Nutrients Seasonal Variation and Budget in Jiaozhou Bay,China: A 3-Dimensional Physical–Biological Coupled Model Study

A 3-D biological model was developed and coupled to a hydrodynamic model, i.e., Princeton Ocean Model, to simulate the seasonal variation and budget of dissolved inorganic nitrogen, phosphate, and silicate in Jiaozhou Bay. The modeled nutrients distribution pattern is consistent with observation. Silicate, the most important limiting element for phytoplankton growth, is characterized by consumption in spring, increase in summer and autumn, and accumulation in winter, whereas dissolved inorganic nitrogen and phosphorous have increasing trend with low rates in spring, due to excessive river loads. Phytoplankton plays an important role in nutrient renewal by photosynthesis and respiration processes. During an annual cycle, 7.83 × 10³ t N, 0.28 × 10³ t P, and 3.93 × 10³ t Si are transported to the bay’s outer sea, i.e., the Yellow Sea, suggesting that Jiaozhou Bay is a significant source of nutrients for the Yellow Sea. The spatial distribution of nutrients is characterized by vertically homogeneous profiles, with high concentration inside the bay and low concentration toward the bay channel. These features are mainly governed by strong turbulent mixing, fluvial influx, water exchange rate, and Yellow Sea water intrusion. Numerical experiments suggest that the government should pay enough attention to proper layout of sewage drainage.     

Source identification and prediction of nitrogen and phosphorus pollution of Lake Taihu by an ensemble machine learning technique

● A machine learning model was used to identify lake nutrient pollution sources. ● XGBoost model showed the best performance for lake water quality prediction. ● Model feature size was reduced by screening the key features with the MIC method. ● TN and TP concentrations of Lake Taihu are mainly affected by endogenous sources. ● Next-month lake TN and TP concentrations were predicted accurately. Effective control of lake eutrophication necessitates a full understanding of the complicated nitrogen and phosphorus pollution sources, for which mathematical modeling is commonly adopted. In contrast to the conventional knowledge-based models that usually perform poorly due to insufficient knowledge of pollutant geochemical cycling, we employed an ensemble machine learning (ML) model to identify the key nitrogen and phosphorus sources of lakes. Six ML models were developed based on 13 years of historical data of Lake Taihu’s water quality, environmental input, and meteorological conditions, among which the XGBoost model stood out as the best model for total nitrogen (TN) and total phosphorus (TP) prediction. The results suggest that the lake TN is mainly affected by the endogenous load and inflow river water quality, while the lake TP is predominantly from endogenous sources. The prediction of the lake TN and TP concentration changes in response to these key feature variations suggests that endogenous source control is a highly desirable option for lake eutrophication control. Finally, one-month-ahead prediction of lake TN and TP concentrations (R² of 0.85 and 0.95, respectively) was achieved based on this model with sliding time window lengths of 9 and 6 months, respectively. Our work demonstrates the great potential of using ensemble ML models for lake pollution source tracking and prediction, which may provide valuable references for early warning and rational control of lake eutrophication.     

光和营养盐对三角褐指藻生化组成的影响

采用¹⁴C标记技术,测定三角褐指藻光合作用速率及其光合产物生化组成的相对含量。实验结果表明,在常温和适宜的光强围范内,随光强增强,三角褐指藻光合产物中蛋白质百分比减少,碳水化合物百分比增加,脂类相对含量基本不变。当海水氮磷比为16时,藻类蛋白质合成的相对含量最高。光合产物生化组成蛋白质与碳水化合物之比（P/C）的变化可以反映在不同海洋环境下藻类的生长状态。     

模拟降解去除人工湿地营养物

人工湿地能有效去除水中的营养物,作为净化水质的方法之一,正得到广泛的应用.同时,尝试建立数学模型模拟去污过程,预测处理效果,并为湿地的运行管理提供理论支持.综合比较了目前常用的4种模型:回归方程模型、一级动力学模型、Monod模型和生态动力学模型,从分析各模型的原理出发,提出了各类模型的优缺点及适用条件,对湿地模型的建立具有指导作用.     

古运河营养元素分布特征及富营养化趋势分析

根据2005～2009年各季度对镇江古运河水体多项指标的监测资料,分析了古运河水体中N、P营养元素的时空分布特征,选用营养状态质量指数法对水体营养状态进行了评价,并预测了古运河水体的富营养化趋势。结果表明,古运河水体中营养元素随年度呈先增后减的特征,而年内季度分布不明显,空间分布基本呈从上游向下游递增的规律;2005～2009年,古运河水体连年处于富营养水平,2007年最为严重,但自2007年以来,水体营养水平逐年下降,水体富营养化趋势有所减缓。     

Changes in Tundra Pond Limnology: Re-sampling Alaskan Ponds After 40 Years

The arctic tundra ponds at the International Biological Program (IBP) site in Barrow, AK, were studied extensively in the 1970s; however, very little aquatic research has been conducted there for over three decades. Due to the rapid climate changes already occurring in northern Alaska, identifying any changes in the ponds’ structure and function over the past 30–40 years can help identify any potential climate-related impacts. Current research on the IBP ponds has revealed significant changes in the physical, chemical, and biological characteristics of these ponds over time. These changes include increased water temperatures, increased water column nutrient concentrations, the presence of at least one new chironomid species, and increased macrophyte cover. However, we have also observed significant annual variation in many measured variables and caution that this variation must be taken into account when attempting to make statements about longer-term change. The Barrow IBP tundra ponds represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure and function. Continued monitoring and protection of these invaluable sites is required to help understand the implications of climate change on freshwater ecosystems in the Arctic.     

Effects of nitrogen deposition and soil fertility on cover and physiology of Cladonia foliacea (Huds.) Willd., a lichen of biological soil crusts from Mediterranean Spain

We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha⁻¹ yr⁻¹ in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. β-carotene/chlorophylls increased with 20-50 kg N ha⁻¹ yr⁻¹ (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha⁻¹ yr⁻¹. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes.     

Nutrient transport through a Vegetative Filter Strip with subsurface drainage

The transport of nutrients and soil sediments in runoff has been recognized as a noteworthy environmental issue. Vegetative Filter Strips (VFS) have been used as one of the best management practices (BMPs) for retaining nutrients and sediments from surface runoff, thus preventing the pollutants from reaching receiving waters. However, the effectiveness of a VFS when combined with a subsurface drainage system has not been investigated previously. This study was undertaken to monitor the retention and transport of nutrients within a VFS that had a subsurface drainage system installed at a depth of 1.2 m below the soil surface. Nutrient concentrations of NO₃-N (Nitrate Nitrogen), PO₄⁻ (Orthophosphorus), and TP (Total Phosphorus) were measured in surface water samples (entering and leaving the VFS), and subsurface outflow. Soil samples were collected and analyzed for plant available Phosphorus (Bray P1) and NO₃-N concentrations. Results showed that PO₄⁻, NO₃-N, and TP concentrations decreased in surface flow through the VFS. Many surface outflow water samples from the VFS showed concentration reductions of as much as 75% for PO₄⁻ and 70% for TP. For subsurface outflow water samples through the drainage system, concentrations of PO₄⁻ and TP decreased but NO₃-N concentrations increased in comparison to concentrations in surface inflow samples. Soil samples that were collected from various depths in the VFS showed a minimal buildup of nutrients in the top soil profile but indicated a gradual buildup of nutrients at the depth of the subsurface drain. Results demonstrate that although a VFS can be very effective in reducing runoff and nutrients from surface flow, the presence of a subsurface drain underneath the VFS may not be environmentally beneficial. Such a combination may increase NO₃-N transport from the VFS, thus invalidating the purpose of the BMP.     

Facilitating access to the algal economy: Mapping waste resources to identify suitable locations for algal farms in Queensland

Algae offer a multiple-benefit opportunity as the products that can result from algal cultivation are numerous and diverse. However, commercial production of algal-derived materials is scarce and in Queensland Australia is virtually non-existent, partly due to challenges around readily available resources. In this work, the potential to regionally recycle waste nitrogen (N), phosphorus (P) and CO₂ to support algal production is considered. A feature of the work is mapping the availability of the three resources for algal cultivation (N, P and CO₂) together with climatic and land use considerations. Mapping resolution is defined by the boundaries of Queensland's (Australia) regional authorities. Layering the maps enables identification of regional hotspots for growing algae. Waste resources are shown to be most abundant in Mackay, Burdekin, Toowoomba, Cassowary and Bundaberg; regions which also have favourable eco-climatic conditions. Waste nitrogen is the limiting waste stream, in these and most other regions however additional requirements can be fixed atmospherically, whereas waste CO₂ is shown to be abundant relative to waste nutrients. It is found that, based on the availability of waste phosphorus, the top 5 most suitable regions have sufficient resources to produce around 1.1 million t/y of algal biomass. This could potentially produce 309 ML of biodiesel which is 5% of Queensland's 2011 diesel oil sales. The outcomes of this work highlight new opportunities for industrial ecology in non-urban regions.     

The trophic status of two northern Irish Sea loughs

Studies were conducted on nutrient cycling in two coastal embayments; Strangford Lough and Belfast Lough, in order to classify these coastal waters in compliance with the European Union Urban Waste Water Treatment and Nitrates Directives. Analysis of the data suggests that Strangford Lough is nitrogen-limited throughout much of the growing season with chlorophyll-a levels comparable to the open Irish Sea. In contrast, much of Belfast Lough is never nitrogen-limited and, with chlorophyll-a levels at times exceeding 50 μg/l, is exhibiting symptoms of eutrophication.