A proposal for architecture and data format. Lucrezia Cilenti1, Rita Dario2, Giuseppe Dentamaro3, Vincenzo Di Lecce3, Cataldo Guaragnella3, Angelo.
Sea water distributed monitoring system A proposal for architecture and data format Lucrezia Cilenti1, Rita Dario2, Giuseppe Dentamaro3, Vincenzo Di Lecce3, Cataldo Guaragnella3, Angelo Cardellicchio3, Giorgio Mancinelli4, Domenico Petruzzelli3, Alessandro Quarto5, Domenico Soldo5, Antonietta Specchiulli1, Ierotheos Zacharias6 1
National Research Council, Institute of Marine Sciences, Unit of Lesina, Via Pola 4, Lesina (FG), Italy 2 Policlinico di Bari, Piazza Giulio Cesare 11, Bari, Italy 3 Dipartimento di Ingegneria Elettrica e dell’Informazione, Politecnico di Bari, Via Orabona 4, Bari, Italy 4 Department of Biological and Environmental Sciences and Tecnhnologies, University of Salento, Italy 5 myHermes Srl, Corso Italia 63, Taranto, Italy 6 Department of Civil Engineering, University of Patras, Patras, Greece Abstract— Marine pollution is known and investigated. In the case of economic exploitation of marine waters, i.e. aquaculture and recreational activities, continuous monitoring of their quality is necessary. Commercial sensors may be used for speditive water monitoring but are usually used as stand-alone systems with limited applications. In this article, after a brief review of commercial sensors as real time detectors of the relevant chemical/biological parameters, experimental data on aquaculture plants are presented. The final objective is to produce through techniques of data fusion from heterogeneous sources with a synthetic representation of the information that may be also used for early warning. Both data format and data architecture are covered Keywords—sensor data fusion, aquaculture, marine pollutants
I. INTRODUCTION Water bodies, e.g., coastal sea, natural lakes as well as reservoirs are critical for human activities such as recreation, fishing and/or aquaculture. Monitoring relevant water quality parameters for the assessment of their ecological state and environmental conditions are paramount important for proper management and planning protocols. Methods and techniques for assessing the status of water bodies are functional to the nature of the body itself, the activities carried out therein and for the available control technologies. Conventional water analysis protocols start from the sampling phase, albeit of simple collection by autosampler, sample storage, pretreatment and data validation based on the currently applied timeconsuming protocols. __________________________________________________ Partially supported by the grant of Lombardia Region Programma Operativo Regionale FESR 2014-2020 / Innovazione e Competitività Iniziativa realizzata nell’ambito dell’Asse I - RAFFORZARE LA RICERCA, LO SVILUPPO E L’INNOVAZIONE. Azione I.1.B.1.3 – Sostegno alle attività collaborative di R&S per lo sviluppo di nuove tecnologie sostenibili, di nuovi prodotti e servizi. Project MAUI (Monitoraggio continuo per le Acque reflue Urbane ed Industriali per l’eco-industria).
Moreover, sensors based on simple transducers and/or complex analytical systems may be used as early warning systems. In this latter context, two specific issues should be addressed in designing sensors-based protocols for early warnings or EWSs [1] of anomalous conditions: a) real-time monitoring and b) on-line monitoring. EWSs are integrated systems based on a set of sensing technologies performing data analysis and acquisition aimed at a specific set of pollutants. Data may be actively discerned, by determining lowprobability and high-impact contamination events and, at the same time, reliable methods to distinguish between normal data fluctuations and variations due to accidental contamination events, after, e.g., biochemical and physical interactions of different quality parameters. Several water facilities for specific uses, e.g. aquaculture, are already adopting on-line EWSs in all production steps including water intake, protection, treatment and distribution operations. In the open seawater many sensors are used as stand-alone systems thus loosing potentialities to model pollution events. In most cases are proprietary devices not allowing for immediate integration and/or fusion of data. Moreover, real-time and on-line monitoring tools allow modifications of the sampling protocols (e.g. the sampling rate), thus leading to more precise identification of time and location of a contamination event. Another important issue is the assessment of the parameters to monitor for the specific application. General indicators of the seawater quality include pH, chlorine, temperature, total organic carbon (TOC), dissolved oxygen, conductivity and turbidity, whereas applications involving the assessment of the sanitary impact include several other parameters [2]. The focus of the present paper is to assess the feasibility of a monitoring system integrating heterogeneous parameters acquired by a set of commercially available sensors, with two main goals: a) to improve the selectivity of the system; b) to set an alert recognition system based on the verification of an algorithm relying on data resulting from field sensors. The system must accomplish the mentioned requirements after: a) real-time and on-line monitoring; b) assessment of the feasibility of the general approach.
To the purpose, an applicative testbed was applied based on the assessment of the water quality in aquaculture plants, one of the main topics of interests in the framework of the European Union Blue Growth Program [3]. Among other goals of the program, the fine-tuning of such systems, together with the assessment of the parameters of interest which are related to the human health. The paper is organized as follows: section II reports an overview of the related works. Section III discuss main aspects of aquaculture monitoring, including the chemical aspects (Section III-a), hydro-geological aspects (Section III-b) and toxicological impact (Section III-c). Section IV shows the proposed approach, Section V the conclusions. II. RELATED WORKS Many commercially available devices are on the market for water monitoring and the most interesting and widespread systems are presented below. Many of these devices are classified as multi-parametric probes, like J-Mar Biosentry, UV-VIS, Censar, s:can Water Quality Monitoring Station and many more. The reference probes are used to assess real-time on-line quality of waters based on determination of the following chemical parameters: turbidity, TOC, pH, BOD, nitrate, nitrite, phosphates and aromatic compounds, whereas biological parameters are essentially based on determination of the water toxicity through bacterial bioluminescence, algae fluorescence and fish activities. Bacterial bioluminescence sensors like TOX are based on the ability of certain bacterial strains, e.g. Vibrio fischeri, to produce light after cellular respiration [4]. Many other indications may be obtained through combination of the above parameters with chlorophyll pigment (Chl a). Another relevant aspect of the aquatic ecosystems is obtained after quantification of the phytoplankton because of its critical role in structuring and functioning of the ecosystems. Indeed, phytoplankton biomass, typically expressed as Chl a, plays an important role in photosynthetic processes and represents a functional ring between food availability and the growth of filter-feeder bivalves and fish larval stages. In situ and real-time measurements of the phytoplankton biomass allows for the early warning of critical phenomena, such as toxic microalgae blooms, which represent a risk for organisms and human health. This latter aspect is important not only for an advanced and cost-effective control of aquaculture activities but also as key step in any monitoring protocol focused on aquatic systems. Conventional dedicated sampling protocols and methods for the assessment of phytoplankton biomass are liable, as a general limitation, to the low ability to detect shorttime variations after the interplay of e.g., climate, diurnal phytoplankton movements, and small-scale water circulation. The suitability of Chl as an indicator of water quality is related to technical factors such as the nutrients present and the ease of monitoring in situ [5]. The development of in-situ sensitive sensors for chlorophyll is based on fluorescence, the ability to absorb light at a specific wavelength and releasing it at lower frequency [6]. Works on many multiparametric probes are equipped with fluorimeters for continuous monitoring of biological variables at improved sensitivity and of robust construction are still in
progress [7]. On the other hand, algae fluorescence is adopted by Algae Toximeter to monitor photosynthetic activity, which is reduced by the presence of toxins in complex matrices. Fish monitoring sensors, like ToxProtect, detect real time swimming activity of about 20 fish species through an array of 80 LED; if an erratic swimming behavior is detected, the presence of water toxins can be assumed. However, this class of sensors requires an accurate knowledge of the relationship between bacterial and algae activity and the amounts toxics detected. Recently new classes of sensors, i.e., e-noses (vapor and gas phases) and e-tongue (liquid phase), have been introduced. E-tongues envisage for direct contact between the sensing element matrix (complex) under analysis [8]. The main drawback of this latter system is direct contact of the sensing elements (e.g. electrodes, diodes, membranes, etc.) with the liquid matrix and thus subject to the potential poisoning. Poisons may bind irreversibly to the sensing elements, thus impairing their performance. To overcome the problem, direct contact must be avoided or minimized by transferring the analyte from the liquid to the vapor phase. This is the working principle of VPeN [9], which employs a gas sensor array to identify components related to, e.g., hydrocarbons, sulfur, nitrogen and phosphorus derivatives present in the complex matrix. Phase transfer from the liquid to the gas/vapour phase may be accomplished by mild heating of the liquid phase. Table I shows a summary of some commercially available sensors. TABLE I.
LIST OF COMMERCIALLY AVAILABLE SENSORS
Name J-Mar Biosentry UV-VIS s:can spectroanalyser ToxProtect TOXControl VPeN Algae ToximeterII Fish Activity Monitoring System SeaBird SBE19 AquaTroll 400
Type Multi-parametric probe Multi-parametric probe Fish activity monitor Bioluminescence monitor e-nose for vapour Toxicity monitor Fish activity monitor Multi-parametric probe Multi-parametric probe
III. PROBLEM OVERVIEW Fish advisories warn consumers for possible toxicological threats associated with consumption of certain families of fish species. In this context, it is demonstrated that fetuses and newborn are susceptible to toxicants while there are no doubts that fishes are a source of valuable nutrients. Coastal ecosystems are under increasing stress from a variety of human activities that induce pollution, flora and fauna changes, together physical alteration of the environmental microbioma [10]. On seawaters, human activities face increasing sanitary risks from growing shoreline urbanization. The authors live and work on the Adriatic and Ionian Sea coast (Bari and Lesina, South-East, Italy and Patras, Greece). The Adriatic Sea is a closed basin with reduced waters interchange with the open Mediterranean. The massive amounts of pollutants released into the Mediterranean basin by rivers and sewage (controlled or not) remain therefore confined in a relatively narrow
geographical area. The Marine Strategy Framework Directive [11] defines (Article 3) the good environmental status of water bodies through a template assessing interventions (Article 5), together with an extensive depiction of the monitoring requirements for an ongoing assessment (Chapters III - V). Therefore, the need for a comprehensive evaluation framework for real-time and on-line monitoring raises directly from the EU Directive. A. Physical, chemical and Biological aspects The integration of physical, chemical and biological data on high frequency time scales represents a paramount important tool in the legislative context of the water quality control, with specific reference to aquaculture economic activities. Relevant real-time information about the chemical status of a water body are obtained by monitoring specific parameters allowing identification of key processes related to the aquatic trophic status. •
Water temperature (T) and variations in water temperature have an important impact on the aquatic life. Biochemical reactions usually experience a doubling in reaction rate after 10°C rise of temperature. Moreover, key constituents of water either change their ionic form (ammonia) or alter their solubility (Dissolved Oxygen) after temperature rising.
•
The salinity (S) is relevant to the aquatic ecosystem, especially if it is characterized by species with low tolerance to salinity. Salinity affects the solubility of oxygen in water. Dissolved Oxygen (DO) concentrations in the water provide an indicator of the overall water quality of the system [12]. DO response is not specific to nutrient input; its depletion can indicate an excessive algal growth (eutrophication), with adverse effects on the organisms’ respiration, feeding and growth [13]. Oxygen measurements combined with temperature, salinity and chlorophyll a, allows for deeper insights into the trophic status of water body.
•
•
•
BOD, a measure of the potential oxygen demand exercised within waters after decaying (oxidation) of the organic matter. Ammonia containing nitrogen, an essential nutrient for algal growth. It is present in all-natural waters in small amounts. However, levels beyond 0.1mg N/L may be indicative of sewage contamination. Total ammonia includes two chemical forms: ammonium ions (NH4+) and non-ionised ammonia gas (NH3). Their relative abundance varies with pH and temperature. High levels of un-ionised ammonia are toxic to invertebrates and fish, causing respiratory stress, conditions such as gill hyperplasia and reduced resistance to parasites and disease. Nitrification, i.e., conversion of ammonia to nitrite/nitrates requires oxygen and may therefore be a significant control on oxygen availability in the water. Nitrate/nitrite contains nitrogen and are hence essential for algal growth in water. High concentrations of
nitrate may lead to excessive algal growth (eutrophication) together with preferential growth of potentially toxic blue-green algae over less problematic algal species. Due to the solubility of nitrate compounds, relevant concentrations may be associated with river waters flowing to the sea after heavy rainfalls from agricultural origin. •
Ortho-phosphate is another important nutrient for algal growth in aquatic environments and likely to be the limiting nutrient in riverine waters. High concentrations of ortho-phosphate ions may induce eutrophication phenomena as, in most, cases; it represents the so–called limiting agent triggering eutrophication.
B. Hydro-geological aspects Several models for heterogeneous basins have been set-up and adopted to evaluate pollutant fluxes in waters [14]. However, instruments assessing parameters needed to characterize dispersion of pollutants in the basins must be assessed and measured while evaluating the environmental status of the water body. Aquaculture may be defined as the high-density production of fish, shellfish and vegetal species produced in a controlled environment. Stocking rates for highdensity aquaculture are typically thousand-fold greater than wild environments. Modern aquaculture employs open and closed systems to breed living species, with the former characterized by a rapid turnover of waters. Different forms of high density, intensive aquaculture is similar as they all obey the same set of physical and chemical principles that are basic of the water chemistry and the net result is water quality. Poor chemical composition of the water leads to rapid degradation. Efficient feed conversion, growth and marketability of the final product may not occur unless the pond is a well-balanced ecosystem. Hence, the overriding concern of the fish farmer is to maintain, balance or equilibrium conditions with respect to water chemistry and its natural consequence is good water quality. High stocking density of fish or crustaceans in ponds usually exacerbates problems with water quality and sediment deterioration. Wastes generated (organic metabolites) from aquaculture activities settle at the bottom of the ponds in the form of biodegradable organic matter. When considering the protection of the marine life, conventional monitoring strategy provides only space and time snapshots of the water quality. Measurements of the water quality may give an overview of the general status of the waters dependent on the intensity of the monitoring. The snapshot strategy does not take hydrographical and weather conditions into account and does not provide forecasts of the water quality. To overcome these problems, hydrodynamic and water quality modelling is needed to provide real time information thus forecasting potential duration and intensity of pollution accidents. In this context, biogeochemical modelling of the water quality includes different combinations of water quality parameters and processes.
C. Sanitary aspects. Main classes of sanitary pollutants affecting human beings may be classified as bioorganic (bacteria, spores, etc.,) and chemical (heavy metals, synthetic molecules with potential endocrine disrupting properties, phosphorous and nitrogen compounds and many others). Fish and shellfish bred in contact with contaminated waters may have serious consequences on human health. Literature data confirm the possibility that harmful agents and microorganisms may accumulate in the sea products thus overcoming the biological barrier of the animals themselves. Many of the works published on this topic report the relevant classes of compounds and the related sanitary effects on man. •
metal-mercury derivatives (MetHg): influencing the nervous system, with children more influenced to the exposure during the critical phases of pre- and postnatal development [15], limits are 4389-16853 for 10ng/L and 10μg/L MeHg exposure,
• trace elements (e.g., As and Cd): arsenobetaine in fish is considered virtually non-toxic. However, the main harmful effects are associated with long-term ingestion of inorganic arsenic thus leading to skin lesions, tumours, developmental toxicity, neurotoxicity, cardiovascular diseases, abnormal glucose metabolism and diabetes (EFSA). Carcinogenic cadmium, may induce kidney, bone and reproductive dysfunctions [16], limit for Cd is 0.27 mg/kg and As 55 to 95 μg/L; •
persistent halogenated compounds and dioxine (PCBs, dioxins, PB-DEs): dioxins and dioxin-like PCBs’,aryl receptor agonists, effects on the reproductive, immune and nervous system developement, immunotoxic, IE [17],limits is PCBs 514,32 pg/g;
• endocrine interferers or disrupters) influencing sex functions and thyroid activity by the presence of steroids like (mimicking) compounds [18]; • polychlorobiphenyls (NDL-PCB): influencing thyroid and liver, brain biochemistry, immunotoxin, estrogenic, reproductive effects and neurobehavioral effects for exposure to the uterus [19]; • polybromodiphenyl ethers (PBDEs) after binding and deactivating the AhR aryl receptor, beyond effects on the expression of CYP1A1, aryl receptor biomarker (AhR, dioxin-like), and CYP2B and CYP3A, androstate androstat bioindicators [20]; • nuclear pregnane X (’xenobiotic nuclear receptor’ CAR and PXR) in the rat, in vivo. Effects on the homeostasis and thyroid homeostasis [21]; • hydroxylated: powerful agonist hydroxylated receptor agonists estrogenic (a and b -ER) [22]; Bacterial strains may be identified, among others, like the well-known Escherichia coli, but also many other pathogens may be detected in food of marine origin. In addition, spores and mycelia of algae and/or plants may contaminate fish products with a wide variety of agents. e.g., the well-known harmful algal blooms (HABs) [23]. An emerging class of
contaminants are microparticles [24]. The particles size may represent a very important factor of direct toxicity and pathology. Absence of knowledge on the transport and fluxes of these particles in natural environments leads to a further problem, which is exasperated by the fact that biological systems did not evolved in the presence of nanoparticles now ubiquitarian in all water bodies. Moreover, nanoparticles from volcanic dust and combustion of natural products (e.g., forest fires), contribute significantly together with synthetic derivatives (e.g., automobile and industrial combustion products) since the industrial revolution. Finally, biodegradability may be a further important factor governing harmful biological effects [26]. IV. PROPOSED SYSTEM A. Sensor characterization Table II shows a set of commercial sensors today available for water quality monitoring and multi-parametric probes. As mentioned, the main aim of this study is definition of a combined monitoring approach that relies on the integration of an e-nose for water quality monitoring systems. The main idea is that both a multi-parametric probe and a e-nose may be synergistically used with their respective sensitivities and operating principles to give a more comprehensive and precise evaluation of the chemical status of the water body. In the following, the data from experiments carried-out on seawater with the VPeN commercial device configured for this specific application are presented. VPeN is an e-nose in vapour phase developed at the AeFLab - Politecnico di Bari and myHermes Srl laboratories. The e-nose integrates several solid-state sensors with other devices, specifically designed to transfer volatile compounds from the liquid phase to the gaseous phase [26]. The ultimate objective is to monitor the related volatile pollutants emitted in a distinct expansion chamber. The device architecture provides a hydraulic system with variable temperature thermostatic chamber and mechanical separator of steam from the liquid. An expansion chamber brings the steam into contact with the gas sensors. Cleaning phases of the chamber and sensors alternate with reading phases [27]. The main problem with VPeN is that it may detect only components that are easily transferred from the liquid to the gas/vapour phase at low temperatures (between 20 and 80°C). It is evident that appropriate chemical reagents can cause selective reactions involving the emission of gases and/or vapours in the presence of specific elements present in water. Only seawater test results without reagents additions will be presented. The aim is to identify a specific signature of seawater suitable for aquaculture that allows the continuous and safe identification of the presence of common pollutants (organic, hydrocarbons, ammonium compounds etc.) typical of marine coastal waters [28]. Experiments with the addition of reagents for the identification of pollutants, both chemically and biological, are currently underway. Real testing samples were taken from a mussel purification plant (Mytilus galloprovincialis) along the northern Adriatic shoreline (Gulf of Venice). Natural seawater
was preliminarily UV-irradiated together or artificial seawater was used according to a cycle defined by Italian legislation. 120 tests were carried out according to the table to follow, the VPeN was equipped with 11 sensitive solid-state sensors (Propan, H2, ethanol alcohol, methyl alcohol, Methane, CO2, NH3, Toluene, SOx). Fig.1 summarizes the complex of all experimental results which were reported by the use of a 3D model. The y axis reports single sensors, the x axis reports the experimental tests, the z axis reports the amplitude of the response from the single sensors. Specifically, single groups of 11 figures from different sensors represents the specific “signature” of the sensor for different pollutants.
The different response of the system to different types of water is clear. The first 4 tests were carried out with a known standard compound to set-up the efficiency of the sensors. The two tests to follow were carried-out with demineralized water for setting the system. 36 tests, sampled at sea in authorized areas, were carried-out at temperatures between 30 and 60 degrees. The same tests were repeated with the water from the mussel purification plant after 5 hours of mussel housing. Finally, 36 tests were carried out with synthetic seawater (demineralised water with the addition of salts) not contaminated by mussels (Fig. 1). It is evident how in the first and third series of tests sensors show comparable response. The seawater contaminated by mussels has a completely different and recognizable signature. Experimental data were subsequently correlated by cluster formation with results shown in Fig. 2. The samples from the first and third tests form a compact and convex cluster with a small exception (see Fig. 1). Mussels contaminated samples form a recognisable compact cluster as compared to clean water. The samples labelled DEM are demineralised water.
Fig. 1. 3D model of measurements realized during tests with VPeN. Y axis represents sensors; X axis tests; Z axis is for representation of each sensor output
B. Data fusion and aggregation The use of multi-sensor systems offers several advantages, in consideration that the measured quantities which are not always independent of each other. A trivial example is the variation of salinity linked to the variation of resistivity. It is therefore possible to say that the multi-value measurement increases the robustness of the measurement and reduces uncertainty due to the high number of low precision measurements. In addition, measurements carried out in different geographic positions are useful to generate diffusion patterns (e.g., pollutants). The increase in the number of
Fig. 2. Clusters of data acquired during tests. Each color is related to a specific class of sample as shown in Fig. 1. The number near each class symbol represent the temperature of the thermostatic chamber
sensors, however, has a cost in terms of data exchange, increases the amount of measurements collected from the environment and makes it more difficult to manage the increased amount of data (many times heterogeneous). This case is well-known as big-data. In the case of seawater, it is therefore of economic and scientific interest the combination of data and the identification of correlations to get real-time response of the systems with the final aim of obtaining reliable data on the status of the water body. The research area is of paramount interest and an unprecedented number of scientific archives and data services are currently published and made accessible. Remote and insitu sensors carry out large amounts of historical observations combined with real-time data, as well as simulations modelled in ever finer spatial and temporal resolutions. With the increasing availability of complex and heterogeneous data, the need for formats adapted to their representation, access, understanding and integration also increases. An example is reported by the eReefs project, aiming to creation of an interoperable coastal information platform for the management of data collected from the Great Barrier Reef in the North-Eastern Australia [29]. In the computer area, another example is represented by the exchange of WaterML 2.0 XML data for time series of hydrological observation data [30]. The NetCDF format, which is a “de facto” standard for output models in many scientific communities, including climatic and atmospheric communities [31]. Both NetCDF and WaterML2.0 are used for data cleaning via standard service interfaces. In addition to rigid formats, models and systems have also been proposed on similar systems the use of semantic disambiguation that, at least partially, makes it possible to extract information that can be structured from unstructured and heterogeneous data [32].
Fig. 3. Architecture of proposed system
V. CONCLUSIONS Marine pollutants are present in a very large number thus affecting environmental, ecological and sanitary aspects of seawater quality. We consider that the economy of nations, regardless of their economic and industrial development, will
depends on the use of marine resources and that fishing is one of the most important. Starting from these considerations and from the preestablished or automatic methods of structuring the information on the quality of marine waters in the relevant field of fish farming, we have obtained the following table highlighting the devices and the parameters currently detectable. In the case of VPeN it can be possible to exploit chemical reactions, even complex ones, to indirectly highlight the presence of elements that are not directly measurable. We are currently carrying out activities prior to the creation of a widespread multi-sensorial system for the speditive and continuous monitoring of the quality of marine waters with a special emphasis on closed or enclosed basins such as the Adriatic Sea and the Ionian Sea. TABLE II.
LIST OF COMMERCIALLY AVAILABLE SENSORS INTEGRABLED IN THE PROPOSED SYSTEM Name Type Analytes VPeN E-nose COD, NH4, NOx, mercaptans, sulphides MultiSeaBird parametric conductivity, depth, temperature, dissolved SBE19 probe oxygen, chlorophyll MultiAquaTroll parametric conductivity, depth, temperature, dissolved 400 probe oxygen, pressure, turbidity, pH
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