环境科学最新文献

Agricultural greenhouse gas emission reduction plays an important role in addressing global climate warming. Researching and revealing the spatial and temporal characteristics, as well as the influencing mechanisms of agricultural greenhouse gas emissions, is of great significance for achieving the goals of green and low-carbon development in agriculture. This study examines the agricultural greenhouse gas emissions from 31 provinces （municipalities, autonomous regions） in China from 2000 to 2020. Through the use of geographic detectors, spatial econometric analysis, and other methods, it explores the spatiotemporal evolution characteristics and driving factors of agricultural greenhouse gas emissions. The results indicated the following： ① From 2000 to 2020, agricultural greenhouse gas emissions in China showed a development process of "slow increase - sharp increase - sharp decrease." ② The spatial heterogeneity of agricultural greenhouse gas emissions was significant, forming three high emission areas in space： the central high emission area centered on Henan, the southern high emission area centered on Guangdong, and the southwestern high emission area centered on Sichuan. The center of gravity showed a trend of shifting northward and westward. ③ Rural population, regional gross domestic product, and agricultural output value were the dominant driving factors causing spatial heterogeneity of agricultural greenhouse gas emissions. ④ Agricultural greenhouse gas emissions had spatial spillover effects. When formulating agricultural greenhouse gas reduction targets, it is necessary to adopt a coordinated control strategy among different regions.

Conducting the screening and replanting of crops with low accumulation of heavy metals can effectively reduce the risk of heavy metal accumulation in agricultural products. However, current research focuses more on the screening of crops with low accumulation of a single heavy metal. Target crops also focus more on single-type crops and varieties. Research on the accumulation differences in arsenic and cadmium in different crop types and the priority recommendation list for the planting of low-accumulation crops is limited. This study used a combination of literature data meta-analysis and field survey methods to conduct the relevant work. The results showed that the range of arsenic and cadmium content in rice grains was 0.11-0.624 mg·kg^-1 and 0.01-1.935 mg·kg^-1, respectively. Under the same pollution level, rice had a relatively higher risk of accumulating arsenic and cadmium than that in maize and leafy vegetables, fruit vegetables, and root and tuber vegetables. Some leafy vegetables had significantly higher arsenic and cadmium levels, and the difference in arsenic and cadmium accumulation ability between varieties of leafy vegetables was greater than that of other types of crops. The risk of arsenic and cadmium accumulation in the edible parts of maize, fruit vegetables, and root and tuber vegetables after replacing rice cultivation was more significant. Based on the above results, a priority recommendation list for the planting of low-accumulation crops based on pollution level was constructed. Field survey results showed that the list was reasonable to a certain extent. The relevant results of this study can provide effective reference for the optimization of crop type or variety selection and safe production in arsenic and cadmium-polluted soils.

In order to find out the influencing factors of soil selenium （Se） and bioavailability of Se, 1985 soil samples and 120 sets of crop and root soil samples were collected in the hinterland of the Hetao Plain, and the characteristics of soil Se, different forms of Se, and crop Se and heavy metal content were analyzed. The results showed that approximately 5.59% of soil samples exceeded the risk screening values for soil contamination of agricultural land of GB15618-2018 standard, but the heavy metal content in crops was much lower than the standard value, suggesting that the overall risk of heavy metal pollution was low. Se had significant autocorrelation in soil and appeared enriched locally, which were mainly related to natural factors. The content of different forms of Se in root soil was ranked as： residue state > humic acid state > water soluble state ≈ strong organic state > carbonate state > ion exchange state > iron and manganese oxidation state, this result showed that the characteristics of Se in root soil were high availability state, high potential availability state, and low unavailability state compared with those of most areas in China. At the same time, the results showed that water-soluble, ion exchange, and carbonate Se of root soil were significantly correlated with Se of crops,indicating that they were effective forms that could be absorbed and utilized by plants. According to the Se content and bioconcentration factor, different crops were ranked as： white melon seeds > sunflowers > corn. By means of cluster analysis and correlation analysis, the factors affecting the total Se and bioavailability of Se in soil were studied. It was concluded that soil texture, organic matter, and pH had opposite effects on Se and bioavailability of Se in soil. Factors such as clay soil, high organic matter, and low pH degree could promote the accumulation of Se in soil but also limited the activity of available Se. Based on crop and root soil sample data, the soil Se enrichment threshold was discussed. The results demonstrated that using "ω（total Se）≥0.222 mg·kg^-1" as the threshold, the proportion of soil Se enrichment was closer to the Se enrichment level of crops than others.

In-depth study of the spatiotemporal evolution characteristics of ecosystem service supply and demand and their multi-scale spatial matching patterns is crucial to achieving effective management of ecosystem services and formulating scientific ecological protection plans. Investigating the Hubei Province as a research region, this study employed diverse ecological models, such as InVEST, based on multiple data sources encompassing land use, meteorological conditions, and socio-economic factors. The objective was to quantitatively assess and spatially characterize the supply and demand dynamics of four ecosystem services-namely, carbon storage, water yield, soil conservation, and food provision-within the Hubei Province. A comprehensive analysis was conducted on the spatiotemporal evolution characteristics of ecosystem service supply and demand, as well as the supply-demand ratio of ecosystem services at different scales, from 2000 to 2020. The bivariate Moran's I module in GeoDa was used to further explore the changes in the spatial matching patterns of four ecosystem services supply and demand between 2000 and 2020, as well as the differences in the spatial matching patterns of four ecosystem services supply and demand at different scales in 2020. The research results indicated that： ① Between 2000 and 2020, the total supply of the four ecosystem services in Hubei Province exhibited an overall increasing trend. Regarding total demand, all services, except for food supply, showed a growing trend. Except for soil conservation services, the other three services were in a state of oversupply. ② Except for soil conservation services, the other three services exhibited a polarized pattern with lower urban-rural supply-demand ratios and higher non-urban-rural supply-demand ratios. This pattern deepened progressively over the study period. ③ Significant regional variations were observed in the spatial matching of supply and demand for the four ecosystem services. ④ There were notable differences in the balance and matching of ecosystem service supply and demand at different scales. The research results can provide scientific basis for promoting the optimization of the supply and demand pattern of ecosystem services in Hubei Province and formulating more accurate and detailed ecological protection plans, promoting sustainable development in Hubei Province.

A pot experiment was conducted to investigate the growth response, concentration, and transportation characteristics of Cd and Pb in Sedum aizoon L. in four typical Cd/Pb-contaminated soils from northern and southern China with the addition of different levels of water-soluble chitosan （WSC）. The effect of WSC on physicochemical properties, Cd and Pb forms, and functional groups in contaminated soils was determined to clarify the internal mechanism of WSC promoting Cd and Pb accumulation by S. aizoon. The results showed that WSC improved the physicochemical properties of rhizosphere soil by increasing alkaline nitrogen and organic matter contents and significantly reducing pH values. In addition, WSC significantly increased the acid-extractable Cd and Pb in contaminated soils by 16.3%-34.5% and 88.9%-272.4%, respectively. Fourier transform infrared spectra analysis showed that amino （-NH₂） and hydroxyl （-OH） groups in soils were significantly increased by adding WSC. Therefore, the coordination of Cd/Pb with -NH₂ and -OH may play important roles in forming complexes and mobilizing Cd/Pb in soils. Moreover, the improvement in the rhizosphere environment of contaminated soils by WSC contributed to promoting Cd and Pb accumulation by S. aizoon. WSC significantly increased the total Cd and Pb accumulation by 14.5%-72.1% and 55.0%-128.5%, respectively, without obvious growth inhibition. Therefore, it is feasible to apply WSC to promote Cd/Pb accumulation using S. aizoon, while the matching of WSC addition amount, soil pollution condition, and plant materials should be further considered in practical application.

Excessive nitrogen fertilizer application is the main driving force threatening soil health and reducing multiple soil functions. The enhanced-efficiency nitrogen fertilizers （EENFs）, such as urease inhibitors （NBPT）, nitrification inhibitors （DCD）, and coated controlled-release urea （RCN）, have been proven to be effective measures for reducing nitrogen fertilizer application. However, the effects of EENFs on soil quality （SQI）, microbial metabolic characteristics, and soil ecosystem multifunctionality （EMF） and their internal relationships are still unclear. Therefore, based on the field positioning experiment started in 2019 by Pengyang Experimental Station of Guyuan City, Ningxia Hui Autonomous Region, we studied the effects of different fertilization strategies （no nitrogen fertilizer （N0）, mineral nitrogen fertilizer （N200）, DCD, NBPT, and RCN） on SQI, soil enzyme stoichiometry, and EMF under white plastic film mulching. The results revealed that： ① Compared with that under N0, N200 and EENFs increased soil total nitrogen （TN）, microbial biomass carbon （MBC）, and microbial biomass nitrogen （MBN） contents. Compared to the SQI of N0 and N200, that of NBPT and DCD significantly increased by 59.97%-104.78% and 43.28%-83.42%, respectively, while RCN showed no significant change. ②EENFs can alleviate microbial carbon and nitrogen limitations better than N200 and increase soil EMF by 21.97% -51.53%. ③ The MBC, MBN, available nitrogen （AN）, available phosphorus （AP）, and water content （SWC） of soil factors were the common main factors affecting microbial C limitation, N limitation, and soil EMF. Moreover, the improvement in soil quality and alleviating microbial C and N limitation were conducive to improving soil EMF. Overall, the NBPT and DCD application under white plastic film mulching can achieve a win-win situation of soil health and EMF in the short term, which can provide references for optimizing local fertilization management measures.

To elucidate the pollution characteristics and sources of heavy metals in the soil of drinking water sources in urban areas of the Yellow River Basin, the soil in the water source areas for urban drinking water in the Lanzhou section of the Yellow River was selected as the research object. The content characteristics of heavy metals, including As, Cd, Cr, Hg, and Pb, were analyzed. The pollution degree of heavy metals was quantified systematically using the geo-accumulation index, contamination factor, pollution load index, and improved Nemerow comprehensive pollution index. Correlation-clustering analysis, the positive matrix factorization （PMF） model, and the absolute principal component scores-multiple linear regression （APCS-MLR） model were jointly applied to quantitatively analyze the pollution sources and their contribution rates of heavy metals. The results indicated that： ① The soil in the water source areas for urban drinking water in Lanzhou was alkaline, and, with the exception of Cr, the average content of heavy metals in the soil, including As, Cd, Hg, and Pb, exceeded the background values of soil in Gansu Province. Particularly, Hg and Pb exhibited significant spatial distribution variations, indicative of strong anthropogenic influences. ② The overall pollution level of the water source area soil was mild, with Hg identified as the primary pollutant and localized pollution observed for As and Pb, whereas Cd and Cr showed no substantial contamination. ③ The enrichment of heavy metals in the water source area soil was influenced by a combination of industrial, traffic, coal combustion, and natural sources. The PMF model identified 41.40% as industrial-traffic sources, 32.92% as coal combustion sources, and 25.68% as natural-industrial sources. The APCS-MLR model distinguished 36.36% as industrial-traffic sources, 22.32% as coal-industrial sources, and 41.31% as natural sources. These findings provide a scientific basis for ensuring the health of soil in the water source areas and the safety of drinking water in the urban area of Lanzhou.

As a new environmental pollutant, the widespread existence of antibiotic resistance genes （ARGs） has brought about a series of environmental and human health problems. Livestock manure is considered to be an important repository of ARGs, and its resource utilization has potential environmental risks. Soil-vegetable systems are the core link in agricultural production, and it is also an important way for humans to communicate with the environment. The utilization of livestock and poultry manure in agricultural production leads to the proliferation and spread of ARGs in soil-vegetable systems. ARGs in soil-vegetable systems may be ingested by humans through the food chain and pose a threat to human health. Therefore, on the basis of briefly discussing the sources and hazards of ARGs in the soil-vegetable system, this study focused on the environmental behavior of ARGs in the soil-vegetable system； summarized the occurrence characteristics, migration rules, and key influencing factors of ARGs in the soil-vegetable system； and put forward suggestions and prospects suitable for the prevention and control of ARGs pollution in the soil-vegetable system in order to provide theoretical support for China's agricultural green development.

Due to the expansion of artificial oases in these areas, scientific assessment of the carbon emission and eco-environment effects caused by changes in agriculture, towns, and ecological space is of great significance in grasping the carbon emission characteristics of various land use types, formulating land use emission reduction strategies, promoting the construction of ecological civilization, and optimizing the spatial pattern of the national territory. Based on land use data and socio-economic data, taking the inland river basin of the arid zone of the Xinjiang-Aksu River Basin as the research object, the carbon emission coefficient method was used to measure land-use carbon emissions, and spatial autocorrelation analysis and standard deviation ellipse were used to analyze the spatial evolution characteristics of carbon emissions from agriculture-town-ecological space in the Aksu River Basin. Based on the eco-environment quality index and ecological contribution rate, the impact of the agriculture-town-ecological space transformation on the eco-environment effects in the Aksu River Basin was explored. The results showed that： ① The scale of agricultural space and town space continued to rise, while the overall scale of ecological space was shrinking. The carbon source provided by agricultural space and town space showed a continuous upward trend, while the carbon sink provided by ecological space showed a trend of first increasing and then decreasing, with an overall downward trend. ② There was a positive spatial correlation between the net carbon emissions and the carbon emissions provided by the agriculture-town-ecological space. The center of gravity of carbon emissions in the basin generally moved to the southwest except for the ecological space, whereas the other space and net carbon emissions moved to the southeast. ③ The eco-environment quality index in the basin increased first and then decreased and generally showed a downward trend. From 1990 to 2000, the ecological environment quality improved overall； from 2000 to 2010, it deteriorated severely； and from 2010 to 2020, it deteriorated slowly.

Microplastics （MPs）, an emerging contaminant, have been widely detected in environmental media including water, sediment, soil, and atmosphere. Exploring the occurrence and transport characteristics of MPs in different environments is essential for accurately evaluating its ecological and environmental effects. However, the extent to which a free water surface （FWS） constructed wetland alters the occurrence characteristics of MPs in water has not been clearly elucidated. Therefore, five FWS constructed wetlands in the Luoshijiang Watershed located in the upper reaches of the Erhai Lake were selected as the research objects. The effects of these FWS constructed wetlands on MPs characteristics in water bodies were explored based on their abundance, shape, particle size, and polymer type in the wetland inlet and outlet. The results showed that： ① The quantity and mass abundance of MPs in the water of the FWS constructed wetland in the Luoshijiang Watershed were in the range of 10 375-21 000 n·m^-3 and 5.5-9.8mg·m^-3, and the corresponding average abundances were （14 115±2 790） n·m^-3 and （7.6±2.3）mg·m^-3, respectively. MPs with small particle size （0.2-1 mm, 73.8%±7.5%）, transparent color （64.0%±12.2%）, and fiber shape （98.9%±1.7%） were dominant in water bodies of the FWS constructed wetland, while cellophane （CP, 58.5%±13.9%）, polyethylene terephthalate （PET, 22.1%±11.4%）, and polyester （PES, 12.8%±16.8%） were the main polymer types. The MPs abundance in the water of FWS constructed wetland in this watershed was relatively high, whereas the pollution load index and ecological risk index were both in low levels （Level I）. ② After water flowing through the FWS constructed wetland, the film- and fragment-shaped MPs disappeared, and the proportions of dominant color （transparent, black, and white） and polymer type （PET） decreased by 1.4% and 4.1%, respectively. By contrast, the proportions of large size and minority-color （red, yellow, green, purple, etc.） MPs increased, with 1-2 mm, 2-5 mm, and minority-color increasing by 3.0%, 2.2%, and 5.4%, respectively, and polymer types of rayon and PES, which did not exist in the wetland inlet, were detected. ③ The quantity and mass abundance of MPs differences between the inlet and outlet of the FWS constructed wetland in the Luoshijiang Watershed were both insignificant （P>0.05）, and the retention of MPs in water bodies by the FWS constructed wetland was also insignificant. However, the FWS constructed wetland weakened the correlations among different MPs characteristics in water bodies. The results indicated that the FWS constructed wetland could alter the occurrence characteristics of MPs in water bodies, including particle size, shape, color, and polymer type, and exhibited the dual roles of source and sink of MPs.