A design study on the optimal water refreshment rate in recirculating aquaculture systems

Refreshment (make-up) water is used in recirculating aquaculture systems (RAS) mainly to purge off-flavors, to add alkalinity and sometimes for temperature control. Alternatively, alkalinity may be added by means of a chemical base and heat may be supplied by a heating system. The objective of this study is to show how the optimal (minimizing cost) mix of the three controls: water, base and heat, can be found for given temperatures and water prices.The optimal solution varies over the temperature space and also depends on the price of water. For conditions at Eilat, Israel (on the Red Sea), using supplementary heating to maintain a constant temperature may become prohibitively expensive. If heating is given up, the remaining choice is between the supply of alkalinity via the refreshment water and adding a base. The supply of alkalinity with the water requires 2.0 m³[water]/kg[feed], much more than the minimum refreshment rate required to purge off-flavors, which is thought to be 0.3 m³[water]/kg[feed]. If the price of water is more than 0.03 USD/m³, the use of sodium bicarbonate for alkalinity control is justified.     

Comparison of different soilless media for growing gerbera under alkalinity stress condition

A factorial experiment was developed with two factors of the growing medium (v/v): 100% coconut fiber (CF), 75% vermicompost+25% perlite (VP), 25% zeolite+75% perlite (ZP), 75% peat+25% perlite (PP), 75% coco chip+25% perlite (CCP), 75% coconut fiber+25% perlite (CFP) and 100% perlite (P); and sodium bicarbonate (NaHCO₃) (0, 20 and 40 mM) involving the growth of gerbera cv. Dafne. Compared with CF substrate, NaHCO₃ in the nutrient solution caused significant decrease in vegetative and reproductive traits and nutrient concentration [especially iron, phosphorus, and magnesium (Fe, P and Mg)] in the rest of the media. The improved crop performance of plants grown onto CF substrate was attributed to their strong capacity to accumulate Fe in the aerial part under alkaline conditions and to maintain a better plant nutritional status (higher P and Mg). It is concluded that the use of CF substrate could provide a useful tool to improve alkalinity tolerance of gerbera plants under NaHCO₃ stress.     

碱度对异育银鲫摄食·生长和存活的影响

[目的]探究碱度对异育银鲫摄食、生长和存活的影响,从而为开展盐碱地区异育银鲫的健康养殖提供理论指导。[方法]以摄食量、生长率和存活率为指标,研究以碱度为1.47 mmol/L的曝气自来水作对照,碱度为4、7、10、15和20 mmol/L的5种水环境对异育银鲫健康养殖的适宜性。[结果]结果表明:4 mmol/L的水环境碱度能提高异育银鲫的生长率,但差异不显著(P>0.05),水环境碱度≥7mmol/L时,异育银鲫的生长率显著下降;水环境碱度≥10 mmol/L时,异育银鲫的摄食水平显著下降(P<0.05);异育银鲫的饵料系数随碱度的升高而升高,但碱度在1.47~7 mmol/L范围内饵料系数差异不显著(P>0.05);1.47~10 mmol/L的水环境碱度对异育银鲫的存活率无显著影响(P>0.05),当碱度≥15 mmol/L时异育银鲫的存活率显著下降(P<0.05)。[结论]4 mmol/L左右的水环境碱度适宜异育银鲫的健康养殖,而10 mmol/L以上的水环境碱度不利于异育银鲫的健康养殖。     

Impact of Varying Ca/Mg Waters on Ionic Balance,Dispersion, and Clay Flocculation of Salt-Affected Soils

Inceptisols and Vertisols are two dominant soil orders that support major agricultural production in India. These soils often exist in semi-arid and arid regions. Low precipitation and high evaporation demand leads to salt accumulation in these areas. The problem of salt accumulation is further compounded by the presence of saline/alkaline groundwaters. We evaluated the effect of modified Ca/Mg waters on ionic composition, dispersion, and clay flocculation of sodic Inceptisols, saline-sodic Inceptisols, and normal Vertisols from different parts of India. A completely randomized factorial design with three replications of individual soils were sequentially leached with five pore volumes of deionized, saline water of 60 and 120 me L^?1 total electrolyte concentration (TEC) at a fixed SAR of 5.0 mmol^1/2 L^?1/2 and Ca:Mg ratio of 2:1, 1:1 and 1:2. Application of saline waters decreased pH and increased EC of the soil leachates after leaching five pore volumes of three Ca/Mg ratios of 60 and 120 me L^?1 solutions in sodic Inceptisols and normal Vertisols. In saline-sodic Inceptisols, application of saline waters decreased both pH and electrical conductivity (EC) of the soil leachates. Preferential Ca²⁺ holding in soil was only noticed in sodic Inceptisols when leaching process was performed with independent saline waters, but Mg²⁺ has a tendency to hold in soil upon application of independent saline waters for all soils except sodic Inceptisols. Periodic application of deionized water could increase soil dispersion and decreased flocculation of clay particles. Mg²⁺ ion had less flocculating vis-à-vis high-dispersion effect on soil clays than the Ca²⁺ ion.     

逆境下广布野豌豆的适宜收获时间

及时收获对于获得最大的种子活力和种子产量是很重要的,许多牧草都具有种子脱落及其他种子生产的问题。裂荚是广布野豌豆种子生产中的一个重要问题。本文的研究目的是通过分析种子和荚果的生理学特征、种子的抗逆能力来进一步确定广布野豌豆(Vicia cracca)的收获时间。在广布野豌豆荚果发育过程中,每隔3 d收获1次荚果,到荚果开始出现开裂为止(盛花后第42 d)。结果显示,盛花后36~42 d,荚果干重、千粒重达到最大及荚果含水量达到最小,在此期间NaCl和Na₂CO₃胁迫下的种子发芽率、发芽速率及胚根长均达到最大值。因此,广布野豌豆在裂荚前6 d收获不影响种子产量和品质。     

烟草中水溶性灰分碱度的近红外分析

[目的]应用偏最小二乘法建立烟草水溶性灰分碱度的近红外分析模型。[方法]采集标样的傅里叶变换近红外漫反射光谱数据并利用化学计量学的方法对所得到的近红外光谱数据与灰分碱度的基础数据进行建模,优化建立后的模型,并对该模型进行验证。[结论]经模型优化后最终的相关系数为0.978 0,均方估计残差为0.040 0,预测标准差为0.245,交互验证均方差为0.089 3,模型优化指数为74.1,主因子为11。用57个验证样品对模型进行检验,结果显示：平均误差为0.193 4,预测范围为0.15～3.94。[结论]该方法具有较好的可行性。     

沈阳地区盐渍土的生态分布、特性及改良利用

在土壤调查的基础上，对沈阳市盐渍土的生态分布、剖面特性进行了分析；通过近十年对盐渍土中低产田改良利用的试验示范成果，提出了磷石膏、沸石等改良盐渍土的作用和效果，认为水利、生态和化学等综合配套技术应用是改良沈阳市　盐渍土的有效途径．     

盐度与碱度对花鲈幼鱼的毒性研究

试验研究盐度与碱度对花鲈(Lateolabraxjaponicus)幼鱼的急性毒性结果表明,24h、48h、72h、96h碱度对花鲈幼鱼的半致死浓度(LC50)分别为101.05mmol/L、63.27mmol/L、56.85mmol/L和46.18mmol/L;盐度和碱度联合毒性试验结果显示碱度对花鲈幼鱼24h半致死浓度与盐度显著相关,二者间关系为ALK=125.05-2.18S(n=7,r=0.9756),表明盐度和碱度之间可能存在一定的交互作用。     

盐度、碱度对中国林蛙蝌蚪及变态幼蛙的毒性影响

在水温16—18℃的野外条件下,采用单因子静态急性毒性实验法,研究水环境中盐度、碱度对中国林蛙(Rana chensinensis)蝌蚪及变态幼蛙的毒性效应。在pH为7．0～8．5、总碱度为1．41mol/L时,盐度对中国林蛙蝌蚪及变态幼蛙的24、48、72、96h半致死值(LC50)分别为8．21、7．25、5．17和3．70g/L及8．84、7．17、6．62、6．29g/L;零致死值(LC0)分别为7．14、6．00、2．67、2．20g/L及6．34、6．16、5．78、5．45g/L;全致死值(LC100)分别为9．98、9．00、7．67、5．20g/L及11．34、9．67、7．45、5．45g/L;安全值(SC)为1．70g/L和1．42g/L。在相同pH下,盐度为0．18g/L时,碱度对中国林蛙蝌蚪及变态幼蛙的24、48、72、96h LC50值分别为14．36、11．83、10．35和7．68mmol／L及15．07、13．72、11．23、8．65mmol/L;LC0值分别为8．76、8．51、4．65、3．88mmol/L及9．11、7．03、6．85、5．17mmol/L;LC100值分别为19．96、15．14、16．05、11．48mmol/L及21．02、20．41、15．60、12．02m/mol/L;SC值为2．41mmol/L和3．41mmol/L。综合我国淡水养殖水质标准,建议养殖中国林蛙蝌蚪及变态幼蛙长期生存的盐度上限分别为2．0g/L和1．5g/L,碱度上限分别为2．5mmol/L和3．5mmol/L。     

南美白对虾对内陆碳酸盐型盐碱水环境的适应性研究*I.淡化幼虾对碱度的适应能力

为探讨东北松嫩平原碳酸盐型盐碱水域移植南美白对虾的可行性，以天然盐碱泡水为实验用水，采用急性毒性实验法，研究了淡化幼虾对碱度的适应能力：结果表明，在水温(23．44-1．3)℃、pH8．03～8．37、盐度3．63～4．60的条件下，碱度对淡化幼虾毒性作用的24，48和96hLC，。分别为12．92，11．16和10．67mmol／L，SC为2．50mmol／L：认为南美白对虾淡化幼虾对碱度的适应能力不如鲢、鳙、草鱼等淡水鱼类，可以养殖鲢、鳙的盐碱水域不一定也适宜幼虾生存，而且碱度并不是唯一的限制因子。