Inhibition of nitrification in soil by metal diethyldithiocarbamates

IntroductionNitrificationisaprocessinwhichammoniumformofnitrogenisconvertedintonitrateform .Nitrogenuseefficiencyintermsofplantuptakeisgenerallylowandvariesgreatlyunderdifferentsoilandcroppingconditions.MostfertilizerNappliedtosoilsisintheformofammonium orammoniumproducingcompoundssuchasurea,andisusuallyoxidizedrapidlytonitratebynitrifyingmicroorganismsinsoils.Applicationofnitrogenfertilizersmorethanoptimumlevelsleadstolownitrogenrecoveriesandgreaternitrogenaccumulationinthesoilprofile .Theac…     

Short communication kazal type trypsin inhibitor in amniotic fluid in fetal developmental disorders

The amniotic fluid concentrations of the Kazal type trypsin inhibitor were studied in pregnancies with fetal developmental disorders. The samples were obtained by amniocentesis between 14 and 19 weeks of gestation. In cases with fetal malformations, the level was below the normal 10th centile in 15 out of 28 cases (54 per cent, P<0.05) and above the normal 90th centile in 2 cases (7.1 per cent). Low values were common in cases with intrauterine fetal death or congenital nephrosis. The levels were normal in fetal chromosomal aberrations.     

蛋白酶抑制剂对杨扇舟蛾的中肠蛋白酶作用的研究

研究了杨扇舟蛾幼虫的中肠几种主要蛋白酶活性．以14C-酪蛋白为底物测定的总消化酶活性在碱性缓冲液中最高；特异蛋白酶抑制剂研究表明：只有丝氨酸蛋白酶抑制剂对中肠蛋白酶活性有抑制作用，其它的特异蛋白酶抑制剂如半光氨酸蛋白酶抑制剂、天门冬氨酸蛋白酶抑制剂和金属蛋白酶抑制剂对中肠的酶活均无抑制作用，可以认为杨扇舟蛾的中肠蛋白酶以丝氨酸蛋白酶为主．以特异的p－nitroanilide为底物测定胰蛋白酶、胰凝乳蛋白酶、弹性蛋白酶和亮氨酸蛋白酶活性在碱性缓冲液中最高，且以弹性蛋白酶活性最高．在所研究的23个丝氨酸蛋白酶抑制剂中，抑制作用最强的是马铃薯蛋白酶抑制剂I和南瓜韧皮胰蛋白酶抑制剂．本研究丰富了对杨扇舟蛾的中肠蛋白酶种类的了解，为杨树抗虫基因构建和转化提供了依据．     

Emission of nitrous oxide from rice-wheat systems of Indo-Gangetic plains of India

Nitrous oxide (N₂O) accounts for 5%of the total enhanced greenhouse effect and responsiblefor the destruction of the stratospheric ozone. The rice-wheat cropping system occupying 26 million ha ofproductive land in Asia could be a major source ofN₂O as most of the fertilizer N in this region isconsumed by this system. Emission of N₂O asinfluenced by application of urea, urea plus farm yardmanure (FYM), and urea plus dicyandiamide (DCD), anitrification inhibitor, was studied in rice-wheatsystems of Indo-Gangetic plains of India. Total emissionof N₂O-N from the rice-wheat systems varied between654 g ha^-1 in unfertilized plots and 1570 g ha^-1 in urea fertilized plots. Application of FYM and DCDreduced emission of N₂O-N in rice. The magnitude ofreduction was higher with DCD. In wheat also N₂O-Nemission was reduced by DCD. FYM applied in rice had noresidual effect on N₂O-N emission in wheat. In riceintermittent wetting and drying condition of soilresulted in higher N₂O-N emission than that ofsaturated soil condition. Treatments with 5 irrigationsgave higher emissions in wheat than those with 3irrigations. In rice-wheat system, typical of a farmer'sfield in Indo-Gangetic plains, where 240 kg N isgenerally applied through urea, N₂O-N emission is1570 g ha^-1 (0.38% of applied N) and application ofFYM and DCD reduced it to 1415 and 1096 g ha^-1,respectively.     

环保型阻垢剂的研究进展

介绍了近年来循环冷却水系统中环保型阻垢剂的研究进展。重点阐述了价廉无污染的淀粉、单宁、木质素、纤维素、壳聚糖和腐植酸钠等天然高分子环保型阻垢剂,以及目前广泛应用的共聚物类的环保型阻垢剂和聚环氧琥珀酸、聚天冬氨酸、S-羧乙基硫代琥珀酸等新型环保型阻垢剂的阻垢性能和环境降解性能,并对这些阻垢剂的应用现状进行了阐述。而改性和复配是环保型阻垢剂的发展趋势。     

聚天冬氨酸-丝氨酸接枝聚合物的合成及阻垢性能

目的研究聚天冬氨酸-丝氨酸接枝聚合物的阻垢性能。方法以聚琥珀酰亚胺为母体,以丝氨酸为接枝单体,合成出聚天冬氨酸-丝氨酸接枝聚合物(PASPSE),采用静态阻垢法分别考察了聚合时间、聚合温度、原料配比对产物阻垢性能的影响。结果聚天冬氨酸-丝氨酸接枝聚合物合成的最佳条件为聚合时间18 h、聚合温度55℃、聚琥珀酰亚胺与丝氨酸原料配比(摩尔比)为1:1。该接枝聚合物对Ca CO3垢具有良好的螯合分散作用,其Ca CO3阻垢率随温度的升高、工作时间的延长、HCO3-与Ca2+含量之比的增大而降低。在90℃高温环境下,10 mg/L PASPSE的阻垢率可达95.5%。结论在高温水系统中,PASPSE对Ca CO3垢具有较好的阻垢性能。     

气相组分对氨吸收同步脱除模拟烟气SO2 和NOx 的影响

在pH值5.9～6.1,吸收液浓度≥1 mol·L-1的条件下,分析了模拟烟气的NOx氧化度、O2和SO2浓度,以及添加液相S(Ⅳ)氧化抑制剂Na2S2O3对SO2、NOx吸收脱除效率的影响.结果表明,氨可高效吸收脱除SO2和NO2,但对NO的吸收脱除效率几乎为0,因此,NO氧化是其吸收脱除NOx的前提.吸收液S(Ⅳ)浓度是影响NO2脱除效率的关键因素,气相O2浓度越高或SO2浓度越低,吸收液S(Ⅳ)浓度降低越快,继而使NO2吸收脱除效率降低越快.通过添加S(Ⅳ)氧化抑制剂S2O23-到吸收液,可在一定程度上抑制其氧化,从而延缓NO2吸收脱除效率的降低.     

DMPP对稻田田面水氮素转化及流失潜能的影响

采用杭嘉湖地区典型的小粉土和青紫泥土壤,进行水稻盆栽试验,研究新型硝化抑制剂3,4-二甲基吡唑磷酸盐(DMPP)对稻田田面水氮素转化及径流流失潜能的影响.结果表明,小粉土和青紫泥土壤稻田应用添加DMPP抑制剂的尿素,与常规尿素处理相比,田面水中铵态氮的浓度增加24.8%和16.7%,硝态氮浓度降低47.7%和70.9%,亚硝态氮浓度降低90.6%和88.9%,总无机氮浓度下降13.5%与23.1%,能显著减轻农田氮素流失对水环境存在的污染;DMPP可使田面水的电导率下降,降低盐基离子随农田排水或暴雨径流所导致的流失风险,有助于保护河流水体等地表水环境.     

聚环氧琥珀酸(钠)的合成及阻垢性能研究

以马来酸酐为原料,铬酸钾为催化剂合成了聚环氧琥珀酸(PESA),并在聚合初期和产物溶液中加入蒙脱土以除去C(rⅥ),研究了催化剂用量、蒙脱土加入量及不同外界条件下对产物阻碳酸钙性能的影响。结果表明,以钨酸钠和铬酸钾为催化剂合成的PESA具有相同的结构和相近的阻垢性,它们在高钙离子浓度、高温水系统中长时间停留对碳酸钙仍有较强的抑制作用,该工艺得到的样品C(rⅥ)含量<0.50mg/L,达到国家标准。     

Urease inhibitor reduces N losses and improves plant-bioavailability of urea applied in fine particle and granular forms under field conditions

A field lysimeter/mini plot experiment was established in a silt loam soil near Lincoln, New Zealand, to investigate the effectiveness of urea fertilizer in fine particle application (FPA), with or without the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT - “Agrotain”), in decreasing nitrogen (N) losses and improving N uptake efficiency. The five treatments were: control (no N) and ¹⁵N-labelled urea, with or without NBPT, applied to lysimeters or mini plots (unlabelled urea), either in granular form to the soil surface or in FPA form (through a spray) at a rate equivalent to 100 kg N ha⁻¹. Gaseous emissions of ammonia (NH₃) and nitrous oxide (N₂O), nitrate (NO₃⁻) leaching, herbage dry-matter (DM) production, N-response efficiency, total N uptake and total recovery of applied ¹⁵N in the plant and soil varied with urea application method and with addition of NBPT. Urea with NBPT, applied in granular or FPA form, was more effective than in application without NBPT: N₂O emissions were reduced by 7-12%, NH₃ emissions by 65-69% and NO₃⁻ leaching losses by 36-55% compared with granular urea. Urea alone and with NBPT, applied in FPA form increased herbage DM production by 27% and 38%, respectively. The N response efficiency increased from 10 kg DM kg⁻¹ of applied N with granular urea to 19 kg DM kg⁻¹ with FPA urea and to 23 kg DM kg⁻¹ with FPA urea plus NBPT. Urea applied in FPA form resulted in significantly (P < 0.05) higher ¹⁵N recovery in the shoots compared with granular treatments and this was improved further when urea in FPA form was applied with NBPT. These results suggest that applying urea with NBPT in FPA form has potential as a management tool in mitigating N losses, improving N-response efficiency and increasing herbage DM production in intensive grassland systems.