Chaohu Lake Basin Research Articles

Mosaic pattern of sustained rice domestication and its environmental and cultural implications in Neolithic East China

China is one of the main locations in which rice agriculture occurs, with East China now playing a significant role in research on rice domestication and culture interactions. However, the exact timing of sustained rice domestication and the process of prehistoric cultural exchange in East China remain unclear. Here, we present phytolith records of two profiles from Lingjiatan in the Chaohu Lake Basin. Our results show that rice cultivation was practiced throughout the Lingjiatan culture period (5800-5300 cal BP), and that sustained rice domestication began around 5500 cal BP, which was later than on the Taihu Plain (∼6200 cal BP), Ningshao Plain (∼5800 cal BP), and along the middle and lower Huai River (∼5800 cal BP). Combining other archaeological records and geomorphological features in East China, we hypothesize three possible routes for the spread of rice cultivation and cultural exchange between the lower Yangtze River and the middle and lower Huai River. Lingjiatan, situated at the intersection of two of the possible routes, experienced a gradual increase in its settled population as a result of cultural exchange and technological innovations in cultivation, thereby giving rise to its distinctive culture. This study demonstrates the significant role of Lingjiatan in facilitating transportation and fostering cultural exchange in East China during the mid-Holocene.

Study on the characteristics and scenario simulation of land use change in the Chaohu Lake Basin, China

Effectively evaluating the historical and future land use/cover change (LUCC) is significant for effective land use planning and management, ecological conservation, and restoration. Taking the Chaohu Lake Basin (CLB) as the study area, GIS technology and geographic detector were used to quantitatively analyze the change characteristics and driving factors of LUCC under the three periods in 2000, 2010, and 2020 of the CLB. This study aimed to comprehend the alterations that have transpired over the last two decades. In addition, the PLUS model was utilized to forecast LUCC trends under three scenarios: natural development, urban development, and ecological protection by 2030 in the CLB. The results suggest a significant decrease of the cultivated land area, while a considerable increase for the construction land area from 2000 to 2020 in the CLB. The expansion of the construction land area was mainly driven by the conversion of cultivated land area. Additionally, the slope was identified as the primary factor influencing LUCC, with q-values of 0.275, 0.266, and 0.258 in 2000, 2010, and 2020, respectively. The interaction between slope and soil type, distance to the trunk road and the secondary trunk road, and GDP was strong. The explanatory capacity of socioeconomic factors demonstrated a steady increase. The simulation results indicate that a decrease in cultivated land area and an increase in construction land area still occurred by 2030 in the CLB, particularly in the urban development scenario. Nonetheless, a notable deceleration of change was appeared in the ecological protection scenario. The alterations in forest and grassland areas were not significant. However, the water bodies area continued to enlarge, although the expansion was not substantial. The study results can provide policy references for the scientific management and long-term strategic planning of land resources in the CLB.

A dataset of climate and productivity elements in Chaohu Lake Basin from 1861 to 2010

A dataset of climate and productivity elements in Chaohu Lake Basin from 1861 to 2010

Effects of season and water quality on community structure of planktonic eukaryotes in the Chaohu Lake Basin.

Analyzing the correlation between planktonic eukaryotic communities (PECs) and aquatic physicochemical parameters (APPs) provides important references for predicting the impact of climate change and human activities on aquatic ecosystems. To assess the influence of seasons and APPs on PEC structures in lakes and rivers, we utilized high-throughput sequencing of the 18S rRNA gene to analyze PEC structures in a lake and seven rivers in the Chaohu Lake Basin and analyzed their correlations with APPs. Our results revealed that PEC structure was significantly affected by season, with the highest α-diversity observed in summer. Furthermore, we identified several APPs, including water temperature, conductivity, dissolved oxygen, pH, phosphate, total phosphorus, trophic level index (TLI), nitrate, ammonia nitrogen, and total nitrogen, that significantly influenced PEC structures. Specifically, we found that Stephanodiscus hantzschii, Simocephalus serrulatus, Cryptomonas sp. CCAC_0109, Pedospumella encystans, Actinochloris sphaerica, Chlamydomonas angulosa, Gonyostomum semen, Skeletonema potamos, Chlamydomonas klinobasis, Pedospumella sp., and Neochlorosarcina negevensis were significantly correlated to TLI, while Limnoithona tetraspina, Theileria sp., and Pseudophyllomitus vesiculosus were significantly correlated to the water quality index (WQI). However, our random forest regression analysis using the top 100 species was unable to accurately predict the WQI and TLI. These results provide valuable data for evaluating the impact of APPs on PEC and for protecting water resource in the Chaohu Lake Basin.

Correlations of chemical weathering indicators with major chemical constituents in sediments to obtain palaeoclimate information from Chaohu Lake, China

The main chemical compositions of 201 surface sediments and 53 deep sediment samples from Chaohu Lake, China, were analysed. Since the surface sediments (0–2 cm depth) in Chaohu Lake are modern sediments, this paper mainly focuses on the deep sediments (50–100 cm depth) in Chaohu Lake. Particle size analysis and magnetization determination of the CH3 and CH4 column sediment samples were carried out. The age determination data of the CH-1 column sediment samples are reported. A systematic study of the rocks and their chemical compositional characteristics in the Chaohu Lake Basin was also carried out. The results of this study show that four positive chemical weathering indicators and one negative chemical weathering indicator are applicable to the study of Chaohu Lake. The mean CIA of the Chaohu Lake sediments was less than 65, indicating that the Chaohu Lake Basin experienced weak chemical weathering and that the palaeoclimate was cold and dry. Vertical variations in the mean grain size and magnetization in the CH3 and CH4 columnar sediments reflect changes in the depositional environment and climate during deposition of the Chaohu Lake sediments. The age data from the CH-1 column sediment samples directly indicate deposition of the deep sediments in Chaohu Lake during the Little Ice Age in eastern China (AD 1380–1880). The Th/U, Sc/Th, Rb/Sr, Na2O/K2O, CaO/MgO and OC/N ratios of the Chaohu sediments reflect palaeoclimate characteristics and the chemical compositions of the source rocks in the Chaohu Lake basin. The correlations of the CIA, CIW, PIA, and CIX with the chemical compositional ratios provide information on the palaeoclimate and the distribution of the chemical compositions. The CIA, CIW, PIA, and CIX were not correlated with Cd, Pb, As, Hg, or P. In contrast, the CIA, CIW, PIA, and CIX were significantly positively correlated with Cr and N. The WIP was inconsistently correlated with the selected chemical components. Therefore, the study of the correlations of chemical weathering indicators with four heavy metals and two eutrophication-related elements is of little significance. The study of the chemical weathering characteristics of deep sediments of inland lakes should be combined with assessment of the geological characteristics of the lake basins, particularly the analysis of the chemical composition of the rocks in the lake basins.

Partial Substitution of Nitrogen Fertilizer with Biogas Slurry Increases Rice Yield and Fertilizer Utilization Efficiency, Enhancing Soil Fertility in the Chaohu Lake Basin.

To investigate the effects of biogas slurry substitution for fertilizer on rice yield, fertilizer utilization efficiency, and soil fertility, a field experiment was conducted on rice-wheat rotation soil in the Chaohu Lake Basin for two consecutive years, with the following six treatments: no fertilization (CK), conventional fertilization (CF), optimized fertilization (OF), biogas slurry replacing 15% of fertilizer (15% OFB), biogas slurry replacing 30% of fertilizer (30% OFB), and biogas slurry replacing 50% of fertilizer (50% OFB). The field experiment results showed that, compared with CF treatment, OF treatment in 2022 and 2023 significantly increased (p < 0.05) rice yield, promoted the uptake of nitrogen (N), phosphorus (P), and potassium (K) by grains and straws, improved fertilizer utilization efficiency, and increased the contents of soil organic C (SOC), NH4+-N, NO3--N, hydrolysable N, and available P. The 15% OFB and 30% OFB treatments significantly increased (p < 0.05) rice grain and straw yields compared with CF treatment, and rice grain and straw yields were the highest in the 30% OFB treatment. Compared with CF and OF treatments, 30% OFB treatment significantly increased (p < 0.05) the N, P, and K uptake of grains and straws and increased the fertilizer utilization efficiency. Compared with CF treatment, the grain yield of 50% OFB treatment was significantly decreased (p < 0.05) in 2022, and there was no significant difference in 2023, which may be because the biogas slurry was applied before planting in 2023 to provide more nutrients for early rice growth. Compared with CF treatment, 30% OFB treatment significantly increased (p < 0.05) the contents of SOC, NH4+-N, available K, and hydrolysable N. In summary, optimizing N and K topdressing methods can increase rice yield and improve the fertilizer utilization efficiency and soil fertility. The 30% OFB treatment resulted in the highest rice yield, fertilizer utilization efficiency, and improved soil fertility, indicating that biogas slurry replacing 30% of fertilizer was the best application mode for rice in this region.

Occurrence and risk assessment of endocrine-disrupting chemicals in wastewater treatment plants in the Chaohu Lake Basin

Introduction: Endocrine-disrupting chemicals (EDCs) in effluent and residual sludge from wastewater treatment plants (WWTPs) pose significant environmental and human health risks due to their persistence, bioaccumulation, and difficulty in detection and degradation. This study investigates the environmental exposure and risks associated with EDCs in effluent and sludge from four WWTPs: Tangxi River (TXH), Zipeng Mountain (ZPS), Lianxi (LX), and Wang Xiaoying (WXY).Methods: Environmental exposure indexes of EDCs were assessed in the effluent and sludge of the four WWTPs across four seasons (spring, summer, autumn, and winter) from October 2017 to October 2018. Detection rates of various pollutants, their seasonal and spatial characteristics, and removal rates were analyzed. Positive matrix factorization (PMF) was used for source analysis under influent data, and an ecological risk assessment was conducted using the risk quotient (RQ) method.Results: The study found 4-n-nonylphenol (NP) and di-2-ethylhexyl phthalate (DEHP) had 100% detection rates in the effluent of all four WWTPs, while only DEHP showed a 100% detection rate in the sludge. Bisphenol A (BPA) exhibited the highest concentration in the TXH effluent during autumn. Benzo(a)pyrene (B(a)P) was detected only in the sludge during spring and summer and in the effluent of TXH and WXY. PMF source analysis indicated industrial wastewater discharge as the primary source of pollutants. Ecological risk assessment revealed a high RQ for estriol (E3) in TXH effluent during autumn, and DEHP presented a potential carcinogenic risk through drinking water.Discussion: The findings highlight significant seasonal and spatial variations in EDC concentrations and removal rates across the WWTPs. The persistent presence of DEHP and the high-risk levels of E3 in specific seasons underscore the need for improved treatment processes and stricter industrial discharge regulations to mitigate EDC-related risks. Further research is recommended to explore advanced detection and degradation techniques for EDCs in WWTPs.

Effect of Integrated Landscape Characteristics Around Chaohu Lake on River Water Quality Based on Watershed Units

Considering the impact of differences in watershed characteristics on river water quality, with the Chaohu Lake Basin as the research object, based on the data of water quality, meteorology, topography, soil, and remote sensing images of the river monitoring points from October 2019 to September 2020, the watershed unit at each monitoring point was divided through digital terrain analysis, and the comprehensive landscape characteristics based on the watershed unit were explored through the comprehensive use of correlation analysis, redundancy analysis, and multiple regression analysis to investigate the influence of comprehensive landscape characteristics based on watershed units (including land use, climate, topography, soil, etc.) on the water quality of rivers around Chaohu Lake. The results showed that:① the water quality of rivers around Chaohu Lake had large spatial differences, with the main pollutants being total nitrogen and ammonia nitrogen. Most of the rivers had total nitrogen concentrations exceeding the Class V water quality standards, and the areas with serious nitrogen and phosphorus pollution were concentrated in the urban area of Hefei and the surrounding rivers, as well as in the middle and lower reaches of the Fengle and Hangbu Rivers. ② The comprehensive landscape characteristics of the watershed unit had a significant impact on the river water quality. Among them, the proportion of built-up land, the density of patches, the dispersion and juxtaposition index, and the Shannon diversity index were positively correlated with the water quality indicators, whereas the proportion of forest and grassland and the spreading index were negatively correlated with the water quality indicators. ③ In different seasons, the effect of the integrated landscape characteristics of the watershed unit on river water quality was stronger in the wet season than in the dry season, which was mainly caused by the difference in precipitation in the dry and wet seasons.

Remote retrieval of dissolved organic carbon in rivers using a hyperspectral drone system

ABSTRACT Rivers act as the principal channels for transporting terrigenous dissolved organic carbon (DOC) to lakes and reservoirs. Satellite remote sensing-based river monitoring is difficult due to the narrow river form and high spatiotemporal heterogeneity of DOC components. The unique advantages of unmanned aerial vehicles (UAVs) facilitate river DOC concentration monitoring. The DOC concentration in 8 major tributaries (average width: 109.62 m) and shoreside of the Lake Chaohu Basin were retrieved via a hyperspectral UAV. The results showed that (1) the DOC concentration was significantly correlated with the water remote sensing reflectance ( R rs ) of 402, 429-438, 440–451 and 458–462 nm in the blue band (r2: 0.11 to 0.13; p<0.05), and 620–621 and 623–693 nm in the red band (r2: 0.12 to 0.20; p<0.05). The water quality parameters chlorophyll-a (Chl-a) and suspended particulate matter (SPM) and environmental parameters wind speed and temperature 3 days delay sampling date, also showed a significant correlation. (2) The random forest regression (RFR) model attained the best performance (r2: 0.64; RMSE: 0.30 mg/L; MAPE: 7.02%). (3) DOC concentration in Lake Chaohu Basin was highest in the northeast (8.19 mg/L), followed by the northwest and west (7.13 mg/L), and it was lowest in the south (6.70 mg/L).

Differential responses of ecosystem stability to climatic and anthropogenic factors in connected and isolated lake basins on the Yangtze River

Maintaining optimal ecological security in the Yangtze River-connected and isolated lake basins is of great significance to national projects involving Yangtze River protection. Ecosystem stability and associated factors are important components of ecological security in these basins. However, few studies have focused on ecosystem stability and its driving factors over long periods in the Yangtze River Basin. In this study, a remote sensing index was used to analyze the spatiotemporal variation in the ecosystem stability of the Dongting Lake Basin (DTL), Poyang Lake Basin (PYL), and the isolated Chaohu Lake Basin (CHL) and Taihu Lake Basin (THL) in the Yangtze River over the period 2000–2022 to determine the potential affecting factors. The results showed fluctuations in the ecosystem stability of the DTL and PYL, while a V-shape was observed for the CHL and THL during the same period; the closer to the lake, the weaker the stability of the ecosystem, especially in the DTL and PYL. Moreover, the ecosystem stability was greater in the DTL and PYL than in the CHL and THL. The spillover effect of anthropogenic activities on the ecosystem stability of the four basins and the direct effect of temperature have the greatest effect on the ecosystem stability. Specifically, the ecosystem stability index for the area around the DTL and PYL decreased with increasing human interference, whereas the opposite was observed in the CHL and THL. The effect of temperature was negative for the ecosystem stability of DTL and PYL and significantly positive for CHL and THL, at a level of 0.01 %. The findings of this study provide significant information for targeted ecological restoration of the Yangtze River Basin.

Temporal and Spatial Trends in Livestock Manure Discharge and Water Pollution Risk in Chaohu Lake Basin

Assessments of the spatiotemporal distribution of livestock manure and its risk to the watershed are important to prevent water pollution. In this work, the spatiotemporal livestock manure distribution and its risk for the Chaohu lake basin were evaluated based on the excretion coefficient method and ArcGIS technology. In detail, the amounts of livestock manure and its associated pollutants, including chemical oxygen demand (COD), five-day biochemical oxygen demand (BOD5), ammonia (NH4+-N), total nitrogen (TN), and total phosphorus (TP), were calculated from 2009 to 2019. Then, the diffusion concentrations of COD, BOD5, NH4+-N, TN, and TP and the water pollution risk index from livestock manure were estimated and predicted for the Chaohu lake basin. The results indicated that the mean amount of livestock manure had reached 1.04 × 107 t in the Chaohu lake basin in the studied decade. The COD, BOD5, NH4+-N, TN, and TP from livestock manure in Feixi and Feidong contributed 54.26% and 54.40% of the total in the whole basin. These results demonstrate the potential pollution risk of livestock manure for the Chaohu lake basin. Moreover, the diffusion concentrations of COD, BOD5, NH4+-N, TN, and TP for the lake basin were from highest to lowest as follows: Feixi &gt; Feidong &gt; Chaohu &gt; Lujiang &gt; Wuwei &gt; Shucheng &gt; Hefei. The water pollution risk index was more than 20 in Feixi and Feidong, indicating that these areas were heavily affected by local livestock manure. The water pollution risk index will be approximately 18 for the Chaohu lake basin in 2030, implying that the Chaohu lake watershed will suffer moderate pollution from animal manure. These results provide scientific support for policymakers to enhance manure utilization efficiency and control livestock manure loss, causing water eutrophication in Chaohu lake basin or other similar watersheds.

Evaluating Effects of Nitrogen and Phosphorus Discharges under Different Reduction Scenarios: A Case of Chaohu Lake Basin, China

Determining the amount of nitrogen (N) and phosphorus (P) discharged into lakes and assessing the effectiveness of reduction measures in a basin that involve the interaction of multiple factors are still daunting challenges. In this study, the random forest (RF) model was employed to simulate the impact of controlling measures on the amount of N and P discharged in 2025 under seven specific reduction scenarios. Discharged N and P decreased in the basin by 23.38% and 31.69% from 2011 to 2020, respectively. The N and P nutrient discharge intensities were significantly higher in the western part of the basin (13.31 kg·ha−1·a−1 and 1.34 kg·ha−1·a−1) than those in the eastern region (10.24 kg·ha−1·a−1 and 0.74 kg·ha−1·a−1). Fertilizer runoff (N: 34.72%, 5934.49 t; P: 13.60%, 199.76 t), domestic sewage (N: 29.14%, 4009.27 t; P: 34.84%, 496.59 t), and livestock farming (N: 15.11%, 2657.50 t; P: 40.05%, 616.05 t) were the key sources of N and P. The RF model shows that (R2 &gt; 0.994, p &lt; 0.01) the multi-factor reduction effect is the best, and under this discharge reduction effect, the amount of N and P discharged in 2025 are expected to decrease by 13.79% and 19.42%, respectively, compared with those in 2020. In addition, different key sources in sub-basins might lead to regional differences in the discharge reduction effects of various measures. Ultimately, we recommend that the synergistic treatment of point and non-point sources, using treatments with multiple measures, should be implemented in different regions to reduce the amount of N and P discharged in the Chaohu Lake Basin.

Spatial and Temporal Dynamic Changes and Influencing Factors of Ecological Environmental Quality in Chaohu Lake Basin Based on GEE

Spatial and Temporal Dynamic Changes and Influencing Factors of Ecological Environmental Quality in Chaohu Lake Basin Based on GEE

Dissolved organic matter and Fe/Mn enhance the combination and transformation of As in Lake Chaohu Basin

The phenomenon of algal blooms resulting from lake eutrophication has the potential to increase the concentration of dissolved organic matter (DOM) and consequently influence the environmental behaviour of arsenic (As). In the subtropical region, the interplay between DOM, Fe/Mn and As becomes complex as Fe/Mn-rich substances from soils and sediments enter eutrophic lakes. The mechanisms by which DOM-Fe/Mn interactions affect the transformation of As species remain uncertain. Therefore, the Chaohu Lake Basin was selected as a representative case study site to investigate the levels of DOM, As, Fe and Mn in the water and to establish their associations. In addition, the interaction mechanism between DOM-Fe/Mn and As was investigated by elucidating the transformation behaviour of DOM-Fe/Mn on As species in a controlled laboratory environment. The results showed that in cases where the coexistence of Fe and Mn concentrations was relatively low (e.g. Fe < ∼0.5 mg/L and Mn < ∼0.6 mg/L), the concentration of As in water would increase proportionally with the simultaneous increase of both Fe and Mn concentrations (As < 5 μg/L). However, when the concentration of either Fe or Mn reached 10 mg/L, the proportion of As complexed by DOM increased significantly, reaching 99.73% and 99.66%, respectively. In the configuration of a metallic bridge, the elements Fe and Mn act as connectors between negatively charged DOM and As, thereby increasing the adsorption capacity of DOM for As. The alcohol and alkene functional groups present on the DOM-Fe/Mn surface show a preference for binding with free species of As in aqueous environments. In addition, the reductive groups on the surface of DOM not only directly convert As(V) to As(III), but also facilitate the reduction of Fe(III) to Fe(II), resulting in the indirect conversion of As(V) to As(III). Thus, this study provides a comprehensive understanding of the transport and transformation processes of arsenic in subtropical eutrophic lakes.

Improving in-stream nutrient retention potential through factitious manipulation: the stepping stone structures of flying-geese pattern and their reinforcement structures.

Small streams are essential parts of water ecosystems, such as rivers, lakes, and reservoirs, performing vital functions in the attenuation of nutrient pollution. As eutrophication becomes an increasingly severe problem in waters, it is necessary to investigate how to improve nutrient retention potential in streams. In this study, the effect of artificial manipulation was examined on transient storage and nutrient uptake in streams by setting up the stepping stone structures of flying-geese pattern (SG) and the combination mode of SG and bilaterally staggered spur dikes (SG+SD) in the channel. The tracer experiments were performed to confirm the effectiveness of SG and SG+SD in two headwater streams, which are tributaries of the Chaohu Lake basin. Additionally, the transient storage and nutrient uptake potential were assessed by the OTIS (one-dimensional transport with inflow and storage) model and the nutrient spiraling theory. Compared with the control, the implementation of SG in the Banqiao River increased the retention of ammonium (NH4+) and phosphate (PO43). Furthermore, the transient storage capacity and nutrient uptake potential in the Ershibu River were strengthened with the addition of bilaterally staggered spur dikes based on SG. These results highlight the importance of manipulating the geomorphology of the streambed to enhance the nutrient retention potential in streams.

Spatial scale effects of integrated landscape indicators on river water quality in Chaohu Lake basin, China.

Climate change and rapid urbanization have changed the characteristics of basin landscapes. Non-point-source (NPS) pollution affects river water quality. Exploring the impact of landscapes on river water quality is crucial for the control of water pollution in a basin. Current researchers focus on the impact of landscape pattern change on NPS pollution in the basin, but few consider climate, terrain, soil, and other geographical factors. In this study, we selected a subtropical agricultural basin in China named Chaohu Lake basin as the study area, added precipitation, soil erosion resistance, and slope to the original landscape pattern indicators. We quantified the spatial scale effect and seasonal dependence of integrated landscape indicators on water quality and comprehensively analyzed the optimal spatial scale and key landscape indicators. According to the nonlinear relationship between the key landscape indicators and river nutrients, we also determined the Type-1 threshold values of key landscape indicators for water quality protection in the basin. The results showed that the rivers in Chaohu Lake basin were mainly polluted by nitrogen and phosphorus. The strength of interpretation of the integrated landscape indicators of river water quality increased with riparian zone width. We determined the subbasin scale to be the optimal spatial scale. The key landscape indicators affecting water quality in the wet season at the optimal scale were precipitation and aggregation index of construction land (AIbul), whereas those in the dry season were AIbul and COHESION. The interpretation of the key landscape indicators in the wet season was slightly higher than that in the dry season. The above conclusions provide a scientific reference for NPS pollution control and water quality protection in subtropical agricultural basins.

Will agricultural land scale management aggravate non-point source pollution? – Chaohu Lake Basin, China as a case study

In this study, we investigated the relationship between scale management and non-point source (NPS) total phosphorus (TP) load in Chaohu Lake Basin. We used agricultural point of interest (POI) density to characterize scale management and employed the Soil and Water Assessment Tool (SWAT) model for simulations. Our findings in 2018 showed that there was a segmented relationship between agricultural POI density and TP load in townships. Significant negative correlations between POI density and TP load were observed in medium-density (0.076 < POI<0.172) and high-density (POI>0.172) scale management townships, but not in low-density (POI<0.076) townships. The slope coefficient for high-density townships was approximately one-tenth of that for medium-density townships, indicating the prevalence of agricultural land scale management at only a certain density can effectively inhibit NPS TP emissions, and this inhibitory effect has a marginal diminishing effect. These observations also applied to vegetable, fruit, and flower nurseries bases. Notably, low-density scale management of farms still had a significant inhibitory effect on TP load. However, scale management of forest farms and tea plantations did not inhibit TP loads due to the influence of high natural background phosphorus content, low hills with large gradients, and low POI density.

Water quality variation and driving factors quantitatively evaluation of urban lakes during quick socioeconomic development

Rapid urbanisation has caused a significant impact on the ecological environment of urban lakes in the world. To maintain the harmonious development of urban progress and water quality, it is essential to evaluate water quality variation and explore the driving factors quantitatively. A comprehensive evaluation method with cluster analysis and Kriging interpolation was used to explore the spatiotemporal variation in a typical urban lake in China, Chaohu Lake, from 2011 to 2020. The correlation between water quality and socioeconomic factors was evaluated by Pearson correlation analysis. Results indicated that: total phosphorus (TP) and total nitrogen (TN) were the key pollution parameters of Chaohu Lake. The pollution situation was gradually improving, however, and the improvement in chemical oxygen demand (COD) is more evident due to anthropogenic control. The spatial heterogeneity of water quality in Chaohu Lake is remarkable, and the water quality is poor in the west but better in the east. Natural attributes of lakes and external load were the main reasons for the spatial heterogeneity. The western residential areas of Chaohu Lake Basin (CLB) are concentrated, and a large amount of industrial and domestic sewage exacerbates water pollution in the west of tributaries. In contrast, the implementation of water environmental governance policies in recent years has alleviated water pollution. From 2011 to 2020, water quality has improved by 23%–35% in the west and 7%–14% in the east. This study provided a framework for quantitatively assessing water quality variation and its driving forces in urban lakes.

Method for screening water physicochemical parameters to calculate water quality index based on these parameters’ correlation with water microbiota

Water quality index (WQI) plays a crucial role in guiding water resource management. However, WQI calculation methods are not uniform, especially the selection of water parameters and the weighting given to each water parameter (Pi). To optimize WQI calculation, 132 water samples from seven rivers and from Chaohu Lake (33 sampling sites in Chaohu Lake Basin) in four seasons were collected, and the water parameters and microbiota composition were analyzed using high-throughput sequencing of 16 S rDNA. The correlation coefficient R2 between water parameters and microbiota composition using redundancy analysis with the Monte Carlo method were calculated, and the water parameters that significantly correlated with the microbiota composition were selected to calculate WQImin. The results showed that TP, COD, DO, and Chl a correlated significantly with water microbiota composition. WQIb calculated by substituting R2 for Pi was more consistent with the similarity between the microbiota compositions. WQIminb calculated using TP, COD, and DO was consistent with WQIb. The results of WQIb and WQIminb were more consistent than those of WQI and WQImin. These results imply that using R2 instead of Pi could help obtain a more stable WQIb that could better reflect the biological characteristics of the Chaohu Lake Basin.

Initial Studies on the Effect of the Rice-Duck-Crayfish Ecological Co-Culture System on Physical, Chemical, and Microbiological Properties of Soils: A Field Case Study in Chaohu Lake Basin, Southeast China.

Rice-duck and rice-crayfish co-culture patterns can increase soil productivity and sustainability and reduce the use of chemical pesticides and fertilizers, thereby reducing the resulting negative environmental impacts. However, most studies have focused on the rice-duck and rice-crayfish binary patterns and have ignored integrated systems (three or more), which may have unexpected synergistic effects. To test these effects, a paddy field experiment was carried out in the Chaohu Lake Basin, Hefei city, Southeast China. Four groups, including a rice-duck-crayfish ecological co-culture system (RDC), idle field (CK), single-season rice planting system (SSR), and double-season rice planting system (DSR), were established in this study. The results showed that the RDC improved the soil physical properties, fertility, humus content, and enzyme activity. In the RDC system, the soil total nitrogen content ranged from 8.54% to 28.37% higher than other systems in the 0-10 cm soil layer. Similar increases were found for soil total phosphorus (8.22-30.53%), available nitrogen (6.93-22.72%), organic matter (18.24-41.54%), urease activity (16.67-71.51%), and acid phosphatase activity (23.41-66.20%). Relative to the SSR treatment, the RDC treatment reduced the total losses of nitrogen and phosphorus runoff by 24.30% and 10.29%, respectively. The RDC also did not cause any harm to the soil in terms of heavy metal pollution. Furthermore, the RDC improved the yield and quality of rice, farmer incomes, and eco-environmental profits. In general, the RDC can serve as a valuable method for the management of agricultural nonpoint-source pollution in the Chaohu Lake area and the revitalization of the countryside.