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Abstrak :
The analysis of daily curves of dissolved oxygen in the Garonne, downstream of Toulouse, shows that the river is generally heterotrophic. It appears in contradiction with the fact that the river bed is covered with a thick periphytic biofilm. From the data obtained in-vitro and in-situ, we developed a model to calculate the net production, integrated over the section. This model makes it possible to simulate various environmental situations: variations of the wet cross section, seasons and turbidity. The simulations show that some zones of the section are highly productive. For the majority of the cases, the daily balance photosynthesis/respiration remains less than one. This negative daily balance is equilibrated by the re-aeration rate associated with the turbulent flow of the Garonne. This work shows, however, that the oxygen level in the river is strongly dependent on the total rate of respiration, so that a weak increase (pollution for example) could quickly induce a reduction in the dissolved oxygen

Abstrak :
The development of methods in measuring the photosynthesis process is now increasingly widespread, especially to get a more efficient method and fast. Photosynthesis efficiency of micro-algae periphytic has been estimated under the influence of light intensity and temperature by using the fluorescence monitoring system. the measurement on a colonized substrate by the saturation pulse method has been conducted using a FMSI(Fluorescence Monitoring Systems,Hansatech). Measurement of the fluorescence parameters was conducted every week on algal periphyton which was cultivated on the articial substrate during for 5 weeks under light and temperature conditions. The results show that fluorecence maximal value (Fm) increase linearly with chlorophyll a concentrations. For 20 derajat C (experiment where the biomass reached higher values),up to 100 mg chlorophyll a.m min 2 the change in Fm is approximately linear. After,the response of Fm is hyperbolic, sugesstting a measure in vivo chlorophyll a flurescence of periphyton in laboratory conditions. The instrument is simple to use, with convenient software control, especially when used in PC mode.

Abstrak :
The experiment aimed to examine the growth and some physiological parameters of five metal-accumulator weed species in response to mercury (Hg) and lead (Pb) treatment. Five weed species (Branchiaria mutica, Cyperus kyllingia, Ipomea aquatica, Mikania micrantha, and Paspalum conjugatum) were grown in water culture using half strength Hoagland’s solution and subjected to Hg(NO3)2 and PB(NO3)2 at 0,  0.25 and 0.5 mM for 3 weeks. The growth, photosynthesis, lipid peroxidation and proline content were observed during the treatments. The result showed that both Hg and Pb decreased growth significantly, but the decrease was far higher in Hg than in Pb treatments. Hg treatment reduced photosynthetic rate dramatically under different photosynthetic photon flux density suggesting that heavy metal Hg until 0.5 mM caused the damage of photosynthetic apparatus almost all species except in I. aquatica. Hg and Pb treatment caused dramatic increase in leaf MDA content, which was associated with the decrease of chlorophyll content significantly. Almost all the species were tolerant to Pb treatment up to 0.5 mM except M. micrantha, while only C. kyllingia and I. aquatica were tolerant to Hg treatment up to 0.5 mM. Only Hg treatment and not Pb that induced higher proline content in the leaves of threated plants without clear pattern of the increment among the species suggesting that proline may have a role as alarm stress rather than tolerant indicator.

Abstrak :
ABSTRAK
Kami tengah mengembangkan sistem artifisial fotosintesis berdasarkan sel tandem fotoelektrokimia, baik untuk fiksasi nitrogen atau karbon dioksida menjadi zat kimia bernilai guna. Sel tandem ini terdiri dari DyeSensitized Solar Cell (DSSC), yang digunakan sebagai penyedia potensial eksternal, dan sel PEC (photoelectrochemical) sebagai zona katalisis. PEC pada zona katalisis menggunakan pasangan katoda untuk reaksi reduksi pada kondisi gelap dan fotoanoda untuk reaksi oksidasi air dibawah penyinaran sinar tampak untuk membentuk oksigen dan proton. Bagian penting dalam mengembangkan sistem ini adalah pemilihan material yang tepat. Diperlukan material yang dapat mengadsorb nitrogen dan/atau karbon dioksida secara baik pada sisi katoda gelap, sementara pada fotoanoda diperlukan material yang dapat menyerap cahaya tampak dan memiliki sifat intrinsik yang baik untuk oksidasi air. Saat ini kami mengembangkan material bTiO2 dan b-TiO2 termodifikasi pada katoda dan anoda. Untuk DSSC, dikembangkan DSSC berbasis TiO2 nanotube/N719 dengan menambahkan CdS sebagai ko-sensitizer. Sintesis b-TiO2 dilakukan dengan reduksi elektrokimia TiO2 nanotube dalam larutan aqueous, sedangkan TiO2 nanotube dipreparasi dengan teknik elektro-oksidasi. Material kemudian dikarakterisasi dengan XRD, SEM, FTIR, UV-VIS DRS, dan potensiostat. Hasil penelitian menunjukan warna TiO2 berubah dari abu-abu menjadi biru setelah proses reduksi elektrokimia. Pada waktu optimum reduksi, terjadi peningkatan kondiktivitas dan pergeseran band gap dari 3,2 menjadi 2,9 eV. Sebagai fotoanoda, b-TiO2 dimodifikasi dengan spesies kobalt oksida (Co3O4) untuk meningkatkan respon photocurrent pada daerah sinar tampak dan mengkatalisis reaksi fotooksidasi air. Performa material TiO2/Co3O4 sebagai fotoanoda diuji dengan fenomena evolusi oksigen dan kemampuannya untuk mendegradasi zat warna dari air ketika dipaparkan sinar tampak. DSSC yang difabrikasi dengan sistem TiO2/CdS/ZnS/N719 memberikan efisiensi sebesar 1,29% dan fill factor 0,43, 14% lebih baik dari sel surya TiO2/N719. Sistem artifisial fotosintesis yang terusun dari TiO2/CdS/ZnS/N719 sebagai DSSC, b-TiO2 pada katoda, dan and b-TiO2/Co3O4 sebagai fotoanoda memberikan efisiensi Solar to Chemical sebesar 0.05% untuk konversi N2 menjadi NH3, hasil ini 2,5 kali lebih besar dari sistem Hirakawa et al. (2017). Ketika digunakan untuk mereduksi CO2, sistem menghasilkan Metanol dan asam format. Sistem ini juga dapat melangsungkan fiksasi N2 dan CO2 secara simultan untuk menghasilkan fine chemicals seperti amonia, metanol, dan asam format.

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ABSTRACT
We have been developing an artificial photosynthesis device, based on tandem of dual photo-electrochemical cells, either for nitrogen or carbon dioxide fixation into fine chemicals. The tandem cell is comprised of a dye sensitized solar cell (DSSC), as embedded an external potential, and a photo-electrochemical (PEC) cell as catalysis zone. The PEC in catalysis zone employing couple of cathode and photoanode, whereas the cathode is dedicated for a reduction reaction site under the dark, while the photo-anode is dedicated for an oxidation reaction under visible light to produce oxygen and proton. A crucial part of such system is including proper choice of electrodes materials. An electrode material that can absorb nitrogen and/or carbon dioxide gases is necessary for the dark cathode, while a photo electrode material that can absorb visible light and having intrinsic oxidation potential to split water is necessary. Currently, we are developing the b-TiO2 and modified the bTiO2 for both those electrodes material. For DSSC, we fabricate nanotube TiO2/N719 photoanode with CdS as co-sensitizer. The b-TiO2 was synthesized by electrochemical reduction of TiO2 nanotube in aqueous solution, while the TiO2 nanotubes was prepared by electro-oxidation technique. The materials were characterized by XRD, SEM, FTIR, UV-VIS DRS, and Electrochemical work station. The results indicate that by reducing TiO2 electrochemically, the color of TiO2 change from grey to blue. At the optimum reduction time the band gap shifts from 3.2 eV to 2.9 eV, and the conductivity increase. For a photo-anode, the b-TiO2 was then modified by Cobalt oxide (Co3O4) to increase photocurrent response at visible region, and to enhance photo-oxidation reaction. The performance of bTiO2/Co3O4 as photo-anode was examined by oxygen evolution event and its ability to remove dyes from water, when it was exposed by visible light. The DSSC fabricated by TiO2/CdS/ZnS/N719 system gives 1.29% efficiency and fill factor 0.43, which is 14% higher than TiO2/N719. In addition, the performance of the tandem DSSC-PEC system was examined by the ability of the cell to convert nitrogen to ammonia and carbon dioxide to fine chemicals. The results show that system comprised by TiO2/CdS/ZnS/N719 DSSC, b-TiO2 at cathode, and bTiO2/Co3O4 as photoanode give 0.05% Solar to Chemical efficiency when used to convert N2 to NH3 which is 2.5 higher than Hirakawa (2017) device. When used to convert CO2 the device produces Metanol and formic acid. The device can also be used to convert N2 and CO2 simultanously to produce fine chemicals such as ammonia, methanol, and formic acid.