Spatial variability of heavy metals in soils across a valley plain in Southeastern China

An investigation was carried out to survey the magnitude and spatial distribution of heavy metals, as well as their relation with soil series, in a valley plain in Southeastern China. Soil was sampled at 159 sites by combining a squared grid and nested sampling strategies along the transect perpendicular to the Qujiang River in Zhejiang Province, China. Total concentrations of six metals, namely Cu, Fe, Mn, Ni, Pb and Zn, were measured. Classical statistics and geostatistics were used to quantify their spatial characteristics. There was a considerable variation in many of these parameters. The total concentrations ranged from 6.8 to 29.3 mg kg⁻¹ for Cu, 6,784 to 18,678 mg kg⁻¹ for Fe, 94 to 385 mg kg⁻¹ for Mn, 6.1 to 20.3 mg kg⁻¹ for Ni, 25.0 to 49.5 mg kg⁻¹ for Pb, and 12 to 160 mg kg⁻¹ for Zn. Pearson correlation coefficients among total metal concentrations and selected soil properties showed a number of strong associations. By virtue of analysis of variance, a predominant influence of soil series on the spatial variability of metal concentrations was observed. All metals were spatially correlated. The semivariograms of Cu, Fe, Mn, Ni and Zn were dominated by short range correlation (600 or 700 m), and that of Pb by long range (1200 m). Block kriging maps of total metal concentrations and soil properties showed strip distributions, perpendicular to the river, in the manner similar to the soil series. Principal component analysis was run to identify common distribution patterns of heavy metals and soil properties. These results illustrate that soil series information of valley plain may be useful for developing management zones for site-specific agriculture.     

Spatial analysis and hazard assessment of mercury in soil around the coal-fired power plant: a case study from the city of Baoji, China

Based on systematic sampling of soil around the coal-fired power plant (CFPP), the content of Hg was determined, using atomic fluorescence spectrometry. The result shows that the content of Hg in soil is different horizontally and vertically, ranges from 0.137 to 2.105 mg/kg (the average value is 0.606 mg/kg) and is more than the average content of Hg in Shaanxi, Chinese and world soil. In this study, spatial distribution and hazard assessment of mercury in soils around a CFPP were investigated using statistics, geostatistics and geographic information system (GIS) techniques. Ordinary kriging was carried out to map the spatial patterns of mercury and disjunctive kriging was used to quantify the probability of the Hg concentration higher than the threshold. The maps show that the spatial variability of the Hg concentration in soils was apparent. These results of this study could provide valuable information for risk assessment of environmental Hg pollution and decision support. An erratum to this article can be found at     

Spatial variability of soil properties in relation to land use and topography in a typical small watershed of the black soil region,northeastern China

Soil degradation resulted from unreasonable land use and erosion has been a serious problem in the black soil region of northeastern China. This paper seeks to understand the relationships between topsoil properties and topography and land use for land management targeting at improving soil quality in this region. A total of 292 soil samples and 81 volumetric rings were taken from a typical small watershed of the region in June 2005 for examining total carbon (TC), total nitrogen (TN), soil texture (classified into gravel, sand, silt, and clay), and bulk density (ρ _b), respectively. Spatial variability of these soil properties was evaluated with classical statistics and geostatistics methods. The results of classical statistics indicated that TC, TN, sand, silt, clay content, and ρ _b were moderate variables while gravel had great variability. Soil properties were mainly correlated to slope position, elevation and land types. Geostatistical analyses showed that the spatial autocorrelation for TC, TN, and silt was weak, strong for clay and moderate for and ρ _b sand, respectively. The spatial variations of soil properties are affected comprehensively by topographic factors, land use, erosion, and erosion control in this watershed. Past erosion, however, is the most important component to induce change of soil properties. In this small watershed, current soil and water conservation measures play an important role in controlling soil loss. But the restoration of soil properties was unsatisfactory. Comparing with untilled soil of this region, TC, TN, silt content are excessively low; whereas ρ _b, sand and clay content are excessively high; gravel appears at most sampling locations. It is necessary for improving soil properties to protect forest and grassland and change cultivation system of farmlands.     

Spatial variability assessment of soil nutrients in an intense agricultural area,a case study of Rugao County in Yangtze River Delta Region,China

Topsoil samples (0–20 cm) (n = 237) were collected from Rugao County, China. Geostatistical variogram analysis, sequential Gaussian simulation (SGS), and principal component (PC) analysis were applied to assess spatial variability of soil nutrients, identify the possible areas of nutrient deficiency, and explore spatial scale of variability of soil nutrients in the county. High variability of soil nutrient such as soil organic matter (SOM), total nitrogen (TN), available P, K, Fe, Mn, Cu, Zn, and B concentrations were observed. Soil nutrient properties displayed significant differences in their spatial structures, with available Cu having strong spatial dependence, SOM and available P having weak spatial dependence, and other nutrient properties having moderate spatial dependence. The soil nutrient deficiency, defined here as measured nutrient concentrations which do not meet the advisory threshold values specific to the county for dominant crops, namely rice, wheat, and rape seeds, was observed in available K and Zn, and the deficient areas covered 38 and 11%, respectively. The first three PCs of the nine soil nutrient properties explained 62.40% of the total variance. TN and SOM with higher loadings on PC1 are closely related to soil texture derived from different parent materials. The PC2 combined intermediate response variables such as available Zn and P that are likely to be controlled by land use and soil pH. Available B has the highest loading on PC3 and its variability of concentrations may be primarily ascribed to localized anthropogenic influence. The amelioration of soil physical properties (i.e. soil texture) and soil pH may improve the availability of soil nutrients and the sustainability of the agricultural system of Rugao County.     

Spatial distribution of metals in urban topsoils of Xuzhou (China): controlling factors and environmental implications

The contamination of soils by metals from various sources is a subject of increasing concern in recent times. Twenty-eight elements (Fe, Ti, Cr, Al, Ga, Pb, Sc, Ba, Li, Cd, Be, Co, Cu, Mn, Ni, V, Zn, Mo, Pt, Pd, Au, As, Sb, Se, Hg, Bi, Ag and Sn) have been analyzed from urban topsoil from the city of Xuzhou. The concentrations of these analyzed elements have been correlated to some soil parameters such as organic matter, pH, cation exchange capacity, carbonate content, and granulometric fractions (clay, silt and sand). Results of the statistical analysis show a large variety and complexity in these relationships. The spatial distributions of these metal concentrations were also constructed using geographical information system. The spatial distribution patterns of the elements analyzed show that traffic and industrial activities are the principal anthropogenic pollutant sources.     

Spatial distribution of heavy metals in soils: a case study of Changxing,China

Six hundred and sixty-five soil samples were taken from Changxing County in Zhejiang Province, China, to characterize the spatial variability of Hg Cd, Pb, Cu, As and Cr. The geostatistics and geographic information system (GIS) techniques were applied, and the ordinary kriging and lognormal kriging were used to map the spatial patterns of the six heavy metals. Hg, Pb, Cu and As were fitted to the spherical model with a range of 85.75, 82.32, 86.10, and 23.17 km, respectively. Cr was fitted to the exponential model with a range of 6.27 km, and Cd was fitted to the linear model with a range of 37.66 km. Both Pb and Cu had strong spatial dependence due to the effects of natural factors including parent material, topography and soil type. Hg, Cd, Cr and As had, however, moderate spatial dependence, indicating an involvement of human factors. Meanwhile, based on the comparison between the original data and the guide values of the six metals, the disjunctive kriging technique was used to quantify their pollution risks. The results showed that only Cd and Hg exhibited pollution risks in the study area. The pollution source evaluated was closely corresponded with the real discharge of industrial production and the application of organomercury pesticides. The results of this study provide insight into risk assessment of environmental pollution and decision making for agricultural production and industrial adjustment of building materials.     

Spatial variability of soil quality in the surroundings of a saline lake environment

The spatial variability of the quality of the soil on the shores of a lagoon affected by hydromorphy and/or salinity can be identified (Laguna de Villacañas, Castilla La Mancha) by the use of multitemporal Landsat images in order to analyse these changes. For this purpose, TM and ETM images along with field observations and certain edaphic laboratory parameters are used. In order to identify saline-hydromorphic soils, the spatial variability of chemical and physical properties of a transect, which includes from Solonchaks to Regosols and Cambisols, have been correlated with the Normalised Difference Vegetation Index (NDVI). This index, chosen for specific dates, has proven to be very useful in detecting halophytic vegetation and relating it to the variability of the quality of these soils.     

Soiling of limestone in an urban environment characterized by heavy vehicular exhaust emissions

The inorganic and organic chemical composition of weathering sulphate patinas on the limestone walls of Emmanuel College, Cambridge, UK, have been analysed by FT-IR spectroscopy, pyrolysis gas-chromatography/mass spectrometry and scanning electron microscopy. The College location is characterized by heavy vehicular exhaust emissions including those from diesel powered public transport vehicles due to its proximity to the main Cambridge coach station. A complex mixture of gaseous and particulate air pollutants are found deposited in the weathering patinas including organic compounds (such as PAHs), which represent markers for present-day vehicular pollution. Slight differences in composition between patinas collected at different heights on the building facades with, in particular, more evidence for a biogenic overprint in samples collected at roof level as opposed to ground (street) level are found. Analytical results confirm how building stones in urban areas acted in the past and still do today as passive repositories for any kind of gaseous and particulate air pollutant present in the surrounding atmosphere; accordingly, weathering patinas are slowly changing their composition to accommodate new classes of present-day air pollutants.     

Spatial variability of soil organic matter and nutrients in paddy fields at various scales in southeast China

The present study examines the spatial dependency of soil organic matter and nutrients in paddy fields at three different scales using geostatistics and geographic information system techniques (GIS). The spatial variability of soil organic matter (SOM), total nitrogen (TN) and available phosphorus (AP) has been characterized using a total of 460, 131 and 64 samples that were, respectively, collected from the Hangzhou–Jiaxing–Huzhou (HJH) Plain (10 km), Pinghu county (1,000 m) and a test plot area (100 m) within the Pinghu county, Zhejiang province of the southeast China. Semivariograms showed that the SOM and TN had moderate spatial dependency on the large scale of HJH plain and moderate scale of Pinghu county with long spatial correlation distances. At the moderate scale of Pinghu county and the small scale of a test plot area, the AP data did not show any spatial correlation, but had moderate spatial dependency in HJH plain. Spherical and exponential variogram models were best fitted to all these soil properties. Maps of SOM and TN were generated through interpolation of measured values by ordinary kriging, and AP by lognormal kriging. This study suggests that precision management of SOM and TN is feasible at all scales, and precision management of AP is feasible at large scales.     

Total gaseous mercury emissions from mercury-enriched soil in Guizhou, China

Guizhou is located in the Circum-Pacific Global Mercuriferous Belt, and mercury concentrations in soil in this area are enriched. In-situ total gaseous mercury （TGM） exchange fluxes between air and soil surface were intensively measured at four sampling sites in Guiyang from 21 May to 16 June, 2003, and five sites in the Lanmuchang mercury mining area in December 2002 and May 2003, respectively. The in-situ Hg flux measurement was conducted with a dynamic flux chamber （DFC） of quartz. Overall, net emissions were obtained from all sampling sites. Soil mercury concentration and solar radiation have been proved to be the two most important parameters to control mercury emissions from soil. Meanwhile, rain events can enhance mercury emission rate significantly.     

Longitudinal variability of soils and structural response of sewer networks

A simple model which describes the soil–pipe interaction and accounts for the longitudinal soil variation has been developed. It is used for the analysis of the static response of a section of a buried sewer. A probabilistic analysis (Monte-Carlo method) enabling to quantify the influence of spatial variability of the geomechanical characteristics of the soil makes possible to study the parameters which can influence and drive the longitudinal response of a section of sewer. The system response is complex, soil–structure interaction depending on three different stiffnesses: soil stiffness, pipe components stiffness and joints stiffness. Various analyses have been performed to identify the parameters whose influence is the larger. A specific attention has been devoted to the fluctuation scale of the soil properties and to the stiffness of joints.     

The use of soil mercury and radon gas surveys to assist the detection of concealed faults in Fuzhou City, China

Soil gas approaches have been proven useful for detecting buried faults in field survey. How about their applicability in urban area? A trial soil gas survey has been conducted in an attempt to evaluate this in Fuzhou City, Southeastern China. The detection was performed by measuring the adsorbed mercury, free mercury and radon gases in soil in the sites such as crop soil, refilled soil and those with shallow groundwater levels. The resulting distributions show that anomalous concentrations of soil gases over faults are generally two to four times as much as those in the surrounding areas. The locations of peak values of absorbed and free mercury could possibly be applied to assist to determine the trend of faults. The background values of free mercury seems to be more stable and the anomalous zones narrower than those of radon gas, therefore, the free mercury method seems to be good for detection at this area, especially in those sites with shallow groundwater levels. The false gas anomalies may occur in such a site as refilled with external soil, refilled pond and abandoned construction bases.     

Spatial variability of soil available Zn and Cu in paddy rice fields of China

As a source of nutrient supplements, the deficiency or excess of micronutrients in soil is directly connected to the plant uptake and, thereby, status of micronutrients in the human population. Proper management of micronutrients requires an understanding of the variations of soil micronutrients across the fields. This study is to investigate the spatial patterns of soil available Zn and Cu in paddy rice fields. Four hundred and sixty three soil samples were taken in Hangzhou–Jiaxing–Huzhou (HJH) watershed in Zhejiang Province, China, and available Zn and Cu were analyzed using an atomic adsorption spectrometer. Geostatistical semivariograms analysis indicated that the available Zn and Cu were best fitted to a spherical model with a range of 40.5 and 210.4 km, respectively. There were moderate spatial dependences for Zn and Cu over a long distance and the dependence were attributed to soil types and anthropogenic activities. The overlay analysis of spatial patterns and soil types gave us greater understanding about how intrinsic factors affect the spatial variation of available micronutrients. Based on the above, macroscopically regionalized management of soil available micronutrients and the implications to potential risk were discussed.     

Review: evaporation of mercury from soils. An integration and synthesis of current knowledge

 Understanding the mechanisms of mercury evaporation from soil to the atmosphere is necessary for tracing the fate of mercury in the biological environment and for assessing potential health effects and the impact of anthropogenic mercury emissions on the environment. In this article an integrating overview of the current knowledge of the mechanisms of mercury evaporation is presented. Abiological and biological formation of Hg(0) and/or (CH₃)₂Hg in the uppermost soil layers are the rate limiting processes of mercury evaporation from soils in background areas; the evaporation rate in background areas is probably strongly influenced by deposited airborne mercury. The evaporation rate limiting factors in mercury enriched mineralized areas with large fractions of total mercury being volatile mercury species (relative to background soil in the non-mineralized vicinity) meteorological variations and the transport characteristics of soils for volatile mercury species. Mercury evaporation rates from background soils are usually <0.2 μg·m^–2·h^–1 and significantly smaller than from mercury-enriched mineralized areas. Received: 20 November 1995 / Accepted: 24 July 1996     

Assessment of temporal and spatial variability of soil salinity in a coastal saline field

Many coastal tideland areas in southern Hangzhou Gulf in Zhejiang Province of China have been successively enclosed and reclaimed for agricultural land uses under a series of reclamation projects over the past 30 years. The variability of soil salinity was considerably great and an understanding of the temporal and spatial components of soil salinity variability is essential before decisions can be made about the feasibility of site-specific management. In this paper, a 5.35-ha field reclaimed in 1996 was selected as the study site and 112 bulk electrical conductivity (EC_b) measurements were performed in situ by a hand held device in the topsoil (0–20 cm) at regular 20-m intervals across the field over a two-year period. Conventional statistics and geostatistical techinques were used to assess the spatial variability and temporal stability of soil-salinity distribution. The results indicated high coefficients of variation in topsoil salinity over the three samplings. Simple mean EC_b comparison revealed that soil salinity increased from winter to spring. Kriged contour maps showed the spatial trend of salinity distribution and revealed the consistently high and low salinity areas of the field. In percentage terms, the proportions of the moderately saline class, strongly saline class, and extremely saline class were 37, 39, and 24%, respectively. Temporal stability map indicated that more than 60% of the study field was determined as the stable class. Based on the spatial and temporal characteristics, a similarity assessment map was created, which presented 5 homogenous sub-zones, each with different characteristics that can have an impact on the way the field is managed. It was concluded that saline soil land might be managed in a site-specific way based on the clearly defined management sub-regions within the field.     

Spatial variability of flow parameters in a stratified sand

The spatial variability in porosity, hydraulic conductivity, compressibility, and various grain size fractions is analyzed for several sets of samples from the Quadra Sand. This unit is a well-sorted, medium grained, horizontally stratified sand with relatively few silt or gravel interbeds. Both random and uniformly spaced sample plans are used. The heterogeneity of the flow parameters is characterized by frequency histograms and their estimated moments, by their sample autocorrelation functions, and the estimated power spectra. Emphasis is placed on the nature of the spatial dependence between neighboring values of the flow parameters. A nearest neighbor stochastic process model is fit to the data to consider its adequacy in describing the spatial dependence within the porosity and hydraulic conductivity sequences. Even though the Quadra Sand is relatively uniform, a fairly complex spatial structure is observed. A simple monotonically decaying autocorrelation function may not adequately represent the spatial continuity. Statistical anisotropy is observed in both the extent of the spatial autocorrelation and in its functional form. Results show the importance of scale in constructing a probability model to describe the spatial variability.     

非饱和土壤水分运动参数空间变异性研究进展与展望

非饱和土壤水分运动参数的空间特征是科学认识大尺度土壤水分动态变化的基础和先决条件。在参考国内外大量文献的基础上,对非饱和土壤水分运动参数的研究进展从模型研究到空间尺度研究进行了分析与评述,指出机理模型研究是未来土壤水分运动参数空间变异性研究的方向,而尺度研究目前研究的精度不够;在对土壤水分运动参数的空间变异性研究各类方法分析和归纳后,指出土壤水分运动参数变异性研究的方法包括直接测定方法和间接估计方法两种,并对各种方法的优缺点及适用条件进行了总结;最后指出土壤水分运动参数空间变异性研究存在的问题主要集中在土壤水分运动参数的空间变异性结果的标准化问题和不同尺度土壤水分运动参数的相互转化等问题。     

Spatial variability of soils and stream sediments and the remediation effects in a Portuguese uranium mine area

The old Senhora das Fontes uranium mine, located in central Portugal, was closed down in 1971. The treatment of ores from this mine and other mines by heap-leach ended in 1982. Seven dumps partially covered by vegetation were left in the area. Soil and stream sediment samples were collected in December 2009. The remediation was carried out from May 2010 to January 2011. Stream sediment samples were collected again in October 2013. Before the remediation, soils from inside the mine influence area have higher Al, As, Co, Cr, Cu, Fe, Ni, Sr, Th, U and Zn concentrations than soils from outside this area, due to radionuclides, metals and metalloid released from the mine dumps. The principal component analysis (PCA) shows a distinction between soils from inside and outside the mine influence area. The U(VI), As(V) and metals from soils can be adsorbed to Fe-oxyhydroxides and the humic acid can increase the U uptake. Soils must not be used for public or private green and residential areas, because they are contaminated in U, As, Co, Cd and Ni. Before the remediation, downstream sediments have higher Al, As, Cu, Mn, Ni, Pb, U and Zn than upstream sediments, due to erosion and percolation of water through the mine dumps. The PCA shows a distinction between downstream and upstream sediments. The U(VI), Th and As(V) can be adsorbed to Fe-oxyhydroxides. The stream sediments are contaminated in As, Mn, Th and U. Downstream sediments are the most contaminated in U and As. After the remediation, upstream and downstream sediments have generally higher Al, Fe, As, Cr, Ni, Th, U and Zn concentrations than before the remediation, attributed to the relocation of dumps. Radionuclides, metals and metalloids were transported by surface water. Consequently downstream sediments have higher Al, As, Cu, Mn, Ni, Th, U and Zn concentrations than upstream sediments. The U(VI), Th and As(V) can be adsorbed to Fe-oxyhydroxides. Stream sediments became more contaminated in U, Th and As than before the remediation, but more intensively downstream.     

Spatial distribution and source diagnosis of polycyclic aromatic hydrocarbons in soils from Chengdu Economic Region,Sichuan Province,western China

Surface soils from the Chengdu Economic Region (CER) were analyzed for sixteen United States Environment Protection Agency priority polycyclic aromatic hydrocarbons (PAHs) to study the spatial distribution and to identify the sources of PAHs. Relatively high concentrations (more than 1500 ngg^− 1) of high molecular weight PAHs were found in Chengdu Plain, in the middle of CER, while high concentrations (more than 500 ng g^− 1) of low molecular weight PAHs were detected in the surrounding mountains. The concentrations of ∑₁₆-PAHs in topsoil samples from CER (12.52–75,431.47 ngg^− 1, average value was 3233.92 ngg^− 1) were higher than that from the southern China (21.91–3077 ngg^− 1, average value was less than 500 ngg^− 1), and they were comparable to concentrations in soils from the northern China (366–254,080 ngg^− 1, mean value was more than 3000 ngg^− 1). The concentrations from CER were also much higher than the concentrations of some world clean regions such as Antarctic (34.9–171 ngg^− 1), European high mountains (9–11,000 ngg^− 1, mean value was 158 ngg^− 1) and some Europe residential (736 ngg^− 1) and arable soils (60–145 ngg^− 1, mean value was 66 ngg^− 1). The ratio of tracer compounds (BaA/(BaA + Chr), Flo/(Flo + Pyr), and IcdP/(IcdP + BghiP)) indicated that the high concentrations of PAHs in soils were mainly derived from fossil fuels combustion in mountain region and from the incomplete combustion of petroleum in developed plain area (such as Chengdu and Deyang). From the above distribution characteristics and ratios of tracer compounds, we inferred the reasons for the distribution pattern of PAHs in CER were the domestic heating, emissions, and the physicochemical properties of PAHs.     

沈阳市新城子区土壤重金属元素的空间变异性

利用地质统计学方法,系统地研究了沈阳市新城子区土壤重金属元素的空间分布及空间变异性特征。研究结果显示,土壤中Cd和Pb的含量明显高于全国平均值和辽宁省土壤背景值。变异函数分析结果表明,Hg具有明显的空间自相关性,Cd、Pb和As均具有中等空间自相关的特征。Cd和Pb含量较高,并呈显著的正相关,主要受灌溉、施肥等外在因素的影响。重金属元素空间变异性的研究对当地土壤环境评价和土地质量评估具有一定的指示和引导作用。