A New Geochemical Method for Determining the Sources of Atmospheric Particles: a Case Study from Gannan, Northeast China

atmosphere Article A New Geochemical Method for Determining the Sources of Atmospheric Particles: A Case Study from Gannan, Northeast China Chenmeng Yang 1,2, Guangyi Sun 1,2,* , Chao Zhang 1, Yupeng Chen 1, Wen Yang 3 and Lihai Shang 1,* 1 State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China; [email protected] (C.Y.); [email protected] (C.Z.); [email protected] (Y.C.) 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 Heilongjiang Institute of Geological Survey, Harbin 150036, China; [email protected] * Correspondence: [email protected] (G.S.); [email protected] (L.S.); Tel.: +86-13087859924 (G.S.); +86-13985519611 (L.S.) Received: 24 September 2019; Accepted: 16 October 2019; Published: 20 October 2019 Abstract: The geochemical characteristics of atmospheric deposition can help trace the origin and assess the impacts of pollutants. Northeast China has always been a region seriously affected by sandstorms. This study aims to explain the potential source of sandstorms in Gannan County, Heilongjiang Provence, by collecting dust and analyzing geochemistry in one year where there is no significant industrial or anthropogenic pollution. Input fluxes of deposition show that Zn and Mn were more prevalent (36.7 g hm 2 a 1 and 77.93 g hm 2 a 1, respectively) than other elements. · − · − · − · − The geochemical composition of atmospheric deposition samples from 17 collection points in Gannan County were determined with regard to 20 elements including nine heavy metals, two metalloids, three nonmetallic elements, a transition metal, and five other major elements. The discriminate function (DF) and chemical index of alteration (CIA) indices indicate that Gannan County (agricultural production area) and Harbin (densely inhabited district) have similar geochemical characteristics of dry deposition. The integration of Na/Al and Ca/Mg ratios with an air mass back-trajectories model shows effects from Russian dust sources (36.6%) and from the northwest desert of China (13.3%). The results will assist in developing strategies for reducing dry deposition pollution inputs to agricultural soils in the area and will effectively target policies to protect soils from long-term contaminant accumulation. Keywords: dry deposition; trace elements; source identification; long-term transport 1. Introduction Arid and semiarid regions, which make up a third of the Earth’s landmass, are major sources of dust particles which are produced by the disintegration of aggregates following creeping and saltation of larger soil particles [1,2]. The increase in the number of sandstorms is due to the intensification of desertification, which in turn is encouraged by sandstorm events exacerbating drought conditions in semiarid areas. The dust is mainly composed of iron oxide minerals (such as hematite and goethite), carbonate minerals (such as calcite and dolomite), and quartz and clay minerals (such as kaolinite, illite, and montmorillonite) [3–5]. A broad variety of chemical species, both organic and inorganic, have been discovered in atmospheric deposition [6]. Trace metals, which originate from different anthropogenic and natural sources [7], are constantly released into the air and constitute the major components of dry deposition particles which impact adversely on the ecological environment [8] Atmosphere 2019, 10, 632; doi:10.3390/atmos10100632 www.mdpi.com/journal/atmosphere Atmosphere 2019, 10, 632 2 of 20 and in turn increase the risk to human health [9]. Natural sources such as weathered materials, soils, and crustal minerals, and man-made sources such as vehicle emissions [10–12], residential fossil-fuel burning, non-ferrous metal processing, industrial emissions, and construction operations [6,13–15] have made major contributions to the concentrations of some elements in atmospheric dust [16,17]. Dust can influence radiation of light, global biogeochemical cycles, environmental pollution, and human health risks, and can also stimulate primary productivity [18,19]. Therefore, exploring deposition sources is an important research field to identify and control air pollution. Crucial factors determining the deposition rate include the chemical characteristics of the depositional environment, types and distance of emission sources, and some meteorological conditions [20,21]. In particular, information regarding the spatiotemporal variability of the dust rate provides a powerful framework for evaluating deposition characteristics in a given location [19,21,22]. Dust transmission plays an important role in Earth’s systems [1–6]. Aeolian sand is a major driving force in the climate system through its influence on light scattering/absorption, cloud properties and the ice and snow albedo [23–27]. East Asian deserts are the second largest source of dust [19,28]. The Taklimakan desert and the deserts of Inner Mongolia (such as Badain Jaran and Tengger) are the dominant dust sources for both the subarctic Northwestern Pacific, Greenland and even North America [25,29] Although system model research studies of dry deposition have been conducted [1,2,11,25,30–34], most of the investigations have been limited by the multiple solutions of the algorithms, which analyze the source information based on the pollution transmission of meteorological conditions or lack information on the geological compositions of particles, which could provide accurate source information [35–38]. In addition, research on the isotopes of dry deposition particles has revealed significant new information. For example, due to the unstable environmental conditions experienced by atmospheric particles during long-distance transmission, it is unknown whether the isotopic characteristic signals of atmospheric particles fluctuate or differ [35]. The primary and trace elements of minerals in atmospheric particulates experience less fluctuation than isotopes and rare earth elements (REEs) as a whole during their transmission in a relatively closed condition. Geochemical information of dry deposition with specifically quantitative source estimation has rarely been used in previous studies [39–42]. Detailed investigations of dry deposition in remote rural areas of China are not available in the literature; most Chinese investigations have concentrated on metropolis or urban areas. In this study, measurements of geochemical composition were conducted semi-quantitatively and traced the sources of dry deposition in the remote areas of Northeast China areas by pioneering geochemical methods combined with back-trajectory calculation analysis. This not only has important ecological and environmental significance for ascertaining the scale and source of the dry deposition at the Songnen Plain of the Northeast China, but also provides a scientific basis for regional sand control work. Moreover, the application of discriminating geochemical ratios combined with the tracer method provides a novel path for the study of dry deposition. 2. Experiments 2.1. Study Area and Sample Collection Gannan County (Figure1) is an important agricultural area located in Northwest Songnen Plain in the eastern part of the Greater Hinggan Mountains, Heilongjiang Province, Northeastern China (47◦400–48◦000, 123◦150–124◦000). The study area primarily encompasses Yinhe Town and Shuanhe Town, with an area of 600 km2. The climate in Songnen Plain is a semiarid continental climate where the annual mean temperature varies greatly and sandstorms are infrequent. The monthly mean temperatures range from 22.4 C in July to 18.4 C in January with a mean annual temperature of ◦ − ◦ 3.5 ◦C. The rainy season occurs during the summer and accounts for approximately 60% of the mean annual rainfall (462 mm). Rice and corn are regarded as staple crops in this area where agricultural space dry farming has become the main method, and irrigation is used as an auxiliary method. Atmosphere 2019, 10, 632 3 of 20 Atmosphere 2019, 10, x FOR PEER REVIEW FigureFigure 1. 1. SamplingSampling sites sites and the and schematic the schematic diagram diagram of the different of the sources different of sourcesatmospheric of atmospheric deposition indeposition the Gannan in theCounty Gannan area, County Northeastern area, NortheasternChina (N andChina E refer (N to andnorth E latitude refer to and north east latitude longitude and respectively).east longitude respectively). UnlikeUnlike wet wet deposition deposition [33], [33], there there is is no no common technique technique for for collecting dry dry deposition accuratelyaccurately [33]. [33]. Although Although some some researchers researchers have have pursued pursued more more suitable suitable sampling sampling techniques techniques [43,44], [43,44], nono method method has has yet yet been been established established as as a a standard standard because because both both the the collector collector geometry geometry and and the the characteristicscharacteristics of of the the collection collection container container have have a a strong impact on the results. InIn order toto estimateestimate the the processes processes influencing influencing long-term long-term dry dry deposition deposition changes changes in the in studythe study area, area,atmospheric atmospheric dry deposition dry deposition samples samples were collectedwere collected from 17from sampling 17 sampli pointsng frompoints Gannan from Gannan County Countyagricultural agricultural land for land one yearfor one (2013). year Our

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