The use of lichen (Cetraria nivalis) and moss (Rhacomitrium lanuginosum) as monitors for atmospheric deposition in Greenland

Concentrations of Pb, Cd, Hg, Zn, Cu, Cr, Ni, As, V, Al and Fe are reported from soil, humus, moss (Rhacomitrium lanuginosum) and lichen (Cetraria nivalis) sampled at four locations in Greenland. For Al, Fe, Cr and V the levels in soil were highest followed by humus and R. lanuginosum and with the lowest levels in C. nivalis. The same was true for Pb, Cu and Ni but without as great a difference between medias. For Cd and Hg, the lowest levels were found in soil. For Zn and As, the media with highest levels differed between locality. Data were examined by a principal component analysis. Three principal components explained 87% of the total variation. The dominant elements in the first component were Fe, Al, V, Ni, Cr, Cu and Pb. This component is interpreted as a soil dust factor. The concentrations in R. lanuginosum and C. nivalis of these elements are believed to be highly influenced by soil dust. Pb concentrations in moss and lichen may also be influenced by other sources as Pb also had some correlation's with the third component. Zn and Cd and to a lesser extent. As were the dominant elements in the second component. The third component was highly dominated by Hg with a lesser influence of Pb and As, Zn, Cd and Hg concentrations in R. lanuginosum and C. nivalis are believed to be influenced by other sources than soil dust which may be long-range atmospheric transport. In general, both the within locality and the between locality variability in the values of the three components decreased in the order soil, humus, R. lanuginosum and C. nivalis. The lichen C. nivalis is looked at as an indicator with greater potential for monitoring atmospheric deposition of elements than the moss R. lanuginosum.     

Historical perspective of heavy metals contamination (Cd, Cr, Cu, Hg, Pb, Zn) in the Seine River basin (France) following a DPSIR approach (1950-2005)

The Driver-Pressures-State-Impact-Response approach is applied to heavy metals in the Seine River catchment (65,000 km(2); 14 million people of which 10 million are aggregated within Paris megacity; 30% of French industrial and agricultural production). The contamination pattern at river mouth is established on the particulate material at different time scales: 1930-2000 for floodplain cores, 1980-2003 for suspended particulate matter (SPM) and bed-sediments, 1994-2003 for atmospheric fallout and annual flood deposits. The Seine has been among the most contaminated catchments with maximum contents recorded at 130 mg kg(-1) for Cd, 24 for Hg, 558 for Pb, 1620 for Zn, 347 for Cu, 275 for Cr and 150 for Ni. Today, the average levels for Cd (1.8 mg kg(-1)), Hg (1.08), Pb (108), Zn (370), Cu (99), Cr (123) and Ni (31) are much lower but still in the upper 90% of the global scale distribution (Cr and Ni excepted) and well above the natural background values determined on pre-historical deposits. All metal contents have decreased at least since 1955/65, well before metal emission regulations that started in the mid 1970's and the metal monitoring in the catchment that started in the early 1980's. In the last 20 y, major criteria changes for the management of contaminated particulates (treated urban sludge, agricultural soils, dredged sediments) have occurred. In the mid 1990's, there was a complete shift in the contamination assessment scales, from sediment management and water usage criteria to the good ecological state, now required by the 2000 European Directive. When comparing excess metal outputs, associated to river SPM, to the average metal demand within the catchment from 1950 to 2000, the leakage ratios decrease exponentially from 1950 to 2000 for Cd, Cr, Cu, Pb and Zn, meanwhile, a general increase of the demand is observed: the rate of recycling and/or treatment of metals within the anthroposphere has been improved ten-fold. Hg environmental trajectory is very specific: there is a marked decontamination from 1970 to 2000, but the leakage ratio remains very high (10 to 20%) during this period. Drivers and Pressures are poorly known prior to 1985; State evolution since 1935 has been reconstructed from flood plain cores analysis; Impacts were maximum between 1950 and 1970 but remained unknown due to analytical limitation and lack of awareness. Some Responses are lagging 10 y behind monitoring and have much evolved in the past 10 y.     

Concentrations of heavy metals and plant nutrients in water, sediments and aquatic macrophytes of anthropogenic lakes (former open cut brown coal mines) differing in stage of acidification.

Concentration of heavy metals (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) as well as macronutrients (N, P, K, Ca, Mg, S) were measured in water, bottom sediments and plants from anthropogenic lakes in West Poland. The collected plants were: Phragmites australis, Potamogeton natans, Iris pseudoacorus, Juncus effusus, Drepanocladus aduncus, Juncus bulbosus, Phalaris arundinacea, Carex remota and Calamagrostis epigeios. Two reference lakes were sampled for Nymphaea alba, Phragmites australis, Schoenoplectus lacustris, Typha angustifolia and Polygonum hydropiper. These plants contained elevated levels of Cd, Co, Cr, Cu and Mn, and part of the plants contained in addition elevated levels of Mn, Fe, Pb, Ni and Zn. Analyses of water indicated pollution with sulfates, Cd, Co, Ni. Zn, Pb and Cu, and bottom sediments indicated that some of the examined lakes were polluted with Cd, Co and Cr. Strong positive correlations were found between concentrations of Co in water and in plants and between Zn in sediments and plants, indicating the potential of plants for pollution monitoring for this metal. Heavy metal accumulation seemed to be directly associated with the exclusion of Ca and Mg.     

Biomonitoring of nine elements by the lichen Xanthoria parietina in Adriatic Italy: a retrospective study over a 7-year time span

The results of long-term biomonitoring of nine elements (Cd, Cr, Ni, Pb, V, Cu, Zn, Fe and Al) with the epiphytic lichen Xanthoria parietina over a seven year time span are reported. A total of 51 sampling stations were monitored in two surveys, obtaining information about heavy metal concentrations in a large area characterized by a high impact of industrial and urban sources of air pollution. The results showed that the approach adopted is indeed a reliable tool to assess environmental alteration, pinpointing not only the trends of the nine elements analysed but also their reciprocal correlations. As a consequence it was possible to characterize changes in air pollution composition and the common origin and behavior of several groups of elements.     

Heavy metals in urban soils: a case study from the city of Palermo (Sicily), Italy

Concentrations of V, Mn, Cd, Zn, Ni, Cr, Co, Cu, Pb, Hg and Sb were measured on 70 topsoil samples collected from green areas and parks in the city of Palermo (Sicily) in order to: (1) assess the distribution of these heavy metals in the urban environment; (2) discriminate natural and anthropic contributions; and (3) identify possible sources of pollution. Mineralogy, physico-chemical parameters, and major element contents of the topsoils were determined to highlight the influence of 'natural' features on the heavy metal concentrations and their distribution. Medians of Pb, Zn, Cu and Hg concentrations of the investigated urban soils are 202, 138, 63 and 0.68 mgkg(-1), respectively. These values are higher, in some case by different orders of size, than those of unpolluted soils in Sicily that average 44, 122, 34 and 0.07 mg kg(-1). An ensemble of basic and multivariate statistical analyses (cluster analysis and principal component analysis) was performed to reduce the multidimensional space of variables and samples, thus defining two sets of heavy metals as tracers of natural and anthropic influences. Results demonstrate that Pb, Zn, Cu, Sb and Hg can be inferred to be tracers of anthropic pollution, whereas Mn, Ni, Co, Cr, V and Cd were interpreted to be mainly inherited from parent materials. Maps of pollutant distribution were constructed for the whole urban area pointing to vehicle traffic as the main source of diffuse pollution and also showing the contribution of point sources of pollution to urban topsoils.     

The assessment of air and soil as contributors of some trace metals to vegetable plants. III. Experiments with field-grown plants

Plants have been grown on common soils at a number of field sites with differing air metal concentrations. Moss bags were co-located with the plants to evaluate atmospheric deposition. Values of the concentration factor (CF) have been estimated (soil-derived metal in plant divided by soil metal concentration) and are generally found to be in the order Zn greater than Cd greater than Ni greater than Cr greater than Pb (sometimes Cd greater than Zn), with values for Pb comparable with earlier studies in which the atmospheric contribution was subtracted. Values of the air accumulation factor (AAF) (air-derived metal in plant divided by air metal concentration) showed values of 15-30 m3g-1 for Cd and Pb for the exposed parts of plants, and lower values for non-exposed parts. Values of both CF and AAF are comparable with those determined in Part I, using a laboratory growth chamber.     

A field survey of metal binding to metallothionein and other cytosolic ligands in liver of eels using an on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS)

The effect of metal exposure on the accumulation and cytosolic speciation of metals in livers of wild populations of European eel with special emphasis on metallothioneins (MT) was studied. Four sampling sites in Flanders showing different degrees of heavy metal contamination were selected for this purpose. An on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS) was used to study the cytosolic speciation of the metals. The distribution of the metals Cd, Cu, Ni, Pb and Zn among cytosolic fractions displayed strong differences. The cytosolic concentration of Cd, Ni and Pb increased proportionally with the total liver levels. However, the cytosolic concentrations of Cu and Zn only increased above a certain liver tissue threshold level. Cd, Cu and Zn, but not Pb and Ni, were largely associated with the MT pool in correspondence with the environmental exposure and liver tissue concentrations. Most of the Pb and Ni and a considerable fraction of Cu and Zn, but not Cd, were associated to High Molecular Weight (HMW) fractions. The relative importance of the Cu and Zn in the HMW fraction decreased with increasing contamination levels while the MT pool became progressively more important. The close relationship between the cytosolic metal load and the total MT levels or the metals bound on the MT pool indicates that the metals, rather than other stress factors, are the major factor determining MT induction.     

Quantities and associations of lead, zinc, cadmium, manganese, chromium, nickel, vanadium, and copper in fresh Mississippi delta alluvium and New Orleans alluvial soils

The topic of this study is the effect of anthropogenic metals on the geochemical quality of urban soils. This is accomplished by comparing the metal contents and associations between two alluvial soils of the lower Mississippi River Delta, freshly deposited alluvial parent materials and alluvial soils collected from a nearby urban environment. Fresh alluvium samples (n = 97) were collected from the Bonnet Carré Spillway. The urban alluvial soil samples (n = 4026) were collected from New Orleans and stratified by census tracts (n = 286). The Spillway samples tend to have less Pb and Zn than generally noted for the baseline of natural soils. Except for Mn and V, Spillway alluvium contains significantly less metal than urban soils. For Spillway samples, the median metal content (in microg g(-1)) is 4.7 Pb, 11.1 Zn, 0.7 Cd, 164 Mn, 0.8 Cr, 3.9 Ni, 3.2 V, and 3.9 Cu. For urban soils, the median metal content (in microg g(-1)) is 120 Pb, 130 Zn, 3.2 Cd, 138 Mn, 2.1 Cr, 9.8 Ni, 3.8 V, and 12.7 Cu. Metal associations also differ between Spillway alluvium and urban alluvial soils. Fresh alluvium correlation coefficients between individual metals vary from 0.87 to 0.99 (P < 10(-13)) except for Cr which ranges from 0.57 to 0.68 (P < 10(-7)). The urban soil correlation coefficients for metals and the index value are 0.40-0.98. In urban soils, Pb, Zn, Cr, and Cu are dominant metals and highly associated, with a correlation coefficient ranging from 0.83 to 0.98 (P < 10(-25)). Their strong association justifies the use of GIS to map the integrated soil metal index (sum of the medians of metals by census tract) of New Orleans. Although also positively correlated (0.40-0.68, P < 10(-10)), Cd, Mn, Ni and V differ in their distribution in the city compared to Pb, Zn, Cr and Cu. Overall, significantly higher metal values occur in the inner city and lower values occur in outlying areas. The human health impact of the mixture of metals is not well understood. This study provides empirical data about the mixture and distribution of metals in New Orleans alluvial soils. Given common technical development, especially of traffic flows in cities, similar patterns of soil metals are expected for all US cities and probably international cities as well. Primary prevention of urban metal accumulations is necessary to enhance and sustain the development of urban culture.     

Concentration and fate of trace metals in Mekong River delta

In the Mekong River delta and its associated coastal zone trace elements concentrations (Cd, Cu, Ni and Pb) were measured in the dissolved phase (DP) during dry (March 1997) and wet (October 1997) seasons. As, Co, Cr, Ni, Pb, and Al were also measured in suspended matter (SM) and total and organic carbon, trace elements (Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn) and macro elements in superficial sediments (S). Trace metal concentrations in DP and SM during the contrasting hydrological conditions were generally found within the range observed for uncontaminated environment. The average DP concentrations (nM) in the river for March and October are: Cd 0.03 and 0.09, Cu 15 and 14, Ni 7.8 and 8.4, Pb 0.51 and 0.50, respectively. In general there is no significant difference between the concentrations observed during dry and wet season. The evolution of the DP trace metal concentration in the surface water within the salinity gradient suggests no noticeable exchange between the particulate and dissolved phase. This result is in good agreement with those observed in most plume structures studied so far. The average concentrations in the SM (microg/g) (March, October) at the river end-member are: As (24; 11), Co (17; 9), Cr (49; 29), Ni (32; 18), Pb (42; 19) and Al (113,000; 67,000), respectively. All trace elements show higher concentrations in March than in October, with an average increase of two times. This is essentially related to grain size effect since smaller particles were supplied during dry season. These differences are not reflected in the mixing zone, which integrates the seasonal variations. The concentration of major elements (C total, C organic, Si, Al, Ca, K, Fe, Mg, Ti), trace elements (Pb, Zn, Cu, Ni, Mn, Cr, Cd, Hg) in superficial sediments, show similar values during the two seasons and does not show any important variation with depth, indicating either a very fast sedimentation rate and/or the absence of any significant contamination.     

Trace metal partitioning in marine sediments and sludges deposited off the coast of Barcelona (Spain)

As part of a study on the environmental impact of the sludges discharged on the littoral platform in front of Barcelona (Spain), marine sediment samples were analysed. Major components were determined and the Tessier sequential extraction procedure was applied to study Cd, Cu, Cr, Ni, Pb and Zn distribution in eleven samples taken at nine sampling sites. From the data it can be inferred that in this type of sediment with high carbonate content, Cd is the most easily extractable metal, followed by Cr, Pb and Zn, and that Cu and Ni are the most retained. The anthropogenic contribution is also evaluated from the total metal contents using the metal content of a relatively non-polluted sediment sample taken from the same area as a baseline.     

The distribution and fixation of trace elements by the Vertisols of Malaga, southern Spain

The response of Vertisols to contamination by heavy metals (As, Cd, Pb, Hg) and micronutrients (Co, Cu, Cr, Ni, V, Zn) in toxic concentrations was studied in a series of experiments undertaken with soil samples from the province of Malaga, in Southern Spain. The soil samples were placed in methacrylate columns, passing through a contaminant solution of selected elements in order to study their distribution and fixation the soil. Systematic sampling and sequential extraction analysis show that the Vertisols behave as a buffer to all elements, except cadmium.     

Variations in heavy metal concentrations in the moss species Abietinella abietina (Hedw.) Fleisch. according to sampling time,within site variability and increase in biomass

Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mo, Ni, Pb, V and Zn were analysed in the moss Abietinella abietina (Hedw.) Fleisch. to estimate atmospheric heavy metal depositions. Samples were taken at five comparable sites within a radius of 25 m four times during the year 2000 (July 3rd, August 3rd, September 7th, October 3rd). The samples were taken by means of a PVC-tube (r=10 cm) and could therefore be related to aboveground growth and aerial deposition. The investigation showed significant differences between the various sampling times for concentrations of all heavy metals in total but not between concentrations of a single metal. For Cu, Hg, Mo, Pb and Zn temporal variation (=variation between the four times of sampling) was larger than spatial variation (=variation of concentrations between sub-samples at a single sampling time). Growth rates of the mosses differed significantly between sampling times, which reflects the low precipitation at the beginning of the season. Biomass increase, dust and precipitation influenced the metal concentrations. The calculation of deposition rates, which takes growth rates into account, showed significant differences between the various sampling times for Al, Cd, Cr, Cu and Ni, which is controversial to the results obtained from concentrations of these elements. Additionally, the calculation of atmospheric deposition rates showed a constant increase of metal depositions throughout the investigated period, which can not be seen by considering the concentrations only.     

Utilization of the seagrass Posidonia oceanica to evaluate the spatial dispersion of metal contamination

Metal concentrations have been measured in blades of the endemic Mediterranean seagrass Posidonia oceanica, along transects from three different contaminant point sources (the former asbestos mine of Canari - Corsica, France; the chemical plant of Solvay/Rosignano - Livorno, Italy; and the industrial harbour of Porto-Torres - Sardinia, Italy). The aim of this study was to evaluate the spatial extent of the impact of these sources in terms of metal contamination. The results showed that metal contamination from the former mine of Canari (cobalt - Co, chromium - Cr and nickel - Ni) extends at least 5 km to the north and south. The impact of this mine, which closed in 1965, seems to be lingering still. Mercury (Hg) contamination in the Livorno location was difficult to evaluate due to the presence of others potential sources of mercury in the area (e.g. industrialized city of Livorno, natural cinnabar deposits, intense tectonic activity of the area). At any rate, mercury concentration decreased strongly with distance from the plant. Lead (Pb) contamination at the Porto-Torres harbour was very low and disappeared with distance from the harbour. However, as the Porto-Torres harbour does not appear as a substantial point source of Pb contamination and because of the ubiquitous characteristic of the Pb element, it is difficult to draw any general conclusions concerning this element. The results presented in this study demonstrated the usefulness of the seagrass P. oceanica as a tool for the evaluation of the spatial extent of metal contaminations from point sources and could, therefore, contribute to on-going efforts to manage coastal environments.     

Metal concentrations in a shallow groundwater aquifer underneath petrochemical complex

Duplicate groundwater samples were collected from 104 monitoring wells (piezometers) from shallow aquifers underneath an industrial city in the Eastern Province of Saudi Arabia. Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V, Zn, Ca, Mg, K, Na, Cl, SO₄, alkalinity, salinity, total dissolved salts, and pH were determined in these samples. Analysis of variance showed significantly (p < 0.05) wide variations in the concentrations of the above parameters. The contour maps of metal concentrations indicated that these variations were related to important landmarks in the study area. The results of correlation analyses suggest that geographical as well as chemical factors may influence metal distribution in the groundwater samples. To investigate the geographical effects, the analytical data were normalized (element/Cl ratios were calculated) for chemical variability. As expected, contour mapping of the ratio data of element/Cl of Na, Ca, Mg, K, SO₄, alkalinity, salinity, total dissolved salts, and Sr vary in a relatively small range and did not show a particular geographical trend. The groundwater sample from the industrial-dust area contained higher ratios between concentrations of Cl and Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn. These observations clearly suggest an extraneous contamination source, probably industrial dust, in the area. Another geographical area where metal (As, Cd, Cu, Mo, Ni, Ti,and V)/Cl ratios were found to be large was in the vicinity of an oil-refinery. Groundwater samples collected from the vicinity of a fertilizer plant and green-belt area contained relatively higher ratios of Al, Cd, Cr, Co, and Ni. The results of this study suggest that leachate from the industrial dust, leakage from the oil refinery and fertilizer plant, and drainage of irrigation water are some of the important pollution sources in the industrial city.     

Heavy metals in the tissues of common dolphins (Delphinus delphis) stranded on the Portuguese coast.

The concentrations of Hg, Sn, Cr, Zn, Ni, Co, Cd, Mn, Fe and Cu were determined in the liver, kidney and muscle of 24 common dolphins stranded on the Portuguese coast between 1995 and 1998. Nitric acid was used to extract the metals from the tissues for analysis by inductively-coupled plasma/atomic emission spectroscopy (ICP/AES). Those metals with relatively higher concentrations included Fe, Zn and Hg, particularly in liver. Other metals including Cr, Ni and Cd tended to show much lower levels, or were even undetected (e.g. Co). Different metals seemed to show different temporal trends, although due to substantial variations of the mean concentrations for each year obtained, such temporal pattern has to be studied further. Total Hg concentration in the kidney, muscle and particularly liver, were higher in females than in males. Total Hg concentrations in all the organs increased with body length of dolphins, whilst those of Zn and Cu in muscle decreased with dolphin length. A strong correlation was found between essential metals Zn and Cu in muscle, possibly resulting from sequestration of these metals by metallothionein. In addition, significant co-associations existed between the same metal (e.g. Hg, Sn and Zn) in different organs.     

Atmospheric heavy metal deposition in Finland during 1985-2000 using mosses as bioindicators

Heavy metal deposition and changes in the deposition patterns were investigated on the basis of surveys carried out in 1985, 1990, 1995 and 2000. The concentrations of 10 elements (Cd, Cr, Cu, Fe, Ni, Pb, Zn and V; and As and Hg since 1995) were determined on moss (Hylocomium splendens, Pleurozium schreberi) samples collected from the same permanent sample plots in each survey. The heavy metal concentrations, apart from those in southernmost Finland and close to a number of major emission sources, were relatively low. The mean concentrations of all the heavy metals decreased during the period covered by the surveys. The metals that showed the strongest decrease in concentration since 1985 were Pb (78%), V (70%) and Cd (67%). The concentrations of the other heavy metals decreased by 16-34%. The concentrations of Cr, Cu and Ni were clearly associated with local emission point sources and changes in emission levels. The concentrations of As and Hg, which were measured for the first time during the 1995 survey, decreased on the average by 26% and 10%, respectively.     

Assessment of nutritional status and trace element contamination of holm oak woodlands through analyses of leaves and surrounding soils

The nutritional status and trace element contamination of holm oak woodlands in Vesuvius National Park were assessed by analyses of Quercus ilex L. leaves and surrounding soils. The concentrations of Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, V and Zn were measured in 1-year-old leaves, and in the soils at 0-5 and 15-20 cm depths. The potentially available concentrations were also measured for the soils. The leaf element concentrations were similar to the Q. ilex chemical fingerprint, thus indicating a good nutritional status and the absence of short-term trace element depositions. Total K and V were more abundant in the deep soil layers than in the surface ones, whereas Cd and Pb showed higher values in the surface soils. This suggests that long-term soil accumulations of Cd and Pb are due to atmospheric input. The soil availabilities of Cd, Pb and Zn were high, and Cr availability was very low. A correlation between the available concentrations in the deep soil layers and leaf concentrations was found only for Zn.     

Patterns of metal bioaccumulation in two filter-feeding macroinvertebrates: Exposure distribution, inter-species differences and variability across developmental stages

This study focused on the metal bioaccumulation of two aquatic insects (Ephoron virgo and Hydropsyche spp.) in order to evaluate the spatial distribution of metals, the interspecific differences between both filter-feeders and the bioaccumulation dynamics during E. virgo development stages. Hg, Cd, Ni, Cr, As, Pb, Cu, Ti, Zn and Mn were quantified in insects and in suspended particulate matter (SPM) sampled downstream and upstream of a chemical plant, where more than 300,000 t of polluted sediments are deposited. Hg concentrations were one order of magnitude higher downstream of the sediment dump, which showed that the Hg pollution originated in the chemical plant. Cd, Ni, Cr, Pb, Ti, Zn and Mn in invertebrates revealed that metal pollution was present upstream in other parts of the river. Interspecific differences were observed for all metals but Mn; significantly higher concentrations were observed in E. virgo over Hydropsyche exocellata, except for Cd, which showed 10-fold higher values. Hg and Cd increased until E. virgo nymphs reached 11 mm and decreased afterwards in late instars when nymphs were about to emerge. Cr, Pb, Ti and Mn decreased along early instars followed by a steady state in late instars. Similar values were obtained for Cu, As and Zn along all instars. Sexual differences between males and females of E. virgo were observed for Cd, Cu and Mn. Hg and Cd persistence was strong across developmental stages since high concentrations were found in eggs and emerging adults. Because the behavior of different metals varied for the two species and during the developmental stages of E. virgo, care should be taken in the interpretation of insect metal concentrations when analyzing the food chain transfer of metals in river ecosystems.     

Removal of metals by chemical treatment of municipal waste water

The reduction of the metal content of waste water by chemical treatment with aluminium sulfate or calcium hydroxide has been studied. p] Pb(II), Cu(II), Cr(III), Hg(II), Cd(II) and As(V) are reduced to low levels by both precipitants. Zn(II), Ni(II) and Co(II) are precipitated only at pH-values ≤ 9·5. The precipitation of Cu(II) and Pb(II) is greatly inhibited by the presence of nitrilotriacetate at pH ≤9.     

Heavy metals in wheat grain: assessment of potential health risk for inhabitants in Kunshan, China

Heavy metals (HMs) may cause deleterious effects on human health due to the ingestion of food grain grown in contaminated soils. Concentrations of HMs (Hg, As, Cr, Cu, Ni, Pb, Zn and Cd) in wheat grains were investigated in different areas of a developed industry city in Southeast China (Kunshan city), and their potential risk to health of inhabitants was estimated. The results showed that concentrations of HMs in the top soil (0-15 cm) were in this order: Zn>Cr>Ni>Pb>Cu>As>Hg>Cd. The Zn, Cr, Ni Cd and Hg concentrations of several soil samples exceeded the permissible limits of China standard. In addition, concentrations of HMs in wheat grain decreased in the order of Zn>Cu>Pb>Cr>Ni>Cd>As>Hg. There were 1, 6 and 10 wheat samples whose Zn, Pb and Cd concentrations were above the permissible limits of China standard, respectively. In relation to non-carcinogenic risks, Hazard Quotient (HQ) of individual metal presented values inside the safe interval. However, health risk due to the added effects of eight HMs was significant for rural children and rural adults, but not for urban adults and urban children. HQ (individual risk) and HI (Hazard Index of aggregate risk) to different inhabitants due to HMs followed the same sequence of: country children>country adults>urban children>urban adults. Amongst the HMs, potential health hazards due to As, Cu, Cd and Pb were great, and that due to Cr was the minimum. It was suggested to pay more attention on the potential added threat of HMs to the health of country inhabitants (both children and adults) through consumption of wheat in Kunshan.