Investigation of organochlorine pesticides in the Wang Lake Wetland, China: Implications for environmental processes and risks

Wang Lake Wetland is an important habitat for many fish and migratory birds. To explore the effect of periodic hydrological changes on the transfer and ecological risk of OCPs in the multimedia system of the wetland, eight sampling sites were selected for collecting soil (SS), sediment (SD) and water, to acquire dissolved phase (DP) and suspended particulate matter (SPM) samples during low- and high-flow periods. The results indicated that OCPs are pervasive in the various media of Wang Lake Wetland, and there was a significant temporal variability in concentration of ∑23OCPs in the SPM samples. Several OCPs exist certain ecological risks to aquatic organisms, but higher level of OCPs do not always equal to higher ecological risk. The residues of OCPs are largely attributed to their historical use, but recent inputs of some of them are still non-ignorable. The relatively higher values of organic carbon normalized partition coefficient (KOC) for SPM-W (KOC(SPM-W)) were obtained, which reflected the more frequent exchange of OCPs in the SPM samples. The sediment of the Wang Lake Wetland is likely to be a sink for several OCPs with high n-octanol/water partition coefficient (KOW) (e.g., DDTs and its metabolites), and high-temperature and rainfall-driven changes may promote the migration of OCPs with low KOW to the DP.

Sequestration and export of microplastics in urban river sediments

In rivers, riverbeds are considered to have dual properties as a short-term sink and a source of further mobilization for microplastics. To better understand the sources, storage, and fate of microplastics in river systems, this study quantified the formation of microplastic hotspots in riverbeds and seasonal variations in microplastic inventories in riverbeds, especially for small-sized microplastics (<330 µm), with a fluorescence-based protocol. This study provides first-hand measured evidence for the sequestration of microplastics in the riverbed under low-flow conditions and its export from the riverbed under high-flow conditions. The results show that riverbeds in urban areas are still hotspots for microplastic pollution and that high inputs of urban microplastics control microplastic load in its downstream areas. Seasonal rainfall exported 34.86 % (equivalent to 4.34 × 1011 items/8.57 t) of microplastic pollution from the riverbed, and its removal capacity may be related to the rainfall intensity. Wider riverbeds are conducive to the formation of microplastic hotspots due to the flow slow down. Most importantly, rainfall-driven scouring of the riverbed can enhance the pollution of small-sized microplastics in the riverbed, especially the smallest-size microplastics (<100 µm). Therefore, this study not only contributes reliable information about the sequestration and export of microplastics in the riverbed, but also provides a possible mechanism to explain the lack of small-sized microplastics (<330 µm) in the ocean.

Seasonal trends of per- and polyfluoroalkyl substances in river water affected by fire training sites and wastewater treatment plants

Fire-fighting training areas and wastewater treatment plants (WWTPs) are potential sources of per- and polyfluoroalkyl substances (PFASs) to the nearby aquatic environment. This study investigated seasonal variations of PFAS levels in two river catchments in Sweden; one impacted by Stockholm Arlanda Airport (Sites 1 and 2), and the other by WWTPs and a military airport (Uppsala) (Sites 3 and 4). ƩPFAS concentrations were up to 61 (Sites 1 and 2) and 4 (Sites 3 and 4) times higher compared to the reference site. Distinct different seasonal trends were observed in the two catchments with higher ∑PFAS concentrations during the high water flow season at Site 1 compared to the low water flow season, whereas Sites 3 and 4 showed an inverse seasonal trend. This demonstrates that the pollution is mobilized during periods of high flow in the first catchment (Stockholm Arlanda Airport), while it is diluted during high flow in the second catchment (Uppsala). Average annual loads for ∑PFASs were estimated at ∼5.2 and ∼3.7 kg yr^-1 for the catchment in Uppsala and Stockholm Arlanda Airport, respectively. Thus, both catchments add PFASs to Lake Mälaren, which is Sweden's most important source area for drinking water production.

An improved minimum cumulative resistance model for risk assessment of agricultural non-point source pollution in the coastal zone

Agricultural non-point source pollution (AGNPSP) is an important risk factor affecting the water environment. Among the areas where cropland NPSP occurs, the coastal zone should be of greater concern. Typhoons, heavy precipitation, and abundant rivers and ponds accelerate the transport process of AGNPSP to the offshore waters. It is urgent to construct a simple and accurate model to assess the risk of AGNPSP in the coastal zones. Thus, this study takes the nitrogen pollution from agricultural cultivation in the coastal zone of the Yellow River Delta as an example. A new minimum cumulative resistance (MCR) to agricultural non-point source pollution (AGNPSP-MCR) model is first proposed to simulate the transport process of cropland NPSP into the sea based on the "source-sink" theory in landscape ecology. Finally, the risk is assessed for AGNPSP transport into the sea. The results show the following. (1) The environmental factors of vegetation cover, rainfall erosivity, and soil erodibility are the three most important factors in pollution transportation, weighted 0.3433, 0.2608, and 0.2219, respectively, while the least influential factor is slope, with a weight of only 0.0053. (2) The minimum cumulative resistance of AGNPSP transportation shows a significant positive correlation with the distance to the river and sea, and is higher on the west sides away from the ocean, and smaller in the eastern coastal area near the sea. (3) Similarly, the regions facing serious AGNPSP risk are concentrated in the eastern coastal area, and the cropland area above medium risk was 252.72 km², accounting for 47.57% of the total cultivated land area. (4) Compared with the traditional MCR model, the AGNPSP-MCR model takes into account the quantitative differences of the transport process characteristics of AGNPSP, and it is constrained by the topographical parameter, so the results of AGNPSP risk are more reliable. This study provides a new reference for risk assessments of AGNPSP in the coastal zones.

Nitrogen transport and sources in urban stormwater with different rainfall characteristics

Nitrogen pollution in urban stormwater has led to serious quality issues in urban water. Nitrogen pollution mitigation requires fully understanding the transport process and major nitrogen sources in urban stormwater. In this study, the concentrations and flux of various nitrogen forms during urban stormwater transport were analyzed. It was found that the concentration and flux of NO₃^--N and NH₃-N decreased in the order of roof runoff, road runoff, and drainage runoff, while the concentration and flux of dissolved organic nitrogen (DON) and particulate nitrogen (PN) were found to be the highest in road runoff. Source quantification found that roof runoff (34%) and rainwater (34%) were the main contributors to nitrate pollution during light and moderate rains (<25 mm), while road runoff was identified as the major source (49%) of nitrate pollution during heavy rains (>25 mm) due to the large road runoff volume. Regarding particulate organic nitrogen (PON), the road runoff in commercial areas contributed most (23%) to PON pollution during light and moderate rains, while the runoff generated from pervious surfaces and drainage sediments were the primary two sources (22%) of PON during heavy rains. Moreover, the influence of rainfall characteristics on nitrate and PON source contributions was identified. The results show that antecedent dry periods were an important factor influencing nitrogen source contributions during light and moderate rains, while rainfall amount and intensity were critical factors impacting the nitrogen source contributions during heavy rains. Taking various transport processes, source contributions, and rainfall characteristics into consideration, several recommendations were given for the mitigation of nitrogen pollution in urban stormwater. This study can provide a useful perspective to understand the transport and sources of nitrogen, thus developing constructive strategies to control urban nonpoint source pollution management.

Multimedia distribution of polycyclic aromatic hydrocarbons in the Wang Lake Wetland, China

The Wang Lake Wetland is a highly valued area that is protected due to its high biodiversity. The wetland has a complicated hydrological regime and is subject to frequent human disturbance. We hypothesize that fluctuating hydrology and human activities have varied contributions to the temporal and spatial variations of polycyclic aromatic hydrocarbons (PAHs) in the wetland. Soil (SS), sediment (SD), and water, to acquire dissolved phase (DP) and suspended particulate matter (SPM), samples were collected from eight locations during low- and high-flow periods to elucidate multimedia phase distribution and transport of PAHs. Following the onset of the rainy season, the concentration of SPM-associated PAHs increased significantly, while the DP PAHs remained stable. Individual PAH ratios showed that, although pyrogenic sources are common, petrogenic derived compounds are the main source of PAHs in the Wang Lake Wetland. During the high-flow period, the empirical values for logarithms of the organic carbon-normalized partition coefficients (log K_OC) of individual PAH-congeners were lower than the corresponding field-observed log K_OC values from the SPM-DP and SD-DP systems, reflecting the complexity in evaluating multi-phase PAH partitioning. During the high-flow period, temperature-driven changes may have changed the sediment from a sink to a source for some high molecular weight PAHs. It was determined that human activities governed the PAH loading in the low-flow period, whereas during high-flow conditions, increased rainfall, higher temperatures, and fishery activity are the main factors controlling PAH input to the Wang Lake Wetland.

Transport and sources of nitrogen in stormwater runoff at the urban catchment scale

Revealing the transport and sources of nitrate in urban stormwater runoff can effectively manage nitrate pollution in urban areas. This study used the chemical properties of stormwater along with δ¹⁵N-NO₃^- and δ¹⁸O-NO₃^- isotopes to identify the transport and sources of nitrate within an urban catchment. The results showed that the NO₃-N concentration and total dissolved nitrogen (TDN) composition differed among roof runoff, road runoff, and drainage runoff. The highest NO₃^-N concentration was found in roof runoff and NH₃-N dominated the TDN composition. However, the erosion of pervious surfaces and litter may have led to higher DON/TDN values in road runoff. The TDN composition of drainage runoff was consistent with that of roof runoff. Furthermore, among the various rainfall characteristics, the depth and intensity of rainfall were significantly correlated with the NO₃-N concentrations in roof runoff and road runoff, while antecedent dry days had little effect. According to a Bayesian mixing model, the average contributions of the nitrate load in drainage runoff were ranked as road runoff (51.6%) > rainwater (29.2%) > and roof runoff (15%), which is consistent with the results of previous studies. Rainwater nitrate may have ranked second due to the confluence time, pollution level, and other factors that made rainwater reduce the pollution characteristics of roof runoff. The dominant contribution of road runoff to the NO₃^-N concentration of drainage runoff could be attributed to the large runoff volume. Hence, effective measures should be taken to minimize the NO₃-N concentration in roof runoff, while runoff volume reduction should be the primary concern for controlling road runoff pollution. This work is helpful for obtaining a better understanding of the transport and sources of nitrate that vary dynamically within different hydrological flow pathways, and the outcomes are expected to enhance targeted measures to mitigate nitrate pollution in urban water systems.

Variability of heavy metal transport during the water-sediment regulation period of the Yellow River in 2018

To understand the impacts of the human-induced flood event on heavy metal (HM) transport, spatiotemporal variations in contents and fluxes of metals (Cr, Ni, Cu, Zn, As, Pb, Cd), Pb stable isotopes and characteristics of water and sediment transport into the sea during Water-Sediment Regulation Scheme (WSRS) in Yellow River (YR) were studied based on field investigation at Xiaolangdi Reservoir (XLD), Lijin Station and Yellow River estuary (YRE). The HM transport was significantly controlled by hydrological process and dominated by particulate form with strong associations with particle size and suspended sediment concentration (SSC). In first stage, dissolved heavy metal (DHM) and particulate heavy metal (PHM) contents both increased significantly as coarser sediment with a mixed source of downstream river channel and XLD, while that maintained higher value for stable source of fine-grained XLD sediment in second stage. The HMs into the sea were mainly originated from upper and middle reaches but also contributed by human emissions from downstream area. As the source of HMs into the sea, the downstream area also acted as an important sink, especially in first stage, playing a role of buffering and filtration. During WSRS, the YR discharged 49%-60% of annual HM flux into the sea, and the second stage is the main transport period, leading to a great alternation in geochemical composition of the YRE sediment.

Transport process and source contribution of nitrogen in stormwater runoff from urban catchments

Nitrogen in urban stormwater has been widely studied, and effective management of nitrogen pollution is critical for improving urban stormwater and receiving water quality. This requires an in-depth understanding of the transport process and source contribution to both dissolved and particulate nitrogen in stormwater from urban catchments. In this study, 123 stormwater runoff samples were collected from an urban catchment during different rainfall events. Dissolved and particulate nitrogen concentrations in roof runoff, road runoff, and sewer flow were analyzed. The concentration of dissolved nitrogen was higher in roof runoff than in road runoff and sewer flow. However, the concentration of particulate nitrogen was lower in roof runoff than in road runoff and sewer flow. Isotopic analysis and Bayesian mixing models showed that road runoff was the largest source contributor of both nitrate and particulate organic nitrogen (PON) in sewer flow discharged from the study catchment. In addition, road runoff contributed the majority of PON associated with coarse particles (>105 μm), whereas PON associated with fine particles (<105 μm) was primarily washed-off of sewer sediments. The results provided several suggestions for the management of nitrogen pollution in urban catchments. This study could help to fully understand the transport and sources of nitrogen pollution in urban stormwater and provide recommendations to the government for implementing appropriate stormwater management strategies to minimize stormwater pollution.

Distribution and assessment of heavy metal contents in surface sediments of the western Sunda Shelf

The heavy metal contents (Cr, Cu, Zn, Cd, Pb, Hg, and As) of 88 surface sediment samples from the western Sunda Shelf were analyzed to determine their spatial distribution patterns and contamination status. The results demonstrated that high enrichment regions of heavy metals were focused in the Kelantan, Pahang, and Ambat river estuaries, and deep water regions of the study area. These high enrichment regions were mainly controlled by riverine inputs and their hydrodynamic conditions. The enrichment factor (EF), geoaccumulation index (I_geo), and potential ecological risk index (PERI) were used to assess heavy metal accumulation. The results indicated that the study area was not significantly contaminated overall at the time of the study; however, Cd, As, and Hg were at levels corresponding to moderate contamination at many stations located in the Pahang River estuary, Kelantan River estuary, and north-eastern region of the study area, primarily because of anthropogenic activities.

CFD study and experimental validation of low liquid-loading flow assurance in oil and gas transport: studying the effect of fluid properties and operating conditions on flow variables

Low liquid-loading flow frequently occurs during the transport of gas products in various industries, such as in the Oil & Gas, the Food, and the Pharmaceutical Industries. Even small amounts of liquid can have a significant effect on the flow conditions inside the pipeline, such as increased pressure loss, pipe wall stresses and corrosion, and liquid holdup along the pipeline. However, most studies that analyze this type of flow only use atmospheric pressures and horizontal 1-in or 2-in pipes, which do not accurately represent the range of operating conditions present in industrial applications. Therefore, this study focused on modeling low liquid-loading flow in medium-sized (6–10 in) pipes, using CFD simulations and experimental data from the University of Tulsa, and then applying it to real operating conditions from a Colombian gas pipeline. An acceptable difference was observed between experimental and CFD data, both for the liquid holdup (18%) and for the pressure drop (12%). Variables like pressure drop and wall shear stress increase with phase velocity, operating pressure, and pipe inclination. Liquid holdup increases with liquid velocity but decreases with all other factors. The relation of flow variables with phase velocities is of particular interest: Doubling the gas velocity decreased holdup 70% and increased pressure drop tenfold. On the other hand, the presence of the liquid phase seems to be more influential on process variables than its exact flowrate; the introduction of the liquid phase to a single-phase gas causes an increase in pressure loss by a factor of three, but doubling the liquid velocity only increases the pressure loss by a further 30%.

Supply chain and environmental assessment of the essential oil production using Calendula (Calendula Officinalis) as raw material

Biomass has been considered a potential source of value-added products and energy vectors. Most biomass studies have researched the best pathways or processes to upgrade this renewable raw material through stand-alone processes or biorefineries. The biomass supply chain is a crucial aspect in the economic analysis of biomass upgrading since most of the raw materials need to be transported. A supply chain analysis gives an idea about the availability, real costs, and storage conditions of the raw material to guarantee an accurate feasibility analysis and a standardized production process. Calendula (Calendula Officinalis) is an aromatic plant used to produce valuable extracts in the cosmetic and pharmaceutical industries. Nevertheless, high amounts of exhausted biomass (more than 95% w/w) are produced and wasted. Theseresidues represent an environmental issue to be solved through the implementation of valorizing options. This paper analyses the supply chain and environmental impact of essential oil production using Calendula (Calendula Officinalis) as a raw material in the Colombian context. The case study comprises a single-objective optimization of the calendula supply chain to produce essential oil and the life cycle assessment (LCA) of the process through a cradle-to-gate approach in the Colombian context. The results showed the best locations to upgrade Calendula in Colombia (i.e., Manizales and Bucaramanga), supplying 1.1 % of the total product demand. The optimal product flow to customers was 0.32 tons/year, and the required feedstock from suppliers was 162 tons/year. The agricultural stage of essential oil production represented the highest environmental impact of the supply chain. In particular, plastic sheets, organic fertilizers, and chemical fungicides were the main contributors to this impact.

Characterization of the effectiveness of a hydrocarbon liquid solidifier

Solidifiers are dry, granular hydrophobic polymers that form physical bonds with hydrocarbons by molecular interactions (hydrogen bonding, London forces), and are used to immobilize hydrocarbon spill propagation and dispersion. CIAgent© is a non-toxic, proprietary polymer blend listed as an “Oil Solidifier” on the EPA's National Contingency Plan Product Schedule for use on hydrocarbon spills in the navigable waterways of United States. CIAgent solidifies the liquid hydrocarbons through a rapid transformation into a cohesive rubber-like inert mass upon contact and retains the liquid for easier removal and disposal. The objective of this paper is to determine the effectiveness of the solidifier with a variety of hydrocarbon liquids that could be encountered in an oil spill scenario. The effectiveness of the solidifier was characterized in terms of the application rate, temperature change, solubility parameters and solidification time for a variety of hydrocarbon liquids (e. g., gasoline, diesel fuel, crude oil) that could be encountered by measuring the heat of solidification using a solution calorimeter. A thermogram was obtained and the heat of solidification was calculated using the temperature difference upon solidification. The temperature change and the degree of swelling in the solidifier were used to determine the solubility parameter of the solidifier (6.77 Hildebrands). The heat of solidification value was used to determine the ease and speed of the solidification of the hydrocarbon liquids. Solidification times ranged from 40 to 120 s for the liquids tested. The average application ratio in weight of solidifier to weight of hydrocarbon ranged was 3.35.

RESILIENT: A robust statistical method for estimating multiple VOC sources from limited field measurements

Air pollution due to haphazard industrialization has become a major concern in developing countries. Yet, enforcement of related norms remains problematic because violators cannot easily be pinpointed among closely situated industrial units. Accordingly, it has become imperative to equip regulatory authorities with an economical yet accurate tool that quickly locates emission sources and estimates emission rates. Against this backdrop, we propose RESILIENT, a method for Robust Estimation of Source Information from LImited field measuremENTs, which exhibits significant statistical robustness and accuracy even when the data are collected using a low-cost error-prone sensor. In our field experiment, where ground truth was unavailable, the sources estimated to be inactive based on the complete set of measurements were found inactive (up to three decimal places of accuracy) at least 72% of the time even when estimated using just 54% of random measurements. In that setting, rate estimates of active sources were also found to be statistically robust. For direct validation of RESILIENT, we considered a separate public dataset involving 10 tracer experiments, and obtained a significant correlation coefficient of 0.89 between estimated and recorded emission rates, and that of 0.99 between predicted and measured concentration levels at sensor locations.

Evaluation of a new air water generator based on absorption and reverse osmosis

The evaluation of a new air water generator (AWG) based on absorption and reverse osmosis is described. For the evaluation, an aqueous lithium bromide solution has been selected from a wide range of liquids as the absorbent. At high salt mass fractions, the aqueous lithium bromide solution has a low vapour pressure and a high osmotic pressure. The low vapour pressure ensures that the water vapour can be absorbed from the air, but the high osmotic pressure leads to high pressures over the membrane. Due to the high osmotic pressures, several reverse osmosis membrane modules are necessary and salt solution has to be present on both sides of the membrane, which leads to an additional inlet on the permeate side. Models for the absorber, the reverse osmosis membrane module and the complete multi-stage reverse osmosis system have been developed in Python. The model of the complete system has then been used to simulate the performance of the AWG at different boundary conditions. The simulations have shown that based on the defined assumptions, extracting water from the air with absorption and reverse osmosis is possible and that the energy demand per litre of pure water is similar to AWG systems which use condensation.

Kinetic modeling of the alkaline deproteinization of Nile-tilapia skin for the production of collagen

A new phenomenological model, based on a second order dissolution kinetics, was developed for the alkaline removal of non-collagenous protein (NCP) from the skin of Nile tilapia (SNT). This model allows estimating the liquid concentration of NCP in terms of temperature, skin size, NaOH concentration and time. This model was fitted with 135 experiments averaging a R² of 0.99. The root-mean-square deviation and the mean-absolute-percentage error of the model were 0.0041 and 3.15%, respectively. The Arrhenius-activation energy was 15-122 kJ mol^-1. Multi-objective optimization led to the highest NCP extraction (NCPE) of 24.3% and to the lowest loss of collagen (LC) of 1.3%, with R² coefficients of 0.98 and 0.92, respectively. Ultimately, SNT deproteinized under optimal conditions was subjected to acid extraction and purification. FTIR and SEM analyses indicated that the product was a Type I collagen that could be used in the pharmaceutical industry.

Isolation and identification of cholestane and dihydropyrene from Calophyllum inophyllum

The highest population of Calophyllum inophyllum is in Indonesia. One of the bioactive compound contained in C. inophyllum leave is cholestane. The extraction method was employed to obtain crude extract from these leaves. It was followed by identification of the bioactive compounds. The purpose of this research was to develop a process for isolating and identifying cholestane and dihydropyrene from methanolic extract of C. inophyllum leaves in high yield and purity. The effect of crude extract to non-polar solvent mass ratio and non-polar solvent types on the separation of the bioactive compounds were also systematically investigated. New compounds (trans-2-[2-(trifluoromethyl)phenyl]-10b,10c-dimethyl-10b, 10c-dihydropyrene and anti-4-aza-B-homo-5.alpha-cholestane-3-one) were also identified in C. inophyllum leaves. The successful separation was obtained by employing CS₂ as the solvent and crude extract to CS₂ mass ratio of 1/10 (g/g).

Optimization of process conditions for tannin content reduction in cassava leaves during solid state fermentation using Saccharomyces cerevisiae

Cassava leaves are a crucial source of alternative protein resources for both humans and livestock in developing societies in African and Asian countries that do not have easy access to available protein sources. Hence, cassava has the capacity to promote the economic development of these countries and provide food security. However, it has some disadvantages due to the anti-nutrient compounds present in its tissues, which limits the nutritional value of cassava leaves. Thus, proper processing of cassava leaves is essential in order to reduce the anti-nutrients to a safer limit before utilization. This study focuses on reducing the tannin content of cassava leaves during solid-state fermentation using Saccharomyces cerevisiae. In addition, the Box-Behnken design of the Response Surface Methodology was applied to optimize various process parameters, such as carbon concentration, nitrogen concentration, moisture content, and incubation time for maximum reduction of tannin content in cassava leaves. A quadratic model was developed for the reduction of tannin content, which resulted in a perfect fit of the experimental data (p < 0.01). The optimal conditions were found at 1.4% (w/w) of carbon concentration, 0.55% (w/w) of nitrogen concentration, 57% (v/w) moisture content, and an incubation time of 96 h. The minimum tannin content obtained under these conditions was 0.125%, which indicated a reduction of 89.32 % in tannin content. Conversely, the protein content was increased with a further increase in fermentation time from 24 to 96 h (from 10.08 to 14.11-16.07 %). Furthermore, the ability of Saccharomyces cerevisiae to produce tannase under solid-state fermentation of cassava leaves was also studied. The maximum yield was obtained with an enzyme activity of 0.53 U/gds after 72 h of incubation.

Pore-scale simulations of concentration tails in heterogeneous porous media

The retention of contaminants in the finest and less-conductive regions of natural aquifer is known to strongly affect the decontamination of polluted aquifers. In fact, contaminant transfer from low to high mobility regions at the back end of a contaminant plume (i.e. back diffusion) is responsible for the long-term release of contaminants during remediation operation. In this paper, we perform pore-scale calculations for the transport of contaminant through heterogeneous porous media composed of low and high mobility regions with two objectives: (i) study the effect of permeability contrast and solute transport conditions on the exchange of solutes between mobile and immobile regions and (ii) estimate the mass of contaminants sequestered in low mobility regions based on concentration breakthrough curves.

Spatio-temporal distribution and sources of Pb identified by stable isotopic ratios in sediments from the Yangtze River Estuary and adjacent areas

To understand the spatio-temporal distribution and sources of Pb in the sediments of the Yangtze River Estuary and its adjacent areas, 25 surface sediments and 1 sediment core were collected from the study areas. The concentrations of Al and Pb of these sediments exhibit a decreasing trend from the nearshore towards the offshore, with higher concentrations in the coastal areas of the East China Sea (ECS) and southwest of Jeju Island. According to the stable isotopic ratios of Pb, in combination with the elemental ratios and clay mineral data, it is inferred that sedimentary Pb in the surface sediments of the coastal areas of the ECS may come primarily from the Yangtze River, while the Pb southwest of Jeju Island is probably derived from both the Yangtze and Yellow Rivers. The particulate Pb derived from the Yangtze River was possibly dispersed along two paths: the path southward along the coastline of the ECS and the path eastward associated with the Changjiang Diluted Water (CDW), which crosses the shelf of the ECS towards the area southeast of Jeju Island. Although the Yangtze River Basin witnessed rapid economic development during the period from the late 1970s to the middle 1990s, the influence of human activity on Pb concentration remained weak in the Yangtze River Estuary. Since the early 2000s, however, sedimentary Pb has been significantly increasing in the coastal mud areas of the ECS due to the increasing influence of human activity, such as the increase in atmospheric emission of anthropogenic Pb in China, construction of the Three Gorges Dam (TGD), and the construction of smaller dams in the upper reaches of the Yangtze River. Coal combustion and the smelting of non-ferrous metals are possible anthropogenic sources for the sedimentary Pb in the Yangtze River Estuary.

Comparative analysis of time series of marine litter surveyed on beaches and the seafloor in the southeastern North Sea

The comparative analysis of marine litter in different marine compartments has rarely been attempted. In this study, long-term time series of marine litter abundance on the seafloor and on the coast, both from the southeastern North Sea, were analyzed for temporal trends and correlations. On four beach sections of 100 m length, mean abundances of total beach litter collected four times a year from 2002 to 2008 varied between 105 and 435 items. Mean densities of total inorganic litter on the seafloor amounted to 10.6 ± 9.7 kg km(-2) in the offshore region (2001-2010) and 13.7 ± 12.6 kg km(-2) in the Wadden Sea (1998-2007), respectively. In the offshore region, there was no significant long-term trend, while in the Wadden Sea, densities of marine litter declined significantly. Correlations between time series were weak, indicating different sources and transport processes responsible for compositions of beach litter and litter on the seafloor. Decreases in inputs from fisheries and substantial export due to resuspension are discussed as reasons for the decrease in litter on the seafloor in the Wadden Sea.