Metal Concentrations In Sediments Research Articles

Assessment of some heavy metal content in sediments of a mangrove swamp, niger delta, nigeria using applicable ecological risk indices

Sediments can act as pollutant sinks and a source of pollution in aquatic environments. The surface sediments of the Isaka–Bundu tidal swamp, Niger Delta was assessed for heavy metal content using standard methods and assessment indices. The study was carried out in three stations between January and June 2022. Five heavy metals (lead, copper, cadmium, nickel and zinc) were evaluated while eight assessment indices (Contamination Factor - CF, degree of contamination - DC, Ecological Risk - Er, Potential Ecological Risk - PERI, Pollution Load Index - PLI, Enrichment Factor - EF, Geo-accumulation Index - Igeo and Quantification of Contamination -QoC) were applied. Results showed that cadmium and copper exceeded permissible limits while lead, zinc and nickel were within limits. Stations 1 and 3 recorded significantly higher values indicating anthropogenic influence. The dominant anthropogenic activities observed in the area include maritime and dockyard activities and artisanal crude oil refinery. The assessment indices showed that the sediments were at various levels of heavy metal pollution mainly influenced by copper and cadmium viz: CF: Cu (considerable degree) and Cd (very high degree), DC (very high degree), Er: Cd (high ecological risk) and Cu (very high ecological risk), PERI (significant high ecological risk), PLI (very high level pollution), EF: Pb, Zn, Cu (Station 1) and all Cd (extremely high enrichment), Igeo: Cd (extremely polluted) and QoC: Cu and Cd (anthropogenic source). The sediments were highly polluted with toxic metals, which is detrimental to humans and aquatic biota.Keywords: Heavy metal; Indices; Mangrove; Niger Delta; Sediment.

Comparison of leaching behaviour of heavy metals from sediments sampled in sewer systems - environmental and public health aspect.

The article analyzes the content of heavy metals and standard physical as well as chemical pollution indicators in different types of sediments from stormwater, combined sewer and sanitary sewer systems. Nickel, lead, chromium, copper, zinc and cadmium, as well as standard physical and chemical pollution indicators, were determined in sewage sediments. Aqueous extracts of sediments samples, taken from storm water sewer inlet sediments traps, storm sewers, sanitary sewers and combined sewers, were prepared in accordance with PN-EN 12457-2:2006. After mineralization, the concentrations of the metals: nickel, lead, chromium, copper, zinc and cadmium in the extracts were determined using the inductively coupled plasma emission spectroscopy technique. The results were analyzed with a non-metric multidimensional scaling algorithm. The heavy metal content was variable depending on the sediments collection site. The heavy metals nickel, lead, chromium, copper, zinc and cadmium were found in the sediments from stormwater inlets, storm sewer and sanitary sewer channels, with variability in the concentration of individual metals. The sediments from the flushing of sanitary sewers and combined sewers did not contain cadmium. The content of heavy metals in sediments varied depending on the sampling location and type of sewer system, indicating the need for detailed monitoring to identify the sources of emissions. Sediments from stormwater sewers have higher concentrations of heavy metals, with those from sewer inlets showing zinc concentrations exceeding regulatory limits, highlighting the variability and potential environmental impact of different sewer systems.

Assessment of heavy metal content and ecological risk in offshore surface sediments of the Northern Persian Gulf: Implications for environmental management

Offshore surface sediment samples from fifty-five stations in the northern parts of the Persian Gulf and the Strait of Hormuz were examined to evaluate the content and ecological risk of heavy metals. The physicochemical characteristics of both surface water and deep water were measured using probes and CTD. To determine the source of pollution and assess the ecological risk, various indicators were used, including contamination factor (CF), contamination degree (CD), enrichment factor (EF), pollution load index (PLI), and risk index (RI). The average concentrations of heavy metals in sediment samples were Fe: 1.4 (0.2–2.7%), Cr: 72.9 (8−127), Ni: 59.8 (14−113), V: 43.4 (7−77), Zn: 35.7 (3−58), Cu: 17.5 (2−29), Pb: 12.1 (5−48), Co: 9.4 (1−17), As: 3.9 (1.7–7.2) ppm. Ni and Cr concentrations in almost all Persian Gulf stations especially in shallower parts were higher than their threshold effect level, while Pb, As, Zn, and Cu concentrations were below the threshold values in all stations. The results revealed that EF for all investigated metals in all stations was less than 1.5, which indicates that the studied region had low enrichment and the origin of the heavy metals is natural. However, human activities have contributed to Ni enrichment in the Jask and Bandar Abbas coasts. CD values varied between 11.7 and 14.6, exhibiting the range of moderate pollution to lowest possible pollution category. The PLI for all samples was in the range of 1.2–2.2, which demonstrates advanced pollution load. RI (=∑Eij) varied between 34 and 89, indicating a low ecological risk (IR<110).

Seasonal benthic species composition linked to coastal defense structures (CDS) in Kuala Nerus, Terengganu, Malaysia.

The natural hydrodynamic process of Kuala Nerus, Terengganu, has changed since the extension of Sultan Mahmud Airport runway in 2008. Consequently, severe coastal erosion has occurred in the area, particularly during the northeast monsoon season (NEM). Numerous types of coastal defense structures (CDS) have been constructed to protect the coastline. Despite the loss of esthetic values, the effect of CDS construction on marine organisms in the area remains unknown. Hence, this study aims to assess the ecological aspects of macrobenthic compositions at the CDS area of Kuala Nerus, Terengganu, based on the differences between the southwest (SWM) and northeast (NEM) monsoon seasons. Macrobenthos were collected from the sediment in July (SWM) and December 2021 (NEM) using the Ponar grab at 12 substations from five sampling stations. The density of macrobenthos was higher in SWM (48,190.82 ind./m2) than in NEM (24,504.83 ind./m2), with phylum Mollusca recording the highest species composition (60-99.3%). The macrobenthos species had a low to moderate level of diversity (H' = 1.4-3.1) with the species were almost evenly distributed (J' = 0.2-0.8). Windward substations exhibited coarser grain sizes (38.56%-86.84%), whereas landward substations exhibited very fine grain sizes (44.26%-86.70%). The SWM season recorded a higher organic matter content (1.6%-6.33%) than the NEM season (0.4%-3.1%). However, metal concentrations in the surface sediment were within the safe range and permissible limits for both seasons, inferring that the macrobenthos composition was unaffected. This study demonstrated that the CDS associated with the monsoon system has controlled the hydrodynamics and nearshore sedimentary processes in the Kuala Nerus coastal zone, thereby affecting the macrobenthos population, in terms of richness and density. The ecological and energetic effects of the coastal structures in different seasons have resulted in a more significant result, with the SWM exhibiting a higher macrobenthos composition than the NEM.

Chemical characteristics with attention on toxic metals content in sediments of the urban tropical ecosystem Río Almendares, Havana, Cuba: Pollution risk assessment

Anthropogenic disturbances have dramatically impacted surface water quality worldwide. There is no restriction placed on waste disposal in developing countries, so micropollutants, including metals, are of major concern to soil and water. A tropical river ecosystem was selected as a model for this study: Almendares River (Havana, Cuba). We investigated the occurrence of 15 toxic metals in surface sediment for ecological risk analysis. Results indicated that sediments of a silty loam type had higher concentrations of four metals (Cr concentration range: 3.59–7.35 mg kg−1, Cu: 6.23–14.82 mg kg−1, Zn: 22.64–27.40 mg kg−1, and Pb:3.85–6.72 mg kg−1), than Cuban norms. Further, the contamination indices including Enrichment Factor (EF), Geo-accumulation, Contamination Factor, Contamination Degree, Ecological Risk Factor and Potential Ecological Risk were calculated. 10 elements presented significant enrichment at the sampling stations of the 15 metals examined; Zn, Cd, Pb, Cu, and Ag had the highest EF values. Anthropogenic activities and polymetallic contamination could be the main source of these five heavy metals. The correlation analysis revealed that domestic, agricultural, and industrial sources were the main sources of contamination, along with an unregulated landfill. In terms of the extent of metal contamination in the urban site (Zone II) of Almendares River, this study constitutes the most comprehensive and extensive. The study contributes to the knowledge of the region and is crucial for the sustainable management of the Almendares River. There must be efforts made to control metal pollution in this river and ensure that metal levels are monitored.

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.

Environmental assessment of heavy metal contamination at Chekfa aggregate quarry (Jijel, North‐East Algeria)

AbstractIt is fascinating to observe the potential hazards associated with mining and quarrying activities, despite the limited number of comprehensive studies conducted in Algeria to evaluate their environmental impact. This particular investigation focuses on El M'cif quarry in Chekfa, located within the Nil watershed in Jijel, a region situated in the North‐East of Algeria. The primary objective is to assess the concentrations of lead (Pb), zinc (Zn), copper (Cu), and cadmium (Cd) in surface water, groundwater, stream sediments, and soil. Consequently, a suite of petrographic and geochemical analyses is undertaken to discern the origins of these heavy metals. Employing statistical methodologies, notably the Geo‐accumulation Index (Igeo), Pollution Index (PI+PI), and Ecological Risk Assessment (ER), this study is further fortified to quantify the levels of hazardous contaminants. The findings reveal that the concentrations of Cd and Pb in surface water are recorded at 22 and 654.3 μg/L, respectively, surpassing both Algerian and WHO standards. Meanwhile, the heavy metal concentrations in stream sediments are ranked in the order of Zn &gt; Cu &gt; Cd, with respectively mean concentrations of 1085.30, 14.60, and 1.49 (mg/kg). The mean concentrations of Zn, Pb, Cd, and Cu in soil are measured respectively at 219.78, 128.86, 20.76, and 2.42 (mg/kg). Based on the statistical methods such as I‐geo, PI, IPI, and RI, the research reveals that the sediments of the Aftis River are uncontaminated by Cu, moderately to heavily contaminated with Zn and heavily contaminated by Cd. Besides the soil samples which are found to be extremely contaminated with Cd, moderately contaminated with Pb, and uncontaminated with Cu and Zn. Additionally, the X‐ray fluorescence analysis reveals that the limestone extracted from the quarry contains 0.7% cadmium, suggesting that the quarry could potentially contribute to cadmium contamination. The surrounding rocks exhibit significant concentrations of iron, lead, and zinc. Therefore, the elevated levels of these heavy metals can primarily be attributed to geological factors rather than human activities, highlighting the combined influence of the extractive industry and the geological environment.

Removal of toxic metals using iron sulfide particles: A brief overview of modifications and mechanisms

Growing mechanization has released higher concentrations of toxic metals in water and sediment, which is a critical concern for the environment and human health. Recent studies show that naturally occurring and synthetic iron sulfide particles are efficient at removing these hazardous pollutants. This review seeks to provide a concise summary of the evolution in the production of iron sulfide particles, specifically nanoparticles, through the years. This review presents an outline of the synthesis process for the most dominant forms of iron sulfide: mackinawite (FeS), pyrite (FeS2), pyrrhotite (Fe1-x S), and greigite (Fe3S4). The review confirms that both natural forms of iron sulfide and modified forms of iron sulfide are highly effective at removing different heavy metals and metalloids from water. Concurrently, this review reveals the interaction mechanism between toxic metals and iron sulfide, along with the impact of conditions for remedy and rectification. None the less, modifications and future investigations into the synthesis of novel iron sulfides, their use to adsorb diverse environmental pollutants, and their fate after injection into polluted aquifers, remain crucial to maximizing pollution control.

Heavy metal content in estuaries water and sediment of Banten Bay, Indonesia

The primary economic activity in the estuaries of Banten Bay is fisheries. To maintain their productivity, it is essential to ensure good water quality, which requires monitoring of heavy metal content in both water and sediment. Therefore, this research aimed to investigate heavy metal content in estuaries’ water and sediment of Banten Bay. A survey was conducted in four estuaries, namely Karangantu, Wadas, Cengkok, and Pamong. Heavy metal content in estuaries water was analyzed in April and October 2021, while heavy metal content in estuaries sediment was analyzed in October 2021. Other parameters were analyzed in the laboratory or in situ. The analysis showed that the lead (Pb) content in the estuaries’ water exceeded the standard in April but met the standard in October, while the iron (Fe) and cadmium (Cd) content in the water fulfilled the standard in both months. The Pb, Fe, and Cd content in the estuaries’ sediment also met the standard. The Principal Component Analysis (PCA) indicated that the Pb content in the water was influenced by organic carbon (C organic), while the Cd content was affected by total suspended solids (TSS), oxidation-reduction potential (ORP), salinity, and water depth. Furthermore, the Pb and Fe content in the sediment was influenced by pH, while the Cd content was affected by C organic.

The use of marine sponge species as a bioindicator to monitor metal pollution in Red Sea, Saudi Arabia

The existing data on trace elements of benthic sea organisms is scarce. Yet, the pressing issue of environmental contamination has spurred a surge in the use of organisms as biomonitors. In this study, sediment cores were sampled with the sponges, and metal concentrations were determined in both samples using ICP-MS. The mean concentrations of metals in benthic sediments and sponge species analyzed in this study differed significantly (Sediment >Phorbas species > Negombata magnifica > Callyspongia species > Amphimedon chloros). This could be due to the varying capacity of each sponge species to accumulate a particular metal by different means. Negombata magnifica and Phorbas species appear to be indicators, accumulators, or hyper-accumulators of Cu and Mn, while Callyspongia species is an indicator, accumulator, or hyper-accumulator of Cu only due to bioconcentration factor > 1 for the aforementioned metals. Concentrations of Cu and As in sediment were below the Effects Range Median but above the Effects Range Low threshold, hence the need to give more attention to these metals. This research provides a baseline dataset for designing monitoring strategies on this ecosystem and using sponge species for biomonitoring.

Metal and non–metal dynamics and distribution in soil profiles across selected pans in the Ramsar declared subtropical within a national protected area

ABSTRACT The study investigated the spatial distributions of selected metals, semi–metals and non–metals within a floodplain pan ecosystem in the Ramsar declared Makuleke Wetlands within the Makuleke Contractual National Park, in the northern Kruger National Park (South Africa), along varying soil depths (0–120 cm) at 20 cm intervals. The study identified significant differences in metal concentrations (i.e. Ca, Mn, Fe) and non–metals (i.e. C, S) across sediment depths. Metal and non–metal concentrations in surface sediments (0–40 cm) were generally high. Compared with the sediment quality guidelines, all measured metals were within the ‘no effect’ level across different sites and depths, except for one site (i.e. Mambvumbvanyi pan). In contrast, enrichment factors showed that K, Ca and Mg were enriched in sediments across all the floodplain pans and depths. Principal component and cluster analyses indicated that various metals originated from different sources. Although a high concentration of metals was found in the topsoil, no potential detrimental effects on the aquatic systems could be observed. Based on the findings, this study provides a baseline overview of sediment metal pollution that can inform effective management of these floodplain wetlands systems.

Assessment of Water and Stream Sediment Pollution Related to Artisanal Mining in Alga, Burkina Faso, West Africa

Burkina Faso, like several other countries in the Sahelo-Sahelian strip, has seen a significant change in its mining sector in recent years through the development of the industrial and artisanal mining sub-sectors. The purpose of this study is to assess the level of pollution of water and stream sediments in the study area. A total of twenty-eight samples were taken, including three surface water samples, nine groundwater samples, ten stream sediment samples and six mine tailings samples. The analysis of the physico-chemical parameters and the metal content (cadmium, chrome, copper, mercury, nickel, lead, zinc and arsenic) of the water show that the values meet the drinking water standards in force in Burkina Faso. However, the various indices calculated, namely the geo-accumulation index (Igeo), the contamination factor (CF) and the enrichment factor (EF) show that the total metal contents of stream sediments are not d lithogenic (natural) origin but attributable to artisanal mining in the village of Alga. They highlight metal pollution with high levels of arsenic and cadmium and extremely high levels of mercury.

Distribution, Sources, and Ecological Risk Evaluation of Heavy Metals in Surface Sediments of Taihu Lake

For the surface sediment samples of Taihu Lake in 2010, the eight physicochemical indices of pH, temperature, Eh, water content, porosity, grain size, total phosphorus, and Loss-on-ignition were measured and analyzed, along with the contents of nine heavy metals:Cu, Zn, Ni, Cr, Pb, Ba, Mn, Co, and V. The order of magnitudes of heavy metal content of surface sediments in Taihu Lake was:Mn>Ba>Zn>Cr>V>Ni>Pb>Cu>Co. This suggested that the contents of the nine heavy metals were beyond the background value, which had a close connection to the geology of the Taihu Lake Basin and were influenced by human activity to varying degrees. The clustering analysis and the spatial distribution of the heavy metals revealed that the concentrations of heavy metals in the North and South Taihu Lake sections decreased from the lake shore to the lake center, the concentrations of heavy metals in the West Taihu Lake section increased from the lake shore to the lake center, and the distribution of heavy metals in the center of the lake remained relatively uniform. According to the correlation study, the metal elements were positively correlated with one another to varying degrees, indicating that they originate from the same source of pollution. According to the PCA and PMF analyses, there were some different sources of heavy metals in Taihu Lake, in which the transportation and industrial complex source were the most important sources, the diagenesis was the second major source, and agriculture was the third major source. Furthermore, the heavy metal pollution was evaluated using the geoaccumulation and the potential ecological risk indices. This offers a solid theoretical backing for the future management of heavy metal pollution in Taihu Lake.

Content of metals in bottom sediments of rivers and lakes of the Tyumen region

Content of metals in bottom sediments of rivers and lakes of the Tyumen region

Trace metal content prediction along an AMD (acid mine drainage)-contaminated stream draining a coal mine using VNIR–SWIR spectroscopy

The current study investigated the use of VNIR–SWIR (visible/near infrared to short-wavelength infrared: 400–2500 nm) spectroscopy for predicting trace metals in overbank sediments collected in the study site. Here, we (i) derived spectral absorption feature parameters (SAFPs) from measured ground spectra for correlation with trace metal (Pb, Cd, As, and Cu) contents in overbank sediments, (ii) built univariate regression models to predict trace metal concentrations using the SAFPs, and (iii) evaluated the predictive capacities of the regression models. The derived SAFPs associated with goethite in overbank sediments were Depth433b, Asym433b, and Width433b, and those associated with kaolinite in overbank sediments were Depth1366b, Asym1366b, Width1366b, Depth2208b, Asym2208b, and Width2208b. Cadmium in the overbank sediments showed the strongest correlations with the goethite-related SAFPs, whereas Pb, As, and Cu showed strong correlations with goethite- and kaolinite-related SAFPs. The best predictive models were obtained for Cu (R2 = 0.73, SEE = 0.15) and Pb (R2 = 0.73, SEE = 0.21), while weaker models were obtained for As (R2 = 0.46, SEE = 0.31) and Cd (R2 = 0.17, SEE = 0.81). The results suggest that trace metals can be predicted indirectly using the SAFPs associated with goethite and kaolinite. This is an important benefit of VNIR–SWIR spectroscopy considering the difficulty in analyzing “trace” metal concentrations, on large scales, using conventional geochemical methods.

Distribution of heavy metals in water and sediment at the Bojonegara nearshore of Banten Bay, Indonesia

Heavy metals released to a nearshore environment may vary due to contaminant sources and the seasonally coastal processes. This study revealed how the seasonal variability and potential sources controlled the distribution pattern of several heavy metals and the level of water quality in Bojonegara nearshore of Banten Bay. The water and sediment samples were collected once in January, February, August, September, and October 2020 at six stations representing the river and sea. Heavy metal was determined using the APHA procedure. Cu was detected in August-October, ranging from <0.002 – 0.008 mg/L. The concentrations of Cu, Cd, and Pb in the sediment were detected, varying from <0.02 to 3.90 mg/kg, <0.02-1.68 mg/kg, and <0.02-6.71 mg/kg, respectively. The concentrations of the concerned metals in sediment vary, and their distribution pattern change seasonally. These metals in water and sediments were still safe for the environment and marine biota. This study suggests how contaminant sources and coastal processes could control the contaminant level. In addition, potential sources of heavy metal merely derived from onshore of the Bojonegara, but it could be derived from advection from other areas through the coastal processes.

Provenance and Pollution Status of River Sediments in the Danube Watershed in Serbia

Heavy metals as environmental pollutants can have natural or anthropogenic origin. To determine the river sediment pollution status, it is crucial to have appropriate reference samples, free of anthropogenic impact, and natural reference samples should be used wherever and whenever possible. The collection of reference samples should be performed in the vicinity of the research area in a place that belongs to the same geological environment and is undisturbed by human activity. The main purpose of this study was to compare concentrations of heavy metals from different rivers with background values to show that the usage of natural background values is the best option when assessing pollution status, but also to underline that the natural background values have to correspond to the analyzed sediments. In this study, 5 river sediments from Sava, 17 from Great War Island (GWI), 11 from Danube, 24 from Tisa, 47 from Tamiš, and 11 from Timok were evaluated relative to reference samples from the Sava and Tisa Rivers. The results indicate that geological origin has a strong influence on the content of heavy metals in river sediments, primarily regarding concentrations of Ni and Co. Furthermore, Tamiš, Tisa, Sava, and Danube sediments are under strong anthropogenic influence.

Mineralogical and chemical composition of Arctic gastropods shells

Assessment of environmental controls and natural variability of shell chemistry is inevitable to understand the future of marine calcifiers functioning under the climate change and acidification scenarios. Here we document mineralogical and chemical composition (Al/Ca, Ba/Ca, Fe/Ca, Mg/Ca, Mn/Ca, Na/Ca, P/Ca, S/Ca, Sr/Ca and Zn/Ca ratios) of shells of 27 gastropod species collected in four Arctic and sub-Arctic coastal localities. Most examined gastropods had purely aragonitic shells, although three species were characterized by bimineralic mineralogy, with calcite forming the external shell layer. Positive relationship between shell size and proportion of calcite in bimineralic gastropods indicated that older specimens could possess a thicker outer shell layer of calcite than did younger individuals. Statistically significant differences in shell chemical composition were found among species irrespective of the sampling location, suggesting that organisms exerted a biological control on elements uptake and retention. Extrinsic factors (mostly seawater temperature, seawater and sediment metals concentrations) contributed to elements uptake to a lesser degree. Thus, the observed differences in shell elements’ concentrations among gastropod species can be driven by both factors: species-specific selective incorporation of elements into shells and bioavailability of those elements in the ambient environment.

Fatty-acid based assessment of benthic food-web responses to multiple stressors in a large river system

Rivers are often exposed to multiple stressors, such as nutrients and contaminants, whose impacts on the river food webs may not be distinguished by sole assessment of biological community structures. We examined the benthic algal assemblages and the fatty acids (FA) of benthic macroinvertebrates in the lower Athabasca River in Canada, aiming to assess the changes in algal support and nutritional quality of the benthic food web in response to cumulative exposure to natural bitumen, municipal sewage discharge (hereafter, “sewage”), and oil sands mining (“mining”). Data show that the decline in water quality (increases in nutrient concentrations and total suspended solids) was associated with decreases in benthic diatom abundance, and was driven mainly by sewage-induced nutrient enrichment. Responses in nutritional quality of benthic macroinvertebrates, indicated by their polyunsaturated FA (PUFA) concentrations, were taxon- and stressor-specific. Nutritional quality of the larval dragonfly predator, Ophiogomphus, decreased nonlinearly with decreasing benthic diatom abundance and was lowest at the sewage-affected sites, although exposure to natural bitumen also resulted in reduced Ophiogomphus PUFA concentrations. In contrast, the PUFA concentrations of mayfly grazers/collector-gatherers were not affected by natural bitumen exposure, and were higher at the sewage and sewage+mining sites. The PUFA concentrations of the shredder Pteronarcys larvae did not change with cumulative exposure to the stressors. Sediment metal and polycyclic aromatic compound concentrations were not associated with the macroinvertebrate FA changes. Overall, we provide evidence that sewage induced reduction in trophic support by PUFA-rich diatoms, and was the predominant driver of the observed changes in FA composition and nutritional quality of the benthic macroinvertebrates. Fatty-acid metrics are useful to untangle effects of concurrent stressors, but the assessment outcomes depend on the functional feeding guilds used. A food-web perspective using multiple trophic levels and feeding guilds supports a more holistic assessment of the stressor impacts.

Risk Assessment of Heavy Metals in Sediment Samples from the Mae Chaem River, Chiang Mai, Thailand.

Heavy metals are significant environmental pollutants that are recognized as posing a potential health hazard to human beings. We investigated the concentrations of the heavy metals As, Cd, Cr, Cu, Ni, Pb, and Zn in surface sediments collected from the Mae Chaem River in Chiang Mai, Thailand, during the dry season in 2021. The mean concentrations of heavy metals in sediments were, in decreasing order, Zn > Cr > As > Pb > Ni > Cu > Cd. The mean values of As, Cd, Cr, and Cu were determined to be 32.5 ± 18.3, 0.33 ± 0.07, 45.8 ± 11.9, and 21.9 ± 7.42 mg Kg-1, respectively. These levels are higher than their standard levels in Thailand, namely 10.0, 0.16, 45.5, and 21.5 mg Kg-1, respectively. Principal component analysis (PCA) revealed that the primary origins of heavy metal contamination are predominantly attributed to residential settlements and agricultural areas. The hazard quotient (HQ) was used to estimate the non-carcinogenic risk of exposure to heavy-metal-bound surface sediments for both children and adults. The results showed that the HQ values for both groups were less than 1.0 (HQ < 1.0), indicating no risk. Moreover, assessment of the long-term risk for ingestion of toxic metals indicated no risk (<10-6) based on the lifetime cancer risk (LCR). However, the LCR values of As and Cr were 5.3 × 10-6 and 2.5 × 10-6, respectively, demonstrating the most elevated LCR among the hazardous metals in terms of children's exposure. Therefore, it is possible that children living in agricultural areas and participating in activities around the study area may be exposed to elevated concentrations of As and Cr.