Spatial Distribution Of Metals Research Articles

Source identification and risk assessment of heavy metals in road dust of steel industrial city (Anshan), Liaoning, Northeast China

The purpose of the study was to acquire the source and evaluate the risk posed by heavy metals in road dust of steel industrial city (Anshan), Liaoning, Northeast China. Potential ecological risk index (RI), pollution index (PI) and geo-accumulation index (Igeo) were applied to evaluate the heavy metal pollution level, and the carcinogenic risk (RI) and hazard index (HI) were calculated to estimate the human health risk. The geographic information system maps clearly reveal the hot spots of heavy metal spatial distribution. Principle component analysis (PCA) and cluster analysis (CA) classified heavy metals into three groups. The metal Zn and Pb originate from the traffic emission, while Cd, Cr, Fe, Mn, Ni and Sb primarily come from industrial activities. These two pathways were the major source of heavy metals pollution by positive matrix factorization (PMF). The Igeo and PI values of heavy metals were decreased in the following order: Cd > Sb > Zn > Fe > Pb > Cu > Cr > Sn > Mn > Ni. The RI index showed the heavy metals were moderate to very high potential ecological risk. The HI values for children and adults presented a decreasing order of Cr > Pb > Ni > Cu > Cd > Zn. The HI also predicted a possibility of non-carcinogenic risk for children living in urban areas in comparison with adults.

Spatial distribution of metal(loid) depletion and accumulation zones around a natural carbon dioxide degassing site

Long-term influence of geogenic CO2 affects soil conditions and pedogenesis. Mobilization of metals and metalloids from soil to solution has been reported to occur in natural CO2 degassing sites, so-called mofettes. We determined metal(loid)-specific spatial distribution patterns in soil around a mofette as well as metal(loid) pore water concentrations along a CO2 gradient (0–98% CO2 in soil air). Depletion of Mn, Co, and Ni in soil in the mofette center was caused by leaching due to the long-term soil acidification leading to correspondingly low pore water concentrations and thus indicating no recent influence of CO2 on metal(loid) mobility. Iron and As were also depleted in soil within the mofette center where pedogenic Fe (oxyhydr)oxides could not form due to absence of oxygen. Small-scale variations in redox conditions lead to ongoing Fe cycling and the repeated reduction of Fe (oxyhydr)oxides resulted in increased Fe and As pore water concentrations at high CO2. Precipitation in form of sulfide minerals caused immobilization and accumulation of Cd, Cu, and Zn directly in the degassing center. The highest mobilization risk occurred within 2–4 m distance from the degassing center, where complexation with dissolved organic matter (DOM) increased the mobility of Al, As, Cr, Cu, Fe, and Zn. Our results show that CO2 as soil-forming factor influences the spatial distribution of metal(loid)s. The highest metal(loid) mobilization risk after long-term CO2 influence arises from accumulation of scarcely degraded organic matter, which can easily dissolve and form mobile metal(loid)-DOM complexes.

Изменение пространственного распределения металлов под воздействием реакционной среды в системе, образованной напылением пленки золота на поверхность серебряной фольги

Методом рентгеновской фотоэлектронной спектроскопии (РФЭС) исследовано поведение пленки золота, напыленной на поверхность серебряной фольги, при нагреве в вакууме или в диоксиде азота (давление 10–5 мбар) при 200 °С. Исходная пленка золота имела толщину 2—2.7 нм. Показано, что в процессе нагрева происходит растворение пленки золота в объеме серебряной фольги с образованием сплава Ag—Au. На основе анализа изменений, происходящих с отношением интенсивности Оже-линии AgMVV к интенсивности фотоэмиссионной линии Ag3d, было установлено, что поверхность сплава обогащена серебром. Процесс обогащения протекает более эффективно при нагреве системы в присутствии NO2.

Stream sediments geochemical investigations in Deliklitas and Ovacık (Balikesir), Turkey

ABSTRACTStream sediment sampling was carried out of the Deliklitas and Ovacık region, western Turkey. These sediments are derived mainly from Miocene intermediate volcanic rocks. The volcanics are widely affected by hydrothermal alteration. A total of 50 stream sediment samples were collected from the alteration area and its vicinity. They were then analysed for metal element content and spatial distribution at the different sampling locations. Factor analysis of the data produced a three-factor model which accounted for 72.29% of the total variance in the data with the following three metal element associations: Au-Ag-Cd-Pb-W-Zn, Co-Cu-Ga-V, and As-Sb. The Au-Ag association indicated gold mineralization while the others reflected lithologic control.

Distribution and pollution assessment of heavy metals in the intertidal zone environments of typical sea areas in China

The heavy metals (Cu, Cr, Zn, Cd, Pb) were analysed for 217 surface sediment samples collected across 14 typical intertidal zone areas in China. The data reveals the heavy metals spatial distribution patterns and correlations among their concentrations. Cu, Zn, Cd and Cr showed similar trends of spatial variation and the correlations between the concentrations of every two heavy metals were significantly positive except for the correlation between Pb and Cr concentrations. By using Nemerow index method, Enrichment factor and Sediment Quality Guidelines, it is found that Hangzhou Bay and Jiulong River Estuary were polluted, Yingluo Bay and Dongzhaigang Bay were Cd-rich areas. Except Beidaihe shoal, Sishili Bay and Yingluo Bay that were not exposed to any ecological risk of heavy metals and had no adverse biotoxic effects, the other 11 typical intertidal zone areas were exposed to moderate ecological risk of heavy metals in the sediment with potential adverse biotoxic effects.

Using Xps Data for Determining Spatial Distribution of Metals in Bimetallic Particles Supported on a Flat Surface

Expressions are obtained for the intensities of photoemission lines of silver and gold in bimetallic particles formed during sequential deposition of metals on the flat surface of the support. Two cases are considered: bimetallic particles with a non-uniform distribution of metals (silver core covered with a gold shell) and alloy particles of uniform composition. The particle shapes are assumed to be hemispherical. Expressions were obtained for the photoemission lines of gold Au4f, Au3d3/2 and silver Ag3d as well as for the Auger line of silver AgMVV recorded using radiation AlKα (hν = 1486.6 eV) and AgLα (hν = 2983.4 eV). Gold shells on the surface of silver particles are shown to diminish the intensity ratio of AgMVV line to Ag3d line, and this effect becomes stronger with the increasing ratio γ of gold atoms to silver atoms. In the case of alloy particles Ag–Au, the intensity ratio of these lines also decreases with increasing γ, though to a much lesser extent. The intensity ratios of gold Au4f and Au3d3/2 lines to the silver Ag3d line are also considered. The obtained equations can be used in XPS studies to consider formation of bimetallic particles in model planar systems and the changes occurring with the particles as a result of heat treatment in a vacuum or in a reaction medium.

Enrichment of the Hot Intracluster Medium: Observations

Four decades ago, the firm detection of an Fe-K emission feature in the X-ray spectrum of the Perseus cluster revealed the presence of iron in its hot intracluster medium (ICM). With more advanced missions successfully launched over the last 20 years, this discovery has been extended to many other metals and to the hot atmospheres of many other galaxy clusters, groups, and giant elliptical galaxies, as evidence that the elemental bricks of life - synthesized by stars and supernovae - are also found at the largest scales of the Universe. Because the ICM, emitting in X-rays, is in collisional ionisation equilibrium, its elemental abundances can in principle be accurately measured. These abundance measurements, in turn, are valuable to constrain the physics and environmental conditions of the Type Ia and core-collapse supernovae that exploded and enriched the ICM over the entire cluster volume. On the other hand, the spatial distribution of metals across the ICM constitutes a remarkable signature of the chemical history and evolution of clusters, groups, and ellipticals. Here, we summarise the most significant achievements in measuring elemental abundances in the ICM, from the very first attempts up to the era of XMM-Newton, Chandra, and Suzaku and the unprecedented results obtained by Hitomi. We also discuss the current systematic limitations of these measurements and how the future missions XRISM and Athena will further improve our current knowledge of the ICM enrichment.

Assessment of the Geographical Detector Method for investigating heavy metal source apportionment in an urban watershed of Eastern China

Assessing heavy metal pollution in river sediments and identifying the key factors contributing to metal pollution are critical components for devising river environmental protection and remediation strategies to protect human and ecological health. This is especially important in urban areas where metals from a wide range of sources contribute to sediment pollution. In this study, the metal enrichment factor (EF) was used to measure the watershed distribution of Cu, Zn, Pb and Cd in sediments in the Wen-Rui Tang urban river system in Wenzhou, Eastern China. The Geographical Detector Method (GDM) was specifically evaluated for its ability to analyze spatial relationships between metal EFs and their anthropogenic and natural control factors, including densities of industry (DI), livestock (DL), service industries (DS), population (DP), and roads (DR), along with agricultural area (AG), sediment total organic carbon (TOC), and soil types (ST). Results showed that the watershed was highly contaminated by all metals with an EF trend of Cd ≫ Zn > Cu > Pb. The spatial distribution of EFs demonstrated high contamination of all metals in the southwestern region of the watershed where industrial activities were concentrated, and higher Cu and Zn concentrations in the northeastern region having a high density of livestock production. GDM results identified DI as the dominant determinant for all metals, while TOC and ST were determined to have a moderate secondary influence for Zn, Pb and Cd. Additionally, GDM revealed several additive and nonlinear interactions between anthropogenic and natural factors influencing metal concentrations. Compared to other correlation, multiple linear regression and geographically weighted regression, GDM demonstrated distinct advantages of being able to assess both categorical and continuous variables and determine both single and multiple factor interactions. These attributes provide a more comprehensive understanding of metal spatial distributions while avoiding multicollinearity issues when identifying significant contributing factors at the watershed scale.

Spatial and seasonal characteristics of dissolved heavy metals in the surface seawater of the Yellow River Estuary, China

Spatial-seasonal variations, sources and correlations with seawater physiochemical factors and the pollution indexes of dissolved heavy metals in the surface seawater of the Yellow River Estuary in China were investigated. The concentrations of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), arsenic (As) and mercury (Hg) had ranges of 0.04–31.0 (11.6 ± 7.08), 0.42–13.3 (5.61 ± 3.55), 1.97–42.2 (14.9 ± 12.0), 0.10–1.90 (0.66 ± 0.37), 0.16–5.89 (2.59 ± 1.12) and 0.10–0.52 μg/L (0.24 ± 0.07), respectively, throughout the four seasons of the year. The concentrations of Cu, Pb, Zn and Cd were significantly high in winter relative to those in the other seasons, and the highest concentrations of Zn and Hg were detected in spring. The single contaminator factors of the elements are in the following order: Pb > Hg > Cu > Zn > Cd > As. The obtained degree of contamination showed that the Yellow River Estuary was highly polluted. The Cu and Zn concentrations were significantly correlated with temperature and suspended particulate matter (SPM). The Cd concentrations were significantly correlated with temperature, SPM, chemical oxygen demand (COD) and dissolved oxygen (DO). The As concentrations were significantly correlated with temperature, salinity, SPM and DO. The Hg concentrations were significantly correlated with salinity. We performed hierarchical cluster and principal component analyses to investigate the possible sources of heavy metals. Agricultural, industrial and atmospheric deposition resources were found to be possible sources of dissolved heavy metals in the studied area. Longshore currents, upwelling and the physicochemical parameters were possible influence factors of dissolved heavy metals spatial and seasonal distribution.

Trace metal pollution and ecological risk assessment in agricultural soil in Dexing Pb/Zn mining area, China

Surface agricultural soil samples obtained from Dexing Pb/Zn mining area in Jiangxi province were analyzed for trace metals to assess their pollution status and potential ecological risk. The spatial distributions and the major trace metals pollution sources were described and identified with the combination of chemical measures and geographic information systems technology. The level of pollution in seven metals is decreasing in the following order: zinc (Zn 128.9mg/kg) > chromium (Cr 64.1mg/kg) > lead (Pb 58.4mg/kg) > arsenic (As 45.3mg/kg) > copper (Cu 41.9mg/kg) > nickel (Ni 31.3mg/kg) > cadmium (Cd 1.5mg/kg). Trace metal spatial distribution maps established by geographic information system techniques displayed two high-pollution zones around mining sites in the study area. Multivariate statistical analyses were also applied, and the results demonstrated that Cd, As, Pb, Cu and Zn in the soils originated from mining activities, whereas Cr and Ni primarily originated from natural sources. The values of pollution index ranged from 4.79 to 71.59, and the values of modified pollution index ranged from 1.98 to 24.69. Moreover, the potential ecological risk values ranged from 264.0 to 3263.5, which indicated considerable ecological risk to very high ecological risk. The potential ecological risk values and other soil contamination indices showed similar patterns that the high-risk areas were around Dexing Pb/Zn mining site. The surface agricultural soil in study area is heavily to extremely polluted , with Cd that made the most dominant contribution.

Ulva australis as a tool for monitoring metal-polluted estuarine system; spatial and temporal considerations

<p>This study investigated temporal and spatial patterns of heavy metal content in Ulva australis. Samples were collected from the Derwent Estuary, Tasmania, Australia, over 3 years (2013-2015) at locations where historically arsenic, cadmium, lead and zinc were high in sediments and seawater. Zinc and lead content were high in U. australis at all sampling times, with levels consistent with the spatial distribution of metal within the system. Zinc in Ulva varied seasonally (4.8 – 320.7 mg·kg-1), but lead did not. Zinc and lead were highest in the middle-upper estuary, close to the zinc smelter, where seawater concentrations were higher. The results suggest that spatial variation of metal content in Ulva is a reflection of variability in the seawater, which in turn indicates that U. australis could be used for monitoring the effects of metals in estuarine systems, and that U. australis could be a useful addition to existing management strategies.</p>

Spatial diversity of Cr distribution in soil and groundwater sites in relation with land use management in a Mediterranean region: The case of C. Evia and Assopos-Thiva Basins, Greece

The present study compiles new and literature data in a GIS platform aiming to (a) evaluate the extent and magnitude of Cr contamination in a Mediterranean region (Assopos-Thiva and Central Evia (Euboea) Basins, Greece); (b) combine spatial distribution of Cr in soil and groundwater with land use maps; (c) determine geochemical constraints on contamination by Cr; and (d) provide information that will be useful for better management of land use in a Mediterranean type ecosystem in order to prevent further degradation of natural resources.The spatial diversity of Cr distribution in soils and groundwater throughout the C. Evia and Assopos-Thiva Basins is considered. It is attributed to both natural Cr sources (Cr-bearing peridotites, affecting primarily soil) and human (industrial) activities (the dominant source of groundwater contamination).A combination of the spatial distribution of metals in soil and land use maps was used to define the specific areas of agricultural land use with elevated heavy metal contents.Furthermore, the combination of the spatial distribution of Cr in groundwater and land use maps allows for definition of specific areas of industrial land use with elevated Cr concentrations (Inofita, south Assopos-Thiva Basin). Despite the good correlation (r = 0.75) between Cr(VI) and the strong oxidant NO3− in C. Evia, the lower standard potential (E0) values for NO3− compared to those for Cr2O72− (the latter is a stronger oxidant than the former) suggest that NO3− is not an oxidant of Cr.This detailed assessment and presentation of the available analytical data for soil and groundwater in Assopos-Thiva and C. Evia Basins on a land use map provides information for land management decision makers.

Spatial distribution of metals in the ICM: evolution of the iron excess in relaxed galaxy clusters

We investigate the spatial distribution of iron in the intra-cluster medium in a selected sample of 41 relaxed clusters in the redshift range $0.05 < z < 1.03$ using {\sl Chandra} archival data. We compute the azimuthally-averaged, deprojected $Z_{\rm Fe}$ profile of each cluster out to $\sim 0.4r_{500}$, and identify a peak in the distribution of iron followed by a flatter distribution at larger radii. Due to the steep gradient both in gas density and abundance, we find that the emission-weighted iron abundance within $0.2r_{500}$, which entirely includes the iron peak in most of the cases, is on average $\sim$25\% higher than the mass-weighted value, showing that spatially resolved analysis and accurate deprojection are key to study the evolution of iron enrichment in the very central regions of cool core clusters. We quantify the extent of the iron distribution in each cluster with a normalized scale parameter $r_{\rm Fe}$, defined as the radius where the iron abundance excess is half of its peak value. We find that $r_{\rm Fe}$ increases by a factor of $\sim 3$ from $z\sim 1$ to $z\sim 0.1$, suggesting that the spatial distribution of iron in the ICM extends with time, possibly due to the mixing with the mechanical-mode feedback from the central galaxy. We also find that the iron mass excess within $0.3r_{500}$, when normalized to the total baryonic mass within the same region, does not evolve significantly, showing that this iron mass component is already established at $z\sim 1$.

Geochemical Fractionation and Potential Ecological Risk of Cadmium and Lead in Soils Impacted by Secondary Lead Refinery.

Total and geochemical associations of Cd and Pb were studied on 75 topsoil samples around a small secondary metal recovery factory, which stopped operations in April 2006 due to metal environmental problems in surrounding communities. After a decade, we evaluated the potential ecological risk of Cd and Pb in impacted soils calculating the risk assessment code (RAC) and the risk index (RI) based on the Hakanson method. High concentrations of metals were found in soils around the factory, with dispersion pattern towards the north-west and south-east quadrants. Cadmium was predominant in exchangeable and carbonate fractions, while Pb was more associated to oxides, sulfides and in lesser extent to carbonates. The values of RAC and RI revealed a serious-considerable ecological risk in the surroundings of the land occupied by the factory and toward W-NW and SE. Statistical analyses showed that smelting activities had a great influence on the metals spatial distribution and their geochemical fractions in polluted soils.

Distribution, source and pollution level of heavy metals in river sediments from South China

The sediment pollution caused by heavy metals has attracted a great deal of attention due to its persistence, bioaccumulation and toxicity. This research was the first to consider the whole of South China to obtain an overall profile of heavy metal spatial distribution, possible sources and pollution levels in river systems. For these data, 14 selected heavy metals were analysed in river sediments collected from sampling sites in Guangdong, Fujian, Guangxi and Hainan Provinces. The geoaccumulation index and enrichment factor revealed that river systems in South China were universally contaminated by Cd, As and Sn, which might be distributed by anthropogenic activities. Moreover, Guangdong Province, a relatively developed area in South China, was relatively polluted by certain heavy metals such as Ni, Cu, Zn and Mn. Multivariate statistical analyses such as Pearson's correlation matrix and a principal component analysis determined that several of the heavy metals might be derived from similar anthropogenic activities such as industrial effluents and domestic sewage discharge. In terms of heavy metal contamination in South China, necessary measures should be undertaken to protect rivers in South China.

Continuous impact of mining activities on soil heavy metals levels and human health

Soils samples collected during different geochemical surveys of the city of Kajaran located near the biggest Cu-Mo mining area in Armenia were subjected to the multivariate geostatistical analysis and geochemical mapping in order to reveal soil heavy metals spatial distribution pattern and assess human health risk level under continuous impact of mining activities. In addition, human health risk assessment was done for the contents of Pb, Cu, Zn, Co, Mo, Mn, Ti, and Fe.The results of Principal Component Analysis and Cluster Analysis verify each other and were also complemented by the spatial distribution features of studied heavy metals indicating that two groups of elements have been generated. The first anthropogenically predominated group includes the main industrial elements Mo and Cu, and their accessories Pb and Zn while Ti, Mn, Fe and Co with the naturally predominant contents were observed in the second group. Moreover, the study reveals that the superposition of geogenic and anthropogenic components lead to the alteration of the shapes of areas with the high natural contents of heavy metals and formation of polluted areas with the intensive anomalies of elements.Health risk assessment showed that Mo was the only studied element which poses a non-carcinogenic risk to adult and children's health in some sampling sites during the whole period of investigations. Moreover, in all studied locations multi-elemental non-carcinogenic risk to children health from all studied heavy metals were detected. Special attention was given to the soils of kindergarten territories, and the results indicated that Hazard Index in kindergartens was >1 indicating an adverse health effect to children. The results obtained can serve as a basis for the development and implementation of risks reduction measures and systematic monitoring program planning.

Source identification and spatial distribution of metals in soils in a typical area of the lower Yellow River, eastern China

In this study, 234 soil samples were recently collected from Gaoqing County (a typical area of the lower Yellow River) to determine the contents of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Multivariate statistical analyses such as correlation analysis, principal components analysis, and one-way ANOVA were applied to identify the source of metals in the soil. Geostatistical methods were used to analyze the spatial structure and distribution of the metals. The results indicated that the mean contents of all metals exceeded the background value of the lower Yellow River, especially for As, Cu, and Hg (1.23, 1.20, and 1.29 times that of the BV, respectively), indicating that these metals were enriched in the study area to different degrees. The results derived from multivariate analysis suggested that As, Cd, Cr, Cu, Ni, Pb, and Zn were mainly controlled by the combination of human activities and soil parent material, and the human activities included industrial emissions, traffic emissions, and agricultural practices. In addition, Hg mainly originated from anthropogenic inputs, such as textile printing, plastics processing, and petrochemical engineering. The contents of metals in different types of land use and parent materials are clearly different. The mean content for eight elements in urban construction land was significantly higher than that of the other land use types; in addition to Hg, the mean content of the other elements was the highest in the lacustrine deposit. The elements of As, Cd, Cr, Cu, Ni, Pb, and Zn had similar hotspots in the urban area, indicating the significant human influence. In addition, these seven metals showed high values in the southeast lacustrine deposit area. The high-value areas of Hg were concentrated in the southwest and northeast study area, which were consistent with the spatial pattern of the industrial sites.

Investigation of the extent of contamination of heavy metals in agricultural soil using statistical analyses and contamination indices

ABSTRACTTo examine the level of contamination of Eshghabad region, Neyshabur, the concentration of heavy metals in soil was measured. For this purpose, 37 samples were taken from surface soil and the total concentration of heavy elements was measured by inductively coupled plasma (ICP). The mean concentration of Pb, Ni, Cu, Zn, and Fe was obtained to be 195, 87.3, 22.8, 274.8, and 2.5%, respectively. Using five valid indicators, the intensity of metal contamination in soil was calculated and compared. Furthermore, using statistical analyses, the relationships between the elements, their origins, and the spatial distribution of metals across various stations were investigated. The results indicated that the mean value of all of the studied metals (except for iron and copper) is greater than the mean concentration of metals in the Earth's crust. The indicators showed very high contamination for lead, while low to medium contamination for other elements of interest in the farming soils of the region. Statistical analyses indicated that there is a relatively similar contamination intensity across all of the studied stations. Considering the quality standards, the soils of this region are threatened by contamination of lead.

Soil Processes, Pedofeatures and Microscale Metal Distributions: Relevant Study of Contaminant-Dynamics Calls for Pedology-Based Soil-Depth Sampling Strategies

Short-term variations of soil conditions affect the form, mobility and bioavailability of metal pollutants. Released metals migrate toward depth where they are intercepted or precipitate, leading to variable spatial metal distribution patterns, at a macro-, meso- and microscale. Studies at a mesoscale give access to trace metal (TM) associations induced by pedological processes. Although scarcely documented, such meso-scale studies represent an essential step for relevant environmental risk assessment, halfway between field- and molecular-scale investigations. We argued for such approach by performing optical microscopy and micro-X-ray fluorescence on thin sections from two soils, contaminated either by industrial zinc-smelter waste or by urban wastewater. Consistent correlation between key indicators of pedological processes (Fe, Mn, and Ca) and trace metals (Zn, Pb, and Cu) on some 20 elemental maps of TM-hosting soil constituents and pedofeatures reveal distinct coinciding localizations, illustrating TM-accumulation via interception or (co)-precipitation processes. Micromorphological interpretation of characteristic pedofeatures in subsurface horizons (crystals, argillans, ferrans, and mangans) containing significant amounts of TM provide valuable insight into the contaminant dynamics in terms of lixiviation, colloidal transport, redox conditions, or fungal activity. Our mesoscale approach stresses the importance of pedology-based sampling strategies, instead of systematic soil-depth sampling, for soil contamination research in natural ecosystems

Spatial Variation of Metals in the Batang Arau River, West Sumatera, Indonesia.

This paper aims to assess metallic pollution in the Batang Arau River, an important source of freshwater supply for local communities in West Sumatera, Indonesia, by applying multivariate statistical techniques. Sampling was conducted at eight stations along the river from March to May 2014. The results indicate that all the metals studied have similar spatial distribution patterns, with an increasing trend in concentration from upstream to downstream. Total concentration of six metals studied upstream, as background concentration, was 1.050 mg/L, and increased to 2.249 mg/L downstream. Spatial distribution of metals did not show significant variability (p < 0.05) for Cd, Cr, Fe, and Pb, but Co and Mn did. The results of principal component analysis/factor analysis (PCA/FA) and correlation analysis suggest that Cd, Co, and Fe are originated from natural and anthropogenic sources; Cr and Pb are derived from natural sources; and Mn is controlled by anthropogenic sources.