Sediment Enrichment Factor Research Articles

Heavy Metal Pollution in a Lake: An Assessment of the Ecological Threat

The purpose of this study was to investigate and evaluate the presence of different heavy metals in sediment samples collected from water of Durgam Cheruvu . The concentrations of six heavy metals, namely arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), and zinc (Zn), were quantified using the technique of inductively coupled plasma-atomic emission spectroscopy (ICPAES). The investigation employed relative enrichment factors and prospective ecological risk indices to examine the contamination levels of heavy metals in sediment samples and evaluate their potential ecological impact on the surrounding ecosystem. The order of heavy metal sediment enrichment factors was determined to be as follows: chromium (Cr) exhibited the highest enrichment factor, followed by arsenic (As), cadmium (Cd), zinc (Zn), copper (Cu), and lead (Pb). Several potential ecological risk indices for heavy metals were identified. The order of decreasing reactivity of the elements is as follows: Cadmium (Cd) > Arsenic (As) > Chromium (Cr) > Copper (Cu) > Lead (Pb) > Zinc (Zn). The prospective ecological risk indices, as determined through calculations, indicate that the lake has been low contaminated by heavy metals. Cadmium (Cd) exhibited a moderate level of potential ecological risk within the ecological environment and emerged as the primary factor contributing to the possible toxicity response indices associated with different heavy metals in Durgam cheruvu. The application of analysis of variance was employed to determine the statistical significance of the observed fluctuations in heavy metal concentrations. The analysis of mean seasonal concentrations of metals revealed statistically significant variations across different seasons and sampling sites. The pollution in Durgam Cheruvu may be attributed to industrial and anthropogenic activity. We have put up a series of techniques that can be implemented to mitigate the accumulation of heavy metals in the lake.

Comparison Results of the Two Different Enrichment Factor Analysis Methods of Heavy Metals in the West Banjir Kanal River Sediment, Central Java

The West Banjir Kanal (WBK) River in Semarang City is a river that plays an important role in supporting the various needs of the people of Semarang City. Land use around the river and utilization of WBK river water, cause river water to be contaminated with heavy metals, which have the potential to accumulate in sediments. This study was conducted to analyze and compare the results of the analysis of metal enrichment factors Cd, Cr, Cu, Pb, and Zn in the sediments of the WBK river, Semarang, with 2 different methods. The study was conducted at 7 sampling stations, representing estuaries, middle, and upper reaches of rivers. Sediment was collected with Van Veen Grab, then prepared with wet digestion, then analyzed the metal concentration with AAS. The results showed that the concentration of metals in the sediment at the studied station was still within the limits of natural concentration. The enrichment factor of the metals Cd and Zn is smaller than 1, however, for other metals (Cr, Cu, and Pb) some have exceeded 1. The test results of the comparison of Cr, Cu, and Pb metal enrichment factors in sediments differed markedly for the 2 different methods. But on metals Cd and Zn can not be compared, because the variety of data is 0.

Heavy metal contamination of Batanghari River, Jambi, Indonesia: determination based on sediment enrichment factor value

Batanghari River is the primary source of water for the people of Jambi. Batanghari River’s condition nowadays is worrying because its color is no longer clear. This research focused on determining the content of heavy metals in the Batanghari River's water and sediment. The conducted analysis is an ICP-MS analysis to determine the level of heavy metal (Cu, Cr, Co, Cd, Hg), and an enrichment factor calculation is conducted to determine the source of pollution. The enrichment factor value from the Batanghari River sediment sample declined with the following sequence Cd>Hg>Cu>Cr>Co, in 10 pinpoint locations. These indicate a high degree of anthropogenic activities along the Batanghari River which become the source of heavy metals entering the Batanghari River. The average concentration of heavy metals in the Batanghari River showed that the metal concentrations of Cd, Cu, and Hg are higher than the quality standards that have been set, whereas the metal concentrations of Cr and Co are still by the quality standards that have been set in PP 22 the year 2021.

Impact of Eocene‐Oligocene Antarctic Glaciation on the Paleoceanography of the Weddell Sea

AbstractThe Eocene‐Oligocene Transition (EOT) at ∼34 Ma marked a climatic shift from greenhouse to icehouse conditions, toward long‐lasting lower global temperatures and a continental ice sheet in the Antarctic. We report on sedimentological and inorganic geochemical results across the EOT at Ocean Drilling Program (ODP) Site 696 in the Weddell Sea, within the Antarctic limb of the Atlantic circulation. The geochemical composition of detrital, authigenic and biogenic marine sediment components, and sortable silt proxies demonstrate the impact of ice growth on high latitude water masses. Sortable silt grain size and Zr/Rb ratios attest to a period of vigorous circulation at ∼36.2–35.8 Ma, coincident with a known warm interval in the Southern Ocean. Across the EOT, detrital provenance suggests that regional ice growth in the western Weddell Sea was stepwise, first expanding in the Antarctic Peninsula, followed by parts of West Antarctica. In conjunction with regional ice growth, high uranium enrichment factors (U EF) in sediments spanning the EOT interval indicate anoxic conditions in the sediment with evidence of carbonate dissolution. Following glacial expansion and sea‐ice formation at ∼33.6 Ma, a return to oxic conditions and carbonate preservation is observed with excess barium and phosphorous indicative of an increase in productivity, and potentially carbon export. Our results highlight the important connections between ice growth and the changing properties of high‐latitude water masses at the EOT with impacts on the global ocean circulation.

Spatial-temporal distribution and pollution indices of heavy metals in the Turnasuyu Stream sediment, Turkey.

The potential contamination levels and human health risk of heavy metals in sediment of the Turnasuyu Stream in Ordu, Turkey, were evaluated comprehensively by taking seasonal samples from three different locations. The order of the mean heavy metals (HMs) concentrations (mg/kg) were as follows: Fe > Al > Mn > Pb > Zn > Cu > Co > Cr > Ni > Cd > As. All HM levels, except Cd and Pb, were in the minimum enrichment range as assessed by the sediment enrichment factor (EF). Similar low contamination levels for all HM, except Pb and Cd, were also observed when the contamination factor (CF) and geo-accumulation index (Igeo) were taken into account. The low risk of the study area has also been confirmed by the ecological risk index (Eri) values. The probable human health risk assessment has been performed, and the lifetime cancer risk (LCR) values for adults were found as negligible with values below 10-6. In addition, the hazard index (HI) and total hazard index (THI) results were both higher in children than in adults. The Pearson correlation coefficient (PCC) revealed the highest correlation between Cd and Pb (0.85). When the ecological indexes and statistical results are evaluated together, it is thought that the presence of HMs in the sediment may be due to lithological reasons as well as anthropogenic activities such as quarrying, municipal, agricultural, and domestic discharges in the region. Mitigation measures should be taken in accordance with the standards within the river basin to prevent the potential risks of pollution.

Spatial distribution and ecological risk evaluation of toxic metals in the southern Black Sea coastal sediments

Spatial distribution and ecological risk levels of toxic metals (Cu, Pb, Zn, Ni, Co, As, Sr, V, and La) in sediments from the southern Black Sea coastal (Türkiye) were evaluated. The sediment samples were taken in April and May 2019 from thirty-one stations, from depths ranged between 16 and 65 m. The average metal concentrations (in dry weight) varied from 59.4 ± 4.8 to 102.5 ± 12.3 for Cu, 39.3 ± 4,1 to 46.1 ± 2.9 for Pb, 104.5 ± 4.7 to 126 ± 6.9 for Zn, 21.2 ± 1.8 to 24.9 ± 1.4 for Ni, 9.8 ± 0.4 to 16.6 ± 1.5 for As, 16.7 ± 0.5 to 18.2 ± 0.9 for Co, 68.2 ± 11.4 to 123.3 ± 13.5 for Sr, 82.7 ± 13.1 to 97.3 ± 4.3 for V, and 16.2 ± 1.8 to 23.6 ± 1.8 μg g−1 for La. Geoaccumulation index (IGEO), Sediment enrichment factor (SEF), and pollution load index (PLI) indicated that Cu and Pb are above the pollution limits. Thus, continuous pollution monitoring programs should be established. Moreover, measures should be implemented more effectively to prevent pollution.

Evaluation of toxic metals in different grain size fractions of sediments of the southeastern Black Sea

Surficial marine sediment samples were collected along the southeastern Black Sea (Trabzon) coast. The sampling was conducted in June 2019 from eleven stations, with the depths varying between 8 and 30 m. Metal concentrations (Cu, Pb, Zn, Ni, As, and Cr) were evaluated in four different sediment size fractions; 0.063 mm (F1), 0.125 mm (F2), 0.25 mm (F3), and 0.5 mm (F4). Geoaccumulation Index (IGEO), Sediment Enrichment Factor (SEF), Ecological Risk (Er), and Potential Ecological Risk Index (RI) were used to determine potential anthropogenic hotspots. Temperature, pH, salinity, dissolved oxygen, and total organic carbon were determined to assess the variation across the sampling area. The highest metal concentrations (Cu:113.4 ± 45.1; Pb:85.9 ± 28.9; Zn: 138.6 ± 18.8; Ni:37.8 ± 7.6; As:14.1 ± 3.6; and Cr: 29.9 ± 5.4 ppm) were obtained in the smallest sediment fraction 0.063 mm (F1). The fractions of sediment structure were polluted by Cu, Pb, and As from moderate and severe levels according to IGEO and SEF.

Beyond anoxia: Exploring sedimentary thallium isotopes in paleo-redox reconstructions from a new core top collection

The thallium isotopic composition (ε205Tl) of seawater has been identified as a promising proxy for global oceanic redox conditions due to its close association with Mn oxide burial. Currently the preferred archives for past seawater Tl isotope reconstructions are from anoxic (no oxygen detected) and/or sulfidic (no oxygen detected and free sulfide present) environments that may suffer from basin restriction. Here we conduct a comprehensive modern calibration of authigenic sedimentary ε205Tl with core tops covering a wide range of bottom water oxygenation and sediment compositions. We show that quantitative Tl removal in the reducing porewaters (e.g., Mn reduction) at/near the sediment–water interface could allow the sediments to track the water column ε205Tl. Even if the bottom water is not anoxic, a shallow oxygen penetration depth under high export productivity and/or high sedimentation rates may still allow rapid oxygen consumption and buildup of reducing porewaters conducive for complete Tl removal. Thus, applications of the Tl isotope redox proxy can be greatly expanded beyond the anoxic conditions into places with open-ocean connections and high mass accumulation rates for high-resolution temporal reconstructions. We present a decision tree using the sediment enrichment factors of Mn, Ba, and U to determine whether sediment archives are likely to record the seawater ε205Tl. We additionally provide an estimate of authigenic Tl burial fluxes in environments with quantitative Tl removal, which is roughly double the size of the ‘euxinic/anoxic’ sink in previously published global marine Tl mass balance estimates.

Redox-driven geochemical partitioning of metal(loid)s in the iron-rich anoxic sediments of a recently flooded lignite mine pit: Lake Medard, NW Czechia

We evaluated the geochemical partitioning of Fe, Mn, As, V, and REE in sediments of a recently flooded open-cast lignite mine to interpret their response to recently established anoxia, and minor variations in the redox potential of its ferruginous bottom water column. Results from a sequential extraction scheme targeting reactive Fe mineral phases are combined with an assessment of sediment enrichment factors and REE systematics. Across the sediment pile metal(loid)s are being released from pre-existing authigenic phases as minor shifts in redox potential induce elemental immobilisation through co-precipitation with Fe into mineral phases of diverse reactivity. REE systematics confirms that minor oscillations in the water column's redox state can trigger swift changes in the speciation of the redox-sensitive elements. The observed metal(loid)s enrichment in the sediments can either be considered an ecological risk, if a management scenario involving solely recreational purposes is conceived, but it can also be seen as a feasible source of critical metals (e.g., REE and V) that are amenable to sustainable, secondary metal recovery endeavours. By anticipating the fate of redox-sensitive metal(loid)s in our study site, we provide parameters useful to delineate management programmes of this and similar post-mining lakes.

Environmental, ecological and human health risk assessment of heavy metals in sediments at Samsun-Tekkeköy, North of Turkey.

A detailed study was conducted in order to evaluate the effects of heavy metal pollution in the sediments in terms of environmental, ecological, and human health. Sediment samples were collected from 5 different points in two seasons, namely summer (August 2017) and winter (December 2017), to determine the distribution of heavy metals, potential pollutants, and toxic and ecological risks in the river sediments in Samsun-Tekkeköy district located in the Mid-Black Sea Region of Turkey and to evaluate the human health risk. The distribution of heavy metals at the sampling points was Fe>Al>Mn>Zn>Cu>Cr>Ni>Pb>Cd based on their averages. According to the toxic risk index (TRI) results, sampling point OIZ (Organized Industrial Zone) Channel (T3) was also found to have a moderate risk, and it was determined that the highest contribution was from Cu>Ni>Cd>Cr, respectively. Potential ecological risk index (PERI) results revealed a low risk except for Cd metal at all sampling points. While the sediment enrichment factor (EF) did not show much metallization at many points, the highest enrichment was observed in Cd, Cu, and Zn metals at sampling point T3. According to the geoaccumulation index (Igeo) and contamination factor (CF), sampling point T3 showed contamination with Cd, Cu, Cr, and Zn. Evaluation of human health risk showed that the hazard index (HI) results of carcinogenic and non-carcinogenic risks were higher among children than adults. The total lifetime cancer risks (TLCR) of heavy metals were within the limits determined by USEPA. However, the risk was ranked as Cr>Cd>Pb. Sediment quality guidelines (SQGs) and pollution index results showed that heavy metal contamination was due to anthropogenic and industrial activities since the region was an industrial zone. It was determined that heavy metals posed ecological risks and that the Samsun-Tekkeköy region was moderately and significantly contaminated.

Assessment of heavy metal pollution and water quality characteristics of the reservoir control reaches in the middle Han River, China

The systematic and scientific assessments on heavy metal pollutions and water quality characteristics are greatly important to protecting the river and coastal eco-environment. In this paper, sediment size, organic matter, total nitrogen, total phosphorus, and heavy metal contents were analyzed by collecting surface sediments and surface water in the reservoir control reach of the middle Han River. Besides, sediment enrichment factor and sediment pollution index were used to evaluate the heavy metal pollution, and enrichment analysis and redundancy analysis were applied to analyze the sources of heavy metals in sediments. The results show a low heavy metal content in the surface water, and the water quality is graded as a Good level. The average enrichment factor of Cd in surface sediments reached 4.63. Zn and Cu also showed significant enrichment in the tributary sediments, whose content far exceeded the background value of soil elements. Thus, the potential ecological risk of heavy metals was at a medium level. Statistical analysis and enrichment factors showed that the accumulation of heavy metals in sediments was affected by pollutant input and reservoir regulation, and it was urgent to conduct an integrated regulation of the heavy metals in river sediment. This study provided an insight into the understanding of feasible assessment for heavy metal contaminated sediment.

Reconstruction of metal(loid)s pollution history in sediments of Wami Estuary, Indian Ocean Coast of Tanzania

Results of metal(loid)s pollution history, their enrichment and contamination factors in sediments of Wami River Estuary, Tanzania are presented. Two sediment cores (WE1 and WE2) were retrieved from the Estuary using hand-driven PVC coring tubes. Levels of metal(loid)s in sediment samples were determined using EDXRF spectrometer coupled with X-lab ProTM software. Metal(loid)s enrichment factors (EF) were determined using metal(loid)s baseline values established during this study. Contamination factors were determined by dividing measured metal(lod)s concentrations in the samples by their respective baseline concentrations. Sediment physical chemical parameters were determined in order to establish their relationship with metal(loid)s concentrations. Sediment chronologies were established using the Constant Initial Concentration (CIC) lead-210 sediment-dating model in order to convert sediment depth profile into timescales. The lowest concentrations of As in sediments was measured in sediments deposited during 1960s, followed by increase reaching the highest concentrations in sediments deposited between ca. 2015 and 2017. Lowest and highest concentrations of Cd were measured in 1960’s and ca. 2000, respectively. Cu and Zn had their maximum concentrations in ca. 1971 and their significant positive correlation (r = 0.94, p = 0.01) suggest common origin of these metals. Average metals enrichment factors in the core were established and are in the order As = Cd = Cu = Pb = Zn = 0.1. This EF value suggests that all metals in sediments of Wami originate from natural sources (EF < 1). Metal(loid)s contamination factors (CF) were low to moderate for As, Cu and Zn; moderate for Pb; and low to considerable for Cd. CIC model revealed that the sediment at the bottom of cores WE1 and WE2 date back about 33 and 55 years, respectively. Sediments of Wami Estuary is characterized by mixing as evidenced in the established chronologies. Therefore, reported radiometric dates should be considered as a preliminary chronological estimate and further research is needed focused on terrestrial records of anthropogenic activities.

Assessment of heavy metals contamination and sediment quality in Ondo coastal marine area, Nigeria

Heavy metals contamination and sediment quality are parts of the major concerns of the aquatic ecosystem globally. To assess the contamination and sediment quality of the Ondo coastal marine area, a total of seventy two (72) sediment samples were collected from three sampling locations along the coastal region. The concentrations of As, Cd, Cr, Cu, Fe, Ni, Pb and Zn were determined by employing Atomic Absorption Spectrophotometry (AAS). The contamination status and quality were assessed by employing sediment enrichment factor (Ksef), contamination factor (Cfi), and modified degree of contamination (mCd), sediment quality guidelines (SQG), sediment toxicity degree (STd) and toxicity load index (TLI). The sources of heavy metals were defined by employing principal component factor analysis (PCFA) approach. Iron had the highest average concentration values of 417.50 ± 89.87, 369.38 ± 80.04 and 286.17 ± 65.21 μg/g at Ayetoro, Abereke and Awoye sites, respectively. The Ksef values of As, Zn, Pb and Cd were < 50 revealing severe enrichment. The Cfi values of As were >6 at Abereke and Awoye sites showing moderate contamination condition. The mCd value of Ayetoro site is 3.0 indicating moderate degree of contamination. The SQG-Q values for Abereke and Awoye were 2.5 and 3.5 representing potential of adverse effects on the biological organism in the sediments. The STd values for As, Cr, Cu, Zn, Ni and Pb were between 1 and 1.5 (1 < STd ≤ 1.5) indicating low toxic level. The result of TLI three sites was 0.52 implying low metals toxicity. PCFA analysis identified mixed source (anthropogenic and natural sources), transportation services, and wastes disposal activities as major sources of heavy metals in the sediment of the study area. This study indicated low contamination and toxicity level of sediment due to heavy metals but a progressive discharge and accumulation of heavy metals in the sediment could occur from continuous oil exploration, transportation services and wastes disposal activities which may threaten aquatic ecosystem.

Metals content in sediments of ephemeral streams with small reservoirs (the Negev Desert)

The content of 19 metals (chromium, cobalt, nickel, strontium, arsenic, magnesium, barium, cesium, gallium, rubidium, uranium, vanadium, zinc, lead, copper, cadmium, iron, manganese, and aluminum) in sediment in three ephemeral streams (Nahal Sansana, Nahal Revivim and Nahal Pura) with reservoirs in the Negev Desert is studied herein. The study was done in September 2016. The samples were collected from the surface layer of sediment (up to 10 cm) in the reservoirs and in the channels upstream and downstream of the reservoirs. Silt, which on average, accounted for 72% dominated in the sediment. In the spatial distribution of the particle size, sand and gravel fractions were deposited in the reservoirs. Aluminum, iron, and magnesium accounted for 99% of all analyzed metals. The Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) showed that sediment in the Negev Desert channel upstream of the reservoirs had similar concentrations of metals. Similarities were also found between the analyzed reservoirs. The bottom sediment in reservoirs had higher concentrations of metals than sediment upstream and downstream of the reservoirs. The comparison of concentrations in upstream and downstream locations did not show any unambiguous trends because metal concentrations downstream from the reservoirs were not always lower than upstream of the reservoirs. The analysis of the sediment enrichment factor (EF) showed the highest value in the reservoirs and the lowest downstream of the reservoirs. The concentrations of most analyzed metals did not indicate the possibility of potential ecological risk (SQG).

Heavy Metal Enrichment Factors in Fluvial Sediments of an Amazonian Basin Impacted by Gold Mining.

Artisanal and small-scale gold mining (ASGM) has been performed in the southern Ecuadorian Amazon since the colonial period. However, its effects on fluvial systems have been poorly investigated. Thus, in order to calculate the normalized enrichment factors (NEF) of several heavy metals in fluvial sediments of the Zamora River basin (Ecuadorian Amazon), we analyzed bottom sediments along ASGM-affected and unaffected river sections. The results indicated that sediments of the Congüime River have NEF between 2.2 and 2.3 for Cu (moderate contamination) and higher than 3 for Mn, Zn, Pb, and Hg (severe contamination). Similarly, a severe contamination is also observed in the lower Nangaritza River, due to sediments of this sector have NEF > 3 for Zn, Pb, and Hg. Bottom sediments from the Nambija and Zamora rivers showed a severe contamination with Hg (NEF > 3), suggesting the existence of ASGM activities in the upper Zamora River basin.

Shallow water anoxia in the Mesoproterozoic ocean: Evidence from the Bashkir Meganticlinorium, Southern Urals

The apparent lag between the first permanent rise of atmospheric oxygen to appreciable levels and oxygenation of the deep ocean has focused efforts in deciphering the evolution of seawater chemistry across the Proterozoic Eon (2.5–0.542 Ga). It is generally accepted that from ∼1.85 Ga oxic shallow marine waters were widespread while the deep ocean remained dominantly ferruginous (Fe(II)-rich), with episodic euxinia confined to productive continental margins and intracontinental basins. The geochemical record that informs this picture, however, is currently sparse, and further studies are required to adequately evaluate temporal and spatial variability in ocean redox conditions across this vast expanse of time. Here, we report Fe-S-C systematics, alongside major (Al, Mn) and trace metal (Mo, U) data for ∼1.6–0.8 Ga marine sediments from the Bashkir Meganticlinorium (BMA), Southern Urals, Russia. Our Fe speciation data reveal a water column dominated by ferruginous conditions, no evidence for euxinia, and oxygenated waters confined to only the shallowest, near-coastal settings. Trace metal data support these findings, with Mo and U enrichment factors in anoxic sediments implying the operation of a particulate Fe (oxyhydr)oxide shuttle under ferruginous conditions as the main mechanism for generating moderate authigenic Mo enrichments. Sulfur isotope systematics imply that predominantly low dissolved sulfate concentrations prevailed throughout the deposition of the BMA succession, which, in combination with a low organic carbon loading, promoted the development of ferruginous, rather than euxinic, water column conditions. The restriction of oxic conditions to the shallowest, near-coastal depositional settings within the Bashkir basin contrasts to other redox studies from this period. Such discrepancies highlight major uncertainty in our understanding of the temporal and spatial evolution of water column redox chemistry across the Mesoproterozoic Era, and signify the need for further detailed work to constrain the chemical evolution of the oceans during this crucial time period.

Spectral fitting approach for the determination of enrichment and contamination factors in mining sediments using laser-induced breakdown spectroscopy.

Monitoring of pollution index values in sediments is crucial in assessing the environmental impacts of toxic metals in a given location. These indices are typically acquired using elaborate and tedious calibration curve-dependent techniques such as (inductively coupled plasma - optical emission spectroscopy) ICP-OES and (atomic absorption spectroscopy) AAS. In this study, laser-induced breakdown spectroscopy (LIBS) was used as a simple and fast alternative method for estimating enrichment factor (EF) and contamination factor (CF) of the sediment samples obtained from selected mining sites. Quantitative analyses of three metal targets (Cd, Pb, and Zn) were done using a calibration-free LIBS method based on the Boltzmann population distribution. Both the EF and CF values calculated from classical ICP-OES method provided significantly high correspondence with the respective EF (R2 = 0.8862-0.9770, p < 0.01-0.05) and CF (R2 = 0.9454-0.9714, p < 0.01) obtained from the developed LIBS method. The intensity-based LIBS approach identified samples AC2 and CCC as the ones with the highest and lowest pollution index values, respectively. The same observation was seen using the concentration-based ICP-OES technique which showed good correlation between the two methods. The correlation results showed the potential of the curve-fitting LIBS analysis in evaluating the level of metal contamination in an area without the preparation of matrix-matched calibration curves.

Distribution of heavy metals and metalloid in surface sediments of heavily-mined area for bauxite ore in Pengerang, Malaysia and associated risk assessment

A detailed investigation has been conducted to evaluate the distribution of heavy metals and metalloid in the surface sediments of a bauxite mining area in association with the potential ecological and human health risk. Field sampling was carried out within the Pengerang bauxite mining areas, including mine tailings, ex-mining pond and streams. Distribution of heavy metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, Sr, Zn) and metalloid such as As in sediments indicated that Fe and Al constituted the greatest portion of metal elements in the sediment while Pb and Cu were found exceeding the recommended guideline values at some locations. Assessment of potential ecological risk (PERI) demonstrated low to medium ecological risk in the metal-contaminated sediments with Cd, As and Pb have generally greater risk compared to other metals, contributing the most to the total risk index (RI). The sediment enrichment factor (EF) indicated no enrichment of most metals while Pb and As at some locations were classified as having minor and moderately to severe enrichment. The geo-accumulation index (Igeo) and contamination factor (CF) indicated that the sediments were classified uncontaminated with respect to most metals. Assessment of potential human health risk revealed that the hazard index (HI) values of the carcinogenic and non-carcinogenic risks were an order of magnitude higher among children compared to adults. There were no significant non-carcinogenic risk due to metals and metalloid in the study area as HIs <1. However, the lifetime cancer risk (LCR) for As is relatively higher than other metals and falls within tolerable LCR for regulatory purposes. Therefore, this study has highlighted the implication on potential ecological and human health risks of heavy metal occurrence in sediments of bauxite mining areas thus indicating the importance of geomorphological changes due to land exploitation for mining sector.

Assessment of streambed sediment contamination by heavy metals: The case of the Gabes Catchment, South-eastern Tunisia

This study deals with the assessment of the behaviour of seven heavy metals (Cd, Zn, Cu, Pb, Ni, Cr and As) in streambed sediments within the Gabes Catchment, located in South-eastern Tunisia. To understand the effect of intense human activities in the Gabes Basin on the quality of the environment, 22 sediment samples, spread all over the study basin, were taken and analyzed for heavy metals. Heavy metal concentrations were shown to vary in the following order: Zn > Pb > Cu > Cr > Ni > Cd > As. Sediment quality was assessed based on the evaluation of various indices. A total of 27% of the sampling stations are characterised by sediment Enrichment Factors (EF) exceeding 40, reflecting extremely severe pollution. This result was also confirmed by different indices, including Sediment Pollution Index (SPI), Pollution Load Index (PLI) and Geo-accumulation index. The calculation of Mean Effect Range-Median Quotient (M-ERM-Q) indicated that in stream discharge, all metals have a probability of 21% to be toxic. The ecological toxicity risk of heavy metals increases close to urban (traffic activity) and industrial activities (industrial complex of Gabes). Close to Gabes City, the situation and the degree of contamination that may be transferred into marine ecosystems is worrisome and requires immediate intervention.

Distribution of trace elements in flowing surface waters: Effect of seasons and anthropogenic practices in India

ABSTRACTThis study reports the distribution of Cr, Ni, Cu and Pb in waters, sediments, macrophytes and fish of the Yamuna River’s patch in Delhi (India). This is one of the most polluted stretches of rivers in the world. Water from this river is used fosr irrigation, industrial and domestic purposes, including drinking water. The effects of season and anthropogenic practices were identified. Almost zero dissolved oxygen and high levels of lead and phosphate indicate the polluted state of the aquatic system. The enrichment factors in sediments (with respect to reference site) vary in the range of 0.60–82.9% (Cr), 1.40–90.5% (Ni), 1.00–85.3% (Cu) and 3.80–86.6% (Pb). The toxic effects due to Ni and Pb could frequently be visible in aquatic life as their values fall above the probable effect level (36 mg Kg−1 for Ni and 91.3 mg Kg−1 for Pb). The metal contents in the macrophyte (Eichhornia crassipes) and the fish (Oreochromis niloticus) generally increase in the summer season. Cu and Pb accumulate preferentially in E. crassipes. The fish from these waters is unsuitable for human consumption as the levels of Cr, Cu and Pb are above the recommended limits. Significant spatial variations in parameters of water and sediments were confirmed via one-way analysis of variance. The Pearson’s correlation analysis suggests a common source of some of the metals. Principal component analysis highlighted domestic, and industrial waste and coal-fired thermal power plants as the metal sources. This study might act as a benchmark for other investigations focused on similarly affected surface aquatic systems due to agricultural and industrial activities.