Correlation Characteristics of Electrical Conductivity of Surface Waters with the Fluorescence Excitation-Emission Matrix Spectroscopy-Parallel Factor Components of Dissolved Organic Matter

Impacts on the quality of surface water in a urban perimeter of the Rio Grande watershed, Brazilian Cerrado

The aim of this study was to assess the spatiotemporal variation in water quality in the Grande River and the Ondas River, in the city of Barreiras, Bahia, Brazil. Water samples were collected at 11 points along the rivers, and eight physical-chemical parameters (electrical conductivity, pH, alkalinity, apparent and true color, turbidity, dissolved oxygen, and biochemical oxygen demand) and three microbiological indicators (heterotrophic bacteria, total and thermotolerant coliforms) were analyzed. Spatiotemporal variation was assessed using the multivariate techniques of principal component analysis/factorial analysis (PCA/FA) and hierarchical cluster analysis (HCA). The results of the PCA/FA highlighted eight of the eleven parameters as the main ones responsible for the variations in water quality, with the greatest increase in these parameters being observed in the rainy season, especially among the points influenced by sewage discharges and by the influence of the urban area. The CA grouped the results from 11 points into three main groups: group 1 corresponded to points influenced by sewage discharges; group 2 grouped points with mainly urban influences; and group 3 grouped points in rural areas. These groupings showed the negative influence of urbanization and also statistically significant variations between the groups and periods. The most degraded conditions were in group 1, and the least degraded conditions were in group 3. Assessment of the variations between the monitoring periods showed that rainfall had a significant impact on the increase or decrease in the parameters assessed, as a result of surface runoff linked to urbanization and increased river flow.

Fish parasites as proxy bioindicators of degraded water quality of River Saraswati, India

The nature and intensity of water pollution determine the effects on aquatic biota and aquatic ecosystem health. The present study aimed at assessing the impact of the degraded physicochemical regime of river Saraswati, a polluted river having a historical legacy, on the parasitic infection and the role of fish parasite as a bioindicator of water quality. Two Water Quality Indices (WQIs) were adopted as useful tools for assessing the overall water quality status of polluted river based on 10 physicochemical parameters. Total 394 fish (Channa punctata) were examined. Ectoparasite Trichodina sp., Gyrodactylus sp., and endoparasites Eustrongylides sp. were collected from the host fish. Prevalence, mean intensity and abundance for each sampling period were calculated for the determination of parasitic load. The parasitic load of Trichodina sp. and Gyrodactylus sp. was significantly (p < 0.001) higher in winter, whereas the parasitic load of Eustrongylides sp. showed no significant (p > 0.05) seasonal fluctuation. The parasitic load of ectoparasites was negatively correlated with temperature, free carbon dioxide, biochemical oxygen demand, and WAWQI but positively correlated with electrical conductivity and CCMEWQI. Fish health was found to be adversely affected by degrading water qualities and parasitic infection. A 'vicious cycle' develops as a result of the interplay among deteriorating water quality, withering fish immunological defence, and amplifying parasitic infection. Since parasitic load was strongly conditioned by the combined influence of a suite of water quality parameters the fish parasites can be used as a powerful indicator of deteriorating water quality.

Assessing inputs of aquaculture-derived nutrients to streams using dissolved organic matter fluorescence

Salmon aquaculture is an important economic activity globally where local freshwater supplies permit land-based salmon aquaculture facilities to cultivate early life stage salmon. Nitrogen, phosphorus and organic matter in aquaculture effluents contribute to the eutrophication of adjacent and downstream rivers and lakes. This study quantifies the enrichment of nutrients in land-based salmon aquaculture facility effluents compared to receiving waters. We measured nutrient concentrations and dissolved organic matter (DOM) quantity and quality via fluorescence spectroscopy in streams and effluent waters associated with 27 facilities in Chile. We found that facilities added on average 0.9 (s.d. = 2.0) mg-C L^-1, 542 (s.d. = 637) μg-total N L^-1, and 104 (s.d. = 104) μg-total P L^-1 to effluents compared to stream waters. DOM in stream water was enriched in humic-like fluorescence, while aquaculture effluents were enriched in protein-like DOM fluorophores. Principal component and correlation analysis revealed that tryptophan-like fluorescence was a good predictor of total N and P in effluents, but the strength of significant linear relationships varied among individual facilities (r²: 0.2 to 0.9). Agreement between laboratory fluorescence and a portable fluorometer indicates the utility of in-situ sensors for monitoring of both tryptophan-like fluorescence and covarying nutrients in effluents. Thus, continuous in-situ sensors are likely to improve industry management and allow more robust estimates of aquaculture-derived nutrients delivered to receiving waters.

Novel insights into impacts of the COVID-19 pandemic on aquatic environment of Beijing-Hangzhou Grand Canal in southern Jiangsu region

In 2020, a sudden COVID-19 pandemic unprecedentedly weakened anthropogenic activities and as results minified the pollution discharge to aquatic environment. In this study, the impacts of the COVID-19 pandemic on aquatic environment of the southern Jiangsu (SJ) segment of Beijing-Hangzhou Grand Canal (SJ-BHGC) were explored. Fluorescent component similarity and high-performance size exclusion chromatography analyses indicated that the textile printing and dyeing wastewater might be one of the main pollution sources in SJ-BHGC. The water quality parameters and intensities of fluorescent components (WT-C1(20) and WT-C2(20)) decreased to low level due to the collective shutdown of all industries in SJ region during the Spring Festival holiday and the outbreak of the domestic COVID-19 pandemic in China (January 24th to late February, 2020). Then, they presented a gradual upward trend after the domestic epidemic was under control. In mid-March, the outbreak of the international COVID-19 pandemic hit the garment export trade of China and consequently inhibited the production activities of textile printing and dyeing industry (TPDI) in SJ region. After peaking on March 26th, the intensities of WT-C1(20) and WT-C2(20) decreased again with changed intensity ratio until April 12th. During the study period (135 days), correlation analysis revealed that WT-C1 and WT-C2 possessed homology and their fluorescence intensities were highly positively correlated with conductivity and COD_Mn. With fluorescence fingerprint (FF) technique, this study not only excavated the characteristics and pollution causes of water body in SJ-BHGC, but also provided novel insights into impacts of the COVID-19 pandemic on production activities of TPDI and aquatic environment of SJ-BHGC. The results of this study indicated that FF technique was an effective tool for precise supervision of water environment.

Advances in the characterization and monitoring of natural organic matter using spectroscopic approaches

Natural organic matter (NOM) is ubiquitous in environment and plays a fundamental role in the geochemical cycling of elements. It is involved in a wide range of environmental processes and can significantly affect the environmental fates of exogenous contaminants. Understanding the properties and environmental behaviors of NOM is critical to advance water treatment technologies and environmental remediation strategies. NOM is composed of characteristic light-absorbing/emitting functional groups, which are the "identification card" of NOM and susceptive to ambient physiochemical changes. These groups and their variations can be captured through optical sensing. Therefore, spectroscopic techniques are elegant tools to track the sources, features, and environmental behaviors of NOM. In this work, the most recent advances in molecular spectroscopic techniques, including UV-Vis, fluorescence, infrared, and Raman spectroscopy, for the characterization, measurement, and monitoring of NOM are reviewed, and the state-of-the-art innovations are highlighted. Furthermore, the limitations of current spectroscopic approaches for the exploration of NOM-related environmental processesand how these weaknesses/drawbacks can be addressed are explored. Finally, suggestions and directions are proposed to advance the development of spectroscopic methods in analyzing and elucidating the properties and behaviors of NOM in natural and engineered environments.