Surface Water Sediment Research Articles

Heavy metal contamination assessment and source attribution in the Vicinity of an iron slag pile in Hechi, China: Integrating multi-medium analysis

Heavy metals, such as mercury, cadmium, and nickel, may contaminate human inhabited environments, with critical consequences for human health. This study examines the health impacts of heavy metal pollution from an iron slag pile in Hechi, China, by analyzing heavy metal contamination in water, sediment, soil, and crops. Here, the Nemerow pollution index (NI) indicated severe pollution at most sampling sites, the mean NI of groundwater, and surface water had reached 594.13 and 26.79, respectively. Bioaccumulation of mercury (Hg), cadmium (Cd), and nickel (Ni) was noted in crops, cucumbers showed comparatively lower risk levels. Logarithmic surface water-sediment partition coefficient calculations indicated that heavy metals such as chromium (Cr), ferrum (Fe), zinc (Zn), copper (Cu), Ni, arsenic (As), and lead (Pb) tend to accumulate in sediments. There was a high risk in groundwater (67.48–6590.54) and surface water (13.73–2500.85). Variably influenced by rainfall, these metals can be diluted and mobilized from surface water and sediments, thereby changing the contamination levels and ecological risks. Probabilistic health risk assessments indicated that health risks were higher in children than in adults, the mean total carcinogenic risk values of soil, groundwater, and surface water, were 6.79E-04, 4.20E-06, and 1.15E-6 for children, respectively. Moderate soil pollution is the main health hazard. A Positive Matrix Factorization model attributed over 60% of the pollution to slag stacking. Biotechnologies, solidification/stabilization techniques, field management, and institutional controls, driven by principles of green, low-carbon, and economic efficiency may mitigate. These findings contribute to the management of heavy metal pollution in iron slag pile areas.

Ecological and health risk assessments of heavy metals in surface water sediments from Ifite Ogwari community in Southeastern Nigeria

The hydrosphere becomes contaminated secondarily by accumulated heavy metals in sediments which may be released into the aquatic environment, thereby increasing the risks to human health. To evaluate the pollution characteristics of heavy metals in surface water sediments of Ifite Ogwari, nine sediment samples were collected from surface water sources used by the residents for drinking and other household activities. The concentrations of eight heavy metals: cadmium (Cd), chromium (Cr), copper (Cu), Iron (Fe), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) were analyzed using Atomic Absorption Spectroscopy (AAS). Enrichment Factor (EF), Contamination Factor (CF), Geoaccumulation index (Igeo), Potential Ecological Risk Index (PERI) and Risk Assessment Code (RAC) were conducted. Results of heavy metal concentration indicated that Cu < Cr < Ni < Pb < Cd < Zn < Mn < Fe based on the average metal concentration. Human health assessment showed high cancer risk for children and adults in a ratio of 1 in 10000 population. PERI indicated that sediment samples from Iyiutu and Ahala streams have low potential ecological risk while samples from Ube, Tabasi and Ogbu showed moderate ecological risk whereas samples from Isiachala, Nabaloku and Atammele streams as well as Omambala river sediments were high. RAC shows no ecological risk by Zn, Pb, Ni, Cu and Mn but in Omambala river, Cr and Cd contributed to ecological risk while Fe contributed to ecological risk in all the samples. Consequently, there is need for proper monitoring from health base evaluation and conscious effort to live in a clean environment devoid of any kind of exposure.

Investigating biotic and abiotic degradation of emerging contaminants in surface water-sediment batch systems

Four emerging compounds including estrone, progesterone, sulfamethoxazole and trimethoprim were investigated for their degradation in water/sediment systems exposed to a variety of biotic and abiotic conditions. Both the water and sediment were sampled from River Yamuna. The experiments were conducted in batch mode for 40 days. The degradation kinetics were described using a pseudo first-order reaction model. Among the four exposure conditions, bio-photodegradation led to higher removal of emerging contaminants. Comparing photodegradation in sterile surface water and distilled water showed the impact of interfering ions on the photochemical reactions thereby slowing the reaction. All the four target compounds underwent rapid degradation in batch 4, consisting of distilled water exposed to sunlight. The identification of transformation products suggested degradation pathways except for estrone, for which only one transformation product was identified. The study also detected the transformation products in Yamuna surface water samples confirming the presence of the proposed degradation pathways in the environment.

Teasing out the Effects of Natural Stressors at Chemically Contaminated Sites.

Aquatic ecosystems are often impacted by a multitude of stressors, many of which are introduced by a combination of anthropogenic activities such as agricultural development, urbanization, damming, and industrial discharge. Determining the primary stressors responsible for ecological impairments at a site can be complex and challenging; however, it is crucial for making informed management decisions. Improper diagnosis of an impaired system can lead to misguided attempts at remediation, which can be both time consuming and costly. We focused on the development, implementation, and evaluation of methodologies that, in combination, allowed us to identify the primary stressors. These included a four-phase, weight-of-evidence (WOE) assessment including in situ Toxicity Identification and Evaluation (iTIE) testing, physicochemical and macrobenthos characterization, reciprocal sediment transplants, and laboratory and in situ toxicity testing. The contaminants of concern (COCs) at the site were elevated levels of ammonia, chloride, pH, and total dissolved solids in groundwater upwellings into a high-quality waterway. Reciprocal transplants of site sediments and nearby reference sediments and traditional benthic sampling showed impaired benthic indices and multiple stations around a contaminated industrial settling basin. Impaired stations had elevated COCs in groundwaters but exhibited a steep vertical concentration gradient, with concentrations decreasing near the sediment-surface water interface. We describe Phase 4 of the study, which focused on teasing out the role of dissolved oxygen sags in benthic macroinvertebrate responses. Extensive submerged and emergent macrophytes, algae, and cyanobacteria co-occurred at the impaired sites and increased throughout the summer. Laboratory testing suggested that ammonia and pH were possibly toxic at the sites, based on groundwater concentrations. The in situ toxicity testing, however, showed toxicity occurring even at stations with low levels of COCs concurrently with large diurnal fluxes in dissolved oxygen (DO). A final phase using a type of iTIE approach utilized limnocorrals with and without aeration and with in situ toxicity measures using Hyalella azteca. The Phase 4 assessment revealed that low DO levels were primarily responsible for impaired benthic communities, and COC upwellings were diluted at the sediment-water interface to nontoxic levels. These findings will allow for improved management decisions for more efficient and effective restoration activities. Environ Toxicol Chem 2024;43:1524-1536. © 2024 SETAC.

Risk Assessments of Polycyclic Aromatic Hydrocarbons in the Surface Sediments of Drinking Water Sources in Ifite Ogwari, South-East Nigeria

ABSTRACT Surface water is the main source of drinking water in Ifite Ogwari, Anambra State, South-East Nigeria. In aquatic environments, sediment functions as both a source and a sink of polycyclic aromatic hydrocarbons (PAHs). To determine the level of pollution, health concerns to people and the environment, and potential sources of PAHs in the surface water sediments in Ifite Ogwari, sediment samples were collected from 9 surface water sources used for drinking by Ifite Ogwari people and were analyzed using a Gas Chromatography/Flame Ionization Detector (GC-FID). In all sediment samples, only 11 PAHs out of 16 United States Environmental Protection Agency (USEPA) priority PAHs were detected while 5 were below detectable limits. The concentration of benzo[a]anthracene was high but detected in only 2 sediment samples while fluoranthene has a relatively close concentration across all samples. Benzo[k]fluoranthene has the highest concentration compared to other PAHs in the samples while benzo[a]pyrene has the lowest concentration across all samples. Atammele sediment was analyzed as the most carcinogenic followed by Isiachala with concentrations of 84.23 ng/µL and 51.92 ng/µL respectively. Ube stream sediment has the lowest concentration of PAHs (11.74 ng/µL). Ecological risk of the PAHs revealed a sediment-to-sediment variation in the risk profile. Human health risk assessment depicts that hazard index and total cancer risk for adults and children ranged from 2.3E-07 - 2.57E-05 and 4.85E-07 - 5.43E-05 respectively. Pyrogenic activities are the main source of PAHs in the sediments. The results provide a guide for monitoring PAHs pollution and protecting drinking water sources.

Concentration levels, spatial variations and exchanges of polychlorinated biphenyls (PCBs) in ambient air, surface water and sediment in Bursa, Türkiye

In this study, ambient air, surface water and sediment samples were simultaneously collected and analyzed for PCBs to investigate their levels, spatial variations and exchanges between these three compartments at different sampling sites for 12 months in Bursa, Türkiye. During the sampling period, a total of 41 PCB concentrations were determined in the ambient air, surface water (dissolved and particle phase) and sediment. Thus, 945.9 ± 491.6 pg/m3 (average ± STD), 53.8 ± 54.7 ng/L, 92.8 ± 59.3 ng/L and 71.4 ± 38.7 ng/g, respectively. The highest concentrations of PCBs in the ambient air and in water particulate phase were measured at the industrial/agricultural sampling site (1308.6 ± 252.1 pg/m3 and 168.7 ± 21.2 ng/L, respectively), ∼ 4–10 times higher than background sites; while the highest concentrations in the sediment and dissolved phase were measured at the urban/agricultural sampling sites (163.8 ± 27.0 ng/L and 145.7 ± 15.3 ng/g, respectively), ∼ 5–20 times higher than background sites. PCB transitions between ambient air-surface water (fA/fW) and surface water-sediment (fW/fS) were investigated by fugacity ratio calculations. According to the fugacity ratios obtained, volatilization from the surface water to the ambient air was observed at all sampling sites (98.7 % of fA/fW ratios are <1.0). Additionally, it has been determined that there is a transport from the surface water to the sediment (100.0 % of fW/fS ratios are higher than 1.0). The flux values in ambient air-surface water and surface water-sediment environments ranged from −1.2 to 1770.6 pg/m2-day and from −225.9 to 0.001 pg/m2-day, respectively. The highest flux values were measured for PCBs with low chlorine content (Mono-, Di-Cl PCBs), while the lowest flux values were measured for the high chlorine content PCBs (Octa-, Nona- and Deca-Cl PCBs). As it was determined in this study that surface waters contaminated by PCBs have the potential to pollute both air and sediments, it will be important to take measures to protect surface waters.

Biomonitoring by using Rapid-Read Pathogenic Bacteria Indicator in Sediments and Bivalve Mollusks: Southern Gulf of Thailand, a Mangrove Area Case Study

Pathogenic bacteria groups can be applied to be rapid bioindicator for environmental assessment. The objective of study was to monitor 5 groups of indicator and pathogenic bacteria (Escherichia coli/ total coliform, Salmonella spp., Vibrio spp., Bacillus spp. and Clostridium spp.) in surface water sediments collected before monsoon and after monsoon season from 6 areas located in a Thepha District, Songkhla province mangrove closed to Southern gulf of Thailand. Each collected area were selected in criteria of totally different in environment parameter and tide. The relative levels of total coliforms, and E. coli, were typically increased in rainy season (July) compared with winter and summer at most sites. In parallel, the highest number of Vibrio spp. was found in summer (April). The highest number of E. coli and Coliform were detected during rainy season at the estuary area with low oxygen dissolved, the average numbers were 6.6×103 and 3.8×105 CFU/g, respectively. Coliform number shows negative correlate with dissolved oxygen (r2 = 0.756, p &lt; 0.05). In addition, total coliform, Bacillus spp. and Clostridium spp. were found in bivalve mollusks during rainy season but the total was not over standard. A very strong positive correlation was found between the temperature and the number of Vibrio spp. and Bacillus spp. The number presence of Vibrio spp. has a strong positive correlation with pH, the number of Bacillus spp. and number of Clostridium spp. In contrast, Vibrio spp. number was strongly negative correlated with water salinity (r2 = 0.632, p &lt; 0.05). Salmonella species were detected only 2 area around shrimp farm in between December of a year-round. In this study area, there are no evidence that the number of Salmonella and Clostridium species founded related to changing of season. This is the first baseline data as an alternative guide concept for the determination of bacterial indicators. Pathogenic bacteria number can be applied to be a key factors for a rapid health assessment for villager around study area that related to EIA in the near future. HIGHLIGHTS The common problem in biomonitoring process in environment are limit of biological indicator and less data collected to establish relative between bioindicator and environmental parameters Key pathogenic bacteria groups were selected and analyzed conducted in order to find the rapid-read method for biomonitoring and assessment This is the first baseline data as an alternative guide concept for the determination of bacterial indicators. Pathogenic bacteria number can be applied to be a key factors for a rapid health assessment for villager around study area that related to EIA in the near future GRAPHICAL ABSTRACT

Effect of repeated sorption–desorption on irreversible and reversible absorption of hydrophobic perfluoroalkyl acids to freshwater sediment

Understanding the factors governing irreversible and reversible sorption is essential to predict the influence of sediment on contaminant fate and transport in surface waters. This study used sediment of an urban water body to demonstrate irreversible accumulation and reversible absorption of perfluoroalkyl acids (perfluorooctane sulfonate (PFOS), perfluorononanoic (PFNA) and perfluorodecanoic acid (PFDA)) during two sorption–desorption (S–D) cycles. Absorption and desorption isotherms were consistent with sorption to irreversibly absorbing glassy sediment organic carbon (SOC) and liquid–liquid like partitioning to rubbery SOC. The observed absorption isotherms and the desorption isotherms were adequately fitted linear models. Irreversible absorption showed signs of saturation and the reversible partitioning diminished during the 2nd S–D cycle causing the composite sorption capacity to decrease. Results suggest that under the conditions tested, surface water sediment can act as sink for the studied PFAAs. Rubbery SOC can potentially release or absorb contaminants, thus acting as a concentration buffer. S–D cycling can cause irreversible absorption concentration to increase even when exposure occurs at lower concentrations (i.e. 5 μ g / L ). log K O C values of sediment that underwent S–D cycling overlaps with the range of field date, suggesting that the sediment of surface water may have experienced some degree of S–D cycling. • History of absorption–desorption affect the fate of PFAAs in aquatic environment. • Sorption of PFAAs is consistent with two-domain absorption assumption. • Surface water sediment can act as sink for PFAAs. • Rubbery sediment organic carbon can act as a concentration buffer.

ASSESSMENT OF RIVER SEDIMENT QUALITY ACCORDING TO THE EU WATER FRAMEWORK DIRECTIVE IN LOWLAND FLUVIAL CONDITIONS. A CASE STUDY IN THE DRAVA RIVER AREA, DANUBE RIVER BASIN

The EU Water Framework Directive requires the monitoring and evaluation of surface water sediment quality based on the assessment of risk posed by contamination on the biotic receptors. Fluvial sediments are important receptors of hazardous substances (HSs) pollution from the upstream catchment areas in the Danube River Basin (DRB). For the development of systematic sediment quality monitoring and evaluation, the Drava River region on the border of Hungary and Croatia was selected as a test area representative of lowland hydromorphological conditions. Overbank (floodplain) sediments and river bottom sediments (stream sediments) were sampled at two depths at 9 locations in the test area. Eight heavy metal(oid)s were analyzed As, Cd, Cr, Cu, Hg, Ni, and Zn as hazardous substances. The sediment quality assessment was carried out according to the 2013/39/EU Directive and EU Water Framework Directive standards. Most of the analysed HS concentrations in river bottom sediment and overbank (floodplain) sediments fall within the limits of environmental quality standards (EQS). Results show that there is no significant differences in metal(oid) HS concentrations among the various sediment types and between shallow (0-5cm) and deeper (stream sediment: 5-10cm; floodplain sediment: 40-50cm) sediment which suggests that the large lowland Drava River fluvial system is an extensive single fluvial system with homogeneous distribution of sediments and the associated contaminants. Specifically, the studied sediments in the tributaries of the Drava River do not seem to be contaminated with metal(oid) hazardous substances but at certain sites concentrations are elevated above the environmental limit values, especially for As and Zn, and to lesser extent for Cr. The data analysis techniques used enabled the identification of sites with anthropogenic pollution and the recognition of regional pattern in HSs distribution.

ASSESSMENT OF RIVER SEDIMENT QUALITY ACCORDING TO THE EU WATER FRAMEWORK DIRECTIVE IN MOUNTAINOUS FLUVIAL CONDITIONS. A CASE STUDY IN THE UPPER TISA AREA, DANUBE RIVER BASIN

Discharge of hazardous substances (HSs) in hydrographic basins represent a danger to aquatic biological activity and water supplies and can severely pollute surface water sediments. The increase of pollution in the Danube Basin requires the implementation of systematic monitoring and evaluation of the sediments quality as dictated by the EU Water Framework Directive. For this system development, applicable in mountainous conditions, the Upper Tisa region in the northwest part of Romania on the border with Ukraine, Hungary and Slovakia was selected as a test area. Sampling of overbank (floodplain) sediment, river bottom sediment and suspended sediment was carried out at 10 locations in the test area in order to analyze the concentration and distribution of eight metal(oid)s (Cu, Pb, Zn, Cd, Hg, Ni, Cr and As), in addition to 3 organic components (anthracene, fluoranthene, benzo(e)pyrene) as hazardous substances (HSs). The sediment quality assessment was carried out according to the 2013/39/EU Directive and EU Water Framework Directive standards. Most of the analyzed HS concentrations in river bottom sediment and overbank (floodplain) sediments fall within the limits of environmental quality standards (EQS). As, Cu, Pb, and Zn tend to exceed the EQS at some locations. The highest exceedances were recorded for Pb, for which contents of up to 987 mg/kg were detected. The highest contents were found in the overbank sediments sampled, and the lowest in river bottom sediments, which may indicate historical pollution. Mercury contents in overbank sediment samples exceed all standards, while cadmium content is below the international standards. Anthracene, fluoranthene and benzo(e)pyrene concentrations in overbank and bottom sediments comply with international standards. A few samples in suspended sediments slightly exceed the lowest environmental standard value (i.e., Romanian normal value). HS concentrations remain low in the suspended sediments showing that it is not the main transport route for pollution in this area. HS contents decrease gradually from upstream to downstream due to dilution along the river course. In the last testing point at Someș Aciua, the concentration of metal(oid)s measured in the sediments remain below the EQS limit values, thus there is no risk of transboundary pollution. The main source of metal(oid) contamination is historic base-metal ore mining and the associated mine waste sites in the Baia Mare and other mining areas scattered around the whole region. The main source of the studied organic compounds is the incomplete or low-temperature coal combustion processes that occur in households in rural areas

Biomonitoring and assessment of toxic element contamination in floodplain sediments and soils using fluorescein diacetate (FDA) enzymatic activity measurements: evaluation of possibilities and limitations through the case study of the Drava River floodplain

The EU Water Framework Directive requires the monitoring and evaluation of surface water sediment quality based on the assessment of risk posed by contamination on the biotic receptors. Floodplain sediments are important receptors of potentially toxic element (PTE) contamination from the upstream catchment areas, and floodplains host climate-sensitive riverine ecosystems and fertile agricultural areas at the same time. This study investigates the effect of PTE contamination on microbial communities in floodplain sediments and soils using the fast, inexpensive and reliable fluorescein diacetate (FDA) method in order to estimate its applicability for sediment quality monitoring and preliminary toxicity-based risk assessment. Sediment and soil samples were collected from the actively flooded alluvial plain and the river terrace areas along a 130-km stretch of the large Drava River floodplain known to be widely contaminated by historical mining, smelting and the associated industry in the upstream Alpine region. Results of detailed data analysis show that the total microbial activity represented by the measured FDA values is related to PTE (As, Cu, Zn, Cd, Pb) concentrations, but this relationship shows significant heterogeneity and depends on the spatial location and on the soil properties such as organic matter content, dissolved salt and nutrient content, and it is specific to the toxic elements. Results show that some microbe species appear to be able to adapt to the elevated PTE concentrations in toxic soil micro-environments, over time. Despite the observed heterogeneity of microbial activity, the results revealed a breakpoint in the FDA dataset around the FDA = 3 FC (fluorescein concentration) value suggesting that microbial activity is controlled by thresholds.

Occurrence, partitioning, and bioaccumulation of an emerging class of PBT substances (polychlorinated diphenyl sulfides) in Chaohu Lake, Southeast China

Polychlorinated diphenyl sulfides (PCDPSs) represent an emerging group of constituents that are persistent, bioaccumulative and toxic (PBT) substances of great concern in terms of human health and ecological integrity. However, little is known about the occurrence, environmental behaviour and ecological risks of PCDPSs in lake environments. In this study, the concentrations of 21 PCDPSs were determined in surface water, suspended particulate matter (SPM), sediments, and 8 fish species from Chaohu Lake, China. Eighteen PCDPS congeners were prevalently detected in the samples, with concentrations ranging from 0.272−1.69 ng/L (water), 0.477−2.03 ng/g d.w. (SPM), 0.719−4.07 ng/g d.w. (sediment) and 0−0.131 ng/g w.w. (fish), respectively. Medium- and high-chlorinated PCDPSs in SPM and sediment were significantly higher than those in water samples. Increased PCDPS concentrations were found in higher trophic level fishes and those with a demersal habitat preference, indicating their bioaccumulation and biomagnification potential. The logBCFs, BSSAFs, and BSAFs of PCDPS congeners in fishes were determined to be 3.91−5.18, 0.0500−2.33, and 0.0360−4.94 L/kg, respectively. The organic carbon normalized partition coefficients (logKoc) of PCDPSs in surface water-SPM (4.61−5.54 L/g) and surface water-sediment (4.38−5.69 L/g) systems were determined, and it was found that highly chlorinated PCDPSs were more prone to migrate from water to sediment and SPM. The toxic equivalent (TEQ) values of PCDPSs in the samples (lower than 10−1 pg/g or pg/L) and daily intake via fish consumption (0.180−0.340 μg/kg/day) were estimated for humans, and cumulative risk quotients (RQs) after correction at ten sampling sites (0.065−0.66) were calculated for green algae. The findings elucidated the environmental behaviour of PCDPSs in Chaohu Lake.

Tracing long-distance electron transfer and cable bacteria in freshwater sediments by agar pillar gradient columns.

Cable bacteria (CB) perform electrogenic sulfur oxidation (e-SOx) by spatially separating redox half reactions over centimetre distances. For freshwater systems, the ecology of CB is not yet well understood, partly because they proved difficult to cultivate. This study introduces a new 'agar pillar' approach to selectively enrich and investigate CB populations. Within sediment columns, a central agar pillar is embedded, providing a sediment-free gradient system in equilibrium with the surrounding sediment. We incubated freshwater sediments from a streambed, a sulfidic lake and a hydrocarbon-polluted aquifer in such agar pillar columns. Microprofiling revealed typical patterns of e-SOx, such as the development of a suboxic zone and the establishment of electric potentials. The bacterial communities in the sediments and agar pillars were analysed over depth by PacBio near-full-length 16S rRNA gene amplicon sequencing, allowing for a precise phylogenetic placement of taxa detected. The selective niche of the agar pillar was preferentially colonized by CB related to Candidatus Electronema for surface water sediments, including several potentially novel species, but not for putative groundwater CB affiliated with Desulfurivibrio spp. The presence of CB was seemingly linked to co-enriched fermenters, hinting at a possible role of e-SOx populations as an electron sink for heterotrophic microbes. These findings add to our current understanding of the diversity and ecology of CB in freshwater systems, and to a discrimination of CB from surface and groundwater sediments. The agar pillar approach provides a new strategy that may facilitate the cultivation of redox gradient-dependent microorganisms, including previously unrecognized CB populations.

Enhanced self-powered system with graphene oxide modified electrode for simultaneous remediation of nitrate-contaminated groundwater and river sediment

Simultaneous in situ remediation of malodorous organic sediment and nitrate-contaminated groundwater was achieved with a novel, enhanced, self-driven three-chamber bio-electrochemical system with Graphene Oxide (GO) modified electrodes. It has been successfully improving the electron transfer efficiency and self-purification ability by the special configuration combining surface water, sediment with underground water. The upper part can be regarded as a Sediment Microbial Fuel Cell (SMFC). The organic sediment serves as available carbon source to provide electrons for the microbes coated on the anode instead of potential pollutants. The lower part is the Biofilm Electrode Reactor (BER). Electrons were synchronously obtained from the loaded biofilm to reduce nitrate. The electricity generated from the upper part was applied directly to the lower part as electrical stimulation to enhance bacterial denitrification of the system. The electron conduction efficiency was further improved by graphene oxide modifying. With a maximum power density of 14.21 W/m2, as well as the voltage outputs ranging from 700 mV to 900 mV, nitrate removal was accelerated with less accumulation of intermediates compared with the controls without graphene oxide. The maximum output power was increased by 1.5 times and the nitrate removal efficiency (in 10 h) was increased from 89.13 ± 1.4% to 99.9 ± 0.1% after the modification. The organic matter in the sediment decreased by 78% after 270 days simultaneously. Sequencing of the microbial community showed that Geobacter and Anaerolinina were enriched in the anode. And theα-proteobacteria were enriched in the four experimental groups and had a good effect on nitrate removal especially in the C-GO-SSG system (Carbon felt anode-Graphene Oxide Modified cathode equipped Surface-water Sediment and Groundwater System) after 270 days operation. These results demonstrate that the C-GO-SSG system can be further used to remediation of sediment and groundwater with improved efficiency.

Heavy metals in soil, water sediment, and ambient PM2.5 across the Yangtze River economic belt: integrated environment risk identification and countermeasures

Abstract To explore the integrated pollution features of heavy metals in environmental multi-media throughout the Yangtze River Economic Belt (YREB) is of significance for national/local decision-makers to establish a sustainable development strategy. Distributions, enrichments, and induced environmental risks of typical toxic metals in soil, water surface sediment, and PM2.5 from the 11 provinces/municipalities of the YREB were studied based on bibliometric analysis. Compared with the background values, Cu, Zn, Cd, Pb, Hg, and Ni were enriched in both soil and surface sediments to a certain extent. Also, the provincial contents of As and Cr were higher than the standard limit of PM2.5. Spatially, the heavy metal pollution in environmental multi-media was distributed primarily in the central and southern parts of the YREB, specifically in the Hunan, Guizhou, Hubei, and Jiangxi provinces. The noncarcinogenic risks of As in soil and PM2.5 were the main contributor to the total risk. In the surface sediment, the average potential ecological risk for Cd and Hg reached Level V (very high ecological risk) and Level IV (high ecological risk), respectively, which is much higher than that for the other metals (Level I, low potential ecological risk). Consequently, Cd, Hg, and As were considered as priority control metals, and targeted risk management policies were recommended.

Effects of Plow-Tillage on Preventing and Controlling the Black Water Events in Shallow Lakes

The high organic loading sediment in the areas of algal accumulation are the primary cause of frequent occurrence of black water in the western Chao Lake. Through an algal accumulation experiment, plow-tillage based on resuspension characteristics and its effect on lake sediment was assessed using a large device capable of simulating lake-winds and sediment resuspension. The dynamics of overlying water coloration, ρ(Fe²⁺), ρ(S2-) in the process of black water induction, the key physicochemical characteristics of newly formed water–sediment interface, and iron and sulfur variations in interstitial-water and their response to plow-tillage were examined. The results showed that plow-tillage depth significantly influenced black-water formation; a 15 cm plow-tillage depth helped in controlling black-water. When black water occurred in other plow-tillage controls, i.e., (2, 5, and 10 cm), along with blank-treatments during day 8 to 14, typical overlying water characteristics [ρ(Fe²⁺) and ρ(S2-)] of the plow-tillage 15 cm treatments were 68.6%, 79.5%, 48.1%, 46.7%, and 51.3%; and 75.2%, 65.7%, 57.1%, 74.5%, and 75.0%, respectively, in comparison to that of the other plow-tillage controls and blank-treatments. Further analysis of the bottom-water and bottom-sediments revealed that the 15 cm plow-tillage depth treatment significantly enhanced the tolerance of the fresh water–sediment interface to algal accumulation and anoxic environments. Through the black water induction simulation, the dissolved oxygen concentration, redox potential, and pH of the bottom-water and at the interface were observably much higher than those in the black-water groups. However, ρ(ΣH₂S) was significantly lower than that of other treatments. The ρ(Fe²⁺) in the surface-sediment water was 0.54 mg/L, which corresponds only 25.3–33.7% that of the black-water groups. Fe²⁺ accounted for 25.2% of the total iron, being considerably lower than ~40.0% of the black-water groups. The concentration of acid-volatile sulfides was 0.51 µg/g, which corresponds only 14.6–17.2% that of the black-water groups. Overall, plow-tillage helped to physically improve sediment in areas of algal accumulation. Plow-tillage could help turn surface-sediment overloaded with organic pollutants to the lower-layer, blocking material migration and supply of contaminated surface-sediment, and controlling anaerobic microbial activity. It could prevent the formation of black water-generating substances in the water column where algae accumulate and die, effectively preventing the occurrence of black water.

Quantification, distribution, and effects of di (2-ethylhexyl) phthalate contamination: Risk analysis and mitigation strategies in urban environment.

Phthalate acid ester, di (2-ethylhexyl) phthalate (DEHP) is ubiquitously detected contaminant of emerging concerns (CECs) in all the environmental samples. The present study attempted to understand the fate and transport of DEHP in urban areas by evaluating the quantities, distribution, risk, and effects in the Mysuru city, India. The study is anticipated to serve as a vital document for local and national regulators to frame a robust DEHP management plan and mitigate the risks associated. Liquid-liquid microextraction followed by gas chromatographic analysis was adopted to determine the concentrations of DEHP. The risk quotient method was adopted to assess potential risk, and a conceptual planning model framework was designed to mitigate the DEHP contamination. The municipal wastewater contained 115±9.2μg/L, whereas treated municipal wastewater showed 95±7.6μg/L DEHP that was attributed to the inefficiency of the treatment plant. Further, sediments in surface water, as well as groundwater samples of the study area, showed 8±0.64 to 12±0.96μg/L and 32±2.56 to 40±3.2μg/kg of DEHP, respectively. The risk quotient of 19.17 for samples in around treatment indicated highest risk, whereas groundwater samples had a risk quotient of 1-2 indicating relative risk to aquatic organisms. In addition, the study highlighted the source, possible entry pathways, and management strategies including treatment aspects to draw an understanding of the distribution and potential ecological imbalances with contamination of DEHP in the urban sector. PRACTITIONER POINTS: Understand the fate and transportation of DEHP in urban wastewater. Primary investigation and assessment to possible health and environmental risks of DEHP contamination in urban wastewater. Revealed the associated health risks and proposed possible management strategies.

Arsenic sequestration in pyrite and greigite in the buried peat of As-contaminated aquifers

Detrital peat (organic carbon-enriched deposit) with high arsenic (As) content is widely distributed in sediments where groundwater As contamination exists. Iron sulfides often persist in these sediments under anoxic conditions. However, the mechanisms and pathways of formation of iron sulfides and its potential contribution in controlling As mobility are still poorly understood. In this study, we examined three As-contaminated peat sediments from the Hetao Basin in China to gain better understanding of the complex interplay between iron sulfides formation and As mobility. We employed high-resolution spectroscopic techniques, including X-ray absorption spectroscopy and 57Fe Mössbauer spectroscopy, coupled with electron microscopy to determine the speciation of iron sulfides and the associated As in the peat sediments.Pyrite (FeS2) and metastable greigite (Fe3S4) persisted in peat as end-members of S and Fe diagenetic pathways. The Fe-rich phyllosilicates and decaying plant tissues provided the ideal micro-environments for pyrite and greigite nucleation. Pyrite formation most likely occurred via the polysulfides pathway in the surface water-sediments interface during early diagenetic process, while the relative enrichment of reactive Fe compared to sulfide possibly inhibited the transformation of greigite to pyrite in such Fe-rich sediments.Our results revealed that the peat sediments could act as a stable sink for As immobilization under steady groundwater anoxic conditions, with As content up to 250 mg/kg and large proportions (40 to 60 wt.% As) sequestered in pyrite and greigite. Pyrite crystallites had up to 1 wt.% As content through the replacement of the S-I sites. Greigite crystallites had a relatively constant As content ranging from ∼500 to ∼1400 mg/kg. Instead of being adsorbed or structurally incorporated, arsenic formed distinct arsenic sulfide phase in the greigite-enriched sediments, which was analogous to realgar. The transfer of As from iron sulfides to ferrihydrite temporarily retarded As release into groundwater under slightly oxic groundwater conditions. However, the reductive dissolution of ferrihydrite and potential subsequent As re-release could be a source of As in groundwater under disturbed redox conditions.

Streambank Legacy Sediments in Surface Waters: Phosphorus Sources or Sinks?

Streambank legacy sediments can contribute substantial amounts of sediments to Mid-Atlantic waterways. However, there is uncertainty about the sediment-bound P inputs and the fate of legacy sediment P in surface waters. We compared legacy sediment P concentrations against other streambank sediments and upland soils and evaluated a variety of P indices to determine if legacy sediments are a source or sink of P to surface waters. Legacy sediments were collected from 15 streambanks in the mid-Atlantic USA. Total P and M3P concentrations and % degree of phosphorus saturation (DPS) values for legacy sediments were lower than those for upland soils. % DPS values for legacy sediments were below the water quality threshold for P leaching. Phosphorus sorption index (PSI) values for legacy sediments indicated a large capacity for P sorption. On the other hand, equilibrium phosphorus concentration (EPC0) for legacy sediments suggested that they could be a source or a sink depending on stream water P concentrations. Anoxic conditions resulted in a greater release of P from legacy sediments compared to oxic conditions. These results suggest that legacy sediment P behavior could be highly variable and watershed models will need to account for this variability to reliably quantify the source-sink behavior of legacy sediments in surface waters.

SewerSedFoam: A Model for Free Surface Flow, Sediment Transport, and Deposited Bed Morphology in Sewers

This paper aims to bridge the gap in the detailed modelling of flow and sediment process interactions in sewers through the development of a computational fluid dynamics (CFD) model. It draws on previous models developed for surface water sediment transport in the OpenFOAM CFD framework and builds on them to improve their suitability for sewer sediment processes. Three distinct sediment processes, suspended sediment transport, bedload transport, and deposited bed morphology, are incorporated into a free surface flow solver, interFoam. This sewer sediment model, called SewerSedFoam, models the impacts of sediment deposition and erosion on flow velocity by using dynamic mesh deformation to capture the movement of the deposited bed and its morphology. Further, three sediment classes, two suspended and one bedload sediment, can be modelled along with some bed stabilization and consolidation effects during deposition and erosion, respectively. The functionality of the overall model in modelling sewer sediment deposition and erosion is promising, although the validation of a large magnitude sediment erosion event has been limited by the availability of granular data in existing case studies.