Preliminary results of detailed geochemical study of mercury at the ancient ore roasting site P{enk (Idrija area, Slovenia)

Abstract

P{enk is one out of 21 localities of ancient roasting sites in the woods surrounding Idrija and one of the largest localities of roasting vessels fragments. The most abundant pottery remains are found in the central western part of the area, which is about 60 m long and up to 50 m wide and is supposed to be the location of the roasting process itself. Detailed soil sampling was performed on 210 x 180 m big area. 156 soil (0-15 cm and 15-30 cm) and humus samples were collected from 73 sampling points. 3 soil profiles were sampled to determine vertical distribution of Hg in soil. The prevailing soil types are Cambisols with the typical A-B-C layers sequence. In general soils are rich in organic matter to the depth of 30-40 cm; deeper the clayey loam prevails. The determined Hg contents in soil and humus samples of the investigated area are in the range 1.6-8,600 mg/kg with the median of 62.5 mg/kg. At the area of supposed roasting site the Hg contents range between 20 and 8,600 mg/kg with the median of 580 mg/kg. Spatial distribution of mercury in humus and soils of the investigated area show the highest Hg concentrations at the supposed roasting site area where the largest quantity of pottery fragments were found and to the east of this area, at the narrow tract between the footpath on the north and the bed of La~na voda brook on the south. Extremely high Hg contents were found in profile P4 where it riches 37,020 mg/kg at the depth of 20-30 cm; in general Hg concentrations in all three studied profiles show a gradual decrease with depth. The soils of the investigated area are enriched with mercury to a high degree. Further investigations on Hg speciation are needed to determine the mobility and bioavailability of Hg in soil. Izvle~ekP{enk je ena izmed 21 lokacij nekdanjih žgalni{kih mest v gozdovih okrog Idrije in eno ve~jih nahajali{~ drobirja žgalni{kih posod. Najve~je koli~ine lon~enine najdemo na približno 60 m dolgem in do 50 m {irokem predelu v centralnem zahodnem delu obravnavanega obmo~ja, ki domnevno predstavlja ožje obmo~je žgalnice. Na raziskovanem ozemlju v velikosti 210 x 180 m je bilo na 73 vzor~nih lokacijah odvzetih 156 vzorcev tal (0-15 cm and 15-30 cm) in humusa. Za dolo~itev vertikalne razporeditve Hg v tleh so bili vzor~eni 3 talni profili. Prevladujo~i talni tip so kambi~na tla s tipi~nim profilom A-B-C. Tla so v splo{nem bogata z organsko snovjo do globine 30-40 cm, globlje pa prevladuje glinasta ilovica. Vsebnost živega srebra v obravnavanih vzor~nih medijih zna{a v povpre~ju 62,5 mg/kg in niha v razponu od 1,6 do 8.600 mg/kg. Na ožjem obmo~ju žgalnice se vrednosti gibljejo med 20 in 8.600 mg/kg, mediana zna{a 580 mg/kg. Prostorska razporeditev živega srebra v humusu in tleh kaže najvi{je vrednosti na domnevnem ožjem obmo~ju žgalnice in vzhodno od tega obmo~ja, na predelu med gozdno potjo na severu in strugo potoka La~na voda na vzhodu. Ekstremno visoke vsebnosti Hg so bile dolo~ene v profilu P4, kjer dosežejo na globini 20-30 cm vrednost 37.020 mg/kg; v splo{nem vsebnosti Hg v vse...

Mercury contents in the vertical profiles through alluvial sediments as a reflection of mining in Idrija (Slovenia)

“…4), which were active in the 16th and 17th century. These localities are highly contaminated, they surpass all described localities in Idrija, because former roasting processes led to considerable losses of Hg (Gosar and Čar, 2006;Teršič, 2010aTeršič, , 2010bTersič et al, 2008;Teršič and Gosar, 2009). Despite these hot spots being spatially limited, we can attribute the increased Hg content in all three profiles in the upper Idrijca Valley to the influence of historical small ore processing in the woods around Idrija.…”

“…The main disadvantage of past studies was the fact that all of them were focused on the study of the Hg contamination and its transformation downstream of main and dominant source of pollution -Idrija Hg mine and ore roasting plant. But known from the recent findings (Gosar and Čar, 2006;Teršič, 2010aTeršič, , 2010bTersič et al, 2008;Teršič and Gosar, 2009), many small-scale ore roasting places existed in 16th century, scattered across the hills around Idrija. The highly contaminated material from these historical roasting sites was thus eroded during the centuries and also significantly contributed to the Hg concentrations in the alluvial sediments.…”

“…The average value of Hg in the top 45 cm of soil at some of these roasting sites is 4000-5000 mg/kg, and around 100 mg/kg in the lower parts of the soil (Gosar and Čar, 2006;Teršič, 2010aTeršič, , 2010bTersič et al, 2008). The highest measured Hg concentration in soil at one specific locality named Pšenk was reported to be 1.6% (Teršič, 2010a(Teršič, , 2010bTeršič and Gosar, 2009). The bioavailability of Hg in the wider Idrija area has been demonstrated by Hines et al (2000) and Gosar (2008).…”

“…The production of Hg in Idrija started in 1492. For the first 150 years, the ore was roasted in earthen vessels at various sites in the woods around Idrija (Gosar and Čar, 2006;Kavčič, 2008;Tersič et al, 2008;Teršič and Gosar, 2009). Hg was released into the environment not only because of Hg evaporation during the roasting process, but also because of ore and end product transportation and incidental spills of Hg.…”

Environmental geochemistry studies in the area of Idrija mercury mine, Slovenia

“…The preliminary investigations of mercury contents in soils at old roasting site locations (Gosar and Č ar 2006;Teršič and Gosar 2009;Teršič et al 2008) revealed that mercury contents in soils at these sites are very high, surpassing all hitherto described localities at Idrija and surroundings. It was estimated that there are about 40 tons of mercury still present at these sites (Gosar and Č ar 2006).…”