Dry deposition of reactive nitrogen to marine environments: recent advances and remaining uncertainties

Many highly productive marine ecosystems exhibit nitrogen limitation or co-limitation. This article is a status review of research into the exchange of nitrogen between the atmosphere and these ecosystems with a particular focus on reactive nitrogen compounds. A summary of research conducted over the past ten years is presented and a perspective given as to remaining uncertainities and research needs. Looking toward development of coastal management modeling tools, we illustrate the processes that need to be resolved in order to accurately simulate the flux from the atmosphere and provide guidance on the required resolution of such models.     

许氏帆蚌耗氧率和排氨率研究

采用生态生理学方法研究了水温和体质量对许氏帆蚌(Hyriopsis schlegelii)耗氧率和排氨率的影响,为育珠蚌养殖生理生态学提供基础资料。用生化培养箱控制水温,winkler碘量法、纳氏试剂比色法测定耗氧率和排氨率。结果表明,在实验温度(9~30℃)条件下,许氏帆蚌的耗氧率为2.504~6.76mg/(kg.h),排氨率为1.963~5.689mg/(kg.h),其中耗氧率和排氨率在27℃达到最高值,30℃均开始下降。在适宜的温度范围内,许氏帆蚌的耗氧率和排氨率均与温度成正比,而与体质量呈负相关。     

2006—2017年安徽省人为源氨排放清单及特征

基于排放因子法建立了2006-2017年安徽省人为源氨排放清单,估算人为源氨的排放水平、变化趋势及其分布特征。结果表明,安徽省2017年人为源氨排放量较高的两个地区是阜阳市和六安市,而氨排放总量最小的是马鞍山,占全省氨排放总量的1.83%。安徽省氨平均排放强度为5.34 t·km^-2,其中阜阳市、淮南市及蚌埠市的排放强度均超过7 t·km^-2。2006-2017年畜禽养殖源产生的氨排放量处于增加状态,尤其是肉猪、肉鸡和肉鸭的贡献分别占到畜禽源氨排放总量的34.49%~38.39%、20.31%~32.8%和10.40%~16.42%。而氮肥施用导致的氨排放量表现出先增加后下降的趋势,2017年产生的氨排放量比2013年下降了28.71 kt。生物质燃烧、人体排放和氮肥生产是非农业源氨排放的主要来源,但由机动车产生的氨的贡献呈明显增长趋势,如从2006年的1.86%增长到2017年的7.47%,这与近年来安徽省汽车保有量不断增加有关。     

九龙江入海河口水质主要化学要素含量年际变化趋势和季节变化特征研究

文章根据2011—2020年九龙江河口入海监测断面表层水连续10年的水质监测数据得出：（1）2011—2020年九龙江河口入海监测断面表层水水质年际变化特征为近10年来九龙江入海河口水质得到了明显改善,尤其是2016—2020年高锰酸盐指数、氨氮、总磷、石油类浓度呈现持续下降的趋势,下降幅度较大,表明“十三五”期间九龙江流域水质得到了明显改善,但是总氮仍然超标严重。（2）2020年九龙江河口入海监测断面水质的季节变化特征为：高锰酸盐指数、氨氮、总氮、无机氮、总磷夏季含量相对较低,冬季含量相对较高。化学需氧量的季节变化特征为冬季含量相对较低,秋季含量相对较高。而石油类的季节变化特征为秋季含量相对较低,春季和冬季含量相对较高。（3）2011—2020年九龙江与闽江、晋江、龙江、木兰溪等福建省内其他主要入海河流河口入海监测断面水质对比分析得出,闽江、晋江河口入海监测断面水质较好,龙江、木兰溪河口入海监测断面水质较差,九龙江河口入海监测断面水质一般。研究结果以期为九龙江水环境规划与管理提供参考。     

硫酸镁—氨气法生产氢氧化镁

以硫酸镁和氨气为原料,直接制备高浓度阻燃剂氢氧化镁。通过单因素实验确定了最佳工艺条件,搅拌强度450r／rain,氨镁摩尔比2．4：1,氨气加入流量500mL／min,陈化时间60min,反应温度60℃,硫酸镁浓度2．50mol／L。用扫描电镜、X射线衍射仪和激光粒度仪表征产品的形貌、结构及粒度。在最佳工艺条件下得到,D5012．06μm,D90 18．99μm,料浆浓度7．37％,Mg收率68．02％,氢氧化镁纯度96．75％。     

胶州湾菲律宾蛤仔（Ruditapes philippinarum）呼吸排泄作用的现场研究

于2006年2月、5月、8月和11月四个季度月采用呼吸瓶法现场研究了胶州湾菲律宾蛤仔的呼吸排泄作用。结果表明,胶州湾菲律宾蛤仔呼吸排泄速率具有明显的季节变化趋势,春、夏季高于秋、冬季。不同生物学规格的蛤仔呼吸排泄速率具有明显的差异,单位个体耗氧率、排氨率和排磷率均随着个体大小的增加而增加,而单位体重的耗氧率、排氨率和排...     

盐度和pH对合浦珠母贝（Pinctada fucata）耗氧率和排氨率的影响

采用实验生态学方法,对3种规格的合浦珠母贝在不同盐度和pH下的耗氧率和排氨率进行了研究。结果表明,盐度对合浦珠母贝的耗氧率和排氨率有极显著影响（P〈0．01）。在盐度21—36的范围内,耗氧率和排氨率均随盐度的升高而降低,且单位体重耗氧率、排氨率随其个体的增大而变小;pH对合浦珠母贝的耗氧率有极显著影响（P〈0．01）...     

Random Monte Carlo simulation analysis and risk assessment for ammonia concentrations in wastewater effluent disposal

High concentrations of ammonia in a river can cause fish kills and harms to other aquatic organisms. A simple water quality model is needed to predict the probability of ammonia concentration violations as compared to the US Environmental Protection Agencys ammonia criteria. A spreadsheet with Random Monte Carlo (RMC) simulations to model ammonia concentrations at the mixing point (between a river and the effluent of a wastewater treatment plant) was developed with the use of Microsoft Excel and Crystal Ball add-in software. The model uses effluent and river ammonia, alkalinity, and total carbonate data to determine the probability density functions (PDFs) for the Monte Carlo simulations. Normal, lognormal, exponential and uniform probability distributions were tested using the Chi-square method and p-value associated with it to choose the best fit to the random data selected from the East Burlington wastewater treatment plant in North Carolina and the Clinch River in Tennessee. It is suggested that different options be tested with a minimum of three classes and a maximum of n/5 classes (n = number of data points) and the highest probability (p-value) for the PDF being tested be chosen. The results indicted that six violations to the EPA criterion for maximum concentration (CMC) were predicted when using 2000 RMC simulations and PDFs fitted to the available data, which violate the current criterion of no more than one violation over 3 years. All violations occur when the pH of the blend ranges from 8.0 to 9.0. No violations were found to the criteria of chronic concentration (CCC) using RMC.     

Characterisation of buddingtonite (NH4)[AlSi3O8] and ND4-buddingtonite (ND4)[AlSi3O8] using IR spectroscopy and Rietveld refinement of XRD spectra

Buddingtonite (NH₄)[AlSi₃O₈] and its deuterated analogue ND₄-buddingtonite (ND₄)[AlSi₃O₈] have been synthesised in 150-mg amounts at 500 and 400?°C and 500?MPa in 5-mm-wide, 4-cm-long Au capsules using René metal hydrothermal autoclaves. The resultant product consists of clumps of monoclinic crystals with diameters of 30–60?μm. The ND₄-buddingtonite contains minor amounts of NH₄-buddingtonite due to H₂ migration across the Au membrane. Using this synthesis technique resulted in >99% pure buddingtonite in 20% of the synthesis runs with the remaining synthesis runs containing very minor tobelite and quartz on the order of a few percent. IR spectra obtained from powdered samples are assigned on the basis of T _d symmetry for the ammonium molecule. They show triply degenerate vibrational bands (i.e. ν₃ and ν₄) and some overtones and combination modes from NH₄ ⁺ and ND₄ ⁺. While T _d symmetry for NH₄ ⁺ in buddingtonite is not completely correct due to distortion of the NH₄ ⁺ molecule, the non-cubic field is not large enough to cause a substantial splitting in the bands. However, this perturbation is documented in the IR spectra by a substantial increase in the FWHH as well as the occurrence of shoulders on the broadened bands. Rietveld analysis indicates that buddingtonite, like orthoclase, has a monoclinic structure with space group symmetry C2/m. Here, the NH₄ ⁺ molecule replaces the K⁺ cation on the nine fold coordinated A site which has m symmetry. Due to the larger size of the NH₄ ⁺ molecule, the N–O interatomic distances are larger than the K–O distances in pure orthoclase and range from 2.95 to 3.16?Å. This results in an increase in the volume of the polyhedron hosting the NH₄ ⁺ molecule. Also, in contrast to orthoclase, the polyhedron hosting the NH₄ ⁺ molecule becomes more regular. The rigid Al, Si tetrahedra of the framework adjust to this expansion of the A site by rotation. This results in larger unit cell parameters for buddingtonite when compared to natural and synthesised potassium feldspars. This increase is especially seen with respect to the lattice constants a and b and the monoclinic angle β which also are found to be extremely variable. In contrast, the c direction remains nearly unchanged. Investigations using IR spectroscopy indicate that it is unlikely that this variation in the a, b and β cell dimensions is caused by incorporation of H₃O⁺ or zeolitic water. Instead, it is more likely that substitution of NH₄ ⁺ for K⁺ coupled with Al, Si disorder are the chief contributors to these variations in the unit cell parameters for buddingtonite.     

Water-air transfer resistance for ammonia from flooded rice

Vertical flux densities of ammonia, water vapour and sensible heat were measured over a flooded rice field in China following the application of ammonium bicarbonate fertilizer. Aqueous and gaseous phase transfer resistances for ammonia were deduced from these measurements. The aqueous phase resistance was maximal in the morning and least in the afternoon. Stable stratification of the floodwater immediately adjacent to the air-water interface was observed during the morning when evaporation rates were low, and may be responsible for inhibiting the transfer of ammonia to the atmosphere.