Potential transition in the effects of atmospheric nitrogen deposition in China

Does Bidens pilosa L. Affect Carbon and Nitrogen Contents, Enzymatic Activities, and Bacterial Communities in Soil Treated with Different Forms of Nitrogen Deposition?

The deposition of nitrogen in soil may be influenced by the presence of different nitrogen components, which may affect the accessibility of soil nitrogen and invasive plant-soil microbe interactions. This, in turn, may alter the success of invasive plants. This study aimed to clarify the influences of the invasive plant Bidens pilosa L. on the physicochemical properties, carbon and nitrogen contents, enzymatic activities, and bacterial communities in soil in comparison to the native plant Pterocypsela laciniata (Houtt.) Shih treated with simulated nitrogen deposition at 5 g nitrogen m-2 yr-1 in four forms (nitrate, ammonium, urea, and mixed nitrogen). Monocultural B. pilosa resulted in a notable increase in soil pH but a substantial decrease in the moisture, electrical conductivity, ammonium content, and the activities of polyphenol oxidase, β-xylosidase, FDA hydrolase, and sucrase in soil in comparison to the control. Co-cultivating B. pilosa and P. laciniata resulted in a notable increase in total soil organic carbon content in comparison to the control. Monocultural B. pilosa resulted in a notable decrease in soil bacterial alpha diversity in comparison to monocultural P. laciniata. Soil FDA hydrolase activity and soil bacterial alpha diversity, especially the indices of Shannon's diversity, Simpson's dominance, and Pielou's evenness, exhibited a notable decline under co-cultivated B. pilosa and P. laciniata treated with nitrate in comparison to those treated with ammonium, urea, and mixed nitrogen.

The driving effects of nitrogen deposition on nitrous oxide and associated gene abundances at two water table levels in an alpine peatland

Alpine peatlands are recognized as a weak or negligible source of nitrous oxide (N2O). Anthropogenic activities and climate change resulted in the altered water table (WT) levels and increased nitrogen (N) deposition, which could potentially transition this habitat into a N2O emission hotspot. However, the underlying mechanism related with the effects is still uncertain. Hence, we conducted a mesocosm experiment to address the response of growing-season N2O emissions and the gene abundances of nitrification (bacterial amoA) and denitrification (narG, nirS, norB and nosZ) to the increased N deposition (20 kg N ha-1 yr-1) at two WT levels (WT-30, 30 cm below soil surface; WT10, 10 cm above soil surface) in the Zoige alpine peatland, Qinghai-Tibetan Plateau. The results showed that the WT did not affect N2O emissions, and this was attributed with the limitation of soil NO3-. The higher WT level increased denitrification (narG and nirS gene abundance) resulting in the depletion of soil NO3-, but the consequent NO3- deficiency further limited denitrification, while the WT did not affect nitrification (bacterial amoA gene abundance). Meanwhile, the N deposition increased N2O emissions, regardless of WT levels. This was associated with the N-deposition induced increase in denitrification-related gene abundances of narG, nirS, norB and nosZ at WT-30 and narG at WT10. Additionally, the N2O emission factor assigned to N deposition was 1.3 % at WT-30 and 0.9 % at WT10, respectively. Our study provided comprehensive understanding of the mechanisms referring N2O emissions in response to the interactions between climate change and human disturbance from this high-altitude peatland.

The Impact of Medical and Health Fiscal Expenditures on Pharmaceutical Industry Stock Index in China

This paper investigates the relationship between fiscal expenditure on health care (FE) and the pharmaceutical industry stock index (SP) by using full-sample and sub-sample rolling-window bootstrap causality tests. It can be observed that there is both a positive and negative relationship between FE and SP. FE will promote the rise of the pharmaceutical stock market, which proves the Keynesian theory, while the result that FE negatively affects SP supports the classical theory. In turn, SP positively impacts FE, which indicates that the development of the pharmaceutical industry and the increase in medical and health expenditures can promote each other. In addition, the negative influence of SP on FE suggests that the impact of the pharmaceutical index on fiscal expenditure needs to be judged in conjunction with other events and market conditions. In complex economic conditions, investors can rationally consider the industry situation of the pharmaceutical market and benefit by optimising their investment portfolios. The government can regulate and guide the pharmaceutical industry by adjusting the fiscal expenditure on health care, thereby promoting the sustainable and stable development of the financial market.

Soil Microbial Community Response to Nitrogen Application on a Swamp Meadow in the Arid Region of Central Asia

Although a large number of studies have reported the importance of microbial communities in terrestrial ecosystems and their response to nitrogen (N) application, it is not clear in arid alpine wetlands, and the mechanisms involved need to be clarified. Therefore, the response of the soil microbial community in a swamp meadow to short-term (1 year) N application (CK: 0, N1: 8, N2: 16 kg⋅N⋅hm^–2⋅a^–1) was studied using 16S/ITS rRNA gene high-throughput sequencing technology. Results showed that N application had no significant effect on soil microbial community diversity, but significantly changed soil bacterial community structure. N1 and N2 treatments significantly reduced the relative abundance of Chloroflexi (18.11 and 32.99% lower than CK, respectively). N2 treatment significantly reduced the relative abundance of Nitrospirae (24.94% lower than CK). Meanwhile, N application reduced the potential function of partial nitrogen (N) and sulfur (S) cycling in bacterial community. For example, compared with CK, nitrate respiration and nitrogen respiration decreased by 35.78–69.06%, and dark sulfide oxidation decreased by 76.36–94.29%. N application had little effect on fungal community structure and function. In general, short-term N application directly affected bacterial community structure and indirectly affected bacterial community structure and function through available potassium, while soil organic carbon was an important factor affecting fungal community structure and function.

Nitrogen enrichment buffers phosphorus limitation by mobilizing mineral-bound soil phosphorus in grasslands

Phosphorus (P) limitation is expected to increase due to nitrogen (N)-induced terrestrial eutrophication, although most soils contain large P pools immobilized in minerals (P_i ) and organic matter (P_o ). Here we assessed whether transformations of these P pools can increase plant available pools alleviating P limitation under enhanced N availability. The mechanisms underlying these possible transformations were explored by combining results from a 10-year field N-addition experiment and a 3700-km transect covering wide ranges in soil pH, soil N, aridity, leaching, and weathering that can affect soil P status in grasslands. Nitrogen addition promoted dissolution of immobile P_i (mainly Ca-bound recalcitrant P) to more available forms of P_i (including Al- and Fe-bound P fractions and Olsen P) by decreasing soil pH from 7.6 to 4.7, but did not affect P_o . Soil total P declined by 10% from 385 ± 6.8 to 346 ± 9.5 mg kg^-1 , while available-P increased by 546% from 3.5 ± 0.3 to 22.6 ± 2.4 mg kg^-1 after 10-year N addition, associated with an increase in P_i mobilization, plant uptake, and leaching. Similar to the N-addition experiment, the drop in soil pH from 7.5 to 5.6 and increase in soil N concentration along the grassland transect were associated with an increased ratio between relatively mobile P_i and immobile P_i . Our results provide a new mechanistic understanding of the important role of soil P_i mobilization in maintaining plant P supply and accelerating biogeochemical P cycles under anthropogenic N enrichment. This mobilization process temporarily buffers ecosystem P-limitation or even causes P eutrophication but will extensively deplete soil P pools in the long run. This article is protected by copyright. All rights reserved.

Effect of atmospheric nitrogen deposition and its components on carbon flux in terrestrial ecosystems in China

Long-term atmospheric nitrogen (N) deposition increases bioavailable N in terrestrial ecosystems, thereby influencing ecosystem productivity. However, how N deposition and its components (i.e., NO₃^--N and NH₄⁺-N) influence the spatial pattern of productivity in terrestrial ecosystems in China remains unknown. Here, we utilize published data including carbon (C) fluxes from eddy flux tower (gross ecosystem productivity, ecosystem respiration, and net ecosystem productivity) and the corresponding climate and N deposition data for 60 typical ecosystems in China. The objective was to investigate the effect of N deposition on ecosystem productivity and explore the variations of N use efficiency (NUE). Our results reveal that atmospheric total N deposition is significantly correlated with C fluxes of terrestrial ecosystems in China. Ecosystems respond variably to different components of N deposition. In detail, forest ecosystem marginally correlated with NO₃^--N and wet deposition, while grassland ecosystem significantly correlated with NH₄⁺-N and dry deposition. NUE of productivity induced by N deposition in Chinese terrestrial ecosystems was 53.95 ± 40.30 g C g^-1 N, and it was influenced by precipitation and aridity index. This study quantifies the contribution of total N deposition and its associated components to productivity in terrestrial ecosystems in China, offering vital information for regional C and N management.

Can thermal intensification be considered a sustainable way for greening Fenton processes?

Life cycle assessment and kinetic modeling were used to elucidate the impact of thermal intensification (TI) on resource consumption and the techno-economic feasibility of a Fenton process at laboratory scale. Increasing temperature from 25 to 55 °C lowers treatment time (96.5%) and electricity use (67.8%) due to the positive impact of temperature on the reaction rate; however, beyond 50 °C no significant diminution in energy use, emissions, and operating cost was observed. The environmental footprint of the process is linked with energy use, operating pH, and the electricity share of the country; nevertheless, the impact of transport and infrastructure materials was lower. At 55 °C and pH of 2.8, emissions of precursors of freshwater and marine eutrophication, particulate matter formation, and ionizing radiation were reduced more than half; besides, in most of the midpoint categories, pondered by the ReCiPe-2016 method, emissions were lowered ca. 43.3%. The endpoint categories human health, ecosystem quality, and resource availability had a significant decline in disability-adjusted life years (46.0%), time-integrated species loss (42.0%), and surplus cost (33.1%). Harnessing the energy present in the wastewater itself decreased 41.9% global warming potential (GWP), but the use of steam for heating raised it 718.8%. In countries where electricity generation is dependent on fossil fuels, GWP could increase (2.0-20.0%) whereas GWP would decrease (8.8-9.4%) when renewable energy sources dominate. Operating at 55 °C and pH of 5.5 rose the reaction time (1835.5%), GWP (29.3%), particulate matter formation (44.3%), terrestrial acidification (21.8%), marine (48.9%), and freshwater eutrophication (66.7%). TI of Fenton processes could increase their treatment capacity with a small reduction in the quality of the effluent; furthermore, they can be made affordable for low-to-medium scale industries in emerging economies due to decreased resources consumption and emissions, leading to a lower treatment cost (US$0.49/m³).

The impact of air pollution on terrestrial managed and natural vegetation

Although awareness that air pollution can damage vegetation dates back at least to the 1600s, the processes and mechanisms of damage were not rigorously studied until the late twentieth century. In the UK following the Industrial Revolution, urban air quality became very poor, with highly phytotoxic SO₂ and NO₂ concentrations, and remained that way until the mid-twentieth century. Since then both air quality, and our understanding of pollutants and their impacts, have greatly improved. Air pollutants remain a threat to natural and managed ecosystems. Air pollution imparts impacts through four major threats to vegetation are discussed through in a series of case studies. Gas-phase effects by the primary emissions of SO₂ and NO₂ are discussed in the context of impacts on lichens in urban areas. The effects of wet and dry deposited acidity from sulfur and nitrogen compounds are considered with a particular focus on forest decline. Ecosystem eutrophication by nitrogen deposition focuses on heathland decline in the Netherlands, and ground-level ozone at phytotoxic concentrations is discussed by considering impacts on semi-natural vegetation. We find that, although air is getting cleaner, there is much room for additional improvement, especially for the effects of eutrophication on managed and natural ecosystems. This article is part of a discussion meeting issue 'Air quality, past present and future'.