Sediment Extracts Research Articles

Deep-Water Circulation over the Last Two Glacial Cycles Reconstructed from Authigenic Neodymium Isotopes in the Equatorial Indian Ocean (Core HI1808-GPC04)

We reconstructed the past deep-water character of the equatorial Indian Ocean using the isotope ratio of neodymium (εNd) in the Fe–Mn coating of mixed-species foraminifera. When compared with previous εNd records at the same site (ODP 758) and at another site to the west (SK 129), the three datasets were consistent and showed glacial-interglacial variations, even though the other two records were extracted from different media (cleaned foraminifera and bulk sediment leach). This confirms that while the foraminiferal coating is the preferred medium for reconstructing past bottom water εNd records, for carbonate-dominated lithologies, weak acid extraction of bulk sediment is also a viable option offering high-resolution capabilities. When the lithology includes volcanic particles or high organics, the extraction protocol may need to be adjusted to guard against detrital contamination or a slight correction may need to be applied. During glacials, the deep waters bathing the equatorial Indian Ocean had a larger AABW component and during interglacials a larger NADW component. Our HI1808-GPC04 record supplements the ODP 758 record in the interval with prominent AABW signal (MIS 6/5 transition and MIS 7) and reveals regional effects in some non-radiogenic intervals. The smaller differences between the HI1808-GPC04/ODP 758 and SK 129 records seem to reflect regional Nd input from river systems and non-radiogenic Nd from the boundaries.

Using Caenorhabditis elegans to assess the ecological health risks of heavy metals in soil and sediments around Dabaoshan Mine, China.

Heavy metal pollution is a global environmental problem, and the potential risks associated with heavy metals are increasing. The acid mine drainage (AMD) which is generated by mining activities at Dabaoshan Mine, the largest polymetallic mine in southern China, is harmful to local residents. A detailed regional survey of the ecological and human health risks of this polluted area is urgently needed. In this study, eight sediments and farmland samples were collected along the flow direction of tailing wastewater and Fandong Reservoir; the content of multiple heavy metals in these samples was determined by inductively coupled plasma mass spectrometry. The biological toxicity of water-soluble extracts from the samples was further assessed by referring to different endpoints of Caenorhabditis elegans (C. elegans). The relationship between specific heavy metals and biological toxicity was estimated by partial least squares regression. The results indicated that the risk of heavy metals in Dabaoshan mining area was very high (potential ecological risk index = 721.53) and was related to geographical location. In these samples, the carcinogenic risk (the probability that people are induced carcinogenic diseases or injuries when exposed to carcinogenic pollutants) of arsenic (As) for adults exceeded the standard value 1 × 10-4 and indicated that As presented a high carcinogenic risk to adults, while the high risk of non-carcinogenic effects (the hazard degree of human exposure to non-carcinogenic pollutants) in children was related to lead exposure (hazard index = 1.24). In addition, the heavy metals at high concentration in the water-soluble fraction of sediment and farmland soil extracts, which might easily distribute within the water cycle, inhibited the survival rate and growth of C. elegans. Gene expression and enzymatic activity related to oxidative stress were increased and genes related to apoptosis and metallothionein were also affected. In conclusion, the results of chemical analysis and biological assays provided evidence on the toxicity of soil and sediment extracts in the Dabaoshan mining area and advocated the control and remediation of heavy metal pollution around Dabaoshan Mine.

Sand mining far outpaces natural supply in a large alluvial river

Abstract. The world's large rivers are facing reduced sediment loads due to anthropogenic activities such as hydropower development and sediment extraction. Globally, estimates of sand extraction from large river systems are lacking, in part due to the pervasive and distributed nature of extraction processes. For the Mekong River, the widely assumed estimate of basin-wide sand extraction is 50 Mt per year. This figure is based on 2013 estimates and is likely to be outdated. Here, we demonstrate the ability of high-resolution satellite imagery to map, monitor, and estimate volumes of sand extraction on the Lower Mekong River in Cambodia. We use monthly composite images from PlanetScope imagery (5 m resolution) to estimate sand extraction volumes over the period 2016–2020 through tracking sand barges. We show that rates of extraction have increased on a yearly basis from 24 Mt (17 to 32 Mt) in 2016 to 59 Mt (41 to 75 Mt) in 2020 at a rate of ∼8 Mt yr−1 (6 to 10 Mt yr−1), where values in parentheses relate to lower and upper error bounds, respectively. Our revised estimates for 2020 (59 Mt) are nearly 2 times greater than previous best estimates for sand extraction for Cambodia (32 Mt) and greater than current best estimates for the entire Mekong Basin (50 Mt). We show that over the 5-year period, only 2 months have seen positive (supply exceeds extraction) sand budgets under mean scenarios (5 months under the scenarios with the greatest natural sand supply). We demonstrate that this net negative sand budget is driving major reach-wide bed incision with a median rate of −0.26 m a−1 over the period 2013 to 2019. The use of satellite imagery to monitor sand mining activities provides a low-cost means to generate up-to-date, robust estimates of sand extraction in the world's large rivers that are needed to underpin sustainable management plans of the global sand commons.

An Extract and Fractions from Coffea arabica Sediment on Antioxidant and Anti-Tyrosinase Activities, and on the Quality of Whiteleg Shrimp (Litopenaus vannamei) during Refrigerated Storage.

Coffea arabica sediment, a popular agro-by-product from the coffee juice processing industry, contains many phytochemicals, and it is often discarded as waste. The antioxidant and anti-tyrosinase activities of an ethanol extract and its active fractions obtained from Coffea arabica sediment was studied. Additionally, whiteleg shrimp (Litopenaeus vannamei) was treated with the extract and fractions, and the quality during refrigerated storage was evaluated. The most active fraction (P<0.05) fraction III from the Coffea arabica sediment extract showed a total phenolic content of 116.5 mg gallic acid equivalent/g, an inhibitory concentration of 50% value of 27.3 μg/mL in the 2,2-diphenyl-1-picryl hydrazyl test, an absorbance of 3.7 (at 1.0 μg/mL) in the reducing power assay, and 79.5% inhibition for the tyrosinase inhibition test (at 100 μg/mL). Whiteleg shrimp treated with PD-3 and crude extract (CE) retarded the growth of bacteria and spoilage microor-ganisms in comparison to the control (P<0.05). Lower values in pH, thiobarbituric acid reactive substances, and total volatile base content were enumerated in samples treated with PD-3 and CE (P<0.05) compared to controls. Loss in freshness, protein content, and melanosis formation declined with CE and PD-3 treatments. Our findings showed that Coffea arabica sediment has antioxidant and antimicrobial properties. Also, it could be a promising treatment in melanosis prevention, and a natural additive for extending the shelf life of whiteleg shrimp during refrigerated storage; thus an alternative to traditional sulfites.

Lead, zinc and arsenic contamination of pit lake waters in the Zeida abandoned mine (High Moulouya, Morocco)

In the Zeida abandoned mine, pit lake waters exhibit alkaline pH and high conductivity. The concentrations of the total dissolved lead and zinc are very low due to their adsorption on clay minerals and iron oxyhydroxides. Conversely, arsenic concentrations in two lakes (ZL1 and ZA) exceed WHO water quality guidelines. The As content is relatively high in ZL1 and exists mainly as As(V). In ZA, As(III) occurs in low concentration compared to the total dissolved arsenic, while dimethylarsenic acid (H 2 AsO 2 (CH 3 ) 2 , DMA) prevails. This means that arsenic was methylated by organic matter produced by micro-organisms such as chlorella. The sequential extraction of floor sediments in the two lakes shows that the bioavailable arsenic contents change between them. In ZA, the sediments show high concentrations of lead and arsenic compared to the ZL1 sediment since it is surrounded by mining waste tailings, which are rich in these elements. An arsenic leaching test of ZA sediment shows that bioavailable arsenic is distributed in equal proportion between clay/carbonates, sulfide-organic matter and iron oxide phases, while in ZL1, most of the arsenic is linked to hydrous iron oxides. Supplementary material: Information on quality control/quality insurance for the used analytical techniques, and additional figures 9–13 are available at https://doi.org/10.6084/m9.figshare.c.5545316 Thematic collection: This article is part of the Hydrochemistry related to exploration and environmental issues collection available at: https://www.lyellcollection.org/cc/hydrochemistry-related-to-exploration-and-environmental-issues

A new solution 31P NMR sample extraction scheme for freshwater ecosystem sediments.

A new approach for the extraction of organic phosphorus (Po) from freshwater sediments, which can be used in solution 31P nuclear magnetic resonance spectroscopy (31P NMR), has been developed and optimized. This approach addresses three important factors for sediment extraction: pH, organic matter (OM), and paramagnetic ions. We classified the sediments according to the pH, OM, and paramagnetic ions (acidic: pH < 7, alkaline: pH > 7; low OM: OM < 100 g·kg-1, high OM: OM > 100 g·kg-1; non-calcareous: Ca/(Fe + Al) < 0.5, calcareous: Ca/(Fe + Al) > 0.5). The 0.25 and 0.5 mol·L-1 NaOH were optimum concentration for acidic and alkaline sediment extracted, respectively. The ratio of sediment to extraction remains at 1:10 (w:v) which exhibited higher extraction efficiency compared with 1:5 and 1:20 for both low and high OM sediments. Use of 25 mmol·L-1 and 50 mmol·L-1 ethylenediaminetetraacetic acid (EDTA) was optimal for Po extraction from non-calcareous and calcareous sediments, respectively. A useful extraction ratio table was developed through systematic orthogonal experiment. This new approach will allow 31P NMR to be more efficiently used for freshwater Po analysis and will help answer questions regarding to the fate and function of Po in freshwater sediments.

Key factors influencing metal concentrations in sediments along Western European Rivers: A long-term monitoring study (1945–2020)

Since 1945, a large amount of heterogeneous data has been acquired to survey river sediment quality, especially concerning regulatory metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Large-scale syntheses are critical to assess the effectiveness of public regulations and the resiliency of the river systems. Accordingly, this data synthesis proposes a first attempt to decipher spatio-temporal trends of metal contamination along seven major continental rivers in Western Europe (France, Belgium, Germany, and the Netherlands). A large dataset (>12,000 samples) from various sediment matrices (bed and flood deposits – BFD, suspended particulate matter – SPM, dated sediment cores – DSC) was set up based on monitoring and scientific research from the 1950s to the 2010s. This work investigates the impact of analytical protocols (matrix sampling, fractionation, extraction), location and time factors (related to geology and anthropogenic activities) on metal concentration trends. Statistical analyses highlight crossed-interactions in space and time, as well as between sediment matrices (metal concentrations in SPM ≃ DSC > BFD) and extraction procedures (also related to river lithology). Major spatio-temporal trends are found along several rivers such as (i) an increase of metal concentrations downstream of the main urban industrial areas (e.g. Paris-Rouen corridor on the Seine River, Bonn-Duisburg corridor on the Rhine River), (ii) a long-term influence of former mining areas located in crystalline zones, releasing heavily contaminated sediments for decades (Upper Loire River, Middle Meuse section), (iii) a decrease of metal concentrations since the 1970s (except for Cr and Ni, rather low and stable over time). The improvement of sediment quality in the most recent years in Europe reflects a decisive role of environment policies, such as more efficient wastewater treatments, local applications of the Water Framework Directive and urban industrial changes in the river valleys.

Sediment quality assessment combining chemical and biological (non)target analysis.

Aquatic sediments act as a storage for diverse mixtures of organic and inorganic contaminants. Nevertheless, most evaluations of contaminated sediments have been limited to the assessment of concentrations of target compounds and lethal effects on some test species. To identify the organic contaminants causing sub-lethal effects of contaminated sediment, this study combined chemical and biological (non)target analysis involving comprehensive two-dimensional gas chromatography coupled with a time-of-flight Mass Spectrometer (GCxGC/ToF-MS) analysis, embryonic malformation and high-throughput sequencing (RNA-seq) analysis on developing flounder. Polycyclic aromatic hydrocarbons were more abundant in the sediment extract of Yeongil Bay (SEY), while Jinhae Bay (SEJ) was contaminated with a large amount of unidentified chemicals. The unidentified chemicals of SEJ included branched alkanes, oxygenated cycloalkanes, heterogeneous hydrocarbons, and other unknown compounds. Percentage of pericardial edema was the highest in embryonic flounder exposed to SEY. Consistent with the morphogenesis results, the expression level of genes related to heart formation including the nkx2.5 and robo1 was greater in embryonic flounder exposed to SEY. In the analyses of differential gene expression profiles (cutoff P < 0.05), by RNA-seq, embryos exposed to SEJ showed changes related to cell differentiation, cell part morphogenesis, neurogenesis, and neuron development. Genes related to neurogenesis and positive regulation of molecular functions variated significantly in embryos exposed to SEY. These results demonstrated the advantages of combining target and non-target analysis to accurately evaluate the major chemical groups causing sediment toxicity. Therefore, this work provided a useful approach to tracking and revealing the causes of toxic effects and identifying potential toxic mechanisms.

Emerging contaminants and priority substances in marine sediments from Cartagena Bay and the Grand Marsh of Santa Marta (Ramsar site), Colombia

Emerging pollutants and priority substances are of growing concern due to their toxicity potential to aquatic organisms and human health. However, few reports on this issue in marine ecosystems in general and, more specifically, on the Colombian Caribbean coast are available. The aim of this study was to detect these compounds in sediments from Cartagena Bay (CB) and in the Grand Marsh of Santa Marta, GMSM (Ramsar site), in order to determine how they related to in vitro cytotoxicity assays on HepG2 cells of sediment extracts. A total of thirty compounds were detected using GC–MS/MS in fifteen stations during both the rainy and the dry seasons. Sediments from CB had a wide range of different toxicants, with polycyclic aromatic hydrocarbons (PAHs) being the most prevalent (12 PAHs, 5.5–881.6 ng/g). Total PCBs ranged from < LOD to 18.6 ng/g, with PCB 138 being the most common detected congener. Residues of p,p′-DDE, Chlorpyrifos and two organophosphate flame retardants, TEHP and ToTP, were found in most sampling locations. The UV filters 4MBC and homosalate were recurrently found in sediments, and the fragrance galaxolide appeared in all cases, with the greatest concentrations found on a touristic beach. In GMSM, with the exception of deltamethrin, all chemicals evaluated had lower average values than in CB. According to sediment quality guidelines, some sites in CB presented values of PAHs higher than the threshold effects level, while in the marsh, none of the stations exceeded it. HepG2 cells exposed to 1% sediment extracts presented reduced cell viability up to 26%. Cytotoxicity displayed a negative correlation with chlorpyrifos concentration. In short, these data suggest the bay and the marsh have specific contamination fingerprints related to anthropogenic interventions. This research highlights the need to further investigate the ecotoxicological implications of detected chemical stressors in these ecosystems.Supplementary InformationThe online version contains supplementary material available at 10.1007/s10661-021-09392-5.

Potential catastrophic water outflow from Lake Dian, China: Possible hydrological and ecological risks

Lake Dian, the largest lake on South China’s Yunnan-Guizhou Plateau, exhibits two abnormal funnel-like features in the deepest part of the lake. Nevertheless, how and when these funnels formed and their implications and potential environmental and ecological effects remain unclear. To address these questions, we carried out a detailed multi-method survey including underwater topographic monitoring, extraction of sediment records, and geophysical exploration across the funnel areas. Sediment records revealed a significant sedimentation hiatus around these features. For example, sediments with thicknesses of ca. 69.24 cm and 83.56 cm in cores D4 and D6 were eroded based on the calculated of sedimentation rates. Deformed sedimentary structures and a hiatus, together with large-scale funnel-shaped topography, prove that underlying karst collapse may trigger massive water outflow through these funnels, which could result in an erosional hiatus in the local lakebed. Continuous clay deposits in the upper part of the sedimentary column suggest that water leakage may have ceased since the 1930s. However, bathymetric surveys conducted in October 2015 and September 2019 indicated that the maximum lake depth increased by 0.97 m and 0.2 m in the large and small funnels, respectively, over this 4-year period. The corresponding increased volumes were 1520 m3 and 375 m3 in the large and small funnels, respectively. Numerous pits were distributed around the funnels. Cumulatively, these underwater topographic changes reveal that small-scale, slow water leakage has been developing, which could potentially trigger catastrophic water discharge due to increasing hydraulic pressure and/or underlying karstification. If catastrophic water outflow occurs, ~14.05 × 108 m3 of highly polluted water would not only contaminate the upper reaches of the large river and/or the lake itself, but would also endanger regional water security and induce widespread negative ecological impacts.

Toxicity assessment of urban marine sediments from Western Norway using a battery of stress-activated receptors and cell-based bioassays from fish

A luciferase reporter gene-based bioassay battery consisting of stress-activated receptors from fish, complemented with traditional fish cell-based bioassays, were used to assess the toxicity of marine sediment samples from the Byfjorden area around the city of Bergen (Norway). The reporter assays covered a wide range of cellular signalling and metabolic pathways, representing different molecular initiating events in the adverse outcome pathway framework. Cytotoxicity, generation of reactive oxygen-species, and induction of 7-ethoxyresorufin-O-deethylase activity were analysed using fish liver and gill cell lines. Chemical analyses of the sediment extracts revealed complex contamination profiles, especially at the innermost stations, which contained a wide array of persistent organic pollutants, polycyclic aromatic hydrocarbons, and metals. Sediment extracts from these sites were more potent in activating the stress-activated receptors than the other extracts, reflecting their toxicant profiles. Importantly, receptor- and cell-based bioassays complemented the chemical analyses and provided important data for future environmental risk assessments of urban marine sediments.

Pingo drilling reveals sodium–chloride‐dominated massive ice in Grøndalen, Spitsbergen

AbstractDrilling of a 21.8‐m‐deep borehole on top of the 10.5‐m‐high Nori pingo that stands at 32 m asl in Grøndalen Valley (Spitsbergen) revealed a 16.1‐m‐thick massive ice enclosed by frozen sediments. The hydrochemical compositions of both the massive ice and the sediment extract show a prevalence of Na+ and Cl− ions throughout the core. The upper part of the massive ice (stage A) has low mineralization and shows an isotopically closed‐system trend in δ18O and δD isotopes decreasing down‐core. Stage B exhibits high mineralization and an isotopically semi‐open system. The crystallographic structure of Nori pingo’s massive ice provides evidence of several large groundwater intrusions that support the defined formation stages. Analysis of local aquifers leads to suggest that the pingo was hydraulically sourced through a local fault zone by low mineralized sodium–bicarbonate groundwater of a Paleogene strata aquifer. This groundwater was enriched by sodium and chloride ions while filtering through marine valley sediments with residual salinity. The comparison between the sodium–chloride‐dominated massive ice of the Nori pingo and the sodium–bicarbonate‐dominated ice of the adjacent Fili pingo that stands higher up the valley may serve as an indicator for groundwater source patterns of other Nordenskiöld Land pingos.

The impact of DNA extract homogenization and replication on marine sediment metabarcoding diversity and heterogeneity

AbstractMetabarcoding of environmental DNA (eDNA) is an attractive complement to morphological methods for surveys and routine monitoring of marine sediment benthic communities. However, metabarcoding and other genetic techniques are heavily affected by choices made during sampling, processing, and analysis. Here, we investigated the effect of different eDNA extraction protocols on observed alpha‐ and beta diversity of replicates from the same grab. Specifically, we compared (A) homogenization intensity during sediment DNA extraction, (B) extraction replicates vs larger sediment extraction volume, and (C) pre‐ and post‐PCR extract pooling. Using the 18S V1‐V2 region marker, we show that a Precellys homogenizer protocol during DNA extraction can significantly improve sediment metabarcoding results in terms of captured diversity and inter‐replicate homogeneity compared to vortexing only. This effect superseded that of increased sediment extract volume. Pre‐PCR pooling of DNA extraction replicates increased observed rarefied richness compared to data from single extracts only, but not to the extent of sample extract replicates amplified individually before pooling. We argue that this discrepancy was due to a reduction both in recovered sample diversity, but also the number of PCR artifacts and PCR drift. Our results demonstrate that extraction replicates of smaller sediment volumes, in combination with moderate Precellys homogenization and pre‐PCR pooling, are a cost‐effective way to increase the amount of organism diversity that is recovered from sediment eDNA metabarcoding samples.

Geochemical partitioning and possible heavy metal(loid) bioaccumulation within aquaculture shrimp ponds

Limited work has been conducted on trace metal(loid) exchange between sediment, water, feed, and shrimp, particularly in estuarine aquaculture environments. To identify metal(loid) sources and the processes controlling bioaccumulation in shrimp, we analyzed paired aquaculture water, sediment, and shrimp samples collected in Southwest Bangladesh in the late dry season (May), as well as several common artificial feeds. Additionally, we analyzed sediment extract samples from 24-hour laboratory batch experiments as an analogue for aquaculture pond sediment porewater to examine element mobilization from pond sediment. Weak correlations between element concentrations in extracts, pond water, and bulk sediment indicate equilibrium with sediment was not achieved in extract experiments or ponds, and that sediment composition has little influence on pond water or shrimp composition. Aquaculture shrimp metal(loid) concentrations were similar to artificial feed but not pond sediment or pond water, suggesting that shrimp composition is mostly influenced by diet. Although arsenic (As) and selenium (Se) were present at high concentrations in shrimp pond waters and sediment, they were often below detection in shrimp. However, the highly toxic metal thallium (Tl) was detected in shrimp at levels that pose significant human health risks based on calculated target hazard quotient (THQ) values. Thus, further research into potential Tl contamination in Bangladesh aquaculture environments is warranted.

Determination of brominated flame retardants including polybrominated diphenyl ethers, pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane in sediment samples: Validation of a rapid and efficient clean-up method and application to a sediment core from Lake Biwa, Japan

The development of rapid and efficient analytical method for the determination of legacy and current-use brominated flame retardants (BFRs) has been performed due to environmental concern related to these pollutants. In the present study, we used an automated clean-up device equipped with pre-packed micro-column sets (containing sulfuric acid impregnated silica gel and silver-modified alumina) to develop an effective purification method for polybrominated diphenyl ethers (PBDEs), pentabromoethylbenzene, hexabromobiphenyl, and decabromodiphenyl ethane (DBDPE) in sediment extracts. Matrix-spiked sediments (n = 6) and the Standard Reference Material® 1944 samples (n = 6) were tested. Our method showed acceptable accuracy, repeatability, and sensitivity for almost all the target compounds with reduced processing time, labor requirement, and solvent amounts as compared to conventional clean-up method (e.g., sulfuric acid treatment and self-packed chromatographic columns). The validated method was applied to sediment core samples (n = 16) collected in 2019 from Lake Biwa, the largest lake in Japan. PBDEs were detected in sediment samples of 0–13 cm depth (dated between 1990 and 2019) at relatively low concentrations (median 5.7; range 2.6–9.4 ng/g dry weight). PBDE profiles were dominated by BDE-209, which accounted for 91 ± 10% of total PBDEs. Among other BFRs, only DBDPE was found in sediment layers of 0–9 cm depth (deposited between 2005 and 2019). DBDPE concentrations ranged from 0.43 to 1.6 (median 0.71) ng/g and showed increasing trend toward shallower depths.

Extended series of tricyclic terpanes in the Mesoproterozoic sediments

Analysis of Mesoproterozoic sediment extracts from the North China Craton by gas chromatography–mass spectrometry metastable reaction monitoring revealed an extended series of C18–C33 13α(n-alkyl)-tricyclic terpanes. This discovery extends the previous known series to C33 with sixteen homologs. Because of the abundant presence of C22 and C27 homologs, and no isomeric peaks for the homologs > C24, it was confirmed that the side chain at the C-13 position is a long-chain n-alkyl group without a methyl substituent or an asymmetric carbon atom. The distribution of the extended tricyclic terpanes in the Mesoproterozoic sediments is mainly controlled by a primitive biological community, probably from certain specific bacteria and/or cyanobacteria. Their biological precursor was probably inhibited by high-salinity water conditions and not evolved during the deposition of the Gaoyuzhuang Formation.

Influence of surface geology on phosphorus export in coastal forested headwater catchments in Akita, Japan

ABSTRACT Surface geology is a key factor regulating the geographical patterns of P export; however, geographically extensive data on P export mechanisms from natural coastal mountain regions are lacking. We compared stream-water characteristics in forested headwater catchments with different types of surface geology (marine sedimentary rocks [MSRs] and igneous rocks [IRs]) and evaluated the factors regulating soluble reactive phosphorus (SRP) concentrations in stream water. Geographically extensive stratified sampling was conducted: stream-water and sediment samples were obtained from 66 MSR catchments and 55 adjacent IR catchments along the coastal forested mountain regions in Akita, Japan. SRP and major cations and anions in stream waters were analyzed. To evaluate the effect of ionic composition on SRP, sediments were extracted with NaCl and CaCl2 solutions and the SRP concentrations in the extracts were measured. Stream SRP was significantly higher in MSR catchments (median 23 µg L−1) than in IR catchments (median 8 µg L−1) (P < 0.001), and tended to be higher in MSR catchments with younger rocks. Dissolved inorganic nitrogen (DIN) did not differ between catchments with different geologies; therefore, DIN/SRP was significantly lower in MSR catchments (median 18), close to the Redfield ratio. On a Piper diagram, high-SRP stream waters were of the NaCl water type, and stream SRP was significantly correlated with Na+ (r = 0.642, P < 0.0001). In IR catchments, stream waters had relatively higher Ca2+ and Mg2+ concentrations. SRP in the sediment extracts was significantly higher in MSR catchments and samples obtained by NaCl extraction than in IR catchments and CaCl2-extracted samples. Exchangeable Na+ in sediments was significantly higher in MSR catchments, decreasing Ca2+ in the liquid phase by an ion-exchange reaction, which is likely also key in maintaining high SRP levels. We conclude that MSR catchments in coastal Akita are a significant P source for streams even in headwater forests, and that site-specific NaCl water types and higher exchangeable Na+ concentrations in sediments result in higher SRP concentrations in stream waters. These results have critical implications for P cycles in freshwater ecosystems influenced by Na+.

PAH-pollution effects on sensitive and resistant embryos: Integrating structure and function with gene expression.

Polycyclic aromatic hydrocarbons (PAHs) are among the most widespread natural and anthropogenic pollutants, and some PAHs are proven developmental toxicants. We chemically characterized clean and heavily polluted sites and exposed fish embryos to PAH polluted sediment extracts during four critical developmental stages. Embryos were collected from Fundulus heteroclitus populations inhabiting the clean and heavily polluted Superfund estuary. Embryos of parents from the clean sites are sensitive to PAH pollutants while those of parents from the heavily polluted site are resistant. Chemical analysis of embryos suggests PAH accumulation and pollution-induced toxicity among sensitive embryos during development that ultimately kills all sensitive embryos before hatching, while remarkably, the resistant embryos develop normally. The adverse effects on sensitive embryos are manifested as developmental delays, reduced heart rates, and severe heart, liver, and kidney morphological abnormalities. Gene expression analysis of early somitogenesis, heartbeat initiation, late organogenesis, and pre-hatching developmental stages reveals genes whose expression significantly differs between sensitive and resistant embryo populations and helps to explain mechanisms of sensitivity and resistance to polluted environments during vertebrate animal development.

The In Vitro Proinflammatory Properties of Water Accommodated Sediment Extracts from a Creosote-Contaminated US Environmental Protection Agency Superfund Site.

The southern branch of the Elizabeth River near Portsmouth, Virginia, USA, is one of the most creosote-polluted subestuaries in North America and the former location of the Atlantic Wood US Environmental Protection Agency Superfund site. We previously demonstrated that adult Atlantic Wood killifish collected in situ had severe hepatic lesions, including hepatoblastoma and hepatocellular carcinoma, as well as suppressed circulating antibody responses compared to a historical reference site. Moreover, several innate immune functions were higher in Atlantic Wood fish, including elevated expression of hepatic cyclooxygenase-2 (COX-2), suggesting a proinflammatory environment. To further examine the potential of Atlantic Wood contaminants to modulate innate immune function(s), the present study used RAW264.7 mouse macrophages as an in vitro model to develop new approach methodologies for rapid screening. Lipopolysaccharide (LPS)-stimulated nitric oxide secretion by macrophages is a rapid, sensitive, and predictive in vitro system for screening potentially immunotoxic contaminants as single compounds or as complex mixtures. Compared to the reference site, filter-sterilized Atlantic Wood sediment extracts (water accommodated fractions) induced nitric oxide and IL-6 secretion as well as inducible nitric oxide synthase and COX-2 proteins at levels comparable to or higher than those induced by LPS treatments alone. Extracts also increased phagocytic activity by macrophages. Using a limulus lysate assay, we show that bacterial endotoxin levels in Atlantic Wood extracts are higher than in reference extracts and that polymyxin-B chelation ameliorates proinflammatory effects. These findings illuminate the reality of sediment constituents other than toxic compounds previously associated with developmental abnormalities and carcinogenesis in killifish from the Atlantic Wood site. Perhaps these data also suggest the presence of contaminant-adapted consortia of sediment microbes at many heavily polluted sites worldwide compared to less contaminated sites. Environ Toxicol Chem 2021;40:1576-1585. © 2021 SETAC.

Mercury in soils impacted by alluvial gold mining in the Peruvian Amazon

Gold mining is the largest source of mercury (Hg) pollution worldwide. The discharge of mercury in the environment bears direct human health risks and is likely to increase cascading effects throughout local food chains. In the Peruvian Amazon the mining process consists of slashing and burning trees, followed by extraction of gold-bearing sediment, amalgamation with Hg and gold recovery, leading each year to the degradation of 6,000-10,000 ha and the release of 180 metric tons of Hg per year to the enviroment. The purpose of this study was to determine soil Hg levels in soils of abandoned alluvial gold mine spoils and undisturbed forest in the Madre de Dios region, the epicenter of alluvial gold mining in Peru. We selected gold mine spoils of the two most important technologies locally applied for gold extraction, i.e., Minimally Mechanized Mining (MMM) and Highly Mechanized Mining (HMM), in the native communities of Laberinto and Kotzimba, respectively. We collected 127 and 35 soil samples (0-20cm depth) from potentially contaminated sites and undisturbed forest, respectively. Physicochemical analysis and determination of Hg levels were determined for all soil samples. None of the samples had Hg concentrations above Peruvian, Canadian and British Environmental Quality Standards for Agricultural Soil (6.6mg/kg). Hg levels in MMM and HMM were not significantly different between the two areas. The main variables explaining variation of soil Hg concentrations were the vegetation cover, soil organic matter, soil pH and clay particle content, which explained up to 80% of data set variation. Surprisingly, highest Hg concentrations were found in untouched old-growth forest bordering the mine spoils, but there was also a trend of increasing Hg concentrations with the regenerating vegetation. Our findings suggest that Hg concentrations in old mine spoils are low and shouldn’t stand in the way of efforts to restore soil conditions and develop sustainable land uses. However, it is urgent to end the use of Hg in mining operation to decrease human and environmental risks.