Changes of Periphyton Abundance and Biomass Driven by Factors Specific to Flooding Inflow in a River Inlet Area in Erhai Lake, China

Periphyton is an ecological essential in freshwater lakes and rivers. Its abundance and biomass are very dynamic in various habitats and subject to various factors, for example, nutrient and light. Following flooding events, the transitional area adjacent to a river inlet and the shallow lake generates diverse habitats for periphyton with gradients in current velocity, suspended matters, nutrients, and light, which would strongly shape the growth and community of periphyton. In this study, three sampling sites were established around a river inlet in Erhai Lake, China, and a field survey was conducted in the sites from April to August (flooding seasons) in 2019 to investigate the abundance and biomass of periphyton and explore influential factors. The results showed that three study areas have different gradients of current velocity depending on the distance to the river inlet, thereby regulating the concentrations of nutrients and suspended matters, which strongly affected the periphyton community; to be specific, the biomass of periphyton was inhibited by the concentration of suspended matters and high concentrations of silicate mainly reduced the diversity of periphyton. Our results imply that the study on the driving factors of periphyton could help to understand its community assembly mechanism and biomass and species composition of periphyton can provide some reference for trophic state of the lake.

Bottom Detection from Backscatter Data of Conventional Side Scan Sonars through 1D-UNet

As widely applicated in many underwater research fields, conventional side-scan sonars require the sonar height to be at the seabed for geocoding seabed images. However, many interference factors, including compensation with unknown gains, suspended matters, etc., would bring difficulties in bottom detection. Existing methods need manual parameter setups or to use postprocessing methods, which limits automatic and real-time processing in complex situations. To solve this problem, a one-dimensional U-Net (1D-UNet) model for sea bottom detection of side-scan data and the bottom detection and tracking method based on 1D-UNet are proposed in this work. First, the basic theory of sonar bottom detection and the interference factors is introduced, which indicates that deep learning of the bottom is a feasible solution. Then, a 1D-UNet model for detecting the sea bottom position from the side-scan backscatter strength sequences is proposed, and the structure and implementation of this model are illustrated in detail. Finally, the bottom detection and tracking algorithms of a single ping and continuous pings are presented on the basis of the proposed model. The measured side-scan sonar data in Meizhou Bay and Bayuquan District were selected in the experiments to verify the model and methods. The 1D-UNet model was first trained and applied with the side-scan data in Meizhou Bay. The training and validation accuracies were 99.92% and 99.77%, respectively, and the sea bottom detection accuracy of the training survey line was 99.88%. The 1D-UNet model showed good robustness to the interference factors of bottom detection and fully real-time performance in comparison with other methods. Moreover, the trained 1D-UNet model is used to process the data in the Bayuquan District for proving model generality. The proposed 1D-UNet model for bottom detection has been proven effective for side-scan sonar data and also has great potentials in wider applications on other types of sonars.

Influence of Particle and Grain Size on Sand Filtration: Effect on Head Loss and Turbidity

Sand filtration is an eco-friendly method to treat either drinking water or wastewater ; it requires only natural granular media. It is also easy to use and to maintain ; the only problem they face is clogging that affects filter performance, that can be detected when head loss or turbidity increase. The purpose of this work is to see what are the factors that influence the performance of filter operation, for this, we used a pilot consisting on a circular column filled with sand (from South Algeria), where various parameters were tested; pressure, flow rate, sand granulometry, suspended matters and particle concentration of the water which is filtered. After eighteen weeks of operation, we have found that head loss increases by decreasing granulometry and increasing flow rate, pressure, particle size, and concentration. However, turbidity increases by decreasing particle size and increasing granulometry and particle concentration. Turbidity and head loss have different behaviour towards the same parameter; that is why it is necessary to take them into account in order to find a compromise between acceptable head loss / turbidity for a good functioning of the filter.

THE ANALYSIS OF APPLICABILITY OF SATELLITE DATA OF SEA COLOR IN AMURSKY BAY IN SUMMERTIME

Амурский залив испытывает значительную антропогенную нагрузку, поэтому важным является организация многоуровнего мониторинга для осуществления оперативного экологического контроля. Цель данной работы заключается в проведении экспериментальных исследований, ориентированных на решение следующих задач: • определение оценок эффективности спутникового зондирования цвета моря в оптически сложных водах морских акваторий, • проведение подспутниковых подводных экспериментов и определение глубины слоев, значимо влияющих на формирование оптического сигнала, регистрируемого из космоса. Для решения поставленных задач проведено два океанографических разреза, на которых выполнены вертикальные измерения биооптических и гидрологических параметров в морской толще. С этой целью были проанализированы спутниковые изображения радиометров MODIS-Aqua, MODIS-Terra, VIIRS-NPP с применением алгоритмов атмосферной коррекции NIR и MUMM, а также биооптического алгоритма OC-3. Показано, что в водах залива в августе цвет моря формируется в основном в верхнем 10-метровом слое, который подвержен речному стоку и содержит большое количество растворенных и взвешенных веществ. Влияние дна и придонных макроводорослей не должно проявляться на глубинах более 15 метров. Для корректного применения спутниковых данных строго обязательно использование алгоритма MUMM и рекомендуется организация автоматизированной сети подспутниковых наблюдений. The Amursky Bay suffers from the severe anthropogenic impact, so it is important to organize multi-level monitoring for continuous real-time ecological control. This work aimed at performing experimental research focused on solving the following tasks: · estimation of the effectiveness of satellite probing of sea color in optically complex waters of marine aquatic areas, · conducting under-satellite underwater experiments and determination of the depth of layers, significantly influencing on forming optical signals recorded from the space. Solving the stated tasks relies on two oceanographic sections, whereon vertical measurements of bio-optical and hydrological parameters of sea column were performed. In this regard, satellite images of radiometers MODIS-Aqua, MODIS-Terra, VIIRS-NPP with the application of NIR, and MUMM algorithms of atmospheric correction were analyzed. Obtained results demonstrate that in August color of the waters of the Bay is mainly formed in the upper 10 meters layer, which is exposed to rivers run-offs and consists of a large amount of dissolved and suspended matters. The influence of the bottom and macro seaweed should not appear on depths more than 15 meters. For adequate usage of satellite data, it is firmly necessary to use the MUMM algorithm and recommended organizing and automated networks of under-satellite surveys.

Theoretical and experimental study of mud injection porous drainage in filters with floating loading

The paper discusses up-flow filters with floating loading that intensify the process of filtering water for drinking purposes by improving filtering parameters and reducing power consumption. It is established that the problematic part of such filters are drainage systems. As a result of the analysis of drainage systems, it was found that the most promising material is porous polymer concrete. The proposed construction of drains is based on porous polymer concrete, which increases the reliability and durability of the filters with floating loading. The drainages based on porous polymer concrete, which intensify reliability and working life of filters, are offered. Mathematical model of the mud injection process of lower polymer concrete drainage with suspended matters, kept in damp water is designed. Experimental studies have shown the validity of the obtained model.

Analysis of the dynamics of changes in the ecological state of surface waters of the Busk district

On the basis of the generalization and systematization of the results of the regime observations made by environmental monitoring services it has been made an ecological assessment of the water quality in the Ukrainian part of the Western Bug River basin (in six section lines of observation). It has been found, the largest source of mechanical contaminations, organic pollutants and nutrients in the Western Bug River is the river Poltva. That is why insufficiently treated waste water of Lviv increases the level of water pollution in this Basin. Main focus is concentrated on the river Western Bug and its stream tributary (the Poltva river), which significantly affects its ecological status. The data concerning pollution indicators for 2015–2018 years was analyzed. A comparison characteristics of the change of pollution of the investigated water objects is carried out in three lookout points: in the river Poltva before falling into the river Western Bug, in the river Western Bug (background area) the above-fall of the Poltva River, in the river Western Bug the below-fall of the Poltva River. Exceeding of the permitted values of most indicators was detected in 2017: suspended matters – 2.4 MPC, ammonium nitrogen – 8.7 MPC, phosphates – 8 MPC, low level of dissolved oxygen is observed, because of high content of organic matters. This situation is better in the basin of the Western Bug River in the sampled area in 2018. The water of the Poltva River is much cleaner in comparison to the previous year, containing up to 2.3 times less suspended substances, 5.1 times less phosphates and 1.3 times organic substances. In this year there is a significant improvement in the ecological state of the Western Bug River, after the falling into the Poltva River. The ecological state of water of these water basins depends on the efficiency of the treatment facilities, especially in Lviv. Municipal wastewater treatment facilities have undergone repair works over recent years in Lviv.