Relative contribution of multi-source water recharge to riparian wetlands along the lower Yellow River.

Rivers play a vital role in both the formation and maintenance of riparian wetland hydrology. However, few studies have focused on the response of water recharge of riparian wetlands to altered hydrological processes induced by water-sediment regulation practices. To fill this gap, our study investigated the contribution of multi-source water recharge of riparian wetlands in the lower Yellow River, as well as its influence both during and before the water-sediment regulation scheme of Xiaolangdi Dam. Our study is based on hydrochemistry and isotopic methods, using a Bayesian mixing model and artificial neutral network model. The results showed that riparian wetlands were fed by mixed sources, including groundwater, canals, the Yellow River, and precipitation. However, seasonal evaporation introduced additional variation, which affected the relative contribution of these sources across seasons. Among these sources, the Yellow River served as the main water source for recharging riparian wetlands, and its contribution varied both spatially and temporally (across seasons). Specifically, proximity of riparian wetlands was the primary factor explaining spatial variation in the contribution of Yellow River, while climatic (12.38%) and hydrological variabilities (87.62%) explained seasonal variation. Among these climatic and hydrological variables, suspended sediment content was the most important factor-with a relative contribution of 36.33%. By determining the contribution of the Yellow River to the recharge of riparian wetlands, our study has provided information which is beneficial to adaptive management of river-fed riparian wetlands, especially under the implementation of water-sediment regulation practices.

Concentration, Health Risk, and Hydrological Forcing of Heavy Metals in Surface Water Following Water-Sediment Regulation of the Xiaolangdi Dam in the Yellow River.

Water and sediment regulation aimed at aquatic ecosystems and preserving reservoir capacity to minimize the negative consequences of dams can fundamentally change the distribution of heavy metals (HMs) in the reservoir and downstream reaches. However, the effects of water and sediment regulation on variation in HMs are still poorly understood. In this study, the variations in concentration, contamination, human health risk, potential sources, and influencing factors of the metalloid As and HMs (Cr, Hg, Ni, Pb, and Zn) in surface water in the reservoir and the downstream reach of the Xiaolangdi Dam (XLD) following the operation of the water-sediment regulation scheme (WSRS) were determined. These results indicate that HM concentrations in the two post-WSRS seasons were much lower than the water quality standards, but were significantly increased over time due to the trapping effects of the XLD (p < 0.05, except for Zn). However, As concentration in the reservoir was significantly lower than that observed in downstream reaches, likely due to anthropogenic input from agricultural activities. Meanwhile, HM concentrations varied with distance to the dam, which displayed a distinct accumulation closer to the dam in the post-WSRS II season. The contamination of HMs, the carcinogenic risk of exposure to As, and the noncarcinogenic risks associated with exposure to Hg, Ni, Pb, and Zn via the direct ingestion pathway of drinking water were all within acceptable levels following the WSRS, but increased over time. The carcinogenic risk of Cr in the post-WSRS II season was at an unacceptably high level, particularly at sites near the dam. Hydrological characteristics (water level and flow rate) were the dominant factors in determining the distribution of HMs. These results can provide new insight for a better understanding of the variations in HMs following the water and sediment regulation practices, and guide future management in regulating the trapping effects of dams.

Impacts of water-sediment regulation on spatial-temporal variations of heavy metals in riparian sediments along the middle and lower reaches of the Yellow River.

The water-sediment regulation scheme (WSRS) of dams influences the desorption, resuspension, and deposition processes of riparian sediments, which in turn affect the spatial-temporal variations of heavy metals (HMs) in riparian sediments and leads to severe degradation of soil and water quality. However, the difference between the trapping effect of dams and the redistribution effects of the WSRS on HMs in riparian sediments, as well as the consecutively seasonal change of HMs after the WSRS, are rarely reported. To fill this gap, the concentrations of six HMs including Cd, Cr, Cu, Ni, Pb, and Zn in riparian sediments along the Xiaolangdi Dam (XLD) Reservoir and its downstream reach were investigated, and the contamination level and potential ecological risk of HMs were assessed, to differentiate the effects of the XLD and its WSRS on the concentration, contamination level, and potential ecological risks of HMs. The results indicated that the mean HM concentrations in riparian sediments were higher than the background values in the study area and showed significant spatial and temporal variations. However, the regional differences of HM concentrations caused by the trapping effect of the XLD were less than the seasonal differences caused by the redistribution effects of the WSRS. The contamination and ecological risk assessment indicated that riparian sediments in the study area were contaminated by the six HMs, particularly by Cd and Pb, which overall exhibited a high and moderate ecological risk, respectively. The sources for Pb were likely agricultural inputs, while the sources for Cd should be attributed to both industrial and agricultural inputs. Overall, the trapping effect of the XLD led to the accumulation of HMs in riparian sediments along the reservoir area, while the regulation effects of the WSRS resulted in the redistribution of HMs in riparian sediments from the reservoir area to the downstream reach.

Plant trait-environment trends and their conservation implications for riparian wetlands in the Yellow River.

Determining the relationship between plant functional traits and the environment are key for the protection and sustainable utilization of riparian wetlands. In the middle and lower reaches of the Yellow River, riparian wetlands are divided into seasonal floodplain wetlands (natural) and pond-like wetlands or paddy fields (artificial). Here, species composition differences were catalogued based on plant functional traits including origin, life history, and wetland affinity in natural and artificial wetlands. Wetland physicochemical characteristics and regional socio-economic parameters collected as indicators of environmental variables were used to analyze the plant functional trait-environment relationship. The results reveal that plant functional traits in the seasonal floodplain wetland are impacted by physicochemical characteristics of habitat. The abundance of annual plants tends to decrease with concentration of heavy metals, while species diversity is mainly determined by soil physical and chemical properties, especially soil pH and temperature. Specifically, wetland-obligate species (not in water) are more resistant to heavy metal content in water than species with other types of wetland affinity. Life history strategies of species in artificial sites tend to be significantly associated with animal husbandry and artificial populations, while the wetland affinity of species is mainly determined by regional agriculture, especially the installation of agricultural covered areas. Furthermore, water quality and nutrients in suspended sediments from the Yellow River affected species diversity and life history strategies by affecting water and soil conditions of surrounding wetlands, especially conductivity and phosphorus levels.

Osteoblast proliferation on hydroxyapatite coated substrates prepared by right angle magnetron sputtering.

The preparation of hydroxyapatite (HA) coatings via a versatile right-angle magnetron sputtering (RAMS) approach for use as a biomaterial has recently been reported. RAMS coatings show some advantages over conventionally sputtered films in that room temperature deposition yields nanocrystalline and nearly stoichiometric HA coatings under appropriate conditions, thereby avoiding the troublesome post deposition annealing treatment. In this article, we present an exploratory study of the biocompatibility of RAMS HA coatings deposited on metallic substrates. RAMS HA coatings with a thickness around 500nm were prepared on various substrates. X-ray diffraction (XRD) analysis showed that the as-deposited HA coatings were polycrystalline with some strongly preferred orientations. Atomic force microscopy (AFM) results showed that the coatings were rather smooth with surface roughness on the order of 10 nm. X-ray photoelectron spectroscopy (XPS) confirmed that the surface chemistry was nearly stoichiometric. To study the biocompatibility of these coatings, murine pre-osteoblastic MC3T3-E1 cells were seeded onto various substrates. Cell density counts using fluorescence microscopy showed that the best osteoblast proliferation is achieved on an HA RAMS-coated titanium substrate. Additionally, in preliminary studies the influence of Zn, Mg, and Al incorporation in the HA crystal lattice on the in vitro behavior was also evaluated. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications.