Determining the fraction of pharmaceutical residues in wastewater originating from a hospital

Pharmaceutical residues in water are frequently analysed and discussed in connection with sewage treatment, ecotoxicity and, natural and drinking water quality. Among different localities hospitals are suspected, or implied, to be a major and highly variable source of pharmaceuticals that substantially contribute to the total wastewater load. In this study, the contribution of pharmaceuticals from a hospital to a sewage treatment plant (STP) serving around 45,000 inhabitants was evaluated. Approximately 200 hospital beds result in a hospital bed density of 4.4 beds per 1000 inhabitants, which is a typical value for developed world countries. Prior to sampling, a sound systems analysis was performed, and a sophisticated continuous flow-proportional sampling regime was applied. Hence, overall experimental uncertainty was reduced to a minimum, and measurements provide clear evidence that, for 28 of 59 investigated substances, over 85% of the pharmaceutical residue loads do not originate from the hospital when applying a conservative error estimation. Only for 2 substances, trimethoprim (18%) and roxithromycin (56%), was the maximum observed contribution of the hospital >15%. On average, the contribution of the hospital for the compounds detected in both, hospital effluent and sewage treatment plant influent was small and fairly constant. Five compounds were only detected in hospital wastewater, and 24 neither in the hospital wastewater nor in the total wastewater at the influent of the STP. For these compounds no experimental contribution could be calculated. For the compounds where audit data for both the national consumption and the specific hospital under investigation were available, a prediction of the fraction of pharmaceuticals originating from the hospital was performed. Three quarters of the compounds, classified with the existing audit data, were in the same “hospital contribution category” as determined by measurements. For most of the other compounds, plausible reasons could be identified to explain the observed deviations.     

Geochemical characteristics and fluxes of organic carbon in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), China

This study aims to investigate the state of the riverine organic carbon in the Luodingjiang River under human impacts, such as reforestation, construction of reservoirs and in-stream damming. Seasonal and spatial characteristics of total suspended sediment (TSS), dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as C/N ratios and the stable carbon isotopic signatures of POC (δ¹³C_POC) were examined based on a one-year study (2005) in the basin-wide scale. More frequent sampling was conducted in the outlet of the river basin at Guanliang hydrological station. DOC and POC concentrations showed flush effects with increasing water discharge and sediment load in the basin-wide scale. Atomic C/N ratio of POC had a positive relationship with TSS in the outlet of the basin, indicating the reduced aquatic sources and enhanced terrestrial sources during the high flood season. However, the similar relationship was not observed in the basin-wide scale mainly due to the spatial distributions of soil organic carbon and TSS. δ¹³C_POC showed obvious seasonal variations with enriched values in the period with high TSS concentration, reflecting the increased contribution from C₄ plants with enhanced soil erosion.The specific flux of the total organic carbon (2.30 t km^− 2 year^− 1) was smaller than the global average level. The ratio of DOC to POC was 1.17, which is higher than most rivers under Asian monsoon climate regime. The organic carbon flux was estimated to decline with decreasing sediment load as a result of reforestation, reservoir construction and in-stream damming, which demonstrates the impacts of human disturbances on the global carbon cycle.     

Exchange of oxygen and carbon dioxide across the water surface during algal blooms in a pond

Exchange of O₂ and CO₂ across the water surface during algal blooms was studied in an experimental pond from measurements of O₂ and TCO₂, pH and chlorophyll-a. Production and consumption rates of O₂ due to biological activity were also measured using light and dark bottles.Algal blooms occurred twice during the experimental period of 22 days. The trajectory on the phase plane showing the time changes in concentration of O₂ and TCO₂ made a clockwise, converging loop. A new concept and quantity called total oxygen (TO₂), which is the sum of the concentrations of O₂ and TCO₂, is proposed in order to distinguish the role of gas exchange from that of deposits. From the analysis of the trajectory, the total amount of TO₂ was found to decrease during the production period, and increase during the decomposition period. This was due to the difference between O₂ and TCO₂. The mass transfer coefficient of O₂ was found to be (3.6 ± 1.9) × 10⁻⁴, and that of TCO₂ (1.0 ± 0.5) × 10⁻⁴ cm s⁻¹.During the production period, 60% of produced O₂ was lost to the atmosphere, and 20% of consumed TCO₂ was supplied from the atmosphere. During the decomposition period, 80% of consumed O₂ was supplied, and 35% of produced TCO₂ was lost.     

Major ion chemistry and dissolved inorganic carbon cycling in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), China

Major ion chemistry and dissolved inorganic carbon system (DIC, mainly HCO₃⁻ and gaseous CO₂) in the Luodingjiang River, a mountainous tributary of the Zhujiang (Pearl River), China, were examined based on a seasonal and spatial sampling scheme in 2005. The diverse distribution of lithology and anthropogenic impacts in the river basin provided the basic idea to assess the effects of lithology vs. human activities on water chemistry and carbon biogeochemistry in river systems. Major ions showed great spatial variations, with higher concentrations of total dissolved solids (TDS) and DIC in the regions with carbonate rocks and clastic sedimentary rocks, while lower in the regions with metamorphic sandstones and schists as well as granites. pCO₂ at all sampling sites was oversaturated in June, ranging with a factor from 1.6 to 18.8 of the atmospheric concentration, reflecting the enhanced contribution from baseflow and interflow influx as well as in situ oxidation of organic matter. However, in April and December, undersaturated pCO₂ was found in some shallow, clean rivers in the upstream regions. δ¹³C of DIC has a narrow range from − 9.07 to − 13.59‰, which was more depleted in the regions with metamorphic rocks and granites than in the carbonate regions. Seasonally, it was slightly more depleted in the dry season (December) than in the wet season (June). The results suggested that lithological variability had a dominant control on spatial variations of water chemistry and carbon geochemistry in river systems. Besides, anthropogenic activities, such as agricultural and urban activities and in-stream damming, as well as river physical properties, such as water depth and transparency, also indicated their impacts. The seasonal variations likely reflected the changes of hydrological regime, as well as metabolic processes in the river.