Contamination of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and plants of mangrove swamps in Shenzhen,China

The concentrations of 16 individual and total polycyclic aromatic hydrocarbons (∑PAHs) in sediments, roots and leaves of three mangrove swamps in Shenzhen, China, namely Futian, Baguang and Waterlands, were determined. The mean concentration of ∑PAHs in Futian (4480 ng g⁻¹) was significantly higher than that in Baguang (1262 ng g⁻¹) and Waterlands (2711 ng g⁻¹). Among the 16 PAHs, the concentration of naphthalene was the highest. Based on the ratios of phenanthrene/anthracene and fluoranthene/pyrene, PAHs in Futian and Waterlands came from petrogenic and pyrolytic sources, while Baguang was mainly from pyrolytic. More PAHs were accumulated in leaves, as reflected by its higher mean concentration of ∑PAHs (3697 ng g⁻¹) and bioconcentration factor of PAHs (BCF) (>1.5) than that in roots. The BCF values in plants collected from Futian were significantly higher than that from Waterlands. These results indicated that more attention should be paid to the PAH contamination in Futian.     

Comparison of hypoxia among four river-dominated ocean margins: The Changjiang (Yangtze), Mississippi,Pearl, and Rhône rivers

We examined the occurrence of seasonal hypoxia (O₂<2 mg l⁻¹) in the bottom waters of four river-dominated ocean margins (off the Changjiang, Mississippi, Pearl and Rhône Rivers) and compared the processes leading to the depletion of oxygen. Consumption of oxygen in bottom waters is linked to biological oxygen demand fueled by organic matter from primary production in the nutrient-rich river plume and perhaps terrigenous inputs. Hypoxia occurs when this consumption exceeds replenishment by diffusion, turbulent mixing or lateral advection of oxygenated water. The margins off the Mississippi and Changjiang are affected the most by summer hypoxia, while the margins off the Rhône and the Pearl rivers systems are less affected, although nutrient concentrations in the river water are very similar in the four systems. Spring and summer primary production is high overall for the shelves adjacent to the Mississippi, Changjiang and Pearl (1–10 g C m⁻² d⁻¹), and lower off the Rhône River (<1 g C m⁻² d⁻¹), which could be one of the reasons of the absence of hypoxia on the Rhône shelf. The residence time of the bottom water is also related to the occurrence of hypoxia, with the Mississippi margin showing a long residence time and frequent occurrences of hypoxia during summer over very large spatial scales, whereas the East China Sea (ECS)/Changjiang displays hypoxia less regularly due to a shorter residence time of the bottom water. Physical stratification plays an important role with both the Changjiang and Mississippi shelf showing strong thermohaline stratification during summer over extended periods of time, whereas summer stratification is less prominent for the Pearl and Rhône partly due to the wind effect on mixing. The shape of the shelf is the last important factor since hypoxia occurs at intermediate depths (between 5 and 50 m) on broad shelves (Gulf of Mexico and ECS). Shallow estuaries with low residence time such as the Pearl River estuary during the summer wet season when mixing and flushing are dominant features, or deeper shelves, such as the Gulf of Lion off the Rhône show little or no hypoxia.     

Biological,physical and chemical properties at the Subtropical Shelf Front Zone in the SW Atlantic Continental Shelf

The physical aspects of the Subtropical Shelf Front (STSF) for the Southwest Atlantic Continental Shelf were previously described. However, only scarce data on the biology of the front is available in the literature. The main goal of this paper is to describe the physical, chemical and biological properties of the STSF found in winter 2003 and summer 2004. A cross-section was established at the historically determined location of the STSF. Nine stations were sampled in winter and seven in summer. Each section included a series of conductivity-temperature-depth (CTD) stations where water samples from selected depths were filtered for nutrient determination. Surface samples were taken for chlorophyll a (Chl-a) determination and plankton net tows carried out above and below the pycnocline. Results revealed that winter was marked by an inner-shelf salinity front and that the STSF was located on the mid-shelf. The low salinity waters in the inner-shelf indicated a strong influence of freshwater, with high silicate (72 μM), suspended matter (45 mg l⁻¹), phosphate (2.70 μM) and low nitrate (1.0 μM) levels. Total dissolved nitrogen was relatively high (22.98 μM), probably due to the elevated levels of organic compound contribution close to the continental margin. Surface Chl-a concentration decreased from coastal well-mixed waters, where values up to 8.0 mg m⁻³ were registered, to offshore waters. Towards the open ocean, high subsurface nutrients values were observed, probably associated to South Atlantic Central Waters (SACW). Zooplankton and ichthyoplankton abundance followed the same trend; three different groups associated to the inner-, mid- and outer-shelf region were identified. During summer, diluted waters extended over the shelf to join the STSF in the upper layer; the concentration of inorganic nutrients decreased in shallow waters; however, high values were observed between 40 and 60 m and in deep offshore waters. Surface Chl-a ranged 0.07–1.5 mg m⁻³; winter levels were higher. Three groups of zoo and ichthyoplankton, separated by the STSF, were also identified. Results of the study performed suggest that the influence of freshwater was stronger during winter and that abundance distribution of Chl-a, copepods and ichthyoplankton was related to the Plata Plume Waters (PPW), rather than to the presence of the STSF. During summer, when the presence of freshwater decreases, plankton interactions seem to take place in the STSF.     

Distributions of polycyclic aromatic hydrocarbons in the Daliao River Estuary of Liaodong Bay, Bohai Sea (China)

The distributions of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in the aqueous phase, suspended particulate matter (SPM), sediment, and pore water of the Daliao River Estuary in Liaodong Bay, Bohai Sea (China). Total PAH concentrations ranged from 139.16 to 1717.87 ng L⁻¹ in surface water, from 226.57 to 1404.85 ng L⁻¹ dry weight in SPM, from 276.26 to 1606.89 ng g⁻¹ dry weight in sediments, and from 10.20 to 47.27 μg L⁻¹ in pore water. PAH concentrations were at relatively moderate levels in water, SPM, sediment and pore water in comparison with those reported for other estuary and marine systems around the world. Sedimentary PAH concentrations decreased offshore owing to active deposition of laterally-transported river-borne particles. PCA analysis of the possible PAH source suggested petrogenic and pyrolytic PAH inputs in the studied region.     

Concentration,composition and sources of PAHs in the coastal sediments of the exclusive economic zone (EEZ) of Qatar,Arabian Gulf

Surface sediments were collected from sixteen locations in order to assess levels and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Qatar exclusive economic zone (EEZ). Samples were analyzed for 16 parent PAHs, 18 alkyl homologs and for dibenzothiophenes. Total PAHs concentration (∑PAHs) ranged from 2.6 ng g⁻¹ to 1025 ng g⁻¹. The highest PAHs concentrations were in sediments in and adjacent to harbors. Alkylated PAHs predominated most of the sampling locations reaching up to 80% in offshore locations. Parent PAHs and parent high molecular weight PAHs dominated location adjacent to industrial activities and urban areas. The origin of PAHs sources to the sediments was elucidated using ternary plot, indices, and molecular ratios of specific compounds such as (Ant/Phe + Ant), (Flt/Flt + Pyr). PAHs inputs to most coastal sites consisted of mixture of petroleum and combustion derived sources. However, inputs to the offshore sediments were mainly of petroleum origin.     

Persistent organochlorine pollutants in Korean offshore waters: Squid (Todarodes pacificus) as a biomonitor

Persistent organochlorine pollutants (POPs) such as polychlorinated biphenyls (PCBs), dichlorodiphenyl trichloroethane and its metabolites (DDTs), chlordane compounds (CHLs), and hexachlorocyclohexanes (HCHs) were determined in Japanese common squid collected from the offshore waters of Korea. Liver accumulated higher levels of contaminants than mantle. The sums of DDTs, PCBs, CHLs and HCHs in liver were in the ranges of 164-4430 ng g⁻¹, 95-1030 ng g⁻¹, 15-121 ng g⁻¹, and 13-98 ng g⁻¹ on a lipid weight basis, respectively. Among the POPs, DDTs showed distinct regional difference in concentration levels and composition between the western and eastern offshore of Korea. One of the highest concentrations of DDTs so far recorded in the western offshore of Korea, that is Yellow Sea. This implies ongoing fresh input of technical DDT to this regional sea. HCHs were relatively high in the Yellow Sea as well, with an enhanced signal of γ-HCH indicating recent input of lindane. In contrast, CHLs showed higher level in the eastern offshore of Korea, that is East Sea, but PCBs showed an even distribution in both regions. Squid could be a useful bio-indicator for monitoring offshore water contamination by POPs.     

Monitoring pesticides in the Great Barrier Reef

Pesticide runoff from agriculture poses a threat to water quality in the world heritage listed Great Barrier Reef (GBR) and sensitive monitoring tools are needed to detect these pollutants. This study investigated the utility of passive samplers in this role through deployment during a wet and dry season at river mouths, two near-shore regions and an offshore region. The nearshore marine environment was shown to be contaminated with pesticides in both the dry and wet seasons (average water concentrations of 1.3-3.8 ng L⁻¹ and 2.2-6.4 ng L⁻¹, respectively), while no pesticides were detected further offshore. Continuous monitoring of two rivers over 13 months showed waters flowing to the GBR were contaminated with herbicides (diuron, atrazine, hexazinone) year round, with highest average concentrations present during summer (350 ng L⁻¹). The use of passive samplers has enabled identification of insecticides in GBR waters which have not been reported in the literature previously.     

Vertical profile,sources, and equivalent toxicity of polycyclic aromatic hydrocarbons in sediment cores from the river mouths of Kaohsiung Harbor,Taiwan

Six sediment cores collected at four contaminated river mouths and two harbor entrances in Kaohsiung Harbor (Taiwan) were analyzed to evaluate the sources and potential toxicity of polycyclic aromatic hydrocarbons (PAHs). PAHs presented the wide variations ranging from 369 ± 656 to 33,772 ± 14,378 ng g⁻¹ at the six sampling sites. The composition of PAHs presented a uniform profile reflecting the importance of atmospheric input from vehicle exhausts or coal combustion in the river mouths. PAHs diagnostic ratios indicated a stronger influence of coal combustion in the Salt River mouth and the prevalence of petroleum combustion and mixed sources in the other rivers and harbor entrances. PAHs toxicity assessment using the mean effect range-median quotient (m-ERM-q: 0.011–1.804), benzo[a]pyrene-toxicity equivalent (TEQ^carc: 22–2819 ng TEQ g⁻¹), and dioxin-toxicity equivalent (TEQ^fish: 37–5129 pg TEQ g⁻¹) identified the Salt River mouth near the industrial area of the harbor as the most affected area.     

Distribution and mass inventory of polycyclic aromatic hydrocarbons in the sediments of the south Bohai Sea, China

Recent occurrence, distribution and mass inventories of 16 priority polycyclic aromatic hydrocarbons (PAHs) proposed by USEPA in the south Bohai Sea (BS) were studied based on the analytical data of 71 surface sediment samples. The concentrations of 16 PAHs varied from 37 to 537 ng g⁻¹ (dry weight). A clear difference was observed between the coastal Bohai Bay (CBB) and its adjacent BS (ABS) in the distribution and compositions of PAHs. The petrogenic source of phenanthrene in CBB was attributable to the industrial wastewater, fugitive fuel leakages from ships and offshore oil production. Four to six ring PAHs were predominantly from the coal and wood combustions in the whole area. The estimated PAH input to the south BS (43,000 km², 56% of BS in area) was 36.6 ton yr⁻¹, indicating that the study area was one of the important reservoirs of PAHs in world.     

Perfluoroalkyl and polyfluoroalkyl substances in sediments from South Bohai coastal watersheds,China

This study investigated the concentrations and distribution of Perfluoroalkyl and polyfluoroalkyl substances (PFAS) in sediments of 12 rivers from South Bohai coastal watersheds. The highest concentrations of ΣPFAS (31.920 ng g⁻¹ dw) and PFOA (29.021 ng g⁻¹ dw) were found in sediments from the Xiaoqing River, which was indicative of local point sources in this region. As for other rivers, concentrations of ΣPFAS ranged from 0.218 to 1.583 ng g⁻¹ dw were found in the coastal sediments and from 0.167 to 1.953 ng g⁻¹ dw in the riverine sediments. Predominant PFAS from coastal and riverine areas were PFOA and PFBS, with percentages of 30% and 35%, respectively. Partitioning analysis showed the concentrations of PFNA, PFDA and PFHxS were significantly correlated with organic carbon. The results of a preliminary environmental hazard assessment showed that PFOS posed the highest hazard in the Mi River, while PFOA posed a relative higher hazard in the Xiaoqing River.     

Reevaluation of mixing among multiple water masses in the shelf: An example from the East China Sea

East China Sea (ECS) is bounded by the continent where the fourth largest river of Changjiang discharges large amounts of freshwater to the west and by the Kuroshio in the East and connected to the South China Sea via Taiwan Strait, therefore water characteristics are very complex and undergo great seasonal changes. The dominant source waters in the ECS are found to be Kuroshio Surface Water (KSW), Kuroshio Sub-surface Water (KSSW), Changjiang Diluted Water (CDW), and Taiwan Strait Warm Water (TSWW). Optimum multiparameter analysis (OMP) using temperature, salinity and ²²⁶Ra were applied to quantify the contribution of individual source water to the surface water of the ECS in summer. The successful application of radium isotope in OMP analysis demonstrates the usefulness of ²²⁶Ra in the discrimination of mixing among multiple water sources. In 1987, one interesting phenomenon was that the KSSW entered the surface with the upwelling at the margin of continental shelf, and affected the coastal water obviously. In 1999, the TSWW extended northward continuously up to the Changjiang Estuary.     

Enormous PCBs increase in oysters from the coast of Guangdong, China

PCBs equivalent to Aroclor 1242 and 1254 in soft tissues of oysters Crassostrea rivularis from the Guangdong coast, China, were measured using a GC-ECD. PCB concentrations (ng g⁻¹ d.w.) ranged from 30 to 2040 with an average of 315 in 2003-2007, and 0.35-1.43 with an average of 0.56 in 1989-1991. Annual averages were 0.61, 0.65, 313, 290 and 342 ng g⁻¹, respectively in 1989, 1991, 2003, 2006 and 2007. In east Guangdong, the Pearl River Estuary, and west Guangdong, regional means were 444, 273, 194 ng g⁻¹, respectively in 2003-2007, and 0.43, 0.78, 0.38 ng g⁻¹, respectively in 1989-1991, indicating PCB levels in oysters have risen greatly by ratios of 350-1032 compared with earlier data. PCB sources may derive from older transformers, printing materials and pressworks. Fortunately, current residual PCBs in the oysters were 0.004-0.253 mg kg⁻¹ (w.w.), still below hygienic criteria of China and developed countries.     

Spatio-temporal assessment of perfluorinated compounds in the Brisbane River system,Australia: Impact of a major flood event

Perfluorinated chemicals including PFOA and PFOS have been widely used in consumer products and have become ubiquitous pollutants widely distributed in the aqueous environment. Following a major flood event in 2011, water samples were collected along a spatial gradient of the Brisbane River system to provide an initial estimate of the release of PFASs from flooded urban areas. PFOA (mean concentrations 0.13–6.1 ng L⁻¹) and PFOS (mean concentrations 0.18–15 ng L⁻¹) were the most frequently detected and abundant PFASs. Mean total PFASs concentrations increased from 0.83 ng L⁻¹ at the upstream Wivenhoe Dam to 40 ng L⁻¹ at Oxley Creek, representing an urban catchment. Total masses of PFOA and PFOS delivered into Moreton Bay from January to March were estimated to be 5.6 kg and 12 kg respectively. From this study, urban floodwaters appear to be a previously overlooked source of PFASs into the surrounding environment.     

Hydrocarbon composition and distribution in a coastal region under influence of oil production in northeast Brazil

Waters and sediments from the Potiguar Basin (NE Brazilian coast) were investigated for the presence and nature of polycyclic aromatic hydrocarbons (PAH) and aliphatic hydrocarbons. The region receives treated produced waters through a submarine outfall system serving the industrial district. The total dispersed/dissolved concentrations in the water column ranged from 10-50 ng L⁻¹ for ∑16PAH and 5-10 μg L⁻¹ for total aliphatic hydrocarbons. In the sediments, hydrocarbon concentrations were low (0.5-10 ng g⁻¹for ∑16PAH and 0.01-5.0 μg g⁻¹ for total aliphatic hydrocarbons) and were consistent with the low organic carbon content of the local sandy sediments. These data indicate little and/or absence of anthropogenic influence on hydrocarbon distribution in water and sediment. Therefore, the measured values may be taken as background values for the region and can be used as future reference following new developments of the petroleum industry in the Potiguar Basin.     

Levels and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Lenga Estuary, central Chile

The Lenga Estuary is a small brackish wetland located southwest of San Vicente Bay, Region VIII, Chile. Surface sediment from nine sites in the estuary were analysed for PAHs and compared to Sediment Quality Guidelines (SQG). Sediment samples were freeze dried and soxhlet extracted for 16 h using DCM. Identification and quantification was carried out by HPLC. Organic carbon was also determined. Results showed total PAH concentrations ranged from 290 to 6118 (2025 ± 1975) ng g⁻¹ d.w. (2025 ± 1975). Results for organic carbon percentages ranged from 1% to 7%. Statistical analysis showed a significant positive correlation (Pearson test) between organic carbon percentage PAHs. Comparison of contaminant levels and international Sediment Quality Guidelines (SQG) (ERL and ER) suggested that sediment of the Lenga estuary did not show any ecotoxicologial risk for benthic organisms where high levels of PAHs were detected. Monitoring of this and other contaminants is recommended in Chile.     

Matrix bound phosphine in sediments of the yellow sea and its coastal areas

Matrix bound phosphine (MBP), a kind of chemically reduced phosphorus, has received limited attention in prevailing modeling of the phosphorus biogeochemical cycle. MBP has been found to occur in marine sediments. MBP in the sediments of the Yellow Sea and its coastal areas was measured by gas chromatography from 2004 to 2007. MBP levels in surface sediments were 0.19–38.24 ng kg⁻¹ in the shelf of the Yellow Sea, 0.34–17.15 ng kg⁻¹ in the Jiaozhou Bay, 2.11–71.79 ng kg⁻¹ in the Sanggou Bay and 0.28–319.32 ng kg⁻¹ in the rivers around the Jiaozhou Bay. High levels of MBP occurred in the northern and middle areas of the Yellow Sea. Obvious seasonal variation of MBP was observed in surface sediments of the Sanggou Bay, with the highest MBP level occurring in summer and the lowest in winter. MBP in surface sediments of the inner Jiaozhou Bay was higher than those in the outer region. MBP levels increased with depth in the top 5–10 cm sediments of the Jiaozhou Bay and on the intertidal flats. Environmental factors such as type of sediments, temperature, organic matter and human activity were found to affect the concentrations and distribution of MBP in marine sediments.     

Stir bar sorptive extraction-thermal desorption-gas chromatography-mass spectrometry: An effective tool for determining persistent organic pollutants and nonylphenol in coastal waters in compliance with existing Directives

A multi-residual method based on stir bar sorptive extraction coupled with thermal desorption-gas chromatography-mass spectrometry (SBSE-TD-GC-MS) has been developed to measure 49 organic pollutants (organochlorine pesticides, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers and nonylphenol) in seawater. Using 100 ml of water, the method exhibited good linearity, with recoveries between 86% and 118% and relative standard deviation between 2% and 24% for almost all compounds. The method was applied to determine target contaminants in Catalonian seawater, including coastal areas, ports and desalination plant feed water. Overall individual compound levels oscillated between 0.16 and 597 ng l⁻¹; PAHs and nonylpenol were the compounds found at the highest concentrations. The method provided LODs between 0.011 and 2.5 ng l⁻¹, lower than the Environmental Quality Standards (EQS) fixed by Directive 2008/105/EC. In compliance with the directive, this method can be used as a tool to survey target compounds and is aimed at protecting coastal ecosystems from chemical pollution.     

Air-sea CO2 fluxes in the southern Yellow Sea: An examination of the continental shelf pump hypothesis

The southern Yellow Sea (SYS), located to the north of the East China Sea (ECS), was considered part of the ECS when Tsunogai et al. (1999) proposed the “continental shelf pump” (CSP) hypothesis. However, the original CSP carbon dioxide (CO₂) uptake flux (2.9 mol C m⁻² yr⁻¹) appears to have been overestimated, primarily due to the differences between the SYS and the ECS in terms of their CO₂ system. In this paper, we estimated air-sea CO₂ fluxes in the SYS using the surface water partial pressure of CO₂ (pCO₂) measured in winter, spring, and summer, as well as that estimated in fall via the relationship of pCO₂ with salinity, temperature, and chlorophyll a. The results indicate that overall, the entire investigated area was a net source of atmospheric CO₂ during summer, winter, and fall, whereas it was a net sink during spring. Spatially, the nearshore area was almost a permanent CO₂ source, while the central SYS shifted from being a CO₂ sink in spring to a source in the other seasons of the year. Overall, the SYS is a net source of atmospheric CO₂ on an annual scale, releasing ∼7.38 Tg C (1 Tg=10¹² g) to the atmosphere annually. Thus, the updated CO₂ uptake flux in the combined SYS and ECS is reduced to ∼0.86 mol C m⁻² yr⁻¹. If this value is extrapolated globally following Tsunogai et al. (1999), the global continental shelf would be a sink of ∼0.29 Pg C yr⁻¹, instead of 1 Pg C yr⁻¹ (1 Pg=10¹⁵ g).The SYS as a net annual source of atmospheric CO₂ is in sharp contrast to most mid- and high-latitude continental shelves, which are CO₂ sinks. We argue that unlike the ECS and the North Sea where carbon on the shelf could be exported to the open ocean, the SYS lacks the physical conditions required by the CSP to transport carbon off the shelf effectively. The global validity of the CSP theory is thus questionable.     

Polycyclic aromatic hydrocarbons in marine sediments from the Rijeka Bay area, Northern Adriatic, Croatia, 1998-2006

The first analyses of PAHs in marine sediments within Rijeka Bay started in 1998 at three sampling sites offshore from the petroleum refinery facilities and were extended in 1999 to three more sampling points in front of the repair shipyard within the same east industrial zone. The small Svezanj cove, lying between the shipyard and the petroleum refinery was chosen as the reference point. The concentrations of PAHs were considerably higher in the shipyard environment (average: 3009-6314 μg kg⁻¹ d.w.) in comparison to the petroleum refinery area (average: 279-919 μg kg⁻¹ d.w.), while the PAHs load at reference point was close to the latter level (average: 717 μg kg⁻¹ d.w.). The Phe/Anth and Flo/Py ratios indicate the dominant pyrogenic sources, except for the results from 1999 to 2000 with dominant petrogenic origin at some sites. A declining trend of total PAHs, and consequently toxicity indices was observed at all sites.     

Plankton community as an indicator of water quality in tropical shrimp culture ponds

The plankton was examined as an indicator of water quality in 14 shrimp Litopenaeus vannamei farms in Brazil in 2003. The ponds were categorized by high stocking density (>30 PL m⁻²) of phytoplankton, consisting of 51 species with concentrations ranging from 365,218 ± 416,615 cells mL⁻¹ to 1,961,675 ± 3,160,172 cells mL⁻¹. Diatoms contributed to almost 70% of the species number and high densities resulted from Cyanophyta blooms, mainly Pseudanabaena cf limnetica. Forty zooplankton taxa were registered and were essentially composed of typical marine euryhaline species and suspension-feeders. Copepoda dominated (45%) the make-up, followed by Protozoa (18%), Rotifera (12%), and Mollusca (12%) larvae. Zooplankton varied from 972 ± 209 ind m⁻³ to 4235 ± 2877 ind m⁻³. Enhanced nutrient input affected plankton density and composition. Diatom and Copepoda dominance was replaced by cyanobacteria, protozoan, and rotifers as nutrient concentrations increased with the cultured period, indicating that plankton structure is affected by eutrophic conditions.