Microplastic contamination in edible clams from popular recreational clam-digging sites in Hong Kong and implications for human health.

The ubiquitous presence of microplastics in edible bivalves and the human health risks associated with bivalve consumption have raised public concerns. Farmed and market-sold bivalves have received the most attention, while wild bivalves have received much less scrutiny. In the present study, 249 individuals were examined across six wild clam species from two popular recreational clam-digging sites in Hong Kong. Of the clams, 56.6 % contained microplastics, with an average abundance of 1.04 items/g (wet weight) and 0.98 items/individual. This resulted in an estimated annual dietary exposure of 14,307 items per Hong Kong resident. Moreover, the potential microplastic risks for humans associated with wild clam consumption were assessed using the polymer hazard index, and the results indicated a medium degree of risk, indicating that exposure to microplastics through wild clam consumption is inevitable and poses a potential health threat to humans. Further research is needed to facilitate a better understanding of the widespread occurrence of microplastics in wild bivalves, and further refinements of the risk assessment framework can hopefully allow a more accurate and holistic health risk assessment for microplastics.

Microplastic contamination in marine-cultured fish from the Pearl River Estuary, South China.

Microplastics are ubiquitous in the aquatic environment. However, the occurrence of microplastics in farmed fish is under-researched. Herein, microplastic abundance in the stomach and intestine of marine-cultured hybrid groupers (Epinephelus fuscoguttatus × Epinephelus lanceolatus) in the Pearl River Estuary (PRE) was examined. Microplastics were detected in all fish samples, with an average abundance of 35.36 n/individual or 0.62 n/g. The fish intestine contained more microplastics (23.91 n/individual, i.e., 1.10 n/g) than the stomach (12.80 n/individual, i.e., 0.37 n/g). In addition, the ingested microplastics were predominantly fibre-shaped (70.1%), and nearly 70% were smaller than 1 mm in diameter. Potential factors affecting the ingestion of microplastics by farmed hybrid groupers include fish diet and the availability of microplastics in their feeding habitat.

The influences of emotional factors on householders' decarbonizing cooling behaviour in a subtropical Metropolitan City: An application of the extended theory of planned behaviour.

Air-conditioning accounts for a vast amount of electricity consumption in Hong Kong, and household decarbonization of cooling is considered a vital means of reducing electricity use. However, little information is available on the determinants of household decarbonizing cooling behaviour, and emotional factors are often ignored in the pro-environmental behaviour literature. Thus, this study attempts to address this gap by applying an emotional extension of the theory of planned behaviour (TPB). A total of 295 valid responses were obtained using a questionnaire survey and tested via structural equation modeling (SEM). The incorporation of additional variables improves the explanatory power of the household decarbonizing cooling behaviour model, and the results reveal that subjective norms is the most influential factor, followed by affective connection to nature and negative anticipated emotions. Meanwhile, attitude towards the behaviour and perceived behavioural control are found to have a nonsignificant effect on behavioural intention. These findings not only highlight the importance of emotions in predicting electricity-saving behaviour, but also provide useful insights to formulate effective approaches for motivating citizens to engage in decarbonizing cooling behaviour at home.

Spatial variation of floatable plastic debris and microplastics in the Pearl River Estuary, South China.

The estuaries of populated catchments have been documented as hotspots of plastic pollution. In this study, microplastics (0.355-5.0 mm) and large plastic debris (>5.0 mm) of surface water collected from the Inner Lingding Bay of the Pearl River Estuary (PRE) were quantified and categorized according to their size, shape, colour and composition. Both microplastics and large plastic debris were detected at all sampling sites with mean abundances of 2.376 ± 0.700 n/m3 and 0.110 ± 0.039 n/m3, respectively. Microplastics constitute 95.4% of the total abundance by number. The average microplastic concentration in the inner PRE was almost 3.5 times higher than that in the central PRE, indicating a positive correlation between plastic concentration and proximity to the river mouth. This result reveals the important role of rivers in transporting plastic debris from land to the oceans.

A meta-analysis of methodologies adopted by microplastic studies in China.

China is the world's largest plastic producer and has been a focus of research on microplastic pollution. An increasing number of studies have documented plastics in the sediment, water and biota of China over the past decades. This systematic review compares different methodologies adopted by microplastic studies in China, including sampling equipment and methods; laboratory procedures in microplastic extraction and identification; and the characterisation and quantification of particles. In general, sediment samples were primarily collected with a grab sampler, while water samples were mostly taken from the surface using trawl nets. Different techniques, including density separation, chemical digestion, sieving and filtration, were applied to extract microplastics from the sample matrix. Visual sorting was an obligatory step that identifies microplastics by their morphological characteristics, such as size, shape and colour. Most studies in China reported the prevalence of irregular-shaped particles with sizes smaller than 1 mm. The chemical properties of microplastics were also assessed using infrared and Raman spectroscopy. Quantitative units commonly used for sediment, water and biota samples were "items per kg", "items per m3" and "items per individual", respectively. The inconsistencies in methods have marked the urgent warrant of a standardised methodology. It is believed that the findings of the present review can serve as an important waypoint contributing towards a more efficient and long-acting methodology for microplastic research, that can enable meaningful inter-study comparisons.