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.     

Microbial mercury transformations in marine,estuarine and freshwater sediment downstream of the Idrija Mercury Mine,Slovenia

The Idrija Mine, the second largest Hg mine in the world, ceased operation in 1995, but still delivers large quantities of Hg downstream including into the northern Adriatic Sea, 100 km away. Transformation of Hg species in sediment in sites over 60 km from the mine, including marine sites in the Adriatic Sea, was measured to determine the ability of the system to transform and mobilize Hg and to produce methylmercury (MeHg). Cores from a freshwater impoundment, a brackish estuarine site, and three marine sites in the Gulf of Trieste were sectioned anaerobically, and Hg methylation and MeHg demethylation activities determined using radio-techniques (²⁰³Hg for methylation and ¹⁴C-MeHg for demethylation). Total and dissolved Hg and MeHg were determined as were other geochemical parameters. In addition, rates of SO₄ reduction were determined in marine sediment using a ³⁵S technique. Mercury was readily methylated and demethylated at all sites. Marine sediment was investigated in winter and summer with rates of Hg transformation and SO₄ reduction corresponding only in winter. Methylation of Hg in summer displayed subsurface peaks that may have been influenced by bioturbation. Total Hg and MeHg were most abundant in the freshwater, estuarine, and near-shore marine sites, but dissolved pore water Hg and MeHg were highest in the estuarine region where S cycling appeared ideal for the mobilization of Hg. The impoundment sediment also seemed to be a ‘hotspot’ of Hg transformations. MeHg demethylation occurred via the oxidative demethylation pathway (CO₂ produced from MeHg), except in surficial sediment offshore in the Gulf during winter, where sediment was more oxidizing and significant amounts of CH₄ were liberated during MeHg degradation via reductive demethylation. The CH₄ formation was likely due to an increased influence from the expression of MeHg degradative enzymes encoded by the mer detoxification bacterial genetic system. The freshwater site also liberated CH₄ from MeHg, but it appeared to be due to oxidative demethylation by methanogenic bacteria.     

Spatial distribution of soil organic carbon concentrations in grassland of Ireland

Soil organic C (SOC) concentrations in topsoil samples taken at 678 sites in the grassland of Ireland were investigated using statistics and geostatistics. SOC concentrations (Walkley–Black method) follow a lognormal distribution, with a median and geometric mean of 5.0%, and an arithmetic mean of 5.3%. Statistically significant (P<0.01) positive correlation between SOC and silt-plus-clay, and negative correlation between SOC and sand were observed, with lower correlation (P=0.17) between SOC and pH. Lower SOC concentrations were associated with higher percentages of land in tillage. In order to obtain a robust measurement of spatial structure, spatial outliers were detected, and subsequently eliminated, using the local Moran's I index. The spatial distribution of SOC concentrations based on kriging interpolation showed coherent spatial patterns, with the highest values in the western coastal area, and relatively low values in the inland and southeastern coastal areas; soils at higher elevation were also found to contain higher SOC concentrations. These patterns are consistent with the distribution of rainfall within the country.     

Environmental impacts of the abandoned mercury mine in Podljubelj, Slovenia

The Podljubelj mercury mine lies in the NW part of Slovenia. The ore is of hydrothermal-vein type. The ore deposit was exploited between the years 1557 and 1902. Total production of the mine was 110000 tons of ore （360 tons of Hg）. A smelter located close to the mine had been in operation since 1855. The waste material from the mine and the smelter was dumped in close vicinity of the mine. Total quantity of the waste has been estimated at 170000 tons. In order to establish environmental impacts, soil and stream sediment samples were investigated. Soil samples were collected at two different depths （horizons A and B） in a 100 m grid within an 88 ha area. In the vast area also 11 samples of stream sediments were considered. Heavy metals were determined by means of cold vapor atomic absorption spectrometry CV-AAS after aqua regia digestion. Based on the chemical analyses of samples, the estimated mercury mean for soils is 3.67 mg/kg （0.35-244 mg/kg） for horizon A and 1.39 mg/kg （0.17-71.7 mg/kg） for horizon B. The estimated mercury mean for stream sediments is 0.64 mg/kg （0.065-1.36 mg/kg）. The concentrations of mercury in soils generally decrease with depth and distance from the mine. The highest content of Hg was determined in a sample taken in the immediate vicinity of the smelter （719 mg/kg）. The results have shown that on the 9 ha of the study area, the contents of Hg in soils exceeded the officially set limit value for soils （10 mg/kg）. High contents of Hg in soil around the abandoned smelter are a consequence of former atmospheric emissions and technological losses. High contents of Hg were also found in the mine and smelter waste dump. At the edges of the study area and in the samples of stream sediments, Hg concentrations are low.     

Seasonal distribution of total mercury and methylmercury in sediments of the Wujiangdu Reservoir, Guizhou, China

The concentrations of total mercury and methylmercury in sediments were determined at the dam of the Wujiangdu Reservoir in different seasons. Total mercury (HgT) levels in the whole sediment profile were 254.2±47.0 ng/g in winter, 254.2±31.6 ng/g in spring, and 256.7±60.8 ng/g in summer, without significant variations in different seasons or at different depths. In contrast, the methylmercury (MeHg) compounds were most abundant at the sediment-water interface and decreased progressively with depth. MeHg contents of the sediments during different seasons are highly dependent on microbial activity, and seem to be higher when Hg (II)-methylating microorganisms are active. Thus, MeHg levels tend to rise in the loci where nutrient supplies and biological productivity are favorable. The percentage of HgT that is present as MeHg in the sediments increased gradually from December 2003 to April 2004 and to July 2004.     

Mercury in river sediments, floodplains and plants growing thereon in the drainage area of the Idrija mine, Slovenia

Half a millennium mercury production at Idrija is reflected in increased mercury contents in all environmental segments. The bulk of roasting residues from the middle of the 19th century to 1977 was discharged directly into the Idrijca River, and the material was carried at high waters to the Soca River and farther into the Adriatic Sea. It has been estimated that 45500 tons of mercury were emitted into the environment during the operating period of the mine, which ceased production in 1994. In the lower reaches of the Idrijca the riverine deposits with high mercury contents have been, and will be in the future a source of mercury polluted sediment. Stream sediments were monitored at the same locations along the Idrijca and Soca rivers （70 kin） every 5 years since 1991 （1991-2005）. Grain size distribution was determined by dry sieving and fractions for geochemical analysis were prepared （〈0.04 and 〈0.125 mm）. Soils on river terraces were sampled at 5 localities in the lower course of Idrijca. At two locations of the terrace profiles the samples of averaged meadow forage and plantain （Plantago lanceolata） were collected within a 50-meters radius. We found that there was no decrease in mercury concentration in active river sediments during the last 20 years. Upstream from the Idrija Town the mercury concentrations in active river sediments vary from 1 to 10 mg/kg （average 3.3 mg/kg）. From Idrija to Spodnja Idrija the mercury concentrations increase extremely and vary greatly （32-4,121 mg/kg, the average is 734 mg/kg）. From Spodnja ldrija to the Idrijca-Soca confluence is the average 218 mg/kg, and 57 mg/kg downstream in the Soca River sediments.     

Total organic carbon in soils and its relation with manganese concentrations in soils and vegetation close to an abandoned manganese mine

This study aimed at quantifying the total organic carbon (TOC) present in soils within the proximity of the Kgwakgwe Mn oxide ore abandoned mine, Botswana, and establish its relationship with Mn concentrations in soils and vegetation based on multivariate and Geographical Information Systems (GIS) analytical techniques. Four hundred soil samples and 200 vegetation set samples were obtained from a 4 km² area close to the abandoned mine. The TOC in soil samples were determined using a carbon/hydrogen/moisture determinator, and Mn concentrations in soils and vegetation by atomic absorption spectrophotometry. Results were processed using the statistical package for social science (SPSS), GIS, and Remote Sensing (RS) techniques with the Integrated Land and Water Information System (ILWIS), Geosoft Oasis Montaj and ArcGIS software packages. The values for TOC in the soil samples from the study area ranged from 0 wt % to 7.91 wt %, with a mean of 1.90 wt %, and at the control area, from 4.07 wt % to 4.86 wt %. The range of concentrations of Mn in soils was from 36 mg/g to 24908 mg/g and for Mn concentrations in the vegetation samples from 26 mg/g to 3611 mg/g with a mean of 598 mg/g. Results of correlation coefficients depicted very weak negative association except Mn in soils/Mn in leaves which was weak but positive. The statistical data yielded four clusters as follows: cluster one consisted mainly of Mn in leaves, cluster two was constituted of Mn in soils, and cluster four had TOC. Cluster three was dominated by the three parameters but with negative t statistic. The spatial presentation of data presented revealed little or no vegetation in the south eastern area and those close to the mine workings, and some significant vegetation in the north western part of the study area. The low TOC in the soils is associated to low vegetation cover which is considered to have been influenced by the soil clay fraction mineralogy and high concentrations of Mn.     

The distribution and stable carbon isotopic composition of dissolved organic carbon in estuaries

The distributions of dissolved organic carbon (DOC) and the natural carbon isotope ratio of DOC (DO¹³C) in estuaries reflect the predominant sources and sinks of organic matter from both allochthonous and autochthonous origins. The traditional view is that DOC in land-margin ecosystems reflects mainly the mixing of land-derived and oceanic DOC. However, this view is not consistent with the bulk of our data from a survey of DOC and DO¹³C distributions in estuaries on the East and Gulf coasts of the USA. While it is accurate that the DOC in estuaries includes material derived from land and from the ocean, the distributions of DOC and DO¹³C in several estuaries reflect additional DOC inputs from estuarine phytoplankton and tidal marshes. Even when DOC concentrations were distributed conservatively, the isotopic composition of the DOC revealed the existence of a dynamic cycle of DOC input and removal in some systems.     

Stable isotope (C,O, S) systematics of the mercury mineralization at Idrija,Slovenia: constraints on fluid source and alteration processes

The world-class Idrija mercury deposit (western Slovenia) is hosted by highly deformed Permocarboniferous to Middle Triassic sedimentary rocks within a complex tectonic structure at the transition between the External Dinarides and the Southern Alps. Concordant and discordant mineralization formed concomitant with Middle Triassic bimodal volcanism in an aborted rift. A multiple isotopic (C, O, S) investigation of host rocks and ore minerals was performed to put constraints on the source and composition of the fluid, and the hydrothermal alteration. The distributions of the ¹³C and ¹⁸O values of host and gangue carbonates are indicative of a fracture-controlled hydrothermal system, with locally high fluid-rock ratios. Quantitative modeling of the ¹³C and ¹⁸O covariation for host carbonates during temperature dependent fluid-rock interaction, and concomitant precipitation of void-filling dolomites points to a slightly acidic hydrothermal fluid (¹³C–4 and ¹⁸O+10), which most likely evolved during isotopic exchange with carbonates under low fluid/rock ratios. The ³⁴S values of hydrothermal and sedimentary sulfur minerals were used to re-evaluate the previously proposed magmatic and evaporitic sulfur sources for the mineralization, and to assess the importance of other possible sulfur sources such as the contemporaneous seawater sulfate, sedimentary pyrite, and organic sulfur compounds. The ³⁴S values of the sulfides show a large variation at deposit down to hand-specimen scale. They range for cinnabar and pyrite from –19.1 to +22.8, and from –22.4 to +59.6, respectively, suggesting mixing of sulfur from different sources. The peak of ³⁴S values of cinnabar and pyrite close to 0 is compatible with ore sulfur derived dominantly from a magmatic fluid and/or from hydrothermal leaching of basement rocks. The similar stratigraphic trends of the ³⁴S values of both cinnabar and pyrite suggest a minor contribution of sedimentary sulfur (pyrite and organic sulfur) to the ore formation. Some of the positive ³⁴S values are probably derived from thermochemical reduction of evaporitic and contemporaneous seawater sulfates.Editorial handling: P. Lattanzi     

重庆西部表层土壤有机碳储量与密度分布

利用多目标区域地球化学调查数据,估算了重庆西部地区表层土壤有机碳密度和储量。结果表明,重庆西部地区表层(0~20 cm)土壤有机碳储量为41 038 589 t,平均密度为2 929 t·km-2。从地貌类型看,低山(2 984 t·km-2)和中山(2 986 t·km-2)区土壤有机碳密度较高,丘陵区(2 628 t·km-2)最低,山地土壤有机碳储量最丰富。不同类型土壤中,石灰土有机碳平均密度最高(5 043 t·km-2),其次为黄壤(3 756 t·km-2),紫色土最低(2 329 t·km-2),紫色土有机碳储量最大。就土地利用方式而言,林地土壤有机碳平均密度最高(4 071 t·km-2),耕地土壤处于中等水平(2 752 t·km-2),居民及建筑用地有机碳密度最低(2 416 t·km-2),耕地土壤有机碳储量最大。与第二次土壤普查数据对比发现,该区土壤有机碳储量和密度呈降低趋势,表层土壤作为碳源向大气释放碳,尤其是江津、潼南地区土壤有机碳密度分别降低了56.7%、45.1%。     

Environmental influences upon mercury, radon and helium concentrations in soil gases at a site near Denver, Colorado

Variations in soil gas Hg, Rn and He concentrations and meteorological variables were monitored daily at one site over a period of 22 months. Air and soil temperature, humidity, barometric pressure, soil moisture, wind direction and velocity, soil freeze-thaw, water table elevation, crystal strain and gas emissions were determined simultaneously in order to assess the influence of the environmental variables on gas emission.Mercury concentrations were found to be higher in the summer while Rn and He concentrations were higher in the winter. It is hypothesized that adsorption-desorption controls the migration of Hg whereas Rn and He concentrations are controlled by diffusion and mass transport. Gas emissions respond to seasonal and shorter-term changes in environmental conditions. Stepwise multiple regression using gas emissions as the dependent variables suggests that environmental parameters account for 62% of the total Hg variance, 83% of the total Rn variance, and 33% of the total He variance. Temperature, barometric pressure and soil moisture exert the most influence on gas emissions with temperature effects dominating gas emissions throughout the year. Soil gas emissions display a predictable behavior during winter and summer when more stable meteorological conditions exist. During the transitional seasons of spring and fall, soil gas emissions become erratic and exhibit increased variability. Environmental variables are interrelated and appear to control the manner of gas migration.Increased adsorption by solids during the season of falling temperature decreases soil gas Hg<0.0001 ng L⁻¹, which is desorbed as the soil warms in the spring. Transport of Rn and He is primarily by convection. During the winter months, air temperatures are less than soil temperatures promoting upward movement of Rn and He by convection. During the summer, soil temperatures are less than air temperatures and an inversion layer below the level of sampling reduces upward flux and observed concentration.     

Urban expanding pattern and soil organic, inorganic carbon distribution in Shanghai, China

Soil carbon stock changes induced by land-use change play an essential role in the global greenhouse effect and carbon circulation. This paper studies the urban expanding patterns and spatial characteristics of soil organic carbon (SOC) and soil inorganic carbon (SIC) distribution and evolution during the urbanization process of Shanghai, China, based on the data of the regional geochemical survey. Urbanization process in Shanghai, China, has been quickening greatly since the 1980s. The urban area expanded from 193.08 km² in 1980 to 1,570.52 km² in 2005, or up from 3.05 to 24.77% in the past 25 years, and the urban expansion circled the central city region according to the RS images acquired in the periods of 1980, 2000 and 2005. The urban topsoil is slightly enriched with SOC and SIC, which shows obvious spatial variability. By comparison of SOC and SIC distribution in the central urban area, urbanized area during 1980–2000, 2000–2005 and the suburban area, the SOC obviously accumulates in the central urban area, while SOC density in the urbanized area decreases; similarly, the SIC obviously accumulates in central urban area; furthermore, the SIC density increases with urban land use duration extending and urban ecosystem evolving. This paper provides the characteristics of SOC and SIC distribution and evolution during the course of urbanization, which may be useful for assessing the impact of land use and urban development on SOC and SIC pools in urban ecosystem.     

Sources of dissolved organic carbon in forest soils: evidences from the differences of organic carbon concentration and isotope composition studies

There is considerable discussion and uncertainty in the literature regarding the importance of fresh litter versus older soil organic matter as sources of soil dissolved organic carbon (DOC) in forest floor. In this study, the differences of organic carbon concentration and stable isotope composition were analyzed under different background conditions to identify the origins of DOC in forest soil. The data show that there is no significant difference in SOC content between these collected soil samples (P > 0.05), but the litter-rich surface soils have relatively higher DOC concentration than the litter-lacking (P < 0.01) ones, and the δ ¹³C values of DOC (δ ¹³C_DOC) are closer to δ ¹³C of litter than δ ¹³C values of SOC (δ ¹³C_SOC). In the litter-lacking surface soil samples, the range of δ ¹³C_DOC is between δ ¹³C_SOC and δ ¹³C of dominant plant leaves. These results suggest that DOC mainly derive from litter in the litter-rich surface soil with, and the main path of DOC sources may change with surrounding conditions. In addition, δ ¹³C_SOC and δ ¹³C_DOC become more positive, and the absolute values of Δ (δ ¹³C_DOC − δ ¹³C_SOC) decrease with depth in the soil profiles, which indicate that the percentage of DOC below 5 cm, derived from degradation of humus, may increase with soil depth.     

Total mercury and methylmercury in sediments near offshore drilling sites in the Gulf of Mexico

Concentrations of total Hg in sediments near six drilling sites in the Gulf of Mexico were elevated well above average background values of 40–80 ng/g. The excess Hg was associated with barite from discharged drilling mud. In contrast with total Hg, concentrations of methylmercury (MeHg) in these sediments did not vary significantly at nearfield (<100 m) versus farfield (>3 km) distances from the drilling sites. Observed variability in concentrations of MeHg were related to local differences in redox state in the top 10 cm of sediment. Low to non-detectable concentrations of MeHg were found in nearfield sediments that were anoxic, highly reducing and contained abundant H₂S. At most drilling sites, nearfield samples with high concentrations of total Hg (>200 ng/g) had similar or lower amounts of MeHg than found at background (farfield) stations. Higher values of MeHg were found in a few nearfield sediments at one site where concentrations of TOC were higher and where sediments were anoxic and moderately reducing. Overall, results from this study support the conclusion that elevated concentrations of MeHg in sediments around drilling sites are not a common phenomenon in the Gulf of Mexico.     

Spatial distribution of soil organic carbon and total nitrogen stocks in a karst polje located in Bosnia and Herzegovina

Karst poljes in the Dinaric Mountains have a complex hydrological regime and high potential for crop production. Little information is available about soil organic carbon (SOC), total nitrogen (TN), carbon stocks (SOCS), and nitrogen stocks (TNS) in karst poljes located in the Dinaric area. The objective of this paper was to study the spatial distribution of SOC and TN in topsoil (ranged from 9 to 53 cm depth) and whole profile SOCS and TNS (ranged from 15 to 160 cm depth) in the Livno karst polje depression (Bosnia and Herzegovina) using kriging and co-kriging approaches. We used the following properties as co-variates: distance from hills (DFH), distance from the lake (DFL), sand, silt, and clay content, TN, SOC, SOCS, and TNS. We only used the properties that had a significant correlation with the estimated properties as co-variates. The results showed that soils in the study area had high average SOC (7.92%), TN (0.79%), SOCS (191.05 t ha^?1), and TNS (17.91 t ha^?1) values. Histosols had the highest SOCS and TNS and Arenosols the lowest. The experimental variogram of LogSOC and LogTN was best-fitted by the spherical model, while the exponential model was the most accurate for LogSOCS and LogTNS. The spatial dependence was moderate for all studied soil properties. The incorporation of auxiliary variables increased the precision of the estimations from 35.7% (SOC?×?TN) to 49.2% (TNS?×?SOCS).     

安徽滁州地区土壤有机碳储量分布特征研究

利用多目标区域土壤地球化学调查取得的土壤地球化学数据及安徽省第二次土壤普查数据对滁州地区土壤有机碳储量分布特征、有机碳密度及有机碳储量时空变化规律等问题进行了研究.结果表明滁州地区近30年间土壤有机碳储量减少了8.39 Mt.区内大部分地区土壤碳储量表现出“碳源”效应,仅局部地区呈现出“碳汇”效应.滁州地区0~0.2 m表层土层有机碳储量为53.74 Mt,有机碳密度平均为3.42kg/m2,略低于全国平均水平.滁州地区0~1.8 m表层土层中,72%的土壤有机碳储量赋存于0~1.0 m土壤中.通过对滁州地区不同统计单元的中层土壤有机碳储量及密度的分析,系统查明了土壤有机碳的分布特征,为土壤碳循环研究提供了参考依据.     

Extraction and distribution of soil organic and inorganic selenium in coal mine environments of Wyoming, USA

 Selenium (Se), an animal toxicant and aquifer contaminant, occurs in coal mine environments of Wyoming. There is a paucity of information on solution-phase Se speciation in mine soils. The objectives of this study were to compare Se extraction efficiencies of various reagents and to characterize SeO^2– ₃ (selenite), SeO^2– ₄ (selenate) and organic Se components in these extracts. Forty coal mine soils were extracted using DI (deionized) water, hot water (0.1% CaCl₂), AB-DTPA, NaOH, and KH₂PO₄. Each solution was analyzed for total dissolved Se, and inorganic and organic Se fractions. Both inorganic and organic Se fractions were detected in the soil extracts. The order of Se (total, inorganic, and organic) extraction efficiency for different reagents was DI water < hot water < AB-DTPA < NaOH < KH₂PO₄. The inorganic–organic Se ratios in DI water, hot water, AB-DTPA, NaOH, and KH₂PO₄ extracts were 60 : 40, 26 : 74, 61 : 39, 87 : 13, and 52 : 48, respectively, indicating predominance of inorganic Se in all but the hot water extract. Selenite was the dominant inorganic species in AB-DTPA and KH₂PO₄ extracts, while SeO^2– ₄ was the major Se species in the DI water, hot water, and NaOH extracts. Significant correlations (P<0.01) were observed among extractable inorganic Se [NaOH and KH₂PO₄ (r=0.95); hot water and AB-DTPA (r=0.89)], total soluble Se [DI water with hot water (r=0.98) and AB-DTPA (r=0.95)], and Se species [SeO^2– ₃ in AB-DTPA with SeO^2– ₄ in NaOH (r=0.94) and SeO^2– ₃ in KH₂PO₄ (r=0.88)]. These correlations are indicative of Se extraction efficiency, thermodynamically predicted chemical transformations (such as oxidation of SeO^2– ₃ to SeO^2– ₄), and probable interconversions between the organic and inorganic Se fractions (r=0.70 in KH₂PO₄ extracts); as a whole the correlations can be used as statistical validations of possible geochemical processes. Received: 21 August 1995 · Accepted: 16 October 1995     

Toluene sorption behavior on soil organic matter and its composition using three typical soils in China

The effect of soil organic matter (SOM) content and composition on sorption behavior of toluene for fluvo-aquic, red and black soils in China was investigated in batch experiments. Tested SOM was fractionated into two primary sorptive domains (‘soft’ and ‘hard’) to explain the dependence of sorption behavior on SOM composition. All the tested soils exhibited similar sorption kinetics and nonlinear sorption isotherms. Soils with high SOM content possessed a high sorptive capacity. Clay minerals also contributed to the sorptive capacity, especially for fluvo-aquic and red soils with low SOM content. In comparison, after removing most ‘soft’ SOM fraction from soils through hydrogen peroxide treatment, the residual ‘hard’ SOM fraction of three soil samples exhibited a slower sorption rate and a less sorption capacity compared to the untreated soil samples. The nonlinear degree of sorption was positively correlated with the content of ‘hard’ SOM for all soil samples. This is explained by the combined effect of SOM content and the composition on toluene sorption rates, sorption capacity and nonlinear degree of sorption of three typical soils in China.     

高频红外碳硫仪测定土壤/沉积物中总有机碳研究

用盐酸预处理样品以驱除样品中的无机碳,滤出酸不溶物并洗净,待干燥后置于高频红外碳硫仪中,在富氧气流中充分燃烧,有机碳被氧化成CO2,在4.26微米处具有很强的红外特征吸收,符合朗伯比尔定律,通过测量光强度的变化就能换算成混合气体中二氧化碳的含量,进而得出样品中总有机碳的含量。对含有机碳为1.1%的国家一级标准物GBW07423(GSS-09)测试12次,标准偏差为3.45%,对含有机碳为0.45%的一级标准物质GBW07307a(GSD-07a)测试12次,标准偏差为3.10%,对空白测定12次,计算检出限(6δ)为0.004%。     

青藏高原玛曲冬季牧场土壤有机碳空间分布格局研究

选取60个样点,采用分层（0~15 cm,15~30 cm）采样方法,对青藏高原玛曲草地冬季牧场土壤有机碳的空间分布特征进行了系统地研究。结果显示：在水平分布上,玛曲北部（包括西北部）和东南部的有机碳较高（其含量分别为58.78 g·kg^-1和45.78 g·kg^-1）,而东部（包括东北部）和中部的有机碳较低（其含量分别为39.65 g·kg^-1和38.32 g·kg^-1）;在垂直分布上,土壤有机碳随土壤深度的增加而减小,0~15 cm层的有机碳含量约为其表层（0~30 cm）的53.39%~70.61%。这一结果表明,玛曲北部和东南部应成为未来生态功能区建设的重中之重,严禁过度放牧,尤其是对土壤表层破坏较为严重的各种放牧活动。此外,保存现有联户体,并鼓励更多单户组合成新的联户体也有利于该区土壤有机碳的保护。