter by aquatic plants in artificial wetlands to regular salvage of dead aquatic plants. At the same time urbanization and industrialization affect mercury levels in aquatic environments, so the risk of residential exposure needs to be looked at.

Mercury mobilization in shrubland after a prescribed fire in NE Portugal: Insight on soil organic matter composition and different aggregate size

Soils constitute the major reservoir of mercury (Hg) in terrestrial ecosystems, whose stability may be threatened by wildfires. This research attempts to look at the effect of prescribed fire on the presence of Hg in a shrubland ecosystem from NE Portugal, delving into its relationship with soil aggregate size and the molecular composition of soil organic matter (SOM). During the prescribed fire, on average 347 mg Hg ha−1 were lost from the burnt aboveground biomass of shrubs and 263 mg Hg ha−1 from the combustion of the soil organic horizon. Overall, Hg concentration and pools in the mineral soil did not show significant changes due to burning, which highlights their role as long-term Hg reservoirs. The higher Hg concentrations found in smaller aggregates (<0.2 mm) compared to coarser ones (0.5–2 mm) are favored by the higher degree of organic matter decomposition (low C/N ratio), rather than by greater total organic C contents. The Hg-enriched finest fraction of soil (<0.2 mm) could be more prone to be mobilized by erosion, whose potential arrival to water bodies increases the environmental concern for the Hg present in fire-affected soils. The SOM quality (molecular composition) and the main organic families, analyzed by Fourier-transform infrared spectroscopy in combination with multivariate statistical analysis, significantly conditioned the retention/emission of Hg in the uppermost soil layers. Thus, before the fire, Hg was strongly linked to lipid and protein fractions, while Hg appeared to be linked to aromatic-like compounds in fire-affected SOM.

Mercury in soils of the conterminous United States: patterns and pools

Soils account for the largest global mercury reservoirs, but observations are sparse in many regions. The accumulation and turnover of mercury in soils determines whether they act as an atmospheric source or sink. Here, we present a spatial analysis of soil mercury from a large soil survey (three horizons, ∼4800 sites) across the conterminous United States conducted by the U.S. Geological Survey. Soil mercury pools were calculated for 11 layers, cumulatively representing the top 1 m of soil, and totaling 158 ± 2 Gg (±SD) of mercury (20.3 ± 0.2 mg m−2). Mercury areal density was greatest in mixed forest (27.3 ± 0.5 mg m−2), cropland (25.3 ± 0.3 mg m−2), and deciduous forest (25.6 ± 0.5 mg m−2) ecosystems and lowest in barren (13.5 ± 0.3 mg m−2) and shrubland (12.6 ± 0.2 mg m−2) ecosystems. Assessment of the provenance of soil mercury using bedrock titanium normalization suggests that 62%–95% of soil mercury is unexplained by parental sources.

Geochemical and Dietary Drivers of Mercury Bioaccumulation in Estuarine Benthic Invertebrates

Sediments represent the main reservoir of mercury (Hg) in aquatic environments and may act as a source of Hg to aquatic food webs. Yet, accumulation routes of Hg from the sediment to benthic organisms are poorly constrained. We studied the bioaccumulation of inorganic and methylmercury (HgII and MeHg, respectively) from different geochemical pools of Hg into four groups of benthic invertebrates (amphipods, polychaetes, chironomids, and bivalves). The study was conducted using mesocosm experiments entailing the use of multiple isotopically enriched Hg tracers and simulation of estuarine systems with brackish water and sediment. We applied different loading regimes of nutrients and terrestrial organic matter and showed that the vertical localization and the chemical speciation of HgII and MeHg in the sediment, in combination with the diet composition of the invertebrates, consistently controlled the bioaccumulation of HgII and MeHg into the benthic organisms. Our results suggest a direct link between the concentration of MeHg in the pelagic planktonic food web and the concentration of MeHg in benthic amphipods and, to some extent, in bivalves. In contrast, the quantity of MeHg in benthic chironomids and polychaetes seems to be driven by MeHg accumulation via the benthic food web. Accounting for these geochemical and dietary drivers of Hg bioaccumulation in benthic invertebrates will be important to understand and predict Hg transfer between the benthic and the pelagic food web, under current and future environmental scenarios.

Uranium tetrafluoride production at pilot scale using a mercury electrode cell

This work shows the technical feasibility to obtain uranium tetrafluoride through an electrochemical mercury cell. This technique represents a custom scaling-up methodology from our previous studies to obtain UF4 using the dropping mercury electrode cell. The UF4 products were obtained from natural UF6 gas, which was hydrolyzed to obtain a 50 g/L UO2F2 solution. The electrolysis cell was made using a mercury reservoir, to reach UF4 production rates of 1 Kg UF4/day. This custom design allowed a stable UF4 production thanks to the mercury cathode, which do not permit the accumulation of solid products in its surface. The cell was tested using current densities from 5.000 to 17.500 A/m2 and temperatures from 25 to 65 °C. The maximum current efficiency achieved under these conditions was 80%. The UF4 powders possessed spherical morphology, with diameters between 20 and 80 μm. Compared to the SnCl2 precipitation, this process did not allow preferential growth of the precipitates. This improved the compaction of the UF4 – Mg powders mixtures, with densities between 3.0 and 3.5 g/cm3. The purity of the UF4 products was over 98%.

Planular-vertical distribution and pollution characteristics of cropland soil Hg and the estimated soil–air exchange fluxes of gaseous Hg over croplands in northern China

As an important reservoir of mercury (Hg), cropland play an important role in the Hg cycle, but it was poorly understood in northern China. The major objectives of this study are to ascertain the distribution characteristics of soil Hg and then assess its pollution level and potential risk, and further evaluate the role of cropland in northern China in the global soil–air exchange of Hg based on the simulation experiments and regional survey. The average Hg concentration in surface soils of the 30 sites in northern China was 116.1 ± 135.8 ng g−1, which was significantly higher than background values. The surface soils show a significant spatial heterogeneity in Hg concentration, and the Hg levels near provincial capitals were higher than those at corresponding prefecture-level cities, revealing that the soil Hg levels were closely associated with the local industrial and economic development. Profile data shows that topsoil Hg concentration was significantly higher than those in deeper layers at most of sites, indicating the more serious pollution situation in recent years. Generally, the higher the surface soil Hg concentration, the more obvious this top-bottom decreasing trend. The planular-vertical distribution patterns of TOM share similar trends as those of soil Hg concentration, indicating Hg concentration was closely associated with TOM content. Statistical results show that the mean CF, Eri, and Igeo values were 4.0 ± 5.0, 161 ± 198, 0.76 ± 1.34, respectively, and more than two thirds of sampling sites were moderately and considerably polluted. The mean annual accumulative flux of Hg in the northern China was 20.9 ± 43.8 μg m−2 yr−1, and the total net emission fluxes of Hg from the croplands in six provinces were 8.37 ton yr−1. This indicates that although the cropland occasionally acts as a sink, it represents an important natural source of atmospheric Hg as a whole.

Stable Mercury Isotope Transition during Postdepositional Decomposition of Biomass in a Forest Ecosystem over Five Centuries.

Organic soil is an important transient reservoir of mercury (Hg) in terrestrial ecosystems, but the fate of deposited Hg in organic forest soil is poorly understood. To understand the dynamic changes of deposited Hg on forest floor, the composition of stable Hg and carbon (C) isotopes in decomposing litters and organic soil layer was measured to construct the 500 year history of postdepositional Hg transformation in a subtropical evergreen broad-leaf forest in Southwest China. Using the observational data and a multiprocess isotope model, the contributions of microbial reduction, photoreduction, and dark reduction mediated by organic matter to the isotopic transition were estimated. Microbial reduction and photoreduction play a dominant role in the initial litter decomposition during first 2 years. Dark redox reactions mediated by organic matter become the predominant process in the subsequent 420 years. After that, the values of Hg mass dependent fractionation (MDF), mass independent fractionation (MIF), and Δ199Hg/Δ201Hg ratio do not change significantly, indicating sequestration and immobilization of Hg in soil. The linear correlations between the isotopic signatures of Hg and C suggest that postdepositional transformation of Hg is closely linked to the fate of natural organic matter (NOM). Our findings are consistent with the abiotic dark reduction driven by nuclear volume effect reported in boreal and tropical forests. We recommend that the dark reduction process be incorporated in future model assessment of the global Hg biogeochemical cycle.

Occurrence and risk assessment of total mercury and methylmercury in surface seawater and sediments from the Jiaozhou Bay, Yellow Sea

The Jiaozhou Bay is a semi-enclosed bay located in the middle of the Yellow Sea. Effluents from wastewater treatment plants have been carried into the bay, which has significantly increased the deposition of mercury. The spatial distributions of total mercury (THg) and methylmercury (MeHg) in dissolved state, in suspended matters of seawater and surface sediments at 26 locations inside the Jiaozhou Bay and five surrounding rivers in April 2018 were examined. The contents of THg and MeHg found along the eastern coast were higher than those found along the western coast, which indicated the impact of human activities (river input) on the Jiaozhou Bay. The partition coefficient (LogKd) was used to express the distribution relationships of THg and MeHg in suspended matters and dissolved state, and it was concluded that suspended matter was the main reservoir of mercury in Jiaozhou Bay seawater. The correlations between contents and physicochemical properties of seawater showed that THg and MeHg concentrations in seawater decreased with increasing salinity and pH. The effects of the mean grain diameter (MGD) and sediment organic matter (SOM) on the THg and MeHg in surface sediments were also discussed. Principal component analysis (PCA) was used to obtain the factors determining the methylation proportion in the surface sediments, indicating that the combination of human activities and natural processes affected the degree of methylation in the sediments. The spatial distribution of THg, MeHg and MeHg% was suggested to be disturbed by the interaction of natural processes and human activities (river input) by the correlation analysis of the corresponding pollutant concentrations among seawater and. Although the concentrations of THg and MeHg in seawater and sediments of the Jiaozhou Bay did not exceed the Chinese regulatory standards, the pollution levels of THg and MeHg were comparable to those in other bays in the world.

Temperature sensitivity of gaseous elemental mercury in the active layer of the Qinghai-Tibet Plateau permafrost

Soils represent the single largest mercury (Hg) reservoir in the global environment, indicating that a tiny change of Hg behavior in soil ecosystem could greatly affect the global Hg cycle. Climate warming is strongly altering the structure and functions of permafrost and then would influence the Hg cycle in permafrost soils. However, Hg biogeochemistry in climate-sensitive permafrost is poorly investigated. Here we report a data set of soil Hg (0) concentrations in four different depths of the active layer in the Qinghai-Tibet Plateau permafrost. We find that soil Hg (0) concentrations exhibited a strongly positive and exponential relationship with temperature and showed different temperature sensitivity under the frozen and unfrozen condition. We conservatively estimate that temperature increases following latest temperature scenarios of the IPCC could result in up to a 54.9% increase in Hg (0) concentrations in surface permafrost soils by 2100. Combining the simultaneous measurement of air–soil Hg (0) exchange, we find that enhanced Hg (0) concentrations in upper soils could favor Hg (0) emissions from surface soil. Our findings indicate that Hg (0) emission could be stimulated by permafrost thawing in a warmer world.

Saint Ioannis Lampadistis, the first possible case of blindness due to organic mercury poisoning in history.

Saint Ioannis Lampadistis is a Cypriot saint of the Greek Orthodox Church, widely venerated in his island of origin. He lived during the 11th century and was blinded by ingesting contaminated fish in the mountainous area of Galata, withdrew from civil life when he was 18, and died at the age of 22. The reason for his blindness remains unknown, though it is widely attributed to an unknown poison related to the copper mines of the region. As fish is the end reservoir of organic mercury, it is quite possible that his blindness was the result of heavy metal toxicity. Organic mercury is associated with CNS atrophy and hypoplasia, and blindness is a frequent presenting symptom. While not much is known about the saint's clinical symptoms (as his ecclestiastical biography focuses on his example and miracles), organic mercury poisoning could explain his sudden loss of vision, thus possibly making him the first-recorded case of organic mercury poisoning in history.

The impacts of organic matter on the distribution and methylation of mercury in a hydroelectric reservoir in Wujiang River, Southwest China.

To understand the impacts of organic matter on the geochemical processing of Hg in a hydroelectric reservoir, spatial and seasonal distributions of total mercury (THg) and methylmercury (MeHg) in both solid and liquid phases of sediment cores were investigated in the Wujiangdu Reservoir in Guizhou Province, China. Four sampling sites with different intensities of cage aquaculture activities were chosen and were evenly distributed from upstream to downstream of the Wujiangdu Reservoir. Elevated MeHg concentrations and the high percentage of MeHg in solid and liquid phases of the surface sediment demonstrated that the active Hg methylation process occurred downstream of the Wujiangdu Reservoir. In contrast, the absence of obvious peaks for MeHg in sediment from the upper reaches of the Wujiangdu Reservoir, consistent with low levels of organic matter, suggested that production of MeHg was limited. In sediment with high organic matter content, reduction occurred closer to the sediment surface, resulting in maximum MeHg concentration in these layers. The correlation between MeHg and organic carbon implied that organic matter content in the sediment originating from cage aquaculture activities can help to predict MeHg production rates in reservoirs, which could be used to assess possible MeHg contamination in a reservoir ecosystem.

Deforestation and cultivation mobilize mercury from topsoil

Terrestrial biomass and soils are a primary global reservoir of mercury (Hg) derived from natural and anthropogenic sources; however, relatively little is known about the fate and stability of Hg in the surface soil reservoir and its susceptibility to change as a result of deforestation and cultivation. In southwest Ohio, we measured Hg concentrations in soils of deciduous old- and new-growth forests, as well as fallow grassland and agricultural soils that had once been forested to examine how, over decadal to century time scales, man-made deforestation and cultivation influence Hg mobility from temperate surface soils. Mercury concentrations in surficial soils were significantly greater in the old-growth than new-growth forest, and both forest soils had greater Hg concentrations than cultivated and fallow fields. Differences in Hg:lead ratios between old-growth forest and agricultural topsoils suggest that about half of the Hg lost from deforested and cultivated Ohio soils may have been volatilized and the other half eroded. The estimated mobilization potential of Hg as a result of deforestation was 4.1mgm−2, which was proportional to mobilization potentials measured at multiple locations in the Amazon relative to concentrations in forested surface soils. Based on this relationship and an estimate of the global average of Hg concentrations in forested soils, we approximate that about 550Mmol of Hg has been mobilized globally from soil as a result of deforestation during the past two centuries. This estimate is comparable to, if not greater than, the amount of anthropogenic Hg hypothesized by others to have been sequestered by the soil reservoir since Industrialization. Our results suggest that deforestation and soil cultivation are significant anthropogenic processes that exacerbate Hg mobilization from soil and its cycling in the environment.

Accumulation of mercury in Typha domingensis under field conditions

Typha species is a common wetland plant used in the treatment of urban and industrial effluents. But, despite their widespread implementation, there are not many studies based on the behaviour of this plant growing in an areas affected by mercury. The present work investigates the ability of Typha domingensis to accumulate mercury under field conditions. The study area was along the Valdeazogues river which flows through the Almadén mining district (Ciudad Real, Spain) that is considered the largest mercury reservoir in the world. The mercury concentration in different plant fractions was measured as well as the available and total concentration in the bottom sediments.The results showed that the highest mercury concentrations were found in the belowground organs. T. domingensis had a high efficiency to accumulate mercury in their organs although available metal concentrations in the environment did not exceed 0.16mgkg−1. Bioaccumulation factors (BAF) ranged between 121 and 3168 in roots. Furthermore, significant correlations were found between mercury concentration in all plant organs and Hg in sediments (both total and available). These results demonstrated that T. domingensis could be used as a biomonitor as well as in phytoextraction technology in areas affected by mercury.

Evidence of air-snow mercury exchange recorded in the snowpack at Dome Fuji, Antarctica

Measuring the mercury content in shallow Antarctic snow pits is useful for understanding the mercury dynamics of the Antarctic Plateau and the global mercury cycle and for interpreting ice core data. We determined the total mercury concentration (HgT) in snow samples successively collected at 5 cm intervals from two 4m deep snow pits at Dome Fuji. The measured mercury concentration varied between 0.32 (the detection limit) and 2.93 pg g−1 (n = 160) with depth and was lower than that of summertime surface snow that was sampled simultaneously. This finding is consistent with previous observations that a bidirectional exchange of mercury between the snowpack and the atmosphere led to an increase in HgT in the surface snow during the summer. However, the contribution of the air-snow Hg exchange to the net Hg sequestration was offset by the intense re-emission of deposited mercury over the past ∼50 years. Our results demonstrate that the Antarctic Plateau snowpack is a temporary reservoir of mercury rather than a permanent sink.

Future trends in environmental mercury concentrations: implications for prevention strategies

In their new paper, Bellanger and coauthors show substantial economic impacts to the EU from neurocognitive impairment associated with methylmercury (MeHg) exposures. The main source of MeHg exposure is seafood consumption, including many marine species harvested from the global oceans. Fish, birds and other wildlife are also susceptible to the impacts of MeHg and already exceed toxicological thresholds in vulnerable regions like the Arctic. Most future emissions scenarios project a growth or stabilization of anthropogenic mercury releases relative to present-day levels. At these emissions levels, inputs of mercury to ecosystems are expected to increase substantially in the future, in part due to growth in the legacy reservoirs of mercury in oceanic and terrestrial ecosystems. Seawater mercury concentration trajectories in areas such as the North Pacific Ocean that supply large quantities of marine fish to the global seafood market are projected to increase by more than 50% by 2050. Fish mercury levels and subsequent human and biological exposures are likely to also increase because production of MeHg in ocean ecosystems is driven by the supply of available inorganic mercury, among other factors. Analyses that only consider changes in primary anthropogenic emissions are likely to underestimate the severity of future deposition and concentration increases associated with growth in mercury reservoirs in the land and ocean. We therefore recommend that future policy analyses consider the fully coupled interactions among short and long-lived reservoirs of mercury in the atmosphere, ocean, and terrestrial ecosystems. Aggressive anthropogenic emission reductions are needed to reduce MeHg exposures and associated health impacts on humans and wildlife and protect the integrity of one of the last wild-food sources globally. In the near-term, public health advice on safe fish consumption choices such as smaller species, younger fish, and harvests from relatively unpolluted ecosystems is needed to minimize exposure risks.

Mercury and Other Trace Elements in Glacial Meltwater at Grand Teton National Park, Wyoming

Glaciers are a reservoir of mercury (Hg) and other trace elements that have accumulated in the ice during the industrial era. As glaciers continue to melt at an alarming rate, these potentially toxic metals are released to the environment. In order to evaluate the impact of glacier melt on water quality in high elevation catchments in Grand Teton National Park, we sampled transects along the Teton and Middle Teton glaciers and proglacial streams during early-July and mid-August 2013. The glaciers were snow-covered during July, and thus water samples were primarily melt of snowpack from the previous winter. The glacier ice was exposed during August, and thus samples likely represented true glacier melt. These contrasting sample sets allowed for a determination of the impact of snowmelt versus glacier melt on water chemistry. Ten samples were collected during July and August along the Glacier Gulch transect: four of surface drainage on the Middle Teton glacier, three near the terminal moraine, and three downstream of the glacier. Thirteen samples were collected during July and August along the Garnet Canyon transect: one at the Lower Saddle of the Grand Teton, four of surface drainage on the Middle Teton glacier, two near the terminal moraine, two at the moraine of Teepe Glacier, and four samples downstream of the glaciers. All water samples were analyzed for total Hg, a suite of trace elements (including U, Sr, and Mn), and stable water isotopes (δ2H and δ18O). Analyses for methyl Hg, solutes, and tritium (3H) are still underway. Preliminary results indicate that snowmelt and glacier melt was a significant source of total Hg, but additional work is needed to determine the extent of Hg methylation in the proglacial streams. Other trace elements were found in low concentrations in the melt water, but increased substantially downstream of the glaciers due to water-rock interactions.

Ataxia and cranial neuropathies from subcutaneously injected elemental mercury

Context. Although neurological toxicity from elemental mercury vapor and organic mercury exposure has been commonly reported in the literature, it is rarely reported from soft tissue injection of elemental mercury. We present a case of neurological dysfunction from subcutaneous injection of elemental mercury. Case details. A 35‐year‐old Latin American man subacutely developed gait ataxia, diplopia, and vomiting 1 year after subcutaneous injection of elemental mercury, a practice common in Afro‐Caribbean and Latin‐American cultures. Physical examination showed an indurated plaque on his right shoulder at the injection site, left third nerve and bilateral sixth nerve palsies, nystagmus, dysarthria, and gait and limb ataxia. The patient’s serum and 24‐h urine mercury levels were significantly elevated; he underwent excision of the mercury reservoir and chelation with dimercaptosuccinic acid but experienced only mild improvement after 1 year. Discussion. Neurological sequelae from elemental mercury, specifically cognitive dysfunction, tremor, cortical myoclonus, and peripheral neuropathy, have been reported but cranial neuropathies, ataxia, cerebrospinal fluid pleocytosis, and the presence of anti‐Purkinje cell type‐Tr antibody have not. Treatment involves removal of any existing mercury reservoir and chelation; however, improvement in neurological dysfunction after treatment has rarely been reported in the literature.

The effect of contaminants on the mercury consumption of fluorescent lamps

In order to study the effect of water adsorbed on the alumina coating of fluorescent lamps 35 W tubes were prepared by so setting the manufacturing process as not to fully remove contaminants. The light intensity has been measured along the tubes, showing a fast drop after the initial illumination at switching on. The minimum intensity was followed by a recovery of the light output, the brightening extending gradually from the liquid mercury reservoir of the tube. To explain the observations the reaction between mercury ions and water and its decomposition products (OH and H radicals) were considered, which decreases the free mercury concentration and thus the light output. Density functional calculations indeed indicate a strong binding between these species.

Revision and necessary correction of the long-term temperature series of Hohenpeissenberg, 1781–2006

Having been in use at Hohenpeissenberg from 1781–1841, the Palatina thermometer was found to suffer from a positive bias of 0.5°R (or 0.63°C) as discovered by Lamont following a re-calibration made in 1842. The main reason was due to the composition of the glass used during the early instrumental period. Glass of this period tended to contract over many years due to thermal aftereffects, resulting in a gradual rise of the freezing point position in consequence of the shrinking bulb forming the mercury reservoir. While the problem of the gradually rising zero point was recognised relatively early, the reason was attributed to wrong causes. Around 1880, scientists recognised that the chemical composition of glass might be responsible for the drift of the zero point. New glass types were developed which were free from such effects. Although these facts became known, no correction was applied to the Hohenpeissenberg temperature series when in 1981, the complete 200-year series was published. Most probably this bias is also relevant for other stations, at least those of the network of the Societas Meteorologica Palatina that were supplied with thermometers manufactured in Mannheim. Another problem originates from the different observing times for the period 1879–1900, which were set to 0800, 1400 and 2000 hours instead of 0700, 1400 and 2100 hours before and afterwards. In addition, a new formula to calculate the daily mean was established resulting in the temperature being too low by 0.5°C in that period. The overall trend changes after application of the two necessary corrections. There remain two biases that cannot be quantified without a major detailed study being made: (1) At the start of the observations, the window of the observation room was always kept “open during dry weather”. It is not known how long this practice was remained in use. (2) Lamont also employed an easily melting glass to construct his thermometers which in use between 1841 and 1878. An analysis of the glass composition seems to be necessary to find out whether it also suffered from a rising freezing point. Lamont replaced the Hohenpeissenberg thermometer in 1842 by a new instrument produced in his own workshop. One still existing Lamont thermometer, but not that one of Hohenpeissenberg, was re-calibrated and the zero point found to have lowered by −1.4°C. Since the opposite drift had been expected and the original Lamont-type Hohenpeissenberg thermometer is no longer available, no correction is justified for the period in which this thermometer was in use.