Cd In Sediments Research Articles

Spatial-temporal variations of metals and arsenic in sediments from the Doce River after the Fundão Dam rupture and their bioaccumulation in Corbicula fluminea.

The rupture of the Fundão dam in Brazil released tons of mining tailings into the Doce River Basin (DRB). This investigation aimed to determine the bioaccumulation of metals in soft tissues of the bivalve Corbicula fluminea exposed to sediments collected in the DRB in four periods (just after, 1, 3, and 3.5 years after the dam rupture). In the exposure bioassays, the concentrations of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sediments and bivalve soft tissues were quantified. The concentration of some elements (As, Cd, Mn, and Al) in sediments exceeded the federal limits or regional backgrounds at some sampling sites, but their concentrations tended to decrease over time. However, higher concentrations of many elements were detected in the winter of 2019. Several elements were detected in C. fluminea soft tissues, but the bioaccumulation factors were generally low or not related to those elements associated with the ore tailings, evidencing that the bioavailability of metals to bivalves, in laboratory conditions, was limited. Integr Environ Assess Manag 2024;20:87-98. © 2023 SETAC.

Portunus pelagicus (Linnaeus, 1758) as a Sentinel Species to Assess Trace Metal Occurrence: A Case Study of Kuwait Waters (Northwestern Arabian Gulf).

Heavy metal pollution can adversely impact marine life, such as crabs, which can accumulate it in different organs and potentially transfer and biomagnify along the food chain in aquatic ecosystems. This study aimed to examine the concentrations of heavy metals (Cd, Cu, Pb, and Zn) in sediment, water, and crab tissues (gills, hepatopancreas, and carapace) of the blue swimmer crab Portunus pelagicus in the coastal areas of Kuwait, northwestern Arabian Gulf. Samples were collected from Shuwaikh Port, Shuaiba Port, and Al-Khiran areas. The accumulation of metals in crabs were higher in the carapace > gill > digestive gland, and the highest metal concentration was found in crabs collected from Shuwaikh > Shuaiba > Al-Khiran. The metal concentrations in the sediments were in the order Zn > Cu > Pb > Cd. Zn was the highest metal concentration detected in marine water sampled from the Al-Khiran Area, whereas the lowest metal was Cd sampled in water from the Shuwaikh Area. The results of this study validate the marine crab P. pelagicus as a relevant sentinel and prospective bioindicator for evaluating heavy metal pollution in marine ecosystems.

Risk source identification and diffusion trends of metal(loid)s in stream sediments from an abandoned arsenic-containing mine

Stream sediments from mine area are a converging source of water and soil pollution. The risk and development trends of metal(loid)s pollution in sediments from an abandoned arsenic-containing mine were studied using modelling techniques. The results showed that the combined techniques of geographic information system (GIS), random forest (RF), and numerical simulation (NS) could identify risk sources and diffusion trends of metal(loid)s in mine sediments. The median values of As, Cd, Hg, and Sb in sediments were 5.01, 3.02, 5.67, and 3.20 times of the background values of stream sediments in China, respectively. As (14.09%) and Hg (18.64%) pollution in mine stream sediments were severe while As is the main potential risk source with a strong spatial correlation. High-risk blocks were concentrated in the landfill area, with the surrounding pollution shows a decreasing trend of “step-type” pollution. The risk correlation between Hg and As (55.37%) in the landfill area is high. As a case of arsenic, the diffusion capacity of As within 500m is strong and stabilizes at 1 km when driven by the flows of 0.05, 0.5, and 5 m3/s, respectively. With the worst-case scenario flow (86 m3/s), it would take only 147 days for the waters within 3 km to become highly polluted. The high pollution levels in a stream under forecast of different distance intervals (500, 1500, 2000 m) within 6.5 km is arrived at approximate 344, 357, and 384 days, respectively. The study suggested the combined technique of GIS, RF, and NS can serve the risk source identification of contaminated sites and risk forecast of toxic element diffusion in emergency situations.

Geochemical controls on the distribution and bioavailability of heavy metals in sediments from Yangtze River to the East China Sea: Assessed by sequential extraction versus diffusive gradients in thin-films (DGT) technique

This study conducted a comprehensive investigation on the distribution and bioavailability of heavy metals (Cr, Co, Ni, Cu, Zn, Cd and Pb) in sediments along two typical transects from Yangtze River to the East China Sea continental shelf that spanning large physicochemical gradients. Heavy metals were mainly associated with the fine-grained sediments (enriched with organic matter), exhibiting decreasing trends from nearshore to offshore sites. The turbidity maximum zone showed the highest metal concentrations, which evaluated as polluted for some tested metals (especially Cd) using the geo-accumulation index. Based on the modified BCR procedure, the non-residual fractions of Cu, Zn and Pb were higher within the turbidity maximum zone, and significantly negatively correlated with bottom water salinity. The DGT-labile metals all positively correlated with the acid-soluble metal fraction (especially for Cd, Zn and Cr), and negatively correlated with salinity (except Co). Therefore, our results suggest salinity as the key factor controlling metal bioavailability, which could further modulate metal diffusive fluxes at the sediment-water interface. Considering that DGT probes could readily capture the bioavailable metal fractions, and reflect the impacts of salinity, we suggest DGT technique can be used as a robust predictor for metal bioavailability and mobility in estuary sediments.

Fixation Effect of Modified Bamboo Charcoal on Typical Heavy Metals in Sediment

In this study, we studied the influence of the dosage of modified bamboo charcoal (KAM-500-400-3) on the fixation effect of single Cu(II)-contaminated and mixed Cu(II)–Cd(II)-contaminated sediment. The results showed that it could effectively fix the heavy metals in both sediment types. In the single Cu(II)-contaminated sediment, when the amount of added KAM500-400-3 was greater than or equal to 5%, the Cu(II) content in the overlying and pore water was substantially reduced, and the form of heavy metal Cu(II) in the sediment changed from the acid-extractable state to a relatively stable, reducible, oxidizable, and residual state, its bioavailability markedly reduced, and the toxic leaching amount of heavy metal TCLP in the sediment also gradually reduced. In the sediment polluted by Cu(II)–Cd(II), the Cu(II) and Cd(II) could not be detected in the overlying or pore water when the addition amount was greater than or equal to 2.5%. The contents of Cu(II) and Cd(II) in the acid-extractable state considerably decreased and they transformed into other forms with low bioavailability, in which the content of Cd(II) in the oxidizable state was so low that it was lower than the detection limit. The TCLP toxicity of the leached amount of Cd(II) also gradually decreased. This showed that adding KAM500-400-3 to sediment helps with inhibiting the release of heavy metals from contaminated sediment into water bodies, so KAM500-400-3 is a material that can effectively adsorb and fix heavy metals Cu(II) and Cd(II) in sediment.

Potential risks of heavy metals in green mussels (Perna viridis) harvested from Cilincing and Kamal Muara, Jakarta Bay, Indonesia to human health

This study investigates Pb, Cd, and Cr in the suspended particulate matter (SPM), sediments, and green mussels from Cilincing and Kamal Muara, Jakarta Bay and estimates their potential human health risks. The results showed that the metal levels in SPM from Cilincing ranged from 0.81 to 1.69 mg/kg for Pb and 2.14 to 5.31 mg/kg for Cr, while in Kamal Muara ranged from 0.70 to 3.82 mg/kg for Pb and 1.88 to 4.78 mg/kg dry weight for Cr. The levels of Pb, Cd, and Cr in sediments from Cilincing ranged from 16.53 to 32.51 mg/kg, 0.91 to 2.52 mg/kg; and 0.62 to 1.0 mg/kg whereas in Kamal Muara ranged from 8.74 to 8.81 mg/kg; 0.51 to 1.79 mg/kg, and 0.27 to 0.31 mg/kg dry weight, respectively. The levels of Cd and Cr of green mussels in Cilincing ranged from 0.014 to 0.75 mg/kg and 0.003 to 0.11 mg/kg; while in Kamal Muara ranged from 0.015 to 0.073 mg/kg and 0.01 to 0.04 mg/kg wet weight, respectively. Pb was not detected in all samples of green mussels. The Pb, Cd, and Cr levels in the green mussels were still below the permissible limits set by international standards. However, the Target Hazard Quotient (THQ) for adult and children in several samples were higher than one indicating potential noncarcinogenic effects to consumers due to Cd accumulation. To reduce the detrimental effects of metals, we suggest maximum mussel consumption of 0.65 kg for adults and 0.19 kg for children in a week based on the highest level of metals.

Improved Method of Background Value Determination for Sb and Cd in Freshwater Sediment—Insights from Controlling Factors on Spatial Variability

Variability in the distribution of natural total Sb and Cd in freshwater sediments leads to difficulties in background value (BV) determination. This study aimed to establish a method to determine BV more accurately by investigating the vertical distribution of Sb and Cd in sediment cores collected from a typical river in alluvial plain in China and revealed the factors that control the variation of Sb and Cd BV, which has not been studied in alluvial freshwater sediment. The results suggested that uncontaminated samples for BV calculation should be determined by statistical analysis as human and natural disturbance led to high variation in contamination depth, from <5 cm to >55 cm. The sequential chemical extraction method showed a considerable amount of non-residual fractions of Sb and Cd, which accounted for 48% and 43% of the total, respectively. Acid extractable Cd (16%) was associated to the limestone geology in the area. Fine particles which governed by sedimentary environment contained more natural Sb and Cd, as strong positive correlation was found between clay content and Sb concentration (r = 0.89, p < 0.01), as well as Cd concentration (r = 0.54, p < 0.01). Based on these findings, a method combined with standard deviation and geochemical method was established to calculate the BV of Sb and Cd, and counter maps were made to cover the variation of BV in the Taipu river sediment. The pollution level has been evaluated by the geoaccumulation index more accurately.

High performance self-assembled nano-chlorapatite in the presence of lactonic sophorolipid for the immobilization of cadmium in polluted sediment.

A novel lactonic sophorolipid (LS) self-assembled nano-chlorapatite (LS-nClAP) was prepared for the immobilization of severe cadmium (Cd) in sediment. The experimental results indicated that the introduction of LS not only improved the dispersed performance of chlorapatite, but also brought massive hydroxyl and carboxyl groups, which significantly improved the immobilization efficiency of Cd and reduced its eco-toxicity in sediment. LS can significantly increase the effective utilization rate of phosphorus in chlorapatite, and reduce the content of available phosphorus (AP) by half after remediation compared with ClAP. Additionally, the participation of LS possessed a significant impact on the enzyme activities in the sediment, especially for urease, which was closely related to the effective stability of Cd and the introduction of LS. All experimental results of this study provided new insights into the possible effects of Cd immobilization by chlorapatite in contaminated sediments, demonstrating great application potential for sediment remediation in the future.

Studi Identifikasi Sebaran Ion Logam Pb, Cu, As dan Cd pada Air dan Sedimen di Perairan Bontang Kalimantan Timur Menggunakan Metode Kriging (Ordinary Kriging)

Bontang is one of the cities in East Kalimantan which is geographically located in coastal areas so that it is very vulnerable to marine pollution both from domestic human and industrial activities. This study aims to determine the level and pattern of distribution of poluton metal ions Pb, Cu, As and Cd in water and sediments in Bontang waters using the Kriging (Ordinary Kriging) method. In this study, 4 observation samples were used which were tested in the laboratory to determine the content of heavy metals. Furthermore, the data from laboratory tests along with 4 secondary data were interpolated using the ordinary kriging method with an exponential model to determine the pattern of contour distribution in Bontang waters. The results showed that the heavy metal with the highest distribution value in water and sediment is cadmium with a susceptibility value ranging from 0.006 mg/l to 9.070 mg/l. In general, the pattern of spread of heavy metals originates from coastal areas in a southeasterly direction. The most influential thing on this pattern of spread is tidal currents and bathymetry.

A comparative assessment of potentially harmful metals in the Lagos Lagoon and Ogun river catchment

Abstract Metals are one of the most common pollutants of surface water around the world. The anthropogenic contribution to aquatic metal pollution is of global concern. This study investigates the levels of Ca, Cd, Cu, Fe, Mn, Pb, Ni and Zn in surface water and sediments in the Lagos lagoon (Ibafon-Apapa, University of Lagos waterfront, UWF) and Ogun river catchment at Agiliti-Ketu. The metal concentrations were determined using atomic absorption spectrophotometry. Ibafon-Apapa generally, accounted for the highest concentrations of metals in both water and sediment samples. The ranges of concentrations (µg/g) of metals in sediment samples were: 0.08 ± 0.05–2140.64 ± 1981.54, ND-7.19 ± 7.32, 4.59 ± 2.46–78.95 ± 49.15, 3276.22 ± 2059.57–25,307.60 ± 8759.66, 255.73 ± 98.54–4651.0 ± 1672.60, 19.84 ± 10.23–228.50 ± 84.17, 4.51 ± 4.02–24.45 ± 22.78 for Ca, Cd, Cu, Fe, Mn, Pb and Zn, respectively. Ni occurred in the water and sediment samples below the detection limit. The water and sediments samples from UWF have mean pH values of 7.71 ± 0.07 and 6.61 ± 0.40, respectively, which are higher than that of Agiliti-Ketu (7.65 ± 0.06 and 6.58 ± 0.95) and Ibafon-Apapa (7.60 ± 0.39 and 4.20 ± 0.50), respectively. The highest values for electrical conductivity (EC) was recorded in Ibafon-Apapa (8.54 ± 1.27 μS/cm) followed by UWF (6.50 ± 2.16 μS/cm) and Agiliti-Ketu (0.28 ± 0.40 μS/cm), respectively. The relatively high values of EC and total dissolved solids (TDS) in the Ibafon-Apapa and UWF axis of the Lagos lagoon is an indication of the brackish nature of the lagoon, while the low mean values of EC (0.28 ± 0.40 μS/cm) and TDS (78.0 ± 13.04 mg/L) recorded for Agiliti-Ketu is a pointer to the freshwater attribute of the water. Cd, Mn, Fe and Pb were found to exceed the WHO limit for drinking water. Results were compared with global background values. Cadmium, manganese, iron and lead levels in the water and sediments samples revealed metals pollution. Statistical analysis of variance and t-test were used to analyze the data obtained. Metals pollution source control is recommended.

Assessment and sources of heavy metals in the suspended particulate matter, sediments and water of a karst lake in Guizhou Province, China

An integrated assessment of heavy metal (HM) contamination in dissolved matter, suspended particular matter (SPM) and sediments in lakes is essential. This study assessed the risks of HMs in the water, SPM and sediment of Caohai, China, and analyzed the changes in sediment HM contamination in conjunction with historical data. The HM transport was dominated by the SPM load, and the concentrations of Zn (179.07–1821.24 mg kg−1), Pb (53.63–181.46 mg kg−1), and Cd (3.68–21.31 mg kg−1) in SPM and sediment were 5.34–149.11 times higher than the upper continental crust (UCC) values. SPM and sediments were lightly to extremely polluted and had moderate to very high toxicity risks with Cd, Pb and Zn, and these three HMs originated from industrial and agricultural sources. The concentrations of Zn, Pb, and Cd in Caohai sediments increased by 36.7–187.9 % in 2022 compared to pre-2020. This research provides valuable reference data for the remediation of polluted karst lakes.

Contamination, Ecological Risk and Source Apportionment of Heavy Metals in the Surface Sediments in the Hailar River, the Upper Source of the Erguna River between China and Russia

The concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in 17 surface sediment samples from the Hailar River, the upper source of the Ergun River, which is the boundary river between China and Russia, were analyzed. Traceability and cause analysis of heavy metals in sediment were carried out by correlation analysis and principal component analysis. The results showed that the concentrations of Hg and Cd in sediments exceeded the soil background values. Due to the high biological toxicity factor of Hg, Hg is the highest potential ecological risk factor in the Hailar River and its tributary the Yimin River. The sources of Hg and As were likely to come from human activities including mining, coal burning and animal husbandry; other HMs, especially Zn and Cr, mainly come from mining and natural factors. Due to the high level of urbanization and more agricultural activities, the pollution potential of Cd, Hg and Pb in the Yimin River and the lower reaches of the Hailar River was greater. The results of this study will help to understand the distribution and pollution of heavy metals in river sediments in the basin and provide management support for China’s local environmental management departments and relevant national departments of China.

Ecological and environmental risks of heavy metals in sediments in Dingzi Bay, South Yellow Sea

As a special geographical location between rivers and oceans, coastal estuaries always face severe heavy metal contaminations, especially in semi-closed bay. In this study, the spatial distribution, chemical fraction, ecological risks, and potential sources of heavy metals (Pb, Cr, Cu, As, Cd, Zn, and Ni) in surface sediments and sediment cores were investigated in Dingzi Bay, Shandong Peninsula. The Igeo values and modified potential ecological risk index (MRI) indicated that Cd and As presented high environmental risks in the surface and sediment cores. The high concentration sites were mainly located in the middle and the mouth of the Dingzi Bay. The source identification indicated that most heavy metals in surface sediments originated from shipping and aquaculture, while As and Ni from industrial pollution. The correlation coefficients showed that high proportion of fine particle, TN, TOC, TP, and AVS in surface sediments could significantly elevate the bioavailability of most heavy metals.

Analysis of heavy metals in waters, sediments, and blood clams (Anadara granosa) in the pond at Sidoarjo Regency

As industry continues to develop, both the oil and gas industry, agriculture and other non-oil and gas industries, the level of environmental pollution in Sidoarjo Regency is also increasing. Heavy metals are one of the pollutants in domestic waste and industrial waste which can affect river water quality and can have negative impacts on humans and the environment. The aim of this research is to determine the concentration of the heavy metals lead (Pb) and cadmium (Cd) in water, sediment and blood clam meat, determine the maximum consumption limit for the heavy metals Pb and Cd contained in blood clams, and determine relationship between Pb and Cd concentrations in waters, sediments and blood clams at research study, Tambak Cemandi and Banjar Kemuning station. The sampling method in this research used random sampling. Testing for heavy metals Pb and Cd uses Atomic Absorption Spectrophotometry (AAS). The research results showed that the concentrations of heavy metals Pb and Cd in the waters, sediments and blood clams at the research location had exceeded the established safe limits. Pearson correlation analysis showed that there was no significant relationship between Pb and Cd concentrations in waters, sediments and blood clams.

Pollution and Potential Ecological Risk Evaluation of Heavy Metals in the Bottom Sediments: A Case Study of Eutrophic Bukwałd Lake Located in an Agricultural Catchment.

Metals are natural components of the earth's crust and are essential elements in the metabolism of fauna and flora. However, some metals at high concentrations may pose an ecological risk. Ecological risk analysis is one of the best methods for detecting potential metal pollution problems and its impact on ecosystems. This study analyzed the potential ecological risk and contamination from heavy metals (Cd, Cu, Pb, Ni, Cr, and Zn) in bottom sediments. It analyzed the spatial variability of heavy metal concentrations in the bottom sediments of Lake Bukwałd. The potential ecological risk index (RI) was used to assess the impact of pollutants accumulated in bottom sediments on the environment. In addition to RI, the geochemical index (Igeo) and contamination factor (CF) were also calculated. The pollutant loading index (PLI) was used to compare the average content of metals in the bottom sediments of lakes. The obtained results indicate that agricultural activity determined the quality of the bottom sediments of the reservoir and the spatial content of trace metals in them. Higher concentrations of elements were found in sediments collected from the agricultural catchment, whereas the lowest concentrations were observed near the outflow from the lake. The calculated RI value was 153.3, representing a moderate ecological threat risk. The concentration of cadmium had the greatest influence on the value of the indicator. The analysis of the scale of pollution of bottom sediments using the geochemical index showed that the bottom sediments in terms of the content of most of the trace metals tested are class II. In Cu and Zn, the Igeo index classified these deposits as class 0 and class I. The highest CF values were determined for Cr, Ni, and Pb and classified as significant contamination. The remaining elements were classified as moderately contaminated. The designated PLI was 2.49, suggesting immediate action to reduce pollution and prevent the degradation of the lake.

The Role of Oxygenated Functional Groups on Cadmium Removal using Pyrochar and Hydrochar Derived from Guadua angustifolia Residues

In the Ecuadorian Amazonia, there is a concern about the presence of high concentrations of cadmium (Cd) in rivers and sediments because of changes in land use and anthropogenic activities, e.g., mining and oil exploitation. Hence, the research related to water treatment processes to meet environmental standards has gained relevance. The use of biochar (BC) as adsorbent is considered a promising and low-cost alternative to improve the water quality in developing countries. In this work, lignocellulosic wastes from Guadua angustifolia were transformed through thermochemical treatments, into a promising carbonaceous material, such as BC. BC samples were prepared by pyrolysis (termed pyrochar, PC) and hydrothermal carbonization (termed hydrochar, HC). Their physicochemical properties were correlated with the Cd adsorption removal performance, analyzing the effect of adsorbent dosage, initial solution pH, adsorption kinetics and adsorption isotherms. HC showed the highest Cd adsorption performance, due to the presence of a higher number of oxygenated functional groups, as confirmed by FTIR, XPS and Raman spectroscopy. This research has proposed a sustainable alternative for the recovery of an available waste, contributing to mitigate the effects of the presence of metals on the health and economy of the most vulnerable sectors of society.

Distribution fractions and potential ecological risk assessment of heavy metals in mangrove sediments of the Greater Bay Area.

The restoration of mangrove in coastal wetlands of China has been started since the 1990s. However, various pollutants, especially for heavy metals (HMs), contained in wastewater might present a significant risk to mangrove forests during the restoration. In this study, sediments of five typical mangrove wetlands with varying restoration years and management measures in the Greater Bay Area were collected to evaluate the distribution fractions and potential ecological risk of HMs. Cd (0.2-1.6mg/kg) was found in high concentrations in the exchangeable fraction (37.8-71.5%), whereas Cu (54.2-94.8mg/kg), Zn (157.6-332.6mg/kg), Cr (57.7-113.6mg/kg), Pb (36.5-89.9mg/kg), and Ni (29.7-69.5mg/kg) primarily presented in residual fraction (30.8-91.9%). According to the geo-accumulation index (Igeo) analysis, sediment Cd presented a high level of pollution (3 ≤ Igeo ≤ 4), while Zn and Cu were associated with moderately pollution (1 ≤ Igeo ≤ 2). Besides, high ecological risk of Cd was found in sediments of five mangroves, with risk assessment code (RAC) ranging from 45.9 to 84.2. Redundancy analysis revealed that the content of NO3--N was closely related to that of HMs in sediments and, pH value and NO3--N concentration affected the distribution of HMs geochemical fractions. High concentration of HMs in QA and NS sampling sites was caused by the formerly pollutants discharge, resulting in these sediments still with a higher HM pollution level after the plant of mangrove for a long period. Fortunately, strict drainage standards for industrial activities in Shenzhen significantly availed for decreasing HMs contents in mangrove sediments. Therefore, future works on mangrove conversion and restoration should be linked to the water purification in the GBA.

Chemical speciation and bioavailability of potentially toxic elements in surface sediment from the Huaihe River, Anhui Province, China

In order to understand the characteristics of speciation and ecological risk of potentially toxic element (PTE) pollution in the surface sediment of huaihe river (Anhui province), 23 surface sediment samples were collected. The occurrence characteristics of PTEs (As, Cr, Zn, Cu, Cd, Pb, Mn) were analyzed by modified continuous extraction method (BCR), and the pollution status and potential ecological risk of PTEs were comprehensively evaluated by Pollution Load Index (PLI), Geoaccumulation Index (Igeo), Enrichment Factor (EF) and the risk assessment code (RAC). Results showed that the total concentrations of As, Mn, Cd, Cr, Cu, Pb, and Zn in sediment were 14.98 ± 2.32, 936.02 ± 144.48, 0.32 ± 0.08, 161.73 ± 124.83, 40.44 ± 9.67, 15.46 ± 6.67, and 74.85 ± 26.43 mg/kg, respectively. The mean concentrations of PTEs with the increasing order of Zn < Mn < Cr < Pb < Cu < As < Cd. Most PTEs appeared to mainly associate with a dominant proportion of residual fraction suggesting lower mobility whereas Cd and Mn presented a relative higher exchangeable fraction indicating a great degree of bioavailability and easily ingested by aquatic organism. Results of pollution degree showed that 3 sampling sites belong to the pollution degree of strong pollution, and the other sampling sites belonged to the medium pollution level. The indexes EF revealed moderately enrichment of Cr, minor enrichment of Cd, Mn and As, no enrichment of Cu, Zn and Pb. The values of the Igeo and RAC demonstrated that Cd and Mn pose a high ecological risk, which deserves further attention.

RISK ASSESSMENT, LEVELS, SPECIATION AND SEASONAL VARIATION OF HEAVY METALS (Cd and Cu) IN WATER AND PARTICLE SIZES OF SEDIMENTS FROM HUNKI OX-BOW LAKE, AWE LGA, NASARAWA STATE-NIGERIA

This research aimed at assessment of the levels, speciation, risk assessment indices and seasonal variation of heavy metals (Cd and Cu) in water and sediments from Hunki Ox-bow Lake in Awe L.G.A of Nasarawa State, using Atomic Absorption Spectrophotometer (AAS), during the dry and wet seasons. The mean concentration of Cd in water samples of both dry and wet seasons was higher than that of Cu, but Cu was higher than Cd on the whole (raw) sediment samples. The baseline levels of Cd and Cu in water samples (mg/L) were as follows: Cd (0.354) and Cu (0.014), which revealed that Cd level in water was higher than the WHO Guidelines for Drinking Water Quality. The baseline levels of Cd and Cu in sediment samples (mg/kg) were as follows: Cd (7.149) and Cu (8.363) which showed that Cd and Cu were lower than Interim Sediment Quality Guidelines – High of (Cd: 10 and Cu: 270 mg/kg). However, Cd level from sediment was higher than Interim Sediment Quality Guidelines – Low of 1.5 mg/kg but that of Cu was lower (65 mg/kg). Results of the Tessier five-step sequential extraction procedure indicated that Cd was more in the first four steps of the sequential extraction (non-residual) which accounted for 84.64 - 94.52 % in both seasons. Copper dominated more of the organic matter fraction of the sediments (48.17 – 85.54 %) for both dry and wet seasons. The mean of Bioavailability Index (BI) for wet season was relatively higher than that of dry season. The mean values of Mobility Factor (MF) revealed that Cd had higher values than Cu irrespective of seasons. This indicated that Cd was more mobilizable and bioavailable to this aquatic ecosystem compared to Cu. The geo-accumulation Index (I-geo) values of Cd showed practically unpolluted (sites 1, 2 and 5 of dry season), moderately polluted (sites 3 and 4 of dry season), heavily polluted (sites 1, 2, 4 and 5 of wet season) to very heavily polluted (site 3of wet season). The I-geo values of Cu indicated practically unpolluted. In dry season generally, Contamination Factor (Cf) values for Cd were all moderate in dry season. The Cf values of Cd indicated very high contamination factor for wet season, while that of Cu was low in both seasons. In both seasons, the ecological risk index (Er) of Cd in dry season had low to moderate ecological risk, and high to serious ecological risk in wet season. The Er values of Cu were low. This study revealed that: sediments and water samples of the dry season had lower concentration of Cd and Cu than in wet season; concentrations of Cd and Cu from sediments were more of manmade sources rather than natural sources and most ecological risk indices evaluated revealed that Cd had greater ecological risk.&#x0D;

Ecological risk assessment of trace metals in sediments and their effect on benthic organisms from the south coast of Zhejiang province, China

To explore the ecological risks of trace metals in sediments and their relationship with benthic organisms, 12 trace metals were analyzed and the macrobenthos were identified in the sediments collected from the south coast of Zhejiang province which belongs to the East China Sea. Spatially, the concentrations of most trace metals were high in the estuary, except for Ba and Sr. There was no obvious enrichment for trace metals, except that the concentration of Cd slightly exceeded the coastal background. The ecological risks calculated by the concentrations of Cr, Cd, Cu, Zn, Pb, and Ni in sediments showed that the methods based on sediment quality guidelines could judge the ecological risk more intuitively than the methods based on background value (PN, PLI, RI). The significant correlations between ecological risks and benthos density and biomass revealed the negative impact of trace metals at high concentrations on macrobenthic survival in sediments.