Atmospheric fine particles in a typical coastal port of Yangtze River Delta.

In recent decades, coastal ports have experienced rapid development and become an important economic and ecological hub in China. Atmospheric particle is a research hotspot in atmospheric environmental sciences in inland regions. However, few studies on the atmospheric particle were conducted in coastal port areas in China, which indeed suffers atmospheric particle pollution. Lack of the physicochemical characteristics of fine particles serves as an obstacle toward the accurate control for air pollution in the coastal port area in China. Here, a field observation was conducted in an important coastal port city in Yangtze River Delta from March 6 to March 19, 2019. The average PM2.5 concentration was 63.7 ± 27.8 µg/m3 and NO3-, SO42-, NH4+, and organic matter accounted for ~60% of PM2.5. Fe was the most abundant trace metal element and V as the ship emission indicator was detected. Transmission electron microscopy images showed that SK-rich, soot, Fe, SK-soot and SK-Fe were the major individual particles in the coastal port. V and soluble Fe were detected in sulfate coating of SK-Fe particles. We found that anthropogenic emissions, marine sea salt, and secondary atmosphere process were the major sources of fine particles. Backward trajectory analysis indicated that the dominant air masses were marine air mass, inland air mass from northern Zhejiang and inland-marine mixed air mass from Shandong and Shanghai during the sampling period. The findings can help us better understand the physicochemical properties of atmospheric fine particles in the coastal port of Eastern China.

Changes in the Microbiome of Sugarcane (Saccharum spp. Hybrids.) Rhizosphere in Response to Manganese Toxicity.

Manganese toxicity has limited sugarcane (Saccharum spp. hybrid.) growth and production in acidic soils in south China. The rhizosphere plays an irreplaceable role in plant adaptation to soil abiotic stress, but the responses of the sugarcane rhizosphere to manganese toxicity are still unknown. We designed pot experiments in Mn-rich acidic soil, collected the sugarcane rhizosphere and bulk soil samples, and then investigated the changes in Mn-related soil parameters and microbiome. The results indicated that the water-soluble and exchangeable manganese concentrations in the sugarcane rhizosphere were significantly lower than that in the bulk soil, which was not associated with soil pH changes. In contrast, the number of bacteria and the activity of peroxidase, sucrase, urease, and laccase in the rhizosphere were significantly higher. The 16S rDNA sequencing results showed that the bacterial diversity and quantity along with the abundance of Proteobacteria in the rhizosphere were significantly higher than in the bulk soil, while the abundance of Acidobacteria was lower than in the bulk soil. The soil laccase activity and the number of bacteria decreased significantly with the increase in the manganese toxicity stress. Finally, the relative abundance of proteins associated with manganese transportation and oxidation was significantly higher in the rhizosphere soil. In summary, the Mn-induced response of the rhizosphere is an important mechanism in sugarcane adaptation to manganese toxicity in acidic soil.

Global evaluation of key factors influencing nitrogen fertilization efficiency in wheat: a recent meta-analysis (2000-2022).

Improving nitrogen use efficiency (NUE) without compromising yield remains a crucial agroecological challenge in theory and practice. Some meta-analyses conducted in recent years investigated the impact of nitrogen (N) fertilizer on crop yield and gaseous emissions, but most are region-specific and focused on N sources and application methods. However, various factors affecting yield and N fertilizer efficiency in wheat crops on a global scale are not extensively studied, thus highlighting the need for a comprehensive meta-analysis. Using 109 peer-reviewed research studies (published between 2000 and 2022) from 156 experimental sites (covering 36.8, 38.6 and 24.6% of coarse, medium, and fine texture soils, respectively), we conducted a global meta-analysis to elucidate suitable N management practices and the key factors influencing N fertilization efficiency in wheat as a function of yield and recovery efficiency and also explained future perspectives for efficient N management in wheat crop. Overall, N fertilization had a significant impact on wheat yield. A curvilinear relationship was found between N rates and grain yield, whereas maximum yield improvement was illustrated at 150-300 kg N ha-1. In addition, N increased yield by 92.18% under direct soil incorporation, 87.55% under combined chemical and organic fertilizers application, and 72.86% under split application. Site-specific covariates (climatic conditions and soil properties) had a pronounced impact on N fertilization efficiency. A significantly higher yield response was observed in regions with MAP > 800 mm, and where MAT remained < 15 °C. Additionally, the highest yield response was observed with initial AN, AP and AK concentrations at < 20, < 10 and 100-150 mg kg-1, respectively, and yield response considerably declined with increasing these threshold values. Nevertheless, regression analysis revealed a declining trend in N recovery efficiency (REN) and the addition of N in already fertile soils may affect plant uptake and RE. Global REN in wheat remained at 49.78% and followed a negative trend with the further increase of N supply and improvement in soil properties. Finally, an advanced N management approach such as "root zone targeted fertilization" is suggested to reduce fertilizer application rate and save time and labor costs while achieving high yield and NUE.

Arbuscular mycorrhizal fungi improve selenium uptake by modulating root transcriptome of rice (Oryza sativa L.).

Although selenium (Se) is an essential trace element in humans, the intake of Se from food is still generally inadequate throughout the world. Inoculation with arbuscular mycorrhizal fungi (AMF) improves the uptake of Se in rice (Oryza sativa L.). However, the mechanism by which AMF improves the uptake of Se in rice at the transcriptome level is unknown. Only a few studies have evaluated the effects of uptake of other elements in rice under the combined effects of Se and AMF. In this study, Se combined with the AMF Funneliformis mosseae (Fm) increased the biomass and Se concentration of rice plants, altered the pattern of ionomics of the rice roots and shoots, and reduced the antagonistic uptake of Se with nickel, molybdenum, phosphorus, and copper compared with the treatment of Se alone, indicating that Fm can enhance the effect of fertilizers rich in Se. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the hub genes in modules significantly associated with the genes that contained Se and were related to protein phosphorylation, protein serine/threonine kinase activity, membrane translocation, and metal ion binding, suggesting that the uptake of Se by the rice roots may be associated with these genes when Fm and Se act in concert. This study provides a reference for the further exploration of genes related to Se uptake in rice under Fm treatment.

Real-time non-refractory PM1 chemical composition, size distribution and source apportionment at a coastal industrial park in the Yangtze River Delta region, China.

This study present real-time measurements of the chemical composition and particle number size distributions (PNSD) of submicron particulate matter (PM1) in winter at a coastal industrial park in the Yangtze River Delta region of China. Positive matrix factorization (PMF) analysis identified three PNSD factors and three organic aerosol (OA) factors. Contributions and potential source regions of these factors were investigated for four typical periods during the PM1 formation and dissipation process. Results show that the relative contributions from aged 250 nm- factor, fresh 35 nm- and 80 nm- factors were strongly affected by local fresh emissions and regional new particle formation. The non-refractory PM1 measured by Aerodyne aerosol chemical speciation monitor is indicative of the chemical composition of aged 250 nm-factor, but not fresh 35 nm- and 80 nm-factors. The contributions of NO3- and SO42- to NR-PM1 were largely dictated by whether the air mass trajectory went over the sea or the continent. NO3- was abundant (up to 44% of NR-PM1) in cold and dry continental air masses, while SO42- formation (up to 39% of NR-PM1) was preferred in humid and warm marine air masses. Among the three OA source factors, more-oxidized oxygenated OA (MO-OOA) was the most abundant OA factor (44-66% of total OA) throughout the entire field campaign, while an enhanced contribution of 39% from hydrocarbon-like OA (HOA) was observed prior to heavy pollution period. On average, secondary components SO42-, NO3-, NH4+, MO-OOA and less-oxidized oxygenated OA (LO-OOA) contributed 90 ± 7% of NR-PM1, while primary components HOA and Cl- accounted for the remaining 10 ± 7%.

The characteristics and mixing states of PM2.5 during a winter dust storm in Ningbo of the Yangtze River Delta, China.

Dust particulates play an essential role for the nucleation, hygroscopicity and also contribute to aerosol mass. We investigated the chemical composition, size distribution and mixing states of PM2.5 using a single-particle aerosol mass spectrometer (SPAMS), Monitor for AeRosols and Gases (MARGA), and off-line membrane sampling from 2018.1.24 to 2018.2.20 at a coastal supersite in Ningbo, a port city in Yangtze River Delta, China. During the study campaign, the eastern part of China had experienced a wide range of cooling, sandstorm, and snowfall processes. The entire sampling campaign was categorized into five sub-periods based on the levels of PM2.5 and the ratios of PM2.5/PM10, namely clean (T1), heavy pollution (T2), light pollution (T3), dust (sandstorm) (T4) and cleaning pollution (T5) period. After comparing the average mass spectrum for each period, it shows that the primary ions, such as Ca2+and SiO3-, rarely coexist with each other within a single particle, but secondary ions generally coexist with these primary ions. Furthermore, the coexistence of each two different ions within a particle does not show distinct variation for the whole study periods. All these suggest that the absorption and partitioning of gaseous contaminants into the surface of primary aerosol through heterogeneous reactions are the major pathways of aging and growth of aerosol; and the merging of particles through collisions usually is insignificant. Although the absolute concentrations of nitrate and sulfate all increased with the PM2.5 concentrations, the relative equivalent concentrations of NO3- and SO42- displayed opposite trends; the relative contribution of sulfate decreased and that of nitrate increased as the increase of pollution. During the dust period, the relative equivalent concentrations of calcium and/or potassium ions in PM2.5 are significantly higher. This study provided deep insights about the mixing states and characteristics of particulate after long-range transport and a visualization tool for aerosol study.

[Pollution Characteristics and Potential Source Contributions of Gaseous Elemental Mercury (GEM) During Summer and Autumn in Ningbo City].

Gaseous elemental mercury (GEM) is commonly known as a hazardous heavy metal in the atmosphere and is harmful to living organisms. GEM is chemically stable and has a long residence time in the atmosphere; hence, it can be transported over long distances with air masses and is regarded as a global pollutant. We study the transportation and transformation mechanisms of GEM and its potential anthropogenic and natural contribution sources. GEM, conventional atmospheric pollutants, and meteorological parameters were monitored at a coastal site in Ningbo during the summer and autumn of 2017. The results were as follows. ① The concentrations of GEM ranged from 0.97-10.95 ng·m-3 and the mean and standard deviation (SD) were (2.32±0.90) ng·m-3, whereby the mean summer concentration was lower than the mean autumn concentration. ② The diurnal variations of GEM, ozone (O3), and gaseous oxidized mercury (GOM) during summer/autumn and sunny/rainy days suggest that higher levels of O3 and that strong solar radiation accounted for the rapid photochemical oxidation of GEM. The intensity of oxidation on sunny days was higher than that on rainy days. ③ Correlation analysis showed that GEM was significantly positively correlated with PM2.5 (R=0.65, P<0.01), PM10 (R=0.47, P<0.01), NO2 (R=0.46, P<0.01), and CO (R=0.57, P<0.01). Local and regional sources of GEM were mainly related to fossil fuel combustion. ④ The photochemical oxidation rate of GEM was influenced by the concentrations of oxidants (e.g., O3), gas-particle partitioning between GEM and particles, and light extinction effects of PM2.5, water vapor, and NO2. ⑤ Potential source contribution analysis (PSCF) indicated that the northwestern Zhejiang Province (including Ningbo City), the southern Anhui Province, and most of Jiangxi Province constitute a triangular area that is a potential source contribution to NBUEORS atmospheric GEM pollution during the summer. Local, regional, and long-range sources all had strong impacts on GEM pollution. During the autumn, the potential sources were mainly in the northern Zhejiang Province, and the source was smaller than that during the summer. GEM pollution during the autumn was mainly influenced by local and regional sources. Therefore, the control of atmospheric GEM pollution in the Yangtze River delta should apply inter-regional prevention and comprehensive control strategies in order to reduce atmospheric mercury pollution.