Taihu Lake Research Articles

Significant diurnal variations in nitrous oxide (N2O) emissions from two contrasting habitats in a large eutrophic lake (Lake Taihu, China)

Algae and macrophytes in lake ecosystems regulate nitrous oxide (N2O) emissions from eutrophic lakes. However, knowledge of diurnal N2O emission patterns from different habitats remains limited. To understand the diurnal patterns and driving mechanisms of N2O emissions from contrasting habitats, continuous in situ observations (72 h) of N2O fluxes from an algae-dominated zone (ADZ) and reed-dominated zone (RDZ) in Lake Taihu were conducted using the Floating Chamber method. The results showed average N2O emission fluxes of 0.15 ± 0.06 and 0.02 ± 0.04 μmol m−2 h−1 in the ADZ and RDZ in autumn, respectively. The significantly higher (p < 0.05) N2O fluxes in the ADZ were mainly attributed to differences in nitrogen (N) levels. The results also showed significant diurnal differences (p < 0.05) in the N2O emission fluxes within the ADZ and RDZ, and daytime fluxes were significantly higher (p < 0.05) than nighttime fluxes. The statistical results indicated that N2O emissions from the ADZ were mainly driven by diurnal variations in N loading and the dissolved oxygen (DO) concentration, and those from the RDZ were more influenced by DO, redox potential, and pH. Finally, we determined the proper time for routine monitoring of N2O flux in the two habitats. Our results highlight the importance of considering diverse habitats and diurnal variations when estimating N2O budgets at a whole-lake scale.

Study of flood protection water levels for railway projects in the plains river network area

The Taihu Lake basin is characterised by a developed water system and a longitudinal river network, which is prone to flooding during the flood season. This poses a threat to the construction and operation of river-related railways, bridges, and other infrastructures, and therefore the design value of the water level of the river channel must be provided prior to the construction of roads and bridges in the basin. The Yanyi Railway traverses numerous river systems without the benefit of measured hydrological data. In order to address this deficiency, two methods were constructed using the Taihu Lake basin model: the historical water level frequency analysis method and the typical design storm method of the basin. These methods were employed to calculate the flood protection water level of each river under different design schemes and to analyze the reasons for the differences in the results. The results indicate that the water level results of the historical water level frequency analysis method are also applicable to the construction of the Yanyi Railway, provided that an economic perspective is taken.

Flexible silicone “honeycomb” sensing module inspired by the natural irregular holes of Taihu Lake Stone, used for athlete posture monitoring and human-computer interaction

Flexible silicone “honeycomb” sensing module inspired by the natural irregular holes of Taihu Lake Stone, used for athlete posture monitoring and human-computer interaction

Effects of Straw and Fertilizer Managements on Nitrogen Loss in Rice Cultivation in Taihu Lake Basin

Nitrogen loss from rice systems is an important source of agricultural non-point source pollution. Many studies revolve around reducing the rate of nitrogen fertilizer application. However, studies examining the characteristics of nitrogen loss in multiple loss paths （runoff, leaching, and lateral seepage） under different straw and fertilizer managements are lacking. Therefore, a study was carried out based on a rice field planted for more than 20 years with straw continuously returned to the field for more than 5 years in Taihu lake basin. The effects of straw and fertilizer managements on nitrogen loss in different paths during the whole growth period of rice were studied. Moreover, straw and fertilizer managements were evaluated by their production suitability and environmental friendliness based on crop yield, nitrogen use efficiency, and nitrogen loss. The results showed that straw removal from the field increased the response sensitivity of nitrogen accumulation in plant tissue to nitrogen application. The nitrogen loss in the rice season was 9-17 kg·hm-2, accounting for 5%-7% of the nitrogen application rate. Straw removal increased the risk of nitrogen loss when soaking water discharged. Straw returning could decrease the nitrogen loss by more than 15%, though the effect of straw on nitrogen loss via lateral seepage was not clear. Furthermore, the suitable substitution of organic fertilizer （30% in this study） could respectively reduce the amount of nitrogen loss via runoff, leaching, and lateral seepage by 16%, 26%, and 37% compared with the fertilizer application under the same nitrogen gradient. In conclusion, the implementation of straw returning and fertilizer type optimization measures effectively reduced the nitrogen loss for unit weight of rice production and realized the balance between agricultural production and environmental protection.

Temporal shifts in the phytoplankton network in a large eutrophic shallow freshwater lake subjected to major environmental changes due to human interventions

Phytoplankton communities are crucial components of aquatic ecosystems, and since they are highly interactive, they always form complex networks. Yet, our understanding of how interactive phytoplankton networks vary through time under changing environmental conditions is limited. Using a 29-year (339 months) long-term dataset on Lake Taihu, China, we constructed a temporal network comprising monthly sub-networks using “extended Local Similarity Analysis” and assessed how eutrophication, climate change, and restoration efforts influenced the temporal dynamics of network complexity and stability. The network architecture of phytoplankton showed strong dynamic changes with varying environments. Our results revealed cascading effects of eutrophication and climate change on phytoplankton network stability via changes in network complexity. The network stability of phytoplankton increased with average degree, modularity, and nestedness and decreased with connectance. Eutrophication (increasing nitrogen) stabilized the phytoplankton network, mainly by increasing its average degree, while climate change, i.e., warming and decreasing wind speed enhanced its stability by increasing the cohesion of phytoplankton communities directly and by decreasing the connectance of network indirectly. A remarkable shift and a major decrease in the temporal dynamics of phytoplankton network complexity (average degree, nestedness) and stability (robustness, persistence) were detected after 2007 when numerous eutrophication mitigation efforts (not all successful) were implemented, leading to simplified phytoplankton networks and reduced stability. Our findings provide new insights into the organization of phytoplankton networks under eutrophication (or re-oligotrophication) and climate change in subtropical shallow lakes.

Integrated biomarker-based ecological risks assessment of tadpole responses to tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, and their combined environmental exposure

Tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCPP) are common chlorinated organophosphorus flame retardants (OPFRs) used in industry. They have been frequently detected together in aquatic environments and associated with various hazardous effects. However, the ecological risks of prolonged exposure to these OPFRs at environmentally relevant concentrations in non-model aquatic organisms remain unexplored. This study investigated the effects of long-term exposure (up to 25 days) to TCEP and TCPP on metamorphosis, hepatic antioxidants, and endocrine function in Polypedates megacephalus tadpoles. Exposure concentrations were set at 3, 30, and 90 μg/L for each substance, conducted independently and in equal-concentration combinations, with a control group included for comparison. The integrated biomarker response (IBR) method developed an optimal linear model for predicting the overall ecological risks of TCEP and TCPP to tadpoles in potential distribution areas of Polypedates species. Results showed that: (1) Exposure to environmentally relevant concentrations of TCEP and TCPP elicited variable adverse effects on tadpole metamorphosis time, hepatic antioxidant enzyme activity and related gene expression, and endocrine-related gene expression, with their combined exposure exacerbating these effects. (2) The IBR value of TCEP was consistently greater than that of TCPP at each concentration, with an additive effect observed under their combined exposure. (3) The ecological risk of tadpoles exposed to the combined presence of TCEP and TCPP was highest in China's Taihu Lake and Vietnam's Hanoi than in other distribution locations. In summary, prolonged exposure to environmentally relevant concentrations of TCEP and TCPP presents potential ecological risks to amphibian tadpoles, offering insights for the development of policies and strategies to control TCEP and TCPP pollution in aquatic ecosystems. Furthermore, the methodology employed in establishing the IBR prediction model provides a methodological framework for assessing the overall ecological risks of multiple OPFRs.

Spatiotemporal dynamics of 2-methylisoborneol produced by filamentous cyanobacteria and associated driving factors in Lake Taihu, China

The proliferation of filamentous cyanobacteria in lakes can result in the generation of odor-causing compounds, predominantly 2-methylisoborneol (2-MIB), which pose odor-related challenges. In an effort to elucidate the spatiotemporal dynamics of 2-MIB and related influencing factors in East Lake Taihu, monthly investigations were undertaken from April 2022 to March 2023. In addition to the monthly survey, a whole-lake survey was conducted during the high-temperature period from July to September. The monthly survey revealed a distinct unimodal fluctuation in the concentration of 2-MIB in East Lake Taihu, with an average concentration at 297.0 ng/L during the high-temperature period. During the high-temperature period, the filamentous cyanobacterial communities detected in East Lake Taihu consisted primarily of species belonging to genera Leptolyngbya, Oscillatoria, Planktothricoides, and Pseudanabaena. However, no significant correlations were found between their densities and 2-MIB concentration. In addition, the mic gene was predominantly detected in genera Pseudanabaena and Planktothricoides, with the latter being the primary contributor to 2-MIB production. Furthermore, a succession of cyanobacteria capable of producing 2-MIB was detected, with water temperature and radiation intensity being identified as the primary driving factors. The temporal variation of 2-MIB concentration within East Lake Taihu during the whole year was primarily modulated by factors such as water temperature, water transparency, dissolved oxygen, and chlorophyll-a. During the high-temperature period, the 2-MIB concentration in the alga-dominated zone of East Lake Taihu was approximately 1.7 times greater than that in the macrophyte-dominated zone, with nutrient and transparency being identified as the main influencing factors. Consequently, our findings are of great significance for monitoring the sources and variation of 2-MIB in shallow lakes, providing a scientific foundation and theoretical guidance for odor management.

Rotary Tillage Plus Mechanical Transplanting Practices Increased Rice Yields with Lower CH4 Emission in a Single Cropping Rice System

As the main contributor to greenhouse gas (GHG) in paddy soil, information on methane (CH4) emission characteristics under different tillage and cultivation practices are limited. A five-year field trial was conducted from 2019 in a single-cropping rice system in Taihu Lake region, east of China. The experiment had a completely randomized block design, and the treatments included rotary tillage plus rice dry direct seeding (RD), rotary tillage plus rice mechanical transplanting (RT), and plowing tillage plus rice mechanical transplanting (PT). We determined the rice yield, GHG emission, soil traits, and methanogens and methanotrophs in 2022 and 2023. The results revealed that PT and RT significantly increased rice yield compared to RD, whereas PT simultaneously increased CH4 emissions. The year-averaged cumulative CH4 emissions in PT were increased by 38.5% and 61.4% higher than RT and RD, respectively. Meanwhile, yield-scaled global warming potentials (GWPs) in RT and RD were lower than those in PT. Tillage and cultivation practices shifted mcrA and pmoA abundances, and PT significantly decreased pmoA abundance. The community structure and diversity of the methanogens and methanotrophs were not significantly affected. Structural equation model analyses illustrated that CH4 emissions were regulated by mcrA and pmoA directly, which in turn, regulated by soil carbon and nitrogen. Overall, rotary tillage plus mechanism transplanting was a feasible agronomic technology in a single-cropping rice system in Taihu Lake region, exhibiting higher and more stable rice productivity, accompanied with lower CH4 emissions and yield-scaled GWP.

Temperature and Dissolved Oxygen Drive Arsenic Mobility at the Sediment-Water Interface in the Lake Taihu.

In this study examining the effects of temperature and dissolved oxygen (DO) on arsenic (As) release at the sediment-water interface (SWI), it was found that an increase in temperature promoted the formation of an anaerobic environment and the reduction and desorption of As fractions within the sediments. A temperature of 32 °C was the most favorable condition for As release at the SWI, and low DO conditions aggravated this process. Even under high DO conditions, the release of sediment As was significantly accelerated under high-temperature conditions, allowing dissolved As to rapidly migrate to the overlying water. In this process, the release of As from sediments was a consequence of the transformation of As fractions in the sediments.

Assessment of China’s EIA Law for the prevention and control of water pollution in interregional Lake Taihu

Assessment of China’s EIA Law for the prevention and control of water pollution in interregional Lake Taihu

Evidence of comammox bacteria playing a dominant role in Lake Taihu sediments based on metagenomic analysis

The nitrification process plays an important role in the nitrogen cycle, in which the ammonia-oxidation process mediated by microorganisms is the rate-limiting step. Environmental factors can affect the distribution and activity of ammonia-oxidizing microorganisms (AOM), including ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and complete ammonia oxidizer (comammox Nitrospira). At present, most studies have used amoA as a marker gene for the ammonia oxidation process to analyze the differences among AOM community composition and abundance in the environment. In this study, metagenomic sequencing was used to study the differences in community composition and functional gene distribution of nitrifying microorganisms in the sediments of Lake Taihu with different eutrophication levels. It was found that comammox Nitrospira and typical nitrite oxidizer NOB Nitrospira, which belong to Nitrospirota, had higher relative abundance at most sites compared to AOB and AOA. Furthermore, the network analysis of genes related to nitrogen cycle showed that the main survival mode of nitrogen metabolizing microorganisms was mutualism. Besides, the microbial genomes in the sediments of Lake Taihu were reconstructed by metagenomic binning, which showed that among the 167 bins obtained, 2 bins (bin 9 and bin 32) were annotated as comammox Nitrospira, and had high abundance in the macrophytes-dominated lakes (such as South Lake Taihu and West Coast). In addition, bin 9, which belongs to comammox Nitrospira, annotates amoA genes associated with ammonia oxidation, and other genes associated with urea decomposition and transport, suggesting functional diversity. Overall, these findings suggest that AOM have different distribution characteristics, among which comammox Nitrospira has high diversity and may be potentially dominant in macrophytes-dominated lakes.

Systematic Analysis of the Effects of Different Green Manure Crop Rotations on Soil Nutrient Dynamics and Bacterial Community Structure in the Taihu Lake Region, Jiangsu

Systematic Analysis of the Effects of Different Green Manure Crop Rotations on Soil Nutrient Dynamics and Bacterial Community Structure in the Taihu Lake Region, Jiangsu

Insight into the binding characteristics of dissolved organic matter(DOM)and Fe(Ⅱ)/Mn(Ⅱ): Based on the spectroscopic and dialysis equilibrium analysis

Dissolved organic matter (DOM) plays an important role in metal migration and transformation within inland surface waters. In our study, spectroscopic and dialysis equilibrium analysis were combined to characterize the binding properties between DOM and Fe(II)/Mn(II). Four different type of DOM including two commercial DOM: humic acid、fulvic acid, and two natural dissolved organic matter collected from macrophyte-dominant region (MDR) and algae-dominated region (ADR) of Taihu Lake. Steady state/time resolved fluorescence spectroscopy indicated that the fluorescence intensity of DOM was quenched by Fe(II)/Mn(II) through a static quenching process. The adsorption isotherm shows that the adsorption capacity of DOM from Taihu Lake for metal ions is significantly higher than that of commercial humic acid. Simultaneously, the combination of MDR and Fe(II) has the highest adsorption capacity at 110.950 mg/g among all combinations. Furthermore, the Pseudo-second-order kinetic model and Elovich model were found to be superior in describing the adsorption process, with chemical adsorption controlling the rate of the adsorption reaction. The results of this study show that potentially toxic elements (PETs) pollution in eutrophic shallow lakes may become more serious due to the excessive expansion of algae dominant regions and the reduction of macrophyte dominant regions. In addition, risk analysis and assessment of PETs should consider the contribution of metal binding capabilities.

Biotic regulation of phoD-encoding gene bacteria on organic phosphorus mineralization in lacustrine sediments with distinct trophic levels

Organic phosphorus (Po) mineralization hydrolyzed by alkaline phosphatase (APase) can replenish bioavailable P load in the sediment water ecosystem of lakes. However, the understanding about the interaction between P load and bacteria community encoding APase generation in the sediment are still limited. Different P pools in the sediments from Taihu Lake, China were measured using sequential extraction procedure. The APAase activity (APA) were obtained accompanying with enzymatic dynamical parameters Vmax and Km. The abundances and diversity of gene phoD-harboring bacterial communities were assessed using high throughput sequencing. The analysis results showed the decrease of potentially bioavailable P fractions including MgCl2-P and Fe-P along sampling gradient southwards together with active P concentrations in the water. Conversely, increasing APA and absolute abundance of phoD gene were found with the decreasing of P loads southwards. Positive correlation (p < 0.05) between absolute abundance and APA indicated that phoD-encoding bacteria manipulated the APA and Po mineralization. Negative correlation (p < 0.01) suggested that the APA was restrained by high P load and was promoted under low P condition. However, higher Vmax and Km values suggested that high mineralization potential of Po maintained the high concentrations of potentially bioavailable P even the APA was restricted. The abundance increase of predominant genus Cobetia (from 15.51 to 24.34 %) mirrored by the reduced Calothrix abundance (from 24.65 to 1036 %) was speculated to be responsible for the APA promotion under low P condition. Higher diversity indices in the high P scenario suggested that high P load stimulated the ecological diversity of gene phoD-encoding bacteria community. Generally, rare taxa such as Burkholderia having high connected degrees in bacterial communities together with abundant genera synergistically manipulated the phoD gene abundance and APase generation. Interaction between P fractions and bacteria encoding phoD gene determined the eutrophication status in the lacustrine ecosystem.

Construction of Multiple Paths for the Living Protection and Utilization of Traditional Villages: A Case Study of the Zhoutie Traditional Village in the Taihu Lake Area

China is a vast country with a wide range of geographical and cultural differences, unbalanced economic development of traditional villages and housings, shortages in infrastructure and people’s living conditions, prominent environmental and ecological problems, and an urgent need to improve the overall level of rural development. For a long time, the protection and utilization of traditional villages have mostly been based on the cognitive views of “frozen protection”and “one-sided protection”, prompting difficulties and resistance in practice. Meanwhile, the result is not effective. At present, traditional villages encounter the situation of declining, hollowing out, and aging. Therefore, it is the theoretical frontier of traditional village research to get rid of the traditional one-sided and frozen protection model. Research should explore the living protection and utilization methods adapted to the characteristics of traditional villages and promote the close integration of traditional village protection and utilization with new development and construction.Under the background of rural revitalization strategy and solving the critical problems of a lack of vitality, the decline and hollowing out of traditional villages are caused by “frozen”protection strategies. This is based on the extensive research and continuous study conducted by the “Key Technology and Integrated Demonstration for the Living Protection and Utilisation of Traditional Villages”of the “13th Five-Year Plan”key research project, especially the in-depth study of traditional villages around Taihu Lake. From the perspective of integrated development, it recogni zes the dynamic interactions among the industrial status (production), regional natural resource (ecology), and historical living conditions (living) . This can help fully coordinate industrial development and improvement of the living environment and ecological construction. Thus, traditional vil lages can obtain endogenous power for sustainable development. It also reveals that living protection and utilization are embodied in a systematic and orderly protection system under the simultaneous development of spatial dimension and temporal dimensions.In the protection system, the coordinated development of spatial and temporal dimensions attaches importance to both the overall protection of the material space of traditional villages and the synergistic development of intangible culture and traditional villages in the time dimension. Its objective is to make the protection and utilization of traditional villages and the peoples ’daily lives mutually promote each other, enhance the villagers ’happiness and sense of achievement, and realize the sustainable development of traditional villages. For the theoretical approach, a multi-level path of living protection and utilization is constructed by combining spatial and temporal dimensions. Among them, the multi-level path in the spatial dimension is composed of three levels: the overall village layout, the individual building, and the indoor environment. The ephemeral path in the temporal dimension is progressively promoted by combining the immediate, medium, and long term, with intertwined interactions of the paths in temporal and spatial dimensions to achieve the living protection of traditional villages. Finally, the practical application of the above-mentioned multiple paths is elaborated by taking the Zhoutie traditional village demonstration project in the Taihu Lake area as an example. Both perspective and practical explorations are conducted.This study is on the construction of multiple paths of traditional villages in temporal and spatial dimensions with an elaboration of the Zhoutie traditional village in the Taihu Lake area. It is an example that will be a positive reference for the research and practical application of the protection and utilization of traditional villages in different regions of China towards an overall and dynamic ‘living ’protection and utilization model. Therefore, this study contributes to building traditional villages to gain continuous endogenous power and promote the sustainable development of traditional villages.

The distribution and fate of pesticides in full-scale drinking water treatment plants

This study utilized HPLC-MS/MS combined with improved solid-phase extraction techniques to investigate the distribution and fate of 31 pesticides in three drinking water treatment plants (DWTPs), which source their water from the Yangtze River, the Yellow River, and Taihu Lake. The total concentration of pesticides in the raw water of the three water treatment plants ranged from 145.4 to 257.1 ng/L, while in the treated water it ranged from 22.8 to 59.0 ng/L, with an average removal efficiency of 78.3 %. Atrazine emerges as the predominant pesticide substance in the raw water of all three plants, indicating its continued widespread use. In the conventional treatment process, sand filtration and disinfection can remove a small amount of pesticides, while coagulation and sedimentation are ineffective. However, adding a pre-ozonation step before coagulation and sedimentation can enhance the removal efficiency of pesticides. Ozone and BAC are the most effective removal processes, with pesticide removal rates ranging from 31.8 % to 64.6 % for ozone and from 20.9 % to 47.7 % for BAC. The combination of ozone and H2O2 (64.6 %) has a higher pesticide removal efficiency compared to the ozone process alone (31.8 % and 50.7 %), especially for substances that are resistant to degradation by ozone. However, BAC's effectiveness in pesticide removal decreases significantly with increasing years of usage. After 2 years of use, the removal rate of BAC is 83.3 %, whereas after 4 years, it decreases to only 26.6 %. This study contributes to the understanding of the fate of pesticides in the drinking water treatment process.

Multidirectional Fate Path Model to Connect Phosphorus Emissions with Freshwater Eutrophication Potential.

Excessive anthropogenic phosphorus (P) emissions put constant pressure on aquatic ecosystems. This pressure can be quantified as the freshwater eutrophication potential (FEP) by linking P emissions, P fate in environmental compartments, and the potentially disappeared fraction of species due to increase of P concentrations in freshwater. However, previous fate modeling on global and regional scales is mainly based on the eight-direction algorithm without distinguishing pollution sources. The algorithm fails to characterize the fate paths of point-source emissions via subsurface pipelines and wastewater treatment infrastructure, and exhibits suboptimal performance in accounting for multidirectional paths caused by river bifurcations, especially in flat terrains. Here we aim to improve the fate modeling by incorporating various fate paths and addressing multidirectional scenarios. We also update the P estimates by complementing potential untreated point-source emissions (PSu). The improved method is examined in a rapidly urbanizing area in Taihu Lake Basin, China in 2017 at a spatial resolution of 100 m × 100 m. Results show that the contribution of PSu on FEP (62.6%) is greater than that on P emissions (58.5%). The FEP is more spatially widely distributed with the improved fate modeling, facilitating targeted regulatory strategies tailored to local conditions.

Shifts of the pond area ratio for lowland polders: Implication for nutrient control

Shifts for natural ecosystems were increasingly concerned due to its profound impacts on ecosystem services. Ponds within lowland artificial watersheds (polders) play a critical role in nitrogen (N) and phosphorus (P) cycling. From the perspective of N & P control in management practices, it is needed to determine an optimal pond area ratio for polders. For this purpose, our study proposed a process-based modelling framework to investigate the response of polder N & P loss to pond area, and thus to determine the threshold value of pond area ratio to achieve maximum N & P reduction for polders. The proposed framework included two process-based models (NDP and PDP) specially developed to describe N & P dynamics in lowland polders. To evaluate the proposed performance of the framework, it was applied to 171 polders in Zhong River Watershed in Lake Taihu Basin, eastern China. Our investigation results revealed that the correlation between polder N & P reduction rate and pond area ratio had an abrupt shift of 13.6 %, 14.7 % for N & P, respectively. Therefore, polders with a pond area ratio of 13.6–14.7 % had the largest N & P reduction (5.27 and 0.19 kg/ha). Polder size affected P reduction rate, with smaller polders (<200 ha) showing a higher P reduction rate, while it did not affect N reduction rate. Compared with annual precipitation, rainy-season precipitation more significantly (P<0.01) determined polder N & P reduction. This study demonstrated the use of our process-based framework in characterizing the shifts for the pond area ratio for polders, and thus provided technical support for N & P control of lowland areas in water management practices.

Aerosol interference with open-path eddy covariance measurement in a lake environment

Open-path eddy covariance (OPEC) is widely used for measuring trace gas fluxes between the surface and the atmosphere. At a lake in Eastern China (Lake Taihu), the CO2 flux measured with OPEC was often negative at night (with values as low as −22.1 μmol m−2 s−1) and was coherent across the whole lake, as if the lake were a large sink of atmospheric CO2. The purpose of this study is to investigate the cause of this negative flux phenomenon. In addition to OPEC, we also used closed-path eddy covariance (CPEC) and the transfer coefficient (TC) method to measure the flux. The results show that the persistent negative CO2 flux phenomenon was observed with OPEC but not with CPEC or TC. Because air drawn into the CPEC analyzer was filtered but the OPEC analyzer was influenced by aerosol contamination, the most logical explanation was that particles deposited on the optical lens of the OPEC analyzer changed its cross-sensitivity to water vapor. The direct evidence of this interference was a strong positive correlation between the OPEC analyzer's signal strength and the CO2 mixing ratio observed at 10 Hz. We suggest that it is possible to perform post-field correction to this negative flux bias using the 10 Hz signal strength data. In comparison, an OPEC system at a nearby land site did not experience aerosol interference due to low water vapor flux at night and lack of hygroscopic growth of particles on the optical lens in low humidity conditions. The type of aerosol interference reported here may also occur in high humidity and high pollution conditions elsewhere.

Evaluation of best management practices for mitigating harmful algal blooms risk in an agricultural lake basin using a watershed model integrated with Bayesian Network approach

Lake eutrophication caused by nitrogen and phosphorus has led to frequent harmful algal blooms (HABs), especially under the unknown challenges of climate change, which have seriously damaged human life and property. In this study, a coupled SWAT-Bayesian Network (SWAT-BN) model framework was constructed to elucidate the mechanisms between non-point source nitrogen pollution in agricultural lake watersheds and algal activities. A typical agricultural shallow lake basin, the Taihu Basin (TB), China, was chosen in this study, aiming to investigate the effectiveness of best management practices (BMPs) in controlling HABs risks in TB. By modeling total nitrogen concentration of Taihu Lake from 2007 to 2022 with four BMPs (filter strips, grassed waterway, fertilizer application reduction and no-till agriculture), the results indicated that fertilizer application reduction proved to be the most effective BMP with 0.130 of Harmful Algal Blooms Probability Reduction (HABs-PR) when reducing 40% of fertilizer, followed by filter strips with 0.01 of HABs-PR when 4815ha of filter strips were conducted, while grassed waterway and no-till agriculture showed no significant effect on preventing HABs. Furthermore, the combined practice between 40% fertilizer application reduction and 4815ha filter strips construction showed synergistic effects with HABs-PR increasing to 0.171. Precipitation and temperature data were distorted to model scenarios of extreme events. As a result, the combined approach outperformed any single BMP in terms of robustness under extreme climates. This research provides a watershed-level perspective on HABs risks mitigation and highlights the strategies to address HABs under the influence of climate change.