The variation of phosphorus （P） bioavailability in terms of water soluble P （WSP ）, readily desorbable P （RDP）, algal available P （AAP）, and NaHCo3 extracting P （Olsen-P） in the re-suspended sediments was in...The variation of phosphorus （P） bioavailability in terms of water soluble P （WSP ）, readily desorbable P （RDP）, algal available P （AAP）, and NaHCo3 extracting P （Olsen-P） in the re-suspended sediments was investigated in laboratory experiments, in which the waters and sediments were taken from campus canal. The results indicate that sediment re-suspension can promote the migration, of soluble reactive P （SRP） from overlying water to sediments. The contents of AAP and Olsen-P in re-suspended sediments reduced obviously, whereas the values of the sediments in the control increased slightly, compared with the initial state, indicating that the P bioavailability in the sediments could be rcduced evidently due to sediment re-suspension. The content and characteristics of iron-bound P （BD-P） significantly affect the formation of AAP. The formation of OlservP has close relationship with the contents of BD-P, almninium-botmd P （AI-P）, and organic P （NaOH-nrP）.展开更多
Retention efficiencies (RE) of scallop (Chlamys farreri),oyster (Crassostrea gigas) and mussel (Mytilus edulis) in a flow-through system were measured to understand the short-term response to various particle and orga...Retention efficiencies (RE) of scallop (Chlamys farreri),oyster (Crassostrea gigas) and mussel (Mytilus edulis) in a flow-through system were measured to understand the short-term response to various particle and organic matter concentrations.By comparing the RE of C.farreri with that of C.gigas and M.edulis,we gained further knowledge on the feeding physiological characteristics of C.farreri and ascertained the possible cause of high summer mortalities of this species.The experimental feeding conditions included natural differences in the abundance and composition of suspended seston,as well as conditions in which seston abundance and composition were manipulated by adding natural silt or cultured microalgae.The results show that in natural sea water,the minimum particle size for maximal retention in M.edulis,C.gigas and C.farreri was approximately 4,6,and 8 μm,respectively;the RE of 2-μm (equivalent spherical diameter) particles was 17%,19%,and 8%,respectively;and the relative standardized RE was 58%,49%,and 18%,respectively.In C.gigas and M.edulis,the minimal particle size for maximal retention did not change with food quality (organic content).C.farreri was more sensitive to fluctuations in particle concentration and organic content.With particle concentration increase,the minimal particle size for maximal retention in scallop shifted to large particles and the RE for 2-μm particle decreased from 8% in natural seawater to 1.6%-6% in silt-enriched groups.With organic content increase,the minimal particle size for maximal retention shifted from 8 to 5 μm in natural seawater.Variation in RE of C.farreri with food conditions and the relationship between lower RE and smaller particle size may hamper C.farreri from food taking due to the decrease in the size distribution of phytoplankton in Sungo Bay.展开更多
This study aimed to explore the effect of 5% tembotrione oil dispersion(OD)-38% atrazine suspension concentrate(SC) tank mixture on the weeds in spring maize fields and the safety of the mixture. To be specific, rando...This study aimed to explore the effect of 5% tembotrione oil dispersion(OD)-38% atrazine suspension concentrate(SC) tank mixture on the weeds in spring maize fields and the safety of the mixture. To be specific, randomized block design was adopted for the field experiments. The results showed that the application of tankmixture of 5% tembotrione OD at 90 g a.i./hm^(2)and 38% atrazine SC at 570 g a.i./hm^(2)and the mixture of 5% tembotrione OD at 90 g a.i./hm^(2)and 38% atrazine SC at 1140 g a.i./hm^(2)respectively controlled 94.7%~96.3% and 94.0%~96.3% of the grass weeds, 94.7%~96.0% and 93.7%~95.7% fresh weight of grass weeds, 95.3%~96.3%and 93.3%~97.3% of broadleaf weeds, and 94.7%~96.0% and 93.3%~96.3% fresh weight of broadleaf weeds. The efficacy was better than that of the 5% tembotrione alone and the control herbicide and no phytotoxicity of the mixtures was identified.The tank mixture of tembotrione and atrazine should be promoted in the spring maize field for weed control and the recommended dosages were 90 g a.i./hm^(2)for 5%tembotrione and 570 g a.i./hm^(2)for 38% atrazine.展开更多
基金National High Technology Research and Development Program(863) of China(No.2003AA601070)National Natural Science Foundation of China(No.50908154)
文摘The variation of phosphorus （P） bioavailability in terms of water soluble P （WSP ）, readily desorbable P （RDP）, algal available P （AAP）, and NaHCo3 extracting P （Olsen-P） in the re-suspended sediments was investigated in laboratory experiments, in which the waters and sediments were taken from campus canal. The results indicate that sediment re-suspension can promote the migration, of soluble reactive P （SRP） from overlying water to sediments. The contents of AAP and Olsen-P in re-suspended sediments reduced obviously, whereas the values of the sediments in the control increased slightly, compared with the initial state, indicating that the P bioavailability in the sediments could be rcduced evidently due to sediment re-suspension. The content and characteristics of iron-bound P （BD-P） significantly affect the formation of AAP. The formation of OlservP has close relationship with the contents of BD-P, almninium-botmd P （AI-P）, and organic P （NaOH-nrP）.
基金Supported by the National Natural Science Foundation of China (No. 40676093)European Community INCO-DC Project ERBIC18CT980291+2 种基金National Basic Research Program of China (973 Program) (2006CB400608)National High Technology Research and Development Program of China (863 Program) (No. 2006AA100307)National High Technology Research and Development Program of China (863 Program)(No.2006BAD09A09)
文摘Retention efficiencies (RE) of scallop (Chlamys farreri),oyster (Crassostrea gigas) and mussel (Mytilus edulis) in a flow-through system were measured to understand the short-term response to various particle and organic matter concentrations.By comparing the RE of C.farreri with that of C.gigas and M.edulis,we gained further knowledge on the feeding physiological characteristics of C.farreri and ascertained the possible cause of high summer mortalities of this species.The experimental feeding conditions included natural differences in the abundance and composition of suspended seston,as well as conditions in which seston abundance and composition were manipulated by adding natural silt or cultured microalgae.The results show that in natural sea water,the minimum particle size for maximal retention in M.edulis,C.gigas and C.farreri was approximately 4,6,and 8 μm,respectively;the RE of 2-μm (equivalent spherical diameter) particles was 17%,19%,and 8%,respectively;and the relative standardized RE was 58%,49%,and 18%,respectively.In C.gigas and M.edulis,the minimal particle size for maximal retention did not change with food quality (organic content).C.farreri was more sensitive to fluctuations in particle concentration and organic content.With particle concentration increase,the minimal particle size for maximal retention in scallop shifted to large particles and the RE for 2-μm particle decreased from 8% in natural seawater to 1.6%-6% in silt-enriched groups.With organic content increase,the minimal particle size for maximal retention shifted from 8 to 5 μm in natural seawater.Variation in RE of C.farreri with food conditions and the relationship between lower RE and smaller particle size may hamper C.farreri from food taking due to the decrease in the size distribution of phytoplankton in Sungo Bay.
文摘This study aimed to explore the effect of 5% tembotrione oil dispersion(OD)-38% atrazine suspension concentrate(SC) tank mixture on the weeds in spring maize fields and the safety of the mixture. To be specific, randomized block design was adopted for the field experiments. The results showed that the application of tankmixture of 5% tembotrione OD at 90 g a.i./hm^(2)and 38% atrazine SC at 570 g a.i./hm^(2)and the mixture of 5% tembotrione OD at 90 g a.i./hm^(2)and 38% atrazine SC at 1140 g a.i./hm^(2)respectively controlled 94.7%~96.3% and 94.0%~96.3% of the grass weeds, 94.7%~96.0% and 93.7%~95.7% fresh weight of grass weeds, 95.3%~96.3%and 93.3%~97.3% of broadleaf weeds, and 94.7%~96.0% and 93.3%~96.3% fresh weight of broadleaf weeds. The efficacy was better than that of the 5% tembotrione alone and the control herbicide and no phytotoxicity of the mixtures was identified.The tank mixture of tembotrione and atrazine should be promoted in the spring maize field for weed control and the recommended dosages were 90 g a.i./hm^(2)for 5%tembotrione and 570 g a.i./hm^(2)for 38% atrazine.
