Huanjing Kexue/Environmental Science最新文献

Meteorological factors and anthropogenic activities significantly affect atmospheric ammonia （NH₃） concentration and its dry deposition. Former studies have examined the spatial and temporal variability in atmospheric NH₃ concentrations at monthly scales. However, the characteristics of atmospheric concentrations at finer time scales such as hourly and daily scales and the influencing factors remain unclear. In this study, atmospheric NH₃ concentration and related meteorological factors were continuously monitored online for one year in a double cropping rice region in subtropical China, and atmospheric NH₃ concentration and its meteorological influencing factors as well as dry deposition were analyzed at different time scales （hourly, daily, and monthly）. The main results were as follows： The annual average daily concentration of NH₃ in the rice area varied from 0.01 to 58.0 μg·m^-3 （in N, same below）, and the annual average concentration was 5.3 μg·m^-3. On the hourly scale, the 24-hour dynamics of atmospheric NH₃ concentration showed a unimodal pattern, and the time of the NH₃ peak appearance in different seasons was different； the time of the peak that appeared in winter lagged behind that in the other seasons. From the perspective of daily scale, NH₃ concentration was mainly affected by fertilization in the paddy fields, peaking at 1-3 days after fertilization and then gradually decreasing. On the monthly scale, NH₃ concentration peaked at 12.8 μg·m^-3 in July and was the lowest in October at 1.6 μg·m^-3. On the hourly scale, NH₃ concentration varied seasonally due to the influences of meteorological factors, mainly as follows： NH₃ concentration showed significant positive correlations with air temperature and solar radiation in all four seasons and with wind speed in spring and summer, whereas it showed significant negative correlations with relative humidity except in winter. On the daily scale, NH₃ concentration showed a significant positive correlation with air temperature, rainfall, and solar radiation, whereas it showed a significant negative correlation with relative humidity. On the monthly scale, no significant correlation existed between each meteorological factor and NH₃ concentration. The annual dry deposition flux （in N） calculated from the hourly average NH₃ concentration was 8.5 kg·（hm²·a）^-1, which was 11.6% higher than the annual flux calculated from the daily average and 12.4% higher than the annual flux calculated from the monthly average. In summary, there were significant daily and seasonal variations in atmospheric NH₃ concentration in the paddy rice region in subtropical China, and conducting hourly-scale observations of NH₃ concentration can help to reveal the multi-time scale va

In this study, the modified equivalent factor method was applied to account for the long time series ecosystem service value （ESV） of the Yihe River Basin from 1975 to 2020 in the context of land use change, and the cold hot spot analysis and topographic position analysis methods were introduced to explore the characteristics of its spatial pattern. The results showed that： ① From 1975 to 2020, the land use type of the Yihe River Basin was dominated by arable land, and the land use changes were characterized by the rapid decrease of arable land and the continuous expansion of construction land, a slight increase in the area of forest land and grassland, a contraction of the water body area, and little change in the area of unused land. ② The modified equivalent factor method was more suitable for accounting for the ESV in the basin. From 1975 to 2020, the overall ESV of the basin showed an upward spiral trend （33.369-33.816 billion CNY）, dominated by the regulating services. The ESV of arable land was the highest with a decreasing trend, whereas the ESV of unused land was the lowest. ③ In the horizontal spatial pattern, the hot spot of ESV was near mountains and reservoirs, and the cold spot of ESV was near urban areas. In terms of vertical spatial patterns, with growing topographic gradient, vertical changes in ESV for all land use types showed an increasing trend followed by a decreasing trend. The results of the study revealed the spatial and temporal patterns of ecosystem service values in the Yihe River Basin in the context of land use change and provide a scientific basis for optimizing the land use structure and spatial pattern and enhancing ecosystem services.

Microplastics pose a serious ecological threat to rivers in China, and the construction of a large number of dams has complicated this problem. Ten dams of the Shaying River were chosen to investigate the abundance and composition of microplastics in surface water and sediments of the reservoir and upstream river. Ecological risk was evaluated using species sensitive distribution （SSD） and pollution load index （PLI）. The results showed that the Shaying River was exposed to a severe risk of microplastics from upstream to downstream. The construction of dams did not significantly affect the distribution of microplastics in the river. River sediments became a sink for microplastics in the surface water； however, the ecological risk posed by microplastics in the surface water was greater, and the comparison of the two assessment methods showed that the species sensitivity distribution assessment better reflected the accumulation and feeding behavior of organisms to pollutants compared to the pollution load index.

Microplastics （MPs） coexist with plasticizers in the aqueous environment to form composite pollution, but the adsorption and desorption behaviors of MPs and plasticizers under natural conditions are unknown. Polyvinyl chloride （PVC） and rubber were used as the target MPs to characterize the changes in their morphological features after aging for one anniversary in atmospheric exposure and lake sedimentary burial environments and to investigate the adsorption and desorption behavior of the MPs to the coexisting phthalate esters （PAEs） plasticizer before and after aging. The results showed that the surface of MPs was rougher after exposure to the atmospheric environment and burial in a depositional environment, showing the characteristics of porous polymers. The carbonyl index （CI） of PVC and rubber increased by 62.2% and 321.2%, respectively, in the atmospheric environment and increased by 51.1% and 223.1%, respectively, in the depositional environment. The atmospheric exposure was capable of accelerating the aging process of MPs. PAEs were adsorbed on the surface of MPs through hydrophobic interaction, and the amount of adsorption was significantly and positively correlated with their hydrophobic properties. The adsorption capacity and adsorption rate of PVC on PAEs were inhibited after aging. Aging promoted the adsorption of rubber on strongly hydrophobic PAEs plasticizers and inhibited the adsorption of weakly hydrophobic PAEs. The environmental aging process reduced the desorption of strongly hydrophobic PAEs from rubber, enhanced the reversibility of rubber adsorption of weakly hydrophobic PAEs, and increased the desorption rate of PAEs from PVC.

As climate change, such as global warming, has become a global environmental issue, clarifying the mechanism driving the carbon budget based on land use change has become an inevitable path to realize the "double carbon" goal. Based on the land use change characteristics in the Hangzhou Metropolitan Area from 1995 to 2020, this study employed the inventory accounting method, concentration index, and panel regression models to investigate the driving mechanisms of carbon budget dynamics influenced by land use changes. Moreover, the study utilized a "scenario-actor" policy analysis framework to propose low-carbon strategies through the integration of land use management within territorial spatial planning. The research findings were as follows： ① The carbon source capacity in the study area significantly surpassed its carbon sink capacity. The overall carbon budget concentration index had yet to exceed the 0.4 "alert threshold," with spatial concentration levels as follows： Hangzhou > Huangshan > Shaoxing > Quzhou > Jiaxing ≈ Huzhou. ② For croplands, larger areas and greater shape regularity contributed to a reduction in carbon budgets. Conversely, for constructed lands, expansive areas and increased fragmentation intensified the carbon budget levels, primarily driven by other urban land categories. ③ An increased proportion of croplands and higher land use heterogeneity promoted spatial equilibrium in carbon budgets, whereas the larger coverage and fragmentation of industrial and other urban lands led to an uneven spatial distribution of carbon budgets. ④ Low-carbon optimization of territorial space needs to adjust for the structure and form of carbon source functional land use as a key driver. At the policy implementation level, the central government and urban residents demonstrated strong support for low-carbon territorial control. However, cooperation from local governments, enterprises, and rural residents was suboptimal, necessitating complementary policies for effective guidance. This study holds practical significance for enhancing land use efficiency and promoting low-carbon urban development.

Identifying the influencing factors of soil heavy metal content changes is the basis for reducing or preventing soil heavy metal pollution. Taking an agricultural experimental field in Changping District of Beijing as an example, the heavy metal content changes in As, Cr, Cu, Ni, Pb, and Zn from 2012 to 2022 were firstly analyzed. Secondly, the influencing factors of the heavy metal content changes were detected based on the geographical detector at the single-target and multi-target levels, respectively. Finally, comparative experiments with the correlation analysis method and existing studies were set up to evaluate the effectiveness of the identification method of influencing factors developed in this study. The results showed that human activity factors have exacerbated the changes in soil heavy metal content in the study area as follows： ① At the single-target level, the land use type was the main influencing factor on the changes in Cr, Cu, and Zn contents, and the annual deposition flux influenced the changes in As. The results of the interaction detection showed that there was an enhancement effect among the factors, and the interaction of the human activity factors dominated for the factor identification. ② The results of the multi-target level detection covered the results of the single-target level detection, which could identify more influencing factors. The land use type affected the changes in Cu, Zn, Cr, Ni, and As, and the changes in As and Zn were influenced by the annual deposition fluxes. ③ The multi-target identification method coupled with geographical detector and principal component analysis could effectively identify the influencing factors of soil heavy metal content changes, which was much more effective than the single soil heavy metal correlation method. The developed multi-target identification method for influencing factors of heavy metal content changes can provide technical support for the regional pollution monitoring and macro-management of soil heavy metals.

Maize-soybean compound intercropping has the potential to increase yield and is being tested for spreading in Huang-Huai-hai Plain. However, the main regulatory regions of this cropping pattern on soil microbial communities have not been clarified. In the present study, the tested samples were collected from three maize root zones of bulk soil, rhizosphere soil, and roots under mono- and intercropping planting modes, respectively. The non-rhizosphere soil chemical properties and enzyme activities were determined, and bacterial communities were characterized using high-throughput sequencing of the 16S rRNA gene V3-V4 region. Compared with monocropping, the maize bulk soil electric conductivity （EC）, soil organic matter （SOM）, available potassium （AK）, available phosphorus （AP）, total nitrogen （TN）, and enzyme activities of intercropping were significantly increased. The α diversities and β diversity of the bacterial community in rhizosphere soil were significantly different between the two planting modes. There were 11 bacteria genera with significantly higher abundance in the rhizosphere soil of compound planting than that of monoculture, and TN, AP, and catalase were the three most important factors contributing to their distribution. The abundances of 8 genera among the 11 genera mentioned above, unclassified Vicinamibacterales, unclassified Geminicoccaceae, MND1, unclassified Gemmatimonadaceae, Acidibacter, unclassified Vicinamibacteraceae, Sphingomonas, and unclassified Comamonadaceae were significantly positively correlated with TN. As for the bacteria distribution in maize root, AK contributed the most and had a significantly negative correlation with unclassified Rhizobiaceae and unclassified Microscillaceae and a positive correlation with Haliangium. Maize-soybean compound intercropping affected mainly the bacterial community of maize rhizosphere and had an evident effect on soil fertilizer cultivation and microbial diversity regulation, which provides a theoretical basis and practical guidance for rational intercropping to maintain agroecosystem biodiversity.

Petroleum pollution has become a prominent global environmental problem, restricting the coordinated development of the economy and the ecological environment. Although bioremediation has the advantages of low carbon, high efficiency, and safety, the complexity and severity of the pollution makes it difficult to achieve the remediation purpose with a single bioremediation. Ecological remediation based on bioremediation can integrate carbon neutrality and ecological environmental protection, synergistically promote pollution reduction and carbon reduction, ensure the sustainability of soil and sediment to fulfil ecosystem service functions, and ultimately achieve soil health and sediment health. Therefore, the transition from bioremediation to ecological restoration is the optimal choice for environmental management and ecosystem maintenance at this stage. Here, we first analyzed the micro-removal mechanism of petroleum hydrocarbons in different bioremediation techniques and discussed the types and characteristics of different bioremediation techniques from an ecological point of view. Based on this, the necessity of bioremediation for ecological restoration was analyzed in detail. Finally, a reasonable outlook on the development of ecological remediation is given to provide theoretical support for optimizing ecological remediation of petroleum pollution.

Methane （CH₄） and nitrous oxide （N₂O） are concerning greenhouse gases. Urban rivers have been important emission sources of CH₄ and N₂O in recent years. It is meaningful for city greenhouse gas reduction to provide a systematic analysis of spatiotemporal characteristics, mechanisms, and influencing factors of the production and emission of CH₄ and N₂O from urban rivers. This study combed measured data of urban river CH₄ and N₂O dissolution concentrations and emission fluxes from related literature published in the past 20 years and also concluded the spatiotemporal characteristics of urban river CH₄ and N₂O emissions. This study estimated that CH₄ and N₂O emissions （expressed by CO₂-eq） from urban rivers in Beijing were 234.63 and 59.53 Gg CO₂-eq in 2018, whereas CH₄ and N₂O emissions （expressed by CO₂-eq） from urban rivers in Shanghai were 159.86 and 260.24 Gg CO₂-eq in 2018, respectively. These results demonstrated that urban rivers have become important CH₄ and N₂O emission sources. This study summarized the production/consumption processes and import/export pathways of CH₄ and N₂O in urban rivers. What is more, this study discussed the main influencing factors of urban river CH₄ and N₂O production and emissions from the perspectives of river environmental conditions and urbanization effects. At last, the present work prospected the future research trends of urban river CH₄ and N₂O emissions and provides urban rivers with scientific support for greenhouse gas reduction.

To clarify the impact of transportation on the sensitive and fragile ecosystems of the Qinghai Tibet Plateau and major ecological safety barrier functions, soil samples within 0-25 m on the roadside were collected from sections of national highways such as G214, G213, G345, G109, G316, and G317, and the contents of six heavy metals were analyzed. Then, the degree of heavy metal pollution and the risk of ecological hazards were evaluated using the single-factor pollution index method （P_i）, Nemero comprehensive index method （P_N）, and potential ecological risk index method （RI）. The results showed that the heavy metal contents of As, Cd, Hg, Ni, Pb, and Zn in the soil of important transportation national roads on the Qinghai Tibet Plateau ranged from 5.65 to 176.00, 0.04 to 0.27, 0.01 to 0.14, 9.52 to 113.00, 9.16 to 54.50, and 24.70 to 109.00 mg·kg^-1, respectively, showing high variability. In some sections of the soil, the values of the elements As, Cd, and Hg were higher than the local soil background values. The single-factor pollution index of heavy metals in roadside soil was P_i （As） > P_i （Hg） > P_i（Cd） > P_i （Pb） > P_i （Ni） > P_i （Zn）. The Nemero comprehensive pollution index ranged from 0.41 to 9.20, with an average value of 1.53, indicating clean and mild pollution. Some areas showed a moderate or severe pollution. The average potential ecological risk index of the research section was 106.2, and the soil was generally in a state of no pollution and light pollution. Only two road sections had soil heavy metal enrichment reaching moderate and strong ecological hazards. The comprehensive potential risk of the G213a road section indicated moderate to severe ecological risk, mainly contributed by Hg, As, and Cd. The comprehensive pollution risk of the G317 road section indicated mild to moderate ecological risk, mainly contributed by Hg and Cd. The heavy metal content in the soil of the Qinghai Tibet Plateau road area was not significantly correlated with the roadside distance and soil depth but was significantly positively correlated with the annual average temperature （P < 0.05）. In all, there was a trend of heavy metal input into the soil environment in areas with intense human activities and high traffic flow during road construction on the Qinghai Tibet Plateau.