Spatiotemporal variation in precipitation during rainy season in Beibu Gulf, South China, from 1961 to 2016

The spatiotemporal variation in precipitation is an important part of water cycle change, which is directly associatedwith the atmospheric environment and climate change. The high-resolution spatiotemporal change of precipitation is still unknown inmany areas despite its importance. This study analyzed the spatiotemporal variation in precipitation in Beibu Gulf, South China, during the rainy season (fromApril to September) in the period of 1961–2016. The precipitation datawere collected from 12 national standard rain-gauge observation stations. The spatiotemporal variation in precipitation was evaluated with incidence rate and contribution rate of precipitation. The tendency of variations was analyzed using the Mann–Kendall method. The precipitation in the rainy season contributed 80% to the total annual precipitation. In general, there was an exponential decreasing tendency between the precipitation incidence rate and increased precipitation durations. The corresponding contribution rate showed a downward trend after an initial increase. The precipitation incidence rate decreased with the rising precipitation grades, with a gradual increase in contribution rate. The precipitation incidence rate and contribution rate of 7–9 d durations showed the significant downward trends that passed the 95% level of significance test. The results provide a new understanding of precipitation change in the last five decades, which is valuable for predicting future climate change and extreme weather prevention and mitigation

Approximation of the ergodic measure of SDEs with singular drift by Euler-Maruyama scheme

We study the approximation of the ergodic measure of the following stochastic differential equation (SDE) on $\mathbb{R}^d$: \begin{eqnarray}\label{e:SDEE} d X_t &=& (b_1(X_t)+b_2(X_t)) d t+\sigma(X_t) d W_t, \end{eqnarray} where $W_t$ is a $d$-dimensional standard Brownian motion, and $b_1: \mathbb{R}^d \mapsto \mathbb{R}^d$, $b_2: \mathbb{R}^d \mapsto \mathbb{R}^d$ and $\sigma: \mathbb{R}^d \mapsto \mathbb{R}^{d\times d}$ are the functions to be specified in Assumption 2.1 below. In particular, $b_1$ satisfies $b_1\in \mathbb{L}^\infty(\mathbb{R}^d)\cap \mathbb{L}^1(\mathbb{R}^d)$ or $b_1 \in \mathcal{C}_b^{\alpha}(\mathbb{R}^d)$ with $\alpha\in (0,1)$, which makes the standard numerical schemes not work or fail to give a good convergence rate. In order to overcome these two difficulties, we first apply a Zvonkin's transform to SDE and obtain a new SDE which has coefficients with nice properties and admits a unique ergodic measure $\widehat \mu$, then discretize the new equation by Euler-Maruyama scheme to approximate $\widehat \mu$, and finally use the inverse Zvonkin's transform to get an approximation of the ergodic measure of SDE, denoted by $\mu$. Our approximation method is inspired by Xie and Zhang [22]. The proof of our main result is based on the method of introducing a stationary Markov chain, a key ingredient in this method is establishing the regularity of a Poisson equation, which is done by combining the classical PDE local regularity and a nice extension trick introduced by Gurvich [10]

Effect of drip irrigation with saline water on the construction of shelterbelts for soil and groundwater protection in the hinterland of the Taklimakan Desert, China

Fan, J., Wei, Y., Xinwen, W., & Yang, X. (March-April, 2017). Effect of drip irrigation with saline water on the construction of shelterbelts for soil and groundwater protection in the hinterland of the Taklimakan Desert, China. Water Technology and Sciences (in Spanish), 8(2), 19-30. In order to perceive the effect of drip irrigation with saline water in the desert hinterland on plant growth of shelterbelts and underground environment (vadose zone and groundwater), by developing water-saving irrigation technology to ensure the scientifically substantiated utilization of water resources, four different irrigation cycle experiments (difference in irrigation period I: 12d; IV: 25d; II & III: 25d in the summer and the respective spring and autumn periods, which were the same: 15d and 20d, respectively) were carried out during the irrigation season in four different regions of well irrigation area. In this paper, regular on-site investigation was adopted to observe soil, water, and salt. Single-factor analysis of variance and least significant difference (LSD) are used to analyze the data acquired by the survey method and for measuring plant growth, complemented with the comparison of groundwater level and chemical index before and after irrigation. The results showed that the reduction of annual irrigation volume from 420 mm to 201.6 mm had almost no effect on plant growth and could save more than 50% of the water as compared to treatment I. Considering the impact on the height-growth of Tamarix, treatment II could be optimized, so that more than 30% of the water could be saved as compared to treatment I. Three days after irrigation, the salt was leached through the soil body into the groundwater. The groundwater level in the shelterbelt area, total dissolved solids (TDS), and total hardness exhibited an upward trend. Six days after irrigation, the high salt concentration region was found at a depth of 0–30 cm

A Review of the Role of Natural Clay Minerals as Effective Adsorbents and an Alternative Source of Minerals

The minerals with unique properties such as natural clay minerals (NCMs) have promising approach in environmental and industrial sphere. In fact, under some specific conditions the NCMs could be used either as effective adsorbent material or alternative source of minerals. This chapter presents an outline of a general review of factors that affect the application ability of NCMs and a descriptive analysis of NH4+ and REE adsorption behavior and extraction of rare earth elements (REE) by an ion-exchange with NH4+ ions onto NCMs. Clays and NCMs both effectively remove various contaminants from aqueous solution and serve as alternative sources of minerals, as extensively discussed in this chapter. This review compiles thorough literature of current research and highlights the key findings of adsorption (NH4+ and REE) that use different NCMs as adsorbents or alternative sources of minerals (i.e., REE). The review confirmed that NCMs excellently remove different cations pollutants and have significant potential as alternative source of REE. However, modification and further development of NCMs applications for getting the best adsorption and the best extraction of REE onto NCMs, which would enhance pollution control and leaching system is still needed

Spatiotemporal Variation in Extreme Precipitation in Beijiang River Basin, Southern Coastal China, from 1959 to 2018

Extreme precipitation events have caused serious impacts on natural ecosystem and human society and have attracted increasing attention in recent years. IPCC AR6 WG I report highlighted a lack of conclusive consensus on the change trend of extreme precipitation in some basins and variation (increase or decrease) between regions. Based on seven precipitation indexes defined by ETCCDI, using daily precipitation data observed by 18 national reference meteorological stations in China during 1959–2018, this study analysed spatiotemporal variation trend of extreme precipitation in the Beijiang River Basin, Southern Coastal China, in recent 60 years, using Mann–Kendall (M-K) trend test, coefficient of variation, and continuous wavelet transformation. M-K test results showed that there were mutations in all seven precipitation indexes, and mutation points were mainly concentrated in two periods (1986–1991 and 2005–2010). The change range of each index after mutation was generally greater than that before mutation. Continuous wavelet transformation showed that each indicator had a significant oscillation period of 2–4 year in most time domains. The southeastern part of the basin (Fogang and Qingyuan) was the center of extremely heavy precipitation, and most precipitation indexes decreased from this area to the surrounding area. As far as the basin as a whole was concerned, consecutive wet days (CWD) declined significantly (passing 0.05 of confidence test), and there was a significantly positive correlation between annual distribution of R95ds and monthly precipitation (p < 0.001). The research results expand our understanding of regional water cycle and extreme climate change, guide the allocation and management of water resources related to regional industrial and agricultural activities, and provide reference for disaster prevention and mitigation

Potential to Reduce Chemical Fertilizer Application in Tea Plantations at Various Spatial Scales

Tea is the main commercial crop grown in China, and excessive application of chemical fertilizers in tea plantations is common. However, the potential to reduce chemical fertilizer use in tea plantations is unclear. In this study, Zhejiang Province was selected as the research object to systematically analyze the potential for tea plantation chemical-fertilizer reduction at different spatial scales. The geographic information system-based analytic hierarchy process method and Soil and Water Assessment Tool model were used to determine the chemical fertilizer reduction potential at the province scale and watershed scale, respectively. At the field scale, two consecutive years of field experiments were conducted on a tea plantation. Province-level analysis showed that 51.7% of the area had an average total fertilization intensity greater than 350 kg/hm2 and a high reduction potential. Watershed analysis revealed that chemical fertilizer reduction had better potential in reducing total nitrogen and total phosphorus inputs to runoff in the short term, whereas 50% organic fertilizer substitution was the best strategy to achieve long-term effects. The field experiments further proved that organic fertilizer substitution balanced tea growth and environmental protection. This study provides a useful method to investigate strategies to reduce chemical fertilizer use in tea-growing areas

Characterization of Yemeni Natural Zeolite (Al-Ahyuq Area) and its Environment Applications: A Review

This research characterizes Yemeni natural zeolitic-rich tuff (Al-Ahyuq area) and its potential in environmental applications. A total of 40 zeolite samples of Al-Ahyuq area were selected and fully characterized by a variety technique to obtain the mineralogical and physicochemical parameters. Our results show that the purities of zeolite minerals range from 78 to ~100% zeolite. Clinoptilolite and mordenite are the major mineral zeolite whereas heulandite and stilbite occur in minor amounts present in the zeolite deposit. Accessory minerals include quartz, illite, mica, feldspar, kaolinite, and smectite. In addition, the chemical compositions of Al-Ahyuq zeolitic tuffs are found to be comparable with other zeolites compositions of high economic value in the world. Moreover, its environment application was also discussed in this study

Understanding the role of natural clay minerals as effective adsorbents and alternative source of rare earth elements: Adsorption operative parameters

To better understand the influence of structure and surface properties of NCMs towards REE, requires individual research for each NCM. The adsorption/extraction for light (La3+) and heavy (Yb3+) REE of kaolinite (Kao), montmorillonite (Mt), muscovite (Ms), illite (Ilt), were systematically investigated and compared. Additionally, all the NCMs were fully characterized by XRD, XRF, XPS, Zeta potential and nitrogen adsorption-desorption isotherms to build the relationship between adsorption/extraction mechanism and minerals' property. Our experiments show that the Mt. exhibits highest adsorption and regeneration efficiencies for both La3+ and Yb3+ and decrease in the order of Mt > Ms > Ilt > Kao, while Kao has highest extractions efficiencies for both REE in the order of Kao > Ilt > Mt > Ms 89% for La3+ and 85% for Yb3+ were achieved from Kao and the lowest extractions were obtained from Ms. (63% for La3+ and 57% for Yb3+). The lack of Ms. on both reuse and extraction characteristics is believed to be related to presence of iron oxide associated with Ms. In addition, the important role of the pH in extraction of REE from NCMs was evidenced, when REE-NCMs come into contact with the NH(4)(+ )solution, the pH is rapidly increased over initial pH solution for both Mt. and Ms., thus leading to the decrease of the availability of ion-exchangeable REE with NH(4)(+ )ions. The results illustrated that the structure and surface properties of NCMs are also the key factors that affect the rare earth leaching, thus identifying the types of NCMs and associated impurities in clay materials are important, either for getting the best leaching system or in developing a new one