Trends in the content of acidifying and eutrophying compounds in atmospheric precipitation in an urbanized area

The trends in changing the content of sulfur and nitrogen in atmospheric precipitation in the territory of Minsk over an 18-year period are characterized on the basis of the analysis of the monitoring results of the chemical composition of atmospheric precipitation at the experimental site. A downtrend in the sulfur and nitrogen content combined with an uptrend in the precipitation acidity was identified. An average decrease (trend) in the content of sulfur in atmospheric precipitation for 2002–2019 was 0.019 mg S/dm3/year, of oxidized nitrogen – 0.008 mg/dm3, of reduced nitrogen – 0.019 mg/dm3. Over an 18-year period, the changes in the content of sulfur and nitrogen in atmospheric precipitation decreased the deposition of sulfur on average by 31.3 kg/km2/year, of oxidized nitrogen – by 15.4 kg/km2/year, of reduced nitrogen – by 25.6 kg/km2/year. It is shown that for the period from 2005 to 2012, the acidification potential of the natural environment decreased parallel to the reduction of the sulfur and nitrogen deposition; in the subsequent period, the trend of the acidification potential basically follows the trend of the precipitation of the main cations. It is revealed that the rates of average reduction in the content of oxidized sulfur and oxidized nitrogen in atmospheric precipitation in Minsk for the period from 2002 to 2017 are comparable to the rates of reduction of these compounds at the stations of the EMEP Program in Europe, and exceed those for reduced nitrogen.

Reduced Nitrogen Rate with Increased Planting Density Facilitated Grain Yield and Nitrogen Use Efficiency in Modern Conventional Japonica Rice

The past three decades have seen a pronounced development of conventional japonica rice from the 1990s, although little information is available on changes regarding grain yield and nutrient use efficiency during this process. Nine conventional japonica rice released during the 1990s, 2000s, and 2010s were grown under a reduced nitrogen rate, with increased planting density (RNID) and local cultivation practice (LCP) in 2017 and 2018. The rice from the 2010s had 3.6–5.5% and 7.0–10.1% higher (p < 0.05) grain yield than the 2000s and the 1990s, respectively, under RNID and LCP. The harvest index contributed more to genetic yield gain from the 1990s to the 2000s; whereas from the 2000s to 2010s, yield increase contributed through shoot biomass. Genetic improvement increased total nitrogen (N), phosphorus (P), and potassium (K) accumulation, and their use efficiencies. The rice from the 2010s showed a similar grain yield, whereas the 1990s and 2000s’ rice exhibited a lower (p < 0.05) grain yield under RNID relative to LCP. RNID increased N, P, and K use efficiencies, particularly the N use efficiency for the grain yield (NUEg) of the 2010s’ rice, compared with LCP. For three varietal types, RNID increased the panicles per m2, the filled-grain percentage, and the grain weight (p < 0.05) while decreasing spikelets per panicle of the 2010s’ rice. Compared with LCP, RNID reduced non-structural carbohydrate (NSC) content and shoot biomass, at heading and maturity, while increasing the remobilization of NSC and the harvest index, especially for the 2010s’ rice. Our results suggested the impressive progressive increase in grain yield and nutrient use efficiency of conventional japonica rice since the 1990s in east China. RNID could facilitate grain yield and NUEg for modern conventional japonica rice.

Effects of Reduced Nitrogen with Bio-Organic Fertilizer on Soil Properties, Yield and Quality of Non-Heading Chinese Cabbage

Fertilizer is extremely essential to increasing the yield of vegetables. However, excessively using fertilizers has had a negative impact on the yield and quality of vegetables as well as soil environment in recent years. Non-heading Chinese cabbage ‘yellow rose’ was applied to determine the influence of organic manure and inorganic fertilizer on the character of rhizosphere soil, the growth and quality of plants. There were five treatments: conventional fertilization (NF), a total nitrogen reduction of 20% (NF20), a total nitrogen reduction of 30% (NF30), a total nitrogen reduction of 20% with 100 kg·667 m−2 bio-organic fertilizer (BNF20) and a total nitrogen reduction of 30% with 200 kg·667 m−2 bio-organic fertilizer (BNF30). The results show that the content of nitrate nitrogen, organic matter in rhizosphere soil treated by BNF20 and BNF30, was significantly enhanced compared with NF. The yield, Vc and soluble protein of plants treated by BNF20 and BNF30 increased by 30.11%, 17.26%, 5.66% and 15.90%, 16.02%, 5.37%, respectively, compared with NF. On the contrary, the nitrate content significantly decreased in plants of BNF20 and BNF30 by 47.87% and 40.98% compared with NF. The significantly positive correlation was observed between nitrate nitrogen content in rhizosphere soil and the yield (p < 0.05). In conclusion, reduced nitrogen with bio-organic fertilizer can improve the yield and quality of ‘yellow rose’ cabbage by improving the quality of rhizosphere soil.

Seasonal Analysis of Reduced and Oxidized Nitrogen-Containing Organic Compounds at a Coastal Site

Nitrogen-containing organic compounds, which may be directly emitted to the atmosphere or may form via reactions with prevalent reactive nitrogen species (e.g. NH3, NOx, NO3), have important but uncertain effects on climate and human health. Using gas and liquid chromatography with soft ionization and high-resolution mass spectrometry, we performed a molecular-level speciation of functionalized organic compounds at a coastal site on the Long Island Sound in summer (during the LISTOS 2018 campaign) and winter. This region often experiences poor air quality due to the emissions of reactive anthropogenic, biogenic, and marine-derived compounds and their chemical transformation products. Indeed, we observed a range of functionalized compounds containing oxygen, nitrogen, and/or sulfur atoms resulting from a mix of direct emissions and chemical transformations, including photochemical processing in summer and aqueous-phase processing in winter. In both summer and winter, nitrogen-containing organic aerosols dominated the observed distribution of functionalized particle-phase species ionized by our analytical techniques, with 85 % and 68 % of measured compound abundance containing a nitrogen atom, respectively. Nitrogen-containing particles included reduced nitrogen functional groups (e.g. amines, imines, azoles) and common NOz contributors (e.g. organonitrates). The prevalence of reduced nitrogen functional groups observed in the particle-phase, while frequently paired with oxygen-containing groups elsewhere on the molecule, often rivaled that of oxidized nitrogen groups detected by our methods. Supplemental gas-phase measurements, collected on adsorptive samplers and analyzed with a novel liquid chromatography-based method, suggest that gas-phase reduced nitrogen compounds are possible contributing precursors to the observed nitrogen-containing particles. Altogether, this work highlights the prevalence of reduced nitrogen-containing compounds in the less-studied Northeastern U.S., and potentially in other regions with similar anthropogenic, biogenic, and marine source signatures.