A novel fate and transport model for evaluating the presence and environmental risk of per-/poly-fluoroalkyl substances (PFASs) among multi-media in Lingang hybrid constructed wetland, Tianjin, China.

Accurately revealing and predicting the presence and risks of per-/poly-fluoroalkyl substances (PFASs) in constructed wetlands (CWs) is great significant for the construction and management of CWs, but very challenging. In this work, a novel fate and transport model was for the first time established to evaluate the spatially continuous distribution and environmental risks of PFASs among multi-media in Lingang hybrid CW fed by industry tailwater. 20 PFASs were detected from the Lingang CW, and the total concentration of the detected PFASs in water and sediments were in the range of 38.94-81.65 ng/L and 1.23-4.31 ng/g, respectively. PFOA, PFOS and PFBS were the main pollutants in water and sediments. A fate and transport model describing the distribution characteristics and fate of PFASs in Lingang hybrid CW was constructed, and its reliability was verified. The simulated results suggested that PFASs were mainly accumulated in sediments and long-chain PFASs were more easily adsorbed by sediments compared with short-chain PFASs. According to the principal component analysis-multiple linear regression (PCA-MLR), PFASs mainly came from the tailwater from the surrounding sewage treatment plants. Besides, the environmental risks were predicted by this novel model, suggesting that the risks still cannot be neglected due to the accumulation and continuous input of PFASs although the environmental risks of Lingang CW were low. This work provides a novel model for the understanding of presence and risks of PFASs among multi-media in CWs.

Presence of polycyclic aromatic hydrocarbons among multi-media in a typical constructed wetland located in the coastal industrial zone, Tianjin, China: Occurrence characteristics, source apportionment and model simulation.

In-depth understanding and accurately predicting the occurrence and fate of polycyclic aromatic hydrocarbons (PAHs) in constructed wetlands (CWs) is extremely crucial for optimizing the CWs construction and strengthening the risk control. However, few studies have focused on the PAHs among sediment-water-plant and model simulation in CWs. In this study, sediment, surface water and reed samples were gathered and analyzed from a typical CW. The concentrations of 16 PAHs (Σ16PAHs) in sediments, surface water and reeds ranged from 620 to 4277 µg/kg, 114 to 443 ng/L and 74.5 to 362 µg/kg, respectively. The coefficients of variation (CV) were calculated as 0.796, 0.431 and 0.473 for the above three media respectively, indicating that the spatial distribution variation was medium intensity. The fugacity fraction (ff) suggested that sediments might act as the secondary release source of most PAHs. According to the diagnostic ratios and principal component analysis-multiple linear regression (PCA-MLR), PAHs in this CW mainly come from fossil fuels combustion and petroleum leakage. PAHs in sediments showed high ecological risk at water inlet and moderate risk at the other functional zones, while low risks for surface water at all functional zones. Although the human health risk assessment indicated relatively low cancer risk, the health risk still cannot be ignored with the continuous input and accumulation of exogenous PAHs. A mathematical model covering the hydraulics parameters and composition characteristics of the wetland was established, and its reliability was verified. The simulated results obtained by the established model were basically consistent with the measured values. In addition, the total remove efficiency of PAHs in surface water was 40.2%, which calculated by the simulated model. This work provides helpful insight into the comprehension of occurrence and fate of PAHs among multi-media in CWs.

Trend correlations for coastal eutrophication and its main local and whole-sea drivers - Application to the Baltic Sea.

Coastal eutrophication is a major environmental issue worldwide. In the Baltic Sea, eutrophication affects both the coastal waters and the open sea. Various policy frameworks aim to hinder its progress but eutrophication-relevant water quality variables, such as chlorophyll-a concentrations, still exhibit opposite temporal trends in various Baltic Sea marine and coastal waters. In this study, we investigate the temporal-trend linkages of measured water quality variables and their various anthropogenic, climatic and hydrospheric drivers over the period 1990-2020 with focus on the Swedish coastal waters and related marine basins in the Baltic Sea. We find that it is necessary to distinguish more and less isolated coastal waters, based on their water exchanges with the open sea, to capture different coastal eutrophication dynamics. In less isolated coastal waters, eutrophication is primarily related to nitrogen concentrations, while it is more related to phosphorus concentrations in more isolated coastal waters. In the open sea, trends in eutrophication conditions correlate best with trends in climatic and hydrospheric drivers, like wind speed and water salinity, respectively. In the coastal waters, driver signals are more mixed, with considerable influences from anthropogenic land-based nutrient loads and sea-ice cover duration. Summer chlorophyll-a concentration in the open sea stands out as a main change driver of summer chlorophyll-a concentration in less isolated coastal waters. Overall, coastal waters are a melting pot of driver influences over various scales, from local land-based drivers to large-scale total catchment and open sea conditions. The latter in turn depend on long-term integration of pathway-dependent influences from the various coastal parts of the Baltic Sea and their land-based nutrient load drivers, combined with overarching climate conditions and internal feedback loops. As such, our results challenge any unidirectional local source-to-sea paradigm and emphasize a need for concerted local land-catchment and whole-sea measures for robust coastal eutrophication management.

An integrated migration and transformation model to evaluate the occurrence characteristics and environmental risks of Nitrogen and phosphorus in constructed wetland.

In this study, an integrated migration and transformation (IMT) model based on microbial action, plant absorption, sediment release and substrate adsorption was firstly established to evaluate the temporal-spatial distribution of N and P in Lingang hybrid constructed wetland (CW), Tianjin. Compared to the conventional transformation model that only considers the microbial action, the IMT model could accurately predict the occurrence characteristics of N and P. In Lingang CW, NO3--N (0.56-3.63 mg/L) was the most important form of N, and the TP was at a relatively low concentration level (0.04-0.07 mg/L). The spatial distribution results showed that a certain amount of N and P could be removed by CW. Form the temporal perspective, the N and P concentrations were greatly affected by the dissolved oxygen (DO). The simulated values obtained by IMT model indicated that the distribution of N and P was more affected by the temporality compared with the spatiality, which was consistent with measured values. Besides, the PCA indicated that TN, NO3--N and DO were important factors, which affected the water quality of CW. The Nemerow pollution index method based on the simulated values indicated that Lingang CW was overall moderately polluted, and the subsurface area was the main functional unit of pollutants removal in CW. This work provides a new model for accurately predicting the occurrence characteristics of N and P pollutants in CW, which is of great significance for identifying its environmental risks and optimizing the construction of wetlands.

Nutrient fluxes across sediment-water interface in Bohai Bay Coastal Zone, China.

Sediment cores and overlying water samples were collected at four sites in Tianjin Coastal Zone, Bohai Bay, to investigate nutrient (N, P and Si) exchanges across the sediment-water interface. The exchange fluxes of each nutrient species were estimated based on the porewater profiles and laboratory incubation experiments. The results showed significant differences between the two methods, which implied that molecular diffusion alone was not the dominant process controlling nutrient exchanges at these sites. The impacts of redox conditions and bioturbation on the nutrient fluxes were confirmed by the laboratory incubation experiments. The results from this study showed that the nutrient fluxes measured directly from the incubation experiment were more reliable than that predicted from the porewater profiles. The possible impacts causing variations in the nutrient fluxes include sewage discharge and land reclamation.

Metal contamination in sediments of the western Bohai Bay and adjacent estuaries, China.

Twelve sediment cores were collected in July 2007 in open waters of western Bohai Bay, the Port of Tianjin, and the adjacent estuaries of the Haihe and Yongding Rivers. While overall concentrations of trace metals at incremental depths in these cores met the Marine Sediment Quality (GB18668-2002) criteria of China, the magnitude of both metal enrichment factors (EF) and geoaccumulation indices (I(geo)) suggested that pollution with Ag, Cd, Cr, Cu and Zn was occurring in the estuaries and Port. Risk analysis also suggested that Ag and Ni concentrations were sufficiently elevated as to cause adverse biological effects in the study area. Although metal concentrations in western Bohai Bay were of less concern, a positive relationship between EF values and excess (210)Pb activity for several metals suggested that their concentrations were increasing over time.