140 years-long sedimentary records of PAHs and CN stable isotopes from Ninomiya River, Japan.

Anthropogenic activities' impacts over 140 years were studied at West Nanao Bay using a variety of geochemical techniques on sedimentary records. The bay is influenced by the Ninomiya River which is fed by a small watershed at which Tatzuruhama Town is located. Sedimentation rate was calculated using 210Pb-excess and 137Cs activities. C/N decreased after 1975, indicating a decrease in lignin-rich organic matter. From δ13C, δ15N and biogenic silica it was indicated that the population increased sewage-discharges until the construction of waste-water treatment plant in 1986. Several recorded changes in the landuse matched with the variation of the particle size. Total PAHs concentration was 1.17-62.78 µg g-1, being highest during Japan's fastest economic growth period (1946-1975). Using diagnostic ratios and PCA analysis, PAHs' sources were identified as pyrogenic for all depths, varying from coal combustion (90.7 %) before 1946 to a mixture of biomass and vehicle combustion after 1961.

Environmental processes and fate of PAHs at a shallow and enclosed bay: West Nanao Bay, Noto Peninsula, Japan.

From August 2019 to August 2020, particulate and dissolved polycyclic aromatic hydrocarbons concentrations (PAHs) were analyzed in the water body of West Nanao Bay, Japan, to determinate their levels, environmental pathways, and ecological risks at this remote but shallow and semi-enclosed bay. The 14 targeted PAHs were analyzed by high performance liquid chromatography-fluorescence detector. Even when water column stratifies, the summatory of 14 targeted dissolved PAHs did not follow significantly change with depth. Results agreed with our previous findings in the surface distribution at the bay and can be attributed to long retention time of the water mass of the semi-enclosed bay. Suspended solids start precipitating according to their size; with biggest particles rapidly settling in the proximities of river mouths. Partition coefficients (Kp) varied from 103 to 107, according to molecular weights. In general, highest Kp were found in the nepheloid layer. The risk quotients, RQ∑14 PAHs (NCs) (1.04-174.08), indicated that PAHs represented a very low to low environmental risks.

Geochemical Control of PAHs by Inflowing River Water to West Nanao Bay, Japan, and Its Influences on Ecological Risk: Small-Scale Changes Observed under Near-Background Conditions at an Enclosed Bay.

Polycyclic aromatic hydrocarbons (PAHs), even at low concentrations, have been shown to trigger changes in life cycles and provoke abnormal behaviors in numerous marine organisms. From May 2019 to September 2020, particulate and dissolved PAH concentrations were analyzed on the surface water of West Nanao Bay, Japan, to determinate their levels, emission sources, environmental pathways, and ecological risks at this remote but semi-enclosed bay. The 14 targeted PAHs were analyzed by HPLC-fluorescence detector. Mean total PAH concentrations were lower than 20.0 ng L-1 for most samples. Based on fluoranthene (Flu) to pyrene (Pyr) ([Flu]/[Flu + Pyr]) and benzo[a]anthracene (BaA) to chrysene (Chr) ([BaA]/[BaA + Chr]) isomeric ratios and a varimax rotated PCA, it was established that biomass combustion was the principal source in the particulate phase and that liquid fossil fuel combustion was the principal source in the dissolved phase. From salinity and turbidity distribution, riverine discharges were determined to be the major and continuous transportation pathway of particulate PAHs. It was observed that rain events had a role in the transport of dissolved PAHs. The risk quotients (RQ∑14 PAHs (NCs): 0-84.53) indicated that PAHs represented a very low to low acute environmental risk. The results of this study will contribute to filling the paradigm gap of ecotoxicological studies in remote areas, working as a booster for future in-lab studies of non-lethal implications of endocrine disruptors such as PAHs.

A method for partitioning dissolved polycyclic aromatic hydrocarbons associated with humic substances using polyethylenimine-coated glass fiber filters.

The use of a glass fiber filter coated with polyethyleneimine (PcGF) for partitioning dissolved polycyclic aromatic hydrocarbons (PAHs) that are associated with humic substances (HSs) is reported. The PAHs pass through the PcGF, while HS-associated PAHs are trapped by electrostatic interaction between the HSs and the PcGF. Based on this strategy, free- and associated-PAHs can be separated by simple filtration. Approximately 60-90% of the deuterated benzo[a]pyrene (BaP-d12) that was added to the sample solutions was in the associated form with soil type HAs, while the percentages were lower in the case of aquatic HA (ca. 25%) and FAs (ca. 10-15%). Strong correlations (R 2 = 0.84-0.90) were observed between the %-association for deuterated pyrene (Pyr-d10) or BaP and the degree of HS's aromaticity (log E 280), regardless of the HS fractions or their origins. The separation technique was used to evaluate the association coefficient (log K assoc) and the capacity (C assoc) for soil type HAs based on a Langmuir adsorption model. The log K assoc values were not highly dependent on the origin of the HA (ca. 3.5-4.5). The BaP-d12 and Pyr-d10-C assoc values for the HA derived from compost were more than one order larger than the corresponding values for peat. The findings indicate that C assoc values vary with the origin of the HA and affect the environmental behavior of PAHs. The present study reports on the development of a simple partitioning technique that does not require any special training and equipment.

Biodegradation and Structural Modification of Humic Acids in a Compost Induced by Fertilization with Steelmaking Slag under Coastal Seawater, as Detected by TMAH-py-GC/MS, EEM and HPSEC Analyses.

The compost's humic acid (HA) content decreased when it was fertilized in coastal seawater with steelmaking slag, as confirmed. This study clarified the cause for this change by a detailed analysis of the structural changes in HAs based on the TMAH-py-GC/MS, HPSEC, and 3D-EEM spectra. An increase in the levels of pyrolysates of tannic acid with a low polymerization degree was attributed to the biodegradation of a high polymerized aromatic structure. Moreover, analyses of 3D-EEM, supported by HPSEC, indicated that approximately 20 kDa of the fluorescent matter was generated at the protein-like peaks (Ex/Em = 220/340 and 275/350 nm) in HAs derived from a mixture of compost with steelmaking slag. It would be caused due to the formation of HAs from the bacterial by-product by a catalytic reaction of the steelmaking slag. From these findings reported herein, we conclude that bio-degradation was a major reason for the decreased HA content, and the formation of HA from a part of the degradation products. This would be a reason for the structural modification of HA under the seawater condition.

Mechanism of the Elution of Iron from a Slag-Compost Fertilizer for Restoring Seaweed Beds in Coastal Areas-Characteristic Changes of Steelmaking Slag and Humic Acids Derived from the Fertilizer during the Elution Process.

The characteristic changes in steelmaking slag and humic acids (HAs) derived from a slag-compost fertilizer and their relation to the elution of Fe were evaluated in tank tests in Mashike, Hokkaido and Tsushima, Nagasaki. Analyses of iron, nitrogen and phosphate in the eluate, changes in the chemical states on the surface of the steelmaking slag, and the macro-structural features of the isolated HAs were investigated during the test. Temporal changes in Fe concentrations in the tanks were consistent with data collected in previous studies. Analyses of the surface by 57Fe Mössbauer spectroscopy showed that the concentration of Fe2+ in the fertilizer decreased and the ratio of Fe3+ increased, indicating that Fe2+ was preferentially eluted from the slag surface. The yields of HAs were significantly decreased during the test when steelmaking slag was mixed with compost. Changes in the UV-vis absorptivities indicated that de-aromatization had occurred. These results indicate that microorganisms that were present under these experimental conditions became activated by the mixing of compost with steelmaking slag, and are closely related to the continuous elution of Fe. The residual Fe in the fertilizer after the tests was investigated by analyzing seawater and the levels of extractable Fe. The trends for extractable Fe concentrations were consistent with the results obtained by 57Fe Mössbauer spectroscopy and UV-vis spectra.

Interannual Survey on Polycyclic Aromatic Hydrocarbons (PAHs) in Seawater of North Nanao Bay, Ishikawa, Japan, from 2015 to 2018: Sources, Pathways and Ecological Risk Assessment.

To improve the understanding of the emission sources and pathways of polycyclic aromatic hydrocarbons (PAHs) in the coastal environments of remote areas, their particulate and dissolved concentrations were analyzed on a monthly basis from 2015 to 2018 in surface waters of Nanao Bay, Japan. The concentration of the targeted 13 species of PAHs on the United States Environmental Protection Agency (USEPA) priority pollutant list in dissolved and particle phases were separately analyzed by high-performance liquid chromatography (HPLC) coupled to a fluorescence detector. Particulate and dissolved PAHs had average concentrations of 0.72 ng∙L-1 and 0.95 ng∙L-1, respectively. While most of the samples were lower than 1 ng∙L-1, abnormally high levels up to 10 ng∙L-1 were observed in the winter of 2017-2018 for particulate PAHs. Based on the isomer ratios of Flu to Flu plus Pyr, it was possible to determine that the pyrogenic loads were greater than the petrogenic loads in all but four out of 86 samples. The predominant environmental pathway for PAHs in winter was determined to be long-range atmospheric transportation fed by the East Asian winter monsoon, while for the summer, local sources were more relevant. By the risk quotients method, it was determined that PAHs in surface seawater presented a very low risk to marine life during the interannual survey.

The Use of a Glass Fiber Filter Functionalized with a Double-layer PEI/HA Coating for Removing Trace Levels of Copper from Artificial Seawater.

To avoid degrading the performances related to fuel consumption and maneuverability, an antifouling paint that contains Cu2O as a source of biocidal Cu(II) are applied to the bottom of a ship. However, increasing the Cu(II) concentration around a dockyard located in an enclosed coastal area has been regarded as an environmental issue. The ability of humic acid (HA) and polyethyleneimine (PEI) for complexes with heavy metal ions was examined for removing Cu(II) from contaminated seawater. A glass fiber filter was functionalized by coating it with PEI and HA by taking advantage of the electrostatic character of these substrates. The resulting coated filter proved to be highly effective for removing Cu(II) from artificial seawater by simple filtration. The capacity and efficiency on Cu(II) removal for a filter coated with PEI was increased by further coating with HA. The removal of Cu(II) was dependent on the effectiveness of the coated area, suggesting that this functionalizing method could be applied to other forms of glass fiber materials.

Influence of Land Use on the Structural Feature of Sedimentary Humic Acids in Rivers in Northwest Hokkaido, Japan.

Colloidal organic matter is an important factor in our understanding of the transport of trace metals by rivers to coastal areas and the characteristics of organic matter in the sediment, including the effect of humic substances on the transport of such metals. The structural features of humic acids (HAs) derived from surface sediments collected from the mouths of four rivers in northwest Hokkaido, Japan, were evaluated from the perspective of land use in their basins. The sediments in two rivers (referred to as NS and SK) were lacking in HAs, but the sediments of the others (referred to as SM and PO) contained relatively high levels of HAs. UV-vis spectroscopic characteristics suggested that the HAs in SM and PO contained components derived from humified materials. The PO and SM basins contain rice paddy fields, and TMAH-py-GC/MS analysis showed that the pyrograms of paddy soil HA had a similar character to those of PO-HA and SM-HA samples. Thus, the differences of the structural features can be attributed to the land use in river basins. The findings indicate that the properties of organic river sediments are heavily influenced by the type of land use in the river basins.

Roles of Microbial Activity and Anthraquinone-2,7-disulfonate as a Model of Humic Substances in Leaching of Iron from Hematite into Seawater.

Fertilization with a mixture of steelmaking slag and compost can affect the supply of dissolved iron used to restore seaweed beds, however, the mechanisms of iron elution from the fertilizer are not well understood. In the present study, the microorganism was isolated from Fe-fertilizer incubated in coastal seawater for 6 months, and was identified as Exiguobacterium oxidotolerans by 16S rDNA sequencing. The iron elutability of the bacteria was proved based on the increasing of dissolved iron by incubation with Fe2O3 (hematite) under a seawater-like condition. The value of ORP was changed by inoculated of the bacteria from ca. 0 to ca. -400 mV, which is anticipated concerning to reduction of Fe. The concentration of eluted iron was largely depended on those of organic acids produced by bacteria. From the results, it was proved that E. oxidotolerans is capable of Fe reductive eluting of iron from Fe2O3 into seawater. Anthraquinone-2,7-disulfonate (AQDS), which can play as an electron acceptor/donor between microbe and insoluble Fe2O3 particles, enhanced the effect of iron bio-leaching.

Changes in the Structural Features of Organic Matter Extracted from Compost by the Seawater during a 90-day Period under Anaerobic Conditions, and Its Effect on Oogenesis of Brown Macroalga.

Seawater-extractable organic matter (SWEOM) has a potential to serve as an Fe complexing agent in an Fe-fertilizer intended to restore and preserve macroalgal forests. To better understand the restoration technique, structural alterations in SWEOM that occurred during a 90-day period of incubation in seawater were determined. Up to 82% of the total eluted SWEOM occurred during the initial 30 days; a small amount of SWEOM then continued to elute during the next 60 days. Spectroscopic analyses showed that the high-molecular-weight SWEOM fraction (HMW) altered in aliphatic-rich materials, while the low-molecular-weight fraction (LMW) became significantly enriched in aromatic structures. The structural alterations in the HMW and LMW could be caused by the action of anaerobic microorganisms. In addition, approximately 30 and 60% of the gametophytes were converted to eggs in the presence of HMW and LMW with Fe, respectively.

Thin Alginate Membranes Functionalized with Humic Acids for Removing Traces of Cu(II) from Contaminated Seawater.

Humic acid (HA) could become a useful agent for removing trace amounts of Cu(II) from contaminated seawater. This study reports on the use of a thin alginate membrane (TAM) containing immobilized HA as a Cu(II) binding agent for this purpose. The removal efficiency of Cu(II) by a TAM functionalized with HA was significantly increased compared to TAM alone. In this removal method, HA extracted from hardwood bark compost was more effective in removing Cu(II) than that from peat soil.

Removal of Trace Levels of Cu(II) from Seawater by Co-precipitation with Humic Acids.

To maintain performance related to fuel consumption and maneuverability, the bottom of ships are painted with antifouling paint that contains Cu2O as a biocidal pigment. However, in enclosed coastal areas around dockyards, some of the Cu(II) contained in the paint is eluted into the surrounding water. The present study examined the removal of Cu from seawater by co-precipitation with humic acids (HAs). After precipitating the HA in seawater, the amount of Cu(II) in the supernatant was colorimetrically measured by a colorimetry using bathocuproine. The removal efficiency (RE%) for micromolar Cu(II) increased with increasing initial concentrations of HAs. An RE of 90% was obtained using an HA derived from hardwood bark compost. Aromatic components in the HA that contained highly substituted acidic functional groups appeared to enhance the removal of Cu(II). The findings reported herein indicate that HAs represent a useful material for removing trace levels of Cu from seawater.

Determination of labile Fe(II) species complexed with seawater extractable organic matter under seawater conditions based on the kinetics of ligand-exchange reactions with ferrozine.

A fertilizer, comprised of a mixture of steel slag and compost, was used to restore seaweed beds in barren coastal areas. Complex Fe(II) species, supplied by steel slag, play a significant role in supplying Fe(II) to coastal areas and stimulating seaweed growth. Seawater extractable organic matter (SWEOM) from compost is generally assumed to serve as a chelator of Fe(II) in the fertilizer. It is considered that the bioavailability of Fe(II)-SWEOM complexes is higher in the dissociable (labile) species. In the present study, a method for determining labile species of Fe(II)-SWEOM complexes in seawater (pH 8.0, I = 0.7) was developed. The method is based on a ligand-exchange reaction between SWEOM and ferrozine (FZ). Because Fe(II) is readily oxidized to Fe(III) under normal seawater conditions, ascorbic acid was added as an antioxidant. The coloring for the Fe-FZ complex in the presence of SWEOM was retarded. This retarding can be attributed to a ligand-exchange reaction between FZ and labile Fe(II)-SWEOM complexes. Conditional binding constants for the labile Fe(II)-SWEOM complexes and binding capacities of labile sites in SWEOM to Fe(II) were evaluated for a variety of total Fe(II) concentrations.

Binding characteristics and dissociation kinetics for iron(II) complexes with seawater extractable organic matter and humic substances in a compost.

A steel-slag/compost fertilizer can be useful in supplying complex Fe(II) species to barren coastal regions. Seawater extractable organic matter (SWEOM) was examined for use as a novel chelator of Fe(II) in the compost. The dissociation kinetics for Fe(II)-SWEOM were evaluated, based on the rate of ligand-exchange with ortho-phenanthroline. The ΔH(‡) for the Fe(II)-SWEOM (19 kJ mol(-1)) was significantly smaller than the corresponding values for Fe(II) complexes with humic substances (27 kJ mol(-1)), suggesting that the Fe(II)-SWEOM is kinetically less stable.