Prevalence, distribution, accumulation, and risk of environmental corticosteroids and estrogens in biofilms from the Pearl River Delta.

Biofilms play a significant role in the biogeochemical processing of organic matter and the environmental fate of emerging pollutants. In this study, we investigated the occurrence and distribution of 32 endocrine-disrupting chemicals (EDCs), including 24 environmental corticosteroids (ECs) and 8 environmental estrogens (EEs), in natural biofilms from the Pearl River system. Their association between biofilms and water and environmental risk were assessed. The ECs and EEs ubiquitously occurred in the biofilms, ranging from <0.61-6.57 ng/g and <0.8-2535 ng/g, respectively. Temporally, there was no obvious variance in either ECs or EEs in the biofilms during the winter and summer, and their concentrations exhibited a spatial trend of upward to midstream, descending downstream, and then seaward attenuation at the estuary. For ECs and EEs, the similar levels of field-derived bioconcentration factors (BCFs) (logarithm values: 2.42-2.86 and 2.72-2.98, respectively) and biofilm organic carbon-normalized partitioning coefficients (Kboc) (3.39-3.69 and 3.35-3.95) suggest the comparable potential of accumulation and sorption by biofilms between these two classes of EDCs. In addition, higher values of BCF and Kboc for the EEs were found in winter and were correspondingly comparable to their distribution coefficients (Kd) and Koc derived from suspended particles and sediment, revealing that biofilms are a competitive environmental compartment for capturing EDCs, particularly during the mature period. A positive logKboc-logKow relationship suggests hydrophobic partitioning as a primary interaction mechanism between the biofilm and EEs. Moreover, high risks from biofilm-associated ECs and EEs might have posed to the fluvial ecosystem. This study provides original insights into the occurrence, fate, and risk of ECs in natural biofilms for the first time and demonstrates that biofilms may not only serve as reservoirs but also serve as sentinels for fluvial EDC contamination. These results contribute to the further understanding of the behavior and fate of EDCs in aquatic environments.

Rapid on-site detection of underground petroleum pipeline leaks and risk assessment using portable gas chromatography-mass spectrometry and solid phase microextraction.

Locating underground pipeline leaks can be challenging due to their hidden nature and variable terrain conditions. To sample soil gas, solid-phase microextraction (SPME) was employed, and a portable gas chromatography/mass spectrometry (GC/MS) was used to detect the presence and concentrations of petroleum hydrocarbon volatile organic compounds (pH-VOCs), including benzene, toluene, ethylbenzene, and xylene (BTEX). We optimized the extraction method through benchtop studies using SPME. The appropriate fibre materials and exposure time were selected for each BTEX compound. Before applying SPME, we preconditioned the soil vapour samples by keeping the temperature at around 4 °C and using ethanol as a desorbing agent and moisture filters to minimize the impact of moisture. To conduct this optimisation, airbags were applied to condition the soil vapour samples and SPME sampling. By conditioning the samples using this method, we were able to improve analytical efficiency and accuracy while minimizing environmental impacts, resulting in more reliable research data in the field. The study employed portable GC/MS data to assess the concentration distribution of BTEX in soil vapour samples obtained from 1.5 m below the ground surface at 10 subsurface vapour monitoring locations at the leak site. After optimization, the detection limits of BTEX were almost 100 µg/m3, and the measurement repeatabilities were approximately 5% and 15% for BTEX standards in the laboratory and soil vapour samples in the field, respectively. The soil vapour samples showed a hotspot region with high BTEX concentrations, reaching 30 mg/m3, indicating a diesel return pipeline leak caused by a gasket failure in a flange. The prompt detection of the leak source was critical in minimizing environmental impact and worker safety hazards.