Chaohu Lake Basin Research Articles

Co-occurrence characteristics of antibiotics and estrogens and their relationships in a lake system affected by wastewater.

Antibiotics and estrogens are recognized as emerging contaminants in the water environment because of their potentially adverse effects on aquatic ecosystems. The concentrations of four steroid estrogens (17α-estradiol, 17β-estradiol, estrone, and estriol) and eight antibiotics (norfloxacin, levofloxacin, ciprofloxacin, enrofloxacin, metronidazole, sulfapyridine, doxycycline, and sulfamethoxazole) in the Chaohu Lake basin in Anhui province, China, were analyzed along with adjacent wastewater. The levels of the target antibiotics and estrogens were below detection limits (not detected [nd])-89.86 and nd-118.09ng L-1 , respectively, in the lake water. All of the target antibiotics and estrogens were detected in sediment, and the concentrations ranged widely (nd-35,544 and nd-16,344ng kg-1 , respectively). Antibiotics and estrogens varied spatially in the study area and mostly came from untreated wastewater. Antibiotics and estrogens were associated with water parameters such as pH and total nitrogen. A significant positive correlation was observed between estriol and levofloxacin concentrations (r=.65; p<.01), indicating that levofloxacin from the same source might have inhibited the microbiological degradation of estriol in the surface water. Overall, the estrogens pose a more severe risk than antibiotics to the Chaohu Lake system. However, co-occurrence of antibiotics may affect the fate of estrogens in the same lake media. More attention should be given to estrogens than to antibiotics in wastewater-affected lake systems.

Quantitative assessment of the drainage morphometric characteristics of Chaohu Lake Basin from SRTM DEM Data: a GIS-based approach

ABSTRACT This study is focused on the morphometric evaluation of some hydrological parameters of the streams/rivers in Chaohu Lake Basin and its influence on land-use changes in the basin. The hydrological parameters considered here include drainage network, linear morphometric, areal, and relief parameters as well as the focal statistics of the stream variables in the Chaohu Lake catchment. Morphometric analyses and assessments of the basin were carried out (in ESRI©ArcGIS 10.6.3) utilizing the remotely sensed georeferenced Digital Elevation Model (DEM) data obtained from Shuttle Radar Topographic Mission (SRTM) while the land-use change analyses (executed in ESRI© ArcGIS) was based on Maximum Likelihood supervised Classification (MLC) of subsets of Landsat MSS and OLI/TIRS images acquired in 1979 and 2015. Linear morphometric results from the analyses include river and stream length (18.22 km), stream order (1–4), mean stream length (0.01 km), bifurcation ratio (2.11–4.34) and mean bifurcation ration (2.15) respectively. The areal morphometric attributes extracted include drainage density (670.85 km2), basin perimeter (789.3 km), basin area (13,350 km2), Circularity ratio (Rc, 0.0059) and relief aspects with the highest value at 1.282 m and the lowest elevation at −7 m. The drainage system here is designated as the fourth-order stream of a majorly dendritic pattern which may be a result of the structural and geomorphological influence on the stream system. In this study, the analyses and understanding of the dynamics of the different streams in the basin are shown to indicate the easy accessibility to the abundant freshwater systems in the basin which has contributed to the changes in land-use patterns over the last five decades in the basin. The notable changes include the increase of agricultural lands from 29.8% in 1979 to 45.2% in 2015; and the built-up (urban) areas from 3.5% in 1979 to 25.1% in 2015, respectively.

Investigation and Analysis on Rural Domestic Sewage Discharge in Key Watersheds

In order to grasp the latest changes in the quality and quantity of domestic sewage in the Taihu Lake Basin and Chaohu Lake Basin, and to scientifically guide the construction of rural sewage treatment demonstration projects, two typical villages were selected from Taihu Lake Basin and Chaohu Lake Basin respectively for fieldwork continuous monitoring of sewage water quality and quantity. The results show that the typical rural per capita daily drainage in the plain area of the Taihu Lake Basin in summer is 89.4 L·cap−1·d−1, which is significantly higher than that in the typical rural area of the Chaohu Lake Basin (56.5 L·cap−1·d−1). The amount of sewage hourly discharge fluctuated distinctly, and the coefficient of variation of sewage discharge in the two villages ranged from 2.4 to 6.1, showing obvious characteristics of “morning and evening peaks” or “morning, noon and evening peaks”. In addition, the rural sewage water quality in the two places shows the same pattern, and the pollutant concentration of sewage from different sources is significantly different. It was found that the toilet-flush sewage in Wangjiatang village provided 84.42% of TN and 92.94% of NH4 +-N in the total domestic sewage, while toilet-flush sewage in Qianying village provided 74.31% of TN and 84.56% of NH4 +-N in the total domestic. Therefore, when constructing a sewage treatment demonstration project, the ideological principles of sewage classification and treatment from the source should be considered.

Correction to: Water pollution characteristics and analysis of Chaohu Lake basin by using different assessment methods.

The correct presentation of the Figure 1 image is shown in this paper.

Surface nitrous oxide (N2O) concentrations and fluxes from different rivers draining contrasting landscapes: Spatio-temporal variability, controls, and implications based on IPCC emission factor

Increasing indirect nitrous oxide (N2O) emission from river networks as a result of enhanced human activities on landscapes has become a global issue, as N2O has been widely recognized as an important ozone-depleting greenhouse gas. However, indirect N2O emissions from different rivers, particularly for those that drain completely different landscapes, are poorly understood. Here, we investigated the spatial-temporal variability of N2O emissions among the different rivers in the Chaohu Lake Basin of Eastern China. Our results showed that river reaches in urban watersheds are the hotspots of N2O production, with a mean N2O concentration of ∼410 nmol L−1, which is 9–18 times greater than those mainly draining forested (23 nmol L−1), agricultural (42 nmol L−1) and mixed (45 nmol L−1) landscapes. Riverine dissolved N2O was generally supersaturated with respect to the atmosphere. Such N2O saturation can best be explained by nitrogen availability, except for those in the forested watersheds, where dissolved oxygen is thought to be the primary predictor. The estimated N2O fluxes in urban rivers reached ∼471 μmol m−2 d−1, a value of ∼22, 13, and 11 times that in forested, agricultural and mixed watersheds, respectively. Averaged riverine N2O emission factors (EF5r) of the forested, agricultural, urban and mixed watersheds were 0.066%, 0.12%, 0.95% and 0.16%, respectively, showing different deviations from the default EF5r that released by IPCC in 2019. This points to a need for more field measurements with wider spatial coverage and finer frequency to further refine the EF5r and to better reveal the mechanisms behind indirect N2O emissions as influenced by watershed landscapes.

Water pollution characteristics and analysis of Chaohu Lake basin by using different assessment methods.

In the context of the water environmental protection and local economic sustainable growth, it is of great importance to conduct a comprehensive water quality assessment in Chaohu Lake basin. In this study, dissolved oxygen (DO), permanganate index (CODMn), 5-day biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP) were investigated monthly at 24 sampling sites in Chaohu Lake basin during 2015 to 2017. Five methods were used to evaluate water quality and identify dominant pollutants. Results showed that the dominant pollutants in Chaohu Lake were TN (4.17~11.61mgL-1) and TP (0.27~0.75mgL-1). The upstream of Chaohu Lake was influenced by Nanfei River, Shiwuli River, and Paihe River, and water quality of the upstream (eutrophic) was worse than that of the downstream (mesotrophic) part of Chaohu Lake. Comprehensive Water Quality Identification Index Method (CWQII) can better assess the water quality compared with the other methods by providing qualitative and quantitative analysis. The index values assessed by CWQII method for Nanfei River, Shiwuli River, and Paihe River were 5.819, 5.986, and 5.141, respectively, and water quality were all assessed as grade V. Overall, water quality of Chaohu Lake has been slightly improved during 2015~2017, but water quality of western inflowing rivers was still heavily polluted. These findings provide valuable information and guidance for water pollution control and water resource management in Chaohu Lake basin. Several feasible measures are proposed.

Monitoring the effects of land consolidation on the ecological environmental quality based on remote sensing: A case study of Chaohu Lake Basin, China

As a kind of activity to break down the original land ecosystem, land consolidation causes the ecosystem to undergo a process of “stability-unstable-stable”. The Chaohu Lake Basin is a typical traditional agricultural planting area and extensive implementation of large-scale land consolidation projects. By monitoring the impact of land consolidation activities in a specific time period in the basin on the project areas and surrounding environment, the spatial and temporal impacts of large-scale land consolidation on regional eco-environmental quality are analyzed. This study mainly monitors crop growth, soil moisture and temperature changes in the land consolidation project area, and the corresponding changes in the surrounding environment. The response of ecological environment factors caused by land consolidation can be embodied in indicators such as humidity, greenness, heat and dryness. Four indicators of NDVI, WET, LST, and NDBSI were selected, using principal component analysis, monitoring the environmental quality changes in the land consolidation areas of Chaohu Lake Basin. Result shows that the ecological environmental quality of the study area exhibits long-term convergence and short-term divergence, and the correlation between the ecological indicators is not significant. The average contribution rate of the first principal component eigenvalue is 67.94 %. The implementation period of the land consolidation project will seriously interfere with the ecological environment, but it can be restored within 3–5 years after implementation, and the ecological environmental quality of the project area will continue to improve. Land consolidation not only can improve the quality of the ecological environment in the consolidation area, but also can promote the surrounding environment. The findings provide theoretical basis and decision guidance for the improvement of land consolidation planning and design (reconstruction) in China, and offer suggestions on strategy-oriented support and scientific basis for promoting the long-term development of land consolidation worldwide.

Holocene environmental evolution recorded by multi-proxies from lacustrine sediments of the Hangbu River Valley, Lake Chaohu Basin, East China

在巢湖杭埠河流域中的古湖盆中心——三河圩区获取28.6 m长的湖相岩芯（SZK1507孔），利用AMS¹⁴C测年技术建立可靠的地层年代序列，通过对SZK1507孔738 cm以上段湖相沉积物平均粒径、磁化率、总氮（TN）、总有机碳（TOC）及C/N的综合分析，高分辨率重建了巢湖杭埠河流域全新世以来的古环境演变过程.结果表明，本区域的环境变化过程可以分为4个阶段，阶段Ⅰ（约10050—9700 cal.a B.P.）与阶段Ⅲ（约9250—5300 cal.a B.P.）气候较为湿润，巢湖水位较高，平均粒径、磁化率值较低，TN、TOC、C/N也偏低；阶段Ⅱ（约9700—9250 cal.a B.P.）与阶段Ⅳ（约5300 cal.a B.P.以来）气候干燥，巢湖水量减少，水位降低，平均粒径、磁化率值、TN、TOC、C/N均较高.一些全球范围内显著发生的气候突变事件在SZK1507孔沉积记录中也有体现，如9.3、8.2和4.2 ka B.P.事件等.将巢湖杭埠河流域10000 cal.a B.P.以来的平均粒径、磁化率、TN、TOC、C/N沉积记录与全新世以来的北纬30°夏季太阳辐射量、太阳黑子数、火山喷发对大气中硫酸盐含量贡献率等进行对比，发现巢湖杭埠河流域全新世气候突变事件主要受控于北半球夏季太阳辐射量变化、太阳活动以及火山活动等因素，并与它们之间复杂的响应机制有关.;Time sequence of the SZK1507 core derived from AMS¹⁴C dating, and the content of the total nitrogen (TN), total organic carbon (TOC) and the C/N values as well as the mean grain size, magnetisability are utilized to reconstruct the environmental changes in the Hangbu River Valley of the Lake Chaohu Basin, East China during the Holocene. The comprehensive analyses of multiple alternative proxies indicated that the evolutionary process of Lake Chaohu Basin in the Holocene could be divided into four periods. The climate was moist in Period Ⅰ ( from 10050 cal. a B.P. to 9700 cal. a B.P.) and Period Ⅲ (from 9250 cal. a B.P. to 5300 cal. a B.P.), and lake level of Lake Chaohu was high inferred from the low values of TN, TOC, C/N, mean grain size and magnetisability. Period Ⅱ (from 9700 cal. a B.P. to 9250 cal. a B.P.) and Period Ⅳ (from 5300 cal. a B.P. to the present) were dry, and the Lake Chaohu had low lake level, suggested by the high values of mean grain size and magnetisability, TN, TOC, C/N. Some global-scale abrupt climatic change events (e.g., 9.3 ka B.P., 8.2 ka B.P., and 4.2 ka B.P. events) were also recorded in this sediment core. Comparing the lacustrine records of SZK1507 core to other observations of climate variability, such as the northern hemisphere summer solar insolation, the sunspot numbers etc during the Holocene, we discovered that the abrupt climatic change events occurring in the Lake Chaohu Basin were affected by the variation of summer solar insolation in the northern hemisphere, the solar activities, the volcanic activities, and the complex feedback mechanism among them principally.

Evaluating transient storage and associated nutrient retention in a nutrient-rich headwater stream: a case study in Lake Chaohu Basin, China.

Transient storage has been studied intensively in small streams, but some processes and mechanisms are not yet entirely understood regarding this issue, especially in chronically nutrient-enriched streams. The exploration of transient storage dynamics in nutrient-rich headwater streams has great significance for stream nutrient management in China and other developing countries, which are suffering from eutrophication. In the present study, we conducted five instantaneous slug additions composed of a conservative tracer dissolved with two nonconservative nutrients injections in a suburban small stream (Guanzhen Creek), Lake Chaohu Basin, China. Transient storage metrics were estimated using the model-fitted hydrologic parameters from the one-dimensional transport with inflow and storage (OTIS) model. Regression analyses were performed to examine the relationship between hydraulic parameters and transient storage metrics. Moreover, nitrogen and phosphorus retention efficiency was qualitatively evaluated based on the OTIS model-fitted nutrient parameters. Our results showed that the OTIS model-fitted hydrologic parameters in Guanzhen Creek were within the range of previously published literature. The transient storage metrics of Guanzhen Creek were generally comparable to those in streams with low-to-moderate nutrient levels in other catchments. Moreover, most of the transient storage metrics showed a strong relationship with stream discharge, while only hydrological retention factor showed a markedly negative correlation with flow rate. Given the negative uptake rates for NH4-N and SRP in half cases, we reasonably concluded that Guanzhen Creek was hardly incapable of retaining nitrogen and phosphorus.

Ecological security assessment of Chaohu Lake Basin of China in the context of River Chief System reform.

In the face of the increasingly severe water environment, establishing an effective water environment management mechanism is a major concern of governments around the world. The River Chief System attempts to match water environment management to the performance of the main leaders of the local party and government and represents an institutional innovation to solve the problem of river and lake management in China. However, there is still a lack of systematic research on the performance of the River Chief System and how to promote its overall effectiveness. This paper took Chaohu Lake Basin, with a concentrated and complicated water environment, as the research object and divided it into eastern and western halves. The water ecological security before and after the implementation of the River Chief System was comprehensively evaluated, and the obstacles to ecological security were diagnosed. The implementation effect of the River Chief System and the weak links of the corresponding river chiefs' work performance were analyzed. The results show the following: (1) Since the implementation of the River Chief System in 2013, the overall water ecological security of Chaohu Lake Basin has been raised from the lower limit to the upper limit of the generally healthy category, initially reflecting the effect of the River Chief System. (2) For the eastern half of the lake, the threat to water ecological security mainly comes from the development of industry. Industrial water use intensity is the primary obstacle to the ecological security of the eastern half of the lake in recent years. (3) For the western half of the lake, the threat to water ecological security mainly comes from the process of urbanization. The wetland area, urban domestic water use intensity, and artificial afforestation area are the main factors hindering the ecological security of the western half of the lake. The above analysis results can be used as the basis for future work to improve the performance of the relevant river chiefs in Chaohu Lake Basin.

Detectable Levels of Bacterial Pathogens in the Rivers of the Lake Chaohu Basin, China.

Bacterial pathogens are one of the causes of human diseases and have a serious impact on environmental health. In this study, we investigated the bacterial pathogen community in 88 sites at rivers around Lake Chaohu Basin, China, using Illumina miseq sequencing. The results showed that three opportunistic pathogens: Acinetobacter, Massilia, and Brevundimonas, were the three abundant bacterial genera in all samples, and had a relative abundance of 0.33 to 49.28% (average 8.80%), 0.06 to 25.4% (average 4.6%), 0.01 to 12.82% (average 2.6%) of all bacterial sequences, respectively. Our results indicated that a high abundance of opportunistic pathogens was observed in the rivers of the Lake Chaohu Basin, and that effective treatment and monitoring of sewage entering into rivers should be further strengthened.

Estimation of Soil Erosion in the Chaohu Lake Basin through Modified Soil Erodibility Combined with Gravel Content in the RUSLE Model

It is generally acknowledged that soil erosion has become one of the greatest global threats to the human–environment system. Although the Revised Universal Soil Loss Equation (RUSLE) has been widely used for soil erosion estimation, the algorithm for calculating soil erodibility factor (K) in this equation remains limited, particularly in the context of China, which features highly diverse soil types. In order to address the problem, a modified algorithm describing the piecewise function of gravel content and relative soil erosion was used for the first time to modify the soil erodibility factor, because it has been proven that gravel content has an important effect on soil erosion. The Chaohu Lake Basin (CLB) in East China was used as an example to assess whether our proposal can improve the accuracy of soil erodibility calculation and soil erosion estimation compared with measured data. Results show that (1) taking gravel content into account helps to improve the calculation of soil erodibility and soil erosion estimation due to its protection to topsoil; (2) the overall soil erosion in the CLB was low (1.78 Mg·ha−1·year−1) the majority of which was slight erosion (accounting for 85.6%) and no extremely severe erosion; and (3) inappropriate land use such as steep slope reclamation and excessive vegetation destruction are the main reasons for soil erosion of the CLB. Our study will contribute to decision-makers to develop soil and water conservation policies.

Potential for Phosphorus Uptake by Bed Sediments and Its Response to Carbon Additions in the Shiwuli River, Chaohu Lake Basin

Surficial sediments were collected from five sampling sites in the mainstream of the Shiwuli River along an urban-rural gradient in the Chaohu Lake basin during July 2017 (summer) and January 2018 (winter). The total uptake (SPUlive), abiotic uptake (SPUkill), and biotic uptake (SPUbiotic) of phosphorus by sediments were measured, and uptake responses to different carbon sources (i. e., sodium acetate, glucose, and a mixture of both) were explored quantitatively through incubation experiments. The results showed that SPUlive had obviously spatiotemporal variations across the five sites, and SPUkill was higher than that of SPUbiotic. Under no carbon added, the mean values of SPUkill were 3.016 μg·(g·h)-1 and 3.368 μg·(g·h)-1, and the average values of SPUbiotic were 0.784 μg·(g·h)-1 and 0.323 μg·(g·h)-1 in summer and winter, respectively. Moreover, significant differences were found in abiotic phosphorus uptake between the two months. In the presence of carbon addition, both the value of SPUbiotic and the contribution rate of biotic phosphorus uptake showed a distinct increase. In general, the magnitude and rate of biotic uptake of phosphorus by sediments was highest when sodium acetate was added, followed by glucose, while the effect of mixed carbon was the worst. The responses of biotic phosphorus uptake to carbon addition suggested that the uptake potential of phosphorus by sediments in Shiwuli River was restricted by the carbon availability to some degree.

Effects of Exogenous Carbon Addition on Equilibrium Phosphate Concentration and Risk of Phosphorus Release from Sediments in the Shiwuli River, Chaohu Lake Basin

Five surface sediment samples were collected every two months from the Shiwuli River along an urban-rural gradient, Chaohu Lake Basin, from July 2017 to May 2018. Sediment phosphorus fractions were investigated, and equilibrium phosphate concentration (EPC0) and its response to exogenous carbon (sodium acetate) addition were explored. Moreover, the risk of phosphorus release from sediment into water column was also evaluated. Results show that the Shiwuli River was seriously polluted by phosphorus. The average values of total phosphorus content in sediments ranged from 915.04 to 1205.31 mg·kg-1, and it decreased slowly along the urban-rural gradient, while the bio-available phosphorus content remained stable. Exogenous carbon addition not only reduced the EPC0 values of sediments (about 29%), but changed the order of EPC0 values among the five sampling sites as well. In general, the ratio of overlying water SRP (soluble reactive phosphorus) concentration to EPC0 value was 66.7%, and phosphorus adsorption-desorption equilibrium saturation EPCsat<-20% accounted for about 60.0%, indicating that the surface sediments in the Shiwuli River were dominated by phosphorus adsorption, namely, keeping the phosphorus "sink" state. The inputs of exogenous carbon addition increased the proportion of EPCsat<-20% from 60.0% to 73.3%, which lowered the risk of phosphorus release from sediments.

The effects of environmental factors and geographic distance on species turnover in an agriculturally dominated river network.

Both environmental and geographic factors interact to structure the metacommunities in river networks, but the importance of these factors is difficult to distinguish. We used six aquatic taxonomic groups to test the relationship between environmental and geographic factors and their effect on species turnover patterns in an agriculturally dominated river (Chaohu Lake Basin, China). The relationships between three dissimilarity indices and geographic distance were assessed using the Mantel test while considering the differences in environmental factors between sites. Then, we employed a variation partitioning method to distinguish the isolated and combined effects of environmental and geographic distance on species turnover. There were significant relationships between environmental distance and species turnover in all groups. All organisms except periphytic diatoms were significantly correlated with two geographic (Euclidean and network) distances when the Chao dissimilarity index was considered. The results suggest that the strength of the correlations changed with environmental and geographic distances and with the aquatic community. The communities displayed more complex relationships with the distance measures when different dissimilarity (Jaccard, Chao, and Bray-Curtis dissimilarity) indices were considered. Nevertheless, aquatic communities are strongly influenced by both environmental and geographic distance, and the former has a stronger effect than the latter.

Effects of channel morphology on nitrate retention in a headwater agricultural stream in Lake Chaohu Basin, China.

Five field tracer experiments and relevant detailed investigations of physical characterizations were conducted to investigate the effects of channel geomorphic settings on nitrate uptake efficiency on a 310-m long geomorphically distinct stream reach in a headwater agricultural stream in Hefei District, Lake Chaohu Basin. The model-fitted parameters from the one-dimensional transport with inflow and storage model were used to estimate the transient storage metric ([Formula: see text]) and determine the total nitrate uptake coefficient (k) for the study reach. And then, a nutrient spiraling approach was applied to reach-scale nitrate uptake estimates (Sw, Vf, and U). The results showed that the main channel was the major contributor to nitrate uptake retention, and the higher geomorphic complexity might result in better nitrate uptake efficiency. The partial least squares regression (PLSR) analysis showed strong correlations between the independent variables as geomorphic settings, Reynolds number and transient storage, and the dependent variables as nitrate uptake metrics, which further underscored the importance of stream physical characteristics on measurement of stream nitrate uptake.

Nitrification Rates and Pollution Characteristics of Sediments with Different Geomorphic Features in the Shiwuli Stream, Chaohu Lake Basin

Sediment and overlying water samples were collected seasonally from five different geomorphic structures (i.e., pools, riffles, gravel bars, point bars, and runs) from two urban reaches of the Shiwulihe River in the Chaohu Lake Basin dominated by high ammonia concentration between July 2017 and March 2018. Both the sediment potential and areal nitrification rates were measured and their seasonal and geomorphological variability were evaluated. The specific differences between every two geomorphic structures were determined using the Mann-Whitney U test and the relationship between the overlying water environment or benthic sediments and sediment nitrification was explored based on regression analysis. The results show that:① The studied reaches are seriously polluted by nitrogen and phosphorus and most of the oxidation-reduction potential (ORP) values in the overlying water were are below 0 mV, suggesting strong reducing conditions of the water column. ② The potential nitrification rates (PNRs) across the five geomorphic structures range from 0.002 to 0.079 μmol·(g·h)-1, with a mean value of 0.023 μmol·(g·h)-1. The ranking order of PNRs is pools > point bars > riffles > gravel bars > runs, with a seasonal change pattern of summer > spring > autumn > winter. ③ The areal nitrification rates (ANRs) across the five geomorphic structures range between 0.140 and 13.543 μmol·(m2·h)-1, with an average of 3.658 μmol·(m2·h)-1. In general, the highest mean value was observed in riffles, followed by runs, and gravel bars and point bars; the smallest value was observed in pools. In addition, ANRs appear to have seasonal change patterns similar to that of the PNRs. ④ According to the difference analysis, there are significant differences between pools or riffles and other features of the PNRs. Extremely significant ANR differences were observed between more than half of the geomorphic structures. ⑤ Regression analysis shows a stronger correlation between sediment nitrification and the overlying water environment, compared with the surface sediment properties.

Mode of Ecological Civilization Construction Based on Water Environment—Case Study of Hefei City and Chaohu Lake Basin

Excellent practices and experiences in industrial development, resource conservation, environmental governance, ecological protection, and watershed management mechanism are introduced from the urban (e.g., Hefei City in Anhui Province) and river basin (e.g., Chaohu Lake Basin) levels. A “three-water improvement” model for ecological civilization construction in urban and rural areas in Hefei, and a “three-ecological optimization” model for ecological civilization construction in Chaohu Basin are summarized through surveys. Meanwhile, development suggestions are proposed to solve problems existing in water ecological environment construction in Anhui Province, including promoting green economic development, strengthening environmental governance and ecological restoration, establishing a dynamic monitoring and early-warning mechanism, improving the watershed management mechanism, and establishing an ecological compensation mechanism and a marketization mechanism.

多种集成方法在巢湖流域面雨量预报中的效果检验

多种集成方法在巢湖流域面雨量预报中的效果检验

Holocene fire in relation to environmental change and human activity reconstructed from sedimentary charcoal of Chaohu Lake, East China

Through analysis of the concentration of different-sized charcoals and magnetic susceptibility of the CH-1 core from Chaohu Lake, East China during the Holocene, the features of fire in relation to environmental change in the charcoal record and the effect of human activities were revealed. Between 9870 and 6040 cal yr BP, the climate was still relatively dry, although it was becoming warmer and wetter. The relatively dry climate apparently created favorable conditions for natural fires to occur, which suggests that the charcoal concentration was high. The warmest and wettest period was from 6040 to 2170 cal yr BP during the Holocene, and very little charcoal was found in the core, because the high precipitation during this period apparently suppressed natural fires. However, human activities increased the fire frequency during the cultural phase. Archaeological investigations indicate that a large number of Neolithic and historic sites, including the Lingjiatan cultural sites (5600–5300 cal yr BP), were distributed around Chaohu Lake. As a result, value peaks in the charcoal concentration were shown. After 2170 cal yr BP, the climate became drier and cooler, and conditions were once again favorable for fires to occur naturally. The concentration of charcoal in the core greatly increased and showed the greatest levels of fire activity, which was related to both the drier climate and the enhanced human activities. The water level of Chaohu Lake reached a minimum in this period, as the lakebed was possibly exposed and formed the substrate for ancient sites, such as the flourishing Juchao state (2090–1710 cal yr BP). During the most recent 200 years, the amount of charcoal concentration sharply decreased, and fire occurrence disappeared gradually because there was not enough biomass in the Chaohu Lake basin.