scholarly journals Global Observations and Modeling of Atmosphere-Surface Exchange of Elemental Mercury – A Critical Review

2016 ◽  
Author(s):  
W. Zhu ◽  
C.-J. Lin ◽  
X. Wang ◽  
J. Sommar ◽  
X. W. Fu ◽  
...  
Keyword(s):  
Global Analysis ◽  
Large Data ◽  
Elemental Mercury ◽  
Physicochemical Process ◽  
Anthropogenic Sources ◽  
Flux Chamber ◽  
Surface Exchange ◽  
Environmental Media ◽  
Flux Quantification ◽  
Spatio Temporal

Abstract. Reliable quantification of air-surfaces flux of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoting to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in past three decades. However, large uncertainty remains due to the complexity of Hg0 bi-directional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a comprehensive review on the state of science in the atmosphere-surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air-surfaces Hg exchange, and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence, presence of reactants (e.g., O3, radicals, etc.) that drives the physicochemical process of Hg in the media where Hg0 exchange occurs. However, effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. In this study, we compile an up-to-date global observational flux database and discuss the implication of flux data on global Hg budget. Mean Hg0 flux obtained by micrometeorological measurement did not appear to be significantly greater than the flux measured by dynamic flux chamber methods over unpolluted surfaces (p=0.16, one-tailed, Mann-Whitney U test). The spatio-temporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East Asia are comparatively larger in magnitude than the rest of the world, suggesting substantial reemission of previously deposited mercury from anthropogenic sources. Hg0 exchange over pristine surfaces (e.g., background soil and water) and vegetation need better constrains for global analysis of atmospheric Hg budget. The existing knowledge gap and the associated research needs for future measurements and modeling efforts for the air-surface exchange of Hg0 are discussed.

scholarly journals Global observations and modeling of atmosphere–surface exchange of elemental mercury: a critical review

2016 ◽  
Vol 16 (7) ◽  
pp. 4451-4480 ◽  
Author(s):  
Wei Zhu ◽  
Che-Jen Lin ◽  
Xun Wang ◽  
Jonas Sommar ◽  
Xuewu Fu ◽  
...  
Keyword(s):  
Critical Review ◽  
Large Data ◽  
Elemental Mercury ◽  
Surface Fluxes ◽  
Anthropogenic Sources ◽  
Flux Chamber ◽  
Surface Exchange ◽  
Environmental Media ◽  
Flux Quantification ◽  
Global Biogeochemical Cycles

Abstract. Reliable quantification of air–surface fluxes of elemental Hg vapor (Hg0) is crucial for understanding mercury (Hg) global biogeochemical cycles. There have been extensive measurements and modeling efforts devoted to estimating the exchange fluxes between the atmosphere and various surfaces (e.g., soil, canopies, water, snow, etc.) in the past three decades. However, large uncertainties remain due to the complexity of Hg0 bidirectional exchange, limitations of flux quantification techniques and challenges in model parameterization. In this study, we provide a critical review on the state of science in the atmosphere–surface exchange of Hg0. Specifically, the advancement of flux quantification techniques, mechanisms in driving the air–surface Hg exchange and modeling efforts are presented. Due to the semi-volatile nature of Hg0 and redox transformation of Hg in environmental media, Hg deposition and evasion are influenced by multiple environmental variables including seasonality, vegetative coverage and its life cycle, temperature, light, moisture, atmospheric turbulence and the presence of reactants (e.g., O3, radicals, etc.). However, the effects of these processes on flux have not been fundamentally and quantitatively determined, which limits the accuracy of flux modeling. We compile an up-to-date global observational flux database and discuss the implication of flux data on the global Hg budget. Mean Hg0 fluxes obtained by micrometeorological measurements do not appear to be significantly greater than the fluxes measured by dynamic flux chamber methods over unpolluted surfaces (p = 0.16, one-tailed, Mann–Whitney U test). The spatiotemporal coverage of existing Hg0 flux measurements is highly heterogeneous with large data gaps existing in multiple continents (Africa, South Asia, Middle East, South America and Australia). The magnitude of the evasion flux is strongly enhanced by human activities, particularly at contaminated sites. Hg0 flux observations in East Asia are comparatively larger in magnitude than the rest of the world, suggesting substantial re-emission of previously deposited mercury from anthropogenic sources. The Hg0 exchange over pristine surfaces (e.g., background soil and water) and vegetation needs better constraints for global analyses of the atmospheric Hg budget. The existing knowledge gap and the associated research needs for future measurements and modeling efforts for the air–surface exchange of Hg0 are discussed.

scholarly journals Mercury vapor air–surface exchange measured by collocated micrometeorological and enclosure methods – Part I: Data comparability and method characteristics

2015 ◽  
Vol 15 (2) ◽  
pp. 685-702 ◽  
Author(s):  
W. Zhu ◽  
J. Sommar ◽  
C.-J. Lin ◽  
X. Feng
Keyword(s):  
Temporal Variability ◽  
Temporal Trends ◽  
Elemental Mercury ◽  
Bowen Ratio ◽  
Mercury Vapor ◽  
Bare Soil ◽  
Agricultural Field ◽  
Flux Chamber ◽  
Surface Exchange ◽  
Flux Quantification

Abstract. Reliable quantification of air–biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding the global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micrometeorological (MM) and dynamic flux chamber (DFC) measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and correlation with environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much more gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R>0.8, p<0.05), but the correlation between DFC and MM fluxes were from weak to moderate (R=0.1–0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (<10% difference). This suggests that incorporating an atmospheric turbulence property such as friction velocity for correcting the DFC-measured flux effectively bridged the gap between the Hg0 fluxes measured by enclosure and MM techniques. Cumulated flux measured by REA was ~60% higher than the gradient-based fluxes. Environmental factors have different degrees of impacts on the fluxes observed by different techniques, possibly caused by the underlying assumptions specific to each individual method. Recommendations regarding the application of flux quantification methods were made based on the data obtained in this study.

scholarly journals Air/Surface Exchange of Gaseous Elemental Mercury at Different Landscapes in Mississippi, USA

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 538 ◽  
Author(s):  
James Cizdziel ◽  
Yi Jiang ◽  
Divya Nallamothu ◽  
J. Brewer ◽  
Zhiqiang Gao
Keyword(s):  
Forest Floor ◽  
Agricultural Soils ◽  
Elemental Mercury ◽  
Ecological Impacts ◽  
Wetland Soil ◽  
Flux Chamber ◽  
Surface Exchange ◽  
Gaseous Elemental Mercury ◽  
Emission Fluxes ◽  
Mesocosm Experiments

Mercury (Hg) is a global pollutant with human health and ecological impacts. Gas exchange between terrestrial surfaces and the atmosphere is an important route for Hg to enter and exit ecosystems. Here, we used a dynamic flux chamber to measure gaseous elemental Hg (GEM) exchange over different landscapes in Mississippi, including in situ measurements for a wetland (soil and water), forest floor, pond, mowed field and grass-covered lawn, as well as mesocosm experiments for three different agricultural soils. Fluxes were measured during both the summer and winter. Mean ambient levels of GEM ranged between 0.93–1.57 ng m−3. GEM emission fluxes varied diurnally with higher daytime fluxes, driven primarily by solar radiation, and lower and more stable nighttime fluxes, dependent mostly on temperature. GEM fluxes (ng m−2 h−1) were seasonally dependent with net emission during the summer (mean 2.15, range 0.32 to 4.92) and net deposition during the winter (−0.12, range −0.32 to 0.12). Total Hg concentrations in the soil ranged from 17.1 ng g−1 to 127 ng g−1 but were not a good predictor of GEM emissions. GEM flux and soil temperature were correlated over the forest floor, and the corresponding activation energy for Hg emission was ~31 kcal mol−1 using the Arrhenius equation. There were significant differences in GEM fluxes between the habitats with emissions for grass > wetland soil > mowed field > pond > wetland water ≈ forest ≈ agriculture soils. Overall, we demonstrate that these diverse landscapes serve as both sources and sinks for airborne Hg depending on the season and meteorological factors.

scholarly journals Circumpolar transport and air-surface exchange of atmospheric mercury at Ny-Ålesund (79° N), Svalbard, spring 2002

2007 ◽  
Vol 7 (1) ◽  
pp. 151-166 ◽  
Author(s):  
J. Sommar ◽  
I. Wängberg ◽  
T. Berg ◽  
K. Gårdfeldt ◽  
J. Munthe ◽  
...  
Keyword(s):  
Sea Level ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Species ◽  
Research Station ◽  
Flux Chamber ◽  
Vertical Column ◽  
Surface Exchange ◽  
Lower Altitude ◽  
Gaseous Mercury

Abstract. Mercury in different environmental compartments has been measured at Ny-Ålesund (78°54' N, 11°53' E) during an intensive campaign, 17 April to 14 May 2002. Time-resolved speciated determination of mercury in the atmosphere and snow was conducted at the Norwegian research station at the Zeppelin mountain, 474 m above the sea level, and at the Italian research facility Dirigibile Italia, 12 m above the sea level. Total Gaseous Mercury (TGM) was present in the range <0.1 to 2.2 ng m−3 during the campaign. Three mercury depletion events, identified as periods with decreased TGM concentrations, were observed. At the lower altitude, TGM concentrations following such events were found to exhibit both higher magnitude and larger variability in comparison to results from the Zeppelin station. Oxidised mercury species in air and fall-out with snow as well as mercury attached to particles were also measured and their concentrations were found to be anti-correlated with TGM in air. concentrations of total Hg in snow (Hg-tot) showed a large (~15×) increase in response to Gaseous Elemental Mercury Depletion Events (GEMDEs, range 1.5–76.5 ng L−1). Solid evidence for photo-stimulated emissions of Hg0(g) from the snow pack in conjunction to depletion events were obtained from gradient measurements as well as from flux chamber measurements. Steep diurnal concentration variations of Hg0(aq) in surface seawater were also found to concur with changing solar radiation. The concentration of Hg0(aq) in seawater was found to be in the range 12.2–70.4 pg L−1, which corresponds to supersaturation. Hence, the seawater surface constituted a source emitting elemental mercury. The concentrations of RGM (reactive gaseous mercury), Hg-p (particulate mercury), and BrO column densities (detected by DOAS) were very low except for a few individual samples during the major Hg0 depletion event. BrO vertical column densities obtained by the remote satellite ESR-2 and trajectory analysis indicate that the air masses exhibiting low Hg0 concentrations originated from areas with high BrO densities.

scholarly journals Air-surface exchange measurements of gaseous elemental mercury over naturally enriched and background terrestrial landscapes in Australia

2013 ◽  
Vol 13 (10) ◽  
pp. 5325-5336 ◽  
Author(s):  
G. C. Edwards ◽  
D. A. Howard
Keyword(s):  
Environmental Parameters ◽  
Elemental Mercury ◽  
Field Studies ◽  
Bare Soil ◽  
Climatic Conditions ◽  
Flux Chamber ◽  
Land Use Patterns ◽  
Surface Exchange ◽  
Gaseous Elemental Mercury ◽  
Temperature Radiation

Abstract. This paper presents the first gaseous elemental mercury (GEM) air-surface exchange measurements obtained over naturally enriched and background (<0.1 μg g−1 Hg) terrestrial landscapes in Australia. Two pilot field studies were carried out during the Australian autumn and winter periods at a copper-gold-cobalt-arsenic-mercury mineral field near Pulganbar, NSW. GEM fluxes using a dynamic flux chamber approach were measured, along with controlling environmental parameters over three naturally enriched and three background substrates. The enriched sites results showed net emission to the atmosphere and a strong correlation between flux and substrate Hg concentration, with average fluxes ranging from 14 ± 1 ng m−2 h−1 to 113 ± 6 ng m−2 h−1. Measurements at background sites showed both emission and deposition. The average Hg flux from all background sites showed an overall net emission of 0.36 ± 0.06 ng m−2 h−1. Fluxes show strong relationships with temperature, radiation, and substrate parameters. A compensation point of 2.48, representative of bare soils was determined. For periods of deposition, dry deposition velocities ranged from 0.00025 cm s−1 to 0.0083 cm s−1 with an average of 0.0041 ± 0.00018 cm s−1, representing bare soil, nighttime conditions. Comparison of the Australian data to North American data suggests the need for Australian-specific mercury air-surface exchange data representative of Australia's unique climatic conditions, vegetation types, land use patterns and soils.

scholarly journals Circumpolar transport and air-surface exchange of atmospheric mercury at Ny-Ålesund (79° N), Svalbard, spring 2002

2004 ◽  
Vol 4 (2) ◽  
pp. 1727-1771 ◽  
Author(s):  
J. Sommar ◽  
I. Wängberg ◽  
T. Berg ◽  
K. Gårdfeldt ◽  
J. Munthe ◽  
...  
Keyword(s):  
Sea Level ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Mercury Species ◽  
Research Station ◽  
Flux Chamber ◽  
Vertical Column ◽  
Surface Exchange ◽  
Lower Altitude ◽  
Gaseous Mercury

Abstract. Mercury in different environmental compartments has been measured at Ny-Ålesund (78°54′ N, 11°53′ E) during an intensive campaign, 17 April to 14 May 2002. Time-resolved speciated determination of mercury in the atmosphere and snow was conducted at the Norwegian research station at the Zeppelin mountain, 474 m above the sea level, and at the Italian research facility Dirigibile Italia, 12 m above the sea level. Total Gaseous Mercury (TGM) was present in the range <0.1 to 2.2 ng m−3 during the campaign. Three mercury depletion events, identified as periods with decreased TGM concentrations, were observed. At the lower altitude, TGM concentrations following such events were found to exhibit both higher magnitude and larger variability in comparison to results from the Zeppelin station. Oxidised mercury species in air and fall-out with snow as well as mercury attached to particles were also measured and their concentrations were found to be anti-correlated with TGM in air. The strongest modulation was observed for total mercury concentration (Hg-tot) in snow (range 1.5–76.5 ng L−1). Solid evidence for photo-stimulated emissions of Hg0(g) from the snow pack in conjunction to depletion events were obtained from gradient measurements as well as from flux chamber measurements. Steep diurnal concentration variations of Hg0(aq) in surface seawater were also found to concur with changing solar radiation. The concentration of Hg0(aq) in seawater was found to be in the range 12.2–70.4 pg L−1, which corresponds to supersaturation. Hence, the seawater surface constituted a source emitting elemental mercury. The concentrations of the transient mercury forms RGM (Reactive Gaseous Mercury) and PM (Particulate Mercury) respectively and BrO column densities detected using a zenith and off-axis sky viewing DOAS instrument were very low except for a few individual samples during the major depletion event. An evaluation of trajectories for selected events and comparisons with BrO vertical column densities obtained by the GOME (Global Ozone Monitoring Experiment) instrument aboard the earth remote sensing satellite ESR-2 indicates that the air masses exhibiting low Hg0 concentrations originated from areas with high BrO densities. It was concluded that the observed depletion events at Ny-Ålesund were a results of transport from areas with high photochemical activity around the polar region.

scholarly journals Air-surface exchange measurements of gaseous elemental mercury over naturally enriched and background terrestrial landscapes in Australia

2012 ◽  
Vol 12 (10) ◽  
pp. 27927-27954
Author(s):  
G. C. Edwards ◽  
D. A. Howard
Keyword(s):  
Environmental Parameters ◽  
Elemental Mercury ◽  
Field Studies ◽  
Climatic Conditions ◽  
Flux Chamber ◽  
Land Use Patterns ◽  
Surface Exchange ◽  
Gaseous Elemental Mercury ◽  
Copper Gold ◽  
Temperature Radiation

Abstract. This paper presents the first gaseous elemental mercury (GEM) air-surface exchange measurements obtained over naturally enriched and background (< 0.1 μg g−1 Hg) terrestrial landscapes in Australia. Two pilot field studies were carried out during the Australian autumn and winter periods at a copper-gold-cobalt-arsenic-mercury mineral field near Pulganbar, NSW. GEM fluxes using a dynamic flux chamber approach were measured, along with controlling environmental parameters over three naturally enriched and three background substrates. The enriched sites results showed net emission to the atmosphere and a strong correlation between flux and substrate Hg concentration, with average fluxes ranging from 14 ± 1 ng m−2 h−1 to 113 ± 6 ng m−2 h−1. Measurements at background sites showed both emission and deposition. The average Hg flux from all background sites showed an overall net emission of 0.36 ± 0.06 ng m−2 h−1. Fluxes show strong relationships with temperature, radiation, and substrate parameters. A compensation point of 2.48, representative of bare soils was determined. Comparison of the Australian data to North American data confirmed the need for Australian specific mercury air-surface exchange data representative of Australia's unique climatic conditions, vegetation types, land use patterns, and soils.

scholarly journals Air–surface exchange of Hg<sup>0</sup> measured by collocated micrometeorological and enclosure methods – Part 1: Data comparability and method characteristics

2014 ◽  
Vol 14 (16) ◽  
pp. 22273-22319
Author(s):  
W. Zhu ◽  
J. Sommar ◽  
C.-J. Lin ◽  
X. Feng
Keyword(s):  
Temporal Variability ◽  
Temporal Trends ◽  
Elemental Mercury ◽  
Bowen Ratio ◽  
Mercury Vapor ◽  
Bare Soil ◽  
Agricultural Field ◽  
Surface Exchange ◽  
Flux Quantification ◽  
The Difference

Abstract. Reliable quantification of air-biosphere exchange flux of elemental mercury vapor (Hg0) is crucial for understanding global biogeochemical cycle of mercury. However, there has not been a standard analytical protocol for flux quantification, and little attention has been devoted to characterize the temporal variability and comparability of fluxes measured by different methods. In this study, we deployed a collocated set of micro-meteorological (MM) and enclosure measurement systems to quantify Hg0 flux over bare soil and low standing crop in an agricultural field. The techniques include relaxed eddy accumulation (REA), modified Bowen-ratio (MBR), aerodynamic gradient (AGM) as well as dynamic flux chambers of traditional (TDFC) and novel (NDFC) designs. The five systems and their measured fluxes were cross-examined with respect to magnitude, temporal trend and sensitivity to environmental variables. Fluxes measured by the MM and DFC methods showed distinct temporal trends. The former exhibited a highly dynamic temporal variability while the latter had much gradual temporal features. The diurnal characteristics reflected the difference in the fundamental processes driving the measurements. The correlations between NDFC and TDFC fluxes and between MBR and AGM fluxes were significant (R > 0.8, p < 0.05), but the correlation between DFC and MM instantaneous fluxes were from weak to moderate (R = 0.1–0.5). Statistical analysis indicated that the median of turbulent fluxes estimated by the three independent MM-techniques were not significantly different. Cumulative flux measured by TDFC is considerably lower (42% of AGM and 31% of MBR fluxes) while those measured by NDFC, AGM and MBR were similar (< 10% difference). This implicates that the NDFC technique, which accounts for internal friction velocity, effectively bridged the gap in measured Hg0 flux compared to MM techniques. Cumulated flux measured by REA was ~60% higher than the gradient-based fluxes. Environmental factors have different degrees of impacts on the fluxes observed by different techniques, possibly caused by the underlying assumptions specific to each individual method. Recommendations regarding the application of flux quantification methods were made based on the data obtained in this study.

scholarly journals Emission-dominated gas exchange of elemental mercury vapor over natural surfaces in China

2016 ◽  
Author(s):  
Xun Wang ◽  
Che-Jen Lin ◽  
Wei Yuan ◽  
Jonas Sommar ◽  
Wei Zhu ◽  
...  
Keyword(s):  
Forest Ecosystems ◽  
Agricultural Land ◽  
Mechanistic Model ◽  
Mainland China ◽  
Elemental Mercury ◽  
Mercury Vapor ◽  
Model Verification ◽  
Surface Exchange ◽  
Field Shift ◽  
Elemental Mercury Vapor

Abstract. Mercury (Hg) emission from natural surfaces plays an important role in global Hg cycling. The present estimate of global natural emission has large uncertainty and remains unverified against field data, particularly for terrestrial surfaces. In this study, a mechanistic model is developed for estimating the emission of elemental mercury vapor (Hg0) from natural surfaces in China. The development implements recent advancements in the understanding of air-soil and air-foliage exchange of Hg0 and redox chemistry in soil and on surfaces, incorporates the effects of soil characteristics and landuse changes by agricultural activities, and is examined through a systematic set of sensitivity simulations. Using meteorology simulated by the Weather Research and Forecasting Model (WRF version 3.7), the exchange of Hg0 between the atmosphere and natural surfaces in Mainland China is estimated to be 465.1 Mg yr−1, including 565.5 Mg yr−1 of emission from soils, 9.0 Mg yr−1 of emission from water body, and 100.4 Mg yr−1 uptake by vegetation. The air-surface exchange is strongly dependent on the landuse and meteorology, with 9 % of net emission from forest ecosystems, 50 % from shrubland, and savanna and grassland, 33 % from cropland, and 8 % from other landuses. Given the large agricultural land area in China, farming activities play an important role on the air-surface exchange in farmland. Particularly, rice field shift from a net sink (3.3 Mg uptake) during April to October (rice planting) to a net source when the farmland is not flooded (November-March). Summing up emissions from each landuse, more than half of the total emission occurs in summer (51 %), followed by spring (28 %), autumn (13 %) and winter (8 %). Model verification is accomplished using observational data of air-soil/air-water fluxes and Hg deposition through litterfall for forest ecosystems in China and Monte Carlo simulations. In contrast to the earlier estimate by Shetty et al. (2008) that reported large emission from vegetative surfaces using an evapotranspiration approach, the estimate in this study shows natural emissions are primarily from grassland and dry cropland. Such an emission pattern may alter the current understanding of Hg emission outflow from China as reported by Lin et al. (2010b) because of a substantial natural Hg emission occurs in West China.

scholarly journals AN EFFICIENT CLUSTERING METHOD FOR DBSCAN GEOGRAPHIC SPATIO-TEMPORAL LARGE DATA WITH IMPROVED PARAMETER OPTIMIZATION

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 581-584
Author(s):  
J. W. Li ◽  
X. Q. Han ◽  
J. W. Jiang ◽  
Y. Hu ◽  
L. Liu
Keyword(s):  
Parameter Optimization ◽  
Clustering Algorithm ◽  
Optimal Solution ◽  
Large Data ◽  
Parameter Selection ◽  
Physical Analysis ◽  
Clustering Method ◽  
K Value ◽  
Dbscan Clustering ◽  
Spatio Temporal

Abstract. How to establish an effective method of large data analysis of geographic space-time and quickly and accurately find the hidden value behind geographic information has become a current research focus. Researchers have found that clustering analysis methods in data mining field can well mine knowledge and information hidden in complex and massive spatio-temporal data, and density-based clustering is one of the most important clustering methods.However, the traditional DBSCAN clustering algorithm has some drawbacks which are difficult to overcome in parameter selection. For example, the two important parameters of Eps neighborhood and MinPts density need to be set artificially. If the clustering results are reasonable, the more suitable parameters can not be selected according to the guiding principles of parameter setting of traditional DBSCAN clustering algorithm. It can not produce accurate clustering results.To solve the problem of misclassification and density sparsity caused by unreasonable parameter selection in DBSCAN clustering algorithm. In this paper, a DBSCAN-based data efficient density clustering method with improved parameter optimization is proposed. Its evaluation index function (Optimal Distance) is obtained by cycling k-clustering in turn, and the optimal solution is selected. The optimal k-value in k-clustering is used to cluster samples. Through mathematical and physical analysis, we can determine the appropriate parameters of Eps and MinPts. Finally, we can get clustering results by DBSCAN clustering. Experiments show that this method can select parameters reasonably for DBSCAN clustering, which proves the superiority of the method described in this paper.

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