To study how global warming and eutrophication affect water ecosystems,a multiplicative growth Monod model,modified by incorporating the Arrhenius equation,was applied to Lake Taihu to quantitatively study the relationships between algal biomass and both nutrients and temperature using long-term data.To qualitatively assess which factor was a limitation of the improved model,temperature variables were calculated using annual mean air temperature (AT),water temperature (WT),and their average temperature (ST),while substrate variables were calculated using annual mean total nitrogen (TN),total phosphorus (TP),and their weighted aggregate (R),respectively.The nine fitted curves showed that TN and AT were two important factors influencing algal growth;AT limited growth as algal photosynthesis is mainly carried out near the water surface;N leakage of phytoplankton and internal phosphorus load from sediment explains why TN was the best predictor of peak biomass using the Monod model.The fitted results suggest that annual mean algal biomass increased by 0.145 times when annual mean AT increased by 1.0°C.Results also showed that the more eutrophic the lake,the greater the effect AT had on algal growth.Subsequently,the long-term joint effect of annual temperature increase and eutrophication to water ecosystems can be quantitatively assessed and predicted.
Chun YeZhemin ShenTao ZhangMaohong FanYangming LeiJianda Zhang
Activated carbon (AC) was considered to be an effective sorbent to control mercury in combustion systems. However, its capture capacity was low and it required a high carbon-to-mercury mass ratio. AC loaded with catalyst showed a high elemental mercury (Hg 0 ) capture capacity due to large surface area of AC and high oxidization ability of catalyst. In this study, several metal chlorides and metal oxides were used to promote the sorption capacity of AC. As a result, metal chlorides were better than metal oxides loaded on AC to remove gaseous mercury. X-ray diffractometer (XRD), thermogravimetric analyzer (TGA) and specific surface area by Brunauer- Emmett-Teller method (BET) analysis showed the main mechanisms: first, AC had an enormous surface area for loading enough MClx; second, Cl and MxOy were generated during pyrogenation of MClx; finally, there were lots of active elements such as Cl and MxOy which could react with elemental mercury and convert it to mercury oxide and mercury chloride. The HgO and HgCl 2 might be released from AC's porous structure by thermo regeneration. A catalytic chemisorption mechanism predominates the sorption process of elemental mercury. As Co and Mn were valence variable metal elements, their catalytic effect on Hg 0 oxidization may accelerate both oxidation and halogenation of Hg 0 . The sorbents loaded with metal chlorides possessed a synergistic function of catalytic effect of valence variable metal and chlorine oxidation.
Zhemin Shen,Jing Ma,Zhijian Mei,Jianda Zhang School of Environmental Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China
