Medicating the coast in a metropolitan city: Enantiomeric profiles and joint probabilistic risk assessment of antidepressants and antihistamines.

Pharmaceuticals are receiving increasing attention as emerging contaminants in the aquatic environment. Herein, we investigated the occurrence of 11 antidepressants, 6 antihistamines and 4 metabolites in treated wastewater effluents, rivers, stormwater, and seawater in Hong Kong, with special focus on chirality. The average levels of ∑pharmaceuticals ranged from 0.525 to 1070 ng/L in all samples and the total annual mass load of target pharmaceuticals in the marine environment of Hong Kong was 756 kg/y. Antihistamines accounted for >80 % of ∑pharmaceuticals, with diphenhydramine and fexofenadine being predominant. The occurrence and enantiomeric profiles of brompheniramine and promethazine sulfoxide were reported in global natural waters for the first time. Among chiral pharmaceuticals, mirtazapine and fexofenadine exhibited R-preference, while others mostly exhibited S-preference, implying that the ecological risks derived from achiral data for chiral pharmaceuticals may be biased. The joint probabilistic risk assessment of fluoxetine revealed that R-fluoxetine and rac-fluoxetine presented different ecological risks from that of S-fluoxetine; Such assessment also revealed that target pharmaceuticals posed only minimal to low risks, except that diphenhydramine posed an intermediate risk. As estimated, 10 % aquatic species will be affected when the environmental level of diphenhydramine exceeds 7.40 ng/L, which was seen in 46.9 % samples. Collectively, this study highlights further investigations on the enantioselectivity of chiral pharmaceuticals, particularly on environmental behavior and ecotoxicity using local aquatic species as target organisms.

Phytoplankton Community Integrity Index (PCII) - A potential supplementary tool for evaluating nutrient enrichment status of Hong Kong marine waters.

Diagnosis of eutrophication requires evidence of disturbance to the balance of organisms. We describe a tool, the Plankton Community Integrity Index (PCII), derived from the Plankton Index (PI) for tracking change in the seasonal patterns of abundance of diatom and dinoflagellate lifeforms when plotted in state space. The tool uses a nutrient-minimum reference period to interpret PCII values as status indicators, with values close to 1 indicating "High" status and 0.6 a Biological Water Quality Criterion (BioWQC) target set at the "Fair"/"Good" status boundary. It has been applied to Hong Kong marine waters, using data from monthly samples from 1995 through 2021. A preliminary analysis, required for the PI method, confirmed monsoonal seasonality in the diatom lifeform. In 5 of the 9 water bodies examined, PCII time series correlated with those of Total Inorganic Nitrogen (TIN). Since 2020, all Water Control Zones met the operationally defined BioWQC target.

Distinct interaction effects of warming and anthropogenic input on diatoms and dinoflagellates in an urbanized estuarine ecosystem.

Diatoms and dinoflagellates are two major bloom-forming phytoplankton groups in coastal ecosystems and their dominances will notably affect the marine ecosystems. By analyzing an 18-year monthly monitoring dataset (2000-2017) in the Pearl River Estuary (one of the most highly urbanized and populated estuarine in the world), we observe an increasing trend of the diatom to dinoflagellate ratio (Diatom/Dino). As revealed by multiple statistical models (generalized additive mixed model, random forest, and gradient boosting algorithms), both groups are positively correlated with temperature. Diatoms are positively correlated with nitrate and negatively correlated with ammonium while dinoflagellates show an opposite pattern. The Diatom/Dino trend is explained by an altered nutrient composition caused by a decadal increase in anthropogenic input, at which nitrate increased rapidly while ammonium and phosphate were relatively constant. Regarding the interaction of warming and nutrient dynamics, we observe an additive effect of warming and nitrate enrichment that promotes the increase in diatom cell density, while the dinoflagellate cell density only increases with warming when nutrients are depleted. Our models predict that the Diatom/Dino ratio will further increase with increasing anthropogenic input and global warming in subtropical estuarine ecosystems with nitrate as the dominant inorganic nitrogen; its ecological consequences are worthy of further investigation.

Evaluation of real-time PCR for quantitative detection of Escherichia coli in beach water.

The current investigation evaluated the use of real-time polymerase chain reaction (PCR) for quantitative detection of Escherichia coli in marine beach water. Densities of E. coli in 263 beach water samples collected from 13 bathing beaches in Hong Kong between November 2008 and December 2009 were determined using both real-time PCR and culture-based methods. Regression analysis showed that these two methods had a significant positive linear relationship with a correlation coefficient (r) of 0.64. Serial dilution of spiked samples indicated that the real-time PCR had a limit of quantification of 25 E. coli colonies in 100 mL water sample. This study showed that the rapid real-time PCR has potential to complement the traditional culture method of assessing fecal pollution in marine beach water.