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Extreme meteorological events can influence air quality. In March 2021, northern China experienced a severe dust event, leading to widespread air quality deterioration. Using reanalysis datasets and station data, we investigate the synoptic weather patterns, dust transport characteristics, and associated impacts on air quality during this event. The results are as follows. (1) The dust event is closely linked to the Mongolian cyclone, providing favorable conditions for dust emission and long-distance transport. (2) The Gobi Desert in Mongolia is the primary source, with dust particles transported from Mongolia to northern China via the northwesterly flow. Dust transport exhibits a complex three-dimensional structure, with the most intense dust transport at approximately 2500 m altitude. (3) The impact of this dust event on air quality was characterized by its remarkable intensity, extensive spatial coverage, and prolonged duration. Additionally, 58.8% of the stations in northern China experienced pollution, 36.3% of them reached severe pollution levels or higher, and 35.9% of the sites experienced more than 12 h of pollution. (4) The visibility at the northern stations near the dust source rapidly decreases due to solid dust particles. In contrast, the southern stations, with higher moisture content, are primarily affected by liquid particles in terms of visibility. After the frontal passage, wet deposition from the precipitation process gradually improves visibility. [ABSTRACT FROM AUTHOR]

On the 15th of March 2021, the strongest sandstorm in a decade occurred in northern China, and had a great adverse impact on the natural environment and human health in northern China. Real-time monitoring of dust storms is becoming increasingly important. In order to effectively analyze the non-hydrostatic delay (ZNHD) anomaly during a sandstorm, the method based on GNSS-derived tropospheric ZNHD residual to monitor the sandstorm is proposed at the same time. We studied the relationship between ZNHD/PWV and PM10/PM2.5 in Beijing, Changchun, Pingliang and Zhongwei before and after sandstorms. The ZNHD time series was then decomposed by singular spectrum analysis (SSA) and the residuals were obtained. The relationship between the GNSS-derived ZNHD residual and PM10 was analyzed. The results show that the impact of the sandstorm on PM10 is greater than that on PM2.5. Before the sandstorm, the correlation between PM10 and ZNHD was low, less than 0.25. When the sandstorm occurred, the correlation between PM10 and ZNHD increased significantly, and the maximum was greater than 0.7. When the sandstorm ended, the correlation between PM10 and ZNHD decreased significantly. Through the relationship between the ZNHD residual and PM10, it can be found that when the peak-to-peak values of the ZNHD residual are all above 80 mm, sandstorms may occur. But Rainfall, snowfall, haze and other abnormal weather can also lead to ZNHD anomalies. [ABSTRACT FROM AUTHOR]

Severe sandstorms reoccurred in the spring of 2021 after an absence for more than 10 years in North China. The dust source area, located in Mongolia, suffered destructive cooling and warming in early and late winter, which loosened the land. A lack of precipitation, excessive snow melt and strong evaporation resulted in dry soil and exiguous spring vegetation. A super-strong Mongolian cyclone developed on the bare and loose ground, and easily blew and transported large amounts of sand particles into North China. Furthermore, top-ranking anomalies (sea ice shift in the Barents and Kara Sea, and sea surface temperatures in the east Pacific and northwest Atlantic) were found to induce the aforementioned tremendous climate anomalies in the dust source area. Analyses, based on large-ensemble Coupled Model Intercomparison Project Phase 6, yield results identical to the reanalysis data. Thus, the climate variabilities at different latitudes and synoptic disturbances jointly facilitated the strongest spring sandstorm over the last decade. [ABSTRACT FROM AUTHOR]

Mineral dust particles play an important role in the formation of secondary inorganic aerosols, which largely contribute to haze pollution in China. During this study, a haze episode (haze days) and a typical haze process mixed with sandstorm (sandy haze days) were observed in Zhengzhou with a series of high-time-resolution monitoring instruments from November 22 to December 8, 2018. Concentrations of PM 10 and crustal elements clearly increased in the sandy haze days. Concentrations of gaseous pollutants, metallic elements emitted from anthropogenic sources, nitrate, and ammonium during sandy haze days were slightly lower than those during the haze days but still obviously higher than those during the non-haze days. The sulfate concentrations, the sulfate fractions in PM 2.5 , and the sulfur oxidation ratios significantly increased in the sandy haze days. Heterogeneous reactions dominated the conversion of SO 2 during the haze and sandy haze days. Enhanced SO 2 conversion during the sandy haze days may be attributed to the high concentrations of transition metal ions from the sandstorm when the values of relative humidity (RH) were in 30%–70%, and high O 3 at certain time points. Gas-phase NO 2 oxidation reactions were the main pathways for nitrate formation. In the sandy haze days, higher nitrogen oxidation ratio (NOR) at daytime may be associated with higher RH and lower temperature than those in the haze days, which facilitate the gas-to-particle partitioning of nitrate; higher NOR values at night may be attributed to the higher O 3 concentrations, which promoted the formation of N 2 O 5. Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] • The sandstorms presented a trend of decreasing first and then increasing. • The sandstorms mainly occurred in spring (92.4%) and winter (5.6%). • Hot spots of sandstorms were concentrated in the Loess Plateau and desert area. • In the future, sandstorm will become more frequent, in line with past trends. Sandstorm, as a disastrous weather phenomenon, seriously threatens the ecological environment and human health. In this study, the normalized brightness temperature dust index (NBTDI) data set of sandstorms in Yellow River Basin, China during 2000–2021 was constructed. Based on this, the temporal and spatial distribution pattern of sandstorms in the Yellow River Basin in the 21st century was analyzed. The variation trend of NBTDI in the past 22 years was discussed. The results showed that the interannual variation of sandstorms in the 21st century weakened first and then intensified. From the perspective of seasonal variation, sandstorm events occurred most frequently in spring (92.4%), followed by winter (5.6%), and occasionally in summer and autumn. In space, the distribution of sandstorms in the Yellow River Basin had obvious spatial heterogeneity. The central location of the sandstorm in the Yellow River Basin moved slightly to the north, but all of them were concentrated on desert areas. This was caused by the combination of unique geographical location and meteorological factors. The natural climate was closely related to the occurrence of sandstorms. The variation trend of long time-series NBTDI indicated that there were long memories between 22 years of sandstorms. NBTDI had an increasing trend in the long time series. In the future, sandstorms will become more frequent, in line with past trends. This study provides important data support for comprehensive understanding of extreme sandstorm weather, and has important significance for large-scale and long-term monitoring of sandstorm weather. [ABSTRACT FROM AUTHOR]

Air quality has significantly improved in China; however, new challenges emerge when dust weather is combined with haze pollution during spring in northern China. On March 15, 2021, an extremely severe sandstorm occurred in Beijing, with hourly maximum PM 10 and PM 2.5 concentrations reaching 5267.7 μg m−3 and 963.9 μg m−3, respectively. Continuous sandstorm events usually lead to complicated pollution status in spring. Three pollution types were identified disregarding the time sequence throughout March. The secondary formation type was dominant, with high ratios of PM 2.5 /PM 10 (mean 74%) and PM 1 /PM 2.5 (mean 52%). This suggests that secondary transformations are the primary cause of heavy pollution, even during the dry seasons. Sandstorm type resulted in dramatic PM 10 levels, with a noticeable decrease in PM 2.5 /PM 10 levels (27%), although PM 2.5 levels remain high. The transitional pollution type was distinguished by an independent increase in PM 10 levels, although PM 2.5 and PM 1 levels differed from the PM 10 levels. Throughout March, the sulfur oxidation rate varied considerably, with high levels during most periods (mean 0.52). A strong correlation indicated that relative humidity was the primary variable promoting the formation of secondary sulfate. Sandstorms promote heterogeneous reactions by providing abundant reaction surfaces from mineral particles, therefore aggravating secondary pollution. The sandstorm air mass from the northwest passing through the sand sources of Mongolia carried not only crustal matter but also organic components, such as bioaerosols, resulting in a sharp increase in the organic carbon in PM 2.5. [Display omitted] • Three types of air pollution were identified: secondary formation, sandstorm and transitional pollution. • Haze mixed with sandstorms caused more severe air pollution in Beijing. • Air masses from Mongolia with high bioaerosol burden led to increased organic carbon concentrations. [ABSTRACT FROM AUTHOR]

PM2.5 (Particulate Matter 2.5) samples were collected at Mount Heng and analyzed for polycyclic aromatic hydrocarbons (PAHs). During sampling, a sandstorm from northern China struck Mount Heng and resulted in a mean PM2.5 concentration of 150.61 μg/m3, which greatly exceeded the concentration measured under normal conditions (no sandstorm: 58.50 μg/m3). The average mass of PAHs in PM2.5 was 30.70 μg/g, which was much lower than in the non-sandstorm samples (80.80 μg/g). Therefore, the sandstorm increased particle levels but decreased PAH concentrations due to dilution and turbulence. During the sandstorm, the concentrations of 4- and 5-ring PAHs were below their detection limits, and 6-ring PAHs were the most abundant. Under normal conditions, the concentrations of 2-, 3- and 6-ring PAHs were higher, and 4- and 5-ring PAHs were lower relative to the other sampling sites. In general, the PAH contamination was low to medium at Mount Heng. Higher LMW (low molecular weight) concentrations were primarily linked to meteorological conditions, and higher HMW (high molecular weight) concentrations primarily resulted from long-range transport. Analysis of diagnostic ratios indicated that PM2.5 PAHs had been emitted during the combustion of coal, wood or petroleum. The transport characteristics and origins of the PAHs were investigated using backwards Lagrangian particle dispersion modeling. Under normal conditions, the "footprint" retroplumes and potential source contributions of PAHs for the highest and lowest concentrations indicated that local sources had little effect. In contrast, long-range transport played a vital role in the levels of PM2.5 and PAHs in the high-altitude atmosphere. [ABSTRACT FROM AUTHOR]

As an important central city in western China, Xi'an has the worst atmospheric pollution record in China and many measures have been taken to improve the air quality in the past few years. In this study, PM 2.5 samples were collected across four seasons from 2017 to 2018 in Xi'an. Organic carbon and elemental carbon, water soluble ions, and elements were monitored to assess the air quality. The average annual PM 2.5 concentration was (134.9 ± 48.1 μg/m3), with the highest concentration in winter (188.8 ± 93.2 μg/m3), and lowest concentration in summer (71.2 ± 12.1 μg/m3). The secondary generation of sulfate (SO 4 2−) and nitrate (NO 3 −) was strong in spring, and secondary organic carbon (SOC) was formed in all seasons. The compositions of PM 2.5 changed greatly during a sandstorm occurred and the Spring Festival. The sandstorm played a positive role in removing local pollutant NO 3 −, but also increased the concentration of SO 4 2−, however both the concentration of SO 4 2− and NO 3 − greatly increased by secondary generation during Spring Festival. Potential source analysis showed that during the sandstorm, pollutants were transported over a long distance from the northwest of China, whereas it was mainly from the local and surrounded emissions during the Spring Festival. Except Ca2+ and geological dust (GM), the other components in PM 2.5 increased significantly on the day of the Spring Festival. During sampling time in Xi'an, the positive matrix factorization (PMF) model analysis showed that PM 2.5 mainly came from vehicle emission, coal combustion, and biomass burning. • The average annual PM 2.5 concentration in Xi'an has increased from 2004 to 2007, and gradually decreased from 2012 to 2018. • It has higher exposure levels in wintertime in Xi'an, especially during the pollution events with seasonal variations. • NO 3 – decreased and SO 4 2– increased during the sandstorm, whereas both SO 4 2– and NO 3 – increased during the Spring Festival. • As one of the three main sources for PM 2.5 in Xi'an, the contribution of vehicle emission has elevated in the past years. [ABSTRACT FROM AUTHOR]

The article presents a study that investigates on the importance of runoff water in the management of vegetation patches in China. The study was administered by coupling a plant growth model in accordance to a simple GIS-based model of water redistribution and use wherein the interaction of runoff generation on plant and grassland are analyzed. The study reveals that runoffs can be used to increase net primary productivity (NPP) and biomass level to reduce wind erosion and enhance the capacity of system to retarded degradation. In addition, the author notes that the coupled model of plants can be used as a tool to address the effects of water redistribution on land management as well as protect the environment.

A study of sandstorms in the Loess Plateau and neighbouring areas is based on observations of sandstorms and precipitation. Through analysis of the relationship between the mean annual number of sandstorms and the mean annual precipitation, an original sandstorm zone and a secondary high-frequency zone of sandstorms have been defined. The latter is mainly formed as a result of human activities, such as vegetation destruction and waste-land cultivation, and not because of climatic change. The secondary sandstorm zone is located 350–500 km away from the original sandstorm zone, reflecting the fact that the sandstorm zone in the Loess Plateau area has shifted 350–500 km to the southeast, in response to human impact. Some abrupt change has been found in the area where the mean annual precipitation is 270 mm, where the original sandstorm zone ends and a secondary zone of high-frequency sandstorms begins. This transition area can be regarded as an abnormally unstable area. This study shows that destruction of the vegetation can cause changes in the environment similar to those attributed to climatic change. [ABSTRACT FROM AUTHOR]

The purpose of this present study is to investigate the frequency and variation of sandstorm in Minqin Oasis. Using daily observational data of sandstorm and other meteorologic data from 1954 to 2000, we have illuminated the relationship between sandstorm, meteorological parameters and human activities. The results of the analysis show that the highest frequency of sandstorms occurrence and their duration mainly focus on March, April and May, especially in April. Most of sandstorms occur from midday to nightfall, but relative few appear from midnight to forenoon, which apparently correlates to the daily variations of atmospheric thermal stability within atmospheric boundary layer. Monthly mean and annual mean duration of sandstorms coincide well with the frequencies of sandstorm occurrence. [ABSTRACT FROM AUTHOR]