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Despite of the importance of understanding the sediment quality for lacustrine management, the source evaluation of sedimentary organic matter (SOM) in freshwater lakes is still insufficient. In this study, two shallow eutrophic lakes of Lake Taihu, China and Lake Izunuma, Japan were systematically investigated. Results of fatty acid profiles demonstrated that a wide range of organic matters, varying ecotypically, was inputted into the sediments of both lakes. Interestingly, there was a strong contribution from terrestrial plants to the sediments across ecotypes, with an approximate input from bacteria, and a relatively minor input from microalgae mainly included cyanobacteria, green algae, diatom and dinoflagellates. In addition, isotopic mixing model depicted a complementary picture that a significant, but spatially variable, amount of organic matter was derived from emergent and floating-leaf plants of Phragmites, Nelumbo, Nymphoides and Trapa L in Lake Izunuma. A general indicator selection procedure for the source assignments of SOM in freshwater ecosystems was therefore proposed: fatty acids could be a valid biomarker when the potential sources are unknown or unavailable; stable isotopes could be an effective supplement approach when assessing the special or defined organic sources.

Despite of the importance for tracking sources and fates of organics in determining carbon cycling and assessing the overall health of lacustrine ecosystems, little is known of organics behaviors in shallow eutrophic lakes. In this study, for relating the benthic organics to pelagic sources, an ecosystem-level investigation was performed in hypereutrophic Lake Taihu, China, by using source-specific fatty acid biomarkers on the molecular level. Results exhibited the unexpected asymmetric phenomena of organics between surface water and sediments. In the abundance, the dominant organics shifted from cyanobacteria in surface water to terrestrial plants in sediments. In the spatial pattern, as opposed to terrestrial plants, cyanobacteria were found not site-to-site symmetrical, although both of their spatial distributions varied strongly. Essentially, these asymmetric phenomena ascribed to a more considerable loss of cyanobacteria compared to terrestrial plants during sinking, caused by aquatic animal consumption and microbial utilization with different degree. Combined dual stable isotopes (δ13C and δ15N) and fatty acid biomarkers revealed that there were only subtle differences in the diets of benthic and pelagic animals and cyanobacteria were their main food source. Concomitantly, results of δ13C of bacteria-specific fatty acids demonstrated that bacteria equally and profoundly affected organics accumulation or preservation in the sediments, because they preferentially utilized labile cyanobacteria as their carbon source instead of terrestrial plants (>95% within these two sources). Consequently, these novel findings clarify that not only in deep lakes, but also shallow eutrophic ones, the extensive losses of autochthonous organic matter can be expected during sedimentation coupling with the dramatical modifications of biogeochemical processes.

Although an understanding of the quantity and quality of sedimentary organic matter (SOM) pools is necessary to design sound environmental management strategies for lacustrine systems, the characterization of organic matter sources and the assessment of their relative contributions to eutrophic and inland lake sediments remain insufficient. In this study, the contribution of potential organic matter sources to sediments in shallow and hypereutrophic lake Taihu, China was assessed on the molecular level using source-specific fatty acid biomarkers. The results indicated that SOM was composed mainly of terrestrial plants with a maximal contribution of 45.3 ± 2.4% to the total organic carbon, which accounted for approximately 66% among the determined organic matter sources. Evidence suggests the terrestrial plants remained in a fresh state in surface sediments: the correlation ( R 2 = 0.62, p R 2 = 0.60, p

After the tsunami caused by the Great East Japan Earthquake, marine sediment was taken from the sea bottom and deposited over local agricultural fields. The marine sediment already contained an unknown amount of heavy metals, due to anthropogenic activities prior to the tsunami, which might affect plants, animals, and humans. Furthermore, soil salinity in tsunami-inundated land greatly increased. Three different amounts of steel slag were employed as pretreatment agent in order to improve agricultural soil quality. The soil samples treated with 2% of steel slag present a remarkable increase of A. thaliana biomass production with low BCF and TF values for most of the heavy metals. It was concluded that steel slag pretreatment used in the tsunami-inundated agricultural lands produced a noteworthy improvement in soil quality which lead to a positive stimulative effect on plant growth, and the slag addition treatment proved to be a promising treatment that might be used for phytostabilization of slightly contaminated soils.

The impacts of human-induced changes in coastal environments on shellfish farming need to be mitigated. Suspended farming species, such as oysters, greatly impact planktonic communities and benthic environments via filter feeding and bio-deposition. To more effec-tively manage coastal environments and achieve ecologically sustainable shellfish farming, interactions between coastal marine environments and aquaculture activities need to be properly assessed. We examined interactions between coastal biogeochemical environments and suspended oyster farming in Shizugawa Bay of northeastern Japan. We found that particulate organic matter (POM) produced at the oyster farm (e.g., exfoliated periphyton and/or oyster feces) locally increased the concentrations of chlorophyll a and daytime dis-solved oxygen in the bottom layer. Based on the estimated budget of POM at the bay scale, the oyster feeding rate was a couple of orders of magnitude lower than the net primary production and POM inputs at the bay boundaries (e.g., offshore and in rivers). The rela-tively high exposure of the bay and high seawater mixing rate may explain the lack of mac-roscale environmental impacts of oyster cultures at the bay scale. We also found that despite the oligotrophic environment, the oyster growth rate was higher in the bay, compared with previous estimates in other coastal areas. To understand the mechanisms sustaining the production of phytoplankton and oysters, further examinations from the perspective of nu-trient cycling in the bay are required.

The quantity and quality of sedimentary organic matter (SOM) in relation to material and energy flows are crucial for understanding the current state and future development of lake systems, yet, characterization of organic matter sources and assessment of their relative contributions in different trophic-state lakes caused by anthropogenic impacts are scarcely known. In this study, for obtaining information concerning the source of SOM and its compositional diversity along different trophic gradients, a total of thirty-one sampling sites from four freshwater lakes located in China and Japan were performed by the molecular level analysis using source-specific fatty acid biomarkers. Results indicated that SOM in these lakes was composed of microalgae-, aquatic plant-, terrestrial plant- and bacteria-derived organic matters based on their fatty acid profiles. The scatter plot matrix exhibited correlations between these sources, however, only terrestrial plant-derived organic carbon was a well predictor for sediment TOC with strong, spatiotemporal dynamics. The source and composition of SOM were evidently influenced by lake trophic state with redundancy analysis. Moreover, increase of lake trophic state led to the relatively higher contribution of aquatic organic matter sources to SOM pool compared with terrigenous sources, as evidenced by significant correlations between the trophic state index [TSI (TP)] and the ratio of terrigenous to aquatic fatty acids (TARFA ratio). Yet, this changing trend became more gradual with higher trophic state and prevented the occurrence of regime shift from allochthonous to autochthonous dominant state by a threshold (0.683) of TARFA ratio. Together, a conceptual diagram was proposed, which highlighted the prevailing state of allochthonous source and implicated sedimentary organics in biogeochemistry cycle within freshwater lakes.

The aim of this investigation was to evaluate the effect of different velocity gradient and rapid mixing time on coagulation and floc properties, using polysilica iron (PSI) and polyaluminum chloride (PACl) with different rapid mixing speeds and times. The growth, breakage, and re-growth of flocs were monitored by a particle-size analyzer during the rapid mixing, in order to determine the underlying mechanisms. For PSI and PACl, three different zones were found to depending on the G value in the coagulation process. At low G values (G 546 s−1 for PSI flocs and G > 390 s−1 for PACl flocs), breakup dominated over floc formation. Broken flocs did not fully re-grow after breakage, probably as a result of a change...

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The spatial variability of the food availability in different depositional environments (Nanakita estuary, Japan) was investigated using fatty acid biomarkers. The main objective of the present study was to determine the food availability for Nuttallia olivacea and Hediste spp. in connection with the depositional environment of organic matter (OM). Sandy sediment was mainly occupied by diatoms, bacteria and marine organic matter. Meanwhile, muddy sediment is dominated by diatoms, bacteria and terrestrial organic matter. The main food sources and food availability for N. olivacea were mostly dominated by diatoms, bacteria and dinoflagellates in connection with the depositional environment. Meanwhile, the food utilization characteristics of Hediste spp. may be attributable to the lower food selectivity due to their deposit feeding. From these results, the food availability for N. olivacea was more influenced by the depositional environment in estuarine tidal flat than Hediste spp.

The effluents discharged from sewage treatment works (STWs) are major sources of environmental estrogens, which poses an urgent need to explore appropriate techniques for effluent-polishing. In lig...

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An experimental study was conducted to establish the control strategy of an anoxic-oxic sequencing batch reactor system (AOSBR) using a specific feature of N2O generated during the anoxic and oxic phases. Since NH4+-N, NO2--N and gaseous N2O (GN2O) were found to disappear simultaneously in the oxic phase, the end point of nitrification may be detected from the GN2O profile. It was suggested that the stagflation of nitrification and denitrification could be detected by abnormal GN2O emission in the oxic and anoxic phases. Compared with the conventional indexes of AOSBR, GN2O has several advantages. First, the regulation of GN2O emission could be conducted directly, and second maintenance is easier than conventional indexes because the GN2O monitoring system is more durable than the monitoring system for water quality.

Mesocosm-scale vertical subsurface flow constructed wetlands (SSF, 0.5 m length, 0.3 m width) with different reed-bed thickness, including standard SSF (SD, 0.6 m deep), shallow SSF (S, 0.3 m deep) and extremely shallow SSF (ES, 0.075 m deep) were set up at sewage treatment plant and their nutrient removal efficiencies from the sewage plant effluent were compared under three hydraulic loading rate (HLR) conditions of 0.15, 0.45 and 0.75 m3 m−2 d−1. A very interesting characteristics was found for the extremely shallow SSF, in which a high nitrogen removal efficiency was obtained despite the effective hydraulic retention time was only 1/8 times as long as the standard SSF. The results of kinetic analysis confirmed that the high volumetric nitrogen removal efficiency observed in the extremely shallow SSF did not depend on high response against the water temperature but on much higher basic nitrogen removal activity compared with other SSF. The phosphorus removal depending on the adsorption to sand in the reed-bed filter was, however, the lowest in the extremely shallow SSF although the volumetric removal efficiency was much higher compared with other SSF. Results of morphological analysis of rhizosphere collected from respective reed-bed suggested that the extremely shallow SSF lead to a very high-density rhizosphere, resulting in a high basic nitrogen removal activity and volumetric phosphorus removal efficiency.

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The effects of bacterial activity on the degradation of estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2) in nitrifying activated sludge (NAS) were studied with different substrates and organic loading rates (OLRs) and low temperature conditions. Heterotroph was shown to have utilized glucose prior to E1 for metabolism. The co-metabolism of ammonia oxidizing bacteria (AOB) dominated the degradation of E1, E2 and EE2 in NAS. The higher the organic loading, the higher the rate of organic matter transformation, with less ammonia oxidation and less degradation of E1, E2 and EE2. The degradation of E3 in NAS was shown to be largely due to heterotroph metabolism. On the basis of the difference of apparent activity between heterotroph and AOB at 4 degrees C, the process of estrogen degradation via the co-metabolism of AOB was able to be identified.

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The terrestrial plant Luffa cylindrica was applied to a surface-flow-constructed wetland (SFCW) to treat effluent from rice fields. To control the excessive growth of weeds that interfere with the maintenance of SFCWs, SFCWs with and without shading were constructed and the effect of shading was investigated. The average removal efficiencies of T-N and T-P for 135 day operation of the SFCW with shading were 57 and 53%, respectively, while in the case of those without shading were 44 and 41%, respectively. This result indicates that the nutrient removal efficiency was stimulated by shading. Although L. cylindrica completely dominated the SFCW with shading, the total plant biomass production including weeds was higher without shading. The total length of the roots in the SFCW with shading was, however, 2.2-fold that without shading. Consequently, it was suggested that the longer root length observed in SFCW with shading promoted the sedimentation of nutrients, resulting in a nutrient removal efficiency higher than that in the case without shading. These results demonstrate that shading is effective not only to control the growth of weeds but also to enhance the growth of roots in SFCWs, resulting in easier maintenance and a higher nutrient removal efficiency.

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The objective of this study is to assess the importance of algae and algogenic organic substances concerned with the formation of assimilable organic carbon (AOC) during algal growth and chlorination process. Laboratory tests were carried out using cultures of algal species (Phormidium tenue) with different culture medium, M-11 and CT. Extracellular organic matter (EOM) produced during the stationary phase and death phase of P. tenue (106 cells/mL) with M-11 culture medium led to significant increase of the AOC concentration, up to 100 times as high as its initial concentration. In case of CT culture medium containing a high DOC component, the AOC concentration did not increase significantly during P. tenue culture. The formation and removal of AOC derived from EOM and intercellular organic matter (IOM) by chlorination were also examined. The AOC concentration after chlorination of EOM and IOM became maximum with 2 mg/L of chlorine dosage while it decreased with increase of chlorine dosage when the dosage was higher than 2 mg/L, suggesting that necessary chlorine dosage to not form AOC is higher than 2 mg/L.

下水処理水や生活排水と比較して低栄養塩濃度である湖沼水を浄化対象としてヘチマ植栽水路（水路長 25 m，水理学的滞留時間3.8時間）の水質浄化特性を検討した．ヘチマ植栽水路におけるDIPの除去は一次反応であり，その除去速度定数の平均値は 20.8 day-1 に達した．実験期間中に除去されたDINの67％，DIPの90％は，水路に発生した糸状藻類に吸収されていた．糸状藻類はヘチマの根に絡むように存在しており，ヘチマが糸状藻類の発生を促進したことが示唆された．流入栄養塩濃度が低レベルであるにも関わらず既往の植栽浄化施設と比較して高い除去速度が達成できたことから，糸状藻類が発生したヘチマ植栽水路が低濃度の栄養塩の高度処理能力に優れており，富栄養化湖沼水の直接浄化に適した特性を有していることが明らかとなった．

The effect of Tsugaru warm current (TWC) to the variation of temperature and dissolved oxygen (DO) wasinvestigated byfield observation data and sea surface temperature (SST) derived from NOAA/AVHRR data inOhfunato bay. From the field observation data, density intrusion, the phenomenon that outer seawater intrudes thesame density layer in inner bay, was observed under stratified season in Ohfunato bay. Since outer seawatertemperature was sameat the middle layer in inner bay, seawaterexchange occurred at the depthof middle layer. In August, we observed abrupt DOincrease. It seemed to affect ofdensity intrusion. However, this phenomenon didnot affect broken ofoxygen-deficient water mass because DO was consumed by seabed immediately. On the other hand, when typhoon passed through Tsugaru straight at the end of August, temperature changed abruptlywith DO increase. From SST data, it was suggested that Oyashio affect this phenomenon.In the end of oxygen-deficient water mass disappearance period, when temperature of the bottom of inner bay equal to that of outer seawater, DO changed largely. At that time, seeing SST datafrom satellite, the effect of TWC isweaker than in September and outer seawater is also low. Therefore, it was concluded thatthe strength and weaknesscondition of TWC is importantfor anoxic water disappearance.

The mechanism thought to be responsible for the observed fortnightly modulation of estuarine circulation in Tokyo Bay was investigated in December 1998 using a two-layer theoretical model, which was verified using a three-dimensional non-hydrostatic model. The influence of the difference in kinetic energy between the upper and lower layers on estuarine circulation was clarified in terms of vorticity, which was defined by the difference in the velocities of the two layers. The ratio of the difference in kinetic energy between the two layers to the baroclinic energy was attributed to the change in strength of estuarine circulation. Thus, the mechanism for fortnightly modulations of estuarine circulation may be due to the suppression of upper-water withdrawal during spring tide, when the ratio is more than 1, and the enhancement of upper-water withdrawal during neap tide, when the ratio is close to 0.

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The relation between seawater exchange and sea current pattern was investigated. For this purpose, ocean currents conditions were observed in Sanriku Sea off using NOAA/AVHRR data. It was confirmed that density variation is not so much affected by salinity. Therefore, the regression function is derived from observed density and the density which was calculated using constant value of salinity and observed temperature. Using the regression function, σt distribution in Sanriku sea off is evaluated from sea surface temperature data. As the result, the behavior of Oyashio water mass was observed from the σt distribution. Analyzing time series temperature and salinity data in Ohfunato bay, it was confirmed seawater exchange occurred under the influence of Oyashio water mass. It was also observed distributions of chlorophyll-a and nutrient change at this seawater exchange and small density variation affects chlorophyll-a distribution at the depth of middle layer.

Ofunato bay is highly enclosed because of a tsunami breakwater. Therefore, water quality problems, such as eutrophication and ocean anoxic, have been caused in the inside of the bay. Field observation was carried out to clarify the characteristics of water quality in Ofunato bay in 2003 and 2004. The purpose of this paper is to study the seasonal variation characteristics and the load of nutrients. The amount of inflow of nutrients was calculated using the material balance model using field observation data. It shows that a lot of nutrient is released from sediment when anoxic water has occurred. Unusual increase of phytoplankton was observed when river inflow was increased. They have great effect on water quality.

Sea surface current observations with the use of two high-frequency radars were carried out near the mouth of Tokyo Bay, Japan from 1 December to 23 December 1998. A peculiar fortnightly variability of residual flow was found near the mouth of Tokyo Bay, that is, sea surface residual flow was weak and southward in spring tide but it was strong and formed a clockwise circulation in neap tide. Strong sea surface residual flow resulted from large vertical shears of estuarine circulation and small vertical viscosity by weak tidal currents in neap tide. The clockwise circulation was produced by an expansion of horizontal circulation from the river mouth to the bay mouth.

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Field observations were carried out in Banzu intertidal flat in Tokyo Bay throughout two days in the summer of 2000, in order to clarify the spatiotemporal fluctuatuions of water quality during a tidal cycle. Concentrations of DO, ON (TN-DIN) or OP (TP-PO4-P) at the offshore station were higher than those at the onshore station, whereas DIN and PO4-P had an inverse trend, during submergence. During flood tides, an abrupt increase in the concentrations of DIN and PO4-P was observed around a shoreline.We constructed a box model, incorporating both the release flux of inorganic nutrients from sediment and the nutrient uptake rate by overlaying water, that were experimentally obtained in situ at each tide. The observed fluctuation of nutrients during ebb tide was well reproduced by the model. However, agreement was poor during flood tide. These results strongly indicate that the increase in nutrient concentrations during flood tide was attributed to the temporally increased effluxes of nutrients from the sediment and/or the physical resuspension of sediments at the shoreline.The mass balance of TP during a tidal cycle showed that the tidal flat acted as a sink of TP (1μmol·m-2·h-1) during daytime, in turn, source of TP (30μmol·m-2·h-1) during nighttime. The influx of organic N and organic P to the tidal flat and the efflux of inorganic nutrients from the tidal flat were commonly dominant processes when evaluated through a tidal cycle. Possibility that the light intensity during exposure affect the sediment-water flux of nutrients was indicated.

The purpose of this study was to evaluate the influence of pollutant from Coho Salmon cultivation on water quality through analyzing the data of weather and water quality for several years, and to estimate the adequate loading amount into the Shizugawa Bay locating at Miyagi Prefecture.As a result, it was recognized that COD in the bay was improved from 0.94 mg·l-1 to 0.57 mg·l-1, the delta DO in the bay was improved from 0.86 mg·l-1 to 0.55 mg·l-1, maximum COD in the salmon area changed from 1.13 mg·l-1 to 0.68 mg·l-1 and δDO in the salmon area changed from 1.28 mg·l-1 to 0.69 mg·l-1, respectively, at the end of the cultivation time compared with the large cultivation period.From the results of multiple regression analysis, it was showed that the factors affecting the COD in the salmon area were input loading, temperature and duration of sunshine, whereas the factors affecting δDO in the salmon area were input loading, temperature, duration of sunshine and rainfall, respectively. In particular, it was found that both items were great influenced by the salmon cultivation. In addition, through evaluating the prediction equation for the bottom DO in the salmon area, it was suggested that the annual cultivation amount should be restricted by 4,000 ton·y-1 to prevent the bottom water from the deficient water.

The presence of estrone (E1), 17 beta-estradiol (E2) and 17 alpha-ethynylestradiol (EE2) in sewage treatment work (STW) effluent pose a potential risk to aquatic ecosystem. The objectives of this study were to evaluate the effectiveness of vertical-flow wetland as polishing step of conventional wastewater treatment in the removal of estrogens and to examine the effect of sand depth. The highest removal efficiency of 67.8+/-28.0%, 84.0+/-15.4% and 75.3+/-17.6% for E1, E2 and EE2, respectively, was achieved by the shallowest wetland among three constructed wetlands with different filter layer depth (i.e. 7.5, 30 and 60 cm). Together with the result that the performance of wetlands when operating in unsaturated condition was superior to that when operating in water-saturated condition, it is suggested that maintaining sufficient aerobic circumstance in constructed wetlands was important for estrogens removal. Core sampling indicated that the highest efficiency achieved in extremely shallow wetland might be due partly to the highest root density, besides the superior condition for penetration of oxygen. The adsorbed estrogens in sand accounted for less than 12% of the removed estrogens irrespective of the depth, indicating biotic processes play a major role in the estrogens removal.

Brown seaweed Sargassum horneri, a troublesome biomass scattered along the seashore, was utilized as a biosorbent for Pb(II) removal from aqueous solutions. The Pb(II) adsorption by brown seaweed was enhanced by pretreatment with CaCl2, and the Langmuir adsorption isotherm equation showed a maximum capacity of a Qmax of 0.696 mmol/g and ab value of 94.33 L/mmol. Results obtained from the mass-balance equation derived from the simulation model of the Langmuir adsorption isotherm suggested that the adsorption performance of brown seaweed biosorbent was sufficient to reduce the concentration of Pb(II) to meet the range of WHO guideline. The mechanism, as elucidated using pH monitoring, adsorption rate and ion exchange model, involved the rapid pH change of metal solutions that led to high reaction rate and Pb(II) uptake in the first 30 min of the biosorption process. The energy X-ray analysis's result confirmed the sharp reduction of calcium content in the biosorbent after Pb(II) adsorption. The amount of calcium ions released from the biosorbent was about 1.5 times the amount of Pb(II) adsorbed and proved the role of calcium in the ion exchange mechanism. These adsorption equilibrium and mechanistic studies provide useful information for system design and performance prediction of biosorption processes.