Time-series sampling of trace metals in surface waters using osmotic sampler with air segmentation and preservative addition.

High-resolution time-series concentrations (CTS) are very important for the investigation of the biogeochemical processes of trace metals in the aquatic environment. However, the acquisition of CTS of trace metals in water is still challenging because of the lack of suitable samplers. In this study, an osmotic sampler coupled with air segment injection and preservative addition was employed for time-series sampling of trace metals in surface waters. In the sampler, water sampling and preservative adding are both driven by osmotic pumps (OPs), while air segment injection is accomplished by a timer-controlled micro diaphragm pump. During deployment, the sampling OP continuously draws water through a filter and stores it in a narrow-bore coil. Simultaneously, a preservative OP slowly pushes 30% HNO3 (v/v) into the collected sample for in situ preservation. Periodically, the micro diaphragm pump injects air into the continuous water stream to divide it into water segments, enabling accurate time-stamping. After retrieval, the time-series samples were pumped out from the coil and re-collected to analyze the CTS of analytes. The sampler was deployed in river, reservoir, and marine waters for 26 h and one week to measure CTS of trace metals at time resolutions of 2 h and 12 h. Results showed that the recoveries of a preloaded standard mixture (1.0 µg/L) in all samplers ranged from 93.1% to 117.8%. The measured CTS of Cd, Co, Cr, Cu, Mn, and Ni in the waters only varied in small ranges. Accordingly, the measured CTS data from the sampler were consistent with the obtained concentrations from grab sampling. The relative percent differences between the measurements from two samplers were less than 37.4%. These results demonstrate the reliability and accuracy of the sampler for time-series sampling of the chosen trace metals in surface waters.

Measuring of time-series concentrations of nutrients in surface waters using osmotic sampler with air bubble segmentation and preservative addition.

The analysis of time-series concentrations (CTS) is of great importance when investigating the biogeochemical processes of nutrients in aquatic environments. However, obtaining CTS of nutrients remains a challenge using current sampling techniques. In this study, a novel in situ sampler was constructed using reverse osmosis membrane (ROM) osmotic pumps (OP) (ROM-OP sampler), and was used to obtain the CTS of nutrients in surface waters. The sampler consisted of a sampling OP, sample storing coil, filter, bubble injection module, and preservative adding module. When deployed, the sampling OP continuously draws ambient water through the filter into the sample storing coil, while simultaneously the preservative adding module continuously delivers preservative (H2SO4 solution) into the water flow. The bubble injection module periodically injects air bubbles into the sample storing coil, to segment the sample and create time stamp indicators that allow the sample age to be defined. Upon retrieval, the sample segments in the coil are sequentially pumped out of the sample storing coil and transferred into different vials for further analysis. The sampler was applied to measure the CTS of various nutrients, including dissolved total nitrogen, dissolved total phosphorus, dissolved reactive phosphorus, and nitrate in a river over a 20 day period and in municipal sewage treatment plant effluent for a 36 h period. Results showed that the ROM-OP sampler successfully obtained CTS of nutrients, capturing nutrient variations at a high temporal resolution. This sampler is relatively low-cost (~USD 300), small in size, lightweight, robust and does not require an external power source, showing high promise as an effective and efficient tool for monitoring nutrient CTS in aquatic environments.

A Novel Active Sampler Coupling Osmotic Pump and Solid Phase Extraction for in Situ Sampling of Organic Pollutants in Surface Water.

Active samplers for ambient monitoring of trace contaminants in surface water are highly desirable, but their use is often constrained by power supply. Here, we proposed a novel solution by coupling an improved osmotic pump (OP) with a solid-phase extraction (SPE) cartridge to construct a power-free active sampler for organic contaminants. The OP simply consisted of two cylindrical chambers separated by a reverse osmosis membrane. We, for the first time, added ion-exchange resins into the OP inlet chamber and successfully constructed OPs with a smooth and constant flow. In the OP-SPE sampler, water was continuously drawn through the SPE cartridge at a constant flow, and time-weighted average concentration over the sampling course may be easily calculated from the amount of target analytes retained on the SPE cartridge and water collected in the sampler. The OP-SPE samplers were deployed in a river to detect herbicides, and the measured concentrations were largely in agreement with the average of 11 daily spot samples. Given that a wide range of SPE cartridges are available for different classes of organic contaminants, this approach is versatile and may find widespread applications for in situ sampling of surface water under different conditions, including poorly accessible locations.

Survey and analysis for impact factors of psychological distress in HIV-infected pregnant women who continue pregnancy.

Objective: The objective of this study is to explore the psychological distress of HIV-infected pregnant women who continue pregnancy, and analyze the possible influencing factors. Methods: A total of 194 HIV-infected pregnant women who continue pregnancy were enrolled for this study by a convenient sampling method during June 2012-August 2016. Participants completed questionnaires including Hospital Anxiety and Depression Scale (HADS), Berger HIV Stigma Scale (BHSS), Distress Thermometer (DT) and Problem List (PL), and to determine the cut-off value of DT in the group. Results: The positive detection rate of psychological distress in the HIV-infected pregnant women who continue pregnancy was 69.1%, and the highest frequency of PL was the emotional problems. The positive detection rate of anxiety was 60.8%, the positive detection rate of depression was 54.1%, and the discrimination score was 113.16 ± 19.21. Spearman relevant analysis showed that psychological distress score was positively correlated with anxiety, depression and discrimination score (p < .001). Multiple linear regression analysis showed that relationship between husband and wife, family misfortune, Medicaid, chronic disease or high-risk pregnancy, viral load, CD4+T cell count, infection and confidentiality could affect the psychological distress (p < .05). The ideal cut-off value of DT in the group was 5. Conclusion: HIV-infected pregnant women who continue pregnancy have higher incidence of psychological distress, and the psychological distress is not inferior to cancer patients. The influencing factors are mainly related to the infection and pregnancy characteristics, and have nothing to do with the general social demographic characteristics. The DT can be used as a screening tool to quickly identify psychological distress of the group.

Variations in the isotopic composition of stable mercury isotopes in typical mangrove plants of the Jiulong estuary, SE China.

Variations in the composition of stable isotopes of mercury contained in tissues (root, stem, leaf, and hypocotyl or flower) of three typical mangrove plants (Kandelia candel, Aegiceras corniculata, and Bruguiera gymnorhiza), collected from the mangrove wetland of Jiulong estuary, SE China, were used to investigate the sources and transformation of mercury in the mangrove plants. Tissue samples from the plants were digested and mercury in the solution was pre-concentrated with purge-trap method and then analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that the mass dependent fractionation (MDF) of mercury ranged from -2.67 to -0.87 ‰ for δ 202Hg while the mass independent fractionation (MIF) of mercury isotopes ranged from -0.16 to 0.09 and -0.19 to 0.05 ‰ for Δ199Hg and Δ201Hg, respectively, relative to the standard NIST SRM 3133. The ratio of Δ199Hg/Δ201Hg was 0.991, indicating that the mercury had been photo-reduced before being accumulated in mangrove plants. Analyses of the data from MIF studies revealed that the major portion of the mercury measured in leaves (∼90 %) originated from the atmosphere while the source of over half of the mercury present in roots was the surficial sediment. This study, the first of its kind investigating the variations in isotopic composition of mercury in the tissues of mangrove plants, could be helpful to identify the source of mercury contamination in mangroves and understand the biogeochemical cycle of mercury in the estuarine mangrove wetlands.

Mercury isotope signatures of seawater discharged from a coal-fired power plant equipped with a seawater flue gas desulfurization system.

Seawater flue gas desulfurization (SFGD) systems are commonly used to remove acidic SO2 from the flue gas with alkaline seawater in many coastal coal-fired power plants in China. However, large amount of mercury (Hg) originated from coal is also transferred into seawater during the desulfurization (De-SO2) process. This research investigated Hg isotopes in seawater discharged from a coastal plant equipped with a SFGD system for the first time. Suspended particles of inorganic minerals, carbon residuals and sulfides are enriched in heavy Hg isotopes during the De-SO2 process. δ(202)Hg of particulate mercury (PHg) gradually decreased from -0.30‰ to -1.53‰ in study sea area as the distance from the point of discharge increased. The results revealed that physical mixing of contaminated De-SO2 seawater and uncontaminated fresh seawater caused a change in isotopic composition of PHg isotopes in the discharging area; and suggested that both De-SO2 seawater and local background contributed to PHg. The impacted sea area predicted with isotopic tracing technique was much larger than that resulted from a simple comparison of pollutant concentration. It was the first attempt to apply mercury isotopic composition signatures with two-component mixing model to trace the mercury pollution and its influence in seawater. The results could be beneficial to the coal-fired plants with SFGD systems to assess and control Hg pollution in sea area.