Observational study of tidal mixing asymmetry and eddy viscosity-shear covariance – induced residual flow in the Jiulong River estuary

Abstract(#br)An observation study was conducted at three stations in the inner regime of the Jiulong River estuary to examine the tidal mixing asymmetry and its associated residual flow induced by eddy viscosity-shear covariance (ESCO). The water columns at the observation stations were approximately well-mixed during the later flood and were stratified during the early ebb, a typical tidal mixing asymmetry. Corresponding to the tidal variation of stratification, the Reynolds stress and vertical eddy viscosity, which were obtained using the ADCP variance method, exhibited distinct differences in the magnitude and vertical structure between flood and ebb tides. The ESCO flow was calculated using the decomposition method for estuarine circulation, revealing a two-layer vertical structure similar to density-driven flow but with a much greater magnitude, confirming the findings of previous generic model studies that the ESCO flow dominates the density-driven flow in periodically stratified estuaries. The drivers of tidal mixing asymmetry were explored using the potential energy anomaly method. Longitudinal straining reduced stratification during flood tides and reinforced stratification during ebb tides, whereas longitudinal advection acted in the opposite manner. Although the contribution of lateral circulation to stratification was neglected due to the lack of lateral observation data, scaling analysis revealed that lateral advection was important in the longitudinal dynamics and tidal evolution of stratification and warrants further study

Urbanization increased river nitrogen export to western Taiwan Strait despite increased retention by nitrification and denitrification

Abstract(#br)Urban development and increased human activities impose major environmental stress on the receiving bodies of water. Although urban rivers have been recognized as hotspots of regional nitrogen (N) pollution, detailed measurements of river nutrient species in response to urbanization are rarely reported, so the impacts of urban development on N cycling processes and transport to coast remains unclear. Here we investigated the changes in N species (concentration, composition and isotope) and N functional genes between upstream and downstream sections of several rivers affected by urban development in western Taiwan Strait under various flow conditions (low, medium and high flow). Our results suggest that urban sewage (high ammonium) is the predominant substrate that stimulated nitrification and subsequently denitrification and gaseous N removal (N 2 O, N 2 ). Nitrifying and denitrifying functional genes increased their abundance along the urban rivers. There were hydrological and meteorological controls on urban rivers regulating changes in nitrogen retention between seasons. Overall, the enhanced microbe-driven N retention could not balance the increase of urban N loading. Consequently, urbanization increased riverine N export and caused other changes in nutrient supply such as changing the nutrient ratio (N:P:Si ratio), increasing the potential for eutrophication both in the river and in receiving coastal ecosystems

P relim inary resu lts concern ing th e spa tio2tempora l pa ttern and mechan ism of n itrogen sources and expor ts in th e J iu long R iver wa tersh ed

[摘要]：综合运用定位监测、野外试验、模型模拟与G IS技术等手段和方法, 定量研究了南亚热带地区九龙江流域和五川小流域氮的大气沉降、河 流输送(地表径流)、淋失、反硝化和氨挥发等输入输出(源汇)时空模式与机理. 结果表明, 九龙江流域氮/ 源0以化肥与饲料输入为主(占总输 入125. 6kg# hm- 2的86% ), 氮/ 汇0以氨挥发和河流输送为主(占总输出72. 9kg# hm- 2的82% ). 氮输入后50%以上进入大气和水环境, 14. 5% 通过河流输送至河口与近海. 大气氮沉降通量为14. 9kg# hm- 2, 其中干沉降占34%, 湿沉降占66%, 形成1B2 的干湿沉降结构;源于化肥施用与 畜禽养殖引起的强烈氨挥发, 氮沉降集中在春夏两季(占全年80% ), 且以铵态氮为主( 39%以上). 氮的径流输出及河流输送受人为氮输入与 水文条件的双重控制, 2004年九龙江向厦门海域输送无机氮11. 5kg# hm- 2, 其中90%发生在春夏秋季(同期流量占全年89% ); 五川小流域总 氮径流输出负荷为67. 1kg# hm- 2, 其中85%发生在施肥量大、降雨集中的春夏两季(作物生长期); 基流与降雨径流分别贡献25%和75%. 总 氮淋失负荷为27. 5kg# hm- 2, 占总输入的9%; pH < 5的酸性土壤带正电荷导致氮淋失以铵态氮为主(约占40% ). 九龙江流域反硝化通量为 71 7 kg# hm- 2, 而氨挥发高达42. 1kg# hm- 2, 氨挥发主要来自化肥施用与畜禽养殖(分别贡献50% 和39% ). 减少春夏时期肥料氮的输入(养分 管理), 有效截留雨季的降雨径流(水文控制)是该流域氮素管理的关键.国家自然科学基金国际(地区)合作交流项目( No. 40810069004); 福建省/ 十五0重大科技资助项目(N o. 2002H 009

TGF-β Regulates DNA Methyltransferase Expression in Prostate Cancer, Correlates with Aggressive Capabilities, and Predicts Disease Recurrence

DNA methyltransferase (DNMT) is one of the major factors mediating the methylation of cancer related genes such as TGF-β receptors (TβRs). This in turn may result in a loss of sensitivity to physiologic levels of TGF-β in aggressive prostate cancer (CaP). The specific mechanisms of DNMT's role in CaP remain undetermined. In this study, we describe the mechanism of TGF-β-mediated DNMT in CaP and its association with clinical outcomes following radical prostatectomy.We used human CaP cell lines with varying degrees of invasive capability to describe how TGF-β mediates the expression of DNMT in CaP, and its effects on methylation status of TGF-β receptors and the invasive capability of CaP in vitro and in vivo. Furthermore, we determined the association between DNMT expression and clinical outcome after radical prostatectomy. We found that more aggressive CaP cells had significantly higher TGF-β levels, increased expression of DNMT, but reduced TβRs when compared to benign prostate cells and less aggressive prostate cancer cells. Blockade of TGF-β signaling or ERK activation (p-ERK) was associated with a dramatic decrease in the expression of DNMT, which results in a coincident increase in the expression of TβRs. Blockade of either TGF-β signaling or DNMT dramatically decreased the invasive capabilities of CaP. Inhibition of TGF-β in an TRAMP-C2 CaP model in C57BL/6 mice using 1D11 was associated with downregulation of DNMTs and p-ERK and impairment in tumor growth. Finally, independent of Gleason grade, increased DNMT1 expression was associated with biochemical recurrence following surgical treatment for prostate cancer.Our findings demonstrate that CaP derived TGF-β may induce the expression of DNMTs in CaP which is associated with methylation of its receptors and the aggressive potential of CaP. In addition, DNMTs is an independent predictor for disease recurrence after prostatectomy, and may have clinical implications for CaP prognostication and therapy

Porewater exchange drives the dissolved silicate export across the wetland‐estuarine continuum

Coastal wetlands are an important hotspot for nutrient cycling and transport from the land to the ocean. Silicon (Si) as a vital biogenic element affects plant growth and health of coastal ecosystems. The understanding of key factors and processes controlling dissolved silicate (DSi) exchange between the wetlands and coastal water has been limited due to the lack of measured data. We carried out intensive investigations of time-series DSi concentrations and porewater exchange across the Sediment-Water Interface (SWI) along a tidal creek with a mangrove-salt marsh gradient during neap and spring tides in 2020. Seasonal observations of surface water in a tidal creek and Zhangjiang Estuary (Fujian Province, China) were conducted from 2017 to 2020. The results showed that there was a net export of DSi from the mangroves to tidal creek with rates of 2.11 and 2.40 mmol m-2 d-1 in neap and spring tides respectively, suggesting the mangroves served as the source of DSi. However, the salt marshes had a net DSi import with one or two orders of magnitude lower than the export from the mangroves. DSi export across the wetland‐estuarine continuum was largely controlled by porewater exchange, groundwater geochemistry (pH, temperature) and plant root uptake. Groundwater in the mangroves has larger ratios of DSi : DIN (dissolved inorganic nitrogen) (2.5 ± 0.6) and DSi : DRP (dissolved reactive phosphorus) (1257 ± 35) compared with surface water. The net export of DSi from mangroves would modify the nutrient stoichiometry and mitigate the effects of reduced river DSi flux caused by damming on coastal ecosystem. This study provides new insights into the wetland Si cycling for sustaining coastal ecosystem health

A GIS-based approach for mapping direct use value of ecosystem services at a county scale: Management implications

A GIS-based approach was designed to spatially estimate direct use value of ecosystem services and to map results for a case study at county scale. The approach highlights the use of GIS to collect data, perform spatial analysis, and map economic values of ecosystem services. Three key steps of spatial valuation for agricultural products, forest products, and tourism services were illustrated in the GIS-based technical framework. We applied this approach to the Tiantai County (1423.8 km2) in Zhejiang province of southeast China. Selected components of natural products and tourism services in the case area were mapped as data layers in GIS, with each layer containing monetary values for every 25 m cell. The total direct use value of ecosystem services was estimated in RMB to be approximately 538 million Yuan in 2005 (Chinese currency, 8.2 Yuan = US$1), of which agricultural products, forest products and tourism services accounted for 65%, 30% and 5%, respectively. The critical areas for management purpose were identified depending on the heterogeneity of direct use services learned from the case study. The spatially explicit measures provide a mechanism for incorporating spatial context into ecosystem services evaluation. Based on the present GIS-based approach and case study, the suggestions and implications for local resources protection and eco-environmental management were extensively discussed. The work was expected to highlight research avenues to advance the ecosystem services framework as an operational basis for regional ecosystem-based management.Ecosystem services Direct use value Geographic Information System (GIS) Valuation approach Management implications

Nitrogen export by surface runoff from a small agricultural watershed in southeast China: seasonal pattern and primary mechanism

International Cooperation and Exchanges NSFC [408100 69004]; Department of Science and Technology of Fujian Province, P.R. China [2002H009]The seasonal pattern and primary mechanism of nitrogen (N) export by surface runoff from the Wuchuan subwatershed (WCW), an agricultural upper watershed (1.88 km(2)) located in southeast China, were investigated based on extensive streamwater measurements in 2004-2005 under subtropical climatic conditions. The results disclosed a highly variable but strong linkage between hydrological and anthropogenic controls and N export. N export via surface runoff presented a significant seasonal pattern caused by changes in rainfall and watershed N input. Approximately 75% of the annual N export (67 kg ha(-1)) was flushed by those storm runoff mainly occurred during the wet season (March through September). The WCW dataset of N concentrations and loads during both baseflow and stormflow implied an interactive effects of anthropogenetic N input and hydrology conditions: N export was flush-driven in late spring, summer and autumn (wet season), but highly related with soil N in winter and early spring. Compared to undisturbed watersheds under similar rainfall conditions, WCW exported a considerable amount of N due to intensive fertilizer application (a mean of 690 kg N ha(-1) year(-1), commonly as surface applications). This work provides a first characterization of a small agricultural Chinese catchment under subtropical climates and its associated N export behavior