Crowellcarson7414

Abiotic soil CO2 flux (Fa) has been observed in drylands worldwide, while its generation mechanism is not determined. The remarkable features for the occurrence time of Fa, that the positive Fa (CO2 emission from soil) and negative Fa (CO2 absorption by soil) generally occurred in the daytime and nighttime, respectively, suggested that the generation of Fa is related to temperature. Previous studies have focused on the sole effect of soil temperature (Ts) or air temperature (Ta) on Fa, but very little is regarding to the overall response of Fa to both Ta and Ts in the air-soil system. In the Mu Us Desert, China, we continuously measured the hourly Fa, Ts, Ta and the difference between Ta and Ts (Ta-Ts) at 4-day intervals from June to October 2016. During this period, soil abiotically absorbed atmospheric CO2 at a rate of 0.32 ± 0.19 g m-2 d-1. Fa was not correlated with Ts and was weakly correlated with Ta, however, it was strongly and positively correlated with Ta-Ts. A quadratic model adequately fitted the relationship between Fa and Ta-Ts, and similar relationships were also observed between positive Fa and Ta-Ts and between negative Fa and Ta-Ts. The results of Fa measurement highlight that desert soils can absorb CO2 from the atmosphere through abiotic processes. The relationships of Fa with Ts, Ta and Ta-Ts indicate that, abiotic CO2 exchange between soil and atmosphere depends on air-soil temperature gradient in desert. Furthermore, the thermal convection driven by Ta-Ts may play a major role in the generation of nocturnal negative Fa. Our findings provide a new possible perspective for revealing the reasons of Fa generation in drylands.Urbanization is progressing rapidly. It can affect soils ecosystem services directly through land management and indirectly through changes in the socioeconomic environment, which eventually leads to an increase in emissions of greenhouse gases. Soil carbon (C) sequestration plays an important role in offsetting the anthropogenic C emissions. However, there is limited knowledge of how urbanization affects the soil C especially that in suburban. In this study, we studied changes in easily oxidizable organic C (EOC) and total organic C (TOC) of suburban soils (0-100 cm) in the rapid urbanising megacity Chengdu, China. The EOC stock and TOC stock decreased from the outer-suburb to the inner-suburb by 17.8-28.2% and 5.4-13.5%, respectively; particularly, the inner-suburb EOC decreased by 31.4-38.6% during the past 10 years. The quotient of EOC/TOC in the soil profile, reflecting the stability of soil C, declined from the outer-suburb (0.78) to the inner-suburb (0.20). Factors that influenced the EOC and TOC included the changes in economics (economic density, industrialization), farmland (cultivated area, farmland structure), urbanization (city size, population growth) and traffic flow. Among which, economic density growth was the primarily driver of the loss in TOC, explaining 31.6% of the variation in soil surface TOC and 16.0% of the variation in subsoil TOC; changes in farmland and urban expansion were the main factors contributing to the loss of subsoil EOC, with 40.4% explanatory ability. GSK1904529A datasheet In addition, traffic flow also has contribution to the subsoil EOC loss. We concluded that the increasing soil C loss with decreasing distance from the city centre has a continuous contribution to C emission, and the C loss will persist until the suburbs are fully urbanized. The large losses of EOC and TOC caused by urbanization, and their contribution to global warming, necessitate their consideration in future appraisals of climate change and urban planning projects.This study shows if biologically activated carbon (BAC) is backwashed at the correct frequency, a number of benefits can be derived in addition to aiding the subsequent coagulation process. Previous studies have shown that the BAC improves the removal of dissolved organic carbon (DOC) by subsequent coagulation by decreasing non-coagulable dissolved organic carbon (NC-DOC). However, the actual mechanism of such observation or optimising strategies of NC-DOC removal is unknown. The impact of backwashing on BAC reactor performance in terms of NC-DOC removal and microbial community structure was investigated. A laboratory scale BAC column was operated for more than five months with backwashing at once every five days, but in one cycle it was operated without backwashing for 14 days and the effluent collected at different times from the last backwash was subjected to enhanced coagulation (EC). All the effluent of BAC collected at different days depicted better floc forming characteristics than the feed water which is raw surface water. The effluent collected on day three from the last backwash (BAC-3d) contained the least amount (1.64 mg/L) of NC-DOC despite the highest DOC (3.89 mg/L) of all effluents. The coagulant requirement (5 mg-Fe3+/mg-DOC) was minimal for BAC-3d effluent among raw water and all other BAC effluent water samples. This is remarkable given the raw water contained 2.76 mg/L of NC-DOC. The microbial community on BAC granules on day three contained a higher abundance of biodegradable organic matter (BOM) removing microorganisms and low abundance of opportunistic pathogens. Similar performance in terms of DOC removal with the backwash was also observed in the continuous operation of other BAC columns. Possible backwash frequency that optimises the BAC/EC and derives many other benefits is proposed. The BAC/EC combination could help solve many emerging issues cost-effectively hence, needs further investigation.Many reviewers have applied bibliometric analysis to conduct research on heavy metals (HMs) in Chinese soil and found that risk management decisions were biased to a certain extent due to case distribution difference and uncertainty. The previous methodologies were optimized integrating further uncertainty control and case identification in this study. A solid database was built, which included 779 cases published from 2009 to 2020. link2 Based on the data features, the weight method was used to objectively shield extreme cases and normalize the concentrations. We conducted fuzzy eco- and health risk models via a triangular fuzzy number, and identified the risks from Pb, Cd, As, and Hg as the priority control metals. However, the national HMs risk had complex spatial heterogeneity and significant uncertainty. Thus, an "integrated risk grade criterion (IRGC)" was coupled with the risk threshold concentrations for the eco- and health risks to classify the each case. The cases above the moderate IRGC grade for Cd or Hg accounted for approximately 50%, and were mainly in the west and north of China, respectively. The high-grade areas were mostly in the south of China, including the Xijiang-Pearl River Basin and the Yangtze River Basin. It was demonstrated that warning health risks were likely a local question and that the ecological risks from Hg and Cd were considerable across China. link3 By reviewing and summarizing the text information, high grades of soil Cd, Pb, and As were frequently reported in the villages associated with the mining industry, and certain soil Cd near suburban industrial complexes also caused warning health risks. Finally, this study proposed priority control objects for hierarchical risk management, including the identified heavy metals, areas, and pilot cities from multi-spatial scales.Epibiotic bacterial community colonized on the plant leaf plays important roles in promoting plant growth and nutrient absorption, but is sensitive to environmental changes. As one of the most important environmental factors affecting the growth of plants and photosynthetic microorganisms, light may affect the diversity, composition, and interactions of the epibiotic bacterial community. Submerged plants in the aquatic ecosystem may be more sensitive to light intensity variations compared to the terrestrial plants since they usually receive less light. However, the effects of light on the interactions between the submerged plants and their epibiotic microbial communities remain uncertain. Here we used the 16S rRNA gene high-throughput sequencing to investigate the diversity and composition of the bacterioplankton and epibiotic bacterial communities of the Cabomba caroliniana under four different shading levels. A total of 24 water and leaf samples were collected from the experimental microcosms near Lake Taihu. We found the epibiotic bacterial community possessed a higher diversity than that of the bacterioplankton community, although the alpha diversity of the bacterioplankton community was more susceptible to different levels of shading. SourceTracker analysis revealed that with the increase of shading, the colonization of bacterioplankton to epibiotic bacteria decreased. Network analysis showed that the bacterial community network at 50% shading level had the lowest modularity and highest clustering coefficient compared to the bacterial community networks of other shading levels. Our findings provided new understandings of the effects of different light intensities on the epibiotic bacterial communities of submerged macrophytes.The conservation level of rare waterbirds reflects the quality of the regional ecological environment and wetlands, and suitable habitat patches and good environmental conditions are bases to support the activities of rare species in habitats. Establishing these conditions is also an important goal of habitat landscape and functional restoration. However, lack of these conditions limits population protection and habitat restoration of rare species. Based on the random forest (RF) algorithm and threshold indicator taxa analysis (TITAN), this paper performed habitat suitability assessment and environmental variable threshold analysis of rare waterbird species in Yancheng coastal wetlands. The results showed that the suitable area proportion of three waterbird species at different habitat sites was less than 20%. The unsuitable area proportions of red-crowned cranes and oriental storks at the CA habitat site were the highest, reaching 86.73% and 85.17%, respectively. In addition, analysis of the importance of environmental variables showed that the main influencing variables affecting the suitable habitat distribution of the three rare waterbirds were habitat type (T_hab), habitat area (A_hab), vegetation coverage (P_fvc), distance to farmland (D_far), distance to reeds (D_ree), ponds density (Ponds), distance to water surface (D_wat) and distance to main roads or seawalls (D_swa). These variables covered the type, area, coverage and distance indicators. With the exception of D_far, Ponds and D_swa, rare waterbirds had response thresholds to each environmental indicator, and these results supported the restoration of landscape structure and function of each habitat site. This study emphasized the importance of foods, water resources and hidden conditions for habitat selection in rare waterbirds. Finally, we proposed the maintenance and restoration patterns of the landscape structure and function of rare waterbird habitats, which are available for other coastal tidal wetlands.This study analyzed the comprehensive impact of renewable energy investment on carbon emissions in China. To achieve this, a nonparametric additive regression model was built. Using the STIRPAT model, we considered six influencing factors economic growth, industrialization level, urbanization level, population aging, trade openness, and renewable energy investment. This enabled the exploration of the existence, direction, and intensity of the impact of renewable energy investment on carbon emissions. The results of the linear component of the model showed that renewable energy investment can slightly reduce carbon emissions. The results of the nonlinear component of the model showed that the impacts of renewable energy investment on carbon emissions were inconsistent at different stages of the investment. In the early stage, the renewable energy investment can increase carbon emissions. In the middle stage, the renewable energy investment begins to play a role in reducing emissions. In the later stage, renewable energy investment may be associated with increased carbon emissions again.