Surface Water Distribution Research Articles

Surface Water Organophosphorus Pesticides Concentration and Distribution in the Langat River, Selangor, Malaysia

Pesticide contamination in the environment is a contemporary global issue. As agricultural production through crop planting in Malaysia now supports both energy and food productions, the concentration and distribution of pesticides in surface water may have changed. Therefore, this study assesses the concentration and distribution of organophosphorus pesticides (quinalphos, diazinon and chlorpyrifos) contamination in the Langat River, Selangor. The Langat River Basin is one of the most populated river basins in Malaysia. As a result, it is surrounded by various environmental stresses of which agricultural activity is a dominant cause. An analytical method has been developed and optimised based on solid-phase extraction and high-performance liquid chromatography, coupled with a diode array detector (SPE–HPLC–DAD). This method allowed for the determination and quantification of selected organophosphorus pesticides. The optimised method displays a high mean recovery for both quinalphos and diazinon (100.21 and 100.15 %, respectively) but relatively low recovery for chlorpyrifos (32.40 %). The low recovery of chlorpyrifos is due to limitations in the determination of multi-residues in a single analytical run, optimisation of chromatographic conditions and the recovery of each compound. The method detection limit was found to be 0.003 μg/L for quinalphos and diazinon, and 0.006 μg/L for chlorpyrifos. Sample analyses revealed the occurrence of quinalphos, diazinon and chlorpyrifos in the Langat River with chlorpyrifos found to have the highest mean concentration of 0.0202 μg/L. The quinalphos and diazinon sample concentrations were 0.0178 μg/L and 0.0094 μg/L, respectively. The concentrations of organophosphorus pesticides in this monitoring study were found to be below the Maximum Contaminant Levels (MCLs) established under the European Union (Drinking Water) Regulation 2014. This study was the first to detect concentrations of quinalphos and diazinon in the Langat River, Selangor.

A seasonal comparison of prokaryote numbers, biomass and heterotrophic productivity in waters of the KwaZulu-Natal Bight, South Africa

The KwaZulu-Natal Bight is a shallow indentation of the eastern seaboard of South Africa, characterised by a narrow (45 km wide) extension of the continental shelf, with a shelf break at about 100 m. It has a complex hydrography: the waters of the bight are derived from the fast-flowing, southward-trending Agulhas Current, which is fed mostly by the tropical and subtropical surface waters of the South-West Indian Ocean subgyre, which are generally oligotrophic in nature, notably depleted in reduced nitrogen and phosphate except at river mouths and during periodic upwelling of deeper nutrient-rich water. Despite this, the bight is believed to be relatively productive, and it is suggested that efficient nutrient recycling by prokaryotes may sustain primary productivity efficiently, even in the absence of new nutrient inputs. Here we have measured bacterial numbers, biomass and heterotrophic productivity during summer and winter in conjunction with phytoplankton standing stock and factors that influence it. Bacterial distribution closely matched phytoplankton distribution in surface waters, and was highest close to the coast. Bacterial standing stocks were similar to those of oligotrophic systems elsewhere (0.5–5.0 × 105 cells ml–1; 1 × 10–8 to 1.25 × 10–7 g C ml–1) and increased in association with the development of phytoplankton blooms offshore and with inputs of allochthonous material by rivers at the coast. Heterotrophic productivity in summer was lowest in the far south and north of the bight (0.5 × 10–10 g C ml–1 h–1) but higher close to the shore, over shallow banks, and in association with increased phytoplankton abundance over the midshelf (1.0–3.5 × 10–9 g C ml–1 h–1). There were marked seasonal differences with lower bacterial standing stocks (5 × 104 to 2 × 105 cells ml–1; 4–5 × 10–9 to 1–2 × 10–8 g C ml–1) and very low bacterial productivity (4 × 10–11 to 1 × 10–10 g C ml–1 h–1) in winter, probably resulting from lowered rates of primary productivity and dissolved organic matter release as well as reduced riverine allochthonous inputs during the winter drought.

The precarious freshwater resources of Sable Island, Nova Scotia, Canada: Occurrence and management considerations

This paper presents an overview of the hydrogeology and the freshwater resources of Sable Island, Nova Scotia. The role of the sand deposits, morphology and dynamics of the dune structures and systems, precipitation, and tidal influences are discussed. The distribution, quality, and importance of both surface water and groundwater resources of the island are also presented. Fresh groundwater on the Island occurs in an unconfined sand lens aquifer. Studies to date on the hydrogeology of the island have shown highly variable rates of precipitation, both seasonally and annually, which in combination with the influence of shifting dune structures contribute to a dynamic freshwater /saltwater balance. Infiltration rates into the permeable aquifer system are greater than precipitation rates, precluding surface water flow.The chemical quality of water in the freshwater lens aquifer is generally good and meets the Guidelines for Canadian Drinking Water Quality. The aquifer is vulnerable to surface contamination, however, due to its shallow, unconfined nature, and any water supply wells are highly likely to be classified as being ‘under the direct influence of surface water’ (GUDI). Under these conditions a multi-barrier source water protection plan is considered essential for managing future public drinking water supplies on the Island. Recommendations for future studies, including long-term monitoring of water level trends, are provided to support the sustainable use of groundwater on the Sable Island.

Continuous measurement of suspended sediment concentration: Discussion of four techniques

Continuous measurements of suspended sediment mass concentration (SSC) and particle size distribution (PSD) in surface waters and hydraulic schemes are of prime importance for the investigation and management of many fine-sediment related processes. In this paper, the performance of selected techniques and instruments for continuous SSC measurements is discussed based on results of a field study and a recent literature-review paper. SSCs measured with Laser In Situ-Scattering and Transmissometry (LISST) or vibrating tube densimetry were confirmed to be not or less biased by temporary PSD variations than SSCs obtained from turbidimeters or a single-frequency acoustic attenuation method. Vibrating tube densimetry allowed measurements of higher SSCs (e.g. 10g/l) compared to the other investigated instruments. For the conversion of the instruments’ outputs to SSC, i.e. calibration, and for validation, gravimetric analysis of bottle samples is recommended as reference.

Groundwater stable isotope profile of the Etosha National Park, Namibia

The Etosha National Park (ENP) is a large protected area in northern Namibia. While the ENP has received a lot of research attention in terms of terrestrial ecosystem process understanding in recent decades, aquatic and hydrological research has to date been limited to a descriptive form. This study provides a baseline hydrological data set of the spatial representation of Oand H-isotope ratios in the groundwater at a park scale, with a focus on three water point types utilised by game, namely natural artesian and contact springs as well as artificial boreholes. The data are used to infer broad-scale hydrological process from groundwater recharge mechanisms dominated by direct rainfall recharge in the west of the ENP to evaporative controls on surface water recharge pathways in the east of the ENP close to Fishers Pan. The findings are used to recommend further targeted research and monitoring to aid management of water resources in the ENP.Conservation implications: The terrestrial ecosystem, particularly large game, are tightly coupled to the distribution of available surface water in the ENP, notably contact and artesian springs. Within the ENP there is a perceived desiccation of these springs. This study provides a baseline upon which more comprehensive studies should be undertaken to differentiate natural from anthropogenic causes for this phenomenon.

Groundwater flow modeling to support water management scenarios – the Bekaa Valley, Lebanon

The Italian Ministry of Foreign Affairs funded a project aimed at developing tools for water management in the Bekaa valley, Lebanon. The Lebanese Ministry of Energy and Water implemented the project, supported by the University of Milan Department of Agricultural and Environmental Sciences (DISAA).The geologic framework consists of a Cretaceous-Eocene carbonatic structure, crossed by a fracture system parallel to the anticlines of the Anti-Lebanon and Mount Hermon ranges and to the synclinal constituting the Bekaa valley. The carbonatic structure is overlain by a Neogene-Quaternary sequence of lacustrine limestones, marls and conglomerates outcropping in the lower valley.In the study area, groundwater bodies fed by precipitation along the mountain ridges, give origin to the Orontes river. Surficial and ground water feed the population, agriculture and fish farming and, since 2011, over one million of Syrian refugees.A Decision Support System (DSS) was set up based on WEAP, a software that represents the interaction between water resources and users by simulating flow mechanisms directly or coupled to external models. MODFLOW-2000, one of such models, was used to represent groundwater flow in the carbonatic and in the overlying Quaternary aquifer, which is present in the lower valley.By coupling WEAP with MODFLOW, it is possible to represent physically-based scenarios of water management, with the aim of optimizing both water extraction and distribution. Moreover, the groundwater flow model could support negotiations between Lebanon, Syria and Turkey for the distribution of surface and ground water through joint data and knowledge.

Heavy metals distribution and contamination in surface water of the Bay of Bengal coast

AbstractIn this study, we measured the distribution of heavy metals (Pb, Ni, Fe, Mn, Cd, Cu) in the surface water of Bengal Coast at the southern part of Bangladesh. We also examined the common water quality parameters to discuss the impacts of pollution. It was revealed that the majority of the heavy metals have been introduced into the Bengal marine from the riverine inflows that are also affected by the impact of industrial, ship breaking yard, gas production plant and urban wastes. The concentration of heavy metals was measured using atomic absorption spectroscopy (AAS) instrument. Heavy metals concentrations were found to decrease in sequence of Fe > Mn > Pb > Cu > Cd > Ni. Results showed that heavy metal concentrations in the marine surface water generally exceed the criteria of international marine water quality. Moreover, both the contamination factor (CF) and pollution load index (PLI) values suggested the elevation of heavy metals concentration in the region. Constant monitoring of the Bengal co...

MEASUREMENTS OF WATER SURFACE SNOW LINES IN CLASSICAL PROTOPLANETARY DISKS

ABSTRACT We present deep Herschel-PACS spectroscopy of far-infrared water lines from a sample of four protoplanetary disks around solar-mass stars, selected to have strong water emission at mid-infrared wavelengths. By combining the new Herschel spectra with archival Spitzer-IRS spectroscopy, we retrieve a parameterized radial surface water vapor distribution from 0.1 to 100 au using two-dimensional dust and line radiative transfer modeling. The surface water distribution is modeled with a step model composed of a constant inner and outer relative water abundance and a critical radius at which the surface water abundance is allowed to change. We find that the four disks have critical radii of ∼3–11 au, at which the surface water abundance decreases by at least 5 orders of magnitude. The measured values for the critical radius are consistently smaller than the location of the surface snow line, as predicted by the observed spectral energy distribution. This suggests that the sharp drop-off of the surface water abundance is not solely due to the local gas-solid balance, but may also be driven by the deactivation of gas-phase chemical pathways to water below 300 K. Assuming a canonical gas-to-dust ratio of 100, as well as coupled gas and dust temperatures T gas = T dust, the best-fit inner water abundances become implausibly high (0.01–1.0 H 2 − 1 ?> ). Conversely, a model in which the gas and dust temperatures are decoupled leads to canonical inner-disk water abundances of ∼ 10 − 4 H 2 − 1 ?> , while retaining gas-to-dust ratios of 100. That is, the evidence for gas–dust decoupling in disk surfaces is stronger than for enhanced gas-to-dust ratios.

Obscure oases: natural, cultural and historical geography of western Queensland's Tertiary sandstone springs

AbstractThe distribution of surface water dictates human and animal activity in arid zones. Although typically small, hidden, and inaccessible, springs and wells fed by local aquifers were the only sources of reliable water across vast areas of inland Australia until the last century. Compared to larger, more accessible water sources such as riverine waterholes and Great Artesian Basin discharge springs, their history is sketchy and poorly documented, although rich in intrigue and mythology. Since the expansion of artificial waters and motorised transport, many of these small oases have been forgotten, and their location and permanence are now less well‐known than for thousands of years. We examine the distribution, hydrogeology, cultural history, and biological values of Tertiary sandstone springs in western Queensland based on a review of historical literature, interviews with long‐term residents, and extensive field surveys. One hundred and sixty springs were documented, and nearly 40% of these have declined in flow or become inactive since pastoral settlement for reasons that are not well understood. While their decline in some areas seems related to shallow bores sunk into their local aquifers, it is possible that some smaller springs owed their existence to regular human maintenance. Others are probably naturally dynamic over decadal time scales. This study documents an almost‐forgotten aspect of Queensland's natural and cultural history.

Spatial analysis and source profiling of beta-agonists and sulfonamides in Langat River basin, Malaysia

Beta-agonists and sulfonamides are widely used for treating both humans and livestock for bronchial and cardiac problems, infectious disease and even as growth promoters. There are concerns about their potential environmental impacts, such as producing drug resistance in bacteria. This study focused on their spatial distribution in surface water and the identification of pollution sources in the Langat River basin, which is one of the most urbanized watersheds in Malaysia. Fourteen beta-agonists and 12 sulfonamides were quantitatively analyzed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). A geographic information system (GIS) was used to visualize catchment areas of the sampling points, and source profiling was conducted to identify the pollution sources based on a correlation between a daily pollutant load of the detected contaminant and an estimated density of human or livestock population in the catchment areas. As a result, 6 compounds (salbutamol, sulfadiazine, sulfapyridine, sulfamethazine, sulfadimethoxine and sulfamethoxazole) were widely detected in mid catchment areas towards estuary. The source profiling indicated that the pollution sources of salbutamol and sulfamethoxazole were from sewage, while sulfadiazine was from effluents of cattle, goat and sheep farms. Thus, this combination method of quantitative and spatial analysis clarified the spatial distribution of these drugs and assisted for identifying the pollution sources.

Performance Evaluation of Existing Community Level Arsenic Removal Plants for Arsenic Free Drinking Water Supply in Jessore and Jhenidah Districts of Bangladesh

The use of groundwater as drinking water in Bangladesh is favoured by its easy availability, microbial safety and absence of proper infrastructure for treatment and distribution of surface water. As a result, millions of people are affected by widespread arsenic poisoning through drinking water drawn from underground sources containing arsenic at concentrations well above the permissible limit of 50µg/L. Since 2000, hundreds of community level arsenic removal plants have been installed in the south-west region of Bangladesh. However, the performance of the plants over time is hindered by lack of information due to the absence of long term water quality monitoring information. The objective of this study is to evaluate the performance of existing community level arsenic removal plants. In this study, we selected five arsenic removal plants (four plants were Arsenic Iron Removal Plant, namely AIRP; and one Granular Ferric Hydroxide Based Arsenic Removal Unit, namely SIDKO) located in Jessore and Jhenidah district. All AIRPs and SIDKO achieved the Bangladesh standard for arsenic in drinking water of 50µg/L. The AIRPs removed 64% of influent arsenic on average. However, the SIDKO removed 80 % of influent arsenic. Treated water quality parameter (such as pH, EC, TDS, PO43-, As, NO3-) of the plants were within the WHO standards, except NH3 (0.01-1.89 mg/L) and Fe++ (1.0 – 1.21 mg/L) for long term uses.

辛安泉岩溶水系统特征的环境同位素研究

为了探究泉域内的岩溶水系统的更新转化特征，选用具有可以快速、准确地了解地下水资源的各种属性的环境同位素示踪方法对辛安泉域内的岩溶水系统的更新转化特征进行了研究。本文以辛安泉域内的岩溶水系统的更新转化为例，通过对辛安泉域岩溶水、孔隙水、地表水中锶同位素所占比重及其空间分布特征的计算与分析，探索了泉域岩溶水系统的转化关系。同时，通过对各个泉域排泄区处的氚含量值的分析，估算出岩溶地下水的平均年龄，进而进一步研究了其更新交替的能力。研究表明：研究域岩溶水具有多样性的补给来源，平均地下水年龄为107a，整个泉域水资源的更新交替也相对频繁。由以上可以证明环境同位素示踪法是探究地下水资源属性行之有效的方法。 In order to explore the transformation characteristics of the karst water system in Spring Basin with the environmental isotope tracing method which has the characteristics of fast and accurate understanding of the groundwater resources, the renewal and transformation characteristics of the karst water system in the Xin’an spring domain were studied. Taking Xin’an Spring in the domain of update transformation as example to analyze the proportion of strontium isotope and characteristics of spatial distribution in karst water, pore water and surface water in the basin, the transform relationship was explored on karst water system. By analyzing the value of tritium isotope in each discharge area of spring basin, the average age of karst groundwater was estimated and then renewability and alternation capability were analyzed. It is shown that karst water system in Xin’an Spring Basin has diversity on recharge sources, and the average age of groundwater is 107a; the renewability and alternation of the whole water resources of the spring area are frequently updating. The analysis method of environmental isotope tracing is proved to be effective in the work of exploring the water resource attributes of groundwater system.

Spatio‐Temporal Patterns of Open Surface Water in the Central Valley of California 2000‐2011: Drought, Land Cover, and Waterbirds

AbstractWe used Landsat satellite imagery to (1) quantify the distribution of open surface water across the Central Valley of California 2000‐2011, (2) summarize spatio‐temporal variation in open surface water during this time series, and (3) assess factors influencing open surface water, including drought and land cover type. We also applied the imagery to identify available habitat for waterbirds in agriculture. Our analyses indicated that between 2000 and 2011 open surface water has declined across the Central Valley during the months of July‐October. On average, drought had a significant negative effect on open surface water in July, September, and October, though the magnitude and timing of the effect varied spatially. The negative impact of a drought year on open water was experienced immediately in the southern Central Valley; however, there was a one year time‐lag effect in the northern Central Valley. The highest proportion of open surface water was on agricultural lands followed by lakes, rivers, and streams, yet the relative proportions varied spatially and across months. Our data were consistent with previous descriptions of waterbird habitat availability in post‐harvest rice in the northern Central Valley. Tracking water distribution using satellites enables empirically based assessments of the impacts of changing water policy, land‐use, drought, climate, and management on water resources.

Effects of ionic strength and cationic type on humic acid facilitated transport of tetracycline in porous media

The occurrence of antibiotics in subsurface environments is increasingly reported recently in addition to the widespread distribution in surface waters. However, the mechanisms governing the transport of antibiotics from surface into subsurface are not well understood. In this study, the transport of tetracycline in saturated sand columns were investigated in the presence and absence of humic acid (HA) at different ionic strengths and cationic types. NaCl (0–0.1M) and CaCl2 (0–0.1M) were used as representatives of mono- and divalent cations in subsurface. The presence of HA moderately facilitated the transport of tetracycline in sand columns. The presence of Na+ inhibited the transport of tetracycline and HA through increasing the deposition of HA aggregates on the sands. The inhibition increased slightly with the increase in Na+ concentration from 0 to 0.1M. In contrast, the presence of Ca2+ dramatically inhibited the transport of tetracycline and HA even at a low concentration of 0.001M, which was attributed to the increased aggregation of HA and the greater electrostatic attractive interactions. Results from this study improve our understanding on the penetration of antibiotics from surface into subsurface waters and the transport of antibiotics in saturated aquifers at environmentally relevant conditions.

Surface water types and sediment distribution patterns at the confluence of mega rivers: The Solimões‐Amazon and Negro Rivers junction

AbstractLarge river channel confluences are recognized as critical fluvial features because both intensive and extensive hydrophysical and geoecological processes take place at this interface. However, identifications of suspended sediment routing patterns through channel junctions and the roles of tributaries on downstream sediment transport in large rivers are still poorly explored. In this paper, we propose a remote sensing‐based approach to characterize the spatiotemporal patterns of the postconfluence suspended sediment transport by mapping the surface water distribution in the ultimate example of large river confluence on Earth where distinct water types meet: The Solimões‐Amazon (white water) and Negro (black water) rivers. The surface water types distribution was modeled for three different years: average hydrological condition (2007) and 2 years when extreme events occurred (drought‐2005 and flood‐2009). Amazonian surface water domination along the main channel is highest during the water discharge rising season. Surface water mixing along the main channel depends on the hydrological seasons with the highest mixed‐homogenized area observed during water discharge peak season and the lowest during discharge rising season. Water mixture also depends on the yearly hydrological regime with the highest rates of water mixing in 2009, followed by 2005 and 2007. We conclude that the dominant mixing patterns observed in this study have been persistent over a decadal scale and the anabranching patterns contribute to avoid a faster mixing in a shorter distance. Our proposed approach can be applied to a variety of morphodynamic and environmental analyses in confluences of large rivers around the world.

Factors affecting differences in the rainy season rice yield in a lowland area of a mountainous village in Lao PDR

The unevenness of rice productivity in lowland areas is caused by differences in farming techniques, accessibility of water, planting environment, and other field-specific factors. In order to increase rice production in low-productivity fields, this study examined the factors affecting yield reduction. In this study, the influence of water conditions, farming activities, and soil fertility on rice yield were analyzed in a lowland area located in the northern part of Lao PDR. A field survey was conducted in a village in Vientiane Province during the rainy season of 2013. Water conditions were observed (i) prior to land preparation, (ii) between land preparation and transplanting, and (iii) after transplanting. Farming activities were recorded in each lowland rice field weekly from June to August. Yield surveys were also conducted in 47 field blocks, and soil samples were collected for soil fertility analyses. The ponding of fields commenced in the middle of June, and extended from the upper part to the lower part of the lowland area. Transplanting was conducted following the distribution of surface water, and no serious water shortages were observed after transplanting in the surveyed areas. There was no correlation between grain yield and the content of total nitrogen or available phosphorus in the field soil. Significant differences in grain yield were detected between direct and plot-to-plot irrigation, early and late ponding, and transplanting in July and in August. The results suggest that water shortages and the delay of field ponding before land preparation led to late transplanting which caused yield reduction.

GDL and MPL Characterization and Their Relevance to Fuel Cell Modelling

PEM fuel cells (PEMFC) are a promising technology for electrochemical energy conversion. However, especially for applications requiring high current density, the gas diffusion layer (GDL) deserves further attention and efforts. Liquid water saturation of pores in the GDL limits the flow of reactants to the catalyst and creates starvation areas with inhomogeneous current density distribution. This leads to accelerated material degradation in these areas and to poor overall performance. Traditional fuel cell models, e.g. CFD simulation modules, make simplifying assumptions, i.e. by modelling the GDL fibre structure as homogeneous porous material, which may cause current density distributions to appear more uniform than they really are. This presentation will give a survey on relevant parameters for GDL characterization, useful methods for investigations and on implications of these results to GDL modelling. The GDL structure inside of an assembled fuel cell can be characterized using X-ray based methods, especially synchrotron or µ-CT based radiography and tomography [1, 2]. Radiographic methods allow for a relatively quick investigation on the integral water distribution within the different MEA layers, especially the GDL substrate and - to some extent - also for the membrane, depending on the selection of material and operating parameters. On the other hand, tomographic methods allow for 3D resolved water distribution analysis, especially for the water distribution within the GDL substrate. Moreover, the different GDL structures due to flow field compression under-land and under-channel are subject of these investigations. Such measurements are performed with sub-μm pixel size at ZSW/HZB to account for the effects of fine pores and fiber structures in detail. The structural information obtained can be used for advanced modelling techniques determining reactant concentrations in the gaseous media employing single-phase approaches. Liquid water effects caused by pore volume reduction may be directly used as model input at this stage. To perform a reasonable modelling of the water distribution itself, not only structural, but also surface parameters must be known. These have to be additionally determined by ex situ techniques. Ideally, the surface properties inside the porous structure would be known down to a sub µm scale. Unfortunately, no generally applicable methods are known until today. First approaches are e.g. the STXM method [3]. But at least integral surface property data can be determined requiring significantly less effort. Different approaches to characterize the wettability of porous media will be discussed. As a very efficient method to determine the inner contact angle of the GDL, inverse gas chromatography techniques may be used. This inner contact angle has been successfully used for a modelling technique (Monte Carlo (MC) modelling) describing the behavior of liquid water inside the porous fibre structure [4]. Thus, using both structural and surface properties, water distribution and GDL transport parameters may be modelled (MC, CFD at µm to mm level) and introduced into models on the macro-scale (e.g. CFD at cell level with segmented GDL areas over rib and over channel). Furthermore, GDL material characteristics regarding transport properties require special attention. As relevant parameters for ex-situ characterization, rating of GDL materials and as important modelling input, structure and material related physical parameters as Leverett function, electrical and heat conductivity, mechanical parameters as E module and shear modulus G can be determined by both modelling on the basis of accurate structure data, e.g. from µ-CT imaging, and – on the macro scale – by direct measurement. Specially, the compression force cycle behavior is mainly obtained from direct measurements. Also, permeability data (in and through plane) may be measured directly. Besides permeation, gas-phase diffusion of the relevant species in the substrate and – on a much smaller scale involving different diffusion mechanisms – in the MPL pores is not trivial to characterize. First results obtained by recently designed setups employing a special low turbulence cell in combination with molar flow analysis for determination of diffusion coefficients and a method to determine the Leverett function will be presented. The ex situ methods recommended will be listed and described in the presentation.

Global Assessment of Bisphenol A in the Environment: Review and Analysis of Its Occurrence and Bioaccumulation.

Because bisphenol A (BPA) is a high production volume chemical, we examined over 500 peer-reviewed studies to understand its global distribution in effluent discharges, surface waters, sewage sludge, biosolids, sediments, soils, air, wildlife, and humans. Bisphenol A was largely reported from urban ecosystems in Asia, Europe, and North America; unfortunately, information was lacking from large geographic areas, megacities, and developing countries. When sufficient data were available, probabilistic hazard assessments were performed to understand global environmental quality concerns. Exceedances of Canadian Predicted No Effect Concentrations for aquatic life were >50% for effluents in Asia, Europe, and North America but as high as 80% for surface water reports from Asia. Similarly, maximum concentrations of BPA in sediments from Asia were higher than Europe. Concentrations of BPA in wildlife, mostly for fish, ranged from 0.2 to 13 000 ng/g. We observed 60% and 40% exceedences of median levels by the US Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey in Europe and Asia, respectively. These findings highlight the utility of coordinating global sensing of environmental contaminants efforts through integration of environmental monitoring and specimen banking to identify regions for implementation of more robust environmental assessment and management programs.

Optimization of a colorimetric method to determine trace urea in seawater

AbstractThis study optimized the experimental conditions for the analysis of dissolved urea in seawater. The kinetics of the colorimetric reaction of urea with diacetyl monoxime were studied under different conditions: reagent stability, pH, and reaction temperature and time, based on which robust procedures were developed for both normal (> 100 nmol L−1, using a five centimeter cuvette) and trace (<100 nmol L−1, using a one meter path length capillary cell) levels of dissolved urea. Our trace level method showed very high sensitivity (detection limit of 1.2 nmol L−1) and high reproducibility (relative standard deviations were 0.29–1.09%), which was a significant improvement as compared to what was reported previously. The current method afforded a more stable colorimetric product, which provided better reproducibility when a large number of samples were analyzed. The normal‐level method was applied to studying the urea distribution in estuarine surface water, and the trace‐level method was applied to studying the vertical distribution of urea in the South China Sea basin (> 4000 m).

Target Detection Method for Water Mapping Using Landsat 8 OLI/TIRS Imagery

Extracting surface water distribution with satellite imagery has been an important subject in remote sensing. Spectral indices of water only use information from a limited number of bands, thus they may have poor performance from pixels contaminated by ice/snow, clouds, etc. The detection algorithms using information from all spectral bands, such as constrained energy minimization (CEM), could avoid this problem to some extent. However, these are mostly designed for hyperspectral imagery, and may fail when applied to multispectral data. It has been proved that adding linearly irrelevant data to original data could improve the performance of CEM. In this study, two kinds of linearly irrelevant data are added for water extraction: the spectral indices and the spectral similarity metric data. CEM is designed for targets with low-probability distribution in an image, but water bodies do not always satisfy this condition. We thereby impose a sensible coefficient for each pixel to form the weighted autocorrelation matrix. In this study, the weight is based on the orthogonal subspace projection, so this new method is named Orthogonal subspace projection Weighted CEM (OWCEM). The newly launched Landsat 8 images over two lakes, the Hala Lake in China with ice/snow distributed in the north, and the Huron Lake in North America, a lake with a very large surface area, are selected to test the accuracy and robustness of our algorithm. The Kappa coefficient and the receiver operating characteristic (ROC) curve are calculated as an accuracy evaluation standard. For both lakes, our method can greatly suppress the background (including ice/snow and clouds) and extract the complete water surface with a high accuracy (Kappa coefficient > 0.96).