Overview of trace metal contamination in the Scheldt estuary and effect of regulatory measures

Seasonally, dissolved and particulate metal concentrations in the Scheldt estuary were assessed over a period of 4 years (1995–1998). High quality data were obtained following stringent analytical protocols for each step: sampling, sample treatment, sample storage and analysis. Of the 5 trace metals, Ni showed the most conservative behaviour, while Cd and Cu were clearly transferred from the particulate to the dissolved phase in the middle estuary. A substantial part of the particulate metals entering the estuarine system are lost through sedimentation. General seasonal patterns are the following: lower concentrations in spring and higher ones in winter (sometimes late fall/early winter) for dissolved metals, while in summer a pronounced rise of the longitudinal concentration profile is observed for the particulate metals. A comparison of the trace metal concentrations (dissolved and particulate) at the mouth of the estuary in 1995–1998 with those from 1981 to 1983, reveal reductions between 30 and 58%. Reductions based on direct emission measurements for almost the same period suggest reductions (dissolved + particulate) between 42 and 64%. Biomagnification (BMF) is the accumulation of a compound through the food-chain. It is in our case expressed as the ratio of the metal concentration in the organism (g g^–1, d.w.)/the metal concentration in total suspended matter (g g^–1, d.w.). Almost all BMF-values of Periwinkle, Nereis diversicolor and Macoma balthica (3 bottom organisms in the Scheldt estuary) are negative meaning that these organisms contain less heavy metals than the particulate suspended matter. For all organisms log BMFs for Pb, respectively Ni, are around –1.8, respectively –0.7. For Cd, Periwinkle shows slight enrichment (0.05) and for Cu even more (0.45), while negative values were observed for Nereis diversicolour and Macoma balthica. The latter organisms are more enriched in Zn (–0.09) than Periwinkle (–0.43).     

Trace elements in the Upper Fly River, Papua New Guinea

SUMMARY. Measurements were made of calcium, magnesium and eight trace elements (Cu, Zn, Fe, Mn, Ni, Pb, Cd, Co) in waters, sediment and biota at eight sites in the Upper Fly River, Papua New Guinea. Determinations from streams draining an area rich in copper ore showed relatively low values for soluble copper and this was attributed to the small amount of ore exposed to weathering, heavy rainfall and high pH of water associated with the limestone bedrock. More iron was transported in a soluble form down a headwater tributary (Alice River) than in the Fly River but higher iron concentrations were associated with particulate matter in the Fly than in the Alice. The geochemistry of the catchment and the distance from the headwaters were important influences on the amount of particulate iron and its distribution between soluble and particulate forms.
Levels of metals in the biota generally reflected the background concentrations of metals encountered at each site. Concentrations of Cu, Cd, and Zn were lower in starved invertebrates compared with unstarved individuals but no consistent changes were observed in Fe or Mn content.     

Biogeochemical behaviour of Cd, Cu, Pb and Zn in the Scheldt estuary during the period 1981–1983

Cu, Zn, Cd and Pb have been analysed in suspendedmatter and water samples from the Scheldt estuary,collected during five cruises between May 1982 and May1983. In order to evaluate the overall metal behaviourin the estuary, continuous longitudinal profiles ofthe total, the particulate and the dissolved metalconcentrations are discussed in relation to variousspecific physico-chemical parameters. By means ofcorrelation and multi-regression techniques, severalestuarine processes could be identified which dominateand/or control the behaviour of the individual tracemetals in three distinct areas of the Scheldt estuary. The behaviour of the four selected metals was foundto show some common features, but is besides this alsocharacterised by many individual and specificproperties. The total metal concentrations seem toco-vary well with the turbidity in the maximumturbidity zone between salinities 2 and 10 psu. In thedownstream area a dilution profile is observed for thetotal metal concentrations of Cu and Cd as well as forthe dissolved concentrations of all metals. Dissolved metal production rates are high for Cu andCd, but much lower for Zn and Pb, confirming thedifferent longitudinal dissolved metal profiles. ForCu and Cd these dissolved metal profiles arecharacterised by a broad mobilisation area, coveringthe whole middle estuary. Pb on the other hand, showsa more confined mobilisation area, and for Zn no sucharea was found. During winter the dissolved metalproduction rates seem to be controlled, predominantly,by desorption processes. During summer dissolved metalproduction is correlated mainly to the dissolvedoxygen content, suggesting the domination of redoxprocesses solely or in combination with desorptionprocesses. In some cases, co-existent with nearly zerooxygen concentrations, removal of dissolved metals wasobserved, possibly reflecting precipitation reactions. Longitudinal particulate metal profiles all show anegative deviation versus the dilution profile. Cu andCd provide the higher deviations, characterised by anarrow enrichment zone preceding a broad mobilisationarea. Finally, all particulate metal profiles appearedto correlate well with POC, when expressed involumetric units. This revised version was published online in July 2006 with corrections to the Cover Date.     

调水调沙工程黄河口近岸沉积物重金属和砷含量的空间分布及其生态风险评估

为了明确调水调沙工程长期影响下黄河口近岸沉积物中重金属含量的分布特征及其生态风险,基于2012年黄河口近岸27个站位的表层沉积物样品,通过ICP-MS测定重金属(Zn、Cr、Ni、Pb、Cu、Cd)和砷(As)含量,并运用潜在生态风险指数法(RI)对其进行生态风险评估。结果表明:近岸沉积物中重金属和As的平均含量表现为AsZnCrNiPbCuCd。Cr、Ni、Cu和Pb四种元素的分布规律较为一致,整体呈现出近岸和近黄河口高而远离河口和岸线低的空间分异特征。Ni、Cu、Pb、Zn与粘土均呈极显著或显著正相关(P0.01或P0.05),而Cd、Cr和As与其相关性均未达到显著水平(P0.05)。近岸沉积物中6种重金属和As的平均单项潜在生态风险指数大小顺序整体表现为CdAsNiPbCuCrZn。就潜在生态风险(RI)而言,研究区域18.52%的站位属轻微生态危害,70.07%的站位属中等生态危害,7.41%的站位属强生态危害,Cd和As是造成危害的两种主要元素。近岸沉积物中重金属和As的来源复杂且多样,主要是由于农业化肥使用、海上石油开采和泄漏、化石燃料燃烧以及河口污染物输入所致。对比研究发现,随着调水调沙工程的长期实施,除Cd和As外沉积物中其他重金属含量均呈下降趋势,说明二者的生态风险将会随调水调沙的长期实施呈增加趋势,而其他重金属的生态风险将呈降低趋势,故未来应重点关注近岸沉积物中Cd和As的生态毒理风险。     

Analysis of Spatial Variations and Sources of Heavy Metals in Farmland Soils of Beijing Suburbs

To understand the effect of intense human activities in suburbs on environmental quality, we obtained 758 measurements of the heavy metals in certain farmland soils of the Beijing suburbs. Multivariate statistical analysis and geostatistical analysis were used to conduct a basic analysis of the heavy metal concentrations, the distribution characteristics and the sources of pollution of the farmland soils in these suburbs. The results showed the presence of eight heavy metals in the agricultural soils at levels exceeding the background values for As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. In particular, all the measured Cr concentrations exceeded the background value, while As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were present at 1.13, 1.68, 1.95, 1.43, 1.63, 0.79, 0.92 and 1.36 times their background values, respectively. The results of correlation, factor and spatial structure analyses showed that Cd, Cu, Pb and Zn were strongly homologous, whereas Cr and Hg showed a degree of heterogeneity. The analysis further indicated that in addition to natural factors, Cd, Cu, Pb and Zn in the soil were mainly associated with distribution from road traffic and land use status. Different agricultural production measures in the various areas were also important factors that affected the spatial distribution of the soil Cr concentration. The major sources of Hg pollution were landfills for industrial waste and urban domestic garbage, while the spatial distribution of As was more likely to be a result of composite pollution. The regional distribution of the heavy metals indicated that except for Cr and Hg, the high heavy metal levels occurred in districts and counties with higher organic matter concentrations, such as the northwestern and southeastern suburbs of Beijing. There was no significant Ni pollution in the agricultural soils of the Beijing suburbs.     

Particle sources and trace element reactivity in the Humber plume

Samples of suspended particulate matter (SPM) collected from the Humber Estuary had higher concentrations of particulate metals than SPM from Holderness coastal waters (U.K.). Characterised SPM from both sources was used in laboratory experiments involving the uptake of radiotracer¹⁰⁹Cd,¹³⁷Cs,⁵⁴Mn and⁶⁵Zn. Kinetic experiments, over five days, showed that the rate and extent of uptake was highly dependent on particle type, with¹⁰⁹Cd,⁵⁴Mn and⁶⁵Zn being more reactive with Humber Estuary particles than those from Holderness and¹³⁷Cs having the opposite trend. Adsorption experiments were also carried out on suspensions in which SPM from the Humber Estuary and Holderness coastal water were mixed in various proportions. These experiments revealed that K_d for⁶⁵Zn increased linearly with the proportion of Humber SPM, K_d for¹³⁷Cs decreased linearly with increase in Humber SPM and K_d for⁵⁴Mn and¹⁰⁹Cd displayed non-linear behaviour. The results of the study were used to develop an algorithm for predicting the partition coefficients in the Humber Plume based on the extent of particle mixing from the two source regions. The use of^206/207Pb ratios in determining the extent of particle mixing is discussed, along with the application of the algorithm to the modelling of particulate trace metal behaviour in the Humber-Wash coastal zone.     

Assessment on Pollution by Heavy Metals and Arsenic Based on Surficial and Core Sediments in the Cam River Mouth,Haiphong Province,Vietnam

The Cam River mouth (Haiphong Province) is one of the main river mouths of the Red River System, which is one of the most important water resources in Northern Vietnam. Over the past 50 years, the strong socio-economic development in the area has caused a considerable contamination with heavy metals (Co, Cr, Cu, Mn, Ni, Pb, and Zn) and arsenic. In this study, the vertical and horizontal distributions of heavy metals and arsenic in sediments from the Cam River mouth were investigated. In addition, the history, origin, and degree of contamination were assessed. Normalized (with respect to Al) heavy metal and arsenic concentrations in sediment cores and absolute dates obtained from the ¹³⁷Cs analysis were used to reconstruct the pollution history of the river mouth. As, Cu, Mn, Pb, and Zn concentrations increase rapidly by approximately two times or more from 1954 to 1975, and then remain nearly unchanged from 1975 until 2008, whereas Co, Cr, and Ni concentrations slightly increase from 1954 until 2008. In addition, background values for heavy metals and arsenic have also been determined with regard to the period before 1954. In the study area, Co, Cr, Cu, Ni, Mn, and Zn are evaluated as minorly enriched, whereas As and Pb are classified as moderately enriched. Generally, the anthropogenic activities in the Haiphong harbor and industrial zone locally contribute to the contamination by heavy metals and arsenic in the Cam River mouth.     

淮南矿区大气及二球悬铃木叶片中重金属含量及其相关性分析

对淮南市污染区(矿区)和对照区(相对清洁区)空气中TSP、PM10-100、PM5-10、PM2.5-5和PM2.5的日均质量浓度进行了测定,并对TSP中Cd、Cr、Cu、Ni、Pb和Zn的质量浓度和二球悬铃木〔Platanus×acerifolia(Ait.)Willd.〕叶片中Cd、Cr、Cu、Ni、Pb和Zn含量的动态变化进行了分析,同时对二球悬铃木叶片中重金属含量与TSP中重金属质量浓度和各类空气颗粒物日均质量浓度的相关性进行了分析。结果表明:在60 d采样期内,空气颗粒物日均质量浓度和叶片中重金属含量均呈波动的变化趋势,其中污染区空气中TSP和PM2.5的日均质量浓度均显著高于对照区,污染区PM10-100、PM5-10和PM2.5-5日均质量浓度总体上低于对照区;污染区空气TSP中6种重金属元素的质量浓度均高于对照区,污染区二球悬铃木叶片中的Cd、Cr、Cu、Ni和Zn含量均高于对照区但Pb含量低于对照区。相关性分析结果表明:污染区二球悬铃木叶片中重金属含量与空气TSP中重金属质量浓度多数呈正相关,叶片中重金属含量与空气中PM2.5日均质量浓度也均呈正相关,其中叶片中Cd含量与PM2.5日均质量浓度的相关性达显著水平。研究结果表明:在淮南矿区,可将二球悬铃木叶片中的重金属含量作为空气PM2.5污染状况的监测指标。     

Particulate phosphorus in the Humber estuary

The biogeochemical controls on particulate phosphorus distribution in the Humber estuary have been investigated with regard to salinity and season. Surveys of the Humber were conducted in August 1991 and January, March and June 1992. Samples were collected for particulate phosphorus, dissolved phosphorus, suspended load and salinity analysis. Particulate phosphorus forms 16 to 93% of the total phosphorus present in the water column of the Humber estuary. Total particulate phosphorus concentrations in the Humber ranged from 1 to 45 μmol l⁻¹. This range is comparable to that observed in similar sized industrialized estuaries of the U.S.A. and northern Europe. Flocculation at low salinities was found to be a major influence on particulate phosphorus concentrations. Highest concentrations of particulate phosphorus were found in reaches below a salinity of 5 and may result in phosphorus being trapped in the sediments of the estuary. There is evidence that this phosphorus may be released as oxygen concentrations decrease during the summer. Suspended load, adsorption/desorption equilibrium and external inputs were also found to influence the particulate phosphorus concentrations.     

Temporal and spatial variation on heavy metal concentrations in the oyster Ostrea equestris on the northern coast of Rio De Janeiro State, Brazil.

Heavy metal (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) concentrations were determined by ICP-AES in Ostrea equestris from three beaches (Barra do Furado, Buena, and Ponta do Retiro) on the northern coast of Rio de Janeiro State. The average concentration was 0.8 +/- 0.18, 0.4 +/- 0.21, 58 +/- 25.6, 249 +/- 52.3, 11 +/- 1.31, 0.55 +/- 0.16, 0.13 +/- 0.11, and 1131 +/- 321 microg x g(-1) dry weight for Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn respectively. Significant spatial variation (p < 0.05) between the samples areas occurred for Cr, Pb, and Zn with higher values in Barra do Furado; and for Cu in Ponta do Retiro. Significant temporal variations (p < 0.05) were observed for all metals except Cu. Temporal variability may be related to changes in the inputs of metals associated with suspended particles. Concentrations were similar to those found in areas under low pollution impact, except for Zn, the high concentrations of which probably reflect the physiological characteristics of these organisms.     

Bioaccumulation of heavy metals in Dactylis glomerata L. growing in a calcareous soil amended with sewage sludge

The total and DTPA-extractable concentrations of Pb, Ni, Zn, Cu, Cr and Cd were measured in a calcareous soil amended with different doses of sewage sludge under field conditions. The same metals were also measured in the roots and leaves of Dactylis glomerata at the end of the first vegetative period after the sludge was added. The root concentrations of all the metals were unrelated to their concentrations in the soil. Leaf concentrations of Zn and Cr correlated with total (Zn) and DTPA-extractable (Zn and Cr) concentrations in the soil. DTPA extraction did not appear to be very useful for evaluating the bioavailability of metals in this kind of soil as it gave very low correlation coefficients with leaf content (r = 0.684, P = 0.0049 for Zn and r = 0.557, P = 0.0249 for Cr). Concentrations of Pb, Ni, Cu, and Cd in roots and leaves of Dactylis glomerata were unrelated to the total or DTPA-extractable concentrations in the sludge-amended soil.     

Dissolved and particulate trace metal geochemistry in the scheldt estuary,S. W. Netherlands (water column and sediments)

The geochemistry of dissolved and particulate trace metals has been studied in the water column and the sediments of the Scheldt estuary between 1987 and 1990. A strong seasonal influence on the behaviour of dissolved Cd, Cu and Zn is observed, related to the redox conditions in the upper estuary and phytoplankton activity in the lower estuary (which are both seasonally dependent variables). The dissolved trace metal concentrations in the fresh water end-member are remarkably low during spring and summer, due to metal sulphide precipitation in the anoxic Scheldt river. However, the dissolved concentrations increase rapidly with increasing salinity, due to oxidation of metal sulphides that are present in the suspended matter, accompanied by (e.g. chloro-)complexation of the released metals. Readsorption of Cd and Zn occurs in the lower estuary during the spring phytoplankton bloom. During winter, when the Scheldt river is not completely anoxic, much higher dissolved trace metal concentrations are observed in the fresh water end-member since metal sulphide precipitation in the water column is precluded. Rapid trace metal removal is observed in the low salinity, high turbidity zone, due to adsorption onto suspended matter and freshly precipitated iron and manganese oxyhydroxides. Upon further mixing, desorption is apparent, due to a similar oxidation-complexation mechanism as observed during spring and summer. Pore water infusion may also contribute to the enrichment of dissolved Cd, Cu and Zn in the mid-estuarine region. The trace metal contents of the suspended matter and the sediments show a continuous decrease with increasing salinity. This behaviour is to a very large extent due to physical mixing of contaminated fluvial particulates and relatively unpolluted marine particulates. Desorption of Cd, Cu and Zn can be identified but is of minor importance compared to the conservative mixing process. The distribution of dissolved Cd, Cu and Zn in the pore waters of the mid-estuarine region reflects the impact of early diagenetic processes. Trace metal peaks are observed near the sediment-water interface, and at greater depth in the manganese and iron reduction zones. These peaks are attributed to oxidation of reduced trace metal compounds (e.g. sulphides) and reduction of the (iron and manganese) oxide carrier phases, respectively. At greater depth, the dissolved trace metal concentrations are much lower due to metal sulphide precipitation in the sulphate reduction zone. Analysis of a large sediment dataset indicates severe trace metal pollution of the Scheldt estuary at the end of the fifties. A major reduction of the pollution by As, Cr, Hg, Pb, and Zn has occurred in the seventies, and of Cd and Cu in the eighties. The Ni pollution has increased over the time period considered. In spite of this improvement, the present-day pollution status of the Scheldt estuary is still reason for concern.     

Contamination and environmental risk assessment of heavy metals in marine sediments from Tahaddart estuary (NW of Morocco)

Abstract

The distribution, contamination status, and ecological risks of heavy metals in Tahaddart estuary were investigated. 24 surface sediment samples and two cores were collected and analyzed for major (Al and Fe), heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn), and grain size composition. The heavy metals assessment was carried out using different environmental indices. The results indicated that the spatial distribution patterns of Al, Fe, and Zn were mainly determined by the distribution of the finer grained fraction (<63?μm) in the sediment. In contrast, As, Cd, Cr, Cu, Ni, and Pb concentrations were controlled by anthropogenic activities (vehicular traffic from Highway Bridge and thermal power plant). The distribution of heavy metals in sediment cores showed an upward enrichment in heavy metals with high concentration found in the uppermost may related to the increasing in human activities. The pollution indexes confirmed that the Tahaddart estuary sediment was considerably to high contaminated by heavy metals near to different anthropogenic inputs. Similarly, the potential ecological risk index and the biological risk index present 21% probability of toxicity posing potential risk to the aquatic organisms. These results provide basic information that can be used to protect and improve the quality of this ecosystem.     

Roadside Topsoil Concentrations of Lead and Other Heavy Metals in Ibadan,Nigeria

Concentrations of Pb, Zn, Cd, Cu, Cr, Co, and Ni were determined in roadside topsoil collected from locations of varied vehicular traffic densities in the city of Ibadan, Nigeria, with a view to determining the level of contamination and the contribution of traffic density. Levels of Pb, Zn, Cd, and Cu were elevated above background concentrations measured in control areas. Average values (ppm) for all sample locations were Pb — 81±140; Zn — 48±37; Cd — 0.55±0.49; Cu — 17±17; Cr — 22.1±9.6; Co — 7.9±3.8; Ni — 10.5±9.7. Factors of accumulation of metals in roadsides relative to control sites were highest for Pb. Vehicular traffic was not an important source of chromium, cobalt and nickel, for which roadside concentrations were about those of the control sites. Metal concentrations were poorly correlated with traffic volumes. An average of about 60% of total soil concentration of the metals were determined to be held in bioavailable geochemical phases, of which the highest concentrations were mostly held in either the reducible or oxidizable phase. Levels of the metals in the topsoil were generally lower than the soil quality criteria of some developed countries.     

Integrated assessment of heavy metal contamination in sediments from a coastal industrial basin, NE China

The purpose of this study is to investigate the current status of metal pollution of the sediments from urban-stream, estuary and Jinzhou Bay of the coastal industrial city, NE China. Forty surface sediment samples from river, estuary and bay and one sediment core from Jinzhou bay were collected and analyzed for heavy metal concentrations of Cu, Zn, Pb, Cd, Ni and Mn. The data reveals that there was a remarkable change in the contents of heavy metals among the sampling sediments, and all the mean values of heavy metal concentration were higher than the national guideline values of marine sediment quality of China (GB 18668-2002). This is one of the most polluted of the world's impacted coastal systems. Both the correlation analyses and geostatistical analyses showed that Cu, Zn, Pb and Cd have a very similar spatial pattern and come from the industrial activities, and the concentration of Mn mainly caused by natural factors. The estuary is the most polluted area with extremely high potential ecological risk; however the contamination decreased with distance seaward of the river estuary. This study clearly highlights the urgent need to make great efforts to control the industrial emission and the exceptionally severe heavy metal pollution in the coastal area, and the immediate measures should be carried out to minimize the rate of contamination, and extent of future pollution problems.     

Sources,distribution and temporal variability of trace metals in the Thames Estuary

Water and intertidal sediment samples were collected from 28 stations along the Thames Estuary, from the tidal limit to the outer estuary. Surveys were conducted in 1997, 1999 and 2001 to assess spatial distributions and short-term variability. Highest concentrations of trace metals in water coincided with high turbidity in the mid-estuarine region, although the particle-associated fraction varied from 22% (As) to 95% (Pb). Theoretical dilution line (TDL) plots showed that dissolved metals were largely derived from a combination of diffuse (sediment desorption) and localised point sources (outfalls, industry). Dissolved Cu and Zn both exceeded environmental quality standard (EQS) levels during the survey period. The majority of sediment metals showed common distributional patterns, with increasing concentrations upstream. This increase was greatest for pollutant metals: Ag, Cd, Cu, Hg, Pb and Zn. Partial extraction of sediment metals with 1 M HCl showed that >50% of Ag, Cd, Cu, Mn, Pb and Zn were potentially bioavailable and that the proportion of bioavailable sediment metals also increased upstream. The majority of sediment metal concentrations exceeded Interim Sediment Quality Guideline threshold effects levels (TELs) over much of the estuary. Sediment concentrations of Cu, Hg, Pb and Zn also exceeded probable effects levels (PELs) at many estuarine sites. Despite improvements in recent years, the Thames Estuary remains chronically contaminated with a range of metals.     

Spatial variability characteristics and environmental effects of heavy metals in surface riparian soils and surface sediments of Qinggeda Lake

Abstract

One hundred and twenty topsoil (0–20?cm layer) samples and 45 surface sediment samples were collected from the riparian area and bottom of Qinggeda Lake. The content of Pb, Cu, Cr, Ni, Zn, Mn, V, and As were determined to reveal the distribution characteristics and explore the spatial dependency relationship between environmental factors (pH, conductivity, and organic matter) and heavy metals using Kriging interpolation and the geographical weighted regression model. Results showed as follows: (1) The average contents of Pb, Cu, Cr, Ni, Zn, V, and As did not exceed the Standard of National Soil Environmental Quality. However, Cu, Cr, and V were higher than the Xinjiang soil background. (2) The target elements in the surface sediments of the lake showed a decreasing trend from the center of the lake to the shore. Also, the heavy metal concentrations in the eastern part of the lake shore were significantly higher than those in other areas, and the highest concentrations appeared in the paddy field. (3) The effects of the eight heavy metals on pH, conductivity, and organic matter displayed significant spatial nonstationary characteristics. Cr, As, Cu, and Zn are the primary factors that affect environmental characteristics such as pH, conductivity, and organic matter content.     

Attached and Free Bacteria in an Estuary with Abundant Suspended Solids

Concentrations and glucose mineralization potentials ( V _max) of attached and free bacteria in waters from the Humber estuary were determined. The waters had high concentrations of suspended solids. Most bacteria were attached to suspended solids and V _max of attached bacteria was greater than that of free bacteria. These observations suggest that breakdown of organic matter is carried out mainly by attached bacteria. Examination of samples from other estuaries which contained less suspended solids than the Humber suggested that in these estuaries free bacteria might be more abundant than attached bacteria.     

Spatial distribution and human health risk assessment of heavy metals in campus dust: A case study of the university town of Huaxi

Abstract

A detailed investigation was conducted to understand the contamination characteristics of a selected set of heavy metals (HMs) in 34 campus dust samples from Huaxi University Town. The HMs spatial distribution analysis based on ArcGIS software, the geo-accumulation index (I_geo) and health risk model were employed for evaluation, and multivariate statistical methods were used to identify possible sources. Results showed that the mean concentrations of Cu, Zn, Pb, Cr, Ni, and Cd were 68.18, 123.81, 45.26, 140.36, 47.26, and 0.47?mg/kg, respectively. The spatial distribution characteristics displayed that the relatively large concentrations for the analyzed HMs were mainly located at both teaching areas and students’ dormitory areas. The average values of I_geo indicated that HMs contamination level followed the decreasing trend of Cd?>?Cu?>?Cr?>?Pb?>?Ni?>?Zn. The health risk assessment results indicated that HMs in campus dust generally do not pose any immediate health risk for both adult males and adult females but the cumulative effect is a matter of concern. The sources analyses demonstrated that Cu, Zn, Cr, and Cd, primarily from motor vehicle emission and waste incineration, Pb predominantly originated from construction source, while Ni had the mixed sources of nature and traffic.     

Mobility and Translocation of Heavy Metals from Mine Tailings in Three Plant Species after Amendment with Compost and Biosurfactant

An experiment was performed to determine the effects of mine tailings alone mixed with compost or with compost plus crude biosurfactant on the accumulation of heavy metals (Pb, Zn, Cu, Cr, Cd, and Ni) in Acacia retinodes, Nicotiana glauca, and Echinochloa polystachya. The plants were grown in soil, mine tailings, and mine tailings containing compost over a period of seven and five months for shrubs or grass, respectively. The plants Acacia retinodes and Nicotiana glauca grown in mine tailings containing compost showed increases in dry biomass (from 62 to 79%) compared with plants in only tailings. Heavy metals accumulated in the roots and leaves showed high translocation rates of Cr in N. glauca, Cd in A. retinodes, and Ni in E. polystachya. Concentrations of heavy metals in the three plants irrigated with crude biosurfactant were not significantly different from those irrigated with water. Zn and Cd fractions within mine tailings containing compost were bound to carbonate, Pb was bound to residues, and Cu was bound to Fe-oxides. Cd had the highest mobility factor followed in order by Zn, Pb, and Cu. The elevated concentrations of Pb in roots and the low translocation rate for N. glauca and A. retinodes indicate that they are suitable for phytostabilizing Pb and Zn.