Acute Toxicity of Nitrite to Larval Penaeus Japonicus

Abstract

To establish an empirical model of ammonia uptake by duckweed,Lemnaperpusilla under various ammonia concentrations and duckweed densities,anexperiment of a 5×5 factorial arrangement of treatments;5 initial ammonia-Nconcentrations 0.0,0.25,0.5,1.0 and 2.0 mg/l,by 5 duckweed densities 0.0,0.5,1,0,2.0,and 4.0g/l were conducted to measure the ammonia-N concentrationat 9 durations from 0 to 96 hours.In the presence of duckweed,ammonia-Ndecreased in a decaying exponential fashion;C(subscript t)=C(subscript o)×exp(－K×t)and anoptimal second order multiple regression model was obtained as the following:K=9.5242×10^(-3)+2.8252×10^(-3)×ln(C(subscript o))+3.0327×10^(-2)×D－6.1993×10^(-3)×D^(2)(R^(2)=0.7689)where C(subscript t)is the ammonia-N concentration(mg/l)at time t(hr),C(subscript o)the initialammonia concentration,K the uptake coefficient,and D the duckweed density(g/l).The model demonstrated duckweed density at 2.44 g/l was most efficientin ammonia uptake;at densities either higher or lower than 2.44 g/l the uptakecoefficient K decreased.Kincreased with initial ammonia concentration.Thechange of K was most sensitive to ln(C(subscript 0)),followed by D^(2)and D.There wasa 64 to 69% decrease in ammonia when duckweed was placed at a density 2.44g/l in solution of ammonia concentration 0.25 to 2.0 mg/l after 24 hours.為了要建立浮萍(Lemna perpusilla)在不同氨濃度及浮萍密度下對氨吸收的實驗模式，一試驗以5×5複因子處理安排；5種氨氮起始濃度0.00、0.25、0.50、1.00及2.00 mg／l及5種浮萍密度0.00、0.50、1.00、2.00及4.00 g/l，來量取從0到96小時間9個時段的氨氮濃度。當有浮萍時，氨氮呈C(下标 t)=C(下标 o)×e(上标 -Kt)的指數衰減型式。所獲得最適多元二次廻歸模式為：K=9.524×10^(-3)+2.8252×10^(-3)×ln(C(下标 o))+3.0327×10^(-2)×D－6.1993×l0^(-3)×D^(2)(R^(2)=0.7689)在此C(下标 t)為在t時（小時）氨氮濃度(mg/l)，C(下标 o)為氨氮起始濃度，K為吸收係數，D為浮萍密度(g/l)。此模式顯示浮萍密度在2.44 g/l時對氨氮吸收最有效；在密度高或低於2.44 g/l，吸收係數都降低。吸收係數隨氨氮起始濃度而增加。吸收係數對ln(C(下标 o))最敏感，而後為D^(2)及D。當氨氮濃度在0.25到2.00 mg/l，浮萍在2.44 g/l的密度下，可在24小時吸收64-69％的氨氮。