Dianchi Lake Basin Research Articles

Research on the coupling coordination of land use and eco-resilience based on entropy weight method: a case study on Dianchi Lake Basin

Research on the coupling coordination of land use and eco-resilience based on entropy weight method: a case study on Dianchi Lake Basin

Analysis of long-term spatio-temporal changes of plateau urban wetland reveals the response mechanisms of climate and human activities: A case study from Dianchi Lake Basin 1993–2020

Wetlands serve many functions, including conserving water, providing habitats for animals and plants, and regulating climate change. Their unique ecological effects on the natural environment are indispensable in the whole ecosystem. Dianchi Lake Basin is located in Yunnan-Guizhou Plateau, China, and mainly in Kunming. It is a typical plateau urban wetland area. Based on spatio-temporal hotspot mining, spatio-temporal geographically weighted regression, and adaptive multidimensional grey prediction, we conducted correlation analyses of the wetland changes in Dianchi Lake Basin from 1993 to 2020 under the influence of human activities and natural conditions. The results show that (1) the active wetland change zone in Dianchi Lake Basin is mainly located around Dianchi Lake, and (2) the wetlands in some areas on the north and south of Dianchi Lake declined in the early 21st century, but under the protection policy in recent years, the wetlands in these areas gradually recovered. Meanwhile, the wetlands in most areas around Dianchi Lake showed a significant growth trend from 2018 to 2020. The results suggest that the wetland change in Dianchi Lake Basin is mainly related to the urbanization of Kunming, and it can be divided into five regions (strong negative correlation, weak negative correlation, weak correlation, weak positive correlation, and strong positive correlation) according to the different correlation of human activity intensity, among which the main factors affected by nature are different, but they are all related to temperature. This study shows that, although wetlands in plateau cities can be properly restored under proper protection, wetland protection should be kept in step with the development of plateau cities to support sustainable urban development and carbon neutrality.

Impervious Surface Mapping Based on Remote Sensing and an Optimized Coupled Model: The Dianchi Basin as an Example

Accurately extracting impervious surfaces (IS) and continuously monitoring their dynamics are crucial practices for promoting sustainable development in regional ecological environments and resources. In this context, we conducted experiments to extract IS of the Dianchi Lake Basin by utilizing various features extracted from remote sensing images and applying three different machine learning algorithms. Through this process, we obtained the optimal combination of features and a machine learning algorithm. Utilizing this model, our objective is to map the evolution of IS in the Dianchi Lake Basin, from 2000 to 2022, and analyze its dynamic changes. Our results showed the following: (1) The optimal model for IS extraction in the Dianchi Lake Basin was IMG-SPESVM based on the support vector machine, remote sensing images, and spectral features. (2) From 2000 to 2022, the spatial distribution and shape of the IS in the Dianchi Lake Basin changed significantly, but they all developed in the area around Dianchi Lake. (3) From 2000 to 2015, the rate of expansion of IS gradually accelerated, while from 2015 to 2022, it contracted. (4) From 2000 to 2022, the center of mass of IS moved to the northeast, and the standard deviation ellipse shifted greatly in the south–north direction. (5) Natural factors negatively affected the expansion of IS, while social factors positively affected the distribution of the IS.

The seeds of ecological recovery in urbanization – Spatiotemporal evolution of ecological resiliency of Dianchi Lake Basin, China

As a result of years of monitoring the ecological resiliency of natural areas and cities, it has become clear that it is both important and often feasible to implement ecological and environmental restoration in conjunction with ongoing processes of landscape change development and urbanization. Ecological resiliency and spatiotemporal evolution studies can objectively reveal the resiliency of ecosystems to external disturbances. Ecological monitoring and assessment can also help planners understand regional ecological spatial differentiation patterns and provided data support for planning. In this paper we have analyzes quantitatively the interrelationships of ecological factors in Dianchi Lake Basin (DLB) over the past 30 years and explored the spatial and temporal dynamics of ecological resiliency. Based on remote sensing images and primary data in 1995, 2005, 2010, 2015, 2018, and 2022, we used the center of gravity migration and kernel density analysis to explore the spatial and temporal changes of ecological resiliency. We built the overall resiliency evaluation system using entropy weight in the TOPSIS model, and finally simulate the future changes based on CA-Markov (CA-MC) model. The results show that from 1995 to 2022, the ecological resiliency of land use and vegetation cover in DLB decreased substantially. An important finding was that the ecological resiliency of riparian buffer zone and landscape pattern were generally increasing. The distribution of barycenter movement and kernel density of different levels of ecological resiliency differed significantly and showed fluctuating changes. The extreme low resiliency and extremely resilient areas shift to the northeast, the mildly resilient areas shift to the northwest, and the highly resilient areas shift to the southeast. The overall resiliency level of DLB is predicted to slowly increase from 2022 to 2030 by deduction of the CA-MC model. Our analysis suggests that the study of the evolution of regional ecological resiliency can provide a timely understanding of regional ecological evolution patterns and propose ecological protection strategies.

Synergistic impacts of climate change and human activities on spatiotemporal organic nitrogen burial variation in a plateau lake in southwest China

ABSTRACT The concentration and sources of organic nitrogen (ON) in lake sediments affect lake nitrogen cycles. However, the factors influencing ON accumulation rate (ONAR) are unclear. We collected 3 sediment cores from northern, eastern, and southern Dianchi Lake (DC-N, DC-E, and DC-S, respectively) in July 2014, to study the effects of autochthonous and allochthonous sources of ON. The ON and ONAR increased 2.4–5.1 and 2.6–4.8 times, respectively, from 1900 to 2000, especially since the 1980s, when algal blooms have occurred more frequently. The ON decreased in the order DC-S > DC-N > DC-E, whereas the ONAR decreased in the order DC-N > DC-S > DC-E, suggesting that ONAR was influenced by ON content as well as the depositional environment. The total concentrations of n-alkanes (n-C12 to n-C34) ranged from 4719 to 61 960 ng g−1 in the 3 sediment cores, with proportions varying with vertical depth. The sources of ON were mainly allochthonous (soil erosion and terrestrial plants) and autochthonous (algal and aquatic plants) in DC-S and DC-N, respectively, and primarily mixed planktonic and terrestrial in DC-E. The stochastic impacts by regression on population, affluence, and technology (STIRPAT) model revealed that a 1% increase in air temperature and nitrogen fertilizer corresponded to an increase in ONAR by 23–33% and 20–79% in the Dianchi Lake basin, especially in DC-S and DC-E. However, a 1% increase in urban land area reduced ONAR by 2–11%, especially in DC-N. Our study suggests that the spatial and temporal ONAR in Dianchi Lake may increase in response to a warmer and wetter climate combined with increasing chemical nitrogen fertilizer application.

Long-time series ecological environment quality monitoring and cause analysis in the Dianchi Lake Basin, China

As the core area in the transformation of Kunming into an international center city, studying the changes in ecological environment quality and causes of the Dianchi Lake Basin is of great significance for its future optimization of the landscape pattern. This study is based on the Google Earth Engine (GEE) platform to calculate the Remote Sensing Ecological Index (RSEI) of the Dianchi Lake Basin from 1990 to 2020. Then we used Mann-Kendall mutation detection to obtain the time points when significant changes in RSEI occurred. Finally, the Geodetector and MGWR models were combined to analyse the driving factors of ecological quality changes in the Dianchi Lake Basin. The results show that: (1) The ecological environment quality of the Dianchi Lake Basin showed an increasing trend from 1990 to 2020, with the mean value of RSEI increasing from 0.49 to 0.52. (2) According to the results of the mutation test, the years 1990, 1993, 2006, 2015, and 2020 were used as the time points for monitoring the ecological environment quality of the Dianchi Lake Basin over a long time series. The ecological environment quality of the study area in the past 30 years was mainly in an improved state, accounting for 49.43%. The ecological deterioration areas are mainly located in the northeastern part of Xishan District (north of Caohai Lake), the southwestern part of Guandu District, Kunyang Town in Jining District, and the northern areas of Jincheng and Shangsuan Town. (3) The single factor detection results show that elevation and slope have the strongest influence on RSEI. The q-value of average annual temperature has changed the most, from the 6th to the 3rd place. This indicates that the urban heat island effect and the expansion of construction land have had a greater impact on the quality of the local ecological environment in recent years. The multi-factor interaction test shows that the influence of each factor on RSEI is enhanced after the interaction. (4) The MGWR regression results show that the actual scales of action of the factors are inconsistent, with the most significant spatial heterogeneity in the Percentage of cropland area. Based on the above findings, it can provide data to support the future urban planning of the Dianchi Lake Basin. It also provides a new means of integrating Geodetector and MGWR into the study of ecological quality analysis.

Impact of Land Use/Land Cover and Landscape Pattern on Water Quality in Dianchi Lake Basin, Southwest of China

The water quality of a basin is pronouncedly affected by the surrounding types of land use. Analyzing the impact of LULC and landscape patterns on water quality is critical for identifying potential drivers. To further study how LUCC affects the water quality in a typical plateau lake basin, this study investigated the impacts of land-use types on water quality in the Dianchi Lake Basin in Southwest China. We analyzed changes in land-use types and the landscape pattern of the Dianchi basin, calculated the CWQI (Canadian Water Quality Index) value based on the water quality indexes (PH, total phosphorus (TP), total nitrogen (TN), chemical oxygen demand (COD), dissolved oxygen (DO), permanganate index (CODMn), five-day biochemical ox-ygen demand (BOD5), ammonia nitrogen (NH3-N), turbitidy, and chlorophyll-a (Chla)), used the RDA (Redundancy Analysis) and SMLR (Stepwise multiple linear regression) methods, the coupling degree, coupling coordination degree, and the geographical detector model to explore the relationship between water quality and changes in the land-use type. The results show that (1) changes in the land-use types were obvious: the majority of the land, which was originally forest land, became built land in 2020 and farmland in 1990 (except for the Dianchi water). Landscape pattern indexes indicated that almost all land-use types were first scattered, then gathered from 1990 to 2020. (2) Changes in the water quality of Dianchi Lake lagged behind the changes in land-use types, and the variation trends were similar to the landscape pattern variation trends. The CWQI value decreased in a nearly linear fashion from 1990 to 1998, exhibited a slight change from 1999 to 2013, and quickly increased from 2013. (3) Land-use types demonstrated a tight correlation with the Dianchi water quality, and LPI was the most dominant factor in both Caohai Lake and Waihai Lake. (4) There were different indexes affecting the coupling coordination degrees of Caohai Lake and Waihai Lake.

Assessment of ecosystem health based on landscape pattern in ecologically fragile regions at different spatial scales: A case study of Dianchi Lake basin, China

In the process of urbanization, maintaining ecosystem health in ecologically fragile regions is an inevitable requirement for sustainable development in the future, but the ecological health status varies greatly at different spatial scales. Determining the appropriate spatial scale of ecological health assessment is the basis and premise of ecological management and environmental protection policy making. Taking Dianchi Lake basin as the research area, based on the vigor-organization-resilience (VOR) model and landscape pattern index, this study established an assessment system of ecological health to evaluate the ecosystem health status from quadrat, ecological and administrative scales, with the aim to determine a reasonable evaluation scale and strengthen regional sustainability. The results show that: 1) The suitable spatial grain of landscape pattern analysis in Dianchi Lake basin is 150 m. 2) The average values of ecosystem health indices at quadrat scale, ecological scale and administrative scale are 0.5466, 0.4977 and 0.5373, respectively, demonstrating a sub-health state. 3) The most suitable scale for ecological health assessment of Dianchi Lake basin is ecological scale, because taking sub-watershed as ecological unit can ensure the integrity of the evaluated ecosystem to the greatest extent. Multiscale assessment is helpful for eco-environmental management departments to understand the ecosystem health status at different scales and provide a scientific basis for regional eco-environmental management decisions.

Fish Biomonitoring and Ecological Assessment in the Dianchi Lake Basin Based on Environmental DNA

Fish are among the main target groups when conducting biomonitoring and ecological assessment of aquatic environments. Environmental DNA (eDNA) metabarcoding provides a unique opportunity to enhance biomonitoring throughput, precision, and standardization. However, few fish monitoring studies based on eDNA metabarcoding have been conducted at the basin scale. Taking Dianchi Lake and the three inflowing rivers (Panlong River, Baoxiang River, and Chai River) as research objects, this study monitored fish diversity via eDNA metabarcoding, and the Fish Index of Biological Integrity (F-IBI) was constructed and applied for the ecological assessment of the aquatic environment. Here, we detected 41 species belonging to 9 orders, 15 families, and 35 genera in the sampling areas, including 17 native fish species such as Hemiculter leucisculus, Cyprinus carpio, and Silurus soldatovi. Distinct diversity patterns were observed among Dianchi Lake and the three inflowing rivers. Particularly, the fish diversity of Panlong River was richer than that of Dianchi Lake, Baoxiang River, and Chai River. Water temperature (WT), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) significantly influenced the distribution of fish communities in most sampling sites of the Dianchi Lake basin (p < 0.05). Moreover, according to the F-IBI assessment system, 25% of the sampling sites were defined as ‘fine’ or above, and 75% were ‘impaired’ or below. This study provided insights into the ecological restoration and precise management of the aquatic environment of the Dianchi Lake basin.

Effects Of Alternating Drying And Wetting On Soil Nitrogen And Phosphorus Loss In Root Zone Of Dominant Plants In Phosphorus-rich Mountainous Areas

In the mountainous area of Yunnan-Guizhou Plateau, phosphorus and nitrogen are important factors that limit primary productivity and affect the distribution of plant communities. Alternation of wet and dry has a significant effect on the migration of various elements such as C, N, and P in soil. Taking the rhizosphere soil of the dominant plants in the phosphorus-rich mountainous area in the Dianchi Lake Basin as the research object. Six sets of different humidity treatment methods: blank constant humidity, blank dry and wet alternation, nitrogen constant humidity, nitrogen addition dry and wet alternation, carbon constant humidity, and carbon add dry and wet alternation were assessed. Responses of soluble total nitrogen and soluble total phosphorus to six treatments in plant root zone were investigated. The results showed that the contents of dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) in soil leachate and their changes of Erianthus rufipilus and Eupatorium adenophorum under different treatment conditions increased first and then decreased. In the carbon addition group, the DTN content of the soil leachate in the alternating dry and wet treatment was significantly higher than that in the constant humidity treatment, but there was no significant difference in the nitrogen addition group. The three factors of water treatment and sampling time have significant effects on the DTN content of soil leachate, and the interaction between the three also has a significant effect on it. Bangladesh J. Bot. 51(4): 855-862, 2022 (December) Special

Extraction of long time series wetland information based on Google Earth Engine and random forest algorithm for a plateau lake basin – A case study of Dianchi Lake, Yunnan Province, China

Wetlands are transitional zones between terrestrial and aquatic ecosystems. They have the potential to continuously provide human beings with food, raw materials, and other substances. Also, wetland landscape pattern changes have profound impacts on the climate of plateau areas and accelerate the rate of climate change, so it is crucial to extract long time series of plateau wetland information. Concurrent with large-scale urbanization, industrial development and construction, and rapid population increases, the lakeside wetlands in the Dianchi Lake Basin are changing rapidly. However, scholars have not yet extracted long time series wetland information for this area, so the long-term evolution of these wetlands cannot be clarified. In this study, we used the Google Earth Engine (GEE) platform to extract wetland information for the Dianchi Basin from 1988 to 2020 from Landsat data and generated 33 wetland maps by applying a random forest classification model to identify trends and a confusion matrix to assess accuracy. The results showed that the overall trend of wetland area from 1988 to 2020 showed an increasing area, and the total wetland area increased by 31.11 km2 (+9.67 %). Furthermore, the overall accuracy of most years exceeded 80 %, the QADI was no higher than 0.2, the user accuracy and producer accuracy were higher than 80 % and 70 %, respectively, for swamps and water bodies, and the remaining non-wetland categories also achieved robust classification accuracy. Thus, the results of this study can compensate for the lack of information on wetland changes in the region over the past 33 years and provide data support and a scientific basis for sustainable wetland development in the plateau.

Improved export coefficient model for identification of watershed environmental risk areas.

As a complex system under the joint action of man and nature, land use/cover directly or indirectly affects the environmental quality of the freshwater ecosystem. Studying the response of water environment quality to land use/cover change was significant to accurately simulate lake water quality and effectively enhance the management level. As an empirical model, the classical export coefficient model has been widely used and developed in agricultural non-point source pollution research because of its simple structure and convenient application. However, it assumes that the export coefficient of a particular type of land use/cover was constant, ignoring the influence of surface runoff and interception on the output intensity of pollutants in pollutant migration. This study improved the classical export coefficient model by adding factors such as precipitation, surface cover, and topography, evaluated the contribution of land use/cover to total nitrogen load into the lake in Dianchi Lake Basin, and applied the pollution assessment results to the identification of watershed environmental risk areas. The results showed that the improved export coefficient model could better simulate the relationship between land use/cover and total nitrogen load into Dianchi Lake from the basin. At the same time, spatial characteristics of the total nitrogen load contribution of the terrestrial could be represented. The high-risk areas in the basin were mainly cultivated land and construction areas with low vegetation coverage around lakes or downstream. The contribution per unit area to the TN load into the lake from areas with a high risk was 14.28 t/km2, which was 3.47 times that of medium-high-risk areas and 52.28 times that of the medium-risk area. Land use control measures in high-risk areas in the basin should be further strengthened, especially in the lakeside zone.

Temporal and spatial changes in land use and ecosystem service value based on SDGs' reports: a case study of Dianchi Lake Basin, China.

Understanding the impact of land use and ecosystem services on sustainable development goals is a key to achieving sustainable development goals (SDGs). Taking Dianchi Lake Basin as the research area, land use data from five periods, 2001, 2005, 2010, 2015, and 2019, were analyzed using the dynamic equivalent method to determine ecosystem service value (ESV) and hot spot analysis method to explore temporal and spatial changes in ESV in Dianchi Lake Basin. Three sustainable development goals, SDG15.1.1, SDG15.2, and SDG15.3.1, were selected to quantitatively analyze the impact of land use change in Dianchi Lake Basin. The results showed that (1) in the 20-year study period, the main land use types in Dianchi Lake Basin were forest land, cultivated land, construction land, and water area. In the land transfer, the largest amount of land transferred out is cultivated land, accounting for 35.50% of the total transferred out amount. It is transferred to construction land, resulting in significant expansion of construction land, nearly twice as much. (2) The SDG15.1.1 index of three forest land types in Dianchi Lake Basin showed a downward trend, and the total forest land decreased from 45.36 to 41.80%, with a cumulative decrease of 3.56%, of which 2.35% was caused by the transformation from open forest land to other land types. For watershed SDG15.2 and SDG15.3.1 indicators, all were degraded, but the degradation of high forest (SDG15.2) was the most obvious. (3) From 2001 to 2019, the total ESV in Dianchi Lake Basin initially decreased and then increased before decreasing again, with an overall decrease of 3.687 billion yuan. The ESV in the study area was high in the middle and low in the periphery, and the water area dominated by Dianchi Lake was the highest value area. (4) From 2005 to 2019, the spatial displacement relationship between cold and hot spots dominated by Dianchi Lake was corresponding and obvious, during which the ESV fluctuated violently. This study provides a basis for the sustainable development and ecological construction in typical urbanized watershed.

Spatial–temporal characteristics of surface thermal environment and its effect on Lake surface water temperature in Dianchi Lake basin

The surface thermal environment plays an important role in urban sustainable development and ecological environment protection. Existing researches mainly focus on the formation process and mechanism of the surface thermal environment and lack the analysis of its effect on the lake ecological environment under the influence of human activities. Therefore, based on the analysis of the variations in land surface temperature (LST) and lake surface water temperature (LSWT) of Dianchi Lake at multiple spatio-temporal scales, this study evaluated the response of LSWT by using the methods of spatial influence, the center of gravity migration trajectory, trend analysis, and correlation analysis. The results show that: (1) Urbanization has a greater warming effect on LSWT than on LST, and the warming effect at night is greater than that at daytime. From 2001 to 2018, the warming trend of LSWT in daytime and night was 0.01°C/a and 0.02°C/a, respectively, while the cooling trend of LST in daytime was −0.03°C/a and the warming trend of LST in night was 0.01°C/a. (2) Areas with high human activity are warming faster, both in the eastern and northern coastal areas of lake and the heavily urbanized sub-basins. (3) The spatial influence of LST and LSWT are highly correlated, and the response of the outer buffer in the range of 2 km is obvious, and the direction of gravity center migration trajectory is consistent. The results are of great significance for the control and improvement of urban heat island and ecological environment protection of Dianchi Lake in Kunming and can provide data support and decision support for urban planning, promoting the construction of the ecological civilization city in Kunming, and reducing the accumulation of urban surface heat.

Distribution patterns of lake-wetland cultural ecosystem services in highland

Environmental and ecological degradation are more prominent within lake-wetland ecosystem than any other ecosystem on Earth, especially in the highlands. The continued pressures of population growth and rapid urbanization on cultural ecosystem services (CES) provided by lake-wetland ecosystem in highlands present ongoing challenges to decision-makers and managers. In this paper, Social Values for Ecosystem Services model (SolVES) was used to map, quantify and assess CES in Dianchi lake basin (DLB) and Erhai lake basin (ELB) to understand the spatial dynamics of CES perceived by residents and tourists. After combining the field survey data with four environmental variables, our analysis shows that (1) The Maximum Value Index (M-VI) ranking of the three CES in descending order within DLB was aesthetic (M-VI = 10), recreation (M-VI = 10), cultural (M-VI = 8). (2) Different stakeholders (residents and tourists) had different perceptions of CES. Recreation value between residents and tourists had the same M-VI (M-VI = 10), but the M-VI of aesthetic value (M-VI = 10) perceived by tourists was higher than those perceived by residents. (3) The four environmental variables significantly influenced CES, especially distance to water and dominant landcover. (4) CES were transferable from DLB to ELB due to the potential transferability of Maxent's DLB models for each CES, and CES hotspots in ELB generated from SolVES were highly consistent with high kernel-density areas. In conclusion, SolVES incorporating CES can benefit the basin resource managers when seeking to integrate a social perspective into the resource management decision-making process. In particular, the involvement of various stakeholders ensures that they are not marginalized in environmental planning and management.

Assessing the Terrain Gradient Effect of Landscape Ecological Risk in the Dianchi Lake Basin of China Using Geo-Information Tupu Method.

The assessment of landscape ecological risk (LER) in different terrain gradients is beneficial to ecological environmental protection and risk management in different terrain gradients. Due to the impact of urban expansion, the landscape pattern of the Dianchi Lake basin (DLB) changed obviously, resulting in significant spatial difference of LER. At present, the LER assessment of the DLB is not clear, and the evolution mechanism of LER in different terrain gradients has not been revealed. Based on the LER assessment model, the geo-information Tupu method, the terrain niche gradient, and distribution index, this paper analyzed the LER and its terrain gradient effect in the DLB of China. The conclusions are as follows: (1) Since 1995, the land use type has mainly changed from grassland and cultivated land to construction land in the DLB of China. (2) The LERs in the DLB of China were mainly low, med low, and med high due to the transformation of land use type. The dominance distribution of the low and high LER was obviously constrained by terrain gradient. While the dominance distribution of med-low LER expanded to med-high terrain gradient, the dominance distribution of the med-high LER decreased to med-low terrain gradient. (3) The Tupu LERs were mainly a stable type of “medium” risk and anaphase change type of “med-high to medium” risk. The dominant distribution regions of the stable type, the prophase change type, and the continuous change type were relatively stable; the anaphase and middle change type expanded to the higher terrain gradient, and the repeated change type decreased to the med-high terrain gradient. In the process of ecological risk management and protection in the DLB, attention should be paid to the water area structure and LER control in med-high and high terrain gradients.

Fluorescence characteristics of DOM and its influence on water quality of rivers and lakes in the Dianchi Lake basin

Dissolved organic matter (DOM) is an important part of the material cycle in the water environment, and it plays an important role in the nutrient cycle of nitrogen and phosphorus in eutrophic water and biological processes. Dianchi Lake is a heavily eutrophic plateau lake in China. To investigate the fluorescence characteristics of DOM and the influences of DOM on water quality of rivers and lakes in the Dianchi Lake basin, three-dimensional fluorescence spectroscopy and high-resolution mass spectrometry were employed to determine the features of dissolved organic matter (DOM) components. According to the research results, the DOM components in rivers and lakes in the Dianchi Lake basin were dominated by humic-like substances and affected by seasonal changes to a certain extent. DOM in Dianchi Lake is affected by the macrophytes and algae distribution as well as inflowing rivers, but the dominant factors are different in dry and rainy seasons. PCA results indicated that DOM components had relatively high relevance to water quality indicators, especially COD and TN. In conclusion, Lake ecosystem status and pollution levels can be characterized by DOM to some extent, the DOM components in the Dianchi Lake are prone to humification with the implementation of wastewater treatment and aquatic ecological restoration projects, as reflected in the improved water quality index.

Estimating the pollutant loss rate based on the concentration process and landscape unit interactions: a case study of the Dianchi Lake Basin, Yunnan Province, China

The landscape analysis model establishes a quantitative relationship between landscape patterns and pollution processes. The spatial heterogeneity within and between landscapes affects the pollutant transmission process and originates from the superposition effect of terrestrial geographical and morphological characteristics. This study aimed to develop a new method to estimate the pollutant loss rate. From the perspective of the flow process of pollutants entering a water body, the interaction between each landscape unit and adjacent unit during pollutant migration was simulated along the pollutant migration flow path. The role of pollutants affected by external forces in the process of migration could be divided into "promoting" and "hindering." Four indices were proposed to simulate the pollutant loads entering the lake. The linear coefficients between the load of the pollutants chemical oxygen demand (CODCr), ammoniacal nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP) entering the lake and the pollutant load emission weighted by the upstream and downstream confluence ratio index were 0.930, 0.835, 0.925, and 0.795, respectively, and the non-linear variance explanation coefficients were 87.70%, 87.50%, 87.60%, and 84.70%, respectively. When the surface resistance was integrated into the index as a parameter, the linear and nonlinear correlation coefficients were significantly improved. The linear coefficients were 0.952, 0.897, 0.919, and 0.939, respectively, and the non-linear variance explanations were 99.00%, 97.30%, 95.10%, and 97.30%, respectively. The spatial distribution of landscape surface resistance reflects the spatial movement trend of pollutants from different sources. The indices characterizing the promoting and hindering effects could be integrated to calculate the loss rate of pollutant load entering the lake from landscape units at different locations in the basin space.

Application of combined QSAR-ICE models in calculation of hazardous concentrations for linear alkylbenzene sulfonate

Linear alkylbenzene sulfonate (LAS) is a widely used anionic surfactant that exists as a mixture of various homologous structures in water environment. In the calculation of hazardous concentrations of LAS, cross-taxonomies toxicity estimation was often used instead of species-level-specific estimation for the normalization of toxicity data, which led to substantial uncertainties. In this study, combined quantitative structure–activity relationship (QSAR) and interspecific relationship estimation (ICE) models were developed to normalize the alkyl chain length of toxicity data and calculate the 5th percentile hazard concentrations (HC5s) of LAS. Using seven acute QSAR models based on measured data and 29 acute QSAR-ICE models derived from them, the acute HC5s of LAS were calculated as 2.09–3.67 mg/L. Furthermore, species- and family-level-specific QSAR and QSAR-ICE models were used to calculate chronic HC5s (0.19–0.38 mg/L). Additionally, the sensitivity of biological toxicity to the hydrophobicity of LAS, represented by the slope of the QSAR models, had a significant correlation with the taxa of the species. Further risk assessment based on chronic HC5s showed potential ecological risks in the Dianchi Lake basin and Haihe River basin in China, which should cause concern.

Study on the threshold relationship between landscape pattern and water quality considering spatial scale effect-a case study of Dianchi Lake Basin in China.

It is of great significance to analyze the threshold relationship between landscape pattern and water quality for watershed water environment treatment. However, previous studies did not consider the influence of spatial scale on threshold. Therefore, this study proposed the idea of the relationship between landscape pattern and water quality threshold considering the spatial scale effect to solve the above problems. Firstly, the percentage of landscape composition area under 9 spatial scales (riparian buffer zone and sub-basin) of 20 rivers entering the lake in Dianchi Lake Basin was extracted to identify the optimal spatial scale of landscape pattern and water quality by redundant analysis (RDA). Then, a variety of nonlinear regression models such as power regression, exponential regression, quadratic regression, and segmented regression are used to quantitatively detect the thresholds of landscape pattern and water quality. The results show that (1) the spatial scale has a significant influence on the threshold relationship between landscape pattern and water quality, and the total interpretation rate of landscape pattern on water quality is the largest at the buffer scale of 1100m riparian zone, which is an effective buffer for river governance. (2) Different spatial scales have different effects on the threshold relationship between landscape pattern and water quality. In the nonlinear regression model of landscape pattern and water quality in the buffer zone of 1100m riparian zone, the significance and R2 of the equation are better than those of the sub-basin. (3) From the nonlinear relationship between landscape pattern and water quality, it is found that the landscape threshold can be quantitatively identified when the water quality changes abruptly or reaches the I ~ V water quality standard. Among them, the type-1 landscape threshold at the water quality mutation point can be used as the long-term goal of water quality protection in Dianchi Lake Basin, and the type-2 landscape threshold can be used as the short-term goal of water quality adjustment. The research results can provide a scientific basis for the governance of water environment and the rational planning of landscape pattern in Dianchi Lake Basin, and have practical significance for guiding the sustainable development of cities.