Influence of meteorological and ambient air quality factors on Artemisia pollen counts in Urumqi, Northwest China.

The exposure of Artemisia pollen in the air to humans causes adverse allergenic effects on the respiratory system. However, the relationship between Artemisia pollen counts and meteorological and air quality factors in the arid and semiarid cities of northwest China has not attracted significant attention. Here, we observed the seasonal pollen counts of Artemisia, as well as the main meteorological variables (temperature/T, relative humidity/RH, and wind speed/WS, and ambient air quality factors (PM2.5, PM10, and CO2). This was conducted from May to September 2021 at three sampling sites in Urumqi, Xinjiang. The results showed that Artemisia pollen counts gradually increased from May (121 grains/1000 mm2) to August (563 grains/1000 mm2) and decreased till the end of the sampling period in September (247 grains/1000 mm2). Pearson correlation analysis revealed a significant positive correlation between the variation in Artemisia pollen counts and PM2.5 (R = 0.545, P < 0.01), the average temperature (R = 0.424, P < 0.05), and PM10 (R = 0.466, P < 0.05). Oppositely, a significant negative correlation was observed between the RH (R = 0.503, P < 0.01) and WS (R = 0.653, P < 0.01). Variation partitioning analysis showed that meteorological factors contributed the highest (44 %) to the variation in pollen counts. The study results provide basic information for future case studies on allergenic plant pollen in Urumqi and serve as a reference for the development of sustainable healthy cities in arid regions.

Evaluating the capacity of heavy metal pollution enrichment in green vegetation in the industrial zone, Northwest China.

It focused on heavy metal pollution of green vegetation in Tuokexun County, Xinjiang Northwest China's suburban industrial area, using inductively coupled plasma emission spectrometer to analyze the samples for Mn, Ni, Zn, Cd, Hg, Pb, As, Cu, and Cr contents. The soil's heavy metal content in the study area indicated a minor level of pollution overall (P = 1.77), with the most severe contamination being Hg, which is more likely to be caused by human activities. Heavy metal elements in trees have the most stable composition in comparison to grass and shrubs, with varying concentrations across different vegetation. The concentrations of Mn, Cd and Hg were highest in the Haloxylon ammodendron, Ni in Morus alba, Pb, As and Cu in Nitraria tangutorums, and Cr in Phragmites australis. Heavy metal restoration is most effectively performed by shrubs, and there are disparities in heavy metal enrichment among various vegetation. No significant difference was found in heavy metal enrichment between the aboveground and underground parts of vegetation. Based on the average of the membership function, Tamarix exhibits the strongest ability to enrich heavy metals, while Nitraria tangutorum comes in second, and Cynanchum chinense R.Br. is the least effective among all plant species. Morus alba is recommended as the primary planting species in the area. Nitraria tangutorum and Haloxylon ammodendron have good potential for Cd and As restoration and can be used as supporting vegetation.

Assessment of air quality before and during the COVID-19 and its potential health impacts in an arid oasis city: Urumqi, China.

As a key node city of the "Silk Road Economic Belt" Urumqi has been listed as one of the ten most polluted cities in the world, posing a serious threat to the urban environment and residents' health. This study analyzed the air quality before and during the COVID-19 (Coronavirus disease 2019) pandemic and its potential health effects based on the data of PM2.5, PM10, SO2, NO2, CO, and O3_8h levels from 10 air quality monitoring stations in Urumqi from January 1, 2017, to December 31, 2021. As per the results, the concentrations of the air pollutants PM2.5, PM10, SO2, NO2, CO, and O3_8h in Urumqi from 2017 to 2021 showed a cyclical trend, and the implementation of COVID-19 prevention and control measures could effectively reduce the concentration(ρ) of air pollutants. The mean value of ρ(PM2.5) decreased from 2017 to 2021, whereas ρ(O3_8h) showed a waveform change trend (increased in 2017-2018, decreased in 2018-2020, and increased after 2020). Meanwhile, the maximum annual average values of ρ(PM2.5) and ρ(O3_8h) for the six monitoring stations during 2017-2021 occurred at sites S2 (74.37 µg m-3) and S6 (91.80 µg m-3), respectively; rapid industrialization had a greater impact on PM2.5 and O3_8h concentrations compared to commercial and residential areas. In addition, the air quality index data series can characterize the fluctuation trend of PM2.5. The high pollution levels (Class IV and V) of the air pollutants PM2.5 and O3_8h in Urumqi have been decreasing annually, and good days can account for 80-95% of the total number of days in the year, indicating that the number of days with a potential threat to residents' health is gradually decreasing. Therefore, more attention should be paid in controlling and managing air pollution in Urumqi.

Population Structure and Spatial Distribution Pattern of Populus euphratica Riparian Forest Under Environmental Heterogeneity Along the Tarim River, Northwest China.

Populus euphratica Oliv. (Euphrates poplar), as the dominant tree species of desert riparian forests along the Central Asian inland rivers, plays a critical role in protecting arid land ecosystems. In recent decades, climate change and excessive water resources utilization activities have led to the environmental degradation of desert riparian forests along the Tarim River in northwest China. Understanding the forest stand structure and spatial distribution pattern provide important guidance for monitoring forest dynamics in support of sustainable management. However, few studies have examined how riparian forests stand attributes differ in response to environmental heterogeneity. In this study, terrestrial laser scanning (TLS) was applied to acquire a total of 1648 individual P. euphratica tree's 3D structure attributes within 18 plots along the upper, middle, and lower reaches of the Tarim River, which included tree height (TH), diameter at breast height (DBH), crown diameter (CD), crown projection area (CPA), stand density index (SDI), age structure ratios, and spatial pattern. The results showed that the average tree segmentation and structure determination accuracies of TLS were 93.2 and 94.6%. From the upper to the lower reaches, the average TH and CD decreased by 3.8 and 0.3 m, while the DBH increased by 4.2 cm. The SDI and CPA exhibited the following order: upper reaches (454 n ha-1, 82.3%) > middle reaches (382 n ha-1, 67.3%) > lower reaches (263 n ha-1, 39.1%), the differences were significant at 0.05 level. The population age structure changed from growing population in the upper reaches to stable population in the middle and a temporarily stable population in the lower reaches. The pair correlation g(r) function determined random distribution pattern in the upper reaches [g(r) = 1.2], an aggregated pattern in the middle [g(r) = 3.1], and lower reaches [g(r) = 9.7]. The decline in groundwater depth and soil moisture increased aggregated distribution pattern (R = 0.67 and 0.56, P < 0.05) of the P. euphratica along the mainstream of Tarim River. The results enrich our understanding of the current development stage of P. euphratica, which is important for optimizing management strategies and realizing the sustainability of floodplain ecosystems.

Identifying mismatches of ecosystem services supply and demand under semi-arid conditions: The case of the Oasis City Urumqi, China.

Understanding the balance between supply and demand of ecosystem services (ESs) is helpful for sustainable urban management. However, the interactions among multiple ESs supplies and demands remain under-researched, and ESs supply and demand spatial heterogeneity and correlation characteristics at the city level are rarely studied, especially in arid areas. To fill this gap, we established a comprehensive assessment framework of ESs supply and demand through integrating multi-source remote sensing data, social economy, and policy objectives, for the oasis city of Urumqi, China. The ESs supply-demand mismatches were revealed at the city level, and the spatial relationship between the ESs supply and demand was analyzed using spatial statistics. The results demonstrated that: (1) The total quantity of supply and demand of food provision, carbon sequestration, PM10 removal, and recreation services in Urumqi revealed that the demand was greater than the supply, the deficits being 16.10 × 107 kcal/ha, 6.88 × 104 t/ha, 155.86 kg/ha, and 697.26, respectively. (2) The supply and demand assessment of ESs revealed spatial differences from the city center to the suburbs, which further indicated that there are neighborhood similarities between the supply and demand of ESs. (3) The matching types of ESs supply and demand present obvious spatial heterogeneity, which can be divided into four types: High-high, high-low, low-high, and low-low. Owing to rapid urban development in the inner city, the city center is dominated by low-high, whereas the urban-rural ecotone is characterized by high-low, owing to the higher elevation and water resource advantages in the suburbs. Based on the analysis of the supply, demand, and matching of ESs, economic development and sustainable management policies are proposed for different ecological spaces. Integr Environ Assess Manag 2021;17:1293-1304. © 2021 SETAC.

Spatio-temporal variation of ecosystem services value in the Northern Tianshan Mountain Economic zone from 1980 to 2030.

Rapid agricultural land expansion and urbanization have accelerated land use and land cover changes (LUCC) in the Northern Tianshan Mountain Economic Zone and have significantly impacted on the ecosystem services (ESs). However, the spatiotemporal variations of ecosystem service value (ESV) to LUCC are not well understood. Based on the land use and land cover (LULC) data from 1980 to 2019, we used a CA-Markov model to predict LUCC in 2020 and 2030, assess the spatial-temporal changes of ESV and LULC during 1980-2030, and explore the elastic response of ESV to LUCC. We found that cropland and built-up land expanded rapidly by 34.38% and 196.66%, respectively between 1980 and 2030, while grassland and unutilized land decreased significantly by 11.45% and 10.26%, respectively. The ESV of water body, cropland, grassland and forestland accounts for more than 90% of the total ESV. Our research shows that the ESV of cropland increased 32 million yuan from 1980 to 2030, mainly due to the expansion of cropland area. However, the loss caused by the reduction of grassland area was 45 million yuan. Water conservation, waste treatment, soil formation and retention, and biodiversity conservation are the primary ecosystem service function, accounting for 71.82% of the total ESV. Despite notable increases in the ESV from 1980 to 2010, grassland degradation still remains a main ecological and environmental issue from 2010 to 2030. The results suggest that effective land use policies should be developed to control the expansion of croplands and protect water body, grassland and forestland to maintain more sustainable ESs.

Correction: Ecological effect of the riparian ecosystem in the lower reaches of the Tarim River in northwest China.

[This corrects the article DOI: 10.1371/journal.pone.0208462.].

Ecological effect of the riparian ecosystem in the lower reaches of the Tarim River in northwest China.

The riparian vegetation in the lower reaches of the Tarim River is an irreplaceable natural resource for its ecosystem, and also a guarantee for the transportation safety in this area. Here, we analyzed different plant influences on soil erosion and evaluate the main ecosystem service functions served by the riparian vegetation to study area. Results showed that the total amount of sand-fixation in the study area was 4.14×1013 t and that Tamarix chinensis had a greater influence on wind speed and sediment transport than Populus euphratica, and the Tamarix chinensis can be used as suitable vegetation for wind erosion measures and provide scientific basis for the optimization of vegetation matching and reasonable allocation scheme for ecological construction in arid areas. The total ecosystem service value was calculated to be $11.03×1011. Of the main ecosystem service functions, riparian vegetation primarily served as sand fixation. Results show that, this research was identical, and the construction of shelterbelt plays an important role in the promotion of wind and sand control measures. Finally, our findings highlights the need for further research on how vegetation function as windbreak and sand fixation.

[Ecology-economy harmonious development based on the ecological services value change in Yanqi Basin, Northwest China].

In this paper, we used land use/cover ecosystem service value estimation model and ecological economic coordination degree model to analyze the changes of the ecosystem service value by the land use/cover changes during 1985, 1990, 1996, 2000, 2005 and 2011 in Yanqi Basin, Xin-jiang. Then we evaluated the ecology-economy harmony and the regional differences. The results showed that during 1985-2011, there was an increasing trend in the areas of waters, wetland, sand, cultivated land and construction land in Yanqi Basin. In contrast, that of the saline-alkali land, grassland and woodland areas exhibited a decreasing trend. The ecosystem service value in Yanqi Basin during this period presented an increasing trend, among which the waters and cultivated land contributed most to the total value of ecosystem services, while the grassland and the woodland had obviously declined contribution to the total value of ecosystem services. The research showed that the development of ecological economy in the study area was at a low conflict and low coordination level. So, taking reasonable and effective use of the regional waters and soil resources is the key element to maintain the ecosystem service function and sustainable and harmonious development of economy in Yanqi Basin.

Extracellular polymeric substances buffer against the biocidal effect of H2O2 on the bloom-forming cyanobacterium Microcystis aeruginosa.

H2O2 is an emerging biocide for bloom-forming cyanobacteria. It is important to investigate the H2O2 scavenging ability of extracellular polymeric substances (EPS) of cyanobacteria because EPS with strong antioxidant activity may "waste" considerable amounts of H2O2 before it kills the cells. In this study, the buffering capacity against H2O2 of EPS from the bloom-forming cyanobacterium Microcystis aeruginosa was investigated. IC50 values for the ability of EPS and vitamin C (VC) to scavenge 50% of the initial H2O2 concentration were 0.097 and 0.28 mg mL(-1), respectively, indicating the higher H2O2 scavenging activity of EPS than VC. Both proteins and polysaccharides are significantly decomposed by H2O2 and the polysaccharides were more readily decomposed than proteins. H2O2 consumed by the EPS accounted for 50% of the total amount of H2O2 consumed by the cells. Cell growth and photosynthesis were reduced more for EPS-free cells than EPS coated cells when the cells were treated with 0.1 or 0.2 mg mL(-1) H2O2, and the maximum photochemical efficiency Fv/Fm of EPS coated cells recovered to higher values than EPS-free cells. Concentrations of H2O2 above 0.3 mg mL(-1) completely inhibited photosynthesis and no recovery was observed for both EPS-free and EPS coated cells. This shows that EPS has some buffering capacity against the killing effect of H2O2 on cyanobacterial cells. Such a strong H2O2 scavenging ability of EPS is not favorable for killing bloom-forming cyanobacteria. The high H2O2 scavenging capacity means considerable amounts of H2O2 have to be used to break through the EPS barrier before H2O2 exerts any killing effects on the cells. It is therefore necessary to determine the H2O2 scavenging capacity of the EPS of various bloom-forming cyanobacteria so that the cost-effective amount of H2O2 needed to be used for killing the cyanobacteria can be estimated.