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Scientometrics (2014) 98:511–529 DOI 10.1007/s11192-013-1065-x

Global trends in sediment-related research in earth science during 1992–2011: a bibliometric analysis Beibei Niu • Song Hong • Jiefei Yuan • Sha Peng • Zhen Wang Xu Zhang

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Received: 19 January 2013 / Published online: 22 June 2013 Ó Akade´miai Kiado´, Budapest, Hungary 2013

Abstract An effective bibliometric analysis based on the Science Citation IndexExpanded database was conducted to evaluate earth science sediment-related research from different perspectives from 1992 to 2011. The geographical influences of the authors were subsequently visualized. Sediment-related research experienced notable growth in the past two decades. Multidisciplinary geosciences and environmental sciences were the two major categories, and Environmental Science and Technology was the most active journal. Damste´ JSS and Schouten S were the two most prolific authors with the most high-quality articles and the greatest geographic influences. The major spatial clusters of authors overlapped quite well with regions with high economic growth in the USA, Western Europe, and Eastern Asia. The USA was the largest contributor in global sediment research with the most independent and collaborative papers, and the dominance of the USA was also confirmed in the national collaboration network. National academic output was positively associated with its economic capability. The Chinese Academy of Sciences, the US Geological Survey and the Russian Academy of Sciences were the three major contributing institutions. A keywords analysis determined that ‘‘evolution’’, ‘‘water’’, ‘‘soil(s)’’, and ‘‘model’’ were consistent hotspots in sediment research. Several keywords such as ‘‘organic-matter’’, ‘‘Holocene’’, ‘‘dynamics’’, ‘‘erosion’’, ‘‘sediment transport’’, ‘‘climate’’, and ‘‘heavy-metal’’ received dramatically increased attention during the study period. Through co-word analysis, significant differences were observed between environmental and multidisciplinary geosciences in terms of the most frequently used keywords, and the prevalent research topic patterns were ascertained. Keywords Sediment Bibliometrics SCI-Expanded Geographical impact factor (GIF) Co-word analysis

B. Niu S. Hong (&) J. Yuan S. Peng Z. Wang X. Zhang School of Resource and Environmental Science, Wuhan University, Wuhan 430079, People’s Republic of China e-mail: [email protected]

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Introduction Sediments and their associated processes play an important role in global biogeochemical cycles. Numerous studies have been carried out on the various aspects of sediment-related research in earth science, such as stratigraphy, sediment dynamics and toxicology (Long et al. 1995; Govindaraju et al. 1997; van Beelen and Doelman 1997; Grotzinger et al. 2005; Marttila and Klove 2010). However, a comprehensive statistical review of the global sediment-related research in earth science has not been conducted to date (Elfrink and Baldock 2002; Holland and Elmore 2008). Bibliometrics refers to a research methodology that utilizes quantitative analysis and statistics to describe the research trends of various research fields (Hsieh et al. 2004; Chen et al. 2005; Ho 2007). Bibliometric methods have been applied to assess the scientific outputs or research patterns of authors, journals, countries, and institutes and to identify and quantify international cooperation (Glanzel et al. 1999; van Raan 1999; Chiu and Ho 2007; Ho et al. 2010; Abramo et al. 2011). Whereas conventional bibliometric methods focus on citation and contents analysis, newly developed bibliometric analysis provides a spatial distribution of authors and the country/institution collaboration network (Liu et al. 2011). Co-word analysis, an effective method for providing an immediate picture of the actual content of research topics, has been widely applied in various studies (Callon et al. 1991; Ding et al. 2001). Recently, a new index, the geographic impact factor (GIF), was constructed to evaluate to the academic geographic influence of authors in a specific scientific field during a certain period (Zhuang et al. 2012). The purpose of this study is to provide a bibliometric analysis of sediment-related research in earth science from 1992 to 2011. Specially, this article aims at (1) identifying general patterns for publication outputs, journals and subject categories in sediment research; (2) evaluating author, national and institutional research performance; and (3) summarising global research trends, which may serve as a potential guide for future research.

Data sources and methods Documents were obtained from the online version of SCI-Expanded (SCIE), which is a multidisciplinary database of Thomson Reuters’ Web of Science. SCI-Expanded is the most important and frequently used source for a broad review of scientific accomplishment in all fields (Kostoff 2000; Li et al. 2009). Sediment-related articles published during the period of 1992–2011 were queried based on the topic ‘‘sediment*’’, on behalf of all sediment-related terms, such as ‘‘sediment’’, ‘‘sediments’’, ‘‘sedimentation’’, and ‘‘sedimentary’’. To restrict our domains in the field of earth science, all journals that published articles on sediments were refined using 28 relevant Web of Science categories (Table 6 in Appendix I). The conventional analysis of scientific outputs, subject categories, journals, authors, countries, institutes, and keywords were processed by Microsoft Excel 2007. The affiliations of authors were geocoded using CiteSpace 2.2 R11 (Chen 2004), and the worldwide geographic distribution of authors was plotted using ArcGIS 10.0. The relative importance of each individual country/territory in the collaboration network was measured using Ucinet 6 software. Publications originating from England, Scotland, Northern Ireland, and Wales were reclassified as from the United Kingdom (UK), and publications from Hong Kong were apportioned with those from mainland China. The reported impact factor (IF)

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513 14000

1600000

SCIE publications

1400000

Sediment-related publications

12000

10000

1200000 1000000

8000

800000

6000

600000 4000

400000

Sediment-related publications

SCIE publications

1800000

2000

200000 0

0

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

Fig. 1 Growth of SCIE publications and sediment-related publications in earth science

of each journal was obtained from 2011 JCR. The collaboration type was determined by the addresses of authors, where the term ‘‘single country/institution’’ was assigned if researchers’ addresses were from the same country/institution and the term ‘‘international/ inter-institutionally collaboration’’ was assigned if an article was co-signed by researchers from multiple countries/institutions. Our keywords analysis contained author keywords and keywords plus, using 5-year intervals to minimize year-to-year fluctuations. Co-word analysis, based on social network analysis (SNA), was employed to reveal the patterns in sediment-related research in multidisciplinary geosciences and environmental science.

Results and discussion Characteristic of publication outputs From this study, 18 document types were found in a total of 164,061 publications during the 20-year study period. Article (153,525), including the articles published as proceeding papers or book chapters, was the dominant document type, comprising 93.6 % of the total production. Because there were practically no abstracts or keywords in articles before 1991, only the articles published during 1992–2011 were used for further analysis. Ninetyseven percent of all articles were published in English. Twenty-five other languages also appeared, the most frequent of which were French (1.1 %), Russian (0.6 %), Spanish (0.4 %), Chinese (0.3 %), and German (0.2 %). Sediment-related research in earth science has grown more common over the last century, with the earliest reports appearing in 1900. Figure 1 shows that sediment-related publications increased steadily until 1990 with a lower rate of increase than that of the total SCIE publications. Sediment-related research coverage experienced tremendous growth in 1991, and the publication output grew to 2.6 times that in 1990. Since that year, sedimentrelated publications have increased at an average annual growth rate of 5 % over the past two decades, faster than SCIE publications (4 %). Moreover, the share of relevant publications of the total SCIE records has exhibited a significant increase, from *0.2 to 0.8 %.

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Distribution of subject categories and journals Due to the assignment of journals to multiple subject categories, sediment-related research covered 128 Web of Science categories. As illustrated in Fig. 2, multidisciplinary geosciences (45,874) and environmental sciences (36,276) were the two major categories in sediment-related research in earth science; the other three relatively popular subject categories were geochemistry and geophysics, marine and freshwater biology and oceanography. The annual article output steadily increased in the top 5 subject categories, and articles belonging to these 5 categories covered 75.5 % of the total articles during the 20 years. In addition, articles belonging to multidisciplinary geosciences and environmental sciences increased at high annual growth rates of 5.9 and 8.4 %, respectively. Articles on sediments in earth science were published in 1,688 journals, and the 20 most productive journals are presented in Table 1. There was a high concentration of sediment publications in these top journals. These 20 journals, or 1.2 % of the 1,688 journals, accounted for 35,603 articles, or 23.2 % of the total articles. Obviously, Environmental Science and Technology published the most articles on sediments (2,799) followed by Marine Geology (2,398), Palaeogeography Palaeoclimatology Palaeoecology (2,177) and Earth and Planetary Science Letters (1,988). Sediment-related articles published in these journals have received, on average, 25.1 citations, indicating that sedimentrelated articles published in these journals have had wide influences on this field. Furthermore, several journals published a sizeable number of highly cited sediment-related articles, including Nature (605 articles with 75,713 citations) and Science (379 articles with 42,829 citations). Author productivity and geographic distribution We geocoded the affiliations of authors using CiteSpace (Chen 2004) and plotted the worldwide geographic distribution of authors in sediment-related research of earth science

Fig. 2 Growth trend of articles related to sediment research of the top 5 categories

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Table 1 Twenty most active journals in sediment-related research in earth science Journal titles

TA (%)

IF

TC/TA

Environmental Science and Technology

2,799(1.82)

5.228

38.83

Marine Geology

2,398(1.56)

2.263

22.41

Palaeogeography Palaeoclimatology Palaeoecology

2,177(1.42)

2.392

19.89

Earth and Planetary Science Letters

1,998(1.30)

4.180

33.40

Chemosphere

1,968(1.28)

3.206

21.10

Hydrobiologia

1,939(1.26)

1.784

15.36

Sedimentary Geology

1,900(1.24)

1.537

16.50

Geology

1,850(1.21)

3.612

34.68

Journal of Coastal Research

1,817(1.18)

0.766

6.44

Geochimica Et Cosmochimica Acta

1,747(1.14)

4.259

42.79

Marine Pollution Bulletin

1,709(1.11)

2.503

18.91

Environmental Toxicology and Chemistry

1,662(1.08)

2.809

22.90

Geomorphology

1,638(1.07)

2.520

16.80

Marine Ecology-Progress Series

1,632(1.06)

2.711

28.44

Science of the Total Environment

1,579(1.03)

3.286

20.74

Estuarine Coastal and Shelf Science

1,531(1.00)

2.247

17.76

Organic Geochemistry

1,416(0.92)

2.785

21.45

Tectonophysics

1,319(0.86)

2.433

24.22

Quaternary Science Reviews

1,280(0.83)

3.973

24.25

Applied and Environmental Microbiology

1,244(0.81)

3.829

54.41

TA number of articles, IF 2011 ISI Impact factor, TC/TA average of citation

(Fig. 3). The major spatial clusters of authors are clearly distinguishable in the USA, Western Europe, and Eastern Asia and several other minor clusters in the other parts of the world. In the USA, authors were located more on the east coast than the west coast. The clusters of Western European authors were mainly located in the UK, France, Germany and the Netherlands. Japan and eastern China were the major distribution areas of authors in East Asia. We also produced a choropleth map to depict the gross domestic products (GDP) of individual countries for the year 2011 as the background (for the GDP values of countries without available GDP values in 2011, the most recent available values were used). The spatial clusters of sediment-related research overlapped quite well with regions with GDPs exceeding 2.5 trillion US dollars. This observation suggests that economic development was associated with academic outputs. We performed an author productivity analysis and listed the top 10 most productive authors in Table 2. These authors were significant research pioneers in sediment-related fields. Damste´ JSS from Utrecht University/Royal Netherlands Institute for Sea Research (NIOZ) contributed the most articles (298), followed by Schouten S also from Utrecht University/NIOZ (208), Smol JP from Queen’s University (191), Walling DE from the University of Exeter (141), and Poesen J from the Catholic University of Leuven (139). Because older articles inherently had a higher number of citations, we evaluated the academic impact of authors based on a 5-year fixed analysis window (2007–2011). Damste´ JSS ranked first in the 5-year total citations (2,427) and h-index (27), followed by Schouten S with the highest CPP (citations per publication, 21.48), which indicates that they had

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Fig. 3 Global geographic distribution of authors with GDP (current US$) of different countries in 2011 (data from the World Bank database)

most high-quality articles. Meanwhile, CCTs (the total number of citing countries/territories to all articles of a given author) and GIF (the average number of CTTs per article of a given author) based on Zhuang et al. (2012) are two important indicators of authors’ geographical influence. The largest CCTs (73) and GIF (11.82) were found in the articles produced by Damste´ JSS and Schouten S, respectively, revealing that they had greater geographical impacts than other authors in 2007–2011. To visualize the geographical influence of researchers, we gathered the author affiliations of all articles citing Damste´ JSS and Lovley DR during 2007–2011. The locations of the citing authors and the frequencies of citing countries/territories were plotted in Fig. 4. A total of 4,764 authors of 2,427 articles from 73 countries cited the 118 sediment-related articles of Damste´ JSS. Furthermore, excluding his home country the Netherlands, the USA, Germany, the UK, and China were the major influencing regions of Damste´ JSS. By contrast, Lovley DR had the lowest CCTs among the top 10 productive authors, and only 815 authors of 636 citing articles from 34 countries cited his 31 sediment-related articles published during 2007–2011. Clearly, the USA, his home country, was the major citing country, with 469 citing authors, but the number of citing authors from other countries were all \50. Although the CPP index of Lovley DR (20.52) was higher than that of Damste´ JSS (20.23), the scope of the geographical influence of Lovley DR in sediment research was relatively smaller, with little influence on South America, Africa, Eastern Europe, West Asia, and Southeast Asia. International productivity and collaboration We generated the data on international productivity and collaboration based on the affiliation information of authors. There were 456 articles without any author address information, and the total number of articles for the distribution analysis of country and institute publications was 153,069. Table 3 lists the 20 most productive countries/territories with the number of single-country articles and internationally collaborated articles. The USA was the largest contributor, publishing 45,821 articles on sediments, and the UK ranked

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Table 2 Top 10 productive authors in sediment research in earth science AU

Research institute

TA

In 5-year window (2007–2011) TA(R)

TC

CPP

hindex

CCTs

GIF

Damste´ JSS

Univ Utrecht Netherlands Inst Sea Res

298

120(1)

2,427(1)

20.23(3)

27(1)

73(1)

11.40(2)

Schouten S

Univ Utrecht Netherlands Inst Sea Res

208

102(2)

2,191(2)

21.48(1)

26(2)

65(2)

11.82(1)

Smol JP

Queens Univ

191

68(3)

760(3)

11.18(8)

15(4)

47(6)

5.57(9)

Walling DE

Univ Exeter

141

35(8)

305(10)

8.71(9)

11(9)

46(7)

7.11(8)

Poesen J

Catholic Univ Leuven

139

55(4)

617(6)

11.22(7)

15(4)

63(3)

9.09(5)

Lovley DR

Univ Massachusetts

126

31(10)

636(4)

20.52(2)

16(3)

34(10)

7.84(7)

Giesy JP

Michigan State Univ City Univ Hong Kong Univ Saskatchewan

125

49(5)

313(9)

10(10)

41(8)

5.37(10)

Jorgensen BB

Max Planck Society Aarhus Univ

125

33(9)

441(8)

13(8)

38(9)

9.09(5)

6.39(10)

13.36(4)

Danovaro R

Marche Polytech Univ

117

48(6)

635(5)

13.23(5)

15(4)

57(4)

10.46(3)

Middelburg JJ

Univ Utrecht Netherlands Inst Ecol

117

44(7)

552(7)

12.55(6)

14(7)

52(5)

9.86(4)

CPP average number of citations per publication, CCTs the number of citing countries/territories, GIF average number of CCTs per article of a given researcher

2nd with 17,510 articles, followed by Germany (13,741), France (11,831), Canada (11,902), and China (9,964). The number of single-country articles and internationally collaborated articles by these 6 countries also ranked as the top 6 among all countries in sediment-related research of earth science. The output of China increased steadily at a high rate (19.5 %) and ultimately ranked 2nd in 2010. Among the 20 most productive countries, 12 were from Europe, 3 were from Asia, 2 were from North America, 2 were from Oceania, and 1 was from South America. Furthermore, the 8 major industrial countries (G8: the USA, the UK, Germany, Canada, France, Italy, Japan, and Russia) were all included in the top 20 productive countries. The dominance of G8 in research publications has occurred in most scientific fields (Liu et al. 2011; Dong et al. 2012), demonstrating the high economic capabilities and academic levels of these countries (Arunachalam and Doss 2000). Therefore, it is instructive to compare the number of publications per country relative to population and GDP (Gattuso et al. 2005). Table 3 also lists the number of sediment-related articles per million inhabitants and articles per unit of GDP of the top 20 countries. Norway ranked first, and India ranked last, in terms of the article intensity per million inhabitants; New Zealand ranked first, and Japan ranked last, in terms of the article intensity per unit of GDP. Although the USA published the largest number of articles, it ranked 16th and 13th among the top 20 after taking population and GDP into consideration, respectively. To quantify the relationship between economic capabilities and academic outputs, a correlation analysis was performed using the data for the top 38 countries ([500

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Fig. 4 Geographical influence scope of Damste´ JSS (A) and Lovley DR (B) over 5 years (2007–2011)

articles published during 1992–2011; Fig. 5). The number of articles per million inhabitants is highly correlated with GDP per capita (r2 = 0.83). 110,067 (71.9 %) of the 153,069 articles were single-country publications and 43,458 (28.1 %) were internationally collaborated publications. Although single-country publications dominated in sediment research, international collaboration of researchers became more prevalent, which has also been a general trend in other fields (Persson et al. 2004). The proportions of internationally collaborated articles to the total outputs of these 20 countries showed significant disparity. Approximately 69 % of the articles produced by Switzerland involved other countries, whereas the proportion of collaborated articles in India only accounted for 22.3 %. The USA was the major cooperative partner of 13 other countries (Table 3), and its predominance in collaboration on sediment-related research of

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Table 3 Top 20 most productive countries/territories in sediment-related research in earth science Country/ territories

TA

R(%)

Single-country

Internationally-collaborated

SA

%

CA

%

MC(A)

A/GDP (10 billion)

A/ population (1 million)

USA

4,5821

1(29.93)

3,0111

65.71

1,5710

34.29

Canada(2,495)

2.2

8.0

UK

1,7510

2(11.44)

8,299

47.40

9,211

52.60

USA(2,334)

5.1

14.6

Germany

1,3741

3(8.98)

5,989

43.58

7,752

56.42

USA(1,881)

2.6

8.4

Canada

1,1902

4(7.78)

6,330

53.18

5,572

46.82

USA(2,495)

6.9

18.9

France

11,831

5(7.73)

5,280

44.63

6,551

55.37

USA(1,383)

3.2

9.5

China

9,964

6(6.51)

5,823

58.44

4,141

41.56

USA(1,456)

1.9

0.4

Australia

8,287

7(5.41)

4,370

52.73

3,917

47.27

USA(1,130)

7.5

20.6

Italy

6,242

8(4.08)

3,616

57.93

2,626

42.07

USA(621)

1.9

5.3

Spain

6,200

9(4.05)

3,131

50.50

3,069

49.50

UK(637)

3.4

7.2

Japan

6,012

10(3.93)

3,525

58.63

2,487

41.37

USA(743)

0.6

2.4

Netherlands

5,722

11(3.74)

2,495

43.60

3,227

56.40

UK(669)

5.5

17.8

Russia

5,249

12(3.43)

3,250

61.92

1,999

38.08

USA(501)

5.1

1.8

India

4,556

13(2.98)

3,541

77.72

1,015

22.28

USA(247)

3.3

0.2

Sweden

3,485

14(2.28)

1,505

43.19

1,980

56.81

USA(446)

5.5

19.3

Switzerland

3,439

15(2.25)

1,051

30.56

2,388

69.44

Germany(673)

4.7

23.2

Denmark

3,372

16(2.2)

1,367

40.54

2,005

59.46

Germany(412)

7.9

31.3

Norway

3,184

17(2.08)

1,192

37.44

1,992

62.56

UK(528)

6.9

34.5

Brazil

2,723

18(1.78)

1,489

54.68

1,234

45.32

USA(327)

1.4

0.7

New Zealand

2,690

19(1.76)

1,264

46.99

1,426

53.01

USA(500)

16.3

33.3

Belgium

2,442

20(1.60)

816

33.42

1,626

66.58

France(391)

3.6

11.6

TA total articles, SA Single-country articles, CA internationally collaborated articles, MC(A) major collaborator (the number of collaborated articles between two countries), A/GDP number of articles per unit of GDP, 10 billion, A/population number of articles per million inhabitants

earth science was visually confirmed in the national/territorial collaboration network of the 30 most productive countries (Fig. 6). The thickness of links represented the strength of the collaborations, and the size of the nodes represented the amount of single-country publications of each country. The USA took a core position in the collaboration network, as it was the primary collaborator with the main productive countries, such as the UK, Germany, Canada, France, and China. At the institution level, 36,745 institutions participated in sediment research in earth science, and the top 20 productive institutions are displayed in Table 4. The Chinese Academy of Sciences led institutional productivity, with 3,994 articles, followed by the US Geological Survey, with 3,714, and the Russian Academy of Sciences, with 3,440. The outputs of the top 3 most productive institutions were all above 3,400, whereas those of all other institutions were below 1,600, revealing the predominance of the top 3 institutions in sediment-related research. However, the 3 institutions are all overarching institutions that have branches in many cities, and dividing the articles among the branches would yield different rankings, with Utrecht University, the Woods Hole Oceanographic Institution, and Bremen University being the three most productive single-site institutions. Furthermore, 7 of the top 20 most productive institutions were from the USA; the other 13

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Scientometrics (2014) 98:511–529 4 dk no ch au canlse uk fi be fr ie il de us pt es hk at it gr

ln(articles per million inhabitants)

nz

3

2 cz 1 zaru

pl hu cl ar

jp

kr

tr

0

br mx eg ch

-1

ir

in -2

6

7

8

9

10

11

ln(GDP per capital)

Fig. 5 Correlation of articles per million inhabitants and GDP (current US$) per capita of the top 38 countries for the years 1992–2011. Codes for the 38 countries, according to ISO 3166, are printed in lower case to minimize overlap (ar, Argentina; au, Australia; at, Austria; be, Belgium; br, Brazil; ca, Canada; ch, Chile; ch, China; cz, Czech Republic; dk, Denmark; eg, Egypt; fi, Finland; fr, France; de, Germany; gr, Greece; hk, Hong Kong; hu, Hungary; in India; ir, Iran; ie, Ireland; il, Israel; it, Italy; jp, Japan; kr, South Korea; mx, Mexico; nl, Netherlands; nz, New Zealand; no, Norway; pl, Poland; pt, Portugal; ru, Russian; za, South Africa; es, Spain; se, Sweden; ch, Switzerland; tr, Turkey; uk, United Kingdom; us, United States)

Fig. 6 National/territorial collaboration network of the 30 most central countries

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Table 4 Top 20 most productive institutions in sediment-related research in earth science Institution

TA

Singleinstitution

Inter-institutional collaborated

SI

SI(%)

CI

CI(%)

MC(A) Nanjing Univ, China(140)

Chinese Acad Sci, China

3,994

1,017

25.46

2,977

74.54

US Geol Survey, USA

3,714

1,041

28.03

2,673

71.97

Univ Colorado, USA(103)

Russian Acad Sci, Russia

3,440

1,714

49.83

1,726

50.17

Moscow Mv Lomonosov State Univ, Russia(189)

CSIC, Spain

1,524

324

21.26

1,200

78.74

Univ Barcelona, Spain(148)

Univ Utrecht, Netherlands

1,364

261

19.13

1,103

80.87

Vrije Univ Amsterdam, Netherlands(62)

Woods Hole Oceanog Inst, USA

1,352

202

14.94

1,150

85.06

US Geol Survey, USA(73)

CNRS, France

1,277

107

8.38

1,170

91.62

Univ Paris 06, France(135)

Geol Survey Canada, Canada

1,264

296

23.42

968

76.58

Univ Alberta, Canada(55)

Univ Bremen, Germany

1,217

241

19.80

976

80.20

Alfred Wegener Inst Polar & Marine Res, Germany(138)

Univ Washington, USA

1,133

240

21.18

893

78.82


CNR, Italy

1,088

161

14.80

927

85.20

Univ Pisa, Italy(67)

Univ Paris 06, France

1,032

102

9.88

930

90.12

CNRS, France(135)

Alfred Wegener Inst Polar and Marine Res, Germany

1,024

232

22.66

792

77.34

Univ Bremen, Germany(138)

Texas A&M Univ, USA


1,012

213

21.05

799

78.95

US EPA, USA

998

246

24.65

752

75.35


Univ Cambridge, UK

979

199

20.33

780

79.67

Univ Durham, UK(41)

Univ Copenhagen, Denmark

964

224

23.24

740

76.76

Aarhus Univ, Denmark(80)

Univ Wisconsin, USA

962

234

24.32

728

75.68


Univ Minnesota, USA

939

172

18.32

767

81.68


Univ Tokyo, Japan

931

150

16.11

781

83.89

Hokkaido Univ, Japan(88)

TA total articles, SI Single-institution articles, CI inter-institutionally collaborated articles, MC(A) major collaborative institution (the number of collaborated articles between two institutions)

institutions were scattered in 11 countries. 75.6 % of articles produced by the 20 most productive institutions in sediment research were inter-institutionally collaborated. Obviously, Institutions from the same country tended to have higher rates of collaboration, and the major collaborative institutions of these 20 institutions were all from the same country. It is apparent that collaboration plays an ever-growing role in sediment research. Among the 153,069 articles with address information, 61,911(40.5 %) were independent articles published by single institution, and the other articles were inter-institutional collaborative works, including both national (31.5 %) and international (28.1 %) collaborations. As seen in Fig. 7, the number of collaborative articles exceeded the number of independent articles in 1998 and ultimately accounted for 69.1 % of the total articles in 2011. In general, the increasing trend of collaborative articles relative to the total can be partly explained by the fact that the number of institutes and countries engaged in the sediment-related research increased. In collaborative articles, national articles consistently dominated, with an overall average 52.8 % over the 20 years. The proportion of

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Fig. 7 Independent and collaborative share of articles per year (1992–2011)

international articles has recently gradually increased, from 40.9 % in 1992 to 50.8 % in 2011. We can anticipate that international collaboration will become the major form of collaborative articles in the future.

Keywords analysis Statistical analysis of keywords can be used to identify directions in science (Zhang et al. 2010; Butt et al. 2011). 5,860 articles had neither author keywords nor keywords plus, and the rest of the 147,665 articles contained 1,606,954 occurrences of 213,249 unique keywords. However, 131,349 (61.6 %) keywords were used only once, and the large number of once-only author keywords most likely indicated a lack of continuity in research and a wide disparity in research focuses (Chuang et al. 2007). Only 16,486 (7.7 %) keywords were used in more than 10 articles, and these keywords were present in mainstream sediment-related research. Keyword ranking changes in the four 5-year intervals are indicative of changes in the hot fields. The top 30 most frequently used keywords for the study period are listed in Table 5. With the exception of ‘‘sediment(s)’’ and ‘‘sedimentation’’, which were search words in this study, the three most frequently used keywords were ‘‘evolution’’, ‘‘water’’ and ‘‘soil(s)’’. Various evolutionary processes related to sediments (e.g., tectonic evolution, landscape evolution, fluvial evolution, and basin evolution) were the most important issues during the 20 years. As the main environmental medium of sediment existence, formation and transport, ‘‘water’’ remained a significant target in various sediment research fields. ‘‘Soil(s)’’ experienced a significant increase from 8th in 1992–1996 to 3rd in 2007–2011. ‘‘Model’’ was the major research method in various aspects of sediment studies, including sediment budget models, sediment transport models, and sediment prediction models (Ramos-Scharron and MacDonald 2007; Akay et al. 2008; Zhang et al. 2011).

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Table 5 Temporal evolution of the 30 most frequently used keywords Keywords

1991–1995

1996–2000

2001–2005

2006–2010

Total

Cnt

Cnt

Cnt

Cnt

Cnt

R

R

R

R

RC R

Sediment(s)

4,133

1

6,503

1

8,555

1

11,486

1

30,677

1

Evolution

1,232

2

1,753

3

2,426

2

3,261

2

8,672

2

0 1

Water

1,177

3

1,764

2

2,051

3

2,710

4

7,702

3

2

Soil(s)

646

8

1,250

4

1,774

4

2,835

3

6,505

4

5

Model

810

4

1,217

5

1,515

5

2,035

5

5,577

5

1

Basin

715

5

1,114

6

1,422

6

1,932

7

5,183

6

2

Marine-sediments

562

11

941

11

1,382

7

1,994

6

4,879

7

5

Transport

568

10

953

10

1,331

8

1,815

8

4,667

8

2

Geochemistry

673

6

1,041

7

1,222

10

1,554

12

4,490

9

6

Sea

640

9

992

8

1,225

9

1,591

10

4,448

10

2

Organic-matter

442

18

745

14

1,158

11

1,791

9

4,136

11

9

Sedimentation

668

7

968

9

1,099

12

1,108

21

3,843

12

14

River

359

28

641

19

962

17

1,579

11

3,541

13

17

Stratigraphy

438

20

815

12

983

16

1,176

20

3,412

14

8

Dynamics

363

26

575

28

1,009

14

1,375

14

3,322

15

14

Holocene

188

85

643

17

1,044

13

1,364

15

3,239

16

72

Erosion

254

55

557

29

987

15

1,316

17

3,114

17

40

Growth

519

14

746

13

871

21

898

38

3,034

18

25

Sediment transport

189

84

438

49

935

18

1,382

13

2,944

19

71

Climate

194

81

602

24

931

19

1,194

19

2,921

20

62

Ocean

535

12

718

15

788

24

877

41

2,918

21

29

Carbon

417

21

708

16

797

23

987

31

2,909

22

15

Nitrogen

377

24

635

20

788

25

1,092

23

2,892

23

5

Record

303

36

593

26

881

20

1,072

25

2,849

24

16

Deposits

468

16

583

27

732

30

1,034

30

2,817

25

14

Phosphorus

360

27

537

31

840

22

1,070

26

2,807

26

9

Heavy-metal

247

58

460

45

742

28

1,333

16

2,782

27

42

Origin

520

13

642

18

723

31

843

45

2,728

28

32

History

397

23

604

23

761

27

886

39

2,648

29

16

Bacteria

448

17

618

22

624

42

919

36

2,609

30

25

Cnt count of occurrences, R rank, RC change in rank

‘‘Marine-sediments’’ received increased attention with a rise in rankings from 11th to 6th over the 20 years. Both ‘‘transport’’ and ‘‘sediment transport’’ had an apparent upward movement in their ranks, from 10th and 84th in 1992–1996 to 8th and 13th in 2007–2011, respectively. In addition, important progress was made in the mechanisms and spatially distributed modelling of sediment transport (de Vente et al. 2007; Braun et al. 2011). ‘‘Sea’’, ‘‘river’’ and ‘‘ocean’’, as the main water bodies, were all included in the 30 most frequently used keywords, and the rank of ‘‘river’’ increased from 28th to 11th over the last two decades. ‘‘Dynamics’’ enjoyed a large rank advancement during the study period,

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524


Fig. 8 Co-word network of top 30 high-frequency keywords in geosciences, multidisciplinary and environmental sciences

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525

indicating that studies on the dynamics of sediment transport and soil erosion during different events became more prevalent in sediment research (Sauvage et al. 2010; Marttila and Klove 2010). The rank of ‘‘Erosion’’ also changed from 55th to 17th over the 20 years. Erosion of soil and the underlying regolith contributed the most to sediment yield, and the off-site effects of erosion included sedimentation problems in rivers and lakes, increased flood risk, loss of biodiversity, and a reduction of the reservoir service life (Haregeweyn et al. 2006; Telles et al. 2011). Accordingly, several researchers have emphasized the management of soil erosion for the control of sediment loads in water reservoirs and river basins (Apitz and Power 2002; Apitz and White 2003). Studies on ‘‘nitrogen’’, ‘‘carbon’’, and ‘‘phosphorus’’ maintained a relatively stable position, whereas the rank of ‘‘organic-matter’’ and ‘‘heavy-metal’’ steadily increased from 18th and 58th in 1992–1996 to 9th and 16th in 2007–2011, respectively. Long-term industrialisation and urbanisation has led to organic-matter and heavy metal contamination in aquatic sediments, which is one of the greatest threats to water quality, aquatic ecosystems and human health (Wang et al. 2011). Therefore, contamination of sediments has become a critical area of growing concern worldwide. Furthermore, it is worth noticing that there was little work on ‘‘Holocene’’ and ‘‘climate’’ in the past, but articles on these aspects have obviously increased in recent years. Sediments and their associated processes during the Holocene period, the latest geological epoch, have received plenty of attention (Yang et al. 2004; Rankey et al. 2009), and research on climate change based on geochemical characteristics has become more prevalent (Wang et al. 1999). In contrast, several words, such as ‘‘deposits’’, ‘‘origin’’, ‘‘history’’ and ‘‘bacteria’’, gradually became less significant over the 20-year study period. To achieve a deeper understanding of sediment research publication patterns, we performed a co-word analysis of the frequently used keywords from articles included in the two major categories. Significant differences could be found in terms of research hotspots between the two major categories (Fig. 8). In multidisciplinary geosciences, articles were mainly focused on ‘‘evolution’’, ‘‘basin’’, ‘‘Holocene’’, ‘‘stratigraphy’’, and ‘‘record’’. It is worth noting that there are high co-occurrence frequencies between ‘‘evolution’’ and ‘‘basin’’, ‘‘tectonics’’, and ‘‘stratigraphy’’, indicating that ‘‘basin evolution’’, ‘‘tectonics evolution’’, and ‘‘stratigraphy evolution’’ were the main research targets of sedimentrelated research (Chough et al. 2000; Bracone et al. 2012). In addition, the close relationship of ‘‘Holocene’’ with ‘‘climate/climate change’’ and ‘‘record’’ indicates that an abundance of research was focused on the reconstruction of past environmental changes by analysing the parameters of sediment records, which are critical for understanding the natural variability of the earth’s climate system and for providing a context for present and future global change (Briner et al. 2006; Kirby et al. 2007). By contrast, in Environmental Science, there was a great deal of concern regarding contaminated sediments and their impacts on the ambient environment and ecosystem health. ‘‘Water’’, ‘‘heavy metals’’, ‘‘soil’’, ‘‘polycyclic aromatic-hydrocarbons (PAH)’’, and ‘‘adsorption’’ were the main research themes. Sediments are important components of aquatic ecosystems, in which most water pollutants (PAH, heavy metals, etc.) accumulate (Leivuori 1998; Zhou and Maskaoui 2003; Bartolomeo et al. 2004). The high co-occurrence frequency of ‘‘heavy metal’’ and ‘‘PAH’’ with ‘‘pollution/contamination’’, ‘‘accumulation’’, ‘‘bioavailability’’ and ‘‘adsorption’’ showed that sediment contamination, toxicity and pollutant removal are ongoing problems (Philips et al. 2006). Many studies have evaluated the toxicity of contaminated sediments and their adverse effects on aquatic

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ecosystems (Kemble et al. 2000; Fuchsman et al. 2006) and also attempted to determine the optimal remediation strategies (Forstner and Apitz 2007; Peng et al. 2009).

Conclusions Based on a bibliometric analysis, a clear insight was obtained into the global trends in sediment-related research patterns in earth science during 1992–2011. The amount of sediment-related publication outputs exploded at an average annual growth rate of 5 % over the past two decades, faster than SCIE publications. ‘‘Geosciences, multidisciplinary’’ and ‘‘environmental sciences’’ were the two major subject categories. As the flagship journal of the field, Environmental Science and Technology published the most articles, and *23.2 % of the total sediment-related articles resided in the top 20 productive journals. The worldwide geographic distribution of authors in sediment-related research was visualized, with major spatial clusters in the USA, Western Europe, and Eastern Asia, which overlapped quite well with regions with GDPs exceeding 2.5 trillion US dollars. Among the top 10 prolific authors, Damste´ JSS from Utrecht University/NIOZ contributed the most articles with the largest h-index and CCTs followed by Schouten S with the highest CPP and GIF, indicating that they had more high-quality articles and greater geographical influence. Although the CPP of Lovley DR was greater than that of Damste´ JSS, this researcher’s geographical influence scope was obviously smaller. The USA produced the largest number of single-country and internationally collaborated articles followed by the UK and Germany. The output of China on sediments showed a steady growth and ultimately ranked 2nd in 2011. National academic output was positively associated with its economic capability. The Chinese Academy of Sciences, US Geological Survey and Russian Academy of Sciences were the three most productive institutions, whereas Utrecht University, the Woods Hole Oceanographic Institution, and Bremen University were the three most productive single-site institutions. Network analysis suggested that USA was in the central position of the national collaboration network. Additionally, both national and international collaborative articles were more prevalent in recent years. A keywords analysis found several interesting terminology preferences, confirmed the central position of ‘‘evolution’’, ‘‘water’’, ‘‘soil/soils’’, and ‘‘model’’ in sediment research, and demonstrated increased research interest in ‘‘organic-matter’’, ‘‘Holocene’’, ‘‘dynamics’’, ‘‘erosion’’, ‘‘sediment transport’’, ‘‘climate’’, and ‘‘heavy-metal’’. Based on the coword analysis, significant differences were found between multidisciplinary geosciences and environmental science in terms of research hotspots, and the prevalent research topic patterns were also ascertained in these two fields. The former primarily related to surface evolution, stratigraphy and tectonics, and the latter mainly concerned contaminated sediments, their adverse impacts and methods of removal. Acknowledgments The authors are thankful to Mr. Nan Feng (University of Alabama at Huntsville, USA), Mr. Xingjian Liu (University of Cambridge, UK) and Mrs. Yanhua Zhuang (Wuhan University, China) for their contributions of innovative analysis methods.

Appendix I See Table 6.

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Scientometrics (2014) 98:511–529 Table 6 28 relevant Web of Science categories of earth science

527

No.

Web of science category

1

Archaeology

2

Biology

3

Ecology

4

Energy and Fuels

5

Engineering, Environmental

6

Engineering, Geological

7

Engineering, Ocean

8

Engineering, Petroleum

9

Environmental Sciences

10

Environmental Studies

11

Evolutionary Biology

12

Geochemistry and Geophysics

13

Geography, Physical

14

Geology

15

Geosciences, Multidisciplinary

16

Limnology

17

Marine and Freshwater Biology

18

Meteorology and Atmospheric Sciences

19

Microbiology

20

Mineralogy

21

Multidisciplinary Sciences

22

Oceanography

23

Paleontology

24

Plant Sciences

25

Remote Sensing

26

Soil Science

27

Toxicology

28

Water Resources

References Abramo, G., D’Angelo, C. A., & Viel, F. (2011). The field-standardized average impact of national research systems compared to world average: the case of Italy. Scientometrics, 88(2), 599–615. Akay, A. E., Erdas, O., Reis, M., & Yuksel, A. (2008). Estimating sediment yield from a forest road network by using a sediment prediction model and GIS techniques. Building and Environment, 43(5), 687–695. Apitz, S. E., & Power, B. (2002). From risk assessment to sediment management: An international perspective. Journal of Soils and Sediments, 2, 61–66. Apitz, S. E., & White, S. (2003). A conceptual framework for river-basin-scale sediment management. Journal of Soils and Sediments, 3, 132–138. Arunachalam, S., & Doss, M. J. (2000). Mapping international collaboration in science in Asia through coauthorship analysis. Current Science, 79(5), 621–628. Bartolomeo, A. D., Poletti, L., Sanchini, G., Sebastiani, B., & Morozzi, G. (2004). Relationship among parameters of lake polluted sediments evaluated by multivariate statistical analysis. Chemosphere, 55, 1323–1329. Bracone, V., Amorosi, A., Aucelli, P. P. C., Rosskopf, C. M., Scarciglia, F., Di Donato, V., et al. (2012). The Pleistocene tectono-sedimentary evolution of the Apenninic foreland basin between Trigno and Fortore rivers (Southern Italy) through a sequence stratigraphic perspective. Basin Research, 24(2), 213–233.

123

528


Braun, J., Heimsath, A. M., & Chappell, J. (2011). Sediment transport mechanisms on soil-mantled hillslopes geology, 29(8), 683–686. Briner, J. P., Michelutti, N., Francis, D. R., Miller, G. H., Axford, Y., Wooller, M. J., et al. (2006). A multiproxy lacustrine record of Holocene climate change on northeastern Baffin Island, Arctic Canada. Quaternary Research, 65(3), 431–442. Butt, M. J., Mahmood, R., & Waqas, A. (2011). Sediments deposition due to soil erosion in the watershed region of Mangla Dam. Environmental Monitoring and Assessment, 181(1–4), 419–429. Callon, M., Courtial, J. P., & Laville, F. (1991). Co-word analysis as a tool for describing the network of interactions between basic and technological research—the case of polymer chemistry. Scientometrics, 22(1), 155–205. Chen, C. (2004). Searching for intellectual turning points: progressive knowledge domain visualization. Proceedings of the National Academy of Sciences of the United States of America, 101(1), 5303–5310. Chen, S. R., Chiu, W. T., & Ho, Y. S. (2005). Asthma in children: mapping the literature by bibliometric analysis. Revue Francaise D Allergologie Et D Immunologie Clinique, 45(6), 442–446. Chiu, W. T., & Ho, Y. S. (2007). Bibliometric analysis of tsunami research. Scientometrics, 73(1), 3–17. Chough, S. K., Kwon, S. T., Ree, J. H., & Choi, D. K. (2000). Tectonic and sedimentary evolution of the Korean peninsula: A review and new view. Earth-Science Reviews, 52(1–3), 175–235. Chuang, K. Y., Huang, Y. L., & Ho, Y. S. (2007). A bibliometric and citation analysis of stroke-related research in Taiwan. Scientometrics, 72(2), 201–212. de Vente, J., Poesen, J., Arabkhedri, M., & Verstraeten, G. (2007). The sediment delivery problem revisited. Progress in Physical Geography, 31(2), 155–178. Ding, Y., Chowdhury, G. G., & Foo, S. (2001). Bibliometric cartography of information retrieval research by using co-word analysis. Information Processing and Management, 37(6), 817–842. Dong, B. S., Xu, G. Q., Luo, X., Cai, Y., & Gao, W. (2012). A bibliometric analysis of solar power research from 1991 to 2010. Scientometrics, 93(3), 1101–1117. Elfrink, B., & Baldock, T. (2002). Hydrodynamics and sediment transport in the swash zone: a review and perspectives. Coastal Engineering, 45(3–4), 149–167. Forstner, U., & Apitz, S. E. (2007). Sediment remediation: US focus on capping and monitored natural recovery—fourth international battelle conference on remediation of contaminated sediments. Journal of Soils and Sediments, 7(6), 351–358. Fuchsman, P. C., Barber, T. R., Lawton, J. C., & Leigh, K. B. (2006). An evaluation of cause-effect relationships between polychlorinated biphenyl concentrations and sediment toxicity to benthic invertebrates. Environmental Toxicology and Chemistry, 25(10), 2601–2612. Gattuso, J. P., Dawson, N. A., Duarte, C. M., & Middelburg, J. J. (2005). Patterns of publication effort in coastal biogeochemistry: A bibliometric survey (1971 to 2003). Marine Ecology Progress Series, 294, 9–22. Glanzel, W., Schubert, A., & Czerwon, H. J. (1999). A bibliometric analysis of international scientific cooperation of the European Union (1985–1995). Scientometrics, 45(2), 185–202. Govindaraju, R. S., Shrestha, P. L., & Roig, L. C. (1997). A continuum theory for evolution of soft sediment beds with application to sediment dynamics. Water for a Changing Global Community, 27, 1262–1267. Grotzinger, J. P., Arvidson, R. E., Bell, J. F., Calvin, W., Clark, B. C., Fike, D. A., et al. (2005). Stratigraphy and sedimentology of a dry to wet eolian depositional system, Burns formation, Meridiani Planum, Mars. Earth and Planetary Science Letters, 240(1), 11–72. Haregeweyn, N., Poesen, J., Nyssen, J., De Wit, J., Haile, M., Govers, G., et al. (2006). Reservoirs in Tigray (Northern Ethiopia): characteristics and sediment deposition problems. Land Degradation and Development, 17(2), 211–230. Ho, Y. S. (2007). Bibliometric analysis of adsorption technology in environmental science. Journal of Environmental Protection Science, 1(1), 1–11. Ho, Y. S., Wang, M. H., & Yu, T. C. (2010). A bibliometric analysis of the performance of Water Research. Scientometrics, 84(3), 813–820. Holland, K. T., & Elmore, P. A. (2008). A review of heterogeneous sediments in coastal environments. Earth-Science Reviews, 89(3–4), 116–134. Hsieh, W. H., Chiu, W. T., Lee, Y. S., & Ho, Y. S. (2004). Bibliometric analysis of patent ductus arteriosus treatments. Scientometrics, 60(2), 105–115. Kemble, N. E., Hardesty, D. G., Ingersoll, C. G., Johnson, B. T., Dwyer, F. T., & MacDonald, D. D. (2000). An evaluation of the toxicity of contaminated sediments from Waukegan Harbor, Illinois, following remediation. Archives of Environmental Contamination and Toxicology, 39(4), 452–461. Kirby, M., Lund, S., Anderson, M., & Bird, B. (2007). Insolation forcing of Holocene climate change in Southern California: a sediment study from Lake Elsinore. Journal of Paleolimnology, 38(3), 395–417. Kostoff, R. N. (2000). The underpublishing of science and technology results. Scientist, 14(9), 6.

123


529

Leivuori, M. (1998). Heavy metal contamination in surface sediments in the Gulf of Finland and comparison with the Gulf of Bothnia. Chemosphere, 36(1), 43–59. Li, L. L., Ding, G. H., Feng, N., Wang, M. H., & Ho, Y. S. (2009). Global stem cell research trend: Bibliometric analysis as a tool for mapping of trends from 1991 to 2006. Scientometrics, 80(1), 39–58. Liu, X. J., Zhang, L. A., & Hong, S. (2011). Global biodiversity research during 1900–2009: a bibliometric analysis. Biodiversity and Conservation, 20(4), 807–826. Long, E. R., Macdonald, D. D., Smith, S. L., & Calder, F. D. (1995). Incidence of adverse biological effects within ranges of chemical concentrations in Marine and Estuarine sediments. Environmental Management, 19(1), 81–97. Marttila, H., & Klove, B. (2010). Dynamics of erosion and suspended sediment transport from drained peatland forestry. Journal of Hydrology, 388(3–4), 414–425. Peng, J. F., Song, Y. H., Yuan, P., Cui, X. Y., & Qiu, G. L. (2009). The remediation of heavy metals contaminated sediment. Journal of Hazardous Materials, 161(2–3), 633–640. Persson, O., Glanzel, W., & Danell, R. (2004). Inflationary bibliometric values: The role of scientific collaboration and the need for relative indicators in evaluative studies. Scientometrics, 60(3), 421–432. Philips, B. M., Anderson, B. S., Hunt, J. W., Huntley, S. A., Tjeerdema, R. S., Kapellas, N., et al. (2006). Solid-phase sediment toxicity identification evaluation in an agricultural stream. Environmental Toxicology and Chemistry, 25(6), 1671–1676. Ramos-Scharron, C. E., & MacDonald, L. H. (2007). Development and application of a GIS-based sediment budget model. Journal of Environmental Management, 84(2), 157–172. Rankey, E. C., Guidry, S. A., Reeder, S. L., & Guarin, H. (2009). Geomorphic and sedimentologic heterogeneity along a Holocene shelf margin: Caicos Platform. Journal of Sedimentary Research, 79(5–6), 440–456. Sauvage, S., Oeurng, C., & Sanchez-Perez, J. M. (2010). Dynamics of suspended sediment transport and yield in a large agricultural catchment, southwest France. Earth Surface Processes and Landforms, 35(11), 1289–1301. Telles, T. S., Guimaraes, M. D., & Dechen, S. C. F. (2011). The costs of soil erosion. Revista Brasileira De Ciencia Do Solo, 35(2), 287–298. van Beelen, P., & Doelman, P. (1997). Significance and application of microbial toxicity tests in assessing ecotoxicological risks of contaminants in soil and sediment. Chemosphere, 34(3), 455–499. van Raan, A. (1999). Advanced bibliometric methods for the evaluation of universities. Scientometrics, 45(3), 417–423. Wang, S. L., Lin, C. Y., & Cao, X. Z. (2011). Heavy metals content and distribution in the surface sediments of the Guangzhou section of the Pearl River, Southern China. Environmental Earth Sciences, 64(6), 1593–1605. Wang, L., Sarnthein, M., Erlenkeuser, H., Grimalt, J. O., Grootes, P., Heilig, S., et al. (1999). East Asian monsoon climate during the Late Pleistocene: high-resolution sediment records from the south China Sea. Marine Geology, 156(1–4), 245–284. Yang, W., Mazzullo, S. J., & Teal, C. S. (2004). Sediments, facies tracts, and variations in sedimentation rates of Holocene platform carbonate sediments and associated deposits, northern Belize: Implications for ‘‘representative’’ sedimentation rates. Journal of Sedimentary Research, 74(4), 498–512. Zhang, L. A., Wang, M. H., Hu, J., & Ho, Y. S. (2010). A review of published wetland research, 1991–2008: Ecological engineering and ecosystem restoration. Ecological Engineering, 36(8), 973–980. Zhang, C., Zheng, J. H., Wang, Y. G., Zhang, M. T., Jeng, D. S., & Zhang, J. S. (2011). A process-based model for sediment transport under various wave and current conditions. International Journal of Sediment Research, 26(4), 498–512. Zhou, J. L., & Maskaoui, K. (2003). Distribution of polycyclic aromatic hydrocarbons in water and surface sediments from Daya Bay, China. Environmental Pollution, 121, 269–281. Zhuang, Y., Liu, X., Nguyen, T., He, Q., & Hong, S. (2012). Global remote sensing research trends during 1991–2010: A bibliometric analysis. Scientometrics, 96(1), 203–219.

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