Metals distribution in soils around the cement factory in southern Jordan

Thirty one soil samples were collected from south Jordan around the cement factory in Qadissiya area. The samples were obtained at two depths, 0-10 cm and 10-20 cm and were analyzed by atomic absorption spectrophotometery for Pb, Zn, Cd, Fe, Cu and Cr. Physicochemical factors believed to affect their mobility of metals in soil of the study area were examined such as; pH, TOM, CaCO3, CEC and conductivity. The relatively high concentrations of lead, zinc and cadmium in the soil samples of the investigated area were related to anthropogenic sources such as cement industry, agriculture activities and traffic emissions. It was found that the lead, zinc and cadmium have the highest level in area close to the cement factory, while the concentration of chromium was low. This study indicate that all of the metals are concentrated on the surface soil, and decreased in the lower part of the soil, this due to reflects their mobility and physical properties of soil and its alkaline pH values. The use of factor analysis showed that anthropogenic activities seem to be the responsible source of pollution for metals in urban soils.     

Modelling assessment of regional groundwater contamination due to historic smelter emissions of heavy metals

Historic emissions from ore smelters typically cause regional soil contamination. We developed a modelling approach to assess the impact of such contamination on groundwater and surface water load, coupling unsaturated zone leaching modelling with 3D groundwater transport modelling. Both historic and predictive modelling were performed, using a mass balance approach for three different catchments in the vicinity of three smelters. The catchments differ in their hydrology and geochemistry. The historic modelling results indicate that leaching to groundwater is spatially very heterogeneous due to variation in soil characteristics, in particular soil pH. In the saturated zone, cadmium is becoming strongly retarded due to strong sorption at neutral pH, even though the reactivity of the sandy sediments is low. A comparison between two datasets (from 1990 to 2002) on shallow groundwater and modelled concentrations provided a useful verification on the level of statistics of "homogeneous areas" (areas with comparable land use, soil type and geohydrological situation) instead of comparison at individual locations. While at individual locations observations and the model varies up to two orders of magnitude, for homogeneous areas, medians and ranges of measured concentrations and the model results are similar. A sensitivity analysis on metal input loads, groundwater composition and sediment geochemistry reveals that the best available information scenario based on the median value of input parameters for the model predicts the range in observed concentrations very well. However, the model results are sensitive to the sediment contents of the reactive components (organic matter, clay minerals and iron oxides). Uncertainty in metal input loads and groundwater chemistry are of lesser importance. Predictive modelling reveals a remarkable difference in geochemical and hydrological controls on subsurface metal transport at catchment-scale. Whether the surface water load will peak within a few decades or continue to increase until after 2050 depends on the dominant land use functions in the areas, their hydrology and geochemical build-up.     

Heavy-metal pollution and arseniasis in Hetao region, China

In the Hetao region in northern China drinking water has become toxic due to the presence of arsenic (As) and other heavy metals in soil and water. The 7 counties in this region cover approx. 6100 km2, and in all 180,000 people are suffering from the toxic effects of contaminated drinking water. However, very few studies have been carried out in the region on the possible source of this arsenic. This paper is based on studies of the distribution of heavy metals in soil and groundwater. Results show that the average content of As is 0.483 microg g(-1) in groundwater and 13.74 microg g(-1) in soil. These levels are higher than the drinking water standard of 0.05 microg g(-1) recommended by the World Health Organization in 1984, and for the local background level in soil (5.20 microg g(-1)). This heavy-metal content in water and soil decreases gradually with increasing distance from the contaminated area, which fronts the Yin Mountains. The ratios of the Pb and Sr isotope contents in water are closely related to the ratios found in the water of the regions' mining area, and the ratios in soil correspond to the content of As in groundwater and soil in the area where pathological changes have been detected. Results suggest that the contaminants originate in the ore deposit zone fronting Yin mountains in the upper reaches of the Hetao Region.     

The immobilisation and retention of soluble arsenic, cadmium and zinc by biochar

Water-soluble inorganic pollutants may constitute an environmental toxicity problem if their movement through soils and potential transfer to plants or groundwater is not arrested. The capability of biochar to immobilise and retain arsenic (As), cadmium (Cd) and zinc (Zn) from a multi-element contaminated sediment-derived soil was explored by a column leaching experiment and scanning electron microanalysis (SEM/EDX). Sorption of Cd and Zn to biochar’s surfaces assisted a 300 and 45-fold reduction in their leachate concentrations, respectively. Retention of both metals was not affected by considerable leaching of water-soluble carbon from biochar, and could not be reversed following subsequent leaching of the sorbant biochar with water at pH 5.5. Weakly water-soluble As was also retained on biochar’s surface but leachate concentrations did not duly decline. It is concluded that biochar can rapidly reduce the mobility of selected contaminants in this polluted soil system, with especially encouraging results for Cd.     

Review of concentrations and chemistry of trichloroacetate in the environment

This paper reviews the concentrations of trichloroacetate (TCA) in the atmosphere-plant-soil system. Data originate mainly from Europe. The median TCA concentration in rainwater and canopy drip decreased until 1995. From then the median TCA concentration in rainwater remains rather constant while for canopy drip later data are not available. The same seems to hold for concentrations in air although a very limited data set is available. The median concentrations in coniferous needles and groundwater are constant for the period observed. The median TCA concentrations in soil decreased until 1992 and then remained constant.The TCA formation from chlorinated solvents in the atmosphere may explain a substantial percentage of the TCA amount in the atmosphere. The TCA concentrations in rainwater and canopy drip indicate that there will be other sources contributing to 10-50%. Waste incineration, biomass burning and natural formation in the marine boundary layer are potential candidate sources of TCA, but nothing can be said as yet on their TCA emission rates. Anthropogenic emissions of chlorine could also be a source.TCA can be formed from chlorinated solvents by biota. However, for coniferous trees the uptake of TCA from soil may be the predominant route. Biotic and abiotic reactions can cause to formation of TCA in soil, but also formation of TCA from chlorinated solvents by biota that excrete TCA, may contribute. Mass balance calculations of the bioactive soil top layer show that the production rate of TCA in certain soil types could be substantial. The mass balance calculations could not distinguish between natural and anthropogenic sources in soil.     

Fluorine in the soils of the White Sea Basin and bioindication of pollution

Assessment of the pollution level of soils and vegetation by fluorine and heavy metals and also of the state of the soil microflora in the impact zone of Kandalaksha aluminium factory is discussed. The significant pollution of natural media by fluorine in the basin of the White Sea is established. Concentration of the total fluorine in the organogenic horizon of the Al-Fe-humus podzol soil at a distance of 20 km in the northern direction from the source of emission exceeds the background level by a factor of 3. In the epicentre of emission the amount of total fluorine in the soil exceeds the background level by a factor of 7-8 (Tolerable Amount: 4-5-fold). It is noted that the soil becomes more alkaline under the influence of fluorine and the increased content of chromium along the soil profile exceeds PC by a factor of 3 in the vicinity of the factory. The differences in the dimensions of bacterial and fungi biomass along the gradient of pollution were not revealed in the impact zone. But the changes in the taxonomic structure of fungi and in the level of their domination along the gradient of pollution were estimated. Floristic composition of the soil algae is represented mainly by unicellular green algae with Chlamydomonas elliptica and Bracteacoccus minor predominating.     

A pragmatic approach for estimation of source-zone emissions at LNAPL contaminated sites

When considering natural attenuation as a remediation strategy at a site contaminated by a light non-aqueous phase liquid (LNAPL), it is important to consider the emission of contaminants from the source zone. A quantification of source-zone emissions is essential both for comparison with down-gradient mass fluxes to provide an estimate of fractional mass flux reduction, as well as for estimating the source lifetime. Because the spatial distribution of LNAPL at a field site is strongly dependent on both the spill circumstances and the heterogeneity of the geologic materials, which can be problematic for in-situ determination, alternative methods for estimating source-zone emissions are needed. In this work, a three-dimensional multiphase flow and transport modelling approach is used to investigate the relationship between the lateral extent of an LNAPL body and the emission of contaminants to groundwater at a contaminated site. For simulations involving an LNAPL release in an aquifer comprised of heterogeneous porosity and permeability distributions that were generated geostatistically, it is shown that a simple linear relationship exists between the lateral extent of the LNAPL body in the capillary fringe and the emission to the aqueous phase. The parameters describing the relationship are found to be linear functions of the groundwater flow velocity and the vertical infiltration rate. This site-specific relationship provides a simple method to estimate contaminant emissions to groundwater at LNAPL contaminated sites.     

Development of a composite line source emission model for traffic interrupted microenvironments and its application in particle number emissions at a bus station

A composite line source emission (CLSE) model was developed to specifically quantify exposure levels and describe the spatial variability of vehicle emissions in traffic interrupted microenvironments. This model took into account the complexity of vehicle movements in the queue, as well as different emission rates relevant to various driving conditions (cruise, decelerate, idle and accelerate), and it utilised multi-representative segments to capture the accurate emission distribution for real vehicle flow. Hence, this model was able to quickly quantify the time spent in each segment within the considered zone, as well as the composition and position of the requisite segments based on the vehicle fleet information, which not only helped to quantify the enhanced emissions at critical locations, but it also helped to define the emission source distribution of the disrupted steady flow for further dispersion modelling. The model then was applied to estimate particle number emissions at a bi-directional bus station used by diesel and compressed natural gas fuelled buses. It was found that the acceleration distance was of critical importance when estimating particle number emission, since the highest emissions occurred in sections where most of the buses were accelerating and no significant increases were observed at locations where they idled. It was also shown that emissions at the front end of the platform were 43 times greater than at the rear of the platform. Although the CLSE model is intended to be applied in traffic management and transport analysis systems for the evaluation of exposure, as well as the simulation of vehicle emissions in traffic interrupted microenvironments, the bus station model can also be used for the input of initial source definitions in future dispersion models.     

The mathematical modelling of total nitrogen contamination transport via groundwater from a sugar factory in Eskisehir, Turkey

In this study, mathematical modelling of the total nitrogen contamination transport in a porous medium was evaluated in order to determine the potential groundwater pollution caused by a sugar factory in the Eskisehir region of Turkey. Analytical solutions of mathematical modelling were performed to show graphically the distributions of contaminant concentrations. Multiflow computer programming was used to determine the distribution of contaminant concentrations with respect to time and distance. The distribution distance of contaminant concentrations was determined at any time interval. From this study, the potential pollution of groundwater can be effectively estimated. Prediction of pollution by means of the model will help to form the future predictions of water resource management.     

The Impact of Gold Smelter Emissions on Vegetation and Soils of a Sub-Arctic Forest-Tundra Transition Ecosystem

Gold smelters near Yellowknife in Canada's Northwest Territories have emitted large quantities of sulfur dioxide and arsenic since inception of roasting in 1941. Although particulate wastes are well contained by baghouse fitters in the one remaining operating smelter, significant gaseous emissions continue. Soil and vegetation were sampled at 52 sites over an area of about 40 km radius from the source. Plant ecology was studied at 43 of those sites. After preliminary multi-element screening that indicated only arsenic was a serious persistent contaminant, x-ray fluorescence was used to measure arsenic content in sampled materials. The plant ecology data were synthesized into an Index of Vitality with numerical ratings of pertinent factors. In the marginal forests and rocky outcrops of the area, indicator species of vegetation permitted a division into zones of severe, moderate, mild, or no impact in order of increasing distance from the current center of emissions. Severe impact, including killing of trees, is local only. Analyses of foliage indicate little uptake of arsenic which, together with the presence of S0₂ symptoms, point to S0₂ as the main factor causing decline of vegetation. A separate study, abstracted here, supports this view by providing data that show a frequency of at least 2 significant fumigation episodes per growing season. Soil analyses indicate extremely high arsenic contamination near the stack. A monotonie pattern of dispersion yielded a function explainable in terms of rapid condensation of gaseous emissions. The relationship of arsenic in surface soil and vegetation to distance is approximately an inverse square.     

Arsenic behavior in newly drilled wells

In the present paper, inorganic arsenic species and chemical parameters in groundwater were determined to investigate the factors related to the distribution of arsenic species and their dissolution from rock into groundwater. For the study, groundwater and core samples were taken at different depths of two newly drilled wells in Huron and Lapeer Counties, Michigan. Results show that total arsenic concentrations in the core samples varied, ranging from 0.8 to 70.7 mg/kg. Iron concentration in rock was about 1800 times higher than that of arsenic, and there was no correlation between arsenic and iron occurrences in the rock samples. Arsenic concentrations in groundwater ranged from <1 to 171 microg/l. The arsenic concentration in groundwater depended on the amount of arsenic in aquifer rocks, and as well decreased with increasing depth. Over 90% of arsenic existed in the form of As(III), implying that the groundwater systems were in the reduced condition. The results such as high ferrous ion, low redox potential and low dissolved oxygen supported the observed arsenic species distribution. There was no noticeable difference in the total arsenic concentration and arsenic species ratio between unfiltered and filtered (0.45 microm) waters, indicating that the particulate form of arsenic was negligible in the groundwater samples. There were correlations between water sampling depth and chemical parameters, and between arsenic concentration and chemical parameters, however, the trends were not always consistent in both wells.     

High-level arsenite removal from groundwater by zero-valent iron

The objectives of this study were to conduct batch and column studies to (i) assess the effectiveness of zero-valent iron for arsenic remediation in groundwater, (ii) determine removal mechanisms of arsenic, and (iii) evaluate implications of these processes with regard to the stability of arsenic and long-term remedial performance of the permeable reactive barrier (PRB) technology. A high concentration arsenic solution (50 mg l(-1)) was prepared by using sodium arsenite (arsenic (III)) to simulate groundwater at a heavily contaminated Superfund site in the USA. Batch studies indicate that the removal of arsenic is a two-step reaction with fast initial disappearance of arsenite followed by a slow subsequent removal process. Flow-through columns were conducted at a flow rate of 17 ml h(-1) under reducing conditions for 6.6 mo. Kinetic analysis suggested that arsenic removal behaves as a zero-order reaction at high arsenic concentrations. Arsenic removal rate constants decreased with time and arsenic breakthrough was observed in the column study. Arsenic removal capacity of zero-valent iron was determined to be approximately 7.5 mg As/g Fe. Carbonate green rust was identified from the analysis of surface precipitates; arsenite uptake by green rust may be a major mechanism responsible for arsenic remediation by zero-valent iron. Analysis of HCl-extractable arsenic from iron samples indicated that approximately 28% of arsenic was in the form of arsenate suggesting that a surface oxidation process was involved in the arsenic removal with zero-valent iron.     

A Study of Cooling Pond Fog Generation

Airborne particulate and soil materials sampled in the vicinity of a lead/zinc smelter and subsequently digested In nitric-perchloric acids have been analyzed using an inductively coupled plasma-atomic emission spectrometer (ICP/AES). The samples were collected in two communities; a study community situated immediately adjacent to the smelter complex and a control community some 50 kilometers distant. Enrichment of airborne as well as soil materials is discussed and there is evidence of lead, zinc, copper, cadmium, arsenic, and antimony enrichment from the smelting processes. In addition, an aqueous extraction of the airborne materials isolated sulfate, nitrate, fluoride, and ammonia and gave evidence of enrichment due to fugitive SO _x , NO _x , HF, and NH₃ gaseous emissions.     

电动与渗透反应格栅联合修复镉污染地下水实验

通过实验方法研究了地下水中镉污染的电动力学修复效果,并分析其迁移变化特征。实验结果表明,电动修复中由于阴阳两极的氧化还原反应造成电极附近pH值产生明显变化,其中阳极附近的pH值由开始时的7.0逐渐变小到6.8,而阴极附近则相反,由开始时6.9逐渐增大到9.1,表明土壤的酸碱条件变化明显。Cd浓度变化反映在自然渗透条件下含水层中重金属污染物的迁移能力较弱,阳极附近地下水中Cd的去除率仅8.4%,而在电场作用下地下水中重金属的浓度发生明显变化,使得重金属污染物能在电极附近富集而被去除,当实验电场强度为0.5 V/cm时,Cd在阴极的累积使得阳极附近地下水中去除率为72.9%,说明电动修复重金属Cd污染地下水的效果明显好于自然渗透状态。     

Distribution of chromium, cadmium, nickel and lead in agricultural soils collected from Kazanli-Mersin, Turkey

This study reports total levels of chromium, cadmium, nickel and lead in the agricultural land adjacent a factory producing chromate compounds in Kazanli-Mersin. Surface soil samples were collected from fields around the factory as well as from fields farther away to measure contamination due to aerial transportation and deposition of dust produced in the industrial process. Heavy metals in soil were extracted using wet digestion, and concentrations were measured by atomic absorption spectrophotometry. The concentrations were compared with Turkish maximum allowable concentration values. The metal concentrations averaged 80, 0.14, 228 and 431mg1kg^-1 for chromium, cadmium, nickel and lead, respectively. Soil samples contaminated with chromium were mainly found 500–20001m from the factory and decreased with increasing distance from the factory. Elevated chromium and nickel concentrations were determined in the soils around the factory, especially to the northwest (prevailing wind) and west. Lead concentrations exceeded the limit in only roadside soils (4000 and 50001m to the west), but tended to increase in the vicinity of industrial activity (especially in the west, the northwest and the north). The cadmium concentration did not exceed the limit and was within the normal range for soils.     

Arsenic and other heavy metals in soils from an arsenic-affected area of West Bengal,India

Domkal is one of the 19, out of 26 blocks in Murshidabad district where groundwater contains arsenic above 0.05 mg/l. Many millions of cubic meters of groundwater along with arsenic and other heavy metals are coming out from both the hand tubewells, used by the villagers for their daily needs and shallow big diameter tubewells, installed for agricultural irrigation and depositing on soil throughout the year. So there is a possibility of soil contamination which can moreover affect the food chain, cultivated in this area. A somewhat detailed study was carried out, in both micro- and macrolevel, to get an idea about the magnitude of soil contamination in this area. The mean concentrations (mg/kg) of As (5.31), Fe (6740), Cu (18.3), Pb (10.4), Ni (18.8), Mn (342), Zn (44.3), Se (0.53), Mg (534), V (44.6), Cr (33.1), Cd (0.37), Sb (0.29) and Hg (0.54) in fallow land soils are within the normal range. The mean As (10.7), Fe (7860) and Mg (733) concentrations (mg/kg) are only in higher side whereas Hg (0.17 mg/kg) is in lower side in agricultural land soils, compared to the fallow land soils. Arsenic concentrations (11.5 and 28.0 mg/kg respectively) are high in those agricultural land soils where irrigated groundwater contains high arsenic (0.082 and 0.17 mg/l respectively). The total arsenic withdrawn and mean arsenic deposition per land by the 19 shallow tubewells per year are 43.9 kg (mean: 2.31 kg, range: 0.53-5.88 kg) and 8.04 kg ha(-1) (range: 1.66-16.8 kg ha(-1)) respectively. For the macrolevel study, soil arsenic concentration decreases with increase of distance from the source and higher the water arsenic concentration, higher the soil arsenic at any distance. A proper watershed management is urgently required to save the contamination.     

Cadmium exposure from the cement dust emissions: a field study in a rural residence

The cement dust is one of the causes of pollution in the environment. In the present study, the cadmium concentrations of soil and plant specimens taken from a rural area exposed to cement factory emissions were determined and also the blood concentrations and sensitivity conditions in humans residing in this rural area were investigated. The 108 soil (36 for control) and plant specimens were collected from eight different directions of the cement plant located in Cukurhisar town in Eski?ehir city. Blood samples of the individuals residing in this area were taken from 258 subjects (258 for control) following a physical examination, and patch tests were also applied. The results show that the cadmium concentrations of the soil and plant specimens taken from different places in different directions of the factory were higher than in the control areas. The physical examination of subjects did not reveal results different from those of the control group except for the diagnosis of contact dermatitis. The analysis of venous blood samples showed that cadmium concentrations were found to be within the reference values given for both groups, but higher in the subjects (p<0.001). According to the results of patch tests, sensitivity to cadmium was found to be more frequent for the subject group than the control group (p<0.05). Those results show that, although clinical tools revealed no toxic effects for the subject, except contact dermatitis, the cement plant increases cadmium pollution on the surrounding environment.     

Spatial variability of arsenic and chromium in the soil water at a former wood preserving site

Contamination of industrial sites by wood preservatives such as chromated copper arsenate (CCA) may pose a serious threat to groundwater quality. The objective of this study was to characterise the spatial variability of As and Cr concentrations in the solid phase and in the soil water at a former wood impregnation plant and to reveal the fundamental transport processes. The soil was sampled down to a depth of 2m. The soil water was extracted in situ from the vadose zone over a period of 10 months at depths of 1 and 1.5m, using large horizontally installed suction tubes. Groundwater was sampled from a depth of 4.5m. Results showed that arsenic and chromium had accumulated in the upper region of the profile and exhibited a high spatial variability (As: 21-621 mg kg(-1); Cr: 74-2872 mg kg(-1)). Concentrations in the soil water were high (mean As 167 microg L(-1); Cr: 62 microg L(-1)) and also showed a distinct spatial variability, covering concentration ranges up to three orders of magnitude. The variability was caused by the severe water-repellency of the surface soil, induced by the concurrent application of creosote wood preservatives, which leads to strong preferential flow as evident from a dye experiment. In contrast to soil water concentrations, only low As concentrations (<12 microg L(-1)) were detected in the groundwater. High Cr concentrations in the groundwater (approx. 300 microg L(-1)), however, illustrated the pronounced mobility of chromium. Our study shows that at sites with a heterogeneous flow system in the vadose zone a disparity between flux-averaged and volume-averaged concentrations may occur, and sampling of soil water might not be adequate for assessing groundwater concentrations. In these cases long-term monitoring of the groundwater appears to be the best strategy for a groundwater risk assessment.     

Arsenic distribution and pathway scenarios for sediments and water in a peri-urban Mongolian small-scale coal mining area (Nalaikh District,Ulaanbaatar)

The distribution of arsenic (As) in environmental compartments is investigated in the Nalaikh Depression of N-Mongolia. In Nalaikh, lignite coal is mined by artisanal small-scale mining (ASM) approaches. Because As is often associated with sulfuric minerals in coal, it was hypothesized that enrichment of As is related to coal ASM. A second hypothesis considered coal combustion in power plants, and stoves are a key source of As in the local environment. Three mobilization and distribution scenarios were developed for potential As pathways in this semiarid environment. About 43 soil and 14 water sites were analyzed for As concentrations and meaningful parameters in soil and water. About 28 topsoil samples were analyzed in surface-subsurface pairs in order to identify potential eolian surface enrichment. Additionally, fluvial-alluvial sediments and geogenic and anthropogenic deposits were sampled. Water was sampled as surface water, groundwater, precipitation, and industrial water. Results show that As does not pose a ubiquitous risk in the Nalaikh Depression. However, locally and specifically in water, As concentrations may exceed the WHO guideline value for drinking water by up to a factor of 10. A carefully selected sampling strategy allows the evaluation of the distribution scenarios, which reveals a combination of (a) geogenic As in groundwater and distribution via surface water with (b) anthropogenic As redistribution via eolian pathways. An immediate linkage between As redistribution and coal mining is not evident. However, As distribution in fly ash from coal combustion in the local power plant and yurt settlements is the most likely As pathway. Hence, the results indicate the potential influence of diffuse, low-altitude sources on As emission to the environment. As such, this study provides a good example for As distribution under semiarid climate conditions influenced by geogenic and anthropogenic factors.

     

Spatial distribution and vertical variation of arsenic in Guangdong soil profiles, China

Total of 260 soil profiles were reported to investigate the arsenic spatial distribution and vertical variation in Guangdong province. The arsenic concentration followed an approximately lognormal distribution. The arsenic geometric mean concentration of 10.4 mg/kg is higher than that of China. An upper baseline concentration of 23.4 mg/kg was estimated for surface soils. The influence of soil properties on arsenic concentration was not important. Arsenic spatial distributions presented similar patterns that high arsenic concentration mainly located in limestone, and sandshale areas, indicating that soil arsenic distribution was dependent on bedrock properties than anthropogenic inputs. Moreover, from A- to C-horizon arsenic geometric mean concentrations had an increasing tendency of 10.4, 10.7 to 11.3 mg/kg. This vertical variation may be related to the lower soil organic matter and soil degradation and erosion. Consequently, the soil arsenic export into surface and groundwaters would reach 1040 t year-1 in the study area.