Mercury contents of some greek soils

Mercury contents were determined for horizons or layers of eleven profiles in agricutural areas and three in industrial areas of Greece.Mercury contents were determined for horizons or layers of eleven profiles in agricultural areas and three in industrial areas of Greece.Contents ranged from 25 to 98 ppb in profiles from agricultural areas. No trends in distribution within profiles or among kinds of soils were evident. Moreover, the levels are within the ranges found in uncontaminated soils elsewhere in the world. The contents are therefore considered to be normal background levels for soils of Greece. Amounts of mercury were positively correlated with cation exchange capacity but not with proportions of clay and organic matter.Contents of mercury reached a maximum of 325 ppb in upper layers and had a minimum of 45 ppb in the deeper parts of the profiles from the industrial areas. The greater amounts in the surface layers are attributed to enrichment through industrial activity. The maximum amounts are well above 150 ppb, a level proposed elsewhere as an upper limit for natural backgrounds.     

Abstracts of Nippon Dojohiryogaku Zasshi

Soil profiles with different vegetation, developed on igneous rock-derived areas in Northern Kyushu have been sampled at 13 locations and analyzed for total Hg with a flameless atomic absorption spectrometer. The associated parent rock was also analyzed. The Hg levels of each rock sample were too low, not exceeding 10 ppb, to exert a significant effect within the profiles on the total Hg content. The Hg content was generally higher in the soil than in the underlying rock, irrespective of the depth of the horizon. Surface enrichment of Hg was observed at most of the sample sites, some paddy fields in particular, resulting in steep concentration gradient down the profiles. The total Hg in all the surface horizons ranged from 459 to 64 ppb with a mean of 197 ppb. Obviously, mercurial application in recent years was a principal factor above all with regard to the establishment of the elevated Hg levels in the upper soil horizon under cultivation.

Man-made loading of this element, probably through rain, was indicated even in the soils under natural vegetation, after taking into account a possible residual Hg concentration in the soil formation process. A close relationship in the profile distribution pattern between total Hg and organic matter contents was observed. This fact, in conjunction with the results of pyrolysis studies, did suggest that a large proportion of the total Hg in these soils could be firmly held by chemical forces, very likely as highly insoluble organic complexes.     

Geochemistry of mercury in pristine and flooded ferralitic soils of a tropical rain forest in French Guiana,South America

In ferralitic soils of the dense Guianese forest, mercury (Hg) concentrations of the surface horizons varied from 122 to 318 ng/g d.w. The behaviour and accumulation of Hg is not related to the accumulation of organic matter but to the penetration of humic substances and the progressive adsorption onto iron (Fe) oxy-hydroxydes in the mineral horizons. The flooding of such soils with the creation of a small reservoir has lead to a release of 20% of the Hg initially present. This observation is related to the reduction of the Fe oxy-hydroxydes and to the migration of the organo-metallic complexes to the water column. Although physico-chemical conditions are appropriate for bacterial methylation, methyl Hg (MeHg) levels of these soils are very low. The process regulating MeHg production and its possible loss from the soil are unknown.     

Soil contamination in the zone affected by waste products of Tin Ore Processing in the Khabarovsk region

The degree of soil contamination in the impact zone of the Solnechnyi Tin Ore Processing Plant in the Solnechnyi district of the Khabarovsk region was evaluated. It was shown that the air contamination by the waste products of the ore-processing plant is extremely high with respect to the concentrations of toxic dust and heavy metals. The maximum concentrations of these contaminants exceed the background values by 16–80 times. The bulk contents of Pb, Zn, Cu, As, and Hg in the upper soil horizons within the impact zone exceeded the maximum permissible concentrations and the background values by 2–90 times. Abnormally high concentrations of Zn, As, and Pb were observed not only in the surface 10–cm-thick soil layer but also in the underlying (10–20 cm) horizon. The soil contamination transformed the geochemical sequence of heavy metals typical of the background soils (Zn > Pb > As > Cu > Hg) into a new sequence (As > Pb > Cu > Zn > Hg). The statistical data proved that the intensity of the migration of the heavy metals in the soils decreases with a rise in the soil humus content and a drop in the soil acidity. This should be taken into account in the elaboration of soil-protective measures in the investigated region.     

Heavy metals in 3300-year-old agricultural soils used to assess present soil contamination

For evaluating present concentrations of heavy metals in soils, it is important to be able to determine natural or background soil concentrations. Here, we compare the content of 7 m HNO₃-extractable and 0.2 m Na-EDTA-extractable fractions of cadmium (Cd), zinc (Zn), lead (Pb) and copper (Cu) in present day cultivated A horizons (Ap) under different land uses and 19 buried A horizons (Apb) that have been covered by 3300-year-old burial mounds. The buried A horizons represent a unique opportunity to evaluate background concentrations of heavy metals in top soil. Variations in background concentrations were mainly related to clay content. Using the grain size distribution of present-day topsoils (cultivated and forest/natural A horizons), the background concentrations were calculated and subtracted from observed concentrations prior to an evaluation of soil-type- and land-use-specific metal accumulation. All cultivated soils were significantly enriched with respect to Cd, Pb, Zn and Cu over the last 3300 years and all forest soils were enriched with Pb. The study highlights the importance of using appropriate reference material for assessing present-day metal concentrations and stocks.     

Trace element distributions in soils developed in loess deposits from northern France

A pedo‐geochemical survey was carried out in the Nord‐Pas de Calais region (France) on soils developed in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep horizons, compared with that of the upper continental crust, with that of horizons developed from 21 other sedimentary rocks from the region and with that of loess from various parts of the world, confirms that loess from the Nord‐Pas de Calais region derives from multi‐recycled and well‐mixed ancient sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3 and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction <2 µm (which we define as ‘lutum’). More mobile elements (As, Cd, Hg, Mn, Mo, Sb, Se) are less associated with this fraction. Cadmium is particularly linked to Mn. The distribution of [trace element]/([Al] or [Fe]) in the French loess gives the background content for soils developed from most sedimentary materials in northwestern Europe. Topsoils are enriched with all the trace elements examined, except Co, Cr and Ni. Enrichments with Cd, Cu, Mn and Zn are greater in cultivated soils than in forest soils. Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are mainly due to human contamination through atmospheric fallout. Organic matter seems to act as a sink for all the exogenous trace elements.     

Characteristics of soil profiles affected by smelting of nickel and copper at Coniston,Ontario, Canada

Soil profiles were examined, described and sampled by horizons in various geomorphic positions along a transect originating at the Coniston smelter and extending in a southeasterly direction for approximately 12 km. The samples were then analyzed to determine particle-size distribution, pH, organic carbon and five heavy metals.Within the study area, elevated levels of nickel, copper and iron were found with maximum total concentrations of 1.2, 0.97 and 20.0%, respectively. Manganese and zinc did not occur in above-normal concentrations. The pH values of the soils were depressed with levels as low as 2.4.Near the smelter, erosion from soils on slopes has transferred materials into lower lying areas, thereby rearranging the areal distribution of nickel, copper and iron. Although the surface soil horizons along the entire transect have above-normal concentrations of these elements, only within the eroded area is there marked variability in their vertical distribution.     

Podzolization of soils under individual tree canopies in Southwestern British Columbia,Canada

On Burnaby Mountain in the coastal rainforest of British Columbia there are concentric, circular belts of podzolised soils around the stems of douglas fir and western hemlock trees. The most acid soils occur near each stem, and soils showing the greatest contrast in chroma between the eluvial and illuvial horizons occur beneath the periphery of the canopy of each tree. These circular belts of soils appear to be associated with limited flow of a very acid water from precipitation down a stem and much greater flow of less acid water from the periphery of the canopy.     

Evidence of Elevated Ozone Concentrations on Forested Slopes of the Lower Fraser Valley, British Columbia, Canada

During the summers of 2001 and 2002, hourly average ozone concentrations were measured at three sites of differing elevation (188, 588, and 1221 m.a.s.l.) on the forested south-facing slopes of the Lower Fraser Valley (LFV), British Columbia. Sites experienced ozone concentrations ranging from 0 to 88 ppb in 2001, and 0 to 96 ppb in 2002. Daily patterns were in agreement with previous studies showing morning increases and late afternoon peaks. Reduced diurnal variation increased the exposure of higher-elevation forested sites. An upper-level ridge coinciding with a thermal coastal trough caused above-average ozone concentrations, and the ‘maximum acceptable’ 1-hour National Ambient Air Quality Objective (AQO) of 82 ppb to be exceeded. Maximum ozone concentrations and AQO exceedance frequency both increased with distance eastward in the valley. A preliminary survey of ozone-like injury symptoms on native shrubs suggested that the elevated ozone levels occurring in the LFV may cause injury to forest plants.     

The Effect of Wildfire on Soil Mercury Concentrations in Southern California Watersheds

Mercury (Hg) stored in vegetation and soils is known to be released to the atmosphere during wildfires, increasing atmospheric stores and altering terrestrial budgets. Increased erosion and transport of sediments is well-documented in burned watersheds, both immediately post-fire and as the watershed recovers; however, understanding post-fire mobilization of soil Hg within burned watersheds remains elusive. The goal of the current study is to better understand the impact of wildfire on soil-bound Hg during the immediate post-fire period as well as during recovery, in order to assess the potential for sediment-driven transport to and within surface waters in burned watersheds. Soils were collected from three southern California watersheds of similar vegetation and soil characteristics that experienced wildfire. Sampling in one of these watersheds was extended for several seasons (1.5 years) in order to investigate temporal changes in soil Hg concentrations. Laboratory analysis included bulk soil total Hg concentrations and total organic carbon of burned and unburned samples. Soils were also fractionated into a subset of grain sizes with analysis of Hg on each fraction. Low Hg concentrations were observed in surface soils immediately post-fire. Accumulation of Hg coincident with moderate vegetative recovery was observed in the burned surface soils 1 year following the fire, and mobilization was also noted during the second winter (rainy) season. Hg concentrations were highest in the fine-grained fraction of unburned soils; however, in the burned soils, the distribution of soil-bound Hg was less influenced by grain size. The accelerated accumulation of Hg observed in the burned soils, along with the elevated risk of erosion, could result in increased delivery of organic- or particulate-bound Hg to surface waters in post-fire systems.     

Preliminary Assessment of Oil Contamination Levels in Soils Contaminated with Oil Lakes in the Greater Burgan Oil Fields,Kuwait

Measurements taken for total petroleum hydrocarbons (TPHs), total organic carbon (TOC) and trace metals [vanadium (V), nickel (Ni), cadmium (Cd) and lead (Pb)] in 40 soil samples are used to delineate oil contamination levels and state of oil penetration in soils heavily contaminated with oil lakes in Al-Ahmadi and Burgan oil fields. All soil horizons in Al-Ahmadi profile contain very high concentrations of TPHs down to the depth interval 80–95 cm. In contrast, TPH contaminations are restricted to the upper 50 cm layer in the Burgan profiles, then drop sharply to natural background levels in subsequent soil horizons. A strong and positive relationship exists between the high TOC and TPH contents of the two profiles. The two soil profiles contain contaminations of V and Ni as well as high concentrations of Cd and Pb. Possible sources of these metals are oil contaminants from the lakes and/or deposited airborne oil fallouts. V/Ni ratios of the surface tar sludge and the soil horizons in the two profiles cannot be used in identifying terrestrial oil spills or as indicators of oil contamination in Kuwaiti soils.     

Adsorption of mercury compounds by tropical soils III. Adsorption isotherms

Isotherms for sorption of 2-methoxyethylmercury chloride (Aretan) and HgCl₂ showed that all three soils investigated had a large capacity to adsorb these Hg compounds, the order being Morogoro > Arusha > Dar es Salaam. For all soils, surface horizons adsorbed more Hg at any given concentration of Hg in solution as compared to subsurface horizons. Adsorption isotherms of Aretan, especially at lower equilibrium concentration in soil solution, were much steeper in all horizons and in all profiles. The Freundlich equation described the adsorption of HgCl₂ better than that of Aretan. The adsorption isotherms for Aretan and HgCl₂ showed different forms, implying probably that different adsorption mechanisms were involved.     

郑州市郊土壤重金属的分布变异及来源

分析了郑州市郊区土壤的Cd、Hg、As、Pb、Cr含量,利用地统计学、多元分析和GIS作图等方法分析了郑州市郊区土壤重金属的分布变异和来源。结果表明:郑州市土壤重金属含量10余年来略有上升。土壤Hg、Cd含量分别在6300m和5500 m变程上有不同程度的空间相关性,但土壤Pb、Cr和As的空间变异则呈现较大的随机性。多元分析表明土壤Cd的空间分布主要体现了其自然背景值特征。土壤Cr变异受外源投入的影响较大,但一定程度上也受土壤自然背景因素控制。土壤Pb、As、Hg空间变异都主要受人类活动影响,其中土壤Hg空间变异受土地利用方式影响最明显。     

Mercury Air/Surface Exchange Kinetics of Background Soils of the Tahquamenon River Watershed in the Michigan Upper Peninsula

Air/surface exchange of mercury was investigated over background soils at five sites in the Tahquamenon River watershed in the Michigan Upper Peninsula in the summer of 1998. Measurements of Hg fluxes were performed during middayperiods using the ORNL Teflon dynamic flux chamber. Mean Hg emission fluxes were 1.4±0.3–2.4±1.0 ng m^-2 hr^-1 for three shaded forest sites and 7.6±1.7 ng m^-2 hr^-1 for an open field site. Hg dry deposition was observed at a heavily shaded forest site overwet soils (mean = –0.3±0.2 ng m^-2 hr^-1). Theoverall mean Hg flux was 1.4±1.4 ng m^-2 hr^-1for the four shaded forest sites. The Hg fluxes observed at these sites are similar to those found at other northern background sites. Significant, rapid response of Hg emission to solar radiation was observed over these background soils. Artificial irrigation over these soils induced immediate andmeasurable increases in Hg emission. Soil temperature was found to be less influential to Hg air/surface exchange over these heavily shaded forest background soils than we have seen elsewhere.     

贵州喀斯特山区锑冶炼厂对农业土壤污染特征的影响及风险评价

以贵州省晴隆县大厂镇喀斯特山区废弃锑冶炼厂周围的农田土壤为研究对象,研究了距离冶炼厂烟囱不同距离12个表层土壤样点和5个典型土壤剖面中重金属含量。结果表明表层土壤主要污染元素为Sb、Zn、Pb、Hg、As和Cu,分别是贵州省土壤背景值的58.58、11.96、7.99、7.45、6.70和1.60倍;土壤剖面中8种主要重金属元素垂直变化规律各异,不同层次重金属含量（(Pb除外）)均表现为：距离冶炼厂烟囱越近含量越高,平均含量由高到低依次为：Mn>As>Sb>Cu>Cr>Pb>Hg>Cd,均明显高于全国土壤背景值的平均水平。其中,As、Cr、Mn和Hg平均含量差异较大,与对照相比,主要污染元素为Sb、Hg和As,Hg和As分别为国家土壤环境质量Ⅱ级标准的4.7倍、4.4倍;其次是Cd和Cu,分别为国家Ⅱ级标准的3.0倍、2.7倍。相关分析和聚类分析表明,土壤主要受重金属Cr、Cd、Cu、Sb和As复合污染。采用单因子污染指数和内梅罗综合污染指数法对该地区农田土壤进行了环境风险评价,各层次Cr、Cd、Cu和As含量均超标,污染严重,综合污染指数在1.21 ~ 14.83之间,以重度污染为主;耕作层污染程度由高到低顺序为：大厂村（(冶炼厂）)>中心街村>碧康组>田坝组,均属于重度污染,表层污染土壤（(0 ~ 20 cm）)种植农作物存在一定的风险。     

The Effect of Fire on Mercury Cycling in the Soils of Forested Watersheds: Acadia National Park,Maine, U.S.A.

This study compares mercury (Hg) and methylmercury (MeHg) distribution in the soils of two forested stream watersheds at Acadia National Park, Maine, U.S.A. Cadillac Brook watershed, which burned in 1947, has thin soils and predominantly deciduous vegetation. It was compared to the unburned Hadlock Brook watershed, with thicker soil and predominantly coniferous vegetation. Soils in both watersheds were primarily well drained. The fire had a significant impact on the Cadillac watershed, by raising the soil pH, altering the vegetation, and reducing carbon and Hg pools. Total Hg content was significantly higher (P > 0.05) in Hadlock soils (0.18 kg Hg ha^-1) compared to Cadillac soils (0.13 kg Hg ha^-1). Hadlock O horizon had an average Hg concentration of 134±48 ng Hg g^-1 dry weight, compared to 103±23 ng Hg g^-1 dry weight in Cadillac O horizon. Soil pH was significantly higher in all soil horizons at Cadillac compared to Hadlock soils. This difference was especially significant in the O horizon, where Cadillac soils had an average pH of 3.41±0.22 compared to Hadlock soils with an average pH of 2.99±0.13.To study the mobilization potential of Hg in the O horizons of the two watersheds, batch adsorption experiments were conducted, and the results were modeled using surface complexation modeling. The results of Hg adsorption experiments indicated that the dissolved Hg concentration was controlled by the dissolved organic carbon (DOC) concentration. The adsorption isotherms suggest that Hg is more mobile in the O horizon of the unburned Hadlock watershed because of higher solubility of organic carbon resulting in higher DOC concentrations in that watershed.Methylmercury concentrations, however, were consistently higher in the burned Cadillac O horizon (0.20±0.13 ng Hg g^-1 dry weight) than in the unburned Hadlock O horizon (0.07±0.07 ng Hg g^-1 dry weight). Similarly, Cadillac soils possessed a higher MeHg content (0.30 g MeHg ha^-1) than Hadlock soils (0.16 g MeHg ha^-1). The higher MeHg concentrations in Cadillac soils may reflect generally faster rates of microbial metabolism due to more rapid nutrient cycling and higher soil pH in the deciduous forest. In this research, we have shown that the amount of MeHg is not a function of the total pool of Hg in the watershed. Indeed, MeHg was inversely proportional to total Hg, suggesting that landscape factors such as soil pH, vegetation type, or land use history (e.g., fire) may be the determining factors for susceptibility to high Hg in biota.     

Effects of Recent Human Colonization on the Presence of Mercury in Amazonian Ecosystems

Three Hg sources were characterised and mass balance calculations were used to determine their relative contributions to the contamination of the Amazonian environment. About an order of magnitude more Hg is emitted to the atmosphere by goldmining activity than by the burning of forest biomass. However, anthropogenic atmospheric Hg cannot account for the high Hg burdens found in terrestrial ecosystems: deposition of Hg from goldmining sources is estimated to account for less than 3% of the Hg present in the surface horizons of soils. We propose that erosion of deforested soils following human colonization constitutes a major disturbance of the natural Hg cycle. Deforestation thus increases soil Hg mobilisation by runoff, which may explain the increase of Hg burdens in Amazonian aquatic ecosystems in newly colonized watersheds.     

Comparative characterization of microbial communities in kurgans,paleosols buried under them,and background surface soils in the steppe zone of the Lower Volga region

A comparative analysis of the state of microbial communities in kurgans, paleosols buried under them, and background surface soils in the dry steppe zone of the Lower Volga region has been performed. It is shown that the population density of microorganisms of various trophic groups in the kurgans is an order of magnitude lower than that in the A1 horizon of the corresponding buried paleosols and background surface soils within the areas of chestnut, light chestnut, and solonetzic soils. The respiration activity of the microbial communities in the upper layer of the kurgans is comparable with that in the A1 horizons of the background surface soils; it decreases in the deeper layers of the kurgans. In the A1 horizon of the buried paleosols, the respiration activity is approximately the same as in the deep layers of the kurgans. In the buried paleosols, the spatial variability in the numbers of soil microorganisms is approximately the same or somewhat higher than that in the background surface soils. The spatial variability in the respiration activity of the buried paleosols is two to four times higher than that in the background surface soils.     

Mercury and Mining in Africa with Special Reference to Tanzania

A study of gold (Au) mining areas in Tanzania is being undertaken to assess environmental impacts arising Gum the use of mercury (Hg) in gold extraction. Initial results already indicated the presence of elevated Hg concentrations in environmental samples from the mining areas. The mean Hg concentration in river sediments in 4.19 μg l. soils within gold mining and processing centres exhibit high Hg content (mean 3.39 μg/g) that decreases rapidly to background regional values within a distance of a few kilometres. A review of published Hg data for sediments, fish and aquatic plants from African inland and coastal waters revealed. with a few exceptions. low Hg concentrations close to natural background levels.