Pb In Topsoil Research Articles

Prevalence rates of neurodegenerative diseases versus human exposures to heavy metals across the United States

Novel means are needed to identify individuals and subpopulations susceptible to and afflicted by neurodegenerative diseases (NDDs). This study aimed to utilize geographic distribution of heavy metal sources and sinks to investigate a potential human health risk of developing NDDs. Known or hypothesized environmental factors driving disease prevalence of Alzheimer's Disease (AD), Parkinson's Disease (PD), and amyotrophic lateral sclerosis (ALS) are heavy metals, including arsenic (As), cadmium (Cd), manganese (Mn) and mercury (Hg). Lead (Pb) has been associated with AD and ALS. Analyzable mediums of human exposure to heavy metals (i.e., toxic metals and metalloids), or proxies thereof, include infant blood, topsoil, sewage sludge, and well water. U.S. concentrations of heavy metals in topsoil, sewage sludge, well water, and infant blood were mapped and compared to prevalence rates of major NDDs. Data from federal and state agencies (i.e., CDC, EPA, and the US Geological Survey) on heavy metal concentrations, age distribution, and NDD prevalence rates were geographically represented and statistically analyzed to quantify possible correlations. Aside from an expected significant association between NDD prevalence and age (p < 0.0001), we found significant associations between the prevalence of the sum of three major NDDs with: Pb in topsoil (p = 0.0433); Cd (p < 0.0001) and Pb (p < 0.0001) in sewage sludge; Pb in infant blood (p < 0.0001). Concentrations in sewage sludge of Cd and Pb were significantly correlated with NDD prevalence rates with an odds ratio of 2.91 (2.04, 4.225 95%CI) and 4.084 (3.14, 5.312 95%CI), respectively. The presence of toxic metals in the U.S. environment in multiple matrices, including sewage sludge, was found to be significantly associated with NDD prevalence. This is the first use of sewage sludge as an environmental proxy matrix to infer risk of developing NDDs.

Status of Sustainable Balance Regulation of Heavy Metals in Agricultural Soils in China: A Comprehensive Review and Meta-Analysis

To control heavy metal pollution effectively, prevention of heavy metal accumulations in agricultural soils should be the priority rather than remediation of heavy metal contamination. In this research, papers which contained input and output fluxes of Cd, As, Cr, Hg, and Pb in topsoil (the plough layer) of agricultural lands in Hunan, Zhejiang, the Yangtze River Delta, Hainan, and China as a whole were explored. Fluxes of heavy metal species were recalculated, and future trends of pollution were predicted. Also, cases regarding the application of technologies to control the input and output of heavy metals were analyzed. Results indicated that atmospheric decomposition was the dominant input source of heavy metals in all study sites except Hainan. The relative contributions of fertilizers, irrigation water, and straw returning fluctuated greatly among different sites. Cd pollution in all sites was the most serious, followed by Cr and Pb. In Hunan, Cd has already exceeded the maximum limit value and needs to be controlled urgently. The input of heavy metals from irrigation water, fertilizers, and straw returning could be controlled by proposing more policies to manage their quality and application amounts. The amount of heavy metals absorbed by plants could be increased by cultivating crops with hyperaccumulators and high-biomass plants.

Effects of elevation and geomorphology on cadmium, lead and chromium enrichment in paddy soil and rice: A case study in the Xiangtan basin of China

The distributions of heavy metals in paddy fields and rice along river valleys were studied to explore the key factors affecting the accumulation of heavy metals in the upstream terraces and downstream plains. Results from 975 sampling sites showed that elevation, growing season and soil organic matter (OM) had significant effects on the content of Cd and Pb in topsoil and rice. The content of Cd (0.47–0.66 mg kg−1) and Pb (49.9–68.6 mg kg−1) in paddy fields with low elevation (30–60 m) in the downstream plains was significantly higher than the content of Cd (0.29–0.38 mg kg−1) and Pb (43.9–56.3 mg kg−1) in the upstream terraces with high altitude (60–90 m). In the double-rice production area, late rice generally produced grains with higher Cd and Pb content than early rice. Soil Cd was positively increased with the content of OM, especially in the downstream plains. When elevation was used for principal component analysis, plains with low elevation were grouped together with high content of total and soluble Cd, OM and Pb in soil, as well as high content of Cd and Pb in late rice. Altitude is one of the key factors affecting Cd content in rice. Although content of Cr (93.7–138.0 mg kg−1) was significantly higher than that of Cd and Pb in soil, content of Cr was lower than that of Cd in rice. These results indicate that paddy fields with elevation of 30–60 m in the downstream plains had high risk to produce late rice with Cd and Pb content exceeding the food safety standard 0.2 mg kg−1, which may be resulted from the driving force of runoff on soil soluble Cd and Pb from terraces to alluvial plains in river valleys.

Incorporating field-based research into remote learning: An assessment of soil lead pollution in different land-use types in Los Angeles

A research-based course was developed to investigate the legacy of soil lead (Pb) pollution in Los Angeles, California. During the course, undergraduate and graduate students collected a total of 270 soil samples for analyses of metal (loid) concentrations in different land-use types (residential, park, and school). Residential soils had significantly higher Pb concentrations than other land uses (p < 0.01) exceeding the California recommended safety level for soil Pb (80 mg/kg) at the highest frequency (64% of samples), followed by schools (42%) and parks (6.0%). Soil Pb from all 87 census block groups was correlated with battery recycling plant and railroad proximity as geospatial indicators of childhood Pb exposure risk. Meanwhile, census block groups with higher Pb levels were correlated with higher percentages of the following population: those without health insurance, without college degrees, with a lower median household income and income below the poverty line, and ethnic and racial minorities (r = −0.46 to 0.59, p < 0.05). Principal component regression models significantly improved soil Pb estimation over correlation analysis by incorporating sociodemographic, economic, and geospatial risk factors for Pb exposure (R2 = 0.58, p < 0.05). This work provides new insights into how topsoil Pb prevails in various land-use types and their co-occurring sociodemographic, economic, and geospatial risk factors, indicating the need for multi-scalar assessment across urban land uses.

Characterization of the spatial and temporal distribution of lead around a battery industrial park by LA-SPAMS

A convenient technique for direct solids analysis, laser ablation single particle aerosol mass spectrometry (LA-SPAMS), was used to investigate lead and other components in soil and bark samples from around a battery industrial park. In total, over 50,000 particles ranging in size from 0.2 to 2 μm were sampled and approximately 15–35% of the particles were analyzed for chemical composition. The mean mass spectrum results showed that the intensity of lead varied widely among sampling points, reaching the highest intensity in the topsoil and bark at sampling point 4, located closest to the core factory. Based on the neural network algorithm of adaptive resonance theory (ART-2a), the topsoil and bark samples were classified into five categories: crustal composition (Ca+, silicates, aluminates, etc.), elemental carbon (C2-, C3−, C4−, etc.), organic carbon (CN−, levoglucosan, etc.), secondary inorganic sources (phosphates, nitrates, sulfates), and heavy metals (Pb+, Zn+, Cu+), with the proportion of Pb varying from 0.020 to 0.25% and 0.030–9.41% in topsoil and bark samples, respectively, while the proportion of Cu and Zn in topsoil and bark samples did not differ as greatly as Pb. In addition, the particle number concentrations of lead particles in topsoil and bark ranged from 0.14 to 3.48% and 0.36–37.93%, respectively. The concentrations of Pb in topsoil and bark samples measured by ICP-OES varied from 71 to 791 ppm and 172–2595 ppm, respectively. Overall, both the lead content in topsoil samples measured by LA-SPAMS and ICP-OES reached maximum values at sampling points 4 and 5, respectively, indicating moderate pollution with Pb at these two sites. This convenient LA-SPAMS method not only accurately detects the composition of solid samples, the mixing state of particulate matter, and the analytical component sources, but also omits tedious pretreatment steps, reduces the use of organic solvents, and shortens the detection time of solid samples, thereby providing an attractive method for soil environmental quality monitoring.

Challenges for the estimation of uncertainty of measurements made in situ

In situ measurements are made without the removal of a physical sample and have many advantages over traditional ex situ measurements, made on a removed sample usually in a remote laboratory. The quality of ex situ measurements is usually expressed primarily in terms of their measurement uncertainty, including that arising during the sampling process. However, estimates of uncertainty for in situ measurement values have not usually included this uncertainty from sampling (UfS). It is argued that the making of an in situ measurement inevitably includes the taking of an ‘undisturbed sample’ that generates UfS, which should be included in the estimate of measurement uncertainty. Because undisturbed samples are not prepared or mixed, as is usual for removed samples, the heterogeneity of the analyte concentration in the sampling target is the primary source of UfS. Existing methods for estimating UfS for ex situ measurements can broadly be applied to in situ measurements. However, four extra challenges that limit the design and uptake of uncertainty estimation for in situ methods are identified, and possible solutions and actions required are discussed. Examples of in situ measurements considered include Pb in top soil by hand-held PXRF, 137Cs at a nuclear site by portable gamma-ray spectrometry, and bilirubin in new-born infants by hand-held reflectance photometry.

The concurrent decline of soil lead and children’s blood lead in New Orleans

Lead (Pb) is extremely toxic and a major cause of chronic diseases worldwide. Pb is associated with health disparities, particularly within low-income populations. In biological systems, Pb mimics calcium and, among other effects, interrupts cell signaling. Furthermore, Pb exposure results in epigenetic changes that affect multigenerational gene expression. Exposure to Pb has decreased through primary prevention, including removal of Pb solder from canned food, regulating lead-based paint, and especially eliminating Pb additives in gasoline. While researchers observe a continuous decline in children's blood lead (BPb), reservoirs of exposure persist in topsoil, which stores the legacy dust from leaded gasoline and other sources. Our surveys of metropolitan New Orleans reveal that median topsoil Pb in communities (n = 274) decreased 44% from 99 mg/kg to 54 mg/kg (P value of 2.09 × 10-08), with a median depletion rate of ∼2.4 mg⋅kg⋅y-1 over 15 y. From 2000 through 2005 to 2011 through 2016, children's BPb declined from 3.6 μg/dL to 1.2 μg/dL or 64% (P value of 2.02 × 10-85), a decrease of ∼0.2 μg⋅dL⋅y-1 during a median of 12 y. Here, we explore the decline of children's BPb by examining a metabolism of cities framework of inputs, transformations, storages, and outputs. Our findings indicate that decreasing Pb in topsoil is an important factor in the continuous decline of children's BPb. Similar reductions are expected in other major US cities. The most contaminated urban communities, usually inhabited by vulnerable populations, require further reductions of topsoil Pb to fulfill primary prevention for the nation's children.

Soil treatment and crop rotation for in situ remediation of heavy metal-contaminated agricultural soil in gold mining areas

In many areas of China, agricultural land is subject to heavy metal contamination from mining activity. This study investigates an in situ remediation program suitable for the recovery of heavy metal-contaminated agricultural soil around mining areas. A 1-year field experiment was conducted in a gold mining area of Tongguan, Shaanxi Province, China, to evaluate the effectiveness of engineering remediation measures, including adding a layer of noncontaminated soil, or soil homogenization to 40 cm and 80 cm depths, and three crop rotation systems, including rye-corn rotation, wheat-corn rotation, and potato-adzuki bean rotation on ameliorating heavy metal pollutants from contaminated agricultural soil around mining areas. The results showed that soil treatment and crop rotation significantly decreased soil heavy metal concentrations, with 80 cm homogenization and wheat-corn rotation being most effective. After 1 year of in situ remediation using this combination, the concentrations of Hg, Cd, and Pb in topsoil (0–20 cm) were 71.7%, 82.4%, and 21.8% lower, respectively, than before remediation. The single and Nemero indexes of the edible parts of wheat and corn were both <1, indicating they were safe for consumption. The results provide a solution for the in situ remediation of heavy metal-contaminated agricultural soil in mining areas.

Spatial distribution, risk and potential sources of lead in soils in the vicinity of a historic industrial site

Because of measures taken by local and national government agencies to control releases of metals, former industrial sites in China that are contaminated with lead (Pb) in soils have been abandoned. Compared with historic sites themselves, little attention has been paid to contamination with Pb in areas surrounding these sites. In this study, a method by integrating sequential extraction and isotopic fingerprinting was proposed to reveal the key fractions of Pb contaminants in soils, trace their sources and determine the subject of liability for remediation. Topsoils from near a historic site, where lead oxide was produced, were found to be contaminated. Concentrations of Pb in soils were inversely proportional to distances from the industrial site and depth in soils. The predominant form of Pb was the Fe/Mn-oxide-bound fraction (FM3), which accounted for from 53.39% to 82.07% of total concentrations of Pb. Concentrations of Pb in vegetables produced on contaminated soils exceeded those allowed in food for consumption by humans. An assessment of hazards and risks posed by consumption of vegetables grown on these soils indicated relatively high potential for adverse effects on local residents around the closed plant. By use of isotopic finger printing for Pb, the abandoned factory was determined to be the most likely source of Pb in topsoils, especially fraction FM3. To mitigate exposures of people to Pb via consumption of locally produced food, recommended strategies should target legacy sources of Pb to soils in the vicinity of this historic industrial site.

Soil pollution: Anthropogenic versus geogenic contributions over large areas of the Lazio region

During the last three decades, the scientific community, politicians and decision makers have focussed on the behaviours of trace elements in soil, its accumulation and toxicity, the bioavailability and risk of metals, and soil remediation technologies. Trace metals (or metalloids), such as As, Pb, Cr, Cd, and Ni, cause more environmental contamination than organic chemicals. Therefore, it becomes increasingly important to distinguish between the geogenic and anthropogenic sources of these trace metals, and to understand that the background values change depending on the area and the scale of the area investigated.A total of 40 selected topsoil samples were collected near urban areas in the Lazio region of Italy, from sites characterised by different geological substrate, specifically the Appian Way Regional Park, Borgo Montello, Cisterna di Latina and Roccasecca. Concentrations of V, Cr, Mn, Fe, Co, Ni, Cu, As, Cd and Pb in topsoil and background samples collected at a depth of approximately 1m have been analysed. The analytical results were used to calculate the geoaccumulation index (Igeo) to evaluate possible metal enrichment in topsoil related to human activity. The results indicate that there is no contamination associated with anthropogenic impact at the selected sites; however, a detailed study based on the lithological characteristics of the areas indicates local enrichment by several of the metals considered, especially in the Roccasecca topsoil.

Declining atmospheric deposition of heavy metals over the last three decades is reflected in soil and foliage of 97 beech (Fagus sylvatica) stands in the Vienna Woods

Rigorous studies on long-term changes of heavy metal distribution in forest soils since the implementation of emission controls are rare. Hence, we resampled 97 old-growth beech stands in the Vienna Woods. This study exploits an extensive data set of soil (infiltration zone of stemflow and between trees area) and foliar chemistry from three decades ago. It was hypothesized that declining deposition of heavy metals is reflected in soil and foliar total contents of Pb, Cu, Zn, Ni, Mn and Fe. Mean soil contents of Pb in the stemflow area declined at the highest rate from 223 to 50 mg kg−1 within the last three decades. Soil contents of Pb and Ni decreased significantly both in the stemflow area and the between trees area down to 80–90 cm soil depth from 1984 to 2012. Top soil (0–5 cm) accumulation and simultaneous loss in the lower soil over time for the plant micro nutrients Cu and Zn are suggested to be caused by plant uptake from deep horizons. Reduced soil leaching, due to a mean soil pH (H2O) increase from 4.3 to 4.9, and increased plant cycling are put forward to explain the significant increase of total Mn contents in the infiltration zone of beech stemflow. Top soil Pb contents in the stemflow area presently exceed the critical value at which toxicity symptoms may occur at numerous sites. Mean foliar contents of all six studied heavy metals decreased within the last three decades, but plant supply with the micro nutrients Cu, Zn, Mn and Fe is still in the optimum range for beech trees. It is concluded that heavy metal pollution is not critical for the studied beech stands any longer.

Brassica juncea tested on urban soils moderately contaminated by lead: Origin of contamination and effect of chelates

ABSTRACTUrban garden soils are a potential repository of heavy metal pollution, resulting from either anthropogenic or geogenic origin. The efficiency of phytoextraction was compared on two garden soils with the same texture and topsoil Pb concentration (170 mg kg−1) but not the same origin: one geogenic, the other anthropogenic. Two varieties of Brassica juncea were tested with citric acid (25 mmol kg−1) or ethylenediaminetetraacetic acid (EDTA, 2.5 mmol kg−1). Geogenic Pb was shown to be two times less available than anthropogenic Pb, as a result of which the phytoextraction efficiency was reduced by 59%. Pb mobility in the soil was solely enhanced with EDTA, which increased the Pb concentration in shoots of B. juncea by between 14 and 26 times in comparison with the control. The highest Pb concentration in shoots still remained low, however (i.e., 45 mg kg−1 dry weight). Regardless of the chelates introduced, B. juncea 426308 accumulated roughly twice as much lead as B. juncea 211000, but only for the anthropogenic contaminated soil. Under these conditions, the amount of Pb accumulated by B. juncea (even when assisted by EDTA) was not high enough to envision achieving soil clean-up within a reasonable time frame.

An exploration of spatial human health risk assessment of soil toxic metals under different land uses using sequential indicator simulation

A modified method was proposed which integrates the spatial patterns of toxic metals simulated by sequential indicator simulation, different exposure models and local current land uses extracted by remote-sensing software into a dose-response model for human health risk assessment of toxic metals. A total of 156 soil samples with a various land uses containing farm land (F1–F25), forest land (W1–W12) and residential land (U1–U15) were collected in a grid pattern throughout Xiandao District (XDD), Hunan Province, China. The total Cr and Pb in topsoil were analyzed. Compared with Hunan soil background values, the elevated concentrations of Cr were mainly located in the east of XDD, and the elevated concentrations of Pb were scattered in the areas around F1, F6, F8, F13, F14, U5, U14, W2 and W11. For non-carcinogenic effects, the hazard index (HI) of Cr and Pb overall the XDD did not exceed the accepted level to adults. While to children, Cr and Pb exhibited HI higher than the accepted level around some areas. The assessment results indicated Cr and Pb should be regarded as the priority pollutants of concern in XDD. The first priority areas of concern were identified in region A with a high probability (>0.95) of risk in excess of the accepted level for Cr and Pb. The areas with probability of risk between 0.85 and 0.95 in region A were identified to be the secondary priority areas for Cr and Pb. The modified method was proved useful due to its improvement on previous studies and calculating a more realistic human health risk, thus reducing the probability of excessive environmental management.

Effectiveness of cracker dust as a capping material for Pb-rich soil in the mining town of Broken Hill, Australia

Lead (Pb)-poor ‘cracker dust’, commonly used in kerb and gutter construction, has been installed on top of Pb-rich soil surfaces in Broken Hill over the last few decades, with the aim of reducing the risk of human exposure to Pb particulates. In this study, topsoil (0–0.1m) and subsoil (0.3–0.5m) samples were collected along rays spanning all parts of the Broken Hill urban area to investigate the effectiveness of remediation with cracker dust. Total Pb concentrations in the fine earth fraction (<2mm) of topsoil and subsoil samples and the dust-sized fraction (<100μm) of topsoil samples were measured. Undisturbed subsoil Pb concentrations are high near the ‘Line of Lode’ (LoL) orebody, especially on its southern flank, but are similar to background Pb concentrations at locations more than 0.8km from the LoL. Topsoil Pb concentrations at locations near the LoL are very high, but tend to decrease rapidly with increasing distance from the LoL. At most sampled locations the topsoil is significantly enriched in Pb relative to the subsoil, while Pb concentrations in the dust-sized fraction of topsoils are generally twice as high as those in the fine earth fraction of topsoils. Notably, where cracker dust has been applied, most topsoil Pb concentrations are significantly lower, indicating that remediation with cracker dust has been generally effective. Although contemporary dust deposits in Broken Hill can be very rich in Pb, the relatively small amounts of dust deposited ensure that Pb accretion from fugitive dust deposition is a very gradual process; undisturbed cracker dust should have a ‘clean lifespan’ of at least 100years. However, a small number of cracker dusted sites are found to have Pb-enriched surfaces, suggesting that the efficacy of cracker dust is curtailed where fluvial transport of Pb-rich sediment and/or mixing of the applied cracker dust with the underlying Pb-rich soil occurs.

Canonical correspondence analysis of soil heavy metal pollution, microflora and enzyme activities in the Pb–Zn mine tailing dam collapse area of Sidi village, SW China

The impacts of the Pb–Zn mine tailing dam incident on the degree of environmental response from soil properties were investigated in Sidi village, Guangxi Zhuang Autonomous Region, SW China, using statistical analysis, as well as canonical correspondence analysis (CCA). From the descriptive statistical analysis of soil properties in Sidi village, it can be seen that the topsoil pH ranged from 5.53 to 6.57, while the mean value was 5.74, which reflects the acidic and oxidized effect of the tailing sand. The total Pb in topsoil ranged from 569.50 to 6,423 mg kg−1, while the mean value was 1,852.33 mg kg−1, and the total Zn in topsoil ranged from 240.70 to 5,513 mg kg−1, while the mean value was 1,190.42 mg kg−1, which indicates that this area should not be as farmland anymore according to the environmental quality evaluation standards for farmland of edible agricultural products of China HJ/T332-2006. By analyzing the statistical analysis data and the CCA bioplot, the total Pb and the total Zn have the significant positive correlation coefficients (r = 0.656, p < 0.01) and the angle between vectors of the total Pb and the total Zn is small, which confirms that the heavy metal contamination is mainly from the Pb–Zn intergrowth ore. Moreover, the soil microorganism and the total Pb–Zn are on the opposite quadrant in the CCA ordination diagram and the sensitivity of the soil microorganism to the total Pb–Zn in topsoil was observed in the order of bacteria < fungi < actinomyces. The soil enzyme was released by the soil microorganisms, therefore, the activities of invertase, urease, and alkaline phosphatase were inhibited into different degrees by the total Pb and the total Zn in topsoil. From the CCA biplot, their complex inwardness between the soil enzyme and the Pb–Zn contamination can be clearly and intuitively depicted. Then, the alkaline phosphatase activities have strongly positive correlation coefficients with the total Zn (r = 0.451, p < 0.05) and the urease activities (r = 0.394, p < 0.05).

Potential health risks of heavy metals in cultivated topsoil and grain, including correlations with human primary liver, lung and gastric cancer, in Anhui province, Eastern China

Environmental exposure to heavy metals is a well-known risk factor for cancers. To evaluate potential health risks of heavy metals (Cr, Cd, Pb, As and Hg) and Se in cultivated topsoil and grains, we investigated the concentrations of Hg, As and Se using atomic fluorescence spectrometry and Cr, Cd and Pb using inductive coupled plasma emission spectrometry (ICP-MS). We also analyzed human cancer tissues for heavy metals. Potential health risks for local residents were evaluated by calculating the hazard index (HI) and the total carcinogenic risk (TCR) for soil heavy metals and the target hazard quotient (THQ) and the carcinogenic risk (CR) for grain heavy metals. A bioconcentration factor (BCF) was applied to quantify the bioaccumulation of heavy metals. Our results demonstrated that the mean concentrations of heavy metals in soil were all within the safety limits set by FAO/WHO and Chinese regulations; however, the mean concentrations of Cr and Hg in grain exceeded the safety limits. HI and TCR for soil heavy metals were all within acceptable levels, but the THQ for four grain heavy metals exceeded the target value of 1 (Cr, 2.64; Pb, 1.41; As, 1.24; Hg, 1.07; Cd, 0.39). The grain CR for Cr, Pb and As exceeded the accepted risk level of 10−6. BCF values indicated that the bioaccumulation capacity decreased in the following sequence: Hg>Se>Cd>Cr>Pb>As. We also observed statistically significant correlations of topsoil Pb concentration with human gastric cancer and grain Hg with human liver cancer. Therefore, long-term low dose exposure of heavy metals may play a key role in tumorigenesis, and it may not be necessary to accumulate a high concentration of heavy metals in the human body for those metals to induce tumorigenesis.

Soil Lead Concentration Anomaly Regions in Agricultural Area of Central China

In this study, the spatial distribution of soil lead (Pb) concentration in topsoil in Henan, China, was surveyed and analyzed using geostatistics and geography information systems (GIS). The concentrations of Pb in topsoil were investigated based on 603 samples. Pb mean concentration of 28.2 mg/kg in surface soils was found to be higher than those in global soils, which ranged from 16.31376.9 mg/kg.. From spatial analysis results, soil lead concentration anomaly regions were found in Henan Province, central China. The classification of a soil Pb environmental risk in an area was likewise presented based on the different levels of environmental quality of Pb and was done by GIS technology. Accordingly, there is a higher local concentration of Pb in the surrounding areas of Luoyang and Nanyang, which is historic mining area.

As, Cd, Cr, Hg, Ni and Pb in Soil from Eastern Slope of Mt. Gongga, Eastern Tibet, China

Concentrations of As, Cd, Cr, Hg, Ni and Pb were determined in soils from the eastern slope of Mt. Gongga at an altitude of 7,556 m above sea level. Mean concentrations of As, Hg and Pb in top soil were below the tolerance limit (the grade-1 standard) set in China for uncontaminated soils. Nevertheless, Pb was found in topsoil from the eastern slope of Mt. Gongga at mean concentrations of 30.38±7.32 mg/kg dw, which was close to the tolerance limit. At one site in surface layer of the Faber’s fir mature forest, concentrations of Pb were all above the tolerance limit (35.7-43.1 mg/kg dw). Mean concentrations of Cd, Cr and Ni did exceed the tolerance limit (the grade-1 standard) set in China. Single-factor contaminant index data were calculated by taking into account the analytical information obtained from topsoil at each sampling site. Among heavy metals determined, the highest degree of topsoil pollution was found for Cd. The single-factor pollutant index values decreased in the order of PCd>PCr>PNi>PPb>PHg>PAs. Evidently, topsoil of the eastern slope of Mt. Gongga accumulated elevated levels of Cd and Cr and Ni. An integrated assessment of topsoil quality for six heavy metals analyzed indicated that the values of index PN for all sites varied between 0.92 and 4.89 and all are considered as ‘slight to pronounced impact’ by heavy metals.

Topsoil Contamination by Heavy Metals from a Local Brass Industrial Area of Nigeria

Contents of Cu, Zn and Pb in top soils of the vicinity of a local brass industrial site within a residential area in Bida, Niger State, Nigeria were determined. The obtained results from the soils of the vicinity of the local brass indus- trial site showed some extent of contamination with significant elevated mean values of 467± 455µgCug -1 , 181± 44µgZng -1 and 181± 201µPbg -1 , when compared to 5.4±1.2µgCug -1 , 12±3.2µgZng -1 and not detectable value for Pb from the control soils. Hence, this study has helped to create the public awareness with regard to the risk of the adverse health effects that could possibly arise from the environmental pollution by heavy metals, particularly with regard to Pb in soils and the con- sequent need for immediate remediation of the studied area.

Anthropogenic Influence on Selected Heavy Metal Contamination of Urban Soils of Akure City, Nigeria

Levels of Cd, Ni, and Pb in topsoil (0–5 cm) taken from seven different sites of the urban city of Akure, Nigeria, were determined using flame atomic absorption spectrophotometer after the wet digestion method. This was with a view to appraising the influence of various anthropogenic activities on heavy metal contamination of the urban soil. Results show that the range of Cd was 6.27–10.34 ppm, Ni 7.17–14.78 ppm, and Pb 9.22- 46.19 ppm. This analytical data indicated a significant accumulation of heavy metals above background levels, with highest concentrations found in mechanic/battery charger workshops. The level of accumulation was assessed using accumulation factor (AF), and the values obtained exceeded 4 in all sites. This implies that the heavy metals are not from the natural geochemistry of Akure but from human activities. The classes of contamination were differentiated using geoaccumulation index (I geo). The I geo performed revealed that Cd (2< I geo<3: Class 3), Ni (2< I geo<4: Class 3 and 4) and Pb (3< I geo<5: Class 4 and 5) belong to different classes of geoaccumulation index, but the contamination patterns (moderately to strongly contaminated) are similar in all sites, except the mechanic battery/charger workshop (moderately to extremely contaminated). The differences observed in the metal concentrations among the sites are statistically significant (P < 0.05).