Dynamics of Land Use/Land Cover Considering Ecosystem Services for a Dense-Population Watershed Based on a Hybrid Dual-Subject Agent and Cellular Automaton Modeling Approach

Land use/land cover represents the interactive and comprehensive influences between human activities and natural conditions,leading to potential conflicts among natural and human-related issues as well as among stakeholders.This study introduced economic standards for farmers.A hybrid approach(CA-ABM)of cellular automaton(CA)and an agent-based model(ABM)was developed to effectively deal with social and land-use synergic issues to examine human–environment interactions and projections of land-use conversions for a humid basin in south China.Natural attributes and socioeconomic data were used to analyze land use/land cover and its drivers of change.The major modules of the CA-ABM are initialization,migration,assets,land suitability,and land-use change decisions.Empirical estimates of the factors influencing the urban land-use conversion probability were captured using parameters based on a spatial logistic regression(SLR)model.Simultaneously,multicriteria evaluation(MCE)and Markov models were introduced to obtain empirical estimates of the factors affecting the probability of ecological land conversion.An agent-based CA-SLR-MCE-Markov(ABCSMM)land-use conversion model was proposed to explore the impacts of policies on land-use conversion.This model can reproduce observed land-use patterns and provide links for forest transition and urban expansion to land-use decisions and ecosystem services.The results demonstrated land-use simulations under multi-policy scenarios,revealing the usefulness of the model for normative research on land-use management.

Can the Grain-for-Green Program Really Ensure a Low Sediment Load on the Chinese Loess Plateau?

The Chinese Loess Plateau is the most seriously eroded area in the world and contributes the vast majority of the sediment that goes into the Yellow River.Since the 1950s,progressive soil and water conservation measures have been implemented—in particular,large-scale ecological restoration has been ongoing since 1999—resulting in a significant reduction of the sediment load.However,the mechanism of the sediment transport dynamics is not fully understood due to multiple and complicated influencing factors including climate change and human activities(e.g.,ecological restoration).A challenging question,then,arises:Is the current low sediment level a“new normal”in this era and in the future?To address this question,we selected a typical loess hilly region where considerable ecological restoration has been implemented,and which is regarded as the site of the first and most representative Grainfor-Green program in the Loess Plateau.We investigated the evolution of discharge–sediment relationships in the past decades(1960–2010)and their association with the soil and water conservation measures in this area.The results showed that there was a distinct change in the regression parameters of the commonly used annual discharge–sediment regression equation—a continuously increasing trend of parameter b and a decreasing trend of parameter a,accompanying the ecological restoration.The increase in exponent b(i.e.,a steeper slope)implies a potential lower sediment load resulting from low discharge and a potential higher sediment load resulting from large discharge.This finding may question the new normal of a low sediment level and implies the potential risk of a large sediment load during extremely wet years.

Interactions of Microplastics and Methane Seepage in the Deep-Sea Environment

Microplastics(MPs)are important exempla of the Anthropocene and are exerting an increasing impact on Earth’s carbon cycle.The huge imbalance between the MPs floating on the marine surface and those that are estimated to have been introduced into the ocean necessitates a detailed assessment of marine MP sinks.Here,we demonstrate that cold seep sediments,which are characterized by methane fluid seepage and a chemosynthetic ecosystem,effectively capture and accommodate small-scale(<100μm)MPs,with 16 types of MPs being detected.The abundance of MPs in the surface of the sediment is higher in methane-seepage locations than in non-seepage areas.Methane seepage is beneficial to the accumulation,fragmentation,increased diversity,and aging of MPs.In turn,the rough surfaces of MPs contribute to the sequestration of the electron acceptor ferric oxide,which is associated with the anaerobic oxidation of methane(AOM).The efficiency of the AOM determines whether the seeping methane(which has a greenhouse effect 83 times greater than that of CO_(2)over a 20-year period)can enter the atmosphere,which is important to the global methane cycle,since the deep-sea environment is regarded as the largest methane reservoir associated with natural gas hydrates.

Watershed Ecology and Its Applications

Global climate change and intense human activities greatly alter natural eco-hydrological processes in multi-scale watersheds, resulting in a series of threats to human society and ecosystems that include the increase of extreme climatic events, water quality degradation, and decreases in biodiversity and ecosystem stability. Many theories and approaches on eco- logical restoration for different types of water environments （e.g., rivers, lakes, marshes, and estuaries） have been proposed in the existing research. However, hydrologi-cal connections, mass and energy transports are usually consider- able among the different types of water environments in a watershed, and restoration measures for one component typically affect other components in the same watershed.

A New Method of Assessing Environmental Flows in Channelized Urban Rivers

Assessing environmental flows （e-flows） for urban rivers is important for water resources planning and river protection, Many e-flow assessment methods have been established based on species＇ habitat pro- vision requirements and pollutant dilution requirements, To avoid flood risk, however, many urban rivers have been transformed into straight, trapezoidal-profiled concrete channels, leading to the disappearance of valuable species, With the construction of water pollution-control projects, pollutant inputs into rivers have been effectively controlled in some urban rivers, For these rivers, the e-flows determined by tradi- tional methods will be very small, and will consequently lead to a low priority being given to river pro- tection in future water resources allocation and management, To more effectively assess the e-flows of channelized urban rivers, we propose three e-flow degrees, according to longitudinal hydrological con- nectivity （high, medium, and low）, in addition to the pollutant dilution water requirement determined by the mass-balance equation, In the high connectivity scenario, the intent is for the e-flows to maintain flow velocity, which can ensure the self-purification of rivers and reduce algal blooms; in the medium connectivity scenario, the intent is for the e-flows to permanently maintain the longitudinal hydrological connectivity of rivers that are isolated into several ponds by means of weirs, in order to ensure the exchange of material, energy, and information in rivers; and in the low connectivity scenario, the intent is for the e-flows to intermittently connect isolated ponds every few days （which is designed to further reduce e-flows）, The proposed methods have been used in Shiwuli River, China, to demonstrate their effectiveness, The new methods can offer more precise and realistic e-flow results and can effectively direct the construction and management of e-flow supply projects,

Soil Organic Carbon Changes in City Areas of China Over the Past Three Decades:Implications for Achieving Carbon Neutrality

The substantial amount of greenhouse gas emissions from anthropogenic activities has caused the global mean surface temperature to increase by 0.99℃since the industrial revolution[1].China is committed to achieving carbon neutrality by 2060 in response to climate change[2].Soil stores approximately 2344–3000 Pg(1015 g)of carbon at depths of 0–100 cm in terrestrial ecosystems,an amount approximately equivalent to twice the amount in the atmospheric carbon pool and three times that in the terrestrial biomass;therefore,even a small change in soil carbon stocks will exert significant impacts on atmospheric CO_(2)concentrations[3].

An improved ET control method to determine the water-saving potential for farmland in Baiyangdian Watershed, China

Resource-based water-saving potential has been recognized as the reduction of evapotranspiration and water loss of inefficient irrigation systems. In this paper, an improved evapotranspiration control model is applied to calculate resource-based water-saving potential, considering the influences of effective rainfall （uncontrolled evapotranspiration） and irrigated water （controlled evapotranspiration）. Farmland in Baiyangdian Watershed, a highly productive area in northern China, is analyzed to determine the water-saving potential of irrigation processes. The water-saving potential was zero, 163.90 × 10^6m3, and 318.24 × 10^6m3 in wet, normal, and dry years, respectively, and was greater in years with less rainfall. Under the combined effect of rainfall, crop water consumption, and crop water requirements, the water-saving potential showed obvious temporal and spatial variations. July and August comprised almost 98.6% of the annual potential. In the northeast and southwest corner of the study area, potential approached zero. The potential was 1.53 times greater in the north-central than in the south-central area. The model can furnish the appropriate timing and region to water managers for implementing water-saving strategies.

Eco-environmental water demands for the Baiyangdian Wetland

In recent years,the hydrological characters of Baiyangdian Wetland have changed greatly,which,in turn,influence the biotic component,the structure and function of the wetland ecosystem.In order to determine the demands for water resources of ecological wetland system,a method of ecological water level coefficient was suggested to calculate the water resources demands for wetland environment use.This research showed that the minimum coefficient is 0.94 and the optimal coefficient is more than 1.10.According to these two coefficients,the ecological water level and water quantity can be estimated.The results indicate that the amount of the minimal and optimal eco-environmental water require-ments are 0.87×10^(8) and 2.78×10^(8)m^(3) in average monthly,respectively,with the maximum eco-environmental water requirement in summer and the minimum in winter.The annual change of eco-environment water demand is in accord-ing with the climate change and hydrological characters.The method of ecological water level emphasizes that wetland ecosystem adapts to the hydrological conditions,so it can be used in practice well.

Future climate change decreases multi-pathway but increases respiratory human health risks of PAHs across China

Future climate change will affect the environmental fate of hydrophobic organic contaminants(HOCs)and associated human health risks,yet the extent of these effects remains unknown.Here,we couple a high-resolution environmental multimedia model with a bioaccumulation model to study the multimedia distribution of 16 priority polycyclic aromatic hydrocarbons(PAHs),a group of HOCs,and assess future PAH-related human health risks under varying climate change scenarios over China at a continental scale.After removing the effects of PAH emission changes,we find that the total PAH concentrations would decrease in the air,freshwater,sediment,soil,and organisms,while the high-molecular-weight PAH would increase in the air with climate warming from 1.5°C to 4°C.Consequently,the multi-pathway exposure human health risks predominately influenced by dietary ingestion are expected to decrease by 1.7%–20.5%,while the respiratory risks are projected to rise by 0.2%–5.8%in the future.However,the persistently high multi-pathway human health risks underscore the need for reducing future PAH emissions by 69%compared with 2009 levels in China.Our study demonstrates the urgency of limiting PAH emissions under future climate change for public health and highlights the importance of including the contribution of dietary ingestion in human health risk assessment.

A Bayesian method for comprehensive water quality evaluation of the Danjiangkou Reservoir water source area, for the middle route of the South-to-North Water Diversion Project in China

The Danjiangkou Reservoir is the water source for the middle route of the South-to-North Water Diversion Project in China. Thus, its water quality status is of great concern. Five water quality indicators （dissolved oxygen, permanganate index, ammonia nitrogen, total nitrogen, and total phosphorus）, were measured at three monitoring sites （the Danjiangkou Reservoir dam, the Hejiawan and the Jiangbei bridge）, to investigate changing trends, and spatiotemporal characteristics of water quality in the Danjiangkou Reservoir area from January 2006 to May 2012. We then applied a Bayesian statistical method to evaluate the water quality comprehensively. The normal distribution sampling method was used to calculate likelihood, and the entropy weight method was used to determine indicator weights for variables of interest in to the study. The results indicated that concentrations of all five indicators increased during the last six years. In addition, the water quality in the reservoir was worse during the wet season （from May to October）, than during the dry season （from November to April of the next year）. Overall, the probability of the water＇s belonging to quality category of type lI, according to environmental quality standards for surface water in China, was 27.7%-33.7%, larger than that of its belonging to the other four water quality types. The increasing concentrations of nutrients could result in eutrophication of the Danjiangkou Reser- voir. This method reduced the subjectivity that is commonly associated with determining indicator weights and artificial classifications, achieving more reliable results. These results indicate that it is important for the interbasin water diversion project to implement integrated water quality management in the Danjiangkou Reservoir area.

Growth and nutrient accumulation of Phragmites australis in relation to water level variation and nutrient loadings in a shallow lake

Shallow lake eutrophication is a global environmental issue. This study investigated the effects of water level variation and nutrient loadings on the growth and nutrient accumulation of Phragmites australis （reed） by field samplings in Baiyangdian Lake, the largest shallow lake of northern China. The field samplings were conducted in two sites of different nutrient loadings during the whole growth period of reeds, and three types of zones with different water depths were chosen for each site, including the terrestrial zone with water level below the ground, the ecotone zone with the water level varying from belowground to aboveground, and the submerged zone with water level above the ground. The result showed that reed growth was more limited by water level variation than nutrient loadings. The average stem lengths and diameters in terrestrial zones were about 26.3%-27.5% and 7.2%-12.0% higher than those in submerged zones, respectively. Similarly, the terrestrial status increased the aboveground biomass of reeds by 36.6%-51.8% compared with the submerged status. Both the nutrient concentrations and storages in the aboveground reeds were mainly influenced by the nutrient loadings in surface water and sediment rather than the water level variation of the reed growth environment, and the nutrient storages reached their maxima in late August or early September. It was observed that the maximum nitrogen storage occurred in the terrestrial zone with higher nutrient loadings, with the value of 74.5 g/m2. This study suggested that water level variation and nutrient loadings should be considered when using reeds to control and remediate eutrophication of shallow lakes.

Turnover and loss of nitrogenous compounds during composting of food wastes

Few people have so far explored into the research of the dynamics of various nitrogenous compounds(including water-soluble nitrogen)in composting of food wastes.This study aimed to investigate the solid-phase nitrogen,water-soluble nitrogen,nitrogen loss together with ammonia volatilization in the process of food wastes composting.A laboratory scale static aerobic reactor in the experiment was employed in the composting process of a synthetic food waste,in which sawdust was used as the litter amendment.In the experiment,oxygen was supplied by continuous forced ventilation for 15 days.The results have shown that the concentrations of total nitrogen and organic nitrogen decrease significantly in the composting process,whereasNH_(4)^(+)-N concentration increases together with little fluctuation in NO_(3)^(-)-N.After composting,the total content of the water-soluble nitrogen compounds in the compost greatly increased,the total nitrogen loss amounted to 50% of the initial nitrogen,mainly attributed to ammonia volatilization.56.7% of the total ammonia volatilization occurred in the middle and late composting of the thermophilic stage.This suggested that the control at the middle and late composting of thermophilic stage is the key to nitrogen loss in the food waste compost.

Deep-sea organisms research oriented by deep-sea technologies development

Deep-sea environment,characterized by high pressures,extremely high/low temperatures,limited photosynthesis-generated organic matter,darkness,and high levels of corrosion,is home to flourishing special ecosystems in the world.Here,we illustrate how the deep-sea equipment offers insights into the study of life in the deep sea based on the work in the past five decades.We first describe how organisms in the deep sea are studied,even though it is highly difficult to get access to such extreme environments.We then explain the role of deep-sea technologies in advancing research on the evolution of organisms in hydrothermal vents,cold seeps,seamounts,oceanic trenches,and whale falls from the following perspectives:biological diversity,mechanisms of environmental adaptation,biological evolution,and ecosystem connectivity.Finally,to better understand the function and service of deep-sea organisms,and further conserve the special creatures under anthropologic activity and climate change,we highlight the importance of innovative deep-sea technologies to promote cutting-edge research on deep-sea organisms,and note the remaining challenges and developing directions for deep-sea equipment.

Multi-scale evaluation of river health in Liao River Basin,China

Previous studies on river health evaluation mainly focused on characterizations at a river-corridor scale and ignored the complex interactions between the river ecosystem and other components of the river basin.Based on the consideration of the interactions among rivers,associated river basin and habitats,an assessment framework with multi-scale indicators was developed.An index system divided among these three scales to characterize the health of river ecosystems in China’s Liao River Basin was established.Set pair analysis was applied to integrate the multi-scale indicators and determine the health classes.The evaluation results indicated that the rivers in the western and eastern zones of the Liao River were classified as sick,and rivers in the main stream of the Liao and Huntai rivers were classified as unhealthy.An excessive level of disturbances,such as large pollution loads and dense construction of water conservation projects within the river basin,were the main causes of the river health deterioration.

Ecosystem health assessment of urban rivers and lakes-Case study of “the six lakes”in Beijing,China

The assessment of the ecosystem health of urban rivers and lakes is the scientific basis for their management and ecological restoration.This study developed a three-level indicator system for its assessment.The results indicated that:Zhonghai and Nanhai are in the state of transition from unhealthy to critical state and all the other lakes are in unhealthy states.Water environmental quality,structure and function of the aquatic ecosystem,and the structure of waterfront areas were the constraints.Nanhai was ranked as poor and the others were all ranked as very poor.However,the ecological environment of Zhonghai and Nanhai were better than the others,the sums of the degree of membership to the healthy state and critical state were all close to 0.6.and the restorations of these lakes were moderate.The sums of the degree of membership to the healthy state and critical state of the other lakes were under 0.3,as it was difficult to restore these lakes.Some suggestions on scientific management and ecological restoration of the six lakes were proposed:①To control non-point pollution and to improve the water quality of six lakes and the water entering into these lakes;②To improve the hydrological conditions of six lakes;③To rehabilitate the aquatic ecosystem and waterfront areas.

The frontier evolution and emerging trends of hydrological connectivity in river systems:a scientometric review

With the intensification of climate change and human activities,the watershed ecosystem is seriously fragmented,which leads to the obstruction of hydrological connectivity,and further causes the degradation of the ecosystem.As the value of wetlands continues to be exploited,hydrological connectivity becomes increasingly significant.In this paper,the characteristics and development of hydrological connectivity research from 1998 to 2018 were analyzed through the scientometric analysis based on Web of Science database.CiteSpace,an analytical software for scientific measurement,is used to visualize the results of the retrieval.The analysis results of co-occurrence,co-operative and co-cited network indicate that the hydrological connectivity is a multidisciplinary field which involves the Environment Science and Ecology,Water Resources,Environmental Sciences,Geology and Geosciences.According to Keyword cooccurrence analysis,ecosystem,floodplain,dynamics,climate change and management are the main research hotspots in each period.In addition,the co-cited analysis of references shows that“amphibians”is the largest cluster of hydrological connectivity,and the“channel network”is the most important research topic.It is worth noting that the“GIWS”(Geographically Isolated Wetlands)is the latest research topic and may be a major research direction in the future.

Is urban development an urban river killer? A case study of Yongding Diversion Channel in Beijing, China

The high population and concrete environment alter urban areas by changing temperature, rainfall runoff, and water resource utilization activities. This study was conducted to investigate the water quality features of the Yongding Diversion Channel in Beijing, China, and its relationship with rainfall and urban development. Monthly water quality data were obtained from April to October of 2004 at monitoring sites of Sanjiadian, Gaojing, Luodaozhuang, and Yuyuangtan. The monthly water quality grades from 2007 to 2011 were also investigated and compared with those of other rivers. Dissolved oxygen and pH showed greater decreases after one or two moderate rainfall events than several light rainfall events. The potassium permanganate index （CODMn）, ammonia nitrogen （NH3-N） and total phosphorus （TP） increased more after several light rainfall events than after one or two moderate or heavy rainfall events. Pollutant concentrations （CODMn, NH3-N, TP） in downstream regions showed greater changes than those in upstream areas after heavy rainfall events. Intense human activities around the channel greatly influenced the water quality of the channel in rainy season because of runoff pollution; however, heavy rainfall had a strong dilution effect on the pollutant concentrations in rivers. Overall, urban development has obviously deteriorated the water quality of the Yongding Diversion Channel as indicated by an increase in the water quality index from 3.22 in 2008 to 4.55 in 2010. The Pearson correlation between monthly rainfall and water quality indices from 2007 to 2011 ranged from 0.1286 to 0.6968, generally becoming weaker as rainfall and rainfall runoff became more random and extreme.

Sensitivity analysis for the total nitrogen pollution of the Danjiangkou Reservoir based on a 3-D water quality model

Inter-basin water deal of nitrogen are great transfers containing a great threats to human health, biodiversity, and air and water quality in the recipient area. Danjiangkou Reservoir, the source reservoir for China＇s South-to-North Water Diversion Middle Route Project, suffers from total nitrogen pollution and threatens the water transfer to a number of metropolises including the capital, Beijing. To locate the main source of nitrogen pollution into the reservoir, especially near the Taocha canal head, where the intake of water transfer begins, we constructed a 3-D water quality model. We then used an inflow sensitivity analysis method to analyze the sig- nificance of inflows from each tributary that may contribute to the total nitrogen pollution and affect water quality. The results indicated that the Han River was the most significant river with a sensitivity index of 0.340, followed by the Dan River with a sensitivity index of 0.089, while the Guanshan River and the Lang River were not significant, with the sensitivity indices of 0.002 and 0.001, respectively. This result implies that the concentration and amount of nitrogen inflow outweighs the geographical position of the tributary for sources of total nitrogen pollution to the Taocha canal head of the Danjiangkou Reservoir.

Methane mitigation: Learning from the natural marine environment

During the past decades,public attention regarding global warming has mainly focused on CO_(2) reduction;however,CH4,another important greenhouse gas,has a global warming potential that is 84 times higher than that of CO_(2) on a 20-year basis.The annual atmospheric amount of CH4 in 2020 reached its highest level since systematic monitoring began in 1983(Figure 1A).To date,despite coronavirus 2019 shutdowns,methane has contributed approximately 30%to global warming.Recently,a series of timely appeals,such as“The Global Methane Pledge”signed at the United Nations Climate Change Conference(COP26)and the“Global Methane Assessment”from the United Nations Environment Program,have called on global methane reduction and mitigation.

State control, access to capital and firm performance

We study the effect of state control on capital allocation and investment in China, where the government screens prospective stock issuers. We find that state firms are more likely to obtain government approval to conduct seasoned equity offerings than non-state firms. Further, non-state firms exhibit greater sensitivities of subsequent investment and stock performance to regulatory decisions on stock issuances than state firms. Our work suggests that state control of capital access distorts resource allocation and impedes the growth of non-state firms. We also provide robust evidence that financial constraints cause underinvestment.