Sosuke Otani

Relationship between macrobenthos and physical habitat characters in tidal flat in eastern Seto Inland Sea, Japan.

The investigations were carried out at 6 tidal flats located on the eastern part of the Seto Inland Sea, Japan. This study was focused on physical characteristics of sediments, namely as particle size of sediment and difference in elevation, and generalizes the relationship between sediments and macrobenthos. A total of 192 species were collected at 187 stations at 6 tidal flats. Physical characteristics of sediment were classified into 9 groups by cluster analysis in relation to sediment particle size and difference in elevation. Those groups had also significant difference in physical characteristics of sediments, and were characterized by some specific macrobenthos species. Distribution of macrobenthos can be explained by the classification of physical characteristics of sediment. These findings show the possibility to predict the variety of macrobenthos community using the physical characteristics of sediment.

Phosphorus recovery: minimization of amount of pharmaceuticals and improvement of purity in struvite recovered from hydrolysed urine

Struvite (MgNH4PO4·6H2O) is normally used as a fertilizer in agriculture, where struvite crystallization from hydrolysed human urine is a simple and reliable method for phosphorus (P) recovery. Human urine, however, contains high amount of pharmaceuticals, which may cause health risk for applications. This research investigates the possibility of decreasing the amount of pharmaceuticals (tetracycline, demeclocycline and oxytetracycline) in struvite crystals recovered from synthetic and human urines by focusing on storage time, and of increasing the quality of struvite production. Urines were stored for different times up to 15 days prior to recovery of phosphorus by two steps, spontaneous precipitation and struvite crystallization. The morphology of spontaneous precipitates and struvite crystals was observed. Spontaneous precipitation removed around 17–24% of phosphate from synthetic and human urines, while pharmaceuticals were removed with a quite high amount at a short storage time (5 days) and this amount decreased with increasing the storage time (10 and 15 days). Urines with>70% remaining phosphates were re-used for struvite crystallization by adding extra magnesium. It was found that maximum P-recovery efficiency could be achieved from struvite crystallization at 5-day storage time, 70% and 68% of remaining P in the separated supernatant from synthetic and human urines, respectively, whereas less than 1% pharmaceuticals remained in the struvite crystals from both samples. This indicates that the procedure in this work is a good method for phosphorus recovery, in which high struvite purity (>99%) is obtained with low amount of pharmaceuticals.

Effect of magnesium dose on amount of pharmaceuticals in struvite recovered from urine

Phosphorus (P) recovery was carried out through struvite precipitation from urines. Human urine, however, contains not only high nutrients for plants, such as P and nitrogen, but also pharmaceuticals and hormones. In this work, effects of magnesium (Mg) dose (in terms of Mg:P ratio) on P recovery efficiency and pharmaceutical amounts contained in struvite were investigated. Batch-scale experiments of synthetic and human urines revealed that struvite precipitation formed more X-shaped crystals with an increased molar ratio of Mg:P, while the amount of pharmaceuticals (tetracycline, demeclocycline, and oxytetracycline) in struvite decreased with an increased molar ratio of Mg:P. The lowest pharmaceutical amounts in struvite were found at the Mg:P ratio of 2:1 from both samples. Moreover, the maximum P recovery efficiency, quantity and purity of struvite were found in the range of 1.21 to 2:1. It indicated that the molar ratio of Mg:P has a significant impact on struvite precipitation in terms of pharmaceutical amounts in struvite; morphology, quantity and purity of struvite; and P recovery.

Occurrence of micro-organic pollutants on phosphorus recovery from urine

Increased population growth and food prices have resulted in more demand for fertilizers, especially phosphorus (P), to be used in agriculture and production of food crops. Phosphorus is one of the important natural resources and will be exhausted in the near future. Nowadays, struvite production is a good method to recover P from urine. However, the natural urines contain high amounts of micro-organic pollutants which may cause health risks. Therefore, in this contribution, we investigated the amount of micro-organic pollutants in struvite from urine. There are various kinds of pharmaceuticals and hormones which are used in the world. Nevertheless, we focused on 10 pharmaceuticals (amoxycillin, carbamazepine, erythromycin, furosemide, atenolol, ibuprofen, norfloxacin, trimethoprim, tetracycline, and acetylsalicylic acid) and one hormone (17β-estradiol) as representatives. The experiments were carried out with synthetic and natural urines. After the production of struvite, the results from synthetic and natural urine samples showed that only tetracycline, erythromycin, and norfloxacin remained in the struvite, and, especially, tetracycline remained in struvite with quite a high amount.

CO2 Flux in Tidal Flats and Salt Marshes

Tidal flats and salt marshes are sites where CO2 is released to the environment by decomposing organic matter and CO2 is absorbed by vegetation through photosynthesis. It is thought that on balance, carbon is stored in tidal flats and salt marshes. To explore this topic, we reviewed published estimates of air–water, air–sediment, water–sediment, and air–marsh fluxes of CO2 in tidal flats and salt marshes. We also carried out multiyear measurements of CO2 flux and related parameters at two field sites in Osaka Bay, Japan, having flat intertidal and salt marsh areas. The CO2 fluxes were measured using the eddy correlation and chamber methods. The air–sediment CO2 flux data from tidal flats indicated net absorption of atmospheric CO2 into the sediment during daytime hours. The air–water CO2 flux data indicated that CO2 was emitted from the water surface in small amounts, with temporal fluctuations and seasonal changes that were strongly related to salinity, as has been documented in the literature. We found that CO2 was absorbed into salt marsh and intertidal sediment and that CO2 was emitted from subtidal sediment as well as from the water surface of the tidal flat ecosystem during periods of submersion. The air–sediment CO2 flux and its temporal fluctuation at the field sites appear to be regulated by vegetation such as the reed Phragmites australis and microphytobenthos.

Carbon Storage in Tidal Flats

Tidal flat ecosystems are important habitats in shallow coastal waters. In this chapter, carbon storage in a bivalve (Corbicula japonica), phytoplankton, and sediment is estimated at two tidal flats in a eutrophic coastal area of Osaka Bay in Japan. First, we estimate the carbon storage of the bivalve from the rate of organic carbon production and shell production measured by monthly field investigations. We then estimate the carbon storage of phytoplankton based on phytoplankton biomass measurements and a model of gross primary production and respiration based on incubation experiments. To assess carbon storage in sediment, biodegradation tests of sedimentary organic carbon taken from the intertidal zone and the subtidal zone were carried out for 100 days; the residual sedimentary organic carbon is considered to represent long-term storage of carbon in sediment. Finally, the carbon storage functions of bivalves, phytoplankton, and sedimentary organic matter in tidal flat ecosystems are summarized.

Spatial distribution of hydrogen sulfide and sulfur species in coastal marine sediments Hiroshima Bay, Japan

This study aims to reveal spatial distribution of hydrogen sulfide and sulfur species in marine sediments in Hiroshima Bay, Japan, by direct analyses using a combination of detection tubes and X-ray absorption fine structure spectroscopy. In summer and autumn, the hydrogen sulfide concentration ranged from <0.1 to 4 mg-S L-1. In this study, only hydrogen sulfide was observed in autumn and at two stations in summer. In contrast, some earlier studies reported in all seasons in Hiroshima Bay the presence of acid volatile sulfide, which is used as a proxy of sulfide content. The sulfur species in sediments were mainly identified as sulfate, thiosulfate, elemental sulfur, and pyrite. Thiosulfate was a minor component compared to the other sulfur species. The formation of pyrite and sulfur derived from hydrogen sulfide oxidation played an important role in the scavenging of hydrogen sulfide.

Validity Verification of Measurement Method of Carbon Dioxide Concentration in Water using Water-resistant Breathable Tube

目の濃度が推定できるというものである.藤井ら(2011, 2012)は,pHとアルカリ度の関係から大阪湾における二 酸化炭素濃度の挙動について報告している.しかし,こ の方法は海水中のpH変化がCO2濃度のみに依存するとい うことが前提となるが,実際の環境水中ではpHの変動 要因がCO2以外にも考えられる.また,計測項目として 全炭酸やアルカリ度を選んだ場合,分析に時間や手間を 要するため水中のCO2の動態を連続的にモニタリングす ることが困難である. 直接計測法として,須藤ら(2000)や近藤ら(2003) はセンサーに光ファイバーを利用して蛍光発光物質に光 を照射し蛍光強度を計測することでCO2濃度を求める手 法を開発している.この方法は計測感度が良いのが利点 であるが,装置自体が高価であることや装置の製作には 専門知識が必要であるなどの欠点がある.一方,片山ら (1999)はセンサー部に気液平衡器を用いて気相と液相 の間に気液平衡状態を形成し,平衡状態に達したCO2を 計測する手法を開発している.津守ら(2003)はこの手 法を用いて水理実験を実施し,水中と水面上のCO2を計 測して風波による気液界面間の交換量を評価している. そこで本研究では,本手法を参考に水中のCO2濃度を 直接的かつ連続的に計測することが可能な通気性撥水チ ューブを用いた計測装置を製作し,本手法の妥当性につ いて検討するとともに本手法を用いて堆積物の有機物分 解によるCO2生成過程について検討した.

DIN Fixation by Macroalgae and Release from Sediment by the Burrowing Macrophthalmus japonicus

(1)底質の栄養塩の溶出量および同化量 調査は徳島県勝浦川河口干潟(図-1)の泥質域(約 5000m)において2007年3月から12月に行った.本調査 域はヨシ原に囲まれており,波浪は数 cm程度,潮流は 小さい地点であった.また,当調査域の底質環境につい てシルト・クレイ率は約40%,含水率は約28%,D.L.は0.90mであった.試料はコアサンプラー(Φ8cm)を用 いて深さ10cmまでの底質を採取し,実験室に持ち帰っ て底質の栄養塩の溶出量および同化量の測定を行った. 調査は現場において毎月2~3回の底質試料(n=3)を採取 し,実験に供した.実験にあたっては,底質試料の入っ たコアサンプラーの周りにアルミホイルを巻き,横から の光を遮断した後,作成したチャンバー容器にセットし た.底質が巻き上がらないように滅菌ろ過海水を注入し, 密封した.その後,恒温水槽(TAITAC製:CL-150F) にチャンバー容器を移し,実験中は底質に影響を与えな いよう撹拌を行って,現地で測定した水温に恒温水槽を 設定した.また,ハロゲンランプ(Dupla製:Electra) ヤマトオサガニの造巣活動に伴う底質から水中へのDIN回帰と 藻類による固定 DIN Fixation by Macroalgae and Release from Sediment by the Burrowing Macrophthalmus japonicus