Modern sedimentation rates in the intertidal zone on the west coast of the Bohai Gulf

On the basis of the measurement of 210Pbex and 137Cs activities in the sediment cores taken from the intertidal zone on the west coast of the Bohai Gulf, the average sedimentation rates of modern sediments are calculated. The results indicate that in the sandy area of the intertidal zone (from Daogouzi to the Duliujian River), the sedimentation rate from 1955 to 1963 is 3.43-4.06 cm/a, and is within the range of 0.65￣1.59 cm/a since 1963. The average sedimentation rate in the muddy area (around Qikou) is approximately 1.81 cm/a. The results above suggest that the sandy area of the intertidal zone has experienced rapid sedimentation from the 1950s to the 1960s, and the sedimentation slows down after the 1960s, and the sedimentation rates increase from north to south spatially. The rapid sedi- mentation from the 1950s to the 1960s in the sandy area is due to the fact that North China has plentiful precipitation during this period and the intertidal zone is supplied with abundant matter sources for sedimentation. After the 1960s, the weakened sedimentation may be a result of the reduction of sand transported to the intertidal zone, which is a consequence of diminished rainfall in North China and intensive human activities in the Haihe basin.

Structural and photocatalytic properties of TiO_2 films fabricated on silicon substrates by MOCVD method

Silicon(111) and Silicon(100) were employed for fabrication of TiO 2 films by metal organic chemical vapor deposition(MOCVD). Titanium(IV) isopropoxide(Ti[O(C 3H 7) 4]) was used as a precursor. The as deposited TiO 2 films were characterized with FE\|SEM, XRD and AFM. The photocatalytic properties were investigated by decomposition of aqueous OrangeⅡ. And UV VIS photospectrometer was used for checking the absorption characteristics and photocatalytic degradation activity. The crystalline and structural properties of TiO 2 film had crucial influences on the photodegradation efficiency. For MOCVD in situ deposited films on Si substrates, the photoactivities varied following a shape of “M': at lower(350℃), middle(500℃) and higher(800℃) temperature of deposition, relative lower photodegradation activities were observed. At 400℃ and 700℃ of deposition, relative higher efficiencies of degradation were obtained, because one predominant crystallite orientation could be obtained as deposition at the temperature of two levels, especially a single anatase crystalline TiO 2 film could be obtained at 700℃.

Fabrication and Photocatalytic Characteristics of TiO_2 Films on Silicon Substrates

Silicon (111) and Silicon (100) have been employed for fabrication of TiO_2films by metal organic chemical vapor deposition (MOCVD). Titanium (IV) isopropoxide (Ti[O(C_3H_7)_4]) was used as a precursor. The as-deposited TiO_2 films have been characterized withField emission scanning electron microscopy (FE-SEM), X ray diffraction (XRD) and atomic forcemicroscopy (AFM). The photocatalytic properties were investigated by decomposition of aqueous orangeII. The crystalline and structural propertiesof TiO_2 film had crucial influences on thephotodegradation efficiency. For MOCVD in-situ deposited films on Si substrates, the photoactivitiesvaried following a shape of 'M': At lower (350 °C ) middle (500 °C) and higher (800 °C)temperature of deposition, relative lower photodegradation activities have been observed. At 400 °Cand 700 'C of deposition, relative higher efficiencies of degradation have been obtained, becauseone predominant crystallite orientation could be obtained as deposition at those two temperatures,especially a single anatase crystalline TiO_2 film could be obtained at 700 °C growth.