Principal component analysis of trace elements in industrial soils

The concentrations of the elements Cr, Pb, Cd, Zn, Ni, Mn, Cu and As in soil samples from industrial areas in Serbia were studied. The complexity of the data of eight elements in fifty-nine soil samples was reduced by principal component analysis. Three significant factors, in which 78% of the total variance in the data was found, were attributed to possible pollution sources. The crude and fuel oil burning, local smelters and exhaust emissions were shown to impact heavily the soil trace element profile, whereas no distinct soil type factor was observed. This approach, evidencing spatial relationship, enabled a differentiation between the soil samples originating from different areas.Selected article from the Regional Symposium on Chemistry and Environment, Krusevac, Serbia, June 2003, organised by Dr. Branimir Jovancicevic     

Phosphate-induced differences in stabilization efficiency for soils contaminated with lead,zinc, and cadmium

Phosphates can cost-effectively decrease the mobility of Pb in contaminated soils. However, Pb always coexists with other metals in soil, their competitive reactions with phosphates have not been tested. In this study, the abilities of KH₂PO₄, K₂HPO₄, and K₃PO₄ to stabilize Pb, Zn, and Cd in soils contaminated with a single metal or a ternary metal for different phosphorus/metal molar ratios were investigated. Results indicated that the stabilization efficiency of KH₂PO₄, K₂HPO₄, and K₃PO₄ for Pb, Zn, and Cd in single metal contaminated soil (P/M ratio 0.6) was 96.00%–98.74%, 33.76%–47.81%, and 9.50%–55.79%, respectively. Competitive stabilization occurred in the ternary system, Pb exhibited a strong competition, the stabilization efficiency of Zn and Cd reduced by 23.50%–31.64%, and 7.10%–39.26%, respectively. Pyromorphite and amorphous lead phosphate formed with excess KH₂PO₄ or K₂HPO₄ addition, while K₃PO₄ resulted in the formation of a hydroxypyromorphite precipitate. Amorphous Zn and Cd phosphates and hydroxides were the primary products. The immobilization rate of Zn and Cd depends on pH, and increased significantly in response to the excess phosphate application. This approach provides insight into phosphate-induced differences in stabilization efficiency in soils contaminated with multiple metals, which is of theoretical and engineering significance.

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Effective removal of Cd2+ and Pb2+ pollutants from wastewater by dielectrophoresis-assisted adsorption

Dielectrophoresis (DEP) process could enhance the removal the Cd²⁺ and Pb²⁺ with less absorbent. The removal rates of both Cd²⁺ and Pb²⁺ increased with the increase of voltage. The overall removal rate of Cd²⁺ and Pb²⁺ in the binary system is higher than that of Cd²⁺ or Pb²⁺ in the single system. DEP could cause considerable changes of the bentonite particles in both surface morphology and microstructure. Dielectrophoresis (DEP) was combined with adsorption (ADS) to simultaneously and effectively remove Cd²⁺ and Pb²⁺ species from aqueous solution. To implement the process, bentonite particles of submicro-meter size were used to first adsorb the heavy metal ions. These particles were subsequently trapped and removed by DEP. The effects of the adsorbent dosage, DEP cell voltage and the capture pool numbers on the removal rate were investigated in batch processes, which allowed us to determine the optimal experimental conditions. The high removal efficiency, 97.3% and 99.9% for Cd²⁺ and Pb²⁺, respectively, were achieved when the ions are coexisting in the system. The microstructure of bentonite particles before and after ADS/DEP was examined by scanning electron microscopy. Our results suggest that the dielectrophoresis-assisted adsorption method has a high capability to remove the heavy metals from wastewater.     

Geographic sampling of urban soils for contaminant mapping: how many samples and from where

Properly sampling soils and mapping soil contamination in urban environments requires that impacts of spatial autocorrelation be taken into account. As spatial autocorrelation increases in an urban landscape, the amount of duplicate information contained in georeferenced data also increases, whether an entire population or some type of random sample drawn from that population is being analyzed, resulting in conventional power and sample size calculation formulae yielding incorrect sample size numbers vis-à-vis model-based inference. Griffith (in Annals, Association of American Geographers, 95, 740–760, 2005) exploits spatial statistical model specifications to formulate equations for estimating the necessary sample size needed to obtain some predetermined level of precision for an analysis of georeferenced data when implementing a tessellation stratified random sampling design, labeling this approach model-informed, since a model of latent spatial autocorrelation is required. This paper addresses issues of efficiency associated with these model-based results. It summarizes findings from a data collection exercise (soil samples collected from across Syracuse, NY), as well as from a set of resampling and from a set of simulation experiments following experimental design principles spelled out by Overton and Stehman (in Communications in Statistics: Theory and Methods, 22, 2641–2660). Guidelines are suggested concerning appropriate sample size (i.e., how many) and sampling network (i.e., where).

土壤石油污染物生物通风修复的研究进展

生物通风是一种去污效果好、操作费用低的土壤原位修复技术。文章概述了生物通风系统的结构、设计目的、适用范围和优缺点，详细论述了生物通风的国内外研究现状，包括现场应用、影响因素和强化技术及理论研究，并展望了生物通风在我国的应用前景。     

Some Preliminary Observations On Zinc and Cadmium Accumulative Capacity in Arum Italicum Mill

Pot and hydroponic trials as well as tests on samples collected in a mining area and in two different urban sites of Tuscany were carried out on Arum italicum Mill (Italian arum) plants. Zinc and cadmium contents were determined by differential pulse anodic stripping voltammetry (DPASV) in different organs of about 180 samples. After 65 days treatment, zinc and cadmium median contents in leaves of plants grown hydroponically in solutions containing both metals at different concentrations fell within the range of 281-2022 and 8.3-45.1 μg g^-1 (dry weight), respectively. Some Italian arum plants were also cultivated in pots in the presence or absence of malate or citrate in order to evaluate the role of these ligands in zinc and cadmium accumulation. Citrate enhanced cadmium uptake compared to malate.     

Some Preliminary Observations On Zinc and Cadmium Accumulative Capacity in Arum Italicum Mill

Pot and hydroponic trials as well as tests on samples collected in a mining area and in two different urban sites of Tuscany were carried out on Arum italicum Mill (Italian arum) plants. Zinc and cadmium contents were determined by differential pulse anodic stripping voltammetry (DPASV) in different organs of about 180 samples. After 65 days treatment, zinc and cadmium median contents in leaves of plants grown hydroponically in solutions containing both metals at different concentrations fell within the range of 281-2022 and 8.3-45.1 μg g^-1 (dry weight), respectively. Some Italian arum plants were also cultivated in pots in the presence or absence of malate or citrate in order to evaluate the role of these ligands in zinc and cadmium accumulation. Citrate enhanced cadmium uptake compared to malate.     

Effects of eggshell addition on calcium-deficient acid soils contaminated with heavy metals

The eggshell was used to remediate the contaminated soil by heavy metals. The eggshell addition decreased the available state of the heavy metals. The available calcium in the soil increased due to eggshell addition. The efficiency was investigated in different moisture conditions. In this study, effects of water conditions (flooded, wet, or dry) and eggshell dosages (0, 0.1, 1.0, and 10.0 g/kg soil, respectively) on pH variation, content of unavailable state of heavy metals, form of heavy metals, and available nutritious element calcium (Ca) in acid soils contaminated with heavy metals were investigated, respectively. The soil samples were continuously cultivated indoors and analyzed by toxicity characteristic leaching procedure and community bureau of reference (BCR) sequential extraction procedure. The results showed that the addition of eggshell could effectively improve the pH of acid soil and increase it to neutral level. Moreover, the contents of unavailable state of heavy metals Cu, Zn, and Cd increased significantly. Furthermore, when the soil was cultivated under the flooded condition with 1.0 g/kg eggshell, the unavailable state of Cu, Zn, and Cd increased the most, and these heavy metals were transformed into residual state. On the other hand, the amount of available state of Ca increased to 432.19 from 73.34 mg/kg with the addition of 1.0 g/kg eggshell, which indicated that the addition of eggshell dramatically improved the available state of Ca. Therefore, eggshell could ameliorate the soil environment as it led to the decrease of available heavy metals and improvement of fertilization effectively. In a word, this study indicates that the addition of eggshell would be a new potential method for remediation of acid field soils contaminated with heavy metals.     

Phytoaccumulation prospects of cadmium and zinc by mycorrhizal plant species growing in industrially polluted soils

The natural vegetation growing along a wastewater channel was subjected to analyze the uptake of Cadmium (Cd) and Zinc (Zn) and their subsequent accumulation in aboveground and underground plant parts. Species which were mycorrhizal and growing in soils receiving industrially contaminated wastewater were collected along with their rhizospheric soil samples. The nearby uncontaminated control (reference) area was also subjected to sampling on similar pattern for comparison. Both Cd and Zn concentrations were significantly higher in soils of the study area as compared to the reference site. Five plant species i.e. Desmostachya bipinnata, Dichanthium annulatum, Malvastrum coromandelianum, Saccharum bengalense, and Trifolium alexandrinum were analyzed for metal uptake. The maximum phytoaccumulation of Cd was observed in Desmostachya bipinnata (20.41 μg g⁻¹) and Dichanthium annulatum (15.22 μg g⁻¹) for shoot and root tissues, respectively. However, Malvastrum coromandelianum revealed maximum Zn accumulation for both the shoot and the root tissues (134 and 140 μg g⁻¹, respectively). The examination of cleared and stained roots of the plants from both the areas studied revealed that all of them were colonized to a lesser or a greater degree by arbuscular mycorrhizal (AM) fungi. The Cd hyperaccumulating grasses i.e. Desmostachya bipinnata and Dichanthium annulatum, from study area had smaller root:shoot (R/S) ratio as compared to those growing on reference area indicating a negative pressure of soil metal contamination. The lower R/S ratio in the mycorrhizal roots observed was probably due to increased AM infection and its mediatory role in soil plant transfer of heavy metals. Furthermore, comparatively lower soil pH values in the study areas may have played a key role in making the overall phytoavailability of both the metals. Consequently variations in Cd and Zn tissue concentration among species were observed that also indicate the phytoaccumulation potential of the native species.     

Mitigation and remediation technologies for organic contaminated soils

Organic contaminated soils have become a widespread environmental problem, which may lead to a great threat to the quality of agricultural production and to human health. Physical, chemical, and biological technologies have been employed for the mitigation and remediation of organic contaminated soils. This paper reviews the progress of mitigation and remediation technologies for organic contaminated soils and suggests two different strategies for the mitigation of ’slightly-contaminated’ agricultural soils and the remediation of ‘heavily-contaminated’ soils/sites, respectively. On this basis, directions for future research in this field are suggested.     

Enhanced electrokinetic remediation of quinoline-contaminated soils

ABSTRACT

The aim of this investigation was to examine the ability of enhanced electrokinetic (EK) remediation to efficiently remove quinoline from contaminated kaolinite soils. In order to accomplish this, the effect of a voltage gradient and anode buffer concentration on migration of quinoline in kaolinite was determined. The results showed that EK transport process effectively stimulated desorption and movement of quinoline in kaolinite. The rate and distance of migration rose with increasing voltage gradient and anode buffer concentration under certain conditions. The mechanisms that drive quinoline migration by electrodynamic processes were established as attributed to either electromigration or electroosmosis, and both played key roles in driving quinoline to migrate towards the cathode.     

小球藻吸附重金属离子的试验研究

分析了影响小球藻吸附Cu2 ,Cd2 和Zn2 三种重金属离子的主要因素 ,并对不同金属离子之间的吸附抑制开展了初步试验研究 .结果显示 ,小球藻吸附重金属离子的速度快 ,吸附容量大 ,适宜的pH值在 3 0— 5 0之间 ,其吸附等温线与Freundlich方程拟合良好 .另外 ,小球藻对Cd2 的吸附性能明显高于其它离子 .由于电子云分布和轨道杂化等结构因素 ,三种金属离子在小球藻上的吸附选择顺序为 :Cu2 >Cd2 >Zn2 .     

污染土壤的修复技术研究进展

分析了当前我国严峻的土壤环境状况，并从重金属和有机污染物两个方面，全面介绍了当前污染土壤的各种修复技术，包括物理化学修复方法、植物修复方法和微生物修复方法等；对各种方法的修复原理、已取得的研究进展、存在的优缺点及其将来的发展趋势进行了较全面的综述和展望。文章认为，污染土壤修复将是一项非常具有挑战性同时又是一项非常有前途的修复技术，将会对人类健康和经济可持续发展发挥重要作用。     

Heavy metals contamination of soils under oak ecosystems in the Sofia region

We studied the contamination of Cu, Zn, Pb, and Cd in soils under oak ecosystems of urban (U), suburban (SU), and rural (R) regions in Sofia, Bulgaria. The urban sampling sites are located in the large forest parks of Sofia under oak ecosystems, while the others are located between the centre of the town and the surrounding mountains and are also from oak ecosystems. The concentrations of Cu, Zn, Pb, and Cd in soils were measured for identifying the sources and degree of contamination, and calculating the concentration coefficients (Hc) and enrichment factors (EF). The result of applying principal component analysis (PCA), showed that Cd and Pb accounted for the anthropogenic pollution and could be inferred as its tracers, whereas Cu is located mainly in the parent material. The Zn concentration levels were controlled both by its original content in the parent material as well as by anthropogenic pollution. The results obtained for the city forest parks allow for their successful use for recreation purposes.     

Desorption technologies for remediation of cesium-contaminated soils: a short review

Environmental Geochemistry and Health - This review summarizes the mechanisms for desorbing and extracting cesium (Cs+) from clay minerals and soil. Most techniques use ion exchange with acids,...     

Heavy metals in Jamaican surface soils

A regional survey of Jamaican surface soils has been conducted in which more than 200 samples were collected at a sample density of 1 per 64 km² across the island and analysed for total concentrations of 31 elements by instrumental neutron activation analysis (INAA), energy dispersive X-ray fluorescence (EDXRF) analysis and atomic absorption spectrophotometry (AAS). The aim of the survey was to begin the construction of a high-precision geochemical database to provide information on elemental levels in soils for application to environmental studies, agriculture, and human and animal health. Results on the regional scale are presented for As, Cd, Cu, Hg and Pb. Although Jamaican surface soils are enriched in several heavy metals compared with world soil means and crustal abundances, lead is of particular importance at this stage because of its occurrence in residential areas. Except for Cu, the distribution maps of these elements are highly correlated with bauxite which in Jamaica is associated with white limestone geology and residualterra rossa soils.     

活性污泥对重金属离子混合物的生物吸附

采用城市污水处理厂产生的活性污泥研究了影响污泥吸附Zn^2 ，Cu^2 和Cd^2 三种重金属离子的主要因素，在实验条件下，温度对污泥吸附重金属的影响并不显著，而体系Ph值和吸附时间等的影响较为重要，活性污泥对Cu^2 的吸附符合Langmuir模型，Zn^2 则与Freundlich模型的符合程度优于Langmuir模型，Cu^2 的吸附与两个模型的符合程度一致，另外，活性污泥对Cu^2 离子的吸附性能明显高于其他离子，但在实验中未发现不同金属离子之间存在明显吸附抑制或促进。     

Bioavailability of metals and As from acidified multicontaminated soils: Use of white lupin to validate several extraction methods

White lupin is an annual crop that has been used for phytostabilization of acidified multicontaminated (heavy metals and As) soils from the Aznalcóllar spill-affected area, Southern Spain. One of the most important factors for successful phytostabilization is monitoring the pollutant bioavailability in the soil. The aim of this work was to determine the best-suited method for assessing the bioavailability of heavy metals together with As in the Aznalcóllar spill-affected area, by means of a systematic comparison between different extraction methods (Ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA), CaCl₂, NaNO₃, BCR, (NH₄)₂SO₄ and rhizo). Both AB-DTPA and the first step of the BCR method were found to be unsuitable for assessing the bioavailability of heavy metals and As to plants growing in acidic soils. However, CaCl₂-extractable As, Cu, and Zn and NaNO₃-extractable As and Zn were well correlated with their concentrations in plant organs. Rhizo and (NH₄)₂SO₄, with the highest determination coefficients, were the most recommended simple extraction methods to assess the bioavailability of As, Cu, Fe, Mn, and Zn in acidified multicontaminated soils using white lupin as an excluder model plant.     

污染土壤中菲的修复技术研究进展

菲是多环芳烃中的代表性物质,具有"三致"效应,而且菲的蒸汽压小,辛醇-水分配系数高,生物可利用性低,是一种持久性有机污染物。随着化石燃料的大量使用,受菲污染的土壤越来越多,研究菲的修复技术对污染土壤的再利用具有重要意义。结合目前国内外研究进展,综述了污染土壤中菲的修复方法,包括物理修复、化学修复和生物修复。针对各种修复方法,阐述了其原理、修复条件、实例应用和优缺点,重点论述了植物修复和微生物修复方法的降解机理和应用,分析了微生物性质,包括氧、营养物、温度、土壤理化性质、共存污染物等环境因素对生物降解的影响。由于溶解性的菲有较好的迁移转化能力,因此表面活性剂的助溶作用适用于各种修复方法,选择合适的表面活性剂可以提高修复效果。在各种修复技术中,物理修复是通过物理技术实现菲的解吸与富集,无污染,但是去除率低;化学修复是使用氧化剂将菲氧化分解成无毒易降解的小分子物质或通过添加化学淋洗剂增加菲的溶解性,提高迁移转化能力,用时短,但是引入其他试剂,容易造成二次污染;植物修复是通过植物的提取、降解和固定等过程实现菲的修复,尤其是植物的根际环境为微生物的生长提供有利的条件;微生物修复以菲可作为微生物生长的碳源为基础,在分解酶的作用下实现菲的降解,但是生物修复周期长,可利用的生物少,而且可能生成毒性更高的中间代谢产物。因此,寻找合适的修复物种,采用基因技术提高生物的修复能力或多法联用、取长补短可提高修复效率。最后,在共降解理论的基础上,结合重金属和有机污染物共存时,一种物质的存在对另一种物质的降解有促进作用,提出了协同降解的概念,寻求对多种污染物有协同降解或共降解作用的修复方法是今后发展的主要方向。