In Situ Simultaneous Analysis of Nitrogen and Phosphorus Migration in Urban Black Odorous Runoff.

The extremely serious urban runoff eutrophication and black odorous phenomenon pose a significant threat to the lake aquatic ecosystem, resulting in a significantly increased frequency, magnitude, and duration of algal blooms in lakes. However, few investigations focus on small tributaries of the lakes, despite the ubiquity and potential local importance of these runoffs. Thus, the labile sediments NH4+-N, NO3--N, PO43-, Fe2+, and S2- in black odorous runoff at Wuxi were overall analyzed at high resolution using diffusive gradients in thin films (DGT). The variations in labile N, P, Fe, and S distribution profiles at different sampling sites indicated high heterogeneity in sediments. The concentrations of labile P, Fe, and S showed synchronous variation from the sediment-water interface (SWI) up to -20 mm along sediment profiles. Moreover, there existed a significant positive correlation among labile P, Fe, and S concentrations (p < 0.05), which might represent typical odor compounds' FeS and H2S synchronous release process in urban runoff. Furthermore, the apparent diffusion fluxes of labile P, Fe, and S across the SWI were all released upward, while fluxes of NH4+-N and NO3--N release downward, indicating the sediments act as source and sink of P and N, respectively. Sediments' potential for endogenous P and N fractions release results in the black-odorous water, and sediment finally abouchement the Taihu, which intensifies further lake eutrophication phenomenon.

The variations of labile arsenic diffusion driven by algal bloom decomposition in eutrophic lake ecosystems.

The vertical labile arsenic (As) concentration and diffusion pattern variations in eutrophic lakes were investigated using in situ techniques of diffusive gradients in thin films (DGT) and high-resolution dialysis (HR-Peeper) in the typical eutrophic system of Lake Taihu in China. In addition, simulation experiments were used to reveal labile As distributions in sediment profiles under the influence of algae blooms and wind fluctuations. Our results indicated that eutrophication could lead to the migration and transformation of As fractions, including increased As bioavailability, as well as varied diffusion patterns. The sulfate released from algae decomposition reduced to H2S and formed FeS, which weak adsorbability contributed to the increased mobility of the As fractions. Meanwhile, further decomposition released a large quantity of algae-derived organic matter which competed with the adsorbed As, leading to more endogenous As migrating to the overlying water. Accordingly, the H2S production presented a likely explanation for the changed distribution of labile As and contributed to labile As concentrations in the sediment profiles significantly increasing at depths of -20 mm to -60 mm in the early stages of the simulation experiment. Moreover, the areas of enhanced diffusion patterns with high concentrations of As obviously expanded. However, following the complete decomposition of the algae, the organic matter component significantly changed, suggesting an explanation for the variations in distribution of labile As. All the diffusion pattern variations showed similar trends. Consequently, variation of labile As diffusion patterns could indicate the decomposition and eutrophication levels of freshwater ecosystems.

High-resolution characteristics and mechanisms of endogenous phosphorus migration and transformation impacted by algal blooms decomposition.

Extremely high phosphorus (P) concentrations can be found in eutrophic freshwater sediments during algal blooms (ABs). However, few investigations have revealed the mechanism of labile P production in anoxic sediments following ABs decomposition. This limits our understanding of P cycling and mitigation of ABs in aquatic ecosystems. To identify such a mechanism, we conducted a microcosm experiment to identify how ABs decomposition enhances endogenous P release, using the combined techniques of diffusive gradients in thin films, high-resolution dialysis, and 16S rRNA amplicon sequencing. We show the concentrations of labile iron, manganese, sulfide, and P can be well predicted by quality and quantity of algal biomass. The relative abundance of iron reduction bacteria positively correlated with the decrease of pH induced by ABs decomposition, suggesting that this decomposition facilitates microbial iron and manganese reduction. In addition, the reductive dissolution of iron and manganese oxides leads to the labile P release, resulting in higher concentrations of labile P in those sediments affected by ABs compared with those not affected. The P fluxes in the algae-dominated regions exhibited higher values in the algae group than in the control group, with gains of 14.07-100.04%. Furthermore, endogenous P release is strongly controlled by Mn when the Fe(II):Mn(II) ratio is low (below 0.47), and by both Fe and Mn when the Fe(II):Mn(II) ratio is high (above 0.63). Our results quantify the endogenous P diffusion fluxes across the sediment-water interface can be attributed to ABs decomposition, and are therefore useful for further understanding of P cycling in freshwater.

High-resolution distribution of internal phosphorus release by the influence of harmful algal blooms (HABs) in Lake Taihu.

The Mechanisms driving phosphorus (P) release in sediment of shallow lakes is essential for managing harmful algal blooms (HABs). Accordingly, this study conducted field monitoring of labile P, iron (Fe), sulfur (S), and dissolved manganese (Mn) in different biomass of algae in Lake Taihu. The in-situ technique of ZrO-Chelex-AgI (ZrO-CA) diffusive gradients in thin-films (DGT) and high-resolution dialysis sampler (high resolution-Peeper (HR-Peeper)) were used to measure labile P, Fe, S, and dissolved Mn, as well as their apparent diffusion fluxes at the sediment-water interface (SWI). In addition, the distribution of iron-reducing bacteria (IRB) and sulfate-reducing bacteria (SRB) in sediments was also detected. Results showed that high HABs biomass promoted the reduction of sulfate into labile S, however, IRB is the dominant species. Thus, labile Fe concentrations greatly exceeded labile S concentrations across all sites, indicating that microbial iron reduction (MIR) is the principal pathway for ferric iron reduction. Furthermore, the simple relationship analysis revealed the principal influence P migration and transformation is the Fe-P in high algal biomass sites, while Fe and Mn redox reactions did not significantly influence labile P mobilization in low algal areas.

[Therapeutic effect of acupoint injection as adjuvant treatment on dry eyes of convalescent herpes simplex keratitis].

OBJECTIVE: To evaluate the clinical effect of acupoint injection of houttuynia cordata as the accessory treatment on dry eyes of convalescent herpes simplex keratitis (HSK). METHODS: A total of 60 patients with dry eyes of convalescent HSK were randomized into an observation group and a control group, 30 cases in each one. In the control group, the artificial tears and anti-inflammatory drugs were combined in treatment. In the observation group, on the base of the treatment as the control group, the acupoint injection of houttuynia cordata at Neiqiuhou (Extra) was combined, 3 mL each time, once a day. After consecutive 3 injections, the injection was adjusted to be once every two days, consecutively for 3 times. The treatment for 6 times was as one course and one course of treatment was required. Separately, before treatment and in 7, 15 and 30 days after treatment, the changes of the scores of visual analogue scale (VAS), theresults of SchirmerⅠtest (SⅠT), the tear break-up time (BUT) and the score of corneal fluorescein staining (CFS) were observed and analyzed in the patients of the two groups. RESULTS: In 7, 15 and 30 days after treatment, VAS scores and CFS scores were all reduced as compared with those before treatment in the patients of the two groups (P<0.05), and the scores of VAS and CFS in the observation group were lower than those in the control group (P<0.05). In 7, 15 and 30 days after treatment, the values of SⅠT and BUT were all increased as compared with those before treatment in the patients of the two groups (P<0.05), and the values in the observation group were higher than the control group in 15 and 30 days after treatment (P<0.05). CONCLUSION: Acupoint injection of houttuynia cordata promotes corneal epithelial recovery, reduces the discomfort symptoms as well as increases tear secretion and the stability of tear film in dry eyes of convalescent herpes simplex keratitis.