First lead isotopic data for cinnabar in the Almadén district (Spain): implications for the genesis of the mercury deposits

The Almadén district constitutes the largest and probably the most intriguing mercury concentration in the world. Two types of mineralization are recognized: 1) stratabound, of Lower Silurian age, well represented by the large Almadén deposit; and 2) fully discordant mercury deposits of minor importance in terms of size, and exemplified by the deposit of Las Cuevas. The latter ones can be found at different positions along the Almadén stratigraphic column. Both types of deposits are always associated with the so-called frailesca rocks (diatremes of alkali basaltic composition). This paper reports the first lead isotope compositions of cinnabar in the district. Whole samples and stepwise leaching cinnabar aliquots display relatively homogeneous isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 18.112–18.460; ²⁰⁷Pb/²⁰⁴Pb = 15.635–15.705; ²⁰⁸Pb/²⁰⁴Pb = 38.531–38.826). Taken together with Jébrak et al.s (2002) pyrite lead isotope results, the new cinnabar isotopic data define a steep array trend on the ²⁰⁷Pb/²⁰⁴Pb– ²⁰⁶Pb/²⁰⁴Pb diagram, indicating a mixed contribution of lead and probably mercury from different sedimentary sources in the Almadén basin. The Almadén Hg deposits are related to a contemporaneous mafic magmatism that might have provided part of the mercury. Hydrothermal leaching of organic matter from sedimentary rocks and formation of Hg organic complexes enhanced metal solubility, promoting transport from and within the volcanic units.Editorial handling: M. Chiaradia     

Sedimentärer Pyrit aus der Zinnober-Lagerstätte Almadén

Zusammenfassung Durch Pyrit hervorgehobene sedimentäre Strukturen treten in enger räumlicher Verbindung mit der Zinnobervererzung in Almadén auf. Dieser Pyrit wurde mikroskopisch und makroskopisch untersucht. Seine Ausbildung ist im allgemeinen idiomorph und weist deutlich auf eine Auskristallisierung aus Gelen hin, die in unverfestigten Sedimenten stattgefunden hat. Da ein Teil des Zinnobers in Pyrit eingeschlossen vorkommt, muß seine Zufuhr vor der Verfestigung der Sedimente erfolgt sein.

---

Sedimentary structures, emphasized by pyrite, are closely connected with the cinnabar deposits at Almadén. This pyrite was studied macroscopically and microscopically. Its habit is usually idiomorphic and shows clearly that it crystallized from colloids in unconsolidated sediments. Part of the cinnabar occurs as inclusions in the pyrite and therefore must have been brought in before lithification of the sediments.

     

Distribution and speciation of mercury in soil in the area of an ancient mercury ore roasting site,Frbejžene trate (Idrija area,Slovenia)

In the initial period of mining activities in the Idrija basin (the16^th and the first half of the17^th centuries), Hg ore processing was performed at various small-scale roasting sites in the woods surrounding Idrija, by roasting ore in earthen vessels. The recovery rate of this method was very low; about half of Hg was lost, causing soil contamination and considerable amounts of waste material that could potentially leach Hg into the surrounding environment. The main aims of present geochemical study were to determine the contents, vertical distribution and speciation of Hg in soils at the roasting site at Frbej?ene trate in order to verify the extreme pollution of ancient Hg ore roasting sites in the Idrija area and to establish their significance in the wider spatial contamination of soils and aquatic systems. Soil sampling was performed at the area of the former roasting site. The organic matter-rich surface soil layer (SOM) and underlying mineral soil were sampled at 63 sampling locations. Mercury speciation was performed using Hg thermo-desorption-AAS to distinguish cinnabar from potentially bioavailable forms. The results indicate extremely high Hg concentrations with a maximum of 37,000 mg/kg in SOM and 19,900 mg/kg in mineral soil. The established Hg median in soil was 370 mg/kg and in SOM 96.3 mg/kg. Spatial distributions of Hg in SOM and soil showed very high Hg contents in the central area and decreased rapidly with distance. The results of Hg thermo-desorption measurements indicated the presence of cinnabar (HgS) and Hg bound to organic or mineral soil matter. A significant portion (35–40%) of Hg in the investigated soil and SOM samples was comprised of non-cinnabar compounds, which are potentially bioavailable. It has been shown that soils contain high amounts of potentially transformable non-cinnabar Hg, which is available for surface leaching and runoff into the surrounding environment. Therefore, contaminated soils and roasted residues at the studied area are important for persistent Hg release into the aquatic ecosystem.     

北京市土壤Hg污染的区域生态地球化学评价

城市土壤Hg异常/污染是中国普遍存在的重大生态环境问题。文章对北京市近1000km2范围内的地表土壤、壤中气、大气干湿沉降、大气颗粒物、大气中的Hg含量水平和空间分布模式进行了系统研究,查明北京地表土壤Hg平均含量为0.41mg/kg,大气干湿沉降物中的Hg平均含量为0.194mg/kg,壤中气Hg的平均含量为559.65ng/m3,大气颗粒物PM10和PM2.5中的Hg含量分别为0.59和0.67ng/m3,大气中的Hg平均含量为3.13ng/m3。北京市自2000年起实现了由燃煤转变为燃气的减排措施,导致干湿沉降物中的Hg沉降通量显著减少,2006年大气干湿沉降物中Hg的沉降通量1.837mg·m-2·a-1,北京市城区(近1000km2)Hg全年沉降为1837kg,空气中总Hg浓度由1998年的8.3~24.7ng/m3下降到2006年的3.13ng/m3,大气颗粒物中Hg含量由2003年的1.18ng/m3下降到2006年的0.59ng/m3(PM10)和0.67ng/m3(PM2.5),表明北京市煤改气减排措施的实施显著改善了大气环境质量。通过对土壤中Hg的存在形式研究,发现土壤中有硫化物(辰砂)及各种Hg盐(HgCl2)的含Hg矿物,Hg也可以各种吸附方式或壤中气方式存在。研究证实北京壤中气Hg与大气Hg存在显著的相关性(n=131,R=0.267,p<0.01),表明壤中气Hg是大气Hg的重要来源之一。利用2005年地表土壤总Hg与Hg释放速率的线性方程估算,土壤Hg平均释放速率为102.42ng·m-2·h-1,2005年土壤释放进大气的Hg通量为936.70kg。在查明土壤中存在大量辰砂矿物的同时,还分布有大量具有高温熔融特征的金属微球粒和玻璃质微球粒,证明燃煤和冶金烟尘是地表土壤Hg的主要来源。土壤中Hg、S、pH和辰砂颗粒浓度在空间上的高度耦合性表明,碱性条件下,土壤中高含量的S和Hg是辰砂形成的重要原因。按国家土壤环境质量标准,北京市I级土壤Hg环境质量的面积为176km2,Ⅱ级为808km2,Ⅲ级为24km2,超Ⅲ为36km2。Ⅲ级、超Ⅲ级主要分布在二环路以内的中心城区。城南(长安街为界)大气Hg环境质量明显优于城北,在北四、北五环之间的部分地区,大气颗粒Hg的环境质量为Ⅲ级或超Ⅲ级。在地表土壤Hg含量较高的中心城区,居民每天因呼吸摄入的Hg高达364ng,对人体健康构成潜在风险。根据我国"十一五"规划中每年实现10%节能减排的目标,对北京市未来50年土壤Hg含量的时空演变趋势预测,预测2050年北京因干湿沉降带来的Hg输入量为16.03kg,地表土壤释放Hg的输出量为37.36kg,明显大于Hg的输入通量,土壤Hg的环境质量将得到根本改善。预测到2040年Ⅲ级土壤Hg环境质量的区域将完全消失,到2060年以Ⅰ级土壤为主。     

Tectonic deposition of mercury in the Almadén district,Las Cuevas deposit,Spain

The Las Cuevas mercury deposit is located in the northern part of the Almadén district, Ciudad Real, Spain. It displays characteristic epigenetic features. A reinterpretation of the geological context of the deposit and a detailed structural analysis indicate that the host rocks at Las Cuevas belong to the same stratigraphic units that host the old Almadén mine, but that they experienced a different tectonic evolution. Two types of ore are distinguished at Las Cuevas: (1) hydraulic breccias in a black quartzite, identical to the San Francisco horizon of the Almadén mine. This ore has been interpreted as syngenetic and is associated with an alkaline explosive volcanic event; and (2) a stockwork composed of horizontal subcritical tension cracks which developed along the contact between black shales and volcanic rocks in the hinge of a drag fold, and which is associated with advanced argillic alteration. Mobilization of mercury from type 1 to type 2 ore was related to a local inversion of the stress field associated with an increase of permeability by self-sealing, which probably occurred during uplift. Las Cuevas is representative of a whole class of mercury deposits hosted within basement rocks.     

Mercury speciation in tailings of the Idrija mercury mine

Five hundred years of mercury (Hg) mining activity in Idrija, Slovenia caused widespread Hg contamination. Besides Hg emissions from the ore smelter, tailings have been found to be the major source of river sediment contamination. In the present study, solid phase binding forms and the aqueous mobility of Hg have been investigated in tailings of the Idrija Hg mine by means of a pyrolysis technique and aqueous Hg speciation. Results show that Hg binding forms differ with the age of the tailings due to the processing of different ores with different roasting techniques. In older tailings, the predominant Hg species is cinnabar (HgS), due to incomplete roasting, whereas in tailings of the 20th century the amount of cinnabar in the material decreased due to a higher efficiency of the roasting process and the increasing use of ores bearing native Hg. In younger tailings, metallic Hg (Hg⁰) sorbed to mineral matrix components such as dolomite and Fe-oxyhydroxides became the predominant Hg binding form in addition to unbound Hg⁰ and traces of HgO. Leaching tests show that in younger tailings high amounts of soluble Hg exist in reactive form. In older tailings most of the soluble Hg occurs bound to soluble complexes. It might be assumed that in the long term, matrix-bound Hg⁰ could be bound to humic acids derived from soils covering the tailings. This means that, despite the lower total Hg concentrations found in the younger tailings, the long-term risk potential of its mobile matrix-bound Hg⁰ is higher than that of older tailings bearing mostly immobile cinnabar.     

Environmental impact of ancient small-scale mercury ore processing at Pšenk on soil (Idrija area, Slovenia)

The Idrija mine was the second largest Hg mine in the world surpassed only by the Almaden mine in Spain. It has been estimated that almost 145,000 tons of Hg was produced during operation (1490-1995) of the mine. In the first decade of Hg mining in Idrija the ore was roasted in piles; after that it was roasted for 150 years, until 1652, in earthen vessels at various sites in the woods around Idrija. Pšenk is one out of 21 localities of ancient roasting sites established on the hills surrounding Idrija and one of the largest localities of roasting vessel fragments. The unique way of roasting very rich Hg ore at this site has resulted in soil contamination and considerable amounts of waste material that potentially leach Hg into the surrounding environment. The main aim of this study was to determine the distribution and the forms of Hg in contaminated soils in order to evaluate potential environmental risk. Detailed soil sampling was performed on 37,800 m² area to establish the extent of Hg pollution and to investigate Hg transformations and transport characteristics through the 400 a-long period. A total of 156 soil (0-15 cm and 15-30 cm) and SOM (soil organic matter) samples were collected from 73 sampling points. Three soil profiles were sampled to determine vertical distribution of Hg. The main Hg phases were determined by the Hg-thermo-desorption technique. The measured Hg contents in soil samples in the study area vary from 5.5 to almost 9000 mg/kg with a median of 200 mg/kg. In SOM, Hg contents range from 1.4 to 4200 mg/kg with a median of 20 mg/kg. Extremely high Hg contents were found in soil profiles where the metal reaches 37,020 mg/kg. In general, Hg concentrations in all three profiles show a gradual decrease with depth with the minimum values between 140 mg/kg and 1080 mg/kg. The Hg-thermo-desorption curves indicate the presence of Hg in the form of cinnabar and that of Hg bound to organic or mineral soil matter. The distribution of Hg species in soil and SOM samples show almost equal distribution of cinnabar and non-cinnabar Hg compounds. The non-cinnabar fraction shows a little increase with depth, but cinnabar represents a high portion of total Hg (about 40%). Large amounts of potentially mobile and transformable non-cinnabar Hg compounds exist at the roasting site, which are potentially bioavailable.     

Mercury contamination in Marano Lagoon (Northern Adriatic sea,Italy): Source identification by analyses of Hg phases

Total Hg concentrations and Hg speciation were determined in bottom sediments of Marano lagoon to investigate the consequences of Hg phases on fish farms and shellfish cultivation areas. Mercury phases were separated into cinnabar (HgS) and non-cinnabar compounds, via a thermo-desorption technique, in surface and core sediments; both of which had been contaminated by industrial wastes and mining activity residues. The former are due to an industrial complex, which has been producing cellulose, chlor-alkali and textile artificial fibres since 1940. Processing and seepage wastewaters, which were historically discharged into the Aussa-Corno river system and therefore into the lagoon, have been significantly reduced since 1984 due to the construction of wastewater treatment facilities. The second source is the Isonzo River, which has been the largest contributor of Hg into the northern Adriatic Sea since the 16th century due to Hg mining at the Idrija mine (western Slovenia). Red cinnabar (HgS) derived from the mining area is mostly stable and insoluble under current environmental conditions. In contrast, organically bound Hg, such as Hg bound to humic acids, has the potential to be transformed into bioavailable Hg compounds (for example, methylmercury). The presence of the two Hg forms permitted each Hg source to be quantified. It also allowed the areas with the highest risk of Hg contamination from Hg-rich sediment to be identified; thus potentially avoiding the transfer of Hg from the sediment into the water column and eventually into living biota. The results show that Hg Enrichment Factors in bottom sediments exceed values of 10 and cinnabar dominates the central sector near the main tidal channel where tidal flux is more effective. Non-cinnabar compounds were found to be enriched in fine grained material and organic matter. In fact, up to 98% of total Hg at the Aussa-Corno river mouth and in the inner margin of the basin occurred in an organic form. This evidence, combined with the high contents of total Hg (4.1–6.6 μg g⁻¹ and EF > 10) measured in surface sediments, suggest that Hg in Marano lagoon is involved in biogeochemical transformations (e.g., methylation).     

Mercury speciation and mobilization in contaminated soils of the Valle del Azogue Hg mine (SE,Spain)

Hg mobilization from contaminated soils and mine wastes was the source of environmental contamination in the Valle del Azogue mining area. We researched solid-phase speciation and aqueous mobility of Hg through Scanning electron microscopy-energy dispersive X-ray spectroscopy and electron probe microanalysis analysis, solid-phase-Hg-thermo-desorption (SPTD) and laboratory column experiments. We found that in contaminated soils and mine wastes, the predominant Hg species was cinnabar (HgS), mainly formed from the weathering of Hg-rich pyrite, and metallic Hg (0) in the matrix, whereas in calcines and tailings the dominant species was metallic Hg (0). The mobilization of Hg in the aqueous phase seems to have originated from the dissolution of elemental Hg (0) present in soils and wastes, reaching concentrations of up to 67 μg l⁻¹, and showing a higher long-term environmental potential risk, in addition to atmospheric emissions.     

Discovery of Cinnabar in Soils in Hg Anomalous Zones in City and Town Areas and Their Surroundings and Its Significance

As a result of systematic study on heavy minerals in soils at city and town areas and their surroundings,cinnabar was discovered for the first time in areas of Hg anomalies in China, and it was found that the distribution of cinnabar was basically coincident in scope with that of Hg anomalies, showing that Hg anomalies were‘closely related to cinnabar. This finding provides a theoretical basis for a verification of Hg anomalies in soils in city and town areas and their surroundings, as well as evaluation of its ecological effects, and is significant to revealing the occurrence modes and origin of Hg in soils.     

中国汞的地球化学空间分布特征

20世纪80年代以来中国积累了岩石、土壤和水系沉积物中的大量可靠的汞分析数据和图件,为分析汞的地球化学空间分布特征提供了依据.从空间分布上看,从中国北部到南部,从西部到东部,土壤和水系沉积物中汞的含量背景值逐渐增高,汞在以干旱荒漠区、半干旱荒漠区、黄土地区和高寒山区为主的西部和北部呈低背景,在东部的森林沼泽区和半湿润低山丘陵区为中等背景,在南部的湿润低山丘陵区、热带雨林区和高山峡谷区为高背景,尤其在以云南东南部、贵州、广西西部、湖南西部岩溶区为中心的低温成矿域内,无论岩石、土壤还是水系沉积物,汞含量背景值达到最高.一般情况下,岩石、土壤和水系沉积物之间的汞含量具有继承性,在地理空间分布上呈明显的对栽应关系,并且土壤和水系沉积物之间的汞含量具有相近性,土壤和水系沉积物较岩石更为富集汞.     

平原区城市及周边Hg异常土壤中辰砂的发现及其特征

在我国东部平原区城市及其周边土壤Hg异常查证过程中首次发现辰砂，对其矿物学特征进行了研究，并就辰砂分布与土壤Hg异常的空间对应关系、辰砂的含量与Hg异常土壤中Hg含量间的相关性等问题进行了探讨。结果表明，辰砂是Hg异常土壤中Hg的一种主要存在形式。这一发现对研究和评价Hg异常土壤的生态环境效应具有重要的理论和实用价值。     

Farmland mercury contamination in the vicinity of an organic chemical factory in Guizhou,China

This study assesses the level of contamination of Hg in farmland soils along the irrigating channel downstream from Guizhou Organic Chemical Factory （GOCF）, where metallic mercury is used as a catalyst to produce acetic acid. The total input of mercury into the environment, as announced by GOCF, is 140 t in the past 30 years （1971-2000）. Sampling sites were chosen based on the distance from the source of pollution--the chemical factory. A total of 39 samples were collected from the study area and analyzed for total mercury concentrations and methyl mercury concentrations. The characteristics of vertical and horizontal distributions of total mercury and methyl mercury in the study area （farmland） are described in this paper. Much attention was paid to the transformation of inorganic Hg into organic mercury species in soils as well. The results showed that the farmland has been heavily contaminated by Hg. Land cultivation activity, land utilization style and distance from the pollution source could be the dominant factors controlling the distribution of THg and MeHg. It is observed that active transformation of inorganic Hg into organic mercury species （MeHg） usually takes place in paddy soils.     

Les minéraux à Cu,Sb, Ag,Hg des minerais de Pb-Zn de Sakiet Koucha (diapir de Sakiet Sidi Youssef,Tunisie septentrionale)

Résumé La formation à anhydrite du diapir de Sakiet Sidi Youssef contient aux environs de Sakiet Koucha des minéraux à Cu, Sb, Ag, Hg, au sein des minerais de type BPG habituels des formations corticales des diapirs de Tunisie septentrionale.L'association minérale comprend: pyrite, cuivres gris, chalcopyrite, bournonite, blende, galène, et un amalgame Ag-Hg. La composition des cuivres gris est très variable, du pôle tétraèdrite au pôle freibergite. La composition de l'amalgame argentifère est de stoechiométrie peu courante (Ag 0,71 Hg 0,26). Cette relative richesse en Ag est un caractère déja mis en évidence dans les concentrations du dôme de Hockley en Gulf Coast, ce qui suggère qu'il s'agit d'une caractéristique propre à ce type de gisement lié aux diapirs.Par ailleurs, le rapprochement entre la présence de mercure dans le minerais, et l'existence au Nord du gisement d'un district à cinabre lié au volcanisme néogène, suggère que les phénomènes magmatiques récents ont pu avoir une influence dans cette région pourtant plus méridionale.

---

The CaSO₄ formation of the Sakiet Sidi Youssef diapir (Northern Tunisia) hosts a Cu, Sb, Ag, Hg mineral association (Sakiet Koucha occurence) which is distinct from the usual BPG associations known in the cortical formations of other Triassic diapirs in the same district.It includes: pyrite, fahl ore group minerals, chalcopyrite, bournonite, sphalerite, galena and an Ag-Hg amalgam. The fahl ore group is highly variable in composition and grades from tetrahedrite to freibergite. An unusual stoichiometric compound has been determined: Ag 0.71 Hg 0.26.The presence of Ag minerals is similar to the concentrations described in the Hockley dome, on the Gulf Coast, which would reinforce the view that it is characteristic for this kind of deposit.As for the presence of Hg, the existence of a zone of cinnabar linked to Neogene volcanism immediately North of this deposit introduces the question of the influence of magmatic processes in this area.

     

Physical partitioning of mercury in till: an example from central British Columbia, Canada

The physical partitioning of Hg into different grain size fractions of till is predominantly controlled by the primary bedrock mineralogy, the distance of glacial transport, and the relative stability of cinnabar (HgS) in the soil weathering environment. At sites located short distances down-ice from bedrock cinnabar mineralization, the highest Hg concentrations in unoxidized till were measured in the sand- and granule-sized fractions reflecting the abundance of cinnabar in those size ranges. Similar partitioning was measured in oxidized till as cinnabar was found to be relatively resistant to postglacial weathering. Discrete clay-sized cinnabar grains obtained from the unoxidized till were viewed under the scanning electron microscope and suggest that the terminal grade of cinnabar is in the clay-sized range. In till collected from areas barren of cinnabar mineralization, the highest Hg levels were found in the clay-sized fraction which is attributed to the high adsorption of Hg by clay minerals.     

The geochemical characteristics of mine-waste calcines and runoff from the Wanshan mercury mine,Guizhou, China

Mercury and other geochemical parameters were measured in mine-waste calcines, stream sediments and surface waters from the Wanshan Hg district in the Guizhou Province of China to evaluate adverse effects of Hg to the surrounding environment. Wanshan ore is dominantly cinnabar, and lacks other sulfide minerals and as a result, heavy metals other than Hg are rare in the calcines and mine-water runoff. Host rocks in the Wanshan area are dominantly carbonates, which upon weathering, produces alkaline-water runoff. Surface waters emanating from calcine piles have water pH varying from 10.6 to 11.8, contain high EC values, and variable major element geochemistries. Dissolved Hg concentration decreases from 300 to 1900 ng/l in mine water to 72 ng/l in stream water collected significantly downstream from the mine. High concentrations of Hg in mine-waste calcines and alkaline surface water are the major threats to the surrounding environment. Alkalinity is also naturally attenuated downstream from the Wanshan mine. However, erosion and transport of Hg in sediment and water and highly alkaline mine-water runoff, may adversely affect sediment, aquatic and biological columns downstream from the Wanshan mine area.     

贵州万山汞矿尾矿堆及地表水的环境地球化学特征

对贵州万山汞矿区尾渣堆(主要为炉渣组成)、地表水及河流沉淀物的汞迁移进行了研究。由于赋矿岩石为白云岩，高温煅烧的炉渣中含CaO等碱性物质，炉渣的风化作用释放出汞以及碱性水．流经尾渣堆的地表水碱性强(pH10．6-11．8)、电导率高，且具有明显不同的主要离子组成．万山汞矿矿石单一，主要为辰砂，其他矿石极少，因此炉渣及其渗滤水中除汞外的重金属含量很低．尾渣堆中的汞及碱性物质是对周围环境的主要威胁．在尾渣堆下游汞含量很快降低，约300n，范围内水中的溶解汞从300—1900，ng/L降至72ng／L，而且水的碱性也被中和．但是，由于尾渣堆中的汞及碱性物质含量高，尾渣堆的长时间风化及水流的溶解会将大量汞搬运到周围的土壤及水体并对生物产生不利影响．     

Assessment of Hg-contamination in soils and stream sediments in the mineral district of Nambija,Ecuadorian Amazon (example of an impacted area affected by artisanal gold mining)

The Nambija Mineral District (NMD) is located in the southeastern part of Ecuador, east of Zamora (Zamora Chinchípe's country), Ecuadorian Amazon. In this district, Au occurrences have been know since colonial and pre-colonial times, but only after the early 1980s has intensive artisanal Au mining activity been developed. Currently, the different NMD Au occurrences continue to be exploited by artisanal operations and are difficult to control in the study area. The environmental impacts due to Au mining are a consequence of the illegal situation and deficiency in controlling the techniques of ore exploitation. The Au extraction is carried out by outdoor amalgamation, so the indiscriminate use of Hg by artisanal miners, associated with careless methods of tailings disposal, has caused occupational exposure and environmental degradation. The present study evaluated the geochemical dispersion and concentrations of local contamination of metallic Hg in soils, stream sediments and mine tailings in the NMD area. This article aims to contribute to the discussion of environmental changes caused by the artisanal Au mining in the Nambija district. A total of 82 samples (32 soil, 40 stream sediment and 10 mine tailings) were analyzed. The results were compared with the Hg levels in soil and stream sediments considered not to be contaminated in the Nambija mining area and in other areas where Hg is mined in the Amazon basin. In this work, mean total Hg (T-Hg) concentrations of 1.7 μg g⁻¹ in soils and 2.7 μg g⁻¹ in stream sediments have been found. Mercury values in the mine tailing samples revealed values ranging from 89 to 1555 μg g⁻¹. The results found for Hg in the different analyzed materials pointed to contamination of the studied area by this metal, while soil erosion is responsible for an increase in stream sediment's T-Hg concentrations in the different aquatic ecosystems of the Nambija Creek and Nambija River.     

城镇周边土壤Hg异常成因机理研究

普遍出现在城镇及其周边土壤中的Hg异常受到极大关注,但是对此类异常到底具有怎样的生态危害目前还没有明确的结论原因之一就是对异常的成因机理缺乏准确认识。在13个中心试验区及其周围几十个城镇获得的试验研究结果表明,出现在城镇周边地区的土壤Hg异常,均与土壤中的辰砂矿物有关,而且辰砂在形成土壤Hg异常中起到重要作用。此类辰砂是叠加到土壤中的Hg经过形态转化形成Hg2 ,然后与S2-结合生成HgS,进而结晶形成的首次给辰砂的次生成因学提供了一种可能性。辰砂的形成使Hg以矿物态形式固定在土壤中,导致土壤Hg含量增高,形成土壤Hg异常。此项研究成果对土壤Hg异常生态效应评价及预警预测研究具有重要意义。     

Potentially harmful elements in rice paddy fields in mercury hot spots in Guizhou, China

Levels of the chalcophile metals Hg, Pb, Cd, Cu and Zn and the metalloid As in soils from rice paddy fields were assessed in two regions impacted by different industrial activities in Guizhou province, China. The two study areas (Wanshan and Qingzhen) have previously received attention in the international literature due to heavy Hg pollution, though levels of other potentially harmful elements have not previously been reported. The regions were selected as representing two important, but categorically different metal(loid) contaminated areas in China: Wanshan has been a major region for Hg production while Qingzhen is an important region for a large range of various heavy industries based on coal as an energy source.Within a limited distance of the Hg mine tailings in Wanshan the rice paddy fields are heavily contaminated by Hg (median concentration 25 μg g⁻¹, maximum 119 μg g⁻¹) and moderately contaminated by Zn and Cd (median concentrations of 86 and 0.9 μg g⁻¹, respectively). Zinc and Cd levels correlate well with Hg contamination, which indicates a similar source and mechanism of transport and accumulation. Other studies have concluded that the main sources of Hg contamination in Wanshan are the numerous Hg mine tailings. This is likely as these metals are all geochemically associated with the mineral cinnabar (HgS). The other chalcophile elements (Pb, Cu and As) are nevertheless found at background levels only. In Qingzhen the soils were found to contain elevated levels of As and Hg (median concentrations of 38 and 0.3 μg g⁻¹, respectively). These are elements that are known to be more associated with coal and released during coal combustion.