Assessment of the Distribution,Sources and Potential Ecological Risk of Heavy Metals in the Dry Surface Sediment of Aibi Lake in Northwest China

The distribution, sources and potential ecological risk of heavy metals in the sediment of lakes in eastern China and other areas of the world that have undergone rapid economic development have been widely researched by scholars. However, this is not true for heavy metals in the sediment of rump lakes in the arid regions of China and world-wide. Because of this, we chose Aibi Lake to serve as a typical rump lake in an oasis in an arid area in northwest China for our study. Sediment samples were collected from the lake and then the quantities of the heavy metals Pb, Ni, Cd, Cu, Zn, Hg and Cr were measured. Then using a variety of statistical methods, we analyzed the distribution, sources, pollution status and the potential ecological risk of these metals. The results show that: (1) The amounts of the seven heavy metals all fell within the Second Soil National Standard, but the average and maximum values were all higher than the background values of Xinjiang in northwest China. (2) Multivariate statistical analysis determined that the Cd, Pb, Hg and Zn in the sediment were mainly derived from man-sources, and Cu, Ni, and Cr were mainly from the natural geological background. (3) Enrichment factor analysis and the geo-accumulation index evaluation method show that Cd, Hg and Pb in the surface sediment of the Aibi Lake were at low and partial pollution levels, while Zn, Cr, Ni and Cu were at no and low pollution levels. (4) Calculation of the potential ecological hazards index found that, among the seven tested heavy metals, Cd, Hg and Pb were the main potential ecological risk factors, and the contribution of each was 42.6%, 28.6%, and 24.0%, respectively. Cd is the main potential ecological risk factor, followed by Hg and Pb. This work revealed that recent economic development of the Aibi Lake Basin has negatively influenced the accumulation of heavy metals in the sediments of the lake, and, therefore, we should pay increasing attention to this problem and take effective measures to protect the ecology of the Aibi Lake Basin. This work can provide a scientific basis for an early warning of heavy metal pollution and for protection of the environment. Furthermore, it can serve as a reference when creating policies for the economic development in Aibi Lake Basin and environmental protection of rump lakes in arid regions of northwest China and other areas of the world.     

Controlling Factors and Pollution Assessment of Potentially Toxic Elements in Topsoils of the Issyk-Kul Lake Region,Central Asia

The Issyk-Kul Lake region is well known for its magnificent scenery and unique scientific significance. With multivariable statistical methods, the contents of several geochemical elements (Fe, Mn, V, Zn, Cr, Co, Ni, Cu, As, Mo, Cd, Sb, Tl, Pb, and Hg) and total organic matter of 61 topsoil samples were analyzed, and then, the results were used to assess the environmental factors controlling the concentrations of potentially toxic elements (PTE) in the region. The results showed that most of the elements including Fe, Mn, V, Cr, Co, Ni, Cu, As, and Sb reflected the natural state, but several PTE (Zn, Mo, Hg, Cd, Pb, and Tl) had been influenced by anthropogenic factors. Among these, Zn, Mo, Hg, and Cd were significantly correlated with the organic matter content, which suggests that agricultural soils will accumulate more PTE. From the calculations for the human risk assessment of anthropogenically derived PTE (Zn, Mo, Hg, Cd, Pb, and Tl), the risks for ingestion in this region were found to be higher than those for inhalation and dermal absorption; however, the results also suggested there are no non-carcinogenic risks for all anthropogenically influenced PTE in the current state.     

The Occurrence,Sources and Spatial Characteristics of Soil Salt and Assessment of Soil Salinization Risk in Yanqi Basin,Northwest China

In order to evaluate the soil salinization risk of the oases in arid land of northwest China, we chose a typical oasis-the Yanqi basin as the research area. Then, we collected soil samples from the area and made comprehensive assessment for soil salinization risk in this area. The result showed that: (1) In all soil samples, high variation was found for the amount of Ca²⁺ and K⁺, while the other soil salt properties had moderate levels of variation. (2) The land use types and the soil parent material had a significant influence on the amount of salt ions within the soil. (3) Principle component (PC) analysis determined that all the salt ion values, potential of hydrogen (pHs) and ECs fell into four PCs. Among them, PC1 (C1^-, Na⁺, SO₄ ^2-, EC, and pH) and PC2 (Ca²⁺, K⁺, Mg²⁺and total amount of salts) are considered to be mainly influenced by artificial sources, while PC3 and PC4 (CO₃ ^- and HCO₃ ^2-) are mainly influenced by natural sources. (4) From a geo-statistical point of view, it was ascertained that the pH and soil salt ions, such as Ca²⁺, Mg²⁺ and HCO₃ ^-, had a strong spatial dependency. Meanwhile, Na⁺ and Cl^- had only a weak spatial dependency in the soil. (5) Soil salinization indicators suggested that the entire area had a low risk of soil salinization, where the risk was mainly due to anthropogenic activities and climate variation. This study can be considered an early warning of soil salinization and alkalization in the Yanqi basin. It can also provide a reference for environmental protection policies and rational utilization of land resources in the arid region of Xinjiang, northwest China, as well as for other oases of arid regions in the world.     

The Disastrous Effects of Salt Dust Deposition on Cotton Leaf Photosynthesis and the Cell Physiological Properties in the Ebinur Basin in Northwest China

Salt dust in rump lake areas in arid regions has long been considered an extreme stressor for both native plants and crops. In recent years, research on the harmful effects of salt dust on native plants has been published by many scholars, but the effect on crops has been little studied. In this work, in order to determine the impact of salt dust storms on cotton, we simulated salt dust exposure of cotton leaves in Ebinur Basin in Northwest China, and measured the particle sizes and salt ions in the dust, and the photosynthesis, the structure and the cell physiological properties of the cotton leaves. (1) Analysis found that the salt ions and particle sizes in the salt dust used in the experiments were consistent with the natural salt dust and modeled the salt dust deposition on cotton leaves in this region. (2) The main salt cations on the surface and inside the cotton leaves were Na⁺, Ca²⁺, Cl^- and SO₄^2-, while the amounts of CO₃^- and HCO₃^- were low. From the analysis, we can order the quantity of the salt cations and anions ions present on the surface and inside the cotton leaves as Na⁺>Ca²⁺>Mg²⁺>K⁺ and Cl^->SO₄^2->HCO₃^->CO₃^-, respectively. Furthermore, the five salt dust treatment groups in terms of the total salt ions on both the surface and inside the cotton leaves were A(500g.m^-2)>B(400g.m^-2)>C(300g.m^-2)>D(200g.m^-2)>E(100g.m^-2)>F(0g.m^-2). (3)The salt dust that landed on the surface of the cotton leaves can significantly influence the photosynthetic traits of P_n, PE, C_i, T_i, G_s, T_r, WUE, L_s, φ, A_max, k and R_ady of the cotton leaves. (4)Salt dust can significantly damage the physiological functions of the cotton leaves, resulting in a decrease in leaf chlorophyll and carotenoid content, and increasing cytoplasmic membrane permeability and malondialdehyde (MDA) content by increasing the soluble sugar and proline to adjust for the loss of the cell cytosol. This increases the activity of antioxidant enzymes to eliminate harmful materials, such as the intracellular reactive oxygen and MDA, thus reducing the damage caused by the salt dust and maintaining normal physiological functioning. Overall, this work found that the salt dust deposition was a problem for the crop and the salt dust could significantly influence the physiological and biochemical processes of the cotton leaves. This will eventually damage the leaves and reduce the cotton production, leading to agricultural economic loss. Therefore, attention should be paid to salt dust storms in the Ebinur Basin and efficient measures should be undertaken to protect the environment.     

1986—2019年新疆湖泊变化时空特征及趋势分析

干旱区湖泊是区域水资源系统的重要组成部分,不仅在维系区域生态系统平衡上发挥重要支撑作用,而且也对区域气候变化和人类活动具有重要的指示意义。基于Google Earth Engine(GEE)遥感云计算平台,以Landsat 5/7/8卫星遥感影像为主要数据源,分析了1986—2019年新疆维吾尔自治区湖泊数量以及面积变化的时空特征,并从气候要素变化、人类活动干扰等方面初步探讨了新疆湖泊变化的主要原因。结果表明：1986—2019年间,气温升高使得冰川积雪融水增加,新疆湖泊整体上呈现出扩张趋势。然而受人类活动的干扰程度以及地形海拔等因素,这种趋势存在显著的空间差异。全球变暖背景下,由于受到丰富稳定的雪冰融水的补给,受人为干扰较小的青藏高原北部地区湖泊呈现显著扩张。相反由于环天山地区强烈的人类活动以及冰川加速退缩影响,该区域湖泊面积持续高位波动状态。     

Absorption Circular Dichroism Induced by Contorted Electrical Oscillations in Rectangular Nanoholes

The chiroptical response of plasmonic chiral nanostructures can be tuned by combining different structures. In this paper, an L-shaped metal strip is introduced into a rectangular metal nanohole to generate absorption circular dichroism (ACD). The results of a finite-element method calculation show that ACD effects result from contorted electrical oscillations in the L-shaped strip. Additional calculations show that the ACD effects of the proposed metasurface depend strongly on the structure parameters. These findings provide not only a mechanism for enhancing chiroptical responses in planar structures but also a general strategy for the chiral manipulation of light and creation of chiroptical devices.