Cd In Sediments Research Articles

Spatial Variation, Ecological Risk, and Point Sources of Environmental Trace Metals in Lacustrine Ecosystems: An Assessment of Natural and Urban Inputs

ABSTRACT To gain insights into the spatial distribution, ecological risk and origins of heavy metals in surface sediments of lacustrine ecosystems in Cameroon, the content of 7 trace metals (Fe, Cr, Zn, Cu, Ni, Pb and Cd) in sediments from 60 sampling stations in 5 lacustrine environments of different formation contexts. The selected metals were investigated based on inductively coupled plasma mass spectrometry. The results revealed that the average concentrations of Cr, Cu and Cd were higher than the geochemical Threshold values. On the basis of the spatial variation, the studied metals vary quantitatively in the following order: Fe > Cr > Zn > Cu > Ni > Pb > Cd. The calculated enrichment factor (EF) and geo-accumulation index (Igeo) showed that, sediments from large cities and industrial sites had moderate enrichment (3 < EF ≤ 5) and were moderately to severely contaminated (2 < Igeo < 3) while those from low population and rural areas had minor enrichment (1 < EF ≤ 3) and were moderately contaminated (1 < Igeo < 2). With regards to cumulative pollution, the pollution load index (PLI) and the sediment pollution index (SPI) coupled with the potential ecological risk factor (Er) and the potential ecological risk index (RI), the sediments of the lakes are polluted (SPI and PLI > 1) to some extent but with a low ecological risk (Er < 40 and RI < 150). The results of Pearson correlation, principal component analysis (PCA), and cluster analysis (CA) identified three main sources: Ni would have a natural source; Pb from anthropogenic sources, and the other metals (Fe, Cr, Zn, Cu, and Cd) could have a mixed source (anthropogenic and natural). These findings serve as a scientific foundation for the advancement and use of these lake environments, which are the most attractive sites.

Origin, spatial distribution, sediment contamination, ecological and health risk evaluation of trace metals in sediments of ship breaking area of Bangladesh

Eleven trace metals (Cd, Cr, Fe, Mn, Cu, Ni, Co, Zn, As, Pb, and Ag) in sediments of Bangladesh’s ship breaking area were measured by an atomic absorption spectrometer to determine origin, contamination extent, spatial distributions, and associated ecological and human health hazards. This study found considerable quantities of Pb, Cd, Mn, Zn, and Cu when compared with standards and high levels of Pb, Cd, Zn, Cu, As, and Ag contamination according to pollution evaluation indices. Different indices indicate most of the sampling sites were highly polluted. However, spatial distribution maps indicate that trace metals were predominantly deposited in the northern and southern region. The ecological risk index revealed that Cd has the highest while Pb and As had moderate risk. Based on the health index values, Zn for both adults and children were higher than the safe limit while Mn, Pb, Cr, As, Fe, Cu, Ni, and Co for children were close to the threshold. The mean total carcinogenic risk values of Cr, As, and Ni for children and Ni for adults exceeded the permissible threshold. The cancer risk possibilities were further assessed using Monte Carlo simulation. Most trace metals have anthropogenic origins, which were attributed to ship breaking activities.

A methodology for evaluating the relative pollution level of metal pollution in surface sediments of rivers based on the statistical results of relevant literatures covering world-wide rivers

Due to the intervention of human activities, the background values of riverbed sediment exhibit spatiotemporal variability, which can affect the accuracy of risk assessment results. Using risk assessment that do not rely on background values is an executable alternative to avoid such problems. In this study, a relative pollution level assessment (RPLA) method which was based on the statistical results of relevant literatures was proposed. This method includes a four-step data processing procedure to extract the evaluation indexes of relative pollution degree of pollutants in environment and a series of relative pollution status assessment methods to evaluate the overall relative pollution level and regional difference of world-wide rivers. To demonstrate how to use RPLA method, 310 relevant literatures covering world-wide rivers were selected. And the ambient background value (x̅), the world-wide threshold values (WWTV) and the relative pollution grades (LEVEL I ∼ IV) of 9 target metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Sb and Tl) in riverbed surface sediments of world-wide rivers were extracted and used for evaluation. Moreover, the stability and applicability of RPLA method were evaluated. Results show that the evaluation results of RPLA method are robust and comparable with traditional evaluation method.

Comparison of metals in eelgrass (Zostera marina L.) and the environment across the North Pacific Ocean: Environmental processes drive source delivery

Seagrass beds play a critical role in biodiversity maintenance, serving as nursery habitats for fisheries, and aiding in carbon and sediment sequestration in the ecosystem. These habitats receive dissolved and particulate material inputs, like nutrients and heavy metals, affecting both plant health and the ecosystem. Eelgrass (Zostera marina L.), sediments, and water were randomly collected at twenty sites along the temperate North Pacific coasts of Asia and North America to assess heavy metals concentrations (Cr, Cu, Zn, Cd, and Pb). This aimed to understand heavy metal distribution and accumulation patterns in eelgrass tissues, revealing crucial factors influencing metal accumulation. The sampling included various areas, from pristine marine reserves to human-influenced zones, covering industrial, agricultural, and aquaculture regions, enabling a thorough analysis. This study's uniqueness lies in comparing heavy metal distributions in eelgrass tissues with sediments, uncovering unique accumulation patterns. Aboveground eelgrass tissues mainly accumulated Cd, Zn, and Cu, while belowground tissues stored Cr and Pb. Aboveground eelgrass tissues proved reliable in indicating Cd and Pb concentrations in sediments. However, the correlation between Cu, Zn, and Cr in eelgrass tissues and environmental concentrations seemed less direct, requiring further investigation into factors affecting metal accumulation in seagrass. Human activities are probable major contributors to heavy metal presence in Asian marine environments, whereas oceanographic processes serve as primary metal sources in North American Pacific estuaries. Critical discoveries emphasize the necessity for ongoing research on phytotoxic thresholds and in-depth studies on the complex connections between seagrass physiology and environmental metal concentrations. Understanding these dynamics is crucial for evaluating the broader impact of heavy metal pollution on coastal ecosystems and developing effective conservation measures.

Distribution and Concentration of Pb, Cd, and Hg Metals Due to Land Use Influence on Sediment in Malili River, East Luwu Regency

This research was conducted in the waters of Malili River, East Luwu Regency, with 4 observation points in Malili River East Luwu Regency, namely: (a) Southeast Sulawesi Sub Das (Point 1) namely Pongkeru village bridge, Coordinate point 12126.69’8°” E; (b) Larona Sub Das Karebbe basin bridge (Point 2), Coordinate point 12115.09’9°” E; (c) The meeting point of Larona sub-dash and Pongkeru sub-dash (Point 3), coordinate point 12159.64’8°” E; (d) Upper Malili River, Malili village, Malili bridge (Point 4), Coordinate point 12147.20’5°” E. Metal concentration and distribution were analyzed descriptively with the help of images (maps), graphs, and tables. Differences in Pb, Cd, and Hg metal concentrations in sediments between point locations were tested using analysis of variance (ANOVA) through the SPSS version 22 program. The relation between grain size, organic matter, and Pb, Cd, and Hg metal concentrations was tested using linear correlation. The results showed that the sediment content of Pb and Cd metal concentrations at each point location did not exceed NOAA (1999) quality standards. In the sediment, Hg metal concentration exceeds the quality standards of NOAA (1999) at each point, namely point 1. Pongkeru 0.590 μg.g-1, point 2. Karebbe 0.229 μg.g-1, point 3. Kawasule 0.514 μg.g-1 and point 4. Malili 0.358 μg.g-1. The relation between sediment size and Pb, Cd, and Hg metal concentrations at each point location has a weak correlation. The relation does not significantly affect the content of heavy metals in the sediment. It may be due to other factors, such as the source of heavy metal pollutants in each different point location. The relation between organic matter and the concentration of Pb, Cd, and Hg metals at each point location has a weak correlation. The relation does not significantly affect the content of heavy metals in the sediment because it may be due to other factors, such as different sources of heavy metal pollutants in each point location.

Spatial and seasonal variations, ecological and human risks of trace metals in major rivers within the oil producing zone of Nigeria

The concentrations of Mn, Fe, Cu, Zn, Pb, and Cd in sediments from Great Kwa, Calabar, Cross River, Imo, and Qua Iboe Rivers were investigated during the dry and wet seasons using standard techniques. Results indicated that the mean concentrations of all the metals were within their acceptable limits although; higher concentrations were obtained during the wet season. Cd was the major contaminant in the studied sediments; the ecological risks of all the metals except Cd were in the low class. The potential ecological risks of the metals were in the low and moderate categories during the dry and wet seasons, respectively. Sediments from Qua Iboe River exhibited very high human health risks for both seasons. Factor analysis revealed anthropogenic and natural factors as the major sources of these metals in sediments from the rivers investigated for both seasons. The estimated daily intake (EDI) rates of these metals via exposure to the studied sediments were within their recommended oral reference doses however; higher wet season values were recorded. The hazard index (HI) values of the trace metals were less than one (1) but, higher during the wet season. Pb and Cd were the major contributors to the total HI during the dry and wet seasons. The relative risk analysis for both seasons also confirmed Cd as the major human risk in the studied sediments. This research has exposed the levels of trace metals and their associated human risks in sediments from the rivers investigated.

A comparative study on the pollution status of heavy metals in soils and sediment from farmlands in Askira Uba, Nigeria

Heavy metals may enter the food chain from soil through mineralization by crops or environmental contamination, as in application of agricultural inputs such as pesticides and fertilizers or in the treatment of soils with sewage sludge cupper content of normal plant tissue. Atomic Absorption Spectroscopic (AAS) method is one of the most commonly used instrument in metal analysis due to its reproducibility of results, short analysis time, lower level of detection. Soil and sediments samples were collected at three distinct stations each, designated as A1, B1, C1 and A2, B2, C2 respectively from Askir/Uba local government area of Borno State, Nigeria. The concentrations of six heavy metals of environmental concern which includes Cd, Cu, Cr, Pb, Ni and Zn were determined by Atomic Absorption Spectrophotometer; Buck scientific model 210GP. The mean concentration of Cd in soil and sediment were (10.7±2.32 mg/kg and 9.62±2.32 mg/kg) and are of toxicological concern. The decrease in concentrations of the metals across sampling locations followed this order Cd &gt; Cu &gt; Cr &gt; Pb &gt; Ni &gt; Zn. The geoaccumulation index of the sediment by each metals are in the following increasing order: B2 &lt; A2 &lt; C2 for Cd and Pb, B2 &lt; C2 &lt; A2 for Cr, A2 &lt; B2 &lt; C2 for Cu, A2 &lt; B2 &lt; C2 for Zn respectively. In general, the order of metal contamination were Zn &lt; Ni &lt; Cu &lt; Pb &lt; Cr &lt; Cd. The results of the findings revealed that the soil and sediment were contaminated with Cadmium, the high level of Cd in the soil were above the recommended values. However, Independent-samples t-test (statically significant at p&lt;0.05) was used to compared the average metal composition in soil and sediment which showed that there was no significant difference on the composition in soil and sediment for all the metals p-value = 0.8939 The aim of the study was to compare the mean level of the soil and sediment with WHO permissible limit, hence evaluate their pollution status by the application of geoaccumulation index.

Simultaneous quantification of lead, cadmium and zinc in superficial marine sediments using a carbon-fiber microelectrode modified with bismuth film

Marine sediments are a useful environmental assessment matrix as they naturally trap toxic substances of anthropogenic origin and thus have higher concentrations of these than the surrounding water. Therefore, developing methods for the sensitive, accurate, and inexpensive quantification of these substances is important, as the traditional techniques have various disadvantages. The current study evaluated the effectiveness of an in situ bismuth-modified carbon-fiber microelectrode (voltamperometric sensor) to simultaneously detect Pb, Cd, and Zn in marine sediments from Puerto Jeli in El Oro Province, Ecuador. This site is representative of the contamination levels present along the coast in this province. Differential pulse anodic stripping voltammetry was applied, and the resulting linear regression for the metal quantification ranged from 12 to 50 μg mL−1, with quantification limits for Pb(II), Cd(II), and Zn(II) of 18.69, 12.55, and 19.29 μg mL−1, respectively. Thus, the quantification with the sensor was successful. According to the preliminary results, Cd and Pb values exceeded the permissible limits established by Ecuador (Texto Unificado de la Legislación Secundaria del Ministerio del Ambiente) and the US Environmental Protection Agency, respectively.

Comprehensive pollution and ecological risk of heavy metals in an industrial region of south-west Bangladesh

Deterioration of water, soil and sediment due to industrial operation is well known. This study aimed to evaluate physicochemical properties of surface water and heavy metals in industrial effluent (n = 13), river water (n = 14), pond water (n = 5), soil (n = 11) and sediment (n = 19) collected from an industrial zone in south-west Bangladesh. Among the physicochemical parameters, pH and dissolved oxygen (DO) indicated relatively higher values in most of the samples than their respective lower guideline values of 6 and 4.5 mg L-1 and showed significant variation across environments. Based on the average concentration, none of the heavy metals in any environment surpassed the guideline values in the study area, except, Cr in both industrial effluent (0.034 ± 0.055 mg L-1) and river water (0.011 ± 0.005 mg L-1), Cd in both soil (1.11 ± 0.47 mg kg−1) and sediment (1.41 ± 1.04 mg kg−1). Possibly, continuous discharge of industrial effluents might increase the heavy metal concentrations in the effluent receiving environment. Concentration of others heavy metals were below the respective guideline values but varied significantly among the environments. Depth-wise variation was negligible which might be dependent on metal chemistry in soil and sediment. A very high pollution and ecological risk were observed for Cd, specifically in soil and sediment. Multivariate statistics showed strong correlation among heavy metals, which indicated considerable contribution from industrial effluent. Industrial operations control physicochemical properties of surface water, but temperature is dependent of meteorological conditions. This study concludes that the lower concentrations of heavy metals than guideline values in environmental samples still pose significant levels of pollution and ecological risks.

Spatial and Temporal Distribution Characteristics of Heavy Metals in Main Rivers Sediments and Ecological Risk Assessment in Kaifeng City

Heavy metal pollution in urban river sediments is an important threat to river ecosystem health. To explore the temporal and spatial distribution characteristics of heavy metals in river sediments of Kaifeng City, the surface sediments of rivers were sampled in 2015 and 2021, respectively, and the contents of Cd, Cr, Cu, Ni, Pb, and Zn in sediments at different periods were compared. The heavy metal pollution in the two periods was evaluated using the indices of geo-accumulation, bio-toxicity risk assessment, and potential ecological risk. The results showed that the content of heavy metals in river sediments of Kaifeng City in 2021 were decreased significantly compared with that in 2015. Cd, Cr, Cu, Ni, Pb, and Zn decreased by 94.42%, 18.4%, 85.7%, 45.19%, 75.61%, and 92.28%, respectively. The heavy metal content in the Huafei River and Huiji River was higher than that in other rivers in both periods. Correlation and principal component analyses showed that the heavy metal pollution sources of river sediments in Kaifeng City were highly similar, and human activities such as industrial layout, road traffic, and land use were the main pollution sources. However, the results showed that the main pollutants were different between the two sampling times. In 2015, Cd, Cr, Pb, and Zn were the main pollutants, and in 2021, Cd, Cu, Pb, and Zn were the main pollutants. The results of the geo-accumulation, bio-toxicity risk assessment, and potential ecological risk indices showed that the temporal and spatial differences in heavy metal pollution in river sediments in Kaifeng City were large. However, the heavy metal pollution of the Huiji River and Huafei River was still serious, with contents in the medium and high pollution levels, especially to Cd. The heavy metal treatment of rivers in Kaifeng City has a long way to go, and it is particularly necessary to strengthen the engineering treatment for key river sections and effectively monitor key pollution elements.

Contamination and ecological risk assessment of Cr, As, Cd and Pb in water and sediment of the southeastern Bay of Bengal coast in a developing country

Safe levels of heavy metals in the surface water and sediment of the eastern Bay of Bengal coast have not been universally established. Current study characterized heavy metals such as arsenic (As), chromium (Cr), cadmium (Cd) and lead (Pb) in surface water and sediments of the most important fishing resource at the eastern Bay of Bengal coast, Bangladesh. Both water and sediment samples were analyzed using inductively coupled plasma mass spectrometer. Considering both of the seasons, the mean concentrations of Cr, As, Cd, and Pb in water samples were 33.25, 8.14, 0.48, and 21.14 μg/L, respectively and in sediment were 30.47, 4.48, 0.20, and 19.98 mg/kg, respectively. Heavy metals concentration in water samples surpassed the acceptable limits of usable water quality, indicating that water from this water resource is not safe for drinking, cooking, bathing, and any other uses. Enrichment factors also directed minor enrichment of heavy metals in sediment of the coast. Other indexes for ecological risk assessment such as pollution load index (PLI), contamination factor (CF), geoaccumulation index (Igeo), modified contamination degree (mCd), and potential ecological risk index (PERI) also indicated that sediment of the coastal watershed was low contamination. In-depth inventorying of heavy metals in both water and sediment of the study area are required to determine ecosystem health for holistic risk assessment and management.

Ecological risk assessment of heavy metals in the coastal sediment in the South-western Bay of Bengal

Dynamic coastal waters are often polluted by chemical pollutants, affecting coastal ecosystems. A total of four scientific coastal cruises up to 10 km offshore from the coastline along the Chennai-Puducherry coast during 2019-20 were conducted. This study examined the spatiotemporal distribution of heavy metals (Cr, Cu, Pb, Cd, Ni, Zn, As, Co, Mn) in the coastal sediments using various geochemical indices, including the Geo-accumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), and Ecological Risk Index (ERI), to understand the impacts, environmental risks, and pollution status in coastal and marine systems. The heavy metal concentrations of Cr, Cu, Pb, Cd, Ni, Zn, As, Co, and Mn in sediments are 16.48-74.70 μg/g, 2.01-3.78 μg/g, 1.37-17.54 μg/g, 0.20-21.76 μg/g, and 5.73-40.53 μg/g, 4.73-53.54 μg/g, 2.09-28.18 μg/g, 1.80-9.02 μg/g, 70.27-346.22 μg/g, respectively. The Igeo results revealed that none of the metals reached up to the contamination level except for Cd and As which showed a slightly contaminated level of the sediment. ERI indicated that coastal sediments are at moderate to high ecological risk from heavy metals. This study will help policymakers make informed decisions for combating or remediating metal pollution to safeguard the coastal environment.

Immobilization of cadmium in river sediments by different modified nanoscale zero-valent iron: performance, mechanisms, and Fe dissolution.

Modified nanoscale zero-valent iron (NZVI) exhibited great potential for the remediation of heavy metal contaminated river sediments, but its mechanisms and environmental risks are still unclear. This study systematically discussed the performance and the mechanisms of modified NZVI materials, i.e., sodium alginate-coated NZVI (SNZVI), rhamnolipid-coated NZVI (RNZVI), and graphene oxide-loaded NZVI (GNZVI), for the stabilization of Cd in sediment, with the exploration of their stability to Cd at various pH values and Fe dissolution rate. Compared with the control, the toxicity characteristic leaching procedure (TCLP) leachable Cd decreased by 52.66-96.28%, and the physiologically based extraction test (PBET) extractable Cd decreased by 44.68-70.21% after 56 days of incubation with the immobilization efficiency varying according to GNZVI > RNZVI > SNZVI > NZVI. Besides, the adsorption behavior of Cd on materials was fitted with the Freundlich model and classified as an endothermic, spontaneous, and chemical adsorption process. SEM-EDX, XRD, and FTIR results verified that the stabilization mechanisms of Cd were principally based on the adsorption, complexation of Cd2+ with secondary Fe minerals (including Fe2O3, γ-Fe2O3, and γ-FeOOH) and precipitation (Cd(OH)2). From the risk assessment results, it was observed that the materials were favorable for Cd stabilization at a pH range from 7 to 11, meanwhile, the leaching concentration of Fe in the overlying water was detected below the limit value. These findings pave the way to developing an effective strategy to remediate Cd contaminated river sediments.

Ecological and Human Health Risk Assessment of Heavy Metals in Sediment of Selected Creeks in Rivers State, Nigeria

There has been much concern about the rate at which industrial and household wastes are released into Creeks in Rivers State. The study examined the status of heavy metal pollutants (Cd, Cu, Zn, Cr, Pb, and Ni) in sediment and to determine the extent of damage caused by these human factors using the most recent pollution index and Sediment quality guidelines (SQGs). The research was carried out in four important creeks along the Delta River network in Rivers State, Nigeria (Okrika, Borokiri, Eagle Island, and Kaa). Triplicate sediment samples were collected at a depth of 0-20 cm and extracted with 20cm3 of aqua ragia (a 3:1 mixture of HCl and HNO3) and 10cm3 of 30% H2O2. The metal concentrations were measured using an Atomic Absorption Spectrophotometer (AAS). The concentrations of the heavy metals ranged from 11.147–18.919mg/kg, 11.918–14.379mg/kg, 8.321–11.691 mg/kg, 6.405–11.72mg/kg, and 5.718–12.125mg/kg, and 2.429-7.725mg/kg respectively and followed the sequence Zn &gt; Pb &gt; Cr &gt; Ni &gt;Cu &gt; Cd. Geo-accumulation Index (Igeo) calculated was less than 0 i.e. uncontaminated for all metals except Pb in Borokiri Creek and Cd in all sampled creeks, showing moderate contamination. Eco-toxicological risk assessment (RI) indicated that the creeks were uncontaminated. Despite the low level of contamination, it is recommended that relevant authorities to regulate the indiscriminate dumping of domestic waste and untreated industrial effluents into the river to prevent the deterioration of the creeks

Spatial-temporal Variations and Pollution Assessment of Heavy Metals in Sediments of Qionghai Lake in Xichang City

Based on the analysis of the total concentrations of 10 metals in the sediment core and total concentrations and chemical fractions of seven metals in the surface sediments of Qionghai Lake in Xichang City, Sichuan Province, the spatial-temporal characteristics of metal accumulation and pollution over the past century and the potential ecological risk of metals in surface sediments were studied. Before the 1970s, metal concentrations in the sediment core were stable. The total concentrations of Al, Fe, K, and Cr in the sediment core exhibited visible peaks in the 1970s, which were related to the enhanced input of fine-grained topsoil caused by increasing precipitation, lake reclamation, and deforestation. Since the 1990s, the total concentrations of Al, Fe, K, and Cr decreased with the reduced topsoil erosion, whereas the total concentrations of As, Cd, Cu, Pb, and Zn gradually increased or remained stable. The enrichment factor results showed that Cd, Pb, and Zn were the main contaminants, with Cd as the typical contaminant in the sediment core. The Cd contamination started in the 1960s and has remained at a moderate level since the 1990s. In the surface sediments, the total concentrations of Cd were higher in the northwest lake area, and no visible spatial concentration trends of the other metals were displayed. The bioavailable fractions of Cd, Pb, and Zn accounted for 95%, 63%, and 48% of the total metal concentrations on average. Among the bioavailable fractions, Cd was mainly in the acid-soluble fraction, and Pb and Zn were mainly in the reducible and oxidized fractions. The bioavailable fractions of the other metals were less than 27%. The results of total concentrations and bioavailable fractions of metals revealed that Pb and Zn in the surface sediments were slightly or moderately contaminated, and Cd was moderately contaminated on average. Cd contamination was at a severe level in the northwest lake area. The concentrations of anthropogenic Cd, Pb, and Zn in the surface sediments estimated from the total and bioavailable concentrations were comparable (P>0.05), indicating that anthropogenic metals primarily existed in bioavailable fractions in the sediment. Integrating the assessment results from sediment quality guidelines, potential ecological risk index, and chemical forms of metals, Cd in surface sediments may pose a high ecological risk, whereas the other metals has a low ecological risk.

Comprehensive geochemical assessment, probable ecological and human health risks of heavy metals in water and sediments from dredged and non-dredged Rivers in Lagos, Nigeria

The study was conducted to demystify the geochemical distributions of heavy metals in water and sediments from dredged and non-dredged riverine systems, with a view to ascertain the source, and the deleterious ecological and human health risks of these metals. Ojo and Badagry Rivers were considered as the dredge-mined sites, while Gbaji River was chosen as the non-mined site. The level of heavy metals in water samples are as follows; [Cd (0.040 – 0.360), Cu (0.010 – 0.130), Cr (0.001 – 0.080), Fe (0.170 – 1.040), Pb (0.001 – 0.050), Mn (0.050 – 0.230–), Zn (0.050 – 0.160), As (0.001 – 0.030), Co (0.003 – 0.040) and Ni (0.001 – 0.050) mg/L]. The Cd and Mn contents in the water from the mined sites were higher than their permissible limits. The heavy metal contents [Cd (0.190 – 1.490), Cu (1.390 – 5.950), Cr (1.180 – 2.630), Fe (144.820 – 261.490), Pb (1.960 – 24.250), Mn (5.170 to 24.110), Zn (5.180 – 35.420), As (0.170 – 0.690), Co (0.190 – 0.840) and Ni (0.740 – 2.140) mg/kg] in sediments are within the background levels, except for Cd from the mined sites. The hazard index was lower than 1 (HI ≤ 1), inferring no likelihood of non-carcinogenic incidents. Contrarily, the outcome of the cancer risk index revealed that exposure to sediments from the mined sites could lead to cancer risk. The contamination and enrichment factors of the sediments from mined sites showed “high contamination” and “extremely enriched,” respectively. Notably, the potential ecological risk index of Cd (high) in sediments from the mined areas contribute significantly to the ultra-high risk of these ecosystems, which might result in ecological collapse of the riverine systems. The calculated Nemerow multifactor index (YN) values of the mined sites implies extreme pollution. The coefficient of variation (CV), Pearson's correlation matrix, and principal component analysis (PCA) clearly indicate that heavy metals in water and sediments are from multiple rather than a single source. Although this study could not ascertain whether the mining activities are solely responsible for the elevated heavy metals in water and sediments from the dredge-mined sites since the study sites frequently experience other anthropogenic activities, the study showed that significant pollution and ecological adversities are associated with water and sediment from the dredged-mined sites.

Nutrients in overlying water affect the environmental behavior of heavy metals in coastal sediments

Excessive nutrients in aquatic ecosystems are the main driving factors for eutrophication and water quality deterioration. However, the influence of nutrients in overlying water on sediment heavy metals is not well understood. In this study, the effects of nitrate nitrogen (NO3–N) addition and phosphate addition in the overlying water on the environmental behaviors of chromium (Cr), copper (Cu), and cadmium (Cd) in coastal river sediments were investigated. Fresh estuary sediments and synthetic saltwater were used in microcosm studies conducted for 13 d. To determine the biological effect, unsterilized and sterilized treatments were considered. The results showed that the diffusion of Cr and Cu was inhibited in the unsterilized treatments with increased NO3–N. However, under the NO3–N sterilized treatments, Cr and Cu concentrations in the overlying water increased. This was mostly related to changes in the microbial regulation of dissolved organic carbon and pH in the unsterilized treatments. Further, in the unsterilized treatments, NO3–N addition considerably increased the concentrations of the acid-soluble (Cr, Cu, and Cd increased by 5%–8%, 29%–41%, and 31%–42%, respectively) and oxidizable (Cr, Cu, and Cd increased by 10%, 5%, and 14%, respectively) fractions. Additionally, compared with that in the unsterilized treatments, Cu and Cd concentrations in P-3 treatments decreased by 7% and 63%, respectively. By producing stable metal ions, microorganisms reduced the amount of unstable heavy metals in the sediment and heavy metal concentration in the overlying water, by considerably enhancing the binding ability of phosphate and heavy metal ions. This study provides a theoretical basis for investigating the coupling mechanisms between heavy metals and nutrients.

Internal nutrients dominate load and drive hypoxia in a eutrophic estuary.

The hypothesis that local hypoxia and chlorophyll concentration are spatially tethered to local, sediment-driven nutrient release was examined in a small, nutrient-impacted estuary in the Southern Gulf of St. Lawrence, Canada. Sediment reactor core samples were taken at 10 locations between 0.25 and 100% of the estuary area in spring and fall (2019) and used to estimate nitrogen and phosphate flux. Sediment organic matter, carbonate, percent nitrogen, percent carbon, δ13C, and δ15N were measured from the reactor core stations. Oxygen was recorded continually using oxygen loggers while chlorophyll and salinity were measured bi-weekly. A hydrodynamic model was used to determine water renewal time at each station. The most severe eutrophication effects were in the upper one-fifth of the estuary. There were strong local relationships between sediment biogeochemistry, hypoxia, and chlorophyll metrics but not with water renewal time. Internal nutrient loading represented 65% and 69% of total N loading, and 98% and 89% of total P loading to the estuary in June and September, respectively. Sediment nitrogen flux was highly predictable from a range of local sediment variables that reflect either nutrient content, or organic carbon enrichment in general. Percent nitrogen and percent carbon were highly correlated but sediment P flux was poorly predicted from sediment parameters examined. The highest correlations were with percent nitrogen and percent carbon. These results indicate that incorporating internal nutrient loading into nutrient monitoring programs is a critical next step to improve predictive capacity for eutrophication endpoints and to mitigate nutrient effects.

Determination of some heavy metal concentrations in water and sediment of River Gidin Dorowa, at Gidin Dorowa, Taraba, North Eastern Nigeria

This study examined some heavy metal concentrations in water and sediment of River Gidin Dorowa, Taraba, North Eastern, Nigeria. It was examined with atomic absorption spectrophometer (AAS) buck scientific model 210 VGP. Mean concentrations of metals in water and sediment showed significant (p&lt; 0.05) during the study period between September, 2022 to February, 2023. Samples were collected upstream and downstream at River Gidin Dorowa. Higher mean value (0.3087 mg/l) was reported for lead (Pb) in October compare to other metals with lower value (0.1647 mg/l) recorded in November. Zinc (Zn) recorded higher value (0.1334 mg/l) in September. Cadmium (Cd) recorded higher value (0.0170 mg/l) in September and lower value (0.0027 mg/l) in February. Heavy metals in sediment showed variation (p&lt;0.05) between metal during the study. Cadmium recorded higher value (0.0154 mg/kg) in December and lower value (0.0087 mg/kg) in January. Lead (Pb) value (0.6380 mg/kg) was higher in January while lower value (0.3707 mg/kg) were observed in October and November. Zinc (Zn) recorded a higher mean value (1.6667 mg/kg) in October. Copper value showed higher variation (0.4000 mg/kg) in October and lower value (0.2667 mg/kg) in February. Monthly variation between water and sediment during the study period showed higher variation (0.3910 mg/kg) for Lead (Pb) in the sediment and water value (0.2880 mg/l) in September. Copper (Cu) value (0.1000 mg/l) in water was lower than values in the sediment. Mean Cadmium value for water (0.0027 mg/l) and value (0.0100mg/kg) in sediment showed variations (p&lt;0.05) in February from other metals considered. The levels of Zn, Cu, and Cd in water and sediment at Gidin Dorowa for this study were generally low compared to safe limits recommended by WHO and USEPA except values of Lead (Pb) in water. Therefore, routine monitoring of the heavy metals’ concentrations in water and sediments of River Gidin Dorowa should be sustained.

High-resolution record of temporal change in organic matter burial over the past ∼8,600 years on the northwestern continental slope of the South China Sea

Sedimentary organic matter (SOM) on continental slopes in marine regions can sensitively record climatic and environmental changes. In this study, total organic carbon content (TOC), total nitrogen content (TN), and their stable isotope compositions (δ13C and δ15N) for sediments of core G02 were investigated (at ∼24.2-year resolution) to reveal the temporal variations in organic matter sources and the main controls on the sources and distribution of buried organic matter on the northwestern continental slope of the South China Sea over the last ∼8600 years. Results of a δ13C binary mixing model reveal that ∼82.3 ± 3% of SOM is derived from marine autochthonous sources. We suggest that the carbon and nitrogen contents and compositions of SOM are governed by distinct factors. The more positive δ15N values before the Pulleniatina Minimum Event occurrence are ascribed to stronger subsurface water intrusion by the Kuroshio Current, which led to enhanced subsurface denitrification and in turn counteracted the effect of mixing with surface water caused by the East Asian winter monsoon. Sedimentary δ13C values show a fluctuant decrease during ca. 8.6–3.0 cal kyr BP and a conspicuous increase during ca. 3.0–1.4 cal kyr BP. These changes are attributed to the decrease of marine productivity induced by the continuous weakening East Asian monsoon effect and the decrease of terrigenous organic carbon input induced by the weakened Indian summer monsoon precipitation, respectively. Since ca. 1.4 cal kyr BP, human activities have become the dominant factor in controlling the production and distribution of organic carbon. The results provide an important basis for understanding of source-sink processes of organic matter and the factors influencing these processes on continental slopes in low-latitude marginal seas.