Pollution monitoring using the leaf-deposited particulates and magnetism of the leaves of 23 plant species in a semi-arid city, Northwest China.

We conducted a study of the leaf-deposited particles and magnetism of plant leaves in different functional areas (traffic areas, parks, and residential areas) in Lanzhou, China. The saturation isothermal remanent magnetization (SIRM) of the washed and unwashed leaves of 23 plant species (including evergreen shrubs, deciduous shrubs, deciduous liana species, and deciduous trees) at three sampling heights (0.5 m, 1.5 m, and 2.5 m) was measured. In addition, the mass of the leaf-deposited particles was measured using the elution-filtration method and the leaf morphological characteristics were determined by scanning electronic microscope (SEM) analysis. The results revealed significant differences in particle retention capacity among the 23 plant species, with evergreen shrub species at the heights of 0.5 m and 1.5 m having higher particle concentrations. Buxus sinica, Buxus megistophylla, Prunus cerasifera, and Ligustrum×vicaryi were the most effective plant species for accumulating particles. The SEM results showed that leaves with a relatively complex adaxial surface (such as deep grooves and protrusions) were more effective at accumulating particles. The SIRM of washed leaves, unwashed leaves, and leaf-deposited particles were significantly higher in traffic areas than in parks and residential areas. In addition, significant correlations were found between SIRM of unwashed leaves and leaf-deposited particles and the mass of leaf-deposited particles, and therefore the leaf magnetic properties effectively reflect levels of PM pollution under different environmental conditions. Overall, our results provide a valuable reference for the selection of plant species with high particle retention capacity that is suitable for urban greening and pollution mitigation.

Magnetic characteristics of Juniperus formosana needles along an urban street in Lanzhou, Northwest China: the variation of different season and orientation.

The magnetic properties of particulate matter (PM) deposited on the needles of Juniperus formosana along an urban street in Lanzhou city were measured to evaluate the variations of PM concentration in different seasons by varying distance from the road. The magnetism of PM deposited in this context was significantly higher in winter than in summer, which may reflect changes of atmospheric particle concentrations. Needle samples which were collected from the road-facing side exhibiting significantly stronger magnetism compared with those which were collected from the opposite side of the road, indicating the distance from pollution source to the needles as a factor controls the amount of PM. The results of this study show that the needles of Juniperus formosana are effective traps for PM and can therefore be used to monitor pollution fluxes in different seasons in an important urban context in NW China.

The influence of roadside trees on the diffusion of road traffic pollutants and their magnetic characteristics in a typical semi-arid urban area of Northwest China.

Leaf samples of Juniperus formosana were collected from an open road environment, in order to establish how particulate matter (PM) generated by vehicles was dispersed in both horizontal and vertical directions. Sampling was conducted at sites with trees of varying height and configuration adjacent to a major road in Lanzhou, Gansu Province, Northwest China. The concentration of remanence-bearing ferrimagnets in the leaf samples was estimated from measurements of Saturation Isothermal Remanent Magnetization (SIRM), while the weight of particles deposited on the leaves and their elemental composition were determined at different heights and in different directions relative to the road. The PM on the surface of needles was predominantly influenced by traffic emissions and by dust resuspension. Rows of roadside trees, as opposed to solitary trees, were more effective at intercepting PM and thus in filtering road traffic pollution. The results indicate that Juniperus formosana needles may be an effective bio-sensor for monitoring variations in the spatial diffusion of road pollutants.

[Magnetic Properties of Farmland Soils in Arid Regions in Northwest China and Their Environmental Implications].

In order to understand the feasibility of environmental magnetism methods in farmland soil pollution monitoring in the northwest arid areas of China, the environmental magnetic properties of 102 farmland soil samples from four typical agricultural regions, namely Linze county, Ganzhou district, Minle county, and Shandan county in Zhangye City were systematically analyzed. The results show that the main magnetic mineral of farmland soil samples is ferrimagnetic magnetite, and the main magnetic grain sizes are coarse-grained pseudo single domain (PSD) and multidomain (MD), mainly between 0.2-1 µm in equivalent diameter. The low frequency magnetic susceptibility (χlf) value of farmland soil samples ranged from 22.27×10-8 m3·kg-1 to 188.36×10-8 m3·kg-1, with the average value of 63.85×10-8 m3·kg-1. Overall, the magnetic mineral content of farmland soil samples was low, but it had large spatial variation. The spatial distribution of the magnetic parameters show that the magnetic mineral contents in Ganzhou district, Minle county, and Shandan county are higher than in Linze county, and three relatively high-value areas are present in central Ganzhou district, the southwest side of Minle county, and the west side of Shandan county. High magnetic value in central Ganzhou district is mainly controlled by human activities, such as industrial production, whereas the high magnetic values in the southwest side of Minle county and west side of Shandan county are more related to strong natural pedogenesis. Therefore, systematic comprehensive analysis of magnetic parameters can effectively distinguish and delimit the man-made pollution range in farmland soil and provide a basis for farmland soil pollution prevention and control.

[Magnetic Characteristics and Environmental Pollution Analysis of Street Dust in Different Functional Zones of Xi'an City].

Urban environmental pollution can be revealed by the magnetic characteristics of street dust. Environmental magnetic measurements were carried out for the 151 samples of street dust collected in different functional zones of Xi'an city. Magnetic susceptibility varied within the range between 169.5×10-8 m3·kg-1 and 977.48×10-8 m3·kg-1, and the χlf average value was 415.66×10-8 m3·kg-1,which was 10 times higher than that of the background value. Isothermal remanent magnetization varied within the range between 2005.31×10-5 A·m2·kg-1 and 10897.64×10-5 A·m2·kg-1, and the SIRM average value was 5105.99×10-5 A·m2·kg-1. The average value of frequency-dependent magnetic susceptibility was 1.30, which was extremely low. The SIRM curve was consistent with χlf curve. The results indicated a high concentration of magnetic minerals in street dust. The magnetic minerals were mainly low-coercivity ferrimagnetic (magnetite and maghemite) and anti-ferromagnetic minerals (hematite), which contributed to the magnetic susceptibility. The main domains of magnetic minerals were composed of multiple domain (MD) and pseudo-single domain (PSD) ferrimagnetic minerals demonstrating the pollution of environment. According to the spatial distribution of magnetic properties of street dust and the different functional zones of Xi'an city, seven districts (A, B, C, D, E, F and G areas) were divided, which were summarized as three pollution types:heavily polluted, moderately polluted and lightly polluted. In the ecological district of Baqiao (F area) which was heavily polluted, χlf, SIRM and soft values were all the highest in the seven areas, and the main pollution sources were industry and vehicle emission. χlf, SIRM and soft values were slightly higher in the high-tech industrial district (A area) and the central business and commerce district (B area), which was moderately polluted by industry and vehicle emission. However, the magnetic parameters were relatively low in the functional zones of education, tourism and culture (C, D, E and G area), demonstrating that these areas were only slightly polluted by vehicle emission.

[Pollution Characteristics and Source Apportionment of PM2.5, in Lanzhou City].

In order to understand the characteristics and sources of PM2.5 pollutant in Lanzhou City, two PM2.5 sampling sites were set up in Chengguan district and Xigu district, respectively. Samples were sampled during October (non-heating period) and December (heating period) 2013, and mass concentrations of PM2.5 and its 16 kinds of chemical components were analyzed. The results showed that the average mass concentration of PM2.5 during the sampling period was 129 µg · m⁻³. The sequence of mass concentrations of inorganic elements was: S > Ca > Fe > Al > Mg > Pb > Zn > Mn > Ti > Cu, while the mass concentrations of S, Ca, Fe, and Al, which were the major element compositions, exceeded 1 µg · m⁻³. The mass concentration of inorganic elements during heating period was higher than that during non-heating period, meanwhile, the mass concentration in Chengguan district was higher than that in Xigu district. The sequence of mass concentrations of water-soluble ions was: SO4²â» > NO3⁻ > NH4⁺ > Cl⁻ > K⁺ > Na⁺, while the mass concentrations of SO4²â», NO3⁻, NH4⁺, which were the main ion components, exceeded 10 µg · m⁻³. The mass concentration of water- soluble ions during heating period was higher than that during non-heating period, meanwhile, the mass concentration in Xigu district was higher than that in Chengguan district. The result of enrichment factor (EF) analysis showed that the EF values of Al, Ca, Mg and Ti were lower than 1, indicating the contribution of natural source, while the EF values of Cu, Pb, S and Zn were higher than 10, indicating the contribution of anthropogenic pollution. The result of principal component analysis showed that the sources of PM2.5 were mainly derived from traffic emission, biomass burning, soil and secondary particles.

[Spatial Distribution of Stable Isotope from the Lakes in Typical Temperate Glacier Region].

We focused mainly on the spatial variation and influencing factors of hydrogen and oxygen stable isotopes between water samples collected at the surface and different depths in the Lashi Lake in August, 2014. Hydrological supply characteristics of the lake in typical temperate glacier region were discussed. The results showed that the values of δ¹8O and δD in the Lashi Lake ranged from -12.98 per thousand to -8.16 per thousand with the mean of -9.75 per thousand and from -99.42 per thousand to -73.78 per thousand with the mean of -82.23 per thousand, respectively. There was a reversed spatial variation between δ¹8O and d. Relatively low values of δ¹8O with high values of d were found at the edge of the lake where the rivers drained into. Meanwhile, the values of d in the vertical profile varied little with depth, suggesting that the waters mixed sufficiently in the vertical direction. The d values increased at first and then decreased from east to west at different layers, but both increase and decrease exhibited different velocities, which were related to the river distribution, the locality of the lake and environmental conditions etc. River water and atmospheric precipitation were the main recharge sources of the Lashi Lake, and the melt-water of snow and ice might also be the supply resource. The δ¹8O values of lake water in glacier region decreased along the elevation (except for Lashi Lake), generally, this phenomenon was called "altitude effect". Moreover, high isotopic values of the lake water from non-glacier region were due to the evaporation effect.

[Spatial Distribution of Magnetic Properties of Street Dust in Baoji City and Its Implications of Environment].

Magnetic characteristics of street dust can reflect important information of environmental conditions. Environmental magnetic measurements were carried out on the samples of street dust in Baoji City. The results indicated a high concentration of magnetic minerals in street dust, dominated by multiple domain (MD) and pseudo-single domain (PSD) ferrimagnetic minerals which were mainly from the traffic and industrial pollution. According to the Spatial Distribution of Magnetic Properties of Street Dust, Baoji City was divided into six districts (A, B, C, D, E and F areas). In the A (Chuangxin road and Gaoxin road eight) and B (Dongfeng road and Maying road) areas, χlf, SIRM and soft values were the highest in the six areas and much higher than the average values and background values, indicating heavy pollution. The pollution sources were industry and vehicles. χlf, SIRM and soft values were relatively high in the C ( Huoju road and Yikang road) area, indicating moderate pollution. The pollution source was vehicles. However, the magnetic parameters were lower than the average values and background values in D (Jinger road and Renmin road), E (Qingjiang road and Jiangtan road) and F (Chencang road) area, suggesting mild pollution. The pollution was caused by vehicle emission.

[Magnetic Responses of Heavy Metals in Street Dust of Typical Mine-Based City, Northwest China].

Magnetic characteristics and heavy metal properties of 43 street dust samples collected from Baiyin City, northwest of China were systematically analyzed. The results revealed that the main magnetic minerals were low-coercivity magnetite and maghemite with coarse pseudo single domain (PSD) and multi-domain (MD) in magnetic grain size. Compared with the domestic comprehensive cities, low frequency magnetic susceptibility(χlf) value of street dust samples in Binyin varied from 43. 75 x 10(-8) m3.kg-1 to 1 340. 08 x 10(-8) m3.kg-1 with the average value of 245. 98 x 10(-8) m3.kg-1, the magnetic mineral content in street dust samples of Binyin was low relatively, hut it varied among distinct districts with industrial district was the highest and the stripe traffic area was more higher than those of other regions(commercial district, new district). Different functional zones of Baiyin had a single pollution source relatively. Additionally, the contribution to strong magnetic minerals was predominated by industrial pollution and the distribution of pollution degrees in Bainyin showed a significant spatial difference. Concentrations of heavy metals(Cu, Pb, Zn) were generally high in Baiyin street dust. The significantly positive correlation between magnetic parameters(χlf, χARM, SIRM, SOFT) and pollution load index(PLI) and their consistent spatial characteristics confirm that magnetic concentration parameters can effectively monitor urban heavy metals pollution and determine the bounds and areas of pollution, providing a valuable tool for further urban pollution control.

[Magnetic properties of topsoils in typical industrial belt along the Yellow River in arid regions in northwest China and their environmental significance].

We have carried out environmental magnetic investigation on topsoil samples of two industrial cities Wuhai and Shizuishan along the Yellow River in the arid regions in northwest China. The concentration, type, magnetic grain sizes of the magnetic minerals and the environmental significance were discussed. The results showed that the main magnetic grain sizes were multi-domain (MD) and pseudo single domain (PSD). The concentration and grain sizes of magnetic minerals showed differences in different functional zones. In industrial zone, the concentration was higher and the grain size was coarser, while there were obviously fewer and finer magnetic minerals in agricultural zone and raw coal zone. Environmental magnetic measurements were efficient to monitor pollution caused by burned fossil fuel, but were not sensitive to unburned fuel. X,, SIRM and SOFT were effective indicators to reflect urban soil pollution. Environmental magnetism method was found to be an important way to monitor and evaluate soil pollution in a city.

[Magnetic property of dustfall in a Northwest China valley city and its environmental implications].

Lanzhou is one of the seriously polluted cities in Northwest China. Dustfall samples collected in Lanzhou and the countryside Huanghuatan were studied using magnetic methods. The results reveal that the content of magnetic mineral in dustfall samples from Lanzhou is much higher than that of Huanghuatan. At the same time, it has a much higher lever in winter than that of other seasons. The main magnetic minerals in the dustfall from both places are magnetite, maghemite and hematite, and the main magnetic grain sizes in dustfall samples are mainly pseudo single-domain(PSD) and multi-domain(MD). Although the air in Lanzhou is polluted seriously, the air quality has been improved greatly during the past decades and controlled well in recent years. Compared with other cities, air pollution in Lanzhou is affected significantly by urban terrain. This research also reveals that environmental magnetism has become a more and more important method in air pollution study.

[Characteristics of heavy metal elements and their relationship with magnetic properties of river sediment from urban area in Lanzhou].

The contents of As, Co, Cr, Cu, Ni, Pb, V and Zn in the surface sediments from 8 rivers in urban area in Lanzhou were monitored by ecological risk which was assessed by the potential ecological Håkanson index, and the index of geoaccumulation (Igeo), sediment enrichment factor (R), and environmental magnetism. The results showed that: (1) the potential ecological risk of heavy metals of As, Co, Ni, V in surface sediments from 8 rivers were low, which belonged to low ecological risk. But the risk of heave metals Cr, Pb, Zn in surface sediments from Yuer river was high, which belonged to middle ecological risk, and in downstream of Yuer river, the element of Cu belonged to high ecological risk. (2) The rivers in Lanzhou could be divided into four groups according to the heavy mental pollution degree: first type, such as Paihong river, Shier river, Yuer river and Shuimo river, called downstream concentrate type; second type, such as Qili river, called upstream concentrate type; third type, such as Luoguo river and Dasha river, called less affected type; fourth type, Lanni river, which polluted heavily in up and downstream; (3) The correlation analysis between magnetic parameters and element contents show that the parameters which mainly reflect the concentration of the magnetic minerals (X, SIRM, Ms) have close association with Cr, Ni, Pb, Zn, Cu, So we can infer that the magnetic minerals in deposits samples mainly came from electroplating effluent, motor vehicle emission, and domestic sewage. SIRM/X shows a strong correlation with Cr, Ni, Pb, Zn, indicating the distribution of anthropogenic particulates. (4) The magnetic minerals(X, SIRM, Ms) have a strong correlation with the geoaccumulation (Igeo) than potential ecological risk index and enrichment factor (R). These results suggest a possible approach for source identification of magnetic material in pollution studies and the validity of using magnetic measurements to mapping the polluted area.

[Magnetic characters of river sediment of urban area in Lanzhou].

A total of 23 deposits samples were collected from 8 selected the river sediments in Lanzhou urban area as researching objects of magnetic property and organic matter measure. The results indicate that: (1) the magnetic property controlled by magnetite which is ferrimagnetic mineral, and anti-ferromagnetic component such as hematite and goethite; (2) the value of samples' magnetic parameters (such as: chi, SIRM, magnetic hysteresis loops and M-T curves) increased from upstream to downstream in Paihong River, Shier River and Yuer River, Shuimo River; decreased in Qili River and Lanni River; and contrasting above-mentioned, the value of samples' magnetic parameters were low in Luoguo River and Dasha River. Based on the variation of magnetic parameters, such as chiFD, chiARM, chiFD/Ms and chiARM/Ms, we divided the rivers into three groups according to the contribution originating from anthropogenic activities into spatial river sediments: first type, such as Paihong River, Shier River, Yuer River and Shuimo River, called downstream concentrate type; second type, such as Qili River and Lanni River, called upstream concentrate type; third type, such as Luoguo River and Dasha River, called less affected type. Bulk samples also demonstrate a strong linear positive correlation between magnetic parameters chiFD, chiARM and the content of organic matter, which reflected the content of superparamagnetic and single domain grains were nice proxy parameters of the content of organic matter of river sediments.

[Analysis of particulate pollution characteristics and its causes in Lanzhou, Northwest China].

Seasonal characteristics, annual variations and trend of PM10 and the causes of the PM10 long-term trend in Lanzhou were studied for the period of 2001-2007 using daily air pollution index (API) data and detrending technique. Results indicate that air quality in Lanzhou has been improved since 2001. The annual averaged PM10 concentration decreased from 236 microg x m(-3) in 2001 to 127 microg x m(-3) in 2007 and the number of days satisfying the Chinese Grade I and II air quality standard increased 2.3 times as 2001, but there still have 25% days exceeding the national Grade II air quality standard. Monthly mean PM10 concentration undergoes a seasonal change characterized by higher values in November, December and January to March. The maximum monthly average PM10 concentrations appear in December (271 microg x m(-3)) followed by March (245 microg x m(-3)) while it is low during summer months (May to October) with monthly average PM10 concentrations below 150 microg x m(-3). 61.2% of moderate pollution and 50.6% of serious pollution days occurred in winter and 67.4% of Grade I and II days occurred in summer and autumn. Analyses show that annual mean PM10 concentrations decreased at a rate of 12.6% over the past 7 years which correlates well with the reductions in anthropogenic dust emissions. The occurrence of blowing dust and floating dust can modulate the overall trend of PM10, which explains about 21% of the inter-annual variations of PM10 during 2001-2007. The changes of local meteorological conditions have little effect on the overall trend of PM10 concentrations. The improvement of air quality in Lanzhou is mainly due to the reduction of local emissions, with contributions from the variation of natural dust emissions due to annual variations of blowing and floating dust events. To further improvement of the air quality in Lanzhou, it is advisable to not only implement effective emission control strategies but also improve surrounding ecological environment.

[Correlations between leaf delta13C and physiological parameters of desert plant Reaumuria soongorica].

Reaumuria soongorica is a dominant species in the desert shrubbery vegetation in arid regions of northwestern China, playing an important role in the maintenance of the stability and continuity of desert ecosystem. In this paper, a total of 407 individuals in 21 natural populations of R. soongorica were selected from its main distribution areas to measure the leaf stable carbon isotope composition (delta13C) and nitrogen, phosphorus, potassium, water, proline and chlorophyll contents, with the correlations between the delta13C value and the test physiological parameters analyzed. The results showed that leaf delta13C value was significantly correlated with the contents of leaf potassium, water, and proline (P <0.001), and the correlation with leaf potassium content was most profound (r = 0.793), followed by that with leaf water content (r = -0.786), indicating that the variation of leaf delta13C value could reflect the nutritional status of the plants, and also, their water-deficient degree. The different distribution trends in leaf delta13C value of R. soongorica were likely caused by stomatal conductance, rather than by nutrient-related changes in photosynthetic efficiency under extremely low available water conditions.

[Magnetic characteristics of street dust in Lanzhou and its environmental significance].

Lanzhou has been one of the most seriously polluted cities in the world due to its special geographical location and weather conditions, which make it an ideal place for urban pollution studies. A set of environmental magnetic parameters (chi lf, chi fd%, chi ARM, chi HIRM, SOFT and back field IRM) of the street dust sampled in Lanzhou during spring and summer 2005 were analyzed. These samples were collected along a main street across the urban area and a mountain route from foot to the top. Results demonstrate that the main magnetic minerals in the street dust are magnetite, maghaemite and haematite with some paramagnetic minerals. Plots of Mrs/Ms vs. Bcr/Bc and chi fd% vs. chi ARM/SIRM indicate that the main grain size of magnetic minerals in the street dust are pseudo single domain (PSD). The results reveal that the Lanzhou city is more polluted in spring than in summer. The main pollution sources are anthropogenic activities (81.9%) and natural dust (18.1%), especially the former. The spatial distribution of pollution is controlled by the topography and weather conditions.