Fe In Sediments Research Articles

Study on the Quality of Mako-mako River Water as Clean and Raw Water Source in Yembekiri Village

This study aims to determine the water quality of the Mako-mako river based on physical, chemical and microorganism parameters as well as the effect of metal and microorganism levels on the color of the water and sediment of the Mako-mako river. The method of sampling water, sediment and plankton by purposive sampling at three locations, namely the upstream, middle and downstream of the river. The concentrations of Fe and Mn in water and sediment were analyzed using AAS, while the identification of plankton using a binocular microscope. The results of the analysis of the water quality of the Mako-mako river show that the parameters of temperature, TDS, TSS and Mn are still below the water quality standard for class 1, except for the Fe and total coliform parameters whose concentrations have exceeded the water quality standard. The metal content of Fe in sediment is high and affects the color of the Mako-mako river sediment which is reddish brown to dark brown (deep). The presence of plankton with a low level of abundance and diversity index did not affect the color of the river water or the sediment of the Mako-mako riverSo that to use the Mako-mako river water as a source of raw water, clean water needs to go through a processing process.

Mobility and bioavailability of mercury in sediments of the southern Baltic sea in relation to the chemical fractions of iron: Spatial and temporal patterns

Marine sediments play a significant role as reservoirs for mercury (Hg), a bioaccumulative toxic pollutant that poses risks to human and ecosystem health. Iron (Fe) has been recognized as an influential factor in the complexation and bioavailability of Hg in sediments. However, limited studies have investigated the interactions between the chemical fractions of these elements in natural settings. This study aims to examine the fractions of Hg and Fe in sediments of the Baltic Sea, a region historically impacted by Hg pollution. The Hg fractions were determined using the thermodesorption technique, while sequential extraction was employed to identify the Fe fractions. The findings confirm the crucial role of Fe in the formation, as well as the horizontal and vertical distribution of labile and stable Hg in marine sediments. Factors such as the contribution of organic matter, the presence of reactive Fe, and Fe associated with sheet silicates emerged as significant drivers that positively influenced the content of the most labile Hg fractions, potentially affecting the mobility and bioavailability of Hg in the marine environment.

Low content of highly reactive iron in sediments from Prydz Bay and the adjacent Southern Ocean: Controlling factors and implications for sedimentary organic carbon preservation

Examining iron (Fe) speciation in marine sediments is critical to understand Fe and carbon biogeochemical cycling in polar regions. In this study, we investigated the speciation of Fe in sediments from Prydz Bay and the adjacent Southern Ocean, and examined the factors controlling Fe speciation and its relationship with total organic carbon (TOC). Our results reveal that unreactive silicate Fe (FeU) is the dominant pool of total Fe (FeT), followed by poorly reactive sheet silicate Fe (FePRS), reducible crystalline Fe oxides (Feox2), easily reducible amorphous/poorly crystalline Fe oxides (Feox1), and magnetite (Femag), with carbonate-associated ferrous Fe (Fecarb) being the smallest pool. The highly reactive Fe (FeHR)/FeT ratios (0.13 ± 0.06) in our study area are among the lowest end-member globally, primarily due to weak bedrock weathering and slow glacier melting. The Feox1/FeT ratios are similar to those in continental shelf and marginal seas containing highly weathered materials, while the Feox2/FeT ratios are significantly lower. This result implicates that low temperature inhibits the aging of iceberg melting-sourced Feox1 potentially, and accordingly the regulation of weathering on the FeHR/FeT ratio is mainly reflected in Feox2/FeT ratio. There are no significant correlations between TOC and FeHR, Fecarb, Feox1 or Feox2 in the research region. Four distinct patterns of TOC/FeHR ratio can be discerned by summarizing the global data set: (a) high TOC/FeHR ratios (> 2.5) are likely the result of high marine primary productivity and low chemically weathered source materials; (b) low TOC/FeHR ratios (< 0.6) are caused by high rates of FeHR inputs and OC remineralization; (c) mid-range TOC/FeHR ratios (0.6 – 2.5) typical of most river particulates and marginal sea sediments indicate the same FeHR and OC sources and/or interactions between each other; (d) both low TOC and FeHR content is the result of low marine primary productivity and weak chemical weathering. Our findings provide new insights into the relationship between FeHR and TOC in polar sediments.

Construction of the comprehensive evaluation system of waterbody pollution degree and the response of sedimentary microbial community

This study proposed and established a comprehensive evaluation system for the pollution degree of the waterbody by taking overlying water and sediment as a whole. By dividing different sampling points into three gradients according to the pollution degree, the changes in sedimentary microbes under various pollution gradients were compared. The results showed that microbial diversity, abundance and specific OTUs decreased significantly with the increase in pollution degree. Meanwhile, Firmicutes, Bacteroidota and Caldiseriota increased in the severely polluted group, while Chloroflexi and Acidobacteriota decreased. Spearman correlation analysis and co-occurrence network revealed that COD, pH in overlying water, and Mn, Fe in sediments were the most significant pollution degree evaluation indicators affecting sedimentary microorganisms, which drove the sedimentary microbial communities dominated by Proteobacteria and Firmicutes. FAPROTAX functional prediction indicated that increased pollution levels led to the weakening of functional genes related to nitrogen metabolism and sulfur metabolism and the increase of functional genes related to carbon metabolism in sediment microorganisms. This study not only provided new insights into waterbody pollution evaluation but also verified the feasibility of this evaluation method by the response of sedimentary microbial communities to different pollution degrees.

Distance impacts toxic metals pollution in mining affected river sediments

The study of metals mobility derived from mining activities in an ultramafic lithology is limited. This study investigates the effects of distance on potentially toxic metals such as Co, Cu, Fe, Mn, Ni, Pb, and Zn pollution, and the geochemical processes of fluvial system downstream of an ex-copper mine (Mamut River). The toxicity level of the river was evaluated using various sediment quality guidelines, ecotoxicological risks (ecological risk and risk index) and pollution indices. The geochemical behavior and stability of these toxic metals in the solid-phase samples were also examined. The results show that elevated concentrations of Ni, Cu, and Fe in the sediments can be linked to the adsorption and precipitation of metals from the aqueous-phase samples. We found that the metal scavenging rate as a function of distance is more evident in tropical environments than it was previously thought (10 km downstream). Such an inference could be explained by the greater amount of rainfall (pH 5.5–6.5) received in the tropics and higher weathering products that could react and form stable complexes. Geochemical analysis of the river sediment indicates that Ni, Cu, and Fe in the river sediment have increased 44-, 81-, and 90-fold compared to the background values, respectively. A significant decrease in the concentration of the potentially toxic metals was found at 5.5 km downstream. The scavenging rate of Fe is the highest (1485.82 μg g−1 km−1) followed by Cu (141.48 μg g−1 km−1), Ni (10.23 μg g−1 km−1), Pb (8.12 μg g−1 km−1) and Zn (5.01 μg g−1 km−1) in the tropical river system. In contrast, the concentration of Co and Mn in the river sediments doubled as the river flows approximately 5 km downstream due to the higher mineral solubility and weaker metal partition coefficient. This study also discusses the possibility of asbestos (mainly as chrysotile in the X-ray diffraction) as a potential hidden risk present within the ultramafic setting. This case study can be extrapolated to explain the dispersion of inorganic pollutants in an ultramafic environment in a global context.

Physicochemical properties, total hydrocarbon content, and trace metals of water and sediments from major River Estuaries within the Niger Delta Region of Nigeria

Water and sediment samples from Cross River, Imo River, and Qua Iboe River Estuaries were collected and treated using standard analytical procedures. The samples were analyzed for their physicochemical properties, total hydrocarbon content (THC), and trace metals. Results obtained revealed that, the mean levels of total suspended solids (TSS), total dissolved solids (TDS), turbidity, colour, biochemical oxygen demand (BOD), THC, cadmium (Cd), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn) in water were higher than their acceptable limits in Nigeria. Whereas, the mean levels water pH, electrical conductivity (EC), dissolved oxygen (DO), nitrate, sulphate, phosphate, and copper (Cu) were within their acceptable limits. The results obtained also revealed that, the mean levels of nitrate, THC, and Fe in sediments were higher than their recommended limits. While the levels of pH, EC, sulphate, phosphate, Cd, Cu, Ni, Pb, and Zn in sediments were within their recommended limits. This study indicated that the anthropogenic activities by oil and oil-related companies within the Niger Delta Region of Nigeria may have contributed significantly to the high level of toxic substances in the water channels within the zone. The results obtained revealed that, the direct or indirect exposure to untreated water from the studied water channels may result in serious health challenges. Hence, the environment should be closely monitored to forestall a devastating situation in the region.

Mapping heavy metals contamination and eco-risk along Mediterranean Sea coast, Egypt

The study was selected according to its variability in resources and its important location parallel to an important protectorate. This coastal zone is characterized by different land use/cover activities (water, industrial site, agricultural areas, bare land, vegetative areas, fish farms, and sabkha). Twelve sites were selected along this part of the Mediterranean deltaic coast, each distance between every site is nearly 5 km. water and sediment samples were collected for the determination of these metal ions (Fe, Mn, Zn, Cu, Ni, Pb, Cd, and Co). The average concentrations of heavy metals are 56.50, 2.53, 24.77, 4.28, 0.88, 18.37, 0.97 and 0.06 µg/l in water and 7284.58, 132.60, 13.52, 2.99, 8.36, 4.84, 0.36 and 4.32 µg/g in sediments for Fe, Mn, Zn, Cu, Ni, Pb, Cd, and Co, respectively. The concentrations of these metals (Zn, Cu, Ni, Pb, and Cd) are within the Australian guideline of marine sediments, but Zn, Cu, and Cd in water exceed these limits. Cadmium was the most abundant element in the coastal marine sediments. The heavy metal pollution index for marine water of the study area is within the normal limits except for site 12. The risk index of metals gives a low-risk category. The principal component analysis indicated that site 11 was related by dissolved Pb in seawater and Fe in sediments, this is maybe interpreted by the nature of sediment texture and different shipping activities. Mapping the spatial distribution of metals and their risk categories is an aid in monitoring environmental problems and quantifying their magnitudes.

Heavy Metals Accumulation in Dragonflies (Odonata) and Their Habitats in District Swabi, Khyber Pakhtunkhwa, Pakistan: Assessing Dragonfly Bionomics in the Region.

The current study aimed to examine the bionomics of dragonflies and heavy metal accumulation in their bodies and environment (sediments and water) from district Swabi, Khyber Pakhtunkhwa, Pakistan. A total of 1683 dragonflies were collected from May to September, 2018 in 4 tehsils (administrative subdivisions) of district. Orthetrum pruinosum neglectum was the most abundant species followed by O. anceps and O. chrysostigma luzonicum. Highest abundance was observed in July and August corresponding to maximum temperature and rainfall. Dragonflies displayed preferable abundance within agricultural lands and on elevation ranging from 206 to 506 m. Heavy metal analysis of sediments and water samples from 4 tehsils showed significant differences in mean concentrations of Pb, Zn, Cu, and Fe. Abundance among districts was negatively associated with Fe levels in water while the species diversity had a significant positive relationship with Fe in sediments. Accumulation of metals in each body part significantly varied among species. N. tullia tullia and O. anceps specifically demonstrated their tolerance to high concentrations of heavy metals.

Benthic iron flux influenced by climate‐sensitive interplay between organic carbon availability and sedimentation rate in Arctic fjords

AbstractBenthic iron (Fe) fluxes from continental shelf sediments are an important source of Fe to the global ocean, yet the magnitude of these fluxes is not well constrained. Processing of Fe in sediments is of particular importance in the Arctic Ocean, which has a large shelf area and Fe limitation of primary productivity. In the Arctic fjords of Svalbard, glacial weathering delivers high volumes of Fe‐rich sediment to the fjord benthos. Benthic redox cycling of Fe proceeds through multiple pathways of reduction (i.e., dissimilatory iron reduction and reduction by hydrogen sulfide) and re‐oxidation. There are few estimates of the magnitude and controlling factors of the benthic Fe flux in Arctic fjords. We collected cores from two Svalbard fjords (Kongsfjorden and Lilliehöökfjorden), measured dissolved Fe2+ concentrations using a two‐dimensional sensor, and analyzed iron, manganese, carbon, and sulfur species to study benthic Fe fluxes. Benthic fluxes of Fe2+ vary throughout the fjords, with a “sweet spot” mid‐fjord controlled by the availability of organic carbon linked to sedimentation rates. The flux is also impacted by fjord circulation and sea ice cover, which influence overall mineralization rates in the sediment. Due to ongoing Arctic warming, we predict an increase in the benthic Fe2+ flux with reduced sea ice cover in some fjords and a decrease in the Fe2+ flux with the retreat of tidewater glaciers in other regions. Decreasing benthic Fe2+ fluxes in fjords may exacerbate Fe limitation of primary productivity in the Arctic Ocean.

Effects of the disappearance of seasonal thermal stratification on the mobilization of iron and phosphorus in reservoirs, southern China—A case of Tianbao Reservoir, Nanning City

为了探究我国南方地区水库季节性热分层消亡前后沉积物铁和磷的迁移规律，于2019年11月-2020年1月对天雹水库多点位（浅水区和深水区）水体理化指标进行原位监测，并利用薄膜扩散梯度技术（DGT）高分辨率获取沉积物有效态铁和磷的浓度分布.结果表明：（1）天雹水库沉积物有效态Fe和P浓度分别为4.67~18.72和0.003~0.073 mg/L，其中有效态Fe浓度较太湖、鄱阳湖和洞庭湖高出一个数量级，且浅水区沉积物中有效态Fe浓度较深水区高；（2）热分层消亡过程，沉积物有效态Fe和P浓度的时空差异大，浅水区有效态Fe浓度表现为Day14>Day1>Day32>Day54，有效态P浓度表现为Day1>Day14>Day32>Day54，而深水区有效态Fe和P浓度变幅较小甚至呈增长趋势，归因于浅水区热分层结构对气象因子扰动的响应速率快，水体垂向混合加剧了沉积物中Fe和P的释放；（3）沉积物-水界面处有效态Fe和P的交换通量分别为6.58~31.59和0.008~0.086 mg/（m²·d），均自沉积物向上覆水中不断迁移，由于浅水区的热分层消亡时间早于深水区，浅水区内源Fe²⁺和PO₄^3-的释放对冬季水质恶化的贡献较大，应密切关注水库浅水区沉积物内源释放对整个库区水质的影响.;To investigate the mobilization of iron and phosphorus in the sediments of reservoirs in southern China during the disappearance of seasonal thermal stratification, physicochemical indexes were in-situ monitored from November 2019 to January 2020 in shallow and deep area of Tianbao Reservoir. Simultaneously, diffusive gradients in thin films (DGT) technique were used to acquire the concentration distributions of labile Fe and P in the sediments. The results show: (1) The concentrations of labile Fe ranged from 4.67 to 18.72 mg/L, which far exceeded that of Lake Taihu, Lake Poyang and Lake Dongting, while the concentrations of labile P ranged from 0.003 to 0.073 mg/L. The concentrations of labile Fe in sediments of the shallow area were higher than those of the deep area. (2) The space-time differences between labile Fe and P in the sediments were obvious during the disappearance of thermal stratification. In the shallow area, the concentrations of labile Fe presented decline order: Day14>Day1>Day32>Day54, and labile P was Day1>Day14>Day32>Day54, while the concentrations of labile Fe and P increased in the sediments of the deep area. It was attributed to the quick response of thermal stratification in shallow area to the sudden drop in temperature, consequently increasing the release of Fe and P at the sediment-water interface. (3) The diffusion flux of labile Fe at the sediment-water interface ranged from 6.58 to 31.59 mg/(m²·d), and that of labile P ranged from 0.008 to 0.086 mg/(m²·d), which meant Fe and P diffused from the sediments to the overlying water. The mixing time in the shallow area was earlier than the deep area, resulting in the significant contribution of internal Fe and P release to deterioration of water quality in winter. Therefore, the internal release of sediments in the shallow area should be paid more attention in reservoirs of southern China.

Characterizing geochemistry of organic carbon, sulfur, and iron in sediments of the middle Okinawa Trough since the last glacial maximum

The diagenetic interplays of organic carbon (OC), sulfur (S), and iron (Fe) in marine sediments and their responses to changes in depositional and climatic conditions are poorly characterized. In this study, chemical speciation and isotopes were combined to characterize diagenesis of OC, S and Fe in sediments of the middle Okinawa Trough (OT), a back-arc deep basin along the edge of the East China Sea outer shelf, since the Last Glacial Maximum (LGM). Two key geochemical proxies, i.e., OC/pyrite-S ratios and the degrees of pyritization, indicate anoxic bottom-water conditions during the last Glacial/Deglacial, which promoted burial of OC and pyrite. However, a shift to oxic conditions during the Deglacial-Holocene transition facilitated aerobic respiration, resulting in lower burial of OC and pyrite. In contrast to previous studies, the environmental changes induced by large sea-level rises since the LGM have not triggered significant variations in pyrite-S isotopic compositions, probably due to persistently low sedimentation rates. Variable extents of Fe enrichment are identified in the sediments since the LGM, with lower enrichment during the Holocene probably due to increased distance of Fe shuttling and concomitant Fe ageing. Anoxic bottom water during the Glacial/Deglacial did not induce an expected intensification of OC sulfurization, probably because sedimentary Fe enrichment favored pyrite formation but competitively dampened OC sulfurization. Lines of geochemical evidence hint at a discontinuous deposition at ~200 cm depth probably caused by mass wasting.

Organic matter stabilized Fe in drinking water treatment residue with implications for environmental remediation

Fe-based materials used to adsorb P are commonly considered to be limited by the increased Fe lability, while Fe in drinking water treatment residue (DWTR) shows stable P adsorption abilities. Accordingly, this study aimed to gain insight into Fe lability in DWTR as compared to FeCl3 and Fe2(SO4)3 using Fe fractionation, EXAFS, and high-throughput sequencing technologies. The results showed that compared to Fe2(SO4)3 and FeCl3, Fe was relatively stable in the DWTR under the effects of organic matter, sulfides, and anaerobic conditions. Typically, the addition of FeCl3 and Fe2(SO4)3 enhanced Fe mobility in sediment and overlying water, promoting the formation of Fe-humin acid and ferrous sulfides (FeS and FeS2). However, the addition of DWTR, even at relatively high doses of Fe, has limited impact on Fe mobility. The addition remarkably increased oxidizable Fe in sediment (by approximately 63%), causing Fe to be dominated by oxidizable and residual fractions (like those in raw DWTR); EXAFS analysis also suggested that Fe-humin acid increased substantially with the addition of DWTR, becoming the main Fe species in sediment (with a relative abundance of 50.1%). Importantly, the Fe distributions were stable in sediment with DWTR added, which demonstrated that organic matter stabilized the Fe in the DWTR. Further analysis indicated that all materials promoted the enrichment of bacterial genera potentially related to Fe metabolism (e.g., Bacteroides, Dok59, and Methanosarcina). Fe2O3 in the FeCl3 and Fe2(SO4)3 groups and Fe-HA in the DWTR group were the key species affecting the microbial communities. Overall, the stabilizing effect of organic matter on Fe in DWTR could be used to develop Fe-based materials to enhance Fe stability for environmental remediation.

Geochemical Explorations of Leached Fe in Tiga Warna Beach, Indonesia

To explore Fe minerals in Tiga Warna Beach, we investigated to assess the geochemical fraction of Fe in sediment. The samples were leached of Fe using the optimized BCR microwave method. The optimized of BCR microwave method revealed the high accuracy and precision before Fe assessment. The leached of Fe in each of fraction in sediment were measured by AAS. The same patterns of explored Fe in the geochemical fractions from the sediment fraction 1 (mobile fraction) to fraction 3 (oxidizable fraction) as stated nonresistant sediment fractions showed a lower portion of Fe compared with the Fe levels in sediment fraction 4 (residual fraction) or resistant sediment fraction. The Pollution Load Index (PLI) value and the geoaccumulation Index (I-geo) value of sediment samples in blue, green, and red waters indicating that the sediments of Tiga Warna Beach are still natural and has not been categorized as polluted.

Diffusion kinetic process of heavy metals in lacustrine sediment assessed under different redox conditions by DGT and DIFS model

Different fractions and variations of Mn, Co, Ni, Cu, Cd, Pb, Zn, and Fe in sediment via oxic and anaerobic treatments were investigated using BCR sequential extraction methods, DGT technique, and DIFS model. The results indicated that reducible fraction was the considerable pool apart from residual fraction, suggesting the high desorption potential of heavy metals. The high-resolution DGT measurement indicated that CDGT significantly rose after anaerobic condition and characterized by the relative high R value. Significantly increasing positive fluxes varying from 0.64 to 339.4 μg cm−2 s−1 except Ni suggested that apparent diffusion upward occurred over time from the sediment to the overlying water on anaerobic episode. High proportion of reducible Fe fraction and concurrent reduction of Fe(III) to Fe(II) during anaerobic condition were responsible for the increase of labile metals. The diffusion kinetic parameters including the equilibrium distribution coefficient (Kd), response time (Tc), and rate constant (k1 and k−1) were obtained using DIFS model. These parameters confirmed the partially sustained resupply capacity of heavy metals from solid sediment particle to pore water because of the considerable reducible fractions. Additionally, planar optode (PO) imaging approach demonstrated that low pH accompanied with decreasing dissolved oxygen (DO) concentration on anaerobic condition enhanced the release of labile metal fraction. Generally, anoxia facilitated the reduction of reducible fraction of heavy metals and further strengthened the desorption, resupply and diffusion in the aquatic ecosystems.

Interplay between iron species transformation and hydroxyl radicals production in soils and sediments during anoxic-oxic cycles

Iron (Fe) redox transformation in soils and sediments plays an essential role in the biogeochemical cycling of associated nutrients and elements. It is documented recently that hydroxyl radicals (OH) can be produced upon oxygenation of Fe(II)-bearing minerals in soils and sediments. As OH induces serious oxidative stress to microbes, it is likely that OH produced upon Fe(II) oxygenation inactivates the coexisting dissimilatory iron-reducing bacteria and subsequently impacts Fe redox transformation. This hidden interplay between Fe species transformation and OH production in soils and sediments during anoxic-oxic cycles remains unexplored. In this study, a field sediment was incubated with 1 × 109 CFU/mL Shewanella oneidensis strain MR-1 and treated for six anoxic-oxic cycles (117-h anoxic and 6-h oxic periods). Fe species transformation, OH production and MR-1 activity variation were measured throughout the six cycles. Fe in the sediments prior to anoxic-oxic cycles mainly existed in Fe-bearing silicates (60–70%) and Fe (hydr)oxides (30–40%). For the anoxic periods, a portion of Fe(III) in sediments was either reduced to structural Fe(II) in (hydr)oxides and silicates or reductively dissolved to aqueous Fe2+. Total Fe(II) produced from Fe(III) bio-reduction increased from 2.46 to 8.24 mM in the first two anoxic periods, but decreased to 0.10 mM in the following four anoxic periods. For the oxic periods, Fe(II) was oxidized along with a production of OH, and the cumulative OH concentrations were around 31 µM in the first three periods but decreased to 6.3 µM in the subsequent three periods. MR-1 was inactivated by about 0.6 order of magnitude in the first two oxic periods, and the inactivation became insignificant for the later oxic periods. The six cycles of anoxic-oxic treatments promoted the transformation of Fe(III) (hydr)oxides into more amorphous phase. A strong interplay between Fe species transformation and OH production occurred in anoxic-oxic cycles. Fe(III) bio-reduction by MR-1 in anoxic periods determined the content and speciation of Fe(II), which governed OH production in the subsequent oxic periods. The generated OH affected MR-1 activity in oxic periods, which further controlled Fe(III) bio-reduction in anoxic periods. The hidden interplay identified herein improves our understanding of the cycling of Fe and associated elements under redox fluctuating environments.

Heavy metals in water, sediment, fish and associated risks from an endorheic lake located in Southern Africa

The study assessed heavy metals (Cd, Cu, Fe, Mn, Pb and Zn) and physico-chemical parameters in water, sediments and fish from an endorheic lake (Lake Chilwa) in Malawi. It was observed that pH (max. 9.7), EC (max. 2936 μS/cm), TDS (max. 2119 mg/L), NO3− (max. 6.6 mg/L) and PO43− (max. 1.3 mg/L) were higher in the dry season than in the rainy season. Pb was not detected in all samples. However, the rest of heavy metals were detected with significant values of Mn and Cu in fish (Mn: 0.015–1.18 mg/kg dry weight, dw; Cu: 0.41–0.92 mg/kg dw) and sediment (Mn: 2.25–10.66 mg/kg dw; Cu: n.d–1.63 mg/kg dw). The concentrations of heavy metals in fish samples were below the maximum limits for edible fish recommended by Food and Agriculture Organization/World Health Organization: Cd (0.1 mg/kg), Cu (3 mg/kg), Fe (43 mg/kg), Pb (0.2 mg/kg), Mn (2–9 mg/kg) and Zn (60 mg/kg). The calculated target hazard quotients (ranged from 0.001 to 1.07) indicated no human risks from fish consumption. Furthermore, dry season values for Mn, Cu and Zn in sediments were significantly higher (p < 0.05) than those of the rainy season. Conversely, Fe in sediments was significantly higher (p < 0.05) in the rainy season than in the dry season. The use of fertilizer and indiscriminate disposal of metal products contributes to the observed levels. This calls for reinforcement of suitable agricultural and waste management practices in the study area.

Cumulative Sulfate Loads Shift Porewater to Sulfidic Conditions in Freshwater Wetland Sediment.

It is well established that sulfide can be toxic to rooted aquatic plants. However, a detailed description of the effects of cumulative sulfate loads on sulfide and iron (Fe) porewater geochemistry, plant exposure, and ecological response is lacking. Over 4 yr, we experimentally manipulated sulfate loads to self‐perpetuating wild rice (Zizania palustris) populations and monitored increases in the ratio of sulfur (S) to Fe in sediment across a range of sulfide loading rates driven by overlying water sulfate. Because natural settings are complicated by ongoing Fe and S loads from surface and groundwater, this experimental setting provides a tractable system to describe the impacts of increased S loading on Fe–S porewater geochemistry. In the experimental mesocosms, the rate of sulfide accumulation in bulk sediment increased linearly with overlying water sulfate concentration up to 300 µg‐SO4 cm–3. Seedling survival at the beginning of the annual life cycle and seed mass and maturation at the end of the annual life cycle all decreased at porewater sulfide concentrations between 0.4 and 0.7 µg cm–3. Changes to porewater sulfide, plant emergence, and plant nutrient uptake during seed production were closely related to the ratio of S to Fe in sediment. A mass balance analysis showed that porewater sulfide remained a small and relatively transient phase compared to sulfate in the overlying water and Fe in the sediment solid phase. The results illuminate the evolution of the geochemical setting and timescales over which 4 yr of cumulative sulfate loading resulted in a wholesale shift from Fe‐dominated to sulfide‐dominated porewater chemistry. This shift was accompanied by detrimental effects to, and eventual extirpation of, self‐perpetuating wild rice populations. Environ Toxicol Chem 2019;38:1231–1244. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Analysis of Fe in Sediment Material using a Modified Tessier Technique for Detection of Fe-Anthropogenic and Fe-Naturals

Monitoring of environmental pollution can be carried out in the leaching process to determine the quality of sediment. This study modified the Tessier method leaching process using an optimized microwave. This study reported the effect of radiation contact time and microwave power in the microwave Tessier method based on their level of accuracy and precision to the analysis of Fe in sediment. After optimizing the microwave Tessier method, we continued using this optimization to determine pollution status using the Contamination Factor (CF) values. The results showed the time of contact of the radiation and microwave power gave an influence in the optimized Tessier analysis of Fe in sediment. The optimized conditions were in the fraction 1 (power radiation: 10%; time: 2 minutes), fraction 2 (power radiation: 30%; time: 3 minutes), fraction 3 (power radiation: 50%; time: 2 minutes), fraction 4 (power radiation: 50%; time: 3 minutes). The microwave Tessier method produced the recovery percentage of 94.11%. Fe concentration in sediments showed in the non-resistant fraction had a range between 537.6 mg/kg - 575.9 mg/kg, whereas Fe concentrations in the resistant fraction ranged from 3161.6 mg/kg - 10067.2 mg/kg. The results of CF values were obtained at 1.933-1.961, indicating the moderate contamination status in the Gulf of Prigi.

Environmental Health Status of Some Aquatic Ecosystems in Badagry Division, Lagos, Nigeria

The status of Agboju, Ajegunle, Topo and Gbaji water bodies in Badagry Division of Lagos State, Nigeria was evaluated between April and November 2018 in order to determine the suitability of the ecosystem to biota and safety of the aquatic resources for human consumption. Some environmental variables such as alkalinity, temperature, biochemical oxygen demand (BOD), conductivity, total dissolved solid (TDS), carbon (iv) oxide (CO₂), total hardness, chemical oxygen demand (COD), turbidity, phosphate, dissolved oxygen (DO), pH, salinity, sulphate and nitrate, and some heavy metals (Fe, Cu, Zn, Pb, Cd and Cr) in water, sediment, aquatic plant (<i>Eichhornia crassipes</i>) and fish (<i>Ethmalosa fimbriata</i>) were measured using standard procedures. The results showed that BOD, COD, total hardness and turbidity values were above the standard permissible limits. Cd in water column of Agboju and Ajegunle, and Pb recorded from Agboju, Ajegunle and Topo, exceeded standard permissible limit. Cu (0.56±0.54), Zn (5.45±0.89), Pb (0.54±0.47) and Cr (0.455±0.375) contents in <i>E. fimbriata</i> (from Ajegunle) was slightly above permissible limits while Cd and Fe contents in the fish across the four stations were above permissible limits. Contamination factor, Index of geochemical accumulation and enrichment factor showed moderate degree of contamination of cadmium and Fe in the sediment. This preliminary study could be concluded that the biota can still survive in the ecosystems despite high contamination of the water bodies with metals. However, human consumption of several of <i>E. fimbriata</i> and water could cause health hazard. Therefore, urgent effort should be made by all users of the ecosystem to decline in discharging untreated waste into these water bodies.

The Possibility of Using the Fresh Water Bivalve, Spathopsis Rubens, in The Nile River, El Mahmoudia Water Stream as Bioindicator For Pollution

Bivalves are used as bioindicators of heavy metals pollution because they are known to concentrate these elements, providing a time integrated indication of environmental contamination. Trace metals can reach high concentrations in sediments and also in aquatic organisms by bioaccumulation through the food chain. Six heavy metals (Hg, Zn, Pb, Fe, Mg and Cu) were collected and investigated from Abu Hummus, El Behara. The concentration of Hg was high in winter as 2.3µg/g in sediment. The Zn concentration was high in summer in sediment as 8.1µg/g. The Pb concentration was high in winter in water as 3.3µg/l. The concentration of Fe in sediment was high in summer as 492 µg/g. The concentration of Mg was high in sediment as 408µg/g. The concentration of Cu was high in summer in sediment as 301µg/g. The mean concentrations of Fe in the present study are within the permissible limits of law 48/1982 (&lt;1 mg/l) and the guideline of (WHO, 1993) which is &lt;1 mg/l. The mean concentration level of copper is within the permissible limits of law 48/1982 (&lt;1.0 mg/l). The mean levels of the heavy metals (Hg, Zn, Pb, Fe, Mg and Cu) detected in the present study in the water stream are less than the permissible limits recommended by (USEPA, 2005). In the present study there is a significance between all seasons in the protein content in the soft tissue of Spathopsisrubensas the mean concentration level in Spring was reported as 102.83mg/g which is higher then that of autumn 100.5mg/g, summer 93.33 mg/g and winter 80.50 mg/g. In the present study the mean activity level of GPx in spring was higher than the other seasons such as spring 31.33u/g ˃ summer 28.33 u/g ˃Autumn 26.67 u/g ˃ winter 20.50u/g. The mean activity level of SOD in summer was higher than the other seasons such as summer 38.83 u/g ˃ spring 33.33 U /g ˃Autumn 28.83U/g ˃ winter 22.83U/g. The mean activity level of CAT in spring was higher than the other seasons such as spring 25.67u/g ˃ summer and autumn19.83u/g ˃ winter 15.17u/g. The mean activity level of MDA in winter was 30.50 U/g ˃ summer 22.50U/g ˃ autumn 18.0 U/g ˃ spring 16.83U/g. In the present study it was found that the mean activity level of MDA increased in winter at the same time the mean activity level of CAT, SOD and GPx were decreased in winter. Negative correlation was reported between CAT and Hg in winter as r=-0.88*. A positive correlation coefficient in winter was found between SOD activity level and CAT activity level as r=0.838*.