Heavy metal contents in soil of major towns in the east coast of Peninsular Malaysia

A total of 63 soil samples from 3 different soil profiles （urban, suburban and industrial areas） in major towns in the east coast of Peninsular Malaysia were analyzed for the total concentrations of Cu, Zn, Pb, Ni and Cr. The soil samples were subjected to acid digestion and the concentrations of total metals extracted were measured or flame atomic absorption spectrometry and inductively coupled plasma - atomic emission spectrometry. According to the result of this study, Pb and Zn concentrations in urban soils are much higher than those of industrial and suburban soils. Total concentrations of Cu and Cr in industrial soil samples are high compared to other two soil profiles and Ni concentrations in the suburban area are slightly higher those of urban and industrial soils. Since Malaysia has not yet to come up with her own soil maximum allowable limit, the heavy metal concentrations were compared with the Dutch maximum allowable limit. The results indicated that the median of heavy metals values in the three different soil profiles is still below the Dutch system limit. From the maximum allowable value obtained from the Dutch system, a contamination/pollution （C/p） index for each site was calculated for the set of these five heavy metals. An advantage of using this method is to make a differentiation between pollution （C/p〉1） and contamination （C/p〈1） status in soils as well as being able to characterize each status into 5 different categories （slight, moderate, severe, very severe and excessive）.     

Environmental behaviors of mercury and lead in the soil of polymetallic deposit areas in western Hunan Province

Western Hunan Province is one of the most typical assembling areas of cryogenic metallic deposit in China, as well as a main ore-forming zone for some heavy metals. In the region, Hg and Pb pollution was caused by abnormally high concentrations of Hg, Pb in the natural environment and Hg, Pb exploiting/smelting and other human activities, which make the damage to human health more complicated. Generally, heavy metal pollutants in soil are often long-lasting and consequent, with their emission and/or transport into the environment, resulting in growing hazards to human health posed by elevated heavy metal concentrations in air, water, and food. Therefore, monitoring and understanding their behaviors in soil environment is the most important and urgent task. In this paper, the environmental behaviors and pollution characteristics of soil polluted by Hg and Pb in typical Hg and Pb mining areas in western Hunan were studied. Main results are presented as follows： （1） Western Hunan Province is a high regional geochemical abnormal region on Hg and Pb. The concentrations of Hg and Pb in soils in mercury mining areas were 1 315 and 3. l times higher than the average background of soils in China, respectively. While those in soils in lead mining areas are 14.1 and 6.1 times higher. By using the index of geoaccumulation （Igeo）, it was found that either mercury mining area or lead mining area in western Hunan Province has been polluted by the two elements, the majority of soils in mercury mining areas are seriously polluted by Hg, moderately or light polluted by Pb, while the majority of soils in lead mining areas are moderately or moderately-highly polluted by Pb and moderately-highly polluted by Hg. （2） By the BCR extraction procedures, both Hg and Pb in soils are dominated by residual form, followed by organic-sulfide form. Fe-Mn oxides and acid-exchangeable form are rather low. The total concentrations and each species of Hg and Pb in soils show positive correlations with the concentrations of sands, and negative ones with the concentrations of clays in soils.     

Stabilities of heavy metals in soils treated with red mud

This paper discussed the stabilities of heavy metals in soils treated with red mud. Soil has been polluted by heavy metals more and more seriously during recent several decades, and they are harmful to mankind and animals. The current tendency is to develop in-situ technique by using industrial processing waste as additives to stabilized heavy metals to minimize the disturbance of contaminated soils. Soil samples were collected from the Niujiaotang mining area, Guizhou Province, southwestern China. They were farmed soils polluted weakly by fly ash （QBT） and polluted badly by waste water （BXT） from smelter, respectively. One of the red mud samples （BRM） was collected from Bayer process and the other （CRM） from confederate process in the Alumina Plant of Guizhou. Free metal ion concentrations were analyzed with Donnan Membrane Technique and predicted with ECOSAT. The concentrations of free heavy metal ions in QBT increased after appending CRM, but decreased when adding BRM. The more the red mud was added, the higher the concentration would be, and the free concentrations of nickel and cadmium ions would vary more greatly than those of copper and zinc ions. When appending red muds into BXT, the free concentrations of copper and zinc ions varied little. While those of free nickel and cadmium decreased obviously at the ratio of 2.00%. The variation of the concentration was still biggish after appending BRM at the ratio of 0.50%, but smaller than that of 2.00%. The concentrations of free cadmium ions increased after adding CRM at the ratio of 0.50%. All experimental processes were modeled through ECOSAT. The predicted and measured results were consistent, except for zinc. Contributions of soil sorbents to the heavy metal adsorptions were also modeled through ECOSAT. The sorbents in soil included soil organic matter, iron hydroxides, clay and the Donnan gel of soil organic matter. Compared to the soils without red muds, no matter what kind of red mud and how much was added in soil, the contributions changed slightly.     

Characterization of arsenic-contaminated groundwater and human health risk assessment in Vietnam

The characteristics of arsenic-contaminated groundwater were investigated and the potential risks from groundwater were evaluated in Vietnam. Arsenic contamination in groundwater was found in Ha Nam Province in the northern part of Vietnam. Since groundwater has been used as one of the main drinking water sources in this region, groundwater （n=10） and hair （n=15） samples were collected in the Vinh Tru district, Ha Nam Province, during February of 2006. At the site, the concentrations of anions and silica were analyzed and As（Ⅲ） and As（Ⅴ） species in groundwater were separated with disposable arsenic speciation cartridge. The concentrations of arsenic in groundwater ranged from 13 to 582 μg/L （mean=366 μg/L）. According to the results of arsenic speciation, approximately 90% of arsenic in groundwater existed as As（Ⅲ） species. Average concentrations of iron and manganese were 18 and 0.7 mg/L, respectively. All samples exceeded the Vietnamese drinking water standard of 10μg/L for arsenic and 0.5 mg/L for iron. Also 70% of the groundwater samples were above the Vietnamese drinking water standard of 0.5 mg/L for manganese. However, a real intake of arsenic to human is less than analyzed arsenic concentration because sand filtration units are used to remove iron and arsenic in groundwater in this region. After treatment, arsenic concentrations decreased from 〈1 to 82 μg/L （mean=33 μg/L）. The concentrations of arsenic in hair samples and treated groundwater were compared. Especially, arsenic concentrations in female hair samples and treated groundwater had significantly positive correlation with the Spearman correlation of 0.88 and the P-value of 0.001. Based on the arsenic concentrations in treated groundwater, the assessment of human health risks was conducted.     

A novel strategy using biodegradable EDDS for the chemically enhanced phytoextraction of soils contaminated with heavy metals

For the sake of cost and potential environmental risk, it is necessary to minimize the amount of chelates used in chemically-enhanced phytoextraction. In the present study, a biodegradable chelating agent, EDDS was added in a hot solution at 90℃ to the soil in which garland chrysanthemum （Chrysanthemum coronarium L.） and beans （Phaseolus vulgaris L., white bean） were growing. The application of hot chelate solutions was much more efficient than the application of normal chelate solutions （25℃） in improving the uptake of heavy metals by plants. When 1 mmol kg1 of EDDS as a hot solution was applied to soil, the concentrations ofCu, Zn and Cd and the total phytoextraction by the shoots of the two plant species exceeded or approximated those in the shoots of plants treated with 5 mmol kg^-1 of normal EDTA solution. The concentrations of metals in the shoots of beans were significantly correlated with the relative electrolyte leakage rate of root cells, indicating that the root damage resulting from the hot solution might play an important role in the process of chelate-enhanced metal uptake. The soil leaching study demonstrated that decreasing the dosage of chelate resulted in decreased concentrations of soluble metals in soils. On the 28th day following the application of chelate, the concentrations of soluble metals in the EDDS treated soil were not significantly different from the concentrations in the control soil to which chelates had not been applied.     

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.     

Farmland mercury contamination in the vicinity of an organic chemical factory in Guizhou,China

This study assesses the level of contamination of Hg in farmland soils along the irrigating channel downstream from Guizhou Organic Chemical Factory （GOCF）, where metallic mercury is used as a catalyst to produce acetic acid. The total input of mercury into the environment, as announced by GOCF, is 140 t in the past 30 years （1971-2000）. Sampling sites were chosen based on the distance from the source of pollution--the chemical factory. A total of 39 samples were collected from the study area and analyzed for total mercury concentrations and methyl mercury concentrations. The characteristics of vertical and horizontal distributions of total mercury and methyl mercury in the study area （farmland） are described in this paper. Much attention was paid to the transformation of inorganic Hg into organic mercury species in soils as well. The results showed that the farmland has been heavily contaminated by Hg. Land cultivation activity, land utilization style and distance from the pollution source could be the dominant factors controlling the distribution of THg and MeHg. It is observed that active transformation of inorganic Hg into organic mercury species （MeHg） usually takes place in paddy soils.     

Heavy metal concentrations in soils and plants in the vicinity of Arufu lead-zinc mine,Middle Benue Trough,Nigeria

This study focused on the influence of base metal mining on heavy metal levels in soils and plants in the vicinity of Arufu lead-zinc mine, Nigeria. Soil samples (0-15 cm depth) and plant samples were collected from cul-tivated farmlands in and around the mine, the unmineralized site and a nearby forest (the control site). The samples were analyzed for heavy metals (Fe, Zn, Mn, Cu, Pb, Cr and Cd) by Atomic Absorption Spectrophotometry (AAS). The physical properties of soils (pH and LOI) were also measured. Results showed that soils from cultivated farm-lands have neutral pH values (6.5-7.5), and low organic matter contents (10%). Levels of Zn, Pb and Cd in culti-vated soils were higher than the concentrations obtained from the control site. These heavy metals are most probably sourced from mining and agricultural activities in the study area. Heavy metal concentrations measured in plant parts decreased in the order of rice leavescassava tuberspeelings. In the same plant species, metal levels decreased in the order of ZnFeMnCuPbCrCd. Most heavy metals were found in plant parts at average concentrations normally observed in plants grown in uncontaminated soil, however, elevated concentrations of Pb and Cd were found in a few cassava samples close to the mine dump. A stepwise linear regression analysis identified soil metal contents, pH and LOI as some of the factors influencing soil-plant metal uptake.     

Influence of the environmental behavior and ecological effect of cropland heavy metal contaminants by CO2 enrichment in atmosphere

Recently, the impacts of increasing atmospheric CO2 level on the terrestrial ecological system have been intensively studied. The higher the CO2 concentration, the higher the risk of destabilizing vulnerable carbon pool on ecological safety. Metabolism, biomass, activity, and diversity of microbial communities in soils can be significantly altered by the CO2 enrichment. For instance, it may accelerate carbonate weathering, vary the rhizospheric exudation, and enhance the amount of available C from the upper soil layer. However, how the CO2 enrichment would influence food safety such as species transformation and bioavailability of heavy metals in soils is remained unanswered. The bioavailability of heavy metals is strongly affected by bio-factors in addition to the physiochemical conditions of soils. Different physiological mechanisms and states control plant uptake of heavy metals. The enrichment of CO2 influences physiological functionalities of plants, and in turn, is expected to have impacts on the bioaccumulation of pollutants and the stress adjustment system of plants. Currently, in China soil is heavily polluted, in most cases, combined by organic pollutants and heavy metals. Studies of the environmental behavior and ecological effect of Cu in soil under elevated CO2 levels were conducted in China FACE （Free Air Carbon Dioxide Enrichment） from June to October 2005 using pot experiments. Results showed that the accumulation of Cu and Cd in leaves, stems, roots, and grains of rice growing in Cu contaminated soils was significantly lowered, indicating that the bioavailability of heavy metals in soils decreases with increasing CO2 concentration.     

Response of biomass accumulation and nodulation by Vicia villosa to soil conditions: Evidence from δ13C and δ15N isotopes

Vicia villosa is an annual legume plant,and is mainly used for green manure by farmers in southwest China.Field growth experiments were performed on six plots.The concentrations of mineral nutrients and soluble sugar,and the changes of carbon and nitrogen isotopic composition within and among organs of Vicia were deter- mined.Significant differences in legume growth were found in response to soil type and its moisture conditions.The Vicia villosa was relatively well adapted to growth in limestone soils than sandstone soils.The distribution of sugar concentrations andδ1 3C-differences between roots and leaves indicate that the translocation of sugars from leaves to roots may be restricted by soil drought.Therefore,there was an inhibition of Pi distribution from roots to leaves, resulting in over optimum threshold of N/P ratio.Those may originate from the feedback regulation in the legume, where soluble sugar could not be distributed from leaves to roots.The results ofδ1 5N values in tissues suggest that there should be different preferential use of nitrogen resource by legume during the formation of nodules:before nodule formation the legume preferentially utilizes inorganic nitrogen from soils,but afterwards the nitrogen should be mainly from N2-fixation.Our results indicate that the lack of nodulation development,except for S2,should be ascribed to the factor controlling bi-direction nutrient transfer,which should be efficiency of establishment symbiosis with arbuscular mycorrhiza before nodulation formation.It is predicted that the species of Vicia villosa should be a legume associated with dual symbiosis with rhizobia and mycorrhiza.     

Heavy metals accumulation in urban soils of Belarus： Testing, mapping and ecological risk assessment

Soil pollution is among priority environmental problems in Belarus, especially in cities. Main compound of the health risk are connected with soil pollution-consumption of plants production cultivated at polluted soils. Now in Belarus cultivation of vegetables and potatoes is rather typical at allotment gardens, in rural parts of cities and towns and in suburban regions. Mapping of soil pollution and study of pollutant accumulation in plant production in connections with soil contamination and health risk assessment were conducted in a few large cities of Belarus （Minsk, Gomel, Svetlogorsk, etc）. Investigation includes sampling of soils and vegetation according to a certain plan, sample processing, chemical analysis, results assimilation, mapping, and risk assessment. Contents of soluble compounds （nitrates, sulphates etc.）, total and reactive heavy metals （lead, zinc, cadmium, etc.） were determined. Heavy metal contents were determined by AAS. Elevated levels of heavy metals were detected in soils used for growing vegetables and potatoes. Priority pollutants, as for urban soils on the whole, are lead and zinc. Average accumulation coefficient （related to local background values） for investigated areas within the limits 2.1-7.8. Contents of lead exceeding Maximum Permissible Concentrations （MPC） were detected in 16% of the samples collected in kitchen gardens of Gomel, of zinc in 38% of the samples from kitchen gardens of Svetlogorsk. Average content of zinc in cabbage, carrot and red beet in background conditions amounts to 4 mg/kg, in potatoes, 3.6 mg/kg. In samples of agricultural production from Svetlogorsk the contents of zinc vary from 1.7 to 156.6 mg/kg; average content in cabbage, 25.8 mg/kg, in red beet, 18.0, carrot, 11.8, potatoes, 5.6 mg/kg. For ecological risk assessment from polluted agricultural products consumption the concept of reference dose was applied.     

Human Influence on Heavy Metal Distribution in the Upper Lake Nansi Sediments, Shandong Province, China

Core and surface sediment samples were collected from three sub-lakes ( Lake Nanyang, Lake Dushan and Lake Zhaoyang) in the Lake Nansi Basin, Shandong Province. In order to reveal the characteristics of spatial and historical distribution of heavy metals in different sublakes of the Upper Lake Nansi, heavy metal (As, Cr, Cu, Hg, K, Mn, Ni, Pb, Zn, Al, Fe, Ti and V) concentrations of sediment samples were investigated. Based on the activity of^137Cs in the sediments, the modem accumulation rate of Lake Nansi sediments is 3.5 mm/a. Our results show that the whole Upper Lake Nansi has been already polluted by heavy metals, among which Lake Nanyang has been polluted seriously by mercury, as well as by lead and arsenic, while Lake Dushan has been most seriously polluted by lead and arsenic. Historical variation of heavy metal (Cr, Cu, K, Ni, Zn, A1, Fe, Ti and V) concentrations shows an abrupt shift in 1962, resuiting in a division of two periods: from 1957 to 1962 when metal enrichment increased with time, and from 1962 to 2000 when it decreased with time, while that of some anthropogenic elements such as Hg, Pb and Mn tend to increase toward the surface. However, the variation trend of As in the sediments is different from that of Hg, Pb and Mn, with its maximum value appearing in 1982. Since 1982 the concentrations of As have decreased due to the forbidden use of arsenite pesticides. This variation trend revealed changes in manner of human activity (coal combustion, waste discharges from both industries and urban sewage ) within the catchment during different periods.     

Spatial and temporal distributions of mercury species and controlling factors in Hongfeng Reservoir, Guizhou, China

The Hongfeng Reservoir was built in 1960 and is an alkaline, hyper-eutrophic and seasonal anoxic reservoir due to the contamination from domestic and industrial wastewaters. The water samples at deferent depths from two sampling sites were collected from November 2003 to September 2004 using metal clean protocols. Total Hg （THg）, reactive Hg （RHg）, dissolved total Hg （DHg）, dissolved gaseous mercury （DGM） were measured by gold trap pre-concentration and CVAFS detection. Methyl mercury was measured by distillation followed by aqueous phase ethylation, precollection on a Tenax, isothermal gas chromatography and cold vapor atomic fluorescence detection. There was no discernible seasonal trend （about 8 ng/L） in THg concentration based on the average information developed during the four cruises except for high concentrations at bottom and water-sediment interface in May and September 2004. On the other hand, particulate mercury （PHg） and methyl mercury have discernible seasonal variability. Proportion of PHg increased from 29% in February 2004 to 50% in May 2004. In November 2003, February and May 2004 methyl mercury concentrations were relative low and increased with depth （from 0.13 to 0.40 ng/L）. In September 2004, methyl mercury concentrations increased from 0.14 ng/L in the epilimnion to 0.99 ng/L in the hypolimnion. DGM concentrations varied from 0.024 to 0.11 ng/L and decreased with depth.     

Geochemistry of porewater and sulfate-reducing bacteria in sediment cores from the Chianan Plain, Taiwan

High concentrations of arsenic and humic substances in groundwater from the southwestern coastal plain of Taiwan were well known for their probable relationships with black-foot disease. In order to realize the relationships between the concentrations of humic substances and arsenic in this area, 24 well water samples were analyzed. After filtered through 0.45 μm glass fiber membrane in the field, samples were kept in the dark at 4℃ and then separated into six fractions with varying range of molecular weight （〈0.5, 0.5-1, 1-5, 5-10, 10-50 and 〉50 k Da） by ultrafiltration apparatus （Molecular/Por Stirred Cell system） in the lab. Concentrations of humic substances were measured by fluorescence spectrometer （HITACHI F-2000, ex=370, em=445） and arsenic by FIAS-AA （Perkin Elmer AAnalyst 100, FIAS-400）. On average, only 6.2% of the total arsenic in water existed in the fraction of 〉0.5 k Da. and the others were complexed with humic substances （including humic acid and fulvic acid）. The results demonstrated a distinct positive correlation between the concentrations of humic substances and arsenic.     

Effects of human activities on mercury in the environment in Xi＇an area, China

Effects of mercury on ecosystems and human health are well documented. Human activities have significant impacts on transport, transformation, and fate of mercury in the natural environment. In this study, a gold mining area （Tongchuan）, an urban area （Xi＇an）, and a historical site （Qinshihuan Tomb） in Shaanxi Province, China, was chosen to study the effects of human activities on the transport, transformation, and fate of mercury in the area. Samples of atmospheric precipitate, soil, sediment, pomegranate, corn and those from wells and the rivers that flow through or flow by the city and from the mining area were collected. The EPA methods were used for sample preparation and analysis of these samples. These methods combine acid digestion, chemical reduction, purge and trap with Cold Vapor Atomic Fluorescence Spectrometry （CVAFS）. Preliminary results showed high total mercury concentrations in the water samples collected from a river in Tongguan County. The total mercury concentrations ranged from 133 to 188 ng/L in the water samples collected from the rivers flowing through Xi＇an City. The amount of total mercury in the soil/sediment samples which were collected in the vicinity of Xi＇an ranged from 31.8 to 83.2 ng/g. The total mercury concentrations in the samples of atmospheric precipitate （including rain and snow collected from Sep. 2005 to Jan. 2006） ranged from 106-298 ng/L.     

Distribution of mercury species in water and sediments in Caohai Lake, Guizhou Province

Caohai Lake which is situated in Guizhou Province, has suffered drain project many times since 1958.The main mercury contamination includes industry waste water, litter and waste residue from refine zinc furnace and so on. The water and sediment samples which were collected from Caohai Lake in different seasons using metal clean protocols. Study sites were selected at the upper and down reaches and the tributaries of this lake, respectively. Total mercury （THg）, reactive mercury （RHg） and dissolved mercury （DHg） concentrations were measured by trap pre-concentration and CVAFS detection methods, and the concentrations of particulate mercury （PHg） are equal to difference of THg and DHg. Total methylmercury （MeH） and dissolved methylmercury （DMeHg） concentrations were measured by GC-CVAFS detection method. Mercury in sediment was measured by AAS method. The results in autumn were obtained as follows： the average concentrations of total mercury, reactive mercury,     

Impacts of wastewater irrigation on soils and crops in suburban area of Shiraz, Iran

This preliminary work reported here dealt with potential impacts of wastewater irrigation on soils and crops sampled along the Koshk River canal in the suburban area of Shiraz City, Iran. It also attempts to assess the extent of heavy metal contamination in soils and crops and human exposure risk. For this purpose, samples including soils and plants were collected from two wastewater irrigated sites and a tubewell-irrigated site （marked by A, B and C）. Concentrations of the six heavy metals Ni, Pb, Cd, Zn, Cr and Cu were determined by AAS. Physical and chemical properties of soil samples were also determined. The PLIs and CF for soils and HQ （Hazard quotient） for some vegetables were calculated. The results showed that organic matter content increased from 22% to 30 % in wastewater-irrigated soils as compared to tubewell water irrigated and admixture water irrigated ones. The soil pH was raised by 2 units as a result of wastewater irrigation at site A compared to sites B and C. Wastewater irrigation also result in relatively high concentrations of Ni, Pb and Zn （275.5, 441.3 and 177 mg/kg, respectively） in wastewater irrigated soils over tubewell water irrigated soils. These levels are higher than the maximum permissible limits in unpolluted soils, indicating that a degree of contamination has occurred. This was confirmed by calculated PLIs and contamination factors in soil samples, The results also showed some crops cultivated at sites A and B contained high levels of Ni and Cd beyond the maximum permissible concentrations and those cultivated at site C. The concentrations of these heavy metals are within or very close to the critical levels. HQ indices and daily intake calculated in respect of metal contents in some vegetables （spinach, lettuce and celery） showed that toxic risk due to Cd in these vegetables and crops was greater than one. This study generally concludes that although the content of heavy metals did not reach toxic level, extensive use of untreated wastewater drawn from the Koshk River has obviously increased the contamination of Ni and Pb in soils and Cd in some vegetables cultivated along the canal, causing potential health risk in the long-term scense for consumers or local residents.     

Speciation of heavy metals in airborne particles, road dusts, and soils along expressways in China

This study analyzed the concentrations and chemical forms of Zn,Cu,Pb,Sb,Cd and Mn in airborne particles,road dusts and soils collected along three expressways in Jiangxi Province,China,with different traffic densities,and identified the levels and sources of heavy metal contamination.The concentrations of Zn,Cu,Pb,Sb,and Cd except Mn in airborne particles,road dusts and soils were all in direct proportion to traffic volume.Cd concentrations were low compared with other metals.For instance,the concentrations of Zn,Cu,Pb,Sb,Mn and Cd were 6.6,0.7,2.2,0.1,0.1 and 0.1μg·m-3in PM10along the Changjiu Expressway,792.8,241.4,248.3,9.6,340.5and 8.0 mg·kg-1in road dusts,and 201.1,143.2,59.5,9.5,338.9 and 2.3 mg·kg-1in soils,respectively,but in the case of the ratio of concentration to the environmental background value,most serious contamination was caused by Cd.The sources of the heavy metals were judged by comparisons of the chemical forms of the heavy metals in different environmental media.Pb and Mn in airborne particles were both derived from traffic;Pb in road dusts and soils resulted mainly from the use of leaded gasoline in the past;and Mn in road dusts and soils was derived from parent rocks.Zn,Cu,Sb and Cd in airborne particles,road dusts and soils were derived primarily from traffic,and differences in chemical forms of the heavy metals in different media were due to the interaction between heavy metals in airborne particles and organic matter and other surfaces in road dusts and soils.We also discussed the change of chemical forms of heavy metals in particles of different sizes and under different weather conditions.Bioavailability of heavy metals in airborne particles was much higher than that in road dusts and soils,especially Pb(0.676 in airborne particles,0.159 in road dusts and 0.095 in soils).     

Assessment of heavy metals contamination in soils of Dexing region, Jiangxi Province, China

Heavy metal contamination has attracted huge concern due to its toxicity, abundance and persistence in the environment, and subsequent accumulation in soil, sediment and water. Mining is one of the most important sources of heavy metals in the environment. Mining-milling operations and disposal of tailings （the finely ground remains of milled ores） in addition to smelting and metal refining provide significant sources of pollution. Mining and mineral processing in the Dexing region of China have been carried out for over forty years and have contaminated the soils with heavy metals, Many studies were conducted to assess and establish the extent of heavy metal contamination in the soils due to mining. The aim of this work was to assess the environmental impact of mining on soils in the Dexing region and to identify the main factors involved in heavy metals dispersion. A 4800 km^2 study area was assessed with respect to its heavy metals on the basis of the current guideline values. In order to assess the extent of heavy metals contamination resulting from past mining activities in the Dexing region, 919 soil samples were collected and analyzed for As, Hg, Cd, Cr, Zn, Cu and Pb, Heavy metals levels were determined using inductively couple plasma-atomic emission spectrometry and X-ray fluorescence spectrometry. Results of soil samples reported concentrations between 1.790-899 mg/kg for As, 0.034-4.980 mg/kg for Hg, 0.043-8.330 mg/kg for Cd, 10-666 mg/kg for Cr, 25-18500 mg/kg for Zn, 6-1825 mg/kg for Cu, and 16-1312 mg/kg for Pb, respectively. The maximum values of As, Hg, Cd, Cr, Zn, Cu and Pb concentration in soils were up to 60, 33, 41, 7, 185, 52 and 37 times higher than the tolerable level, respectively. Meanwhile, the single-factor pollution index and Nemerow pollution index were used to assess the environment quality of heavy metals contamination.     

Environmental investigation for causality and remediation of cadmium contaminated soils in Tak Province, Thailand

Highly elevated cadmium concentrations in paddy soil in the Mae Sod District, Tak Province, Thailand, was detected and widely reported in 2003. This emergence provoked public interest and demands for responsibility and remedial actions. As zinc mines and concentrator were located in the upstream area, mining activities were proclaimed a contamination source. Department of Primary Industries and Mines （DPIM）, a governmental organization responsible for mining and mineral processing, was thus challenged to verify the reliability of post monitoring data displaying consistently low heavy metal concentrations in compliance with the standard limits for over 15 years. Detailed survey and deep-going research on the causes, boundary and severity of cadmium contamination as well as the environmental impact alleviation were consequently conducted. Environmental samples were accumulated systematically for 2 years throughout the areas of upstream and downstream mining sites. A total of 259 soil samples from 53 spots at the depths of 0-20, 20-40, 40-60 and 60-200 cm were drilled with hand auger. Samples of water, stream sediment and mine tailing were also collected. Chemical analysis for cadmium （Cd）, zinc （Zn） and lead （Pb） concentrations with AAS and ICP were undertaken. The contaminated area was finally defined to spread over approximately 18 square kilometer mainly of mountainous mineralizing land and colluvium.