盐生野菜中硝酸盐·亚硝酸盐·维生素C含量的测定

测定了东营市9种盐生野菜和几种日常食用的蔬菜中硝酸盐、亚硝酸盐及维生素C的含量。结果证明:茵陈蒿、山苦荬、酸模、苣荬菜、蒙古雅葱符合无公害蔬菜标准,可以食用,并且他们都含有较多的维生素C,营养价值较高。灰绿藜、藜硝酸盐含量超标,地肤、翅碱蓬、灰绿藜亚硝酸盐含量超标,这些野菜不宜食用。     

八种中式烹饪工艺对牛肉中多环芳烃、反式脂肪酸和亚硝酸盐的影响

【目的】从蒸、煮、炖、烤、炸、煎、干制及腌制八种传统中式烹饪工艺中筛选获得有害物质较少的牛肉处理工艺,为消费者选择有害物质含量较低的烹饪工艺提供理论参考。【方法】通过调控烤、炸、煎3种高温处理的温度和时间,对比分析多环芳烃(PAHs)、反式油酸(C_(18:1 trans-9))及亚硝酸盐3类有害物质的组分及含量,选出较优的烤、炸、煎烹饪条件;在此基础上,综合分析烤、炸、煎与蒸、煮、炖、干制及腌制8种烹饪工艺对牛肉中有害物质的影响,进而选择较优的中式烹饪工艺。试验分别采用高效液相色谱外标法、气相色谱-质谱外标法及分光光度法测定牛肉中PAHs、C_(18:1 trans-9)及亚硝酸盐的含量。【结果】对照组中共检测出芘、苯并[a]蒽、苣和苯并[k]荧蒽4种,烤制以160—180℃处理为较优,有5种PAHs且含量低,炸制以3—4 min处理含量较低,煎制以2—3 min处理含量较低;8种中式烹饪中,炸、煎的肉样中PAHs种类最多,炸、腌制的肉样中苯并[a]蒽含量较高,蒸制及煎制的肉样中苣含量较高,烤、炸、煎的肉样中苯并[b]荧蒽含量较高,炸、煎的肉样中苯并[k]荧蒽、苯并[a]芘和二苯并[a,h]蒽含量较高。烤制温度对C_(18:1 trans-9)含量影响不显著(P0.05),炸制3 min和煎制2min的肉样中C_(18:1 trans-9)含量均最低(P0.05);8种中式烹饪中,炸、煎的肉样中C_(18:1 trans-9)含量较高(P0.05)。烤制160℃和180℃的肉样中亚硝酸盐含量均较低,炸制3 min和煎制2 min的亚硝酸盐含量最低(P0.05);8种烹饪工艺中,炸、煎及腌制的肉样中亚硝酸盐含量较高(P0.05)。【结论】对烤、炸、煎3种高温处理,肉样在160℃下烤制40 min,在226—228℃下炸制3 min、煎制2 min时3类有害物质含量较低;综合分析8种工艺,蒸制、煮制、炖制及干制的肉样中3类有害物质种类较少且含量较低。     

DMPP mitigates N2O and NO productions by inhibiting ammonia-oxidizing bacteria in an intensified vegetable field under different temperature and moisture regimes

Vegetable soils with high nitrogen input are major sources of nitrous oxide (N₂O) and nitric oxide (NO), and incorporation of the nitrification inhibitor 3, 4-dimethylpyrazole phosphate (DMPP) into soils has been documented to effectively reduce emissions. However, the efficiency of DMPP in terms of soil N₂O and NO mitigations varies greatly depending on soil temperature and moisture levels. Thus, further evaluations of DMPP efficiency in diverse environments are required to encourage widespread application. A laboratory incubation study (28 d) was established to investigate the interactive effects of DMPP, temperature (15, 25, and 35 ℃), and soil moisture (55% and 80% of water-holding capacity (WHC)) on net nitrification rate, N₂O and NO productions, and gene abundances of nitrifiers and denitrifiers in an intensive vegetable soil. Results showed that incubating soil with 1% DMPP led to partial inhibition of the net nitrification rate and N₂O and NO productions, and the reduction percentage of N₂O production was higher than that of NO production (69.3% vs. 38.2%) regardless of temperature and soil moisture conditions. The increased temperatures promoted the net nitrification rate but decreased soil N₂O and NO productions. Soil moisture influenced NO production more than N₂O production, decreasing with the increased moisture level (80%). The inhibitory effect of DMPP on cumulative N₂O and NO productions decreased with increased temperatures at 55% WHC. Conversely, the inhibitory effect of DMPP on cumulative N₂O production increased with increased temperatures at 80% WHC. Based on the correlation analyses and automatic linear modeling, the mitigation of both N₂O and NO productions from the soil induced by DMPP was attributed to the decreases in ammonia-oxidizing bacteria (AOB) amoA gene abundance and NO^-₂-N concentration. Overall, our study indicated that DMPP reduced both N₂O and NO productions by regulating the associated AOB amoA gene abundance and NO^-₂-N concentration. These findings improve our insights regarding the implications of DMPP for N₂O and NO mitigations in vegetable soils under various climate scenarios.     

Determination of nitrite in soil extracts and water samples by a nitrogen oxide electrode

Abstract

Work to evaluate the Orion nitrogen oxide electrode indicated that this electrode can be used satisfactorily for determination of nitrite in soil extracts and water samples. The electrode method of analysis described is simple, rapid, and precise, and its results agree closely with those obtained by the colorimetric method of Griess‐Ilosvay. The electrode method has the advantage that its results are not affected by color or turbidity or by Cu²⁺ and Hg²⁺ present in samples under analysis     

食用醋精抑制亚硝酸盐产生的试验

亚硝酸盐中毒(Nitrite poisonig)是畜禽常发生的一种中毒病。用白菜等含硝酸盐较多的菜类作猪的饲料,因调制加工不合理,会产生大量的亚硝酸盐,喂后引起猪急性中毒,常来不急抢救而死亡,对养猪业危害较大。用食用醋精加入调制白菜的浸泡液中,使其pH值为4时,完全可抑制反硝化细菌的活动,基本上不会产生亚硝酸盐。这是因为醋酸是含有2个碳原子的有机酸,对反硝化细菌毒性大,使菌体内DNA和ATP受到破坏,细菌失去脱氮作用所致。用醋精作调制白菜的抑制剂,会起到预防畜禽亚硝盐中毒的作用。     

硝化细菌的分离鉴定

应用硝化细菌选择性培养基,从南京的土壤和水体中筛选到6株硝化细菌,包括3株亚硝化菌和3株硝化菌,对其生理生化特性、温度敏感性、耐盐性、抗生素抗性、及硝化能力等生物学特性进行了测定。结果表明,6株细菌均为G-,菌体杆状或球状。生长缓慢,培养120 h以后才进入对数生长期,5 d左右形成菌落。最适生长温度为25~30℃。耐受偏碱环境。不耐盐,6株菌都能耐受的盐浓度范围是0.05%~0.3%。通气量对该菌的生长没有太大影响。6株菌株对不同的抗生素具有抗性。其中,菌株J2的抗药谱最窄,只抗卡那霉素。6株菌只能在以碳酸钠或者碳酸氢钠为唯一碳源、以硫酸铵或者亚硝酸盐为唯一氮源的培养基上生长良好。菌株硝化能力不同,其中菌株J2硝化能力较强,在基础培养基中200 h,该菌转化NO2-42%左右,可以作为降解鱼塘中和饲料中亚硝酸盐的硝化菌候选株。     

Tolerance of juvenile black sea bass Centropristis striata to acute ammonia and nitrite exposure at various salinities

ABSTRACT:   Experiments were conducted to determine the acute tolerance of juvenile (mean weight ± standard error, 9.9 ± 0.9 g) black sea bass Centropristis striata to environmental un-ionized ammonia-nitrogen (NH₃-N) and nitrite-nitrogen (NO₂-N) exposure at various salinities. Specifically, median lethal concentrations (LC50 values) of NH₃-N and NO₂-N at 24, 48 and 96 h of exposure were determined at salinities of 10, 20 and 30 g/L at 22°C. With the exception of LC50 values determined at 48 h, median lethal concentrations of NH₃-N to black sea bass were not influenced by environmental salinity; 24, 48, and 96 h LC50 values ranged from 0.81 to 0.85, 0.65–0.77, and 0.46–0.54 mg-NH₃-N/L, respectively. In contrast, tolerance of black sea bass to environmental NO₂-N was compromised at reduced salinities. Median lethal concentrations of NO₂-N to fish at 24, 48 and 96 h of exposure ranged from 288.3 to 429.0, 258.4 to 358.8 and 190.0 to 241.9 mg-NO₂-N/L, respectively. Results indicate that while juvenile black sea bass are relatively sensitive to acute NH₃-N exposure, they are highly resistant to NO₂-N exposure.     

NO^—2对水稻生长发育的影响

大水培条件下，当ＮＯ＾－２浓度低于６０ｋｇ时，秧苗干重，鲜重及含Ｎ量都随ＮＯ＾－２浓度升高而增加；当ＮＯ＾－２浓度超过６０ｍｇ／ｋｇ，干重，鲜重及含Ｎ则随浓度升高而降低，但这种降低可因Ｆｅ＾＋＋的存在而减弱，在相同施Ｎ量下，秧苗干重，苗高，分蘖数和含Ｎ量也会因为ＮＯ＾－２的施用而下降。ＮＯ＾－２显著影响根系呼吸强度和秧苗含水量，根系吸氧量及秧苗含水量随ＮＯ＾－２浓度升而减少。ＮＯ＾－２提高亚硝...     

Numbers of nitrate-reducing bacteria in the rumen as estimated by competitive polymerase chain reaction

Cell numbers of known species of nitrate- and nitrite-reducing bacteria, Selenomonas ruminantium, Veillonella parvula and Wollinella succinogenes , in the rumen of goats (25–30 kg) were estimated by competitive polymerase chain reaction (PCR). The number of S. ruminantium was the largest of the three species examined, and tended to be greater in goats fed a high-concentrate diet (5.6 × 10⁷ cells/mL rumen fluid) than in goats fed a high-roughage diet (1.3 × 10⁷ cells/mL). The number of V. parvula tended to be greater when goats were fed a high-roughage diet (6.7 × 10³/mL) than when fed a high-concentrate diet (3.2 × 10³/mL). The number of W. succinogenes was below the detectable level (< 1.0 × 10²/mL) when a high-concentrate diet was fed, but was significantly increased by feeding a high-roughage diet (1.6 × 10³/mL). Addition of potassium nitrate (6 g/day) to the high-concentrate diet tended to increase V. parvula , and significantly increased W. succinogenes , indicating that these two bacteria can be increased by feeding a diet containing nitrate.     

潮州产13种野菜中硝酸盐和亚硝酸盐的含量

根据潮州产13种野菜中硝酸盐和亚硝酸盐含量的测定结果,参考蔬菜中硝酸盐含量分级评价标准和我国的无公害蔬菜亚硝酸盐含量限量标准(≤4.0mgkg),对13种野菜的品质进行了评价。结果显示,菜、酢浆草、野茼蒿、黄鹌菜和腋花蓼硝酸盐含量低于轻度污染水平,亚硝酸盐含量低于我国制定的无公害蔬菜亚硝酸盐含量的限量标准(≤4.0mgkg),属于一级无公害野菜,可以安全食用;少花龙葵、马齿苋、鳢肠、叶下珠、铁苋菜、小藜和牛繁缕的硝酸盐含量高于432mgkg,而低于785mgkg,亚硝酸盐含量低于限量标准(≤4.0mgkg),属于二级野菜,不宜生食,煮熟和盐渍可安全食用;鼠曲草的硝酸盐含量高于785mgkg,低于1440mgkg,属于三级野菜,不可生食和盐渍,可熟食。