In 1990–91 three deepwater ocean outfalls replaced three cliff-face outfalls discharging approximately 940 ML/day, or 80% of sewage generated by the City of Sydney (Australia) (population 3.3 million). Operation of these outfalls was assessed for the first two years and performed well, mitigating most of the environmental problems previously experienced from shoreline discharge. However, a concern remained for the unknown long-term effects on the marine environment. The current series of articles examine over 20 years of monitoring, for possible accumulative effects. Oceanographic modelling provided an understanding of particle settling, dispersion and distribution of discharged wastewater and monitoring assessed potential impact of offshore discharges on beach bathing water quality, sediment chemistry and benthic infauna. These four articles demonstrate that properly designed ocean outfalls are a viable, sustainable solution to sewage disposal for mega-coastal cities, however, continued monitoring is required to assess possible long-term environmental degradation.

The chemical industrial zone located along the Xiaoqing River wetlands adjacent to Bohai Sea is one of the largest production bases for brominated flame retardants in China. Herein, high levels of bisphenol-A, tetrabromobisphenol-A (TBBPA), tribromobisphenol-A, dibromobisphenol-A, and monobromobisphenol-A were detected in sediment, soil, and water samples of this zone in the range of below method detection limit (<MDL)–5.45 × 10⁶ ng/kg dw, <MDL–8.37 × 10⁴ ng/kg dw, and <MDL–5.59 × 10² ng/L, respectively. They were mainly buried in sediments as their highest levels in sediment samples. The small concentration fluctuation between water samples retrieved in the upstream and downstream zones is likely attributed to seawater backflow. The nearby chemical factories were point pollution sources and the less brominated analogs are largely from debromination of TBBPA. High pollution levels and the ecological risks of these pollutants along the Xiaoqing estuary to Bohai Sea need to be further assessed in future studies.

Microplastics have emerged as new pollutants in oceans. Nevertheless, information of the long-term variations in the composition of plastic-associated microbial communities in coastal waters remains limited. This study applied high-throughput sequencing to investigate the successional stages of microbial communities attached to polypropylene and polyvinyl chloride microplastics exposed for one year in the coastal seawater of China. The composition of plastisphere microbial communities varied remarkably across geographical locations and exposure times. The dominant bacteria in the plastisphere were affiliated with the Alphaproteobacteria class, particularly Rhodobacteraceae, followed by the Gammaproteobacteria class. Scanning electron microscopy analysis revealed that the microplastics showed signs of degradation. Microbial communities showed adaptations to plastisphere including more diverse microbial community and greater “xenobiotics biodegradation and metabolism” in metabolic pathway analysis. The findings elucidate the long-term changes in the community composition of microorganisms that colonize microplastics and expand the understanding of plastisphere microbial communities present in the marine environment.

During the last years, the oil and gas explorations, extractions and refineries have led to severe ecological damages into the sensitive environment of the Persian Gulf. In this study, the level of oil contamination, the source of hydrocarbons and the degree of weathering or degradation extent were investigated in the Surface Sediments of Pars Special Zone, Persian Gulf. Fifteen sediment samples were collected. The Gas Chromatography-Mass Spectrometry used to analyze Aliphatic Hydrocarbons (AHC) and EPA's sixteen compounds of Polycyclic Aromatic Hydrocarbons (PAHs). The total concentration of Aliphatic Hydrocarbons found to be in the range of 693 to 3752 μg/g and the 16 EPA PAHs compounds varied between 46.6 and 84.7 ng/g dry weight in the region. The concentration of hydrocarbons found to be lower than the level of threshold effects. The source of compounds was also identified by developing the multiple indices.

This baseline study highlights the ²¹⁰Po and ²¹⁰Pb concentration in seven macroalgae species from the northern Gulf that are frequently washed ashore during the bloom season from February to April. The highest concentrations of ²¹⁰Po and ²¹⁰Pb were 2.947 ± 0.032 and 1.057 ± 0.145 Bq kg⁻¹ wwt, respectively, in brown algae Sargassum boveanum, and the lowest in green algae Ulva prolifera with 1.533 ± 0.058 and 0.170 ± 0.069 Bq kg⁻¹ wwt, respectively. A ²¹⁰Po enrichment was observed in both brown and green algae species, with the ²¹⁰Po/²¹⁰Pb ratio being >1 for all the samples. The mean concentration of ²¹⁰Po in all species was an order of magnitude higher than ²¹⁰Pb, and the difference in mean concentration is statistically significant (p < 0.001). At the same time, the mean concentration of dissolved ²¹⁰Po and ²¹⁰Pb in seawater was 0.28 ± 0.01 and 0.52 ± 0.01Bq m⁻³ with a ²¹⁰Po/²¹⁰Pb ratio of 0.54 ± 0.02 indicating that ²¹⁰Po was absorbed from water and more concentrated by macroalgae. The measured concentration factor (CF) for ²¹⁰Po in these macroalgae for the northern Gulf varied between 5 × 10³–1 × 10⁴, higher than the IAEA recommended value of 1 × 10³ which suggests that a revision of that value may be needed. The field derived CFs for ²¹⁰Pb vary between 3 × 10²–1.8 × 10³, comparable to the ICRP recommended value of 2 × 10³.

North Abu Ali Island is contaminated by crude oil from exogenous sources with a variety of persistent toxic substances (PTSs) being input into intertidal sediments. We detected an array of PTSs in sediments and benthic biota off north Abu Ali Island (Arabian Gulf), including 35 polycyclic aromatic hydrocarbons (PAHs), 6 alkylphenols (APEOs), 10 styrene oligomers (SOs), and tributyltin. The PTS concentrations were generally greater than those reported in other areas of Arabian Gulf. PAHs mainly originated from petrogenic sources, and APEOs and SOs seem to be of recent origin. Field-based biota-sediment accumulation factors (BSAF) varied by taxa and compounds, but clearly depended on the log Kₒw values of individual compounds. Some PTSs exceeded the established guidelines for sediments and biota; we found particularly great BSAFs for alkyl-naphthalenes (C1- and C2-), nonylphenol monoethoxylates, and 2,4,6-triphenyl-1-hexene. Remediation will require on-site clean-up of toxic chemicals together with immediate efforts on preventing input of current pollution sources in the given area.

In the present study, 13 endocrine disrupting compounds (EDCs) and their transformation products (TPs) were monitored in Jiulong River and its estuary, China in different seasons. The analytes included antimicrobials [triclosan (TCS) and triclocarbon (TCC)]; estrogens [estrone (E1), estradiol (E2), estriol (E3) and ethinylestradiol (EE2)]; alkylphenol ethoxylates [4-n-nonylphenol (NP) and 4-n-octylphenol (OP)] and the TPs [methyl triclosan (MeTCS), carbanilide (NCC), dichlorocarbanilide, 4-hydroxy estrone (4-OH E1) and 4-hydroxy estradiol (4-OH E2)]. A significant seasonal variation was observed for most EDCs. Approximately, 79% of the total E2 residues were detected in the normal season in comparison with the wet season to indicate recalcitrant behavior of E2 during the normal season. Risk assessment revealed that E2 was most potent among the EDCs to cause highest risk to both vertebrate and invertebrate aquatic species, whereas, E1, EE2, MeTCS and TCS also showed relatively high risk for some surface water aquatic species.

In this study, the spatial distribution and forms of nitrogen in sediment cores collected from the Pearl River Estuary were analyzed. Exchangeable nitrogen (Nₑₓ) comprised only a small proportion of total nitrogen (Nₜₒₜ), with a mean of 3.54% in the sediment cores. NH₄⁺ was the main form of Nₑₓ. No obvious change was observed in the vertical content of fixed ammonia (Nfᵢₓ) in the sediments, and the mean Nfᵢₓ in all five sediment cores was 141.23 mg·kg⁻¹. The organic nitrogen (Nₒᵣg), strongly related to organic carbon (Cₒᵣg), was the main form in Nₜₒₜ. The dissolved inorganic nitrogen in sediment pore water was much lower than that in estuarine water and no significant variation was observed from upstream to downstream. Our results indicated that most nitrogen deposited on surface sediments from overlying water was rapidly removed by a series of microbial processes, reducing the extent of nitrogen returning to overlying waters.

Floating marine litter is known to be currently a widespread pollution problem, especially in the Mediterranean basin, but records on the levels of floating debris in the eastern part are less known. By using an observation platform (32 days, 137 transects, 1784 km), this study provides evidence of a high amount of floating debris in the Levantine sub-basin, within the eastern Mediterranean Sea. The density of floating litter varied between 18 and 1593 items km⁻² (average 232 ± 325 items km⁻²), and small plastic debris accounted for >90% of the items surveyed. These values tend to be higher than densities reported for the central and western Mediterranean areas, which may be related to the circulation patterns and inputs from coastal sources. Significant correlations of floating macro litter density with wind force and sea state were found, thus strengthening the need to standardise protocols (including oceanographic variables) of visual surveys of floating debris.