The effect of nitrogen deposition on the species richness of acid grasslands in Denmark: a comparison with a study performed on a European scale

The effect of atmospheric nitrogen deposition on the species richness of acid grasslands was investigated by combining data from a large Danish monitoring program with a large European data set, where a significant non-linear negative effect of nitrogen deposition had been demonstrated (Stevens et al., 2010). The nitrogen deposition range in Denmark is relatively small and when only considering the Danish data a non-significant decrease in the species richness with nitrogen deposition was observed. However, when both data sets were combined, then the conclusion of the European survey was further corroborated by the results of the Danish monitoring. Furthermore, by combining the two data sets a more comprehensive picture of the threats to the biodiversity of acid grasslands emerge; i.e., species richness in remnant patches of acid grassland in intensively cultivated agricultural landscapes is under influence not only from nitrogen deposition, but also from current and historical land use.     

Enhanced nitrogen deposition exacerbates the negative effect of increasing background ozone in Dactylis glomerata, but not Ranunculus acris

The combined impacts of simulated increased nitrogen (N) deposition (75 kg N ha⁻¹ yr⁻¹) and increasing background ozone (O₃) were studied using two mesotrophic grassland species (Dactylis glomerata and Ranunculus acris) in solardomes, by means of eight O₃ treatments ranging from 15.5 ppb to 92.7 ppb (24 h average mean). A-C_i curves were constructed for each species to gauge effects on photosynthetic efficiency and capacity, and effects on biomass partitioning were determined after 14 weeks. Increasing the background concentration of O₃ reduced the healthy above ground and root biomass of both species, and increased senesced biomass. N fertilisation increased biomass production in D. glomerata, and a significantly greater than additive effect of O₃ and N on root biomass was evident. In contrast, R. acris biomass was not affected by high N. The study shows the combined effects of these pollutants have differential implications for carbon allocation patterns in common grassland species.     

水动力条件对龙须菜N吸收的影响

通过在室外0.5t的玻璃缸桶内对不同放养密度的龙须菜进行流水和静水的氮吸收比较养殖试验,发现龙须菜可以同时吸收介质中的铵态氮和硝态氮;静水导致水体中的pH值升高,最大的上升了1单位以上;龙须菜的吸收造成介质中营养盐的减少,在试验开始3h后,静水组的高放养密度处理中出现氮吸收抑制现象;采用流水方式,水流速度在(160～175)L·h-1范围,养殖介质的条件相对稳定,藻体所吸收的氮量也较多,流水组的2kg和4kg处理分别比静水相应处理多吸收N为5.80、10.25(16∶00)和7.64、11.59mg(18∶00),分别比静水条件增加24、31和18、27%。     

Current status of municipal wastewater treatment plants in North-east China: implications for reforming and upgrading

● The performance and costs of 20 municipal WWTPs were analyzed. ● Effluent COD and NH₄⁺-N effluent exceed the limits more frequently in winter. ● Nitrification and refractory pollutant removal are limited at low temperatures. ● To meet the national standards, electricity cost must increase by > 42% in winter. ● Anammox, granular sludge, and aerobic denitrification are promising technologies. Climate affects the natural landscape, the economic productivity of societies, and the lifestyles of its inhabitants. It also influences municipal wastewater treatment. Biological processes are widely employed in municipal wastewater treatment plants (WWTPs), and the prolonged cold conditions brought by the winter months each year pose obstacles to meeting the national standards in relatively cold regions. Therefore, both a systematic analysis of existing technical bottlenecks as well as promising novel technologies are urgently needed for these cold regions. Taking North-east China as a case, this review studied and analyzed the main challenges affecting 20 municipal WWTPs. Moreover, we outlined the currently employed strategies and research issues pertaining to low temperature conditions. Low temperatures have been found to reduce the metabolism of microbes by 58% or more, thereby leading to chemical oxygen demand (COD) and NH₄⁺-N levels that have frequently exceeded the national standard during the winter months. Furthermore, the extracellular matrix tends to lead to activated sludge bulking issues. Widely employed strategies to combat these issues include increasing the aeration intensity, reflux volume, and flocculant addition; however, these strategies increase electricity consumption by > 42% in the winter months. Internationally, the processes of anaerobic ammonium oxidation (anammox), granular sludge, and aerobic denitrification have become the focus of research for overcoming low temperature. These have inspired us to review and propose directions for the further development of novel technologies suitable for cold regions, thereby overcoming the issues inherent in traditional processes that have failed to meet the presently reformed WWTP requirements.     

总氮浓度对3种沉水植物生长的影响

在1/40 Hoagland营养液的基础上,采用NH4NO3为氮源,设定了2、4、8、16 mg·L-1 4个不同总氮浓度的培养液,以洗净的长江河沙为栽培基质,分别对3种我国湖泊中常见的沉水植物马来眼子菜(Potamogetonmalaianus)、苦草(Vallisneria natans)和黑藻(Hydrilla verticillata)进行了为期45d的水培试验,研究了水体中不同总氮浓度对3种沉水植物分枝数、根长、株高、鲜重等生长指标的影响,以期为富营养化水体中沉水植被的恢复与先锋物种的选择提供科学依据.结果表明,试验结束时不同处理的马来眼子菜的各项生长指标均显著增加,苦草没有产生新的分枝,黑藻的根长没有显著的增加;不同处理的3种沉水植物的鲜重在试验结束时均有显著增加,其增加的顺序表现为马来眼子菜＞苦草＞黑藻的趋势;植物株高和鲜重的净积累随处理浓度的升高而显著增加,根系的净伸长则随处理浓度的升高而显著降低.由于马来眼子菜所有的生长指标均表现出比苦草和黑藻有显著的生长优势,因此,在符合本试验条件的水体沉水植被的恢复过程中可以作为先锋植物.     

水磨河氮含量分布及时空变化初探

根据2005年水质监测结果,对水磨河无机氮的特征分布及相互之间的相关性进行了初步分析探讨,结果显示,水磨河无机氮中硝酸盐氮含量最高,亚硝酸盐氮含量最低,亚硝酸盐氮与氨氮之间有非常显著的线性关系.通过对1991-2005年的监测资料分析,表明水磨河各断面无机氮含量呈下降趋势,但水磨河自上而下无机营养盐N总体浓度升高,说明氮污染还在延续,形势不容乐观.     

连云港地区近地面臭氧浓度月均浓度变化特征

利用2014—2018年连云港地区的监测资料,分析了O3的月变化特征,得出O3与NO2、CO呈负相关关系,并给出了相对合理的解释。     

稻田氮磷流失控制技术研究

分析了稻田氮磷流失的途径,以及降雨、秸秆还田、施肥等影响因素,综述了养分管理、水分管理、生态拦截、农田尾水回用等稻田氮磷流失控制技术的研究现状,提出应探索稻田氮磷流失源头控制和末端管控机制,加强生态拦截技术优化配置与性能研究。     

Nitrogen Flow Analysis in Huizhou, South China

Eutrophication due to uncontrolled discharges of nitrogen and phosphorus has become a serious pollution problem in many Chinese rivers. This article analyzes the nitrogen flow in Huizhou City in the East River watershed in south China. The material accounting method was applied to investigate the nitrogen flows related to human activities, which consist of the natural and anthropogenic systems. In Huizhou City, the nonpoint source pollution was quantified by the export coefficient method and the domestic discharge was estimated as the product of per capita nitrogen contribution and population. This research was conducted based on statistical information and field data from 1998 in the Huizhou City. The results indicated that the major nitrogen flows in this area were river loads, fertilizer and feedstuff imports, atmospheric deposition, animal manure volatilization, and processes related to burning and other emissions. In 1998, about 40% of the nitrogen was retained in the system and could result in potential environmental problems. Nitrogen export was mainly by rivers, which account for about 57% of the total nitrogen exported. Comparisons made between the East River and the Danube and Yangtze Rivers show that the unit area nitrogen export was of the same magnitude and the per capita nitrogen export was comparable.     

Nitrogen dynamics of a mountain forest on dolomitic limestone--a scenario-based risk assessment

The dominant nitrogen (N) fluxes were simulated in a mountain forest ecosystem on dolomitic bedrock in the Austrian Alps. Based on an existing small-scale climate model the simulation encompassed the present situation and a 50-yr projection. The investigated scenarios were current climate, current N deposition (SC1) and future climate (+2.5 degrees C and +10% annual precipitation) with three levels of N deposition (SC2, 3, 4). The microbially mediated N transformation, including the emission of nitrogen oxides, was calculated with PnET-N-DNDC. Soil hydrology was calculated with HYDRUS and was used to estimate the leaching of nitrate. The expected change of the forest ecosystem due to changes of the climate and the N availability was simulated with PICUS. The incentive for the project was the fact that forests on dolomitic limestone stock on shallow Rendzic Leptosols that are rich in soil organic matter are considered highly sensitive to the expected environmental changes. The simulation results showed a strong effect due to increased temperatures and to elevated levels of N deposition. The outflux of N, both as nitrate (6-25kg Nha(-1)yr(-1)) and nitrogen oxides (1-2kg Nha(-1)yr(-1)), from the forest ecosystem are expected to increase. Temperature exerts a stronger effect on the N(2)O emission than the increased rate of N deposition. The main part of the N emission will occur as N(2) (15kg Nha(-1)yr(-1)). The total N loss is partially offset by increased rates of N uptake in the biomass due to an increase in forest productivity.