The metal — Metal interactions in biological systems Part III. Daphnia magna     

Piotr Tomasik  Christopher H. D. Magadza  Sungano Mhizha  Alfred Chirume 《Water, air, and soil pollution》1995,82(3-4):695-711

The toxicity of single metal ions: Al, Co(II), Cr(III), Cu(II), Fe(III), Mg, Mn(II), Mo(VI), Ni(II), Se(VI), V(V) and Zn and the following pairs of them: Al-Co, Al-Mg, Al-Mo, Al-Se, Al-Zn, Cr-Co, Cr-Mg, Cr-Mo, Cr-Se, Cr-Zn, Cu-Co, Cu-Mg, Cu-Mo, Cu-Se, Cu-Zn, Fe-Co, Fe-Mg, Fe-Mo, Fe-Se, Fe-Zn, Mn-Co, Mn-Mg, Mn-Mo, Mn-Se, Mn-Zn, Ni-Co, Ni-Mg, Ni-Mo, Ni-Se, Ni-Zn, V-Co, V-Mg, V-Mo, V-Se, V-Zn, Zn-Co, Zn-Mg, Zn-Mo, and Zn-Se on Daphnia magna was examined. The most prominent antagonism in the toxicity was observed in the following ion pairs: Al-Mo(VI), Cr(III)-Co(II), Cr(III)-Mg, Cr(III)-Mo(VI), Cr(III)-Se(VI), Cr(III)-Zn, Fe(III)-Se(VI), Mn(II)-Mg, Mn(II-Se(VI), Zn-Mg and Zn-Mo(VI). The strong synergism was found for the following ion systems: Cr(III)-Se(VI), Cr(III)-Zn, Fe(III)-Se(VI), Mn(II)-Zn, Mn(II)-Se(VI), Ni(II)-Co(II), Ni(II)-Mo(VI), Ni(II)-Se(VI), Ni(II)-Zn, V(V)-Co(II), V(V)-Mo(VI), V(V)- Se(VI), and V(V)-Zn. Synergism and antagonism in toxicity were dependent on water hardness as well as on the ion concentration. Adaptive procesess of the animals to the toxic environment could also be observed. Thus, the toxicity of the single ions and their pairs was not linear with respect to time.  相似文献   

Modeling the potential for closing quinoa yield gaps under varying water availability in the Bolivian Altiplano   总被引：1，自引：0，他引：1  

S. Geerts  D. Raes  M. Garcia  C. Taboada  R. Miranda  J. Cusicanqui  T. Mhizha  J. Vacher 《Agricultural Water Management》2009,96(11):1652-1658

In the Bolivian Altiplano, the yields of rainfed quinoa are relatively low and highly unstable. We use a validated crop water productivity model to examine the potential of closing quinoa yield gaps in this region. We simulate the expectable yields under rainfed cultivation and under different deficit irrigation (DI) strategies using the AquaCrop model for the Northern, Central and Southern Bolivian Altiplano. Simulated DI scenarios include a reference strategy avoiding stomatal closure during all sensitive growth stages and allowing drought stress during the tolerant growth stages (DI₀) and various restrictive deficit irrigation strategies (DI_i) representing cases when water resources are limited. We obtain a logistic crop water production function for quinoa by plotting the seasonal actual evapotranspiration versus total grain yield. Due to the large scatter, this function only indicatively provides expectable yields. From the scenario analysis, we derive yield probability curves for the 3 agro-climatic regions. DI, without restriction in irrigation water during the drought sensitive growth stages, is able to close the yield gaps in the Northern, Central and Southern Bolivian Altiplano, and would guarantee a high and stable level of water productivity (WP). The yields of quinoa under rainfed cultivation during dry years are only 1.1, 0.5 and 0.2 Mg ha⁻¹ in the Northern, Central and Southern Bolivian Altiplano, whereas under DI₀ they are 2.2, 1.6 and 1.5 Mg ha⁻¹, respectively. Under limited water availability for irrigation, these stable yield levels decrease, most drastically in the Southern Bolivian Altiplano. Below a minimum water availability of 600 m³ per ha and 700 m³ per ha in the Central and Southern Bolivian Altiplano, respectively, the application of DI for quinoa is not significantly effective and should be avoided to save valuable resources. The yield probability curves we derive can serve as input for stochastic economic analysis of DI of quinoa in the Bolivian Altiplano.  相似文献   

Metal-metal interactions in biological systems. Part IV. Freshwater snail Bulinus globosus     

Piotr Tomasik  Christopher M. Magadza  Sungano Mhizha  Alfred Chirume  Mark. F. Zaranyika  Satchmore Muchiriri 《Water, air, and soil pollution》1995,83(1-2):123-145

The toxicity against title snails of all Al, Cd, Co(II), Cr(III), Cu(II), Fe (III), Mg, Mn(II), Mo(VI), Ni(II), Pb(II), Se(VI), V(V) and Zn ions was checked in 96 h tests in the water of Kariba Lake. Based on the mortality — concentration relationship the toxicity order of the above ions against Bulinus globosus is Cu(II) > Ni(II) > Cd > Pb(II) > Zn > Al > V(V)> Cr(III)> Se(VI) > Fe(III) =Co(II)> Mn(II) > Mg > Mo(VI). Only Mg, Pb(II), Cu(II), Cd, Zn and Ni(II) ions are harmful to these snails as their mortality is observed at the naturally occuring concentrations. Other metal ions cause lethality at naturally unrealistic concentrations. The following pairs of metal ions were also checked for mutual interactions: Cd-Al, Cd-Co, Cd-Cr, Cd-Cu, Cd-Fe, Cd-Mg, Cd-Mn, Cd-Mo, Cd-Ni, Cd-Pb, Cd-Se, Cd-V, Cd-Zn, Cu-Al, Cu-Co, Cu-Cr, Cu-Fe, Cu-Mg, Cu-Mn, Cu-Mo, Cu-Ni, Cu-Pb, Cu-Se, Cu-V, Cu-Zn, Ni-Al, Ni-Co, Ni-Cr, Ni-Fe, Ni-Mg, Ni-Mn, Ni-Mo, Ni-Pb, Ni-Se, Ni-V, Ni-Zn, Pb-Al, Pb-Co, Pb-Cr, Pb-Fe, Pb-Mg, Pb-Mn, Pb-Mo, Pb-Se, Pb-V, Pb-Zn, Zn-Al, Zn-Co, Zn-Cr, Zn-Fe, Zn-Mg, Zn-Mn, Zn-Mo, Zn-Se, Zn-V. Synergism and antagonism were several times observed in various combinations of ions. The effect of metal-metal interactions on an accumulation of those metals in the flesh and shells of snails was also observed and measured.  相似文献   

Using seasonal climate forecasts to improve maize production decision support in Zimbabwe   总被引：1，自引：0，他引：1  

N. ZinyengereT. Mhizha  E. MashonjowaB. Chipindu  S. GeertsD. Raes 《Agricultural and Forest Meteorology》2011,151(12):1792-1799

Maize production in marginal tropical regions is at great risk due to rainfall variability and climate change. Climate change is set to increase the variability and uncertainty of inter-annual rainfall. Farmers who depend on rainfed maize production for their livelihoods would therefore benefit from improved climate based forecasting of production likelihood. In this study we developed a simple maize production decision support tool for Masvingo by using seasonal climate forecasts and a crop model to forecast maize yields likelihood prior to the season. We follow up on earlier studies carried out in Zimbabwe which show that the El Nino Southern Oscillation (ENSO) can be used to forecast rainfall and maize yields in Zimbabwe. An ENSO based seasonal climate analysis tool (RAINMAN) was used to produce probabilistic monthly climate forecasts for Masvingo corresponding to the phases of the Southern Oscillation Index (SOI). The climate forecasts were used to run a crop model (AquaCrop) for a variety of scenarios relevant to maize production (monthly rainfall, cultivar selection, planting date, and fertility level). The results of the simulations were similar to those observed by Phillips et al. (1997) and formed the basis for the development of an operational decision support tool. Simulated maize yields varied from 1.2 t/ha to 5.8 t/ha. The simulated yields were higher than expected average yields in a marginal region like Masvingo especially under small holder farming. The work suggested that optimal use of forecasts may lead to improved maize production in Masvingo. The study set a platform for the development of operational climate based maize production decision support tools in Zimbabwe.  相似文献