Impacts of hydraulic engineering construction on the aquatic environment and ecosystem of Nansi Lake (Shandong Province, China)

Nansi Lake is the largest lake along the eastern route of China's South-to-North Water Diversion Project (SNWDP). It is divided into the upper lake and the lower lake by a dam. By using UV-Vis spectroscopy, synchronous fluorescence (SF) spectroscopy, excitation-emission matrix and parallel factor analysis (EEM-PARAFAC), spatial, and temporal differences in the properties of dissolved organic matter (DOM) were found in the 2 areas of Nansi Lake under different hydrological conditions. A total of 5 fluorescence components were obtained by EEM-PARAFAC, which included 3 humic-like components (C1-C3) and 2 protein-like components (C4 and C5). On the spatial scale, the fluorescence intensities (Fmax) of humic-like substances and the ratio of the fluorescence intensity of humic-like components to the total fluorescence intensity (%Fmax) and degree of humification (HIX) in the upper lake were higher than those in the lower lake. This indicated the strong contributions of terrestrial sources to the upper lake, while DOM properties in the lower lake were more endogenous than those in the upper lake. On the temporal scale, protein-like substances played a more important role in DOM properties in April (Fmax=0.72±0.03 in the upper lake and 1.84±0.13 in the lower lake) and July (Fmax=1.10±0.05 in the upper lake and 1.49±0.04 in the lower lake) than in October. This result might be related to the water transfer of the eastern route of the SNWDP and to the death of submerged plants. However, the contents of humic-like substances (ranging from 55.61±1.23% to 66.56±0.58% for the upper lake and 29.98±1.56% to 61.98±0.99% for the lower lake) and degree of humification (from 2.23±0.06 to 3.10±0.05 for the upper lake and 1.06±0.05 to 2.62±0.08 for the lower lake) in Nansi Lake showed an increasing trend from April to October. In addition, significant correlations and good linear relationships between humic-like components, a254, and DOC in the 3 months reflected the continuous contribution of humic-like substances to DOM properties in Nansi Lake. Rapid changes in the fluorescence signal were largely dependent on changes in water quality. The fluorescence signal could be a tool for the management of water quality in Nansi Lake.

Nansi Lake is an important storage lake in the east route of the South-to-North Water Diversion Project in China, about which there has been serious concern regarding the water quality. In this study, the phytoplankton taxonomic composition, abundance, temporal variations, spatial distribution, and diversity were studied based on a monthly sampling campaign from five sampling stations between January 2010 and December 2010. A total of 159 species (8 phyla, 79 genera), including 74 species of Chlorophyta, 36 species of Bacillariophyta, 19 species of Cyanophyta (including 2 water bloom causative species), 21 species of Euglenophyta, 3 species of Cryptophyta, 5 species of Xanthophyta, 2 species of Pyrrophyta, and 2 species of Chrysophyta, were identified. Average phytoplankton diversity index and evenness values were 4.33 and 0.81, respectively, revealing high biodiversity of phytoplankton community. The phytoplankton abundance averaged at 9.51 × 10(6) cells L(-1) and was much higher than previous investigations carried out in 1983-1984. The dominant species were Bacillariophyta, Chlorophyta in winter and spring, and Chlorophyta and Cyanophyta in summer and atutumn. There were 14 predominant species including Chlorella vulgaris, Cyclotella stelligera, Pseudanabaena limnetica, and Chroomonas acuta. Phytoplankton community structure and environmental variable changed substantially over the survey period. Redundancy Analysis was used to analyze the relationship between them. Temperature was considered to be the key factor driving the change in phytoplankton community composition in Nansi Lake during the 2010 study period.

Under the background of global change, the lake water environment is facing a huge threat from eutrophication. The rapid increase in curly-leaf pondweed (Potamogeton crispus L.) in recent years has seriously threatened the ecological balance and the water diversion safety of the eastern route of China’s South-to-North Water Diversion Project. The monitoring and control of curly-leaf pondweed is imperative in shallow lakes of northern China. Unmanned Aerial Vehicles (UAVs) have great potential for monitoring aquatic vegetation. However, merely using satellite remote sensing to detect submerged vegetation is not sufficient, and the monitoring of UAVs on aquatic vegetation is rarely systematically evaluated. In this study, taking Nansi Lake as a case, we employed Red–Green–Blue (RGB) UAV and satellite datasets to evaluate the monitoring of RGB Vegetation Indices (VIs) in pondweed and mapped the dynamic patterns of the pondweed Fractional Vegetation Coverage (FVC) in Nansi Lake. The pondweed FVC values were extracted using the RGB VIs and the machine learning method. The extraction of the UAV RGB images was evaluated by correlations, accuracy assessments and separability. The correlation between VIs and FVC was used to invert the pondweed FVC in Nansi Lake. The RGB VIs were also calculated using Gaofen-2 (GF-2) and were compared with UAV and Sentinel-2 data. Our results showed the following: (1) The RGB UAV could effectively monitor the FVC of pondweed, especially when using Support Vector Machine that (SVM) has a high ability to recognize pondweed in UAV RGB images. Two RGB VIs, RCC and RGRI, appeared best suited for monitoring aquatic plants. The correlations between four RGB VIs based on GF-2, i.e., GCC, BRI, VDVI, and RGBVI and FVCSVM calculated by the UAV (p < 0.01) were better than those obtained with other RGB VIs. Thus, the RGB VIs of GF-2 were not as effective as those of the UAV in pondweed monitoring. (2) The binomial estimation model constructed by the Normalized Difference Water Index (NDWI) of Sentinel-2 showed a high accuracy (R2 = 0.7505, RMSE = 0.169) for pondweed FVC and can be used for mapping the FVC of pondweed in Nansi Lake. (3) Combined with the Sentinel-2 time-series data, we mapped the dynamic patterns of pondweed FVC in Nansi Lake. It was determined that the flooding of pondweed in Nansi Lake has been alleviated in recent years, but the rapid increase in pondweed in part of Nansi Lake remains a challenging management issue. This study provides practical tools and methodology for the innovative remote sensing monitoring of submerged vegetation.

Based on Landsat images in 1987, 2002 and 2014 from Nansi Lake located in Shandong Province, landscape pattern index, dynamic index, landscape gradient and gridding model were used for analysis of the wetland distribution in the lake. The results showed that the landscape contagion index and aggregation index gradually decreased from 1987 to 2014, while the landscape diversity index and evenness index gradually increased. The distribution of landscape area was more uniform while its patterns trended to be fragmented. Human activities impacted Nansi wetland distribution and the disturbance presented an increasing trend. The total area of Nansi wetland gradually increased during the study period. The area of lake first decreased then increased, and the area reached the maximum in 2014. The area of the ponds along the riparian zone had increased gradually, but the increasing speed slowed down. The area of the rivers remained stable, while the area of the swamps decreased continually during the period. The change of landscape pattern of Nansi Lake wetland mainly resulted from agricultural activities, establishment of Nansi Lake Natural Reserve, and the South-to-North Water Diversion Project.

Variation of cyanobacteria with different environmental conditions in Nansi Lake, China

The Weishan Lake serves as a crucial reservoir and regulating lake in the Eastern Route of the South-to-North Water Diversion Project and the ecological health of its lake ecosystem directly impacts the water quality for water diversion. Diatoms are particularly sensitive to changes in water environments, and the composition of diatom communities serves as a significant indicator of the health of aquatic ecosystems. To understand the composition of diatom communities in Weishan Lake and their relationship with environmental factors, thereby providing scientific grounds for the protection of the lake’s ecological environment, surface sediment diatoms, water samples, and sediments were collected and analyzed. The study revealed that there are 64 species from 19 genera of diatoms in Weishan Lake, predominantly comprising epiphytic and planktonic species. Dominant species include Fragilaria brevistriata, Achnanthes minutissima, and Stephanodiscus parvus, indicating an overall meso-eutrophic status. According to the diatom composition and biodiversity index, the diatom community was divided into three combination zones. Redundancy analysis (RDA) results indicated that the water environmental factors influencing the composition and distribution of diatom communities in Weishan Lake are TP, TOC, DO, NO2 −–N, and Ca2+, collectively explaining 35.60% of the variation in diatom community composition. Due to the influence of agricultural and industrial wastewater runoff, domestic sewage discharge, and cage aquaculture, Weishan Lake is in a mesotrophic eutrophication state. Therefore, it is recommended that strict control over inappropriate human activities in the lake area be implemented in the future to ensure the safety of water quality for water diversion.

Residues of neonicotinoid insecticides in artificial waterways of the Eastern Route of the South-to North water diversion project, China: Implications for environmental risks and human health

Lake Nansi consists of four lakes: the Nanyang,Dushan,Zhaoyang and Weishan Lake.It is a lake in the line of the Eastern Route Project(ERP) of the South-to-North Water Diversion Project(NSBD).After the project supply water in 2013,the water quality of Lake Nansi will be affected significantly.Based on the existing theories and methods,a three-dimensional hydraulic control and water quality model of the lake is presented.The model is developed under the Environmental Fluid Dynamics Code(EFDC) model.It was calibrated and verified to hydrodynamic and water quality data,using two sets of observed data from October 1 to December 31,2006 and January 1 to June 30,2007,respectively.The observed data including water surface elevation,water temperature,chemical oxygen demand,dissolved oxygen and ammonia nitrogen from five stations is used as forcing for simulations.The model results show that temporal and spatial patterns for hydrodynamic and water quality components are consistent with observed data in the reservoir.Because the direction of the water supply and natural flow is converse,the Lake Nansi is divided into the upper-lake and the lower-lake by Erji dam in the Lake Zhaoyang.Two scenarios of whole supplying water term of the lake were simulated using the model.By the analysis of the variations of the hydraulic control and water quality of the upper-lake and lower-lake,This paper proposed three advices of the ERP operation,which can help the project to give full benefits and improve the water quality.

Nansi Lake is the largest and most important freshwater reservoir for the South-North Water Diversion Project located in Shandong Province, China. The characteristics of the nutrient compositions and distribution in the lake sediment may significantly influence the upper-level water quality, which has not been well studied. In this study, the distribution characteristics of the total phosphorus (TP), total organic matter (OM) and total nitrogen (TN) contents in the shallow sediments of Nansi Lake were investigated. The experimental results showed that the sedimentary TP, OM, and TN levels of the entire Nansi Lake (expressed as dry weight percentage) were (0.030 ± 0.003)–(0.129 ± 0.018) %, (1.14 ± 0.18)–(10.60 ± 1.30) % and (0.105 ± 0.021)–(0.71 ± 0.08) %, respectively. The three nutrient indicators appeared to be higher in the upstream lake than in the downstream lake. Concentrations of TN and OM were both particularly higher in aquaculture zones of Nansi Lake, where excessive fish feed may largely contribute to the high TN and OM in the sediment. Furthermore, there was a significantly positive correlation (n = 28, R 2 = 0.7870) between TN and OM. According to the pollution index (P i ) and enrichment factor, there is moderate enrichment of TN and OM in the sediment, while minor enrichment of TP in Nansi Lake. Calculations of the OM index and organic nitrogen index suggested that the surface sediment of the entire Nansi Lake has been contaminated by OM and organic nitrogen. Therefore, there is a pressing need to further investigate the release characteristics of these nutrient contaminants from the sediment of Nansi Lake and potential impacts on the surface water quality.

Characterizing the regional distribution, interaction with microorganisms, and sources of dissolved organic matter for summer rainfall: Insights from spectroscopy, community structure, and back-trajectory analyses

Multi-spectroscopic investigation on the spatial distribution and copper binding ability of sediment dissolved organic matter in Nansi Lake, China

Despite extensive investigation, the tectono‐thermal evolution of the Archean crust in the Lewisian Gneiss Complex in NW Scotland (LGC) is debated. Most U–Pb zircon geochronological and metamorphic studies have focused on rocks from the central region of the mainland LGC, where granulite facies assemblages associated with the oldest (Badcallian) tectono‐metamorphic event at c. 2.75 Ga are overprinted by younger amphibolite facies assemblages related to the Inverian (c. 2.5 Ga) and subsequent Laxfordian (c. 1.9–1.65 Ga) tectono‐thermal events. In the southern and northern regions of the mainland LGC, deformation and metamorphism associated with the Laxfordian event are pervasive, although the timing and conditions are poorly constrained. Here, we present new field, petrographic and structural data, U–Pb zircon and titanite geochronology and phase equilibrium modelling of amphibolite samples from the northern and southern regions. Our field observations show that in both regions, pre‐Laxfordian structures are significantly reworked by steep NW‐striking fabrics that are themselves pervasively overprinted by co‐axial deformation and amphibolite facies metamorphism related to the Laxfordian event. In situ U–Pb titanite geochronology yields Laxfordian ages of 1853 ± 20 Ma in the southern region (P = 6–8 kbar and T = 640–690°C) and 1750 ± 20 Ma and 1776 ± 10 Ma in the northern region (P = 6–7.5 kbar and T = 740–760°C). While U–Pb dating of zircon rims from felsic gneisses in the central region shows a dominant Inverian metamorphic overprint at c. 2500 Ma, zircon rims in felsic gneisses from the northern and southern regions commonly yield Laxfordian dates as young as c. 1800 Ma. Combined, the results support the idea that, during the Palaeoproterozoic, the central region of the LGC acted as low‐strain domain, in which intense deformation and metamorphism were restricted to crustal‐scale shear zones. By contrast, in the southern and northern regions, early (c. 1.85 Ga) and late (c. 1.75 Ga) Laxfordian deformation and fluid‐mediated metamorphism were much more pervasive and at higher P–T conditions than previously proposed. The diachronous Laxfordian evolution of the southern and northern regions indicate that they reflect early and late snapshots of collisional to transpressional tectonics in the mainland LGC. The long‐lasting Laxfordian evolution documents the collision of the Rae and North Atlantic cratons during the Palaeoproterozoic amalgamation of the supercontinent Nuna, with implications for the palaeogeographic configuration of NW Scotland during Palaeoproterozoic Nuna.

Spatiotemporal characteristics and potential pollution factors of water quality in the eastern route of the South-to-North Water Diversion Project in China

Occurrence of typical antibiotics in Nansi Lake's inflowing rivers and antibiotic source contribution to Nansi Lake based on principal component analysis-multiple linear regression model.

Spatiotemporal profiles and underlying mechanisms of the antibiotic resistome in two water-diversion lakes