Biochar-based controlled release nitrogen fertilizers (BCRNFs) have received increasing attention due to their ability to improve nitrogen-use efficiency (NUE) and increase crop yields. We previously ...developed a novel BCRNF, but its effects on soil microbes, NUE, and crop yields have not been reported. Therefore, we designed a pot experiment with five randomised treatments: CK (without urea and biochar), B (addition biochar without urea), B + U (biochar mixed urea), Urea (addition urea without biochar), and BCRNF (addition BCRNF), to investigate the effects of BCRNF on nitrifiers and denitrifiers, and how these impact nitrogen supply and NUE. Results of high-throughput sequencing revealed bacterial community groups with higher nutrient metabolic cycling ability under BCRNF treatment during harvest stage. Compared to Urea treatment, BCRNF treatment stimulated nitrification by increasing the copy number of the bacterial amoA gene and reducing nitrous oxide emission by limiting the abundance of nirS and nirK. Eventually, BCRNF successfully enhanced the yield (~ 16.6%) and NUE (~ 58.79%) of rape by slowly releasing N and modulating the abundance of functional microbes through increased soil nitrification and reduced denitrification, as compared with Urea treatment. BCRNF significantly improved soil NO
, leading to an increase in N uptake by rape and NUE, thereby promoting rape growth and increasing grain yield.
With the rapid development of industry, chromium (Cr) pollutants accumulate constantly in the soil, causing severe soil Cr pollution problems. Farmland Cr pollution hurts the safety of agricultural ...production and indirectly affects human health and safety. However, the current situation of Cr pollution in farmland soil and crops has not been detailed enough. In this study, the evaluation of Cr potential risk in soil-crop systems was conducted in a rural area that was affected by industry and historic sewage irrigation. Ten different crops and rhizosphere soils were sampled from four fields. The results showed that Cr contents in farmland soil exceeded the national standard threshold in China (>21.85%), and the Cr content in edible parts of some agricultural products exceeded that too. According to the PCA and relation analysis, the Cr accumulation in edible parts showed a significant correlation with soil Cr contents and available potassium contents. Except for water spinach, the target hazard quotient (THQ) of the other crops was lower than 1.0 but the carcinogenic health risks all exceeded the limits. The carcinogenic risks (CR) of different types of crops are food crops > legume crops > leafy vegetable crops and root-tuber crops. A comprehensive assessment revealed that planting water spinach in this area had the highest potential risk of Cr pollution. This study provided a scientific and reliable approach by integrating soil environmental quality and agricultural product security, which helps evaluate the potential risk of Cr in arable land more efficiently and lays technical guidelines for local agricultural production safety.
•Epidemiological research of COVID-19 outbreaks in land transportation.•Unique features of land vehicles infect virus transmission.•Measures for mitigating risk of passengers in transport ...environment.•Infections spread on different routes under different conditions.
Land public transport is an important link within and between cities, and how to control the transmission of COVID-19 in land public transport is a critical issue in our daily lives. However, there are still many inconsistent opinions and views about the spread of SARS-CoV-2 in land public transport, which limits our ability to implement effective interventions. The purpose of this review is to overview the literature on transmission characteristics and routes of the epidemic in land public transport, as well as to investigate factors affecting its spread and provide feasible measures to mitigate the infection risk of passengers. We obtained 898 papers by searching the Web of Science, Pubmed, and WHO global COVID database by keywords, and finally selected 45 papers that can address the purpose of this review. Land public transport is a high outbreak area for COVID-19 due to characteristics like crowding, inadequate ventilation, long exposure time, and environmental closure. Different from surface touch transmission and drop spray transmission, aerosol inhalation transmission can occur not only in short distances but also in long distances. Insufficient ventilation is the most important factor influencing long-distance aerosol transmission. Other transmission factors (e.g., interpersonal distance, relative orientation, and ambient conditions) should be noticed as well, which have been summarized in this paper. To address various influencing factors, it is essential to suggest practical and efficient preventive measures. Among these, increased ventilation, particularly the fresh air (i.e., natural ventilation), has proven to effectively reduce indoor infection risk. Many preventive measures are also effective, such as enlarging social distance, avoiding face-to-face orientation, setting up physical partitions, disinfection, avoiding talking, and so on. As research on the epidemic has intensified, people have broken down many perceived barriers, but more comprehensive studies on monitoring systems and prevention measures in land public transport are still needed.
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The interception of rainfall by vegetation canopies plays an important role in the hydrologic process of ecosystems. Most estimates of canopy rainfall interception in present studies are mainly ...through field observations at the plot region. However, it is difficult, yet important, to map the regional rainfall interception by vegetation canopy at a larger scale, especially in the southern rainy areas of China. To obtain a better understanding of the spatiotemporal variation of vegetation canopy rainfall interception with regard to the basin scale in this region, we extended a rainfall interception model by combining the observed rainfall data and moderate resolution imaging spectroradiometer leaf area index (MODIS_LAI) data to quantitatively estimate the vegetation canopy rainfall interception rate (CRIR) at small/medium basin scales in Guangdong Province, which is undergoing large changes in vegetation cover due to rapid urban expansion in the area. The results showed that the CRIR in Guangdong declined continuously during 2004–2012, but increased slightly in 2016, and the spatial variability of CRIR showed a diminishing yearly trend. The CRIR also exhibited a distinctive spatial pattern, with a higher rate to the east and west of the mountainous areas and a lower rate in the central mountainous and coastal areas. This pattern was more closely related to the spatial variation of the LAI than that of rainfall due to frequent extreme rainfall events saturating vegetation leaves. Further analysis demonstrated that forest coverage, instead of background climate, has a certain impact on the canopy rainfall interception, especially the proportion of broad-leaved forests in the basin, but more in-depth study is warranted in the future. In conclusion, the results of this study provide insights into the spatiotemporal variation of canopy rainfall interception at the basin scale of the Guangdong Province, and suggest that forest cover should be increased by adjusting the species composition to increase the proportion of native broad-leaved species based on the local condition within the basin. In addition, these results would be helpful in accurately assessing the impacts of forest ecosystems on regional water cycling, and provide scientific and practical implications for water resources management.
Biochar-based fertilizers have attracted increased attention, because biochar can improve the soil fertility, promote plant growth and crop yield. However, biochar-based controlled release nitrogen ...fertilizers (BCRNFs) still face problems because of the high cost, inefficient production technology, instability of nitrides, and the challenge associated with the controlled release of nutrients. In this study, we hydrothermally synthesised novel BCRNFs using urea-loaded biochar, bentonite and polyvinyl alcohol for controlled release of nutrients. Scanning electron microscopy and gas adsorption were conducted to identify the urea-loading and storage of bentonite in the inner pores of the biochar particles. X-ray diffraction, Fourier transform infrared spectroscopic and X-ray photoelectron spectroscopic studies demonstrated that strengthening the interactions among biochar, urea, and bentonite, helps control the moisture diffusion and penetration of bentonite, thereby leading to nutrient retention. The BCRNF showed significantly improved nutrient release characteristic compared with that of a mixture of biochar and urea. This urea-bentonite composite loaded with urea provides control over the release of nutrients stored in the biochar. BCRNF, especially those produced hydrothermally, can have potential applications in sustainable food security and green agriculture.
Bacteria and archaea colonizing on biochar have been reported to possess nitrogen-metabolizing abilities. A larger specific surface area of biochar may enhance the activities of nitrous oxide ...(N2O)-reducing microbes, thereby mitigating N2O emission; however, the underlying mechanisms remain unclear. A 56-day incubation assay was performed with five treatments: no addition, urea only, and addition of three types of biochars (with different specific surface areas: 1193, 2023, and 2773 m2 g−1) combined with urea. N2O emission increased with the specific surface area of biochar up to 2023 m2 g−1 and decreased thereafter by 37% as compared with the urea only addition. By increasing soil pH, C/N ratio, nitrogen availability, and cation exchange capacity, the biochar with the largest specific surface area decreased soil N2O emission by affecting the diversity, abundance, and composition of total bacteria and N2O-producing microbial communities. A larger specific surface area of biochar correlated with a higher abundance of nitrogen-fixing (nifH), -nitrifying (amoA), and -denitrifying (nirK, nirS, and nosZ) genes. An increased abundance of ammonia-oxidizing bacteria and archaea, in the biochar with a smaller specific surface area, resulted in higher N2O emission. As the abundance of nosZ increased, the addition of the biochar with the largest specific surface area resulted in a higher ratio of nosZ/(amoA + nirS + nirK), leading to decreased N2O emission. Furthermore, the abundance of nifH, amoA, nirK, and nosZ on biochar (extraction from soil after 56-day incubation) was positively correlated with that in soil. Thus, the relative specific surface area of biochar should be taken into consideration when using it in agriculture, as our results show that biochars with larger specific surface areas decrease N2O emission by recruiting N2O-reducing microbes and upregulating the abundance of nitrogen-fixing, -nitrifying, and -denitrifying genes.
•A larger biochar surface area decreases soil N2O emission.•Bacteria stimulated by biochar possesses nitrogen-metabolizing activity.•N2O reducing microbes on biochar and in the soil are positively related.•nosZ, a functional marker gene, localization on biochar decreases soil N2O emission.
Microbial immobilization technology is considered an efficient bioremediation method for chromium (Cr) pollution. However, it is currently unclear which strain is more beneficial for the remediation ...of Cr-contaminated water and soil. Therefore, corn straw biochar was used as a carrier to prepare materials for fixing the endophytes Serratia sp. Y-13 (BSR1), Serratia nematodiphila (BSR2), Lysinibacillus sp. strain SePC-36 (BLB1), Lysinibacillus mangiferihumi strain WK63 (BLB2) and the commercial bacteria Shewanella oneidensis MR-1 (BSW). The results demonstrated that, compared with BSW, endophyte-loaded biochar (especially BSR1) was more effective at remediating Cr pollution in water and soil. Endophyte-loaded biochar reduced the abundance of soil pathogenic bacteria, enhanced the number of beneficial plant endophytes, reduced the soil Cr(VI) concentration, improved soil fertility, reduced the plant Cr concentration and improved the yield of lettuce. Redundancy analysis (RDA) and structural equation modelling (PLS-PM) suggested that soil microbes are closely related to soil Cr(VI), plant fresh weight and soil organic matter, whereas endophyte-loaded biochar directly influences plant cell motility pathways by altering plant microbes. This study represents a pioneering investigation into the efficacy of endophyte-loaded biochar as a remediation strategy for Cr pollution.
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•Endophyte-loaded biochar performed better than the commercial one in soil and water Cr(VI) remediation.•Endophyte-loaded biochar reduced soil pathogenic bacteria and Cr(VI) bioavailability while improving soil fertility.•Endophyte-loaded biochar enhanced beneficial plant endophytes, improved plant growth and reduced Cr taken up by plants.•BSR1 had the greatest effect on reducing the concentrations of soil Cr(VI) and plant Cr.
Surface urban heat island (SUHI) is a key climate risk associated with urbanization. Previous case studies have suggested that precipitation (water), radiation (energy), and vegetation have important ...effects on urban warming, but there is a lack of research that combines these factors to explain the global geographic variation in SUHI intensity (SUHII). Here, we utilize remotely sensed and gridded datasets to propose a new water-energy-vegetation nexus concept that explains the global geographic variation of SUHII across four climate zones and seven major regions. We found that SUHII and its frequency increase from arid zones (0.36 ± 0.15 °C) to humid zones (2.28 ± 0.10 °C), but become weaker in the extreme humid zones (2.18 ± 0.15 °C). We revealed that from semi-arid/humid to humid zones, high precipitation is often coupled with high incoming solar radiation. The increased solar radiation can directly enhance the energy in the area, leading to higher SUHII and its frequency. Although solar radiation is high in arid zones (mainly in West, Central, and South Asia), water limitation leads to sparse natural vegetation, suppressing the cooling effect in rural areas and resulting in lower SUHII. In extreme humid regions (mainly in tropical areas), incoming solar radiation tends to flatten out, which, coupled with increased vegetation as hydrothermal conditions become more favorable, leads to more latent heat and reduces the intensity of SUHI. Overall, this study offers empirical evidence that the water-energy-vegetation nexus highly explains the global geographic variation of SUHII. The results can be used by urban planners seeking optimal SUHI mitigation strategies and for climate change modeling work.
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•The influences of background climate on urban heat island intensity (UHII) are explored globally.•UHII and its frequency increase from the arid zone to the humid zone and decrease in extremely humid zone.•A new water-energy-vegetation nexus concept to explain geographic variation in global UHII.•The implications can be used for urban warming mitigation in different climatic regions.
Soil moisture (SM) is essential to microbial nitrogen (N)‐cycling networks in terrestrial ecosystems. Studies have found that SM–atmosphere feedbacks dominate the changes in land carbon fluxes. ...However, the influence of SM–atmosphere feedbacks on the N fluxes changes, and the underlying mechanisms remain highly unsure, leading to uncertainties in climate projections. To fill this gap, we used in situ observation coupled with gridded and remote sensing data to analyze N2O fluxes emissions globally. Here, we investigated the synergistic effects of temperature, hydroclimate on global N2O fluxes, as the result of SM–atmosphere feedback impact on N fluxes. We found that SM–temperature feedback dominates land N2O emissions by controlling the balance between nitrifier and denitrifier genes. The mechanism is that atmospheric water demand increases with temperature and thereby reduces SM, which increases the dominant N2O production nitrifier (containing amoA AOB gene) and decreases the N2O consumption denitrifier (containing the nosZ gene), consequently will potential increasing N2O emissions. However, we find that the spatial variations of soil–water availability as a result of the nonlinear response of SM to vapor pressure deficit caused by temperature are some of the greatest challenges in predicting future N2O emissions. Our data‐driven assessment deepens the understanding of the impact of SM–atmosphere interactions on the soil N cycle, which remains uncertain in earth system models. We suggest that the model needs to account for feedback between SM and atmospheric temperature when estimating the response of the N2O emissions to climatic change globally, as well as when conducting field‐scale investigations of the response of the ecosystem to warming.
The novelty of this study is that we investigated the synergistic effects of temperature, hydroclimate on global N2O fluxes, as the result of soil moisture‐atmosphere feedback impact on N fluxes. We found that soil moisture‐temperature feedback dominates land N2O emissions by controlling the balance between nitrifier and denitrifier genes. The mechanism is that atmospheric water demand increases with temperature and thereby reduces soil moisture, which increases the dominant N2O production nitrifier (containing amoA AOB gene) and decreases the N2O consumption denitrifier (containing the nosZ gene), consequently will potential increasing N2O emissions risk.
•Study the effect of forests on air temperature based on flux towers in mid-to-high latitudes of the Northern Hemisphere.•High vapor pressure deficit during summer droughts decreased the forest's ...cooling effect.•The cooling effect of forests in the warm season is highly sensitive to water stress.•The seasonal warming/cooling of forests responds differently to drought.
The cooling or warming effects of forests in mid-to-high latitudes of the Northern Hemisphere are still a highly controversial topic, while few studies link these effects to drought using large-scale in situ observation data. Here, the temperature difference between forests and non-forests (ΔT; ΔT > 0 represents the warming effect of forests, and vice versa) and its response to drought has been quantified by utilizing eddy covariance data across 31 FLUXNET paired sites, covering a large region in the mid-to-high latitudes (ranging from 40°N to 60°N) of the Northern Hemisphere. We found that high vapor pressure deficit (VPD) during summer (warm season) droughts decreased the cooling effect of forests from ΔT = -0.70 °C to −0.41 °C due to water deficit (precipitation < evapotranspiration). Conversely, winter (cold season) drought decreased the warming effect of forests, due to moderate VPD promoting forests evaporative cooling in water surpluses conditions (precipitation > evapotranspiration). The cooling effect of forests in the warm season is highly sensitive to water stress. Overall, the seasonal warming/cooling of forests responds differently to drought, which increases the difficulty of predicting climate. Our observations can help in the implementation of forestry policies for regulating climate change, especially when the frequency and intensity of drought increase in the future.
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