Suspended Particulate Matter Samples Research Articles

PCBs, HCB and PAHs in the seawater of Arctic fjords – Distribution, sources and risk assessment

In the present study, we examine contamination with PCBs, HCB and PAHs in the seawater of Arctic fjords (Hornsund, Kongsfjorden and Adventfjorden) which differ in environmental conditions and are particularly sensitive to climate change. We also investigate how the melting glaciers and ocean currents may affect the distribution and fate of target compounds in the seawater column in the fjords. The ∑7 PCB, HCB and ∑12 PAH concentrations in seawater ranged from, respectively: 0.002 to 41.2 ng/L; from LOQ to 233 ng/L; and from 0.196 to 311 ng/L. The research indicates that the concentrations of contaminants detected in Arctic fjords depend on the physicochemical properties of these compounds, local human activity and occurrence of glacier meltwaters. Detected HCB and PAH concentrations in most of the seawater samples were at levels classified as harmless, however in 30 out of 80 analysed suspended particulate matter samples some compounds were present at toxic levels.

Viability and stress state of bacteria associated with primary production or zooplankton-derived suspended particulate matter in summer along a transect in Baffin Bay (Arctic Ocean)

In the framework of the GreenEdge Project (whose the general objective is to understand the dynamic of the phytoplankton spring bloom in Arctic Ocean), lipid composition and viability and stress state of bacteria were monitored in sea ice and suspended particulate matter (SPM) samples collected in 2016 along a transect from sea ice to open water in Baffin Bay (Arctic Ocean). Lipid analyses confirmed the dominance of diatoms in the bottommost layer of ice and suggested (i) the presence of a strong proportion of micro-zooplankton in SPM samples collected at the western ice covered St 403 and St 409 and (ii) a high proportion of macro-zooplankton (copepods) in SPM samples collected at the eastern ice covered St 413 and open water St 418. The use of the propidium monoazide (PMA) method allowed to show a high bacterial mortality in sea ice and in SPM material collected in shallower waters at St 409 and St 418. This mortality was attributed to the release of bactericidal free fatty acids by sympagic diatoms under the effect of light stress. A strong cis-trans isomerization of bacterial MUFAs was observed in the deeper SPM samples collected at the St 403 and St 409. It was attributed to the ingestion of bacteria stressed by salinity in brine channels of ice by sympagic bacterivorous microzooplankton (ciliates) incorporating trans fatty acids of their preys before to be released in the water column during melting. The high trans/cis ratios also observed in SPM samples collected in the shallower waters at St 413 and St 418 suggest the presence of positively or neutrally buoyant extracellular polymeric substances (EPS)-rich particles retained in sea ice and discharged (with bacteria stressed by salinity) in seawater after the initial release of algal biomass. Such EPS particles, which are generally considered as ideal vectors for bacterial horizontal distribution in the Arctic, appeared to contain a high proportion of dead and non-growing bacteria.

Under the influence of regulations: spatio-temporal trends of the UV filter 2-Ethylhexyl-4-methoxycinnamate (EHMC) in German rivers

BackgroundGlobally, 2-Ethylhexyl-4-methoxycinnamate (EHMC) is one of the most commonly used UV filters in sunscreen and personal care products. Due to its widespread usage, the occurrence of EHMC in the aquatic environment has frequently been documented. In the EU, EHMC is listed under the European Community Rolling Action Plan (CoRAP) as suspected to be persistent, bioaccumulative, and toxic (PBT) and as a potential endocrine disruptor. It was included in the first watch list under the Water Framework Directive (WFD) referring to a sediment PNEC of 200 µg/kg dry weight (dw). In the light of the ongoing substance evaluation to refine the environmental risk assessment, the objective of this study was to obtain spatio-temporal trends for EHMC in freshwater.We analyzed samples of suspended particulate matter (SPM) retrieved from the German environmental specimen bank (ESB). The samples covered 13 sampling sites from major German rivers, including Rhine, Elbe, and Danube, and have been collected since mid-2000s.ResultsOur results show decreasing concentrations of EHMC in annual SPM samples during the studied period. In the mid-2000s, the levels for EHMC ranged between 3.3 and 72 ng/g dw. The highest burden could be found in the Rhine tributary Saar. In 2017, we observed a maximum concentration ten times lower (7.9 ng/g dw in samples from the Saar). In 62% of all samples taken in 2017, concentrations were even below the limit of quantification (LOQ) of 2.7 ng/g dw.ConclusionsThe results indicate a general declining discharge of EHMC into German rivers within the last 15 years and correspond to the market data. Although the measured levels are below the predicted no-effect level (PNEC) in sediment, further research should identify local and seasonal level of exposure, e.g., at highly frequented bathing waters especially in lakes. In addition, possible substitutes as well as their potentially synergistic effects together with other UV filters should be investigated.

Carbon and nitrogen stable isotopes of copepods in a tidal estuarine system in Maryland, USA

The carbon and nitrogen stable isotope ratios of copepods, particularly Acartia tonsa and suspended particulate organic matter (SPOM) samples, collected seasonally (2014 to 2017) from 13 sites in the tidal estuaries of Maryland were analyzed. We hypothesized that copepods at sites close to the mouths of lagoon tributaries have more depleted δ13C than copepods at sites near the inlets, and that variations in the δ13C values of copepods mirror that of the SPOM. Copepod δ13C values ranged from −27.8‰ to −19.4‰, and that of SPOM from −26.8 to −20.3‰. Mean copepod δ13C value (−21.8‰±0.4) at a site close to the ocean was the highest, whereas the lowest value (−24.4‰±0.5) occurred at a site located at the mouth of St. Martin River. δ15N copepod values varied from 2.9‰ to 13.0‰ (mean=9.2‰±0.1); that of SPOM was −0.58 to 10.51‰ (mean=5.7‰±0.2). Reduction in the δ15N mean values from a site near the Ocean City inlet (10.2±0.4‰) to a site close to the tributaries (8.5±0.6‰) suggests that copepods at the site near Ocean City inlet likely fed on food items that contained more marine phytoplankton with enriched δ15N and heterotrophic protists, than copepods at a site near the river mouth. The highest (−21.9‰±0.4) and lowest (−25.8‰±0.3) mean copepod δ13C values were observed in summer 2015 and winter 2017, whereas the highest (10.8‰±0.2) and lowest (7.1‰±0.7) mean copepod δ15N values were recorded in winter and fall 2016, respectively. δ15N enrichment between copepods and SPOM ranged from 1.0‰ to 8.9‰ (mean: 3.4‰). The highest enrichment observed in February 2016 stemmed from a reduction in SPOM δ15N values, after a major storm event, which was unaccompanied by a decrease in Acartiaδ15N. Copepod and SPOM δ13C and δ15N values, displayed similar spatial patterns and were positively correlated; enrichment at sites near the ocean and depletion near the river mouth indicating that SPOM composition influenced copepods diets in the lagoons.

Levels of dioxins and dioxin-like polychlorinated biphenyls in seawater from the Hornsund fjord (SW Svalbard)

Knowledge of contaminant distribution is important, particularly in the vulnerable first results about the occurrence of seventeen polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans and twelve dioxin-like polychlorinated biphenyls in arctic fjord seawater are reported. The contaminants were measured in 10 samples of suspended particulate matter collected in Hornsund (Svalbard). The ∑PCDD/F and ∑dl-PCB concentrations ranged from 0.066 to 231.47 pg/L and from 2.43 to 46.43 pg/L respectively. In terms of total PCDD/Fs, in general highly chlorinated PCDFs constituted the most significant fraction. Among dl-PCB compounds, PCB118 was the dominant congener. The toxicity equivalent for the samples ranged from 0.0008 to 1.90 pg I-TEQ/L for ∑PCDD/Fs, while for ∑dl-PCB it ranged from 0.0002 to 0.024 pg WHO05-TEQ/L. High concentrations of dioxins and dl-PCBs in some samples indicated that those contaminants could pose a threat to marine biota.

Particulate Mercury and Particulate Organic Matter in the Itenez Basin (Bolivia)

In rivers and other freshwater bodies, the presence of mercury can be due to direct contamination by anthropic activities such as gold mining. However, it can also be attributed to atmospheric deposition and erosion, runoff, or lixiviation from surrounding soils. In the case of the Amazon rainforest, high mercury contents have been reported for litter and topsoil, which could affect the mercury concentrations in water bodies. Samples of suspended particulate matter were obtained from a transect of the Itenez River, associated lakes, and some of its tributaries. The aim was to obtain information on particulate mercury’s origin in the study area and determine the relationship between particulate mercury and particulate organic carbon. The concentration of mercury, organic matter, and the C:N ratio of the suspended matter was determined. The concentration of particulate mercury by water volume depended on changes in suspended matter loads, which in turn were mostly affected by the nature of the watershed or sediment resuspension. The observed values for the percentage of organic matter and the C:N ratio suggest that most of the mercury content in rivers and lakes originated from soils. A positive correlation was found between mercury concentration by weight of particulate matter and organic carbon content in particles. This correlation might be due to the direct binding of mercury to organic matter through functional groups like thiols or to an indirect effect of oxyhydroxides that can adsorb mercury and are associated with organic matter.

Polychlorinated biphenyls and organochlorine pesticides in water and sediment from Volturno River, Southern Italy: occurrence, distribution and risk assessment

BackgroundTo assess the Volturno River pollution and its environmental impact on the Tyrrhenian Sea (Central Mediterranean Sea) caused by Polychlorinated biphenyls (PCBs) and Organochlorine pesticides (OCPs), 32 PCBs and aldrin, α-BHC, β-BHC, δ-BHC, γ-BHC (lindane), 4,4′- DDD, 4,4′-DDE, 4,4′-DDT, dieldrin, endosulfan I, endosulfan II, endosulfan sulphate, endrin, heptachlor, heptachlor epoxide (isomer B) and methoxychlor have been selected and were analyzed in three different phases: dissolved phase (DP), suspended particulate matter (SPM) and sediments. PCBs and OCPs were extracted using an SPE column for the DP and glass fiber filter for SPM and sediment samples. Cleaned extracts were analyzed by gas chromatography with electron capture detector (ECD) and mass spectrometry (MS) detector for PCBs and OCPs, respectively.ResultsPollutants discharges of PCBs and OCPs into the sea were calculated in about 106.9 kg year−1 (87.1 kg year−1 of PCBs and 19.7 kg year−1 of OCPs), showing that this river could be a major source of PCBs and OCPs pollution to the Central Mediterranean Sea. Total concentrations of PCBs ranged from 4.1 to 48.0 ng L−1 in water (sum of DP and SPM) and from 4.3 to 64.3 ng g−1 in sediment samples. The concentrations of total organochlorine pesticides (OCPs) obtained in water (sum of DP and SPM) ranged from 0.93 to 8.66 ng L−1 and from 0.52 to 9.89 ng g−1 in sediment samples. Principal component analysis shows that all PCB compounds are more likely to come from surface runoff than an atmospheric deposition.ConclusionThe data show that higher levels of PCBs and OCPs were found in sediment samples than in DP and SPM samples, which are an indication of no fresh inputs of these compounds. Based on our results, unintentionally produced PCBs by industrial processes (and other processes) were considered to be the main sources of PCBs in Volturno River and Estuary sediments. Considering the Sediment Quality Guidelines (SQGs), the Ecological Risk Index (ERI), the Risk Quotient (RQ) and the USEPA Environmental Quality Standards (EQS), the Volturno River and its Estuary would be considered an area in which the integrity is possibly at risk.

Aquatic suspended particulate matter as source of eDNA for fish metabarcoding

The use of environmental DNA (eDNA) for monitoring aquatic macrofauna allows the non-invasive species determination and measurement of their DNA abundance and typically involves the analysis of eDNA captured from water samples. In this proof-of-concept study, we focused on the novel use of eDNA extracted from archived suspended particulate matter (SPM) for identifying fish species using metabarcoding, which benefits from the prospect of retrospective monitoring and also analysis of fish communities through time. We used archived SPM samples of the German Environmental Specimen Bank (ESB), which were collected using sedimentation traps from different riverine points in Germany. Environmental DNA was extracted from nine SPM samples differing in location, organic content, and porosity (among other factors) using four different methods for the isolation of high-quality DNA. Application of the PowerSoil DNA Isolation Kit with an overnight incubation in lysis buffer, resulted in DNA extraction with the highest purity and eDNA metabarcoding of these eDNA fragments was used to detect a total of 29 fish taxa among the analyzed samples. Here we demonstrated for the first time that SPM is a promising source of eDNA for metabarcoding analysis, which could provide valuable retrospective information (when using archived SPM) for fish monitoring, complementing the currently used approaches.

Temporal and spatial variability of the suspended particulate matter in the Gdansk Deep and Eastern Gotland Basin

The work was carried out in the south-eastern part of the Baltic Sea on the meridional section along the Russian–Polish border during 2015–2018 using the CTD-sounding. The suspended particulate matter samples were taken with the use of ultrafiltration of sea water (0.4 micron filters). The research was focused on identifying the temporal and spatial variability of suspended particulate matter distribution after a series of inflows of the North Sea waters in 2014–2016. The vertical structure of the suspended particulate matter distribution in the south-eastern Baltic, both on a seasonal and interannual scale, contains the main features common for all marine basins, namely increased concentrations of SPM at the sea surface and bottom and an intermediate layer of minimum concentrations located at a depth of 50–70 m. Seasonal fluctuations in the SPM concentration are very significant and are mainly due to the seasonal variation of bioproduction in the surface layer of the sea and the flow of rivers. The confirmation of the barrier role of density boundaries (thermocline and halocline) in sedimentation and geochemical processes has not been obtained.

Dynamics of Hg and MeHg in the Madeira River basin (Western Amazon) before and after impoundment of a run-of-river hydroelectric dam

The impact of a hydroelectric run-of-river (RoR) dam construction on the dynamics of total mercury (THg) and methylmercury (MeHg) is of interest to the environment and health of human and wild life. We monitored (May 2010 to October 2018) THg and MeHg in the waters and in the suspended particulate matter (SPM) of the Madeira River and its tributaries (before and after dam construction) to evaluate changes upstream and downstream from the Santo Antonio Hydroelectric Dam (SAHD). We collected 2826 samples of water and SPM at sampling stations upstream (UPMD-01, UPMD-02 and UPMD-03) and downstream the Madeira River (DWMD-04, DWMD-05 and DWMD-06), and Tributaries upstream (Branco River, Jaci-Parana River, Jatuarana-I Igarapé, Contra River, Caripunas Igarapé, Ceara Igarapé, and Teotonio Igarapé) and downstream (Jatuarana-II Igarapé and Belmont Igarapé) from the SAHD and monitored water and the total load of SPM. SPM was significantly higher in the Madeira River (median: 178.63 mg.L−1) than in upstream and downstream tributaries (median: 15.30 mg.L−1); however, the THg and MeHg concentrations were significantly higher in the tributaries (median: 161.14 ng g−1 and 9.03 ng g−1, respectively) than in the mainstream Madeira River (median = 57.06 ng g−1 and 1.63 ng g−1, respectively). THg concentration in the water was significantly higher in the mainstream Madeira River (median = 6.51 ng.L−1) than in the tributaries (median = 2.57 ng.L−1). However, the percentage of methylation in the tributaries (median = 4.9%) was 4-times higher than in the Madeira River (median: 1.3%). The significantly higher MeHg percentages in the tributaries may indicate natural (hydro-bio-geochemical factors) still predominant in this changing landscape of the Western Amazon. So far, the data suggest that this RoR has not yet impacted the THg and MeHg concentrations.

Correlation between the ratio of 5-methyl hexamethylated to pentamethylated branched GDGTs (HP5) and water depth reflects redox variations in stratified lakes

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are potentially valuable biomarkers for paleoclimatic and paleoenvironmental studies. However, multiple factors controlling their variations in lake sediments hamper the widespread application of brGDGT-based proxies. Here we investigate brGDGTs in water column suspended particulate matter (SPM) and surface sediments in a series of lakes with a wide range of depths from three main volcanic fields of northeastern China. The brGDGT distribution patterns from SPM and surface sediments of these lakes differ greatly from those of surrounding soils, indicating a predominant aquatic origin for brGDGTs. We find that the ratio of 5-methyl hexamethylated and pentamethylated brGDGTs with no cyclopentane rings (IIIa/(IIa + IIIa); designated as HP5) is strongly correlated with water depth. Re-examination of published brGDGT data from SPM samples in redox-stratified Lake Lugano reveals similar relationships, whereas such correlations are much weaker in Lake Superior which does not have an anoxic hypolimnion. Importantly, we find that there is strong correlation between HP5 and dissolved oxygen in water column of the redox-stratified lakes, suggesting that the observed apparent HP5–water depth correlation may be primarily attributed to depth-progressive shifts in the brGDGT-producing bacterial communities with different redox requirements (aerobic, facultative anaerobic, and anaerobic bacteria). Notably, brGDGT methylation indices (MBTʹ5ME and MBTʹ6ME) of surface sediments display poor correlations with air temperatures in our study lakes, calling for caution in applying MBTʹ5ME and MBTʹ6ME as temperature proxies in these lakes.

Connecting land use−land cover and precipitation with organic matter biogeochemistry in a tropical river–estuary system of western peninsular India

Organic matter (OM) composition changed due to land use ─ land cover (LULC) and hydrology modification, has distinctive linkage towards sustainable environment management in tropical river systems. It is crucial in small river systems, which experience delay of freshwater flow to the estuaries due to headwater damming, also LULC alteration along the entire basin. In order to understand this fundamental linkage in tropical Zuari river-estuary (ZRE), we analyzed multi-proxy data of organic carbon to total nitrogen ratio (Corg/N), stable organic carbon isotope (δ13Corg) and lignin phenols measured in seasonally collected suspended particulate matter (SPM) and sediment samples. Results highlighted about moderate seasonality of OM tracers, with a significant effect of LULC alteration, which nevertheless a striking feature in monsoon-fed river-estuaries of peninsular India. Particulate Corg export from ZRE estimated to be 20 × 103 kg yr−1, was much lower as compared to tropical river-estuary systems elsewhere. OM fraction from vascular plant (mangroves) contributed to SPM and sediment was 15% and 40%, respectively, calculated using a Bayesian mixing calculation through Stable isotope analysis in R (SIAR). Presence of mudflat LULC in the estuarine region notably caused 20% decrease in Corg and 60% increase in lignin phenol (Λ8) as compared to their limits in upstream. This is although mudflat accounts only 3% of ZRE catchment. The degree of shifts in OM tracers highlights towards efficient entrapment, transformation and/or utilization of riverine OM in the mudflats of ZRE. Accelerated human induced LULC dampens the seasonality of OM characteristics and flow is highlighted through this study, which is essential towards sustainable environmental management practice in small rivers of India and World.

The impact of discharge reduction activities on the occurrence of contaminants of emerging concern in surface water from the Pearl River.

"Swimming across the Pearl River" is an annual large-scale sporting event with great popularity in Guangzhou. To reduce the risk of swimmers' exposure to various contaminants in the Pearl River during swimming activities, the local government limits direct sewage and effluent discharge from urban channels during the event. However, the impact of discharge reduction on some contaminants of emerging concern (CECs), such as organophosphorus flame retardants (OPFRs), bisphenol analogues (BPs), and triclosan remains unknown. In the present study, the concentrations of CECs, as well as ammonia-nitrogen (NH3-N), dissolved organic carbon, and chemical oxygen demand, were measured in aqueous and suspended particulate matter (SPM) from the Guangzhou reaches of the Pearl River. The concentration ranges of sixteen OPFRs, eight BPs, and triclosan were 21.2-91.0, 8.46-37.3, and 1.47-5.62ng/L, respectively, in aqueous samples, and 25.2-492, 14.0-86.3, and 0.69-17.5ng/g, respectively, in SPM samples. Hydrophobic and π-π interactions could be contributing to the distribution of CECs. Principal component analysis indicated that consumer materials, manufacturing, and domestic sewage might be the main sources of the CECs. In addition, our study showed that the concentrations of CECs did not change considerably before or after discharge reduction activities, although NH3-N showed a substantial decrease following pollution control measure. The results demonstrated that temporary reductions of contaminant discharges to the Pearl River had only limited effect on the levels of CECs. Further research is needed to investigate the distributions and potential health risks of CECs in the Pearl River.

Calculating sources of combustion-derived particulates using 1-nitropyrene and pyrene as markers

Airborne particulate matter (PM) contains numerous hazardous polycyclic aromatic hydrocarbons (PAHs) as well as their functionalized congeners. However, the lack of useful methods to identify the sources of PM has hindered the development of researches in atmospheric and public health fields. This report proposes a new method for estimating the source contribution of combustion-derived particulate (Pc) by using 1-nitropyrene (1-NP) and pyrene (Pyr) as markers. This is premised on the fact that the formation of nitrogen oxides in the flame gas and the subsequent nitration of PAHs are functions of combustion temperature and therefore the concentration ratios of NPAHs to PAHs are highly temperature dependent. This method divides combustion sources into two groups - high and low temperatures - which here are respectively represented by automobile engine and coal combustion in urban areas. Formulae are derived for combustion-derived particulate (Pc), whose fraction in the total particulate is y (0 < y < 1), and particulates from combustion sources with high temperatures (Ph), whose fraction in Pc is x (0 < x < 1), and low temperatures (Pl), whose fraction is (1 －x). When concentrations of 1-NP and Pyr in Ph and Pl are known, values x and y can be calculated from the formulae by determining atmospheric 1-NP and Pyr concentrations at monitoring sites. Then atmospheric concentrations of Pc, Ph and Pl can be calculated. The proposed method has been applied for total suspended particulate matter (TSP) samples collected in Kanazawa and Kitakyushu (Japan) and Beijing (China) having different types of atmospheric pollution to clarify the change of contributions of automobiles and coal combustion.

Seasonal Variations in the Grain Size Distribution and Mineral Composition of Suspended Particulate Matter of the Northern Dvina River

The paper presents the first results of a study of seasonal variations in the grain size distribution and mineral compositions of suspended particulate matter (SPM) of the Northern Dvina River. The SPM samples were collected every month during 2016–2017 at the outlet of the Kuznetchiha arm to Dvina Bay of the White Sea. The grain size fractions were separated by Petelin’s water-mechanical method with retention of fractions for subsequent analyses using an electron microscope, energy-dispersion microanalyzer, and X-ray difractometer. The results demonstrated that the pelitic and subcolloidal fractions predominated in the grain size distribution of river SPM, with subordinate coarser fractions. Seasonal variations in the SPM concentration and the total amount of detrital and clay minerals are influenced by river water discharge and achieved a maximum in high water periods (spring flood and partly at the end of summer–autumn heavy rains). The subcolloidal fraction in the March sample stands out in the fine fraction distribution. Its share in this sample was the highest among these fractions throughout the year. The reason is probably related to the highest content of fine dispersed detrital minerals in the fraction. The question of why this is encountered only in March remains open.

Assessment and sources of heavy metals in suspended particulate matter in a tropical catchment, northeast Thailand

Since the suspended particulate matter (SPM) is a vital heavy metal transporter of the river systems, assessment of heavy metals contamination in SPM is significant as the first step of the high-efficiency surface water environment management and further foundation of water resources sustainability. However, this assessment is rare in developing countries (e.g., Thailand, agriculture is the main economic pillar). Fluvial heavy metal pollution prevention strategy is urgently required in these areas for reducing human exposure to metal contamination. For this purpose, the assessment of eight selected heavy metals of 52 SPM samples in a Thailand tropical river (Mun River) was conducted. The findings suggest that the contents of heavy metals in SPM are Mn (4616.7 mg kg−1) > Zn (223.9 mg kg−1) > V (109.1 mg kg−1) > Cr (100.1 mg kg−1) > Ni (51.0 mg kg−1) > Cu (27.6 mg kg−1) > Pb (14.3 mg kg−1) > Cd (10.7 mg kg−1). A relatively large proportion of heavy metals (e.g., Mn, 89.5%; Zn, 54.2%) are transported in suspended loads in Mun River. Heavy metals accumulation assessment suggests that Cd (EF = 17.5, Igeo = 3.7) and Mn (EF = 14.3, Igeo = 2.1) are extremely enriched in SPM, while the other metals are slightly enriched or not enriched. Principal component (PC) analysis extracted three PCs. PC 1 with a high loading of Mn, Zn, Cd, Pb reflecting these metals mainly from anthropogenic emissions, PC 2 (V and Cu) is primarily characterized by the natural sources (e.g., rock weathering), while PC 3 (Cr and Ni) can be defined as the result of combined action of natural and anthropogenic inputs. Risk assessment denotes that Cd is the major toxicity of SPM with a high toxic risk index (TRICd = 9.4, 54% of the total TRI) and the V, Cr, Mn, and Cd in SPM are the major exposure health risk, particularly for children (hazard index, HI > 0.1), more focus is required for these metals. In total, this study provides powerful support for the prevention of heavy metal pollution and the sustainability of water resources in the Mun River in such a developing country (Thailand).

Complex responses of suspended particulate matter in eutrophic river and its indicative function in river recovery process

Water environment and hydrodynamic condition of a river exerts a powerful influence on Suspended Particulate Matter (SPM) in rivers. Complex responses of SPM in rivers under changing water quality and hydrodynamic condition remain unclear and its indicative role in river recovery process is neglected. In this paper, twenty SPM samples were collected in June 2017 (rainy season) in Ziya River Mainstream (ZRM). The eutrophication levels of ZRM, sedimentation property and P fractions of SPM, and P-buffering intensity of the ZRM were investigated and compared with our previous research in arid season. The results showed eutrophication level was lower in rainy season than in arid season with mean Eutrophication Index (EI) values of 90.02 (seriously eutrophied) and 103.48 (extremely eutrophied), respectively. SPM in arid season has higher Loss On Ignition (LOI) content and was easier to remain suspension. The total amount of NaOH extracted Phosphorus (NaOH-P) and Organic Phosphorus (OP) fractions in SPM and Phosphorus (P) buffering intensity of ZRM were higher in arid season than in rainy season. Differences in water quality of a river can induce complex responses of SPM in its microstructure, P buffering ability and can act as a positive yet negative role in river eutrophication control. We put forward a P based river recovery process and suggest two-step river restoration measures, we point out rainy season is the reasonable timing to conduct measures in decreasing SPM concentration under the premise of mitigating P input. These results deepen our understanding on the role of SPM in P cycling in fluvial system and provide a new idea for river restoration work worldwide.

Distribution, sources, and behavior of PAHs in estuarine water systems exemplified by Salt River, Taiwan

Water, suspended particulate matter (SPM), and sediment samples were collected from Salt River in Taiwan and analyzed the concentrations of 16 types of polycyclic aromatic hydrocarbons (PAHs). The analysis results were used to examine the distribution, source, partition behavior, and potential ecological risks of PAHs in the estuarine water systems. The mean concentration of total PAHs in water, SPM, and sediment samples was 0.485–10.2 μg/L, 26.7–169 mg/kg dw, and 0.343–29.4 mg/kg dw, respectively. The highest concentration was found at the river mouth and decreased toward the river and sea with the tide. The distribution of the diagnostic ratios of PAHs showed that the combustion of coal and petroleum products are the main sources of PAHs in Salt River. The in site organic carbon normalized partition coefficients for SPM-water (K'oc(SPMW)) and sediment-water (K'oc(SedW)) were 2.8–4.5 and 4.6–6.0 (log units), respectively, increasing with the number of rings in PAHs. The values log K'oc(SedW) and log K'oc(SPM-W) showed a significant linear correlation with their octanol-water partition coefficients (p < 0.01), and their slopes were 0.427 and 0.316, respectively. The fugacity fraction was used to evaluate the exchange of PAHs in water-SPM-sediment systems. Results showed that in SPM, 2–4-ring PAHs tend to be released into water, whereas 5–6-ring PAHs in water tend to be adsorbed onto SPM. The exchange of PAHs between water and sediment occurs in the direction of adsorption onto sediment from water. The assessment of the mean risk quotient, total toxicity equivalence, and mean effect range-median quotient of PAHs showed that the PAHs in the water and SPM of Salt River may have moderate to high ecological risk. In sediment, PAHs in the lower reaches and estuary may pose moderate to high ecological risk, whereas PAHs in the middle and upper reaches show low to moderate ecological risk.

Trends for plasticizers in German freshwater environments – Evidence for the substitution of DEHP with emerging phthalate and non-phthalate alternatives

Plasticizers are marketed in high volumes and Di(2-ethylhexyl) phthalate (DEHP) is frequently detected in the environment and human populations. Industry had largely relied on DEHP until regulation started to restrict its marketing in 1999 due to environmental and human health concerns. The aim of this study was to obtain spatial-temporal trends for DEHP and its substitutes in German rivers. We have investigated suspended particulate matter (SPM) samples from the German Environmental Specimen Bank (ESB) for the presence of 23 plasticizers, i.e. 17 phthalates and 6 non-phthalates. The samples were collected in the last 10 years at 13 sites in large river basins in Germany such as the Rhine, Elbe and Danube. A decrease in DEHP concentrations was observed at all sampling sites between the mid-2000s and 2017. The maximum concentration for DEHP was determined in 2006 in samples from Rehlingen/Saar (6720 ng/g dry weight (dw)). By 2017, the DEHP concentration in Rehlingen had dropped to 2080 ng/g dw. Currently, Diisononyl phthalate (DINP) is the plasticizer with the highest levels in the SPM samples (maximum value 4150 ng/g dw in Rehlingen/Saar). Our results show that novel plasticizers such as Diisononylcyclohexane-1,2-dicarboxylate (DINCH) spread rapidly in surface waters after their market introduction. We have found several plasticizers of emerging concern in the environmental samples, the further use of which is currently under review under the EU chemicals regulation (REACH, registration, evaluation, authorisation and restriction of chemicals). In particular for Di(2-propylheptyl) phthalate (DPHP) a significant increase in concentration was observed at almost all sites between the mid-2000s and 2017, for example in Prossen/Elbe from 24 ng/g dw (2005) to 1380 ng/g dw (2017).

Trace element composition of size-fractionated suspended particulate matter samples from the Qatari Exclusive Economic Zone of the Arabian Gulf: the role of atmospheric dust

Abstract. We analyzed net-tow samples of natural assemblages of plankton, and associated particulate matter, from the Exclusive Economic Zone (EEZ) of Qatar in the Arabian Gulf. Size-fractionated suspended particles were collected using net tows with mesh sizes of 50 and 200 µm to examine the composition of small- and large-size plankton populations. Samples were collected in two different years (11 offshore sites in October 2012 and 6 nearshore sites in April 2014) to examine temporal and spatial variabilities. We calculated the excess metal concentrations by correcting the bulk composition for inputs from atmospheric dust using aluminum (Al) as a lithogenic tracer and the metal∕Al ratios for average Qatari dust. Atmospheric dust in Qatar is depleted in Al and enriched in calcium (Ca), in the form of calcium carbonate (CaCO3), relative to the global average Upper Continental Crust (UCC). To evaluate the fate of this carbonate fraction when dust particles enter seawater, we leached a subset of dust samples using an acetic acid–hydroxylamine hydrochloride (HAc–HyHCl) procedure that should solubilize CaCO3 minerals and associated elements. As expected, we found that Ca was removed in Qatari dust; however, the concentrations (ppm) for most elements actually increased after leaching because the reduction in sample mass resulting from the removal of CaCO3 by the leach was more important than the loss of metals solubilized by the leach. Because surface seawater is supersaturated with respect to CaCO3 and acid-soluble Ca is abundant in the particulate matter, we only used unleached dust for the lithogenic correction. Statistical analysis showed that for many elements the excess concentrations were indistinguishable from zero. This suggested that the concentrations of these elements in net-tow plankton samples were mostly of lithogenic (dust) origin. These elements include Al, Fe, Cr, Co, Mn, Ni, Pb, and Li. For several other elements (Cd, Cu, Mo, Zn, and Ca) the excess concentrations present after lithogenic correction are most likely of biogenic/anthropogenic origin. The excess concentrations, relative to average dust, for most elements (except Cd) decreased with distance from the shore, which may be due to differences in biology, currents, proximity to the coast, or interannual processes.