Occurrence, distribution, and ecological risks of organic pollutants in global mangrove sediments.

Composting (aerobic treatment of organic wastes) and digestion (anaerobic treatment of organic wastes combined with biogas production) are important waste management strategies with increasing significance in the European Union and Switzerland. Most of the compost produced is applied to agricultural soils, which hereby recycles nutrients and influences soil properties beneficially. However, compost can contain pollutants that may be hazardous for the soil ecosystem. The problem related to heavy metals had been recognised and measures for reduction were taken. Regarding organic pollutants, the current knowledge is insufficient for quality control and risk assessment. This thesis provides a comprehensive overview on organic contaminates in compost, digestate, and presswater and describes factors that may influence them. In the beginning an extensive literature review was carried out to summarize the current data. Compound classes to be analysed in Swiss composts and digestates were prioritized and analytical methods established. Polychlorinated biphenyl concentrations (∑ of PCB 28, 52, 101, 118, 138, 153, 180) were significantly higher in urban (median: 30 μg/kgdry weight (dw), n=52) than in rural samples (median: 14 μg/kgdw, n=16), which points – together with low concentrations in general – to aerial deposition on feedstock material as major input pathway to compost. Median polycyclic aromatic hydrocarbon (PAH) concentration was 3010 μg/kgdw (∑ of 16 PAH defined by the US EPA except dibenzo[a,h]anthracene, n=69). PAH levels were influenced by the organic matter degradation process (higher levels in digestate than in compost), the season of input material collection (spring/summer>winter>autumn), the particle size (higher concentrations in unsieved or sieved >20mm than in sieved to ≤ 20mm products), and maturity (lower concentrations in more mature composts). One fourth of the samples exhibited PAH concentrations above the Swiss guide value for compost (Ordinance on the Reductions of Risks linked to Chemical Products). These elevated concentrations can lead to considerable input of PAH to soil by compost application. To assess the major contributors of PAH in compost, characteristic PAH ratios and some molecular markers were considered, which pointed mainly to combustion origin of these contaminants. Multifactor statistical analysis indicated traffic emission, straw combustion and some asphalt abrasion as potential additional sources. Concentrations of other organic pollutants determined (dibenzo-p-dioxins and -furans, dioxin-like PCB, brominated flame retardants (BFR), perfluorinated alkyl substances (PFAS), di(2-ethylhexyl)phthalate, nonylphenol and chlorinated paraffins) were mostly above levels found in background soil, except for nonylphenol, which was not detected. Out of 269 pesticides analysed, 30 fungicides, 14 herbicides, eight insecticides and one acaricide were detected. For the first time, the fate of organic pollutants during full-scale composting and digestion was assessed. Concentrations of low chlorinated PCB increased during composting (about 30 %), whereas a slight decrease was observed for the higher chlorinated congeners (about 10%). Enantiomeric ratios of atropisomeric PCB were close to racemic and did not change. Levels of low molecular weight PAH were reduced during composting (50 to 90% reduction), whereas heavier compounds remained stable. However, as indicated above, conventional composting does not reduce PAH concentrations sufficiently to comply with Swiss guide values (see above). Further research is needed to i) identify measures to reduce PAH concentrations in digestate and compost, ii) to monitor organic pollutants that are still increasing in other environmental matrices (e.g. BFR and PFAS) or identify new compounds which have not been detected in compost yet, iii) to evaluate potential risk of compost application to soil by assessing the bioavailable fractions of organic pollutants and iv) to examine possible new input materials and co-substrates for composting and digestion.

Occurrence, distribution and ecological risk of trace metals and organic pollutants in surface sediments from a Southeastern European river (Someşu Mic River, Romania)

Profiles and inventories of organic pollutants in sediments from the central Beibu Gulf and its coastal mangroves

The concentrations of total polycyclic aromatic hydrocarbons (PAHs) and 22 individual PAH compounds in 42 surface sediments collected from the mangrove forest of Qeshm Island and Khamir Port (Persian Gulf) were analyzed. PAHs concentrations ranged from 259 to 5,376 ng g(-1) dry weight with mean and median values of 1,585 and 1,146 ng g(-1), respectively. The mangrove sediments had higher percentages of lower molecular weight PAHs and the PAH profiles were dominated by naphthalene. Ratio values of specific PAH compounds were calculated to evaluate the possible source of PAH contamination. This ratios suggesting that the mangrove sediments have a petrogenic input of PAHs. Sediment quality guidelines were conducted to assess the toxicity of PAH compounds. The levels of total PAHs at all of stations except one station, namely Q6, were below the effects range low. Also, concentrations of naphthalene in some stations exceeded the effects range median.

Microplastics and associated organic pollutants in beach sediments from the Gulf of Guinea (SE Atlantic) coastal ecosystems

Chlorinated pesticides, polychlorinated biphenyls and polycyclic aromatic hydrocarbons in the fat tissue of seabirds from King George Island, Antarctica

Halogenated organic pollutants in sediments and organisms from mangrove wetlands of the Jiulong River Estuary, South China

Screening legacy and emerging organic pollutants in the contaminated soil of Dhaka, Bangladesh

Knowledge regarding partitioning behavior and bioaccumulation potential of environmental contaminants is important for ecological and human health risk assessment. While a range of models are available to describe bioaccumulation potential of hydrophobic organic chemicals (HOCs) in temperate aquatic food webs, their applicability to tropical systems still needs to be validated. The present study involved field investigations to assess the occurrence, partitioning, and bioaccumulation behavior of several legacy and emerging HOCs in mangrove ecosystems in Singapore. Concentrations of synthetic musk fragrance compounds, methyl triclosan (MTCS), polychlorinated biphenyls, organochlorine pesticides, and polycyclic aromatic hydrocarbons were measured in mangrove sediments, clams, and caged mussels. Freely dissolved concentrations of the HOCs in water were determined using silicone rubber passive samplers. Results showed that polycyclic musks and MTCS are present in mangrove ecosystems and can accumulate in the tissues of mollusks. The generated HOC concentration data for mangrove water, sediments, and biota samples was further utilized to evaluate water-sediment partitioning (e.g., Koc values) and bioaccumulation behavior (e.g., BAF and BSAF values). Overall, the empirical models fit reasonably well with the data obtained for this ecosystem, supporting the concept that general models are applicable to predict the behavior of legacy and emerging HOCs in mangrove ecosystems.

Distribution and sources of polynuclear aromatic hydrocarbons in Mangrove surficial sediments of Deep Bay, China

Sediment pollution of the biggest Danube tributary, the Sava River, was investigated within the sixth framework European Union project "Sava River Basin: Sustainable Use, Management and Protection of Resources" (SARIB). The extent of pollution was estimated by determining the amount of inorganic and persistent organic pollutants in sediment samples at 20 selected sampling sites along the Sava River. For the purpose of clarity, the findings are presented and published separately (part I: selected elements and part II: persistent organic pollutants). This study presents an investigation into the presence of organic pollutants in the Sava River sediment. According to the Water Framework Directive, the following persistent organic pollutants were investigated: polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), selected chlorinated pesticides and organotin compounds. The results reveal that PAHs were present in moderate concentrations (sum of 16 PAHs: up to 4,000 ng g(-1)) and their concentrations increased downstream. Concentrations of PCB were low (sum of seven indicator PCBs: below 4 ng g(-1)) and among the pesticides analyzed only p,p-dichlorodiphenyltrichloroethane was found in moderate concentrations at two sampling sites in Croatia (up to 3 ng g(-1)) and hexachlorobenzene was found in a high concentration in the city of Belgrade (91 ng g(-1)), although the use of these persistent pesticides has been banned for decades. Repeated sampling at the same location revealed point pollution near Belgrade. Among the organic pollutants surveyed, organotin compounds were not detected. Overall results reveal the presence of persistent organic pollutants in 20 of the Sava River sediments tested that is, in general, comparable or lower than the levels in the Danube River and other moderately polluted European rivers.

Polycyclic aromatic hydrocarbons (PAHs) are of great environmental and human health concerns due to their widespread occurrence, persistence and carcinogenic properties. There is now compelling evidence that the mangrove sediment microbial structure is susceptible to PAHs contamination. The study aimed to assess the effects of PAHs on the nitrogen-fixing bacterial community of mangrove sediment. Three types of PAHs, naphthalene (NAP), a two-ring PAH; fluorene (FLU), a three-ring PAH; and pyrene (PYR), a four-ring PAH; were applied at three doses. After 7 and 24 days of incubation, the nitrogen-fixing bacterial population and diversity were evidenced in the nifH gene polymerase chain reaction denaturing gradient gel electrophoresis profile. DGGE pattern shows that the nitrogen-fixing bacterial community changed significantly with the types and doses of PAHs, and the incubation time. As far as single PAH is concerned, high concentration of PAH has larger impact on the nitrogen-fixing bacteria than low concentration of PAH. Besides, among the three types of PAHs, NAP has the greatest short term toxicity; PYR has the strongest long-term impact, whereas FLU has relatively higher long-time effect. Multidimensional scaling analysis and correspondence analysis are two reliable multivariate analysis methods for investigating the relationship between the nitrogen-fixing bacterial community and PAHs contamination. Investigating the effect of PAHs on the nitrogen-fixing bacterial diversity could yield useful information for understanding the process of biogeochemical cycling of nitrogen in mangrove sediment. The present study reveals that nitrogen-fixing bacterial community can be used as an important parameter indicating the impact of PAHs on mangrove sediment ecosystem.

Persistent organic pollutants in sediments of the Wouri Estuary Mangrove, Cameroon: Levels, patterns and ecotoxicological significance

PAHs contamination and bacterial communities in mangrove surface sediments of the Jiulong River Estuary, China

Spatial distribution, homologue patterns and ecological risks of chlorinated paraffins in mangrove sediments along the South China Coast