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2005 Combined Bibliometric Analysis for Papers on Topics Relating to Water Quality Research (Papers Published 1995-2005)
November 2006

This is a bibliometric analysis of the papers prepared by intramural and extramural researchers of the U.S. Environmental Protection Agency (EPA) on topics related to water quality research that were published from 1995 to 2005. For this analysis, 800 papers were reviewed. These 800 papers were cited 10,234 times in the journals covered by Thomsons Web of Science.1 Of these 800 papers, 668 (84%) have been cited at least once in a journal.

The analysis was completed using Thomsons Essential Science Indicators (ESI) and Journal Citation Reports (JCR) as benchmarks. ESI provides access to a unique and comprehensive compilation of essential science performance statistics and science trends data derived from Thomsons databases. For influence and impact measures, ESI employs both total citation counts and cites per paper scores. The former reveals gross influence while the latter shows weighted influence, also called impact. JCR presents quantifiable statistical data that provide a systematic, objective way to evaluate the worlds leading journals and their impact and influence in the global research community.

Summary of Analysis

Nearly one-seventh of the water quality publications are highly cited papers. A review of the citations indicates that 114 (14.2%) of the water quality papers qualify as highly cited when using the ESI criteria for the top 10% of highly cited publications. Twelve (1.5%) of the water quality papers qualify as highly cited when using the criteria for the top 1%. Three (0.38%) of the papers meet the 0.1% thresholds for very highly cited papers, and two (0.25%) of the papers qualify as very highly cited when using the criteria for the top 0.01%.

The water quality papers are more highly cited than the average paper. Using the ESI average citation rates for papers published by field as the benchmark, in 10 of the 12 fields in which the EPA water quality papers were published, the ratio of actual to expected cites is greater than 1, indicating that the water quality papers are more highly cited than the average papers in those fields.

Approximately one-eighth of the water quality papers are published in very high impact journals. One-hundred six (106) of the 800 papers were published in the top 10% of journals ranked by JCR Impact Factor, representing 13.2% of EPAs water quality papers. Ninety-one (91) of the 800 papers appear in the top 10% of journals ranked by JCR Immediacy Index, representing 11.4% of EPAs water quality papers.

Nine of the water quality publications qualified as hot papers. ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorterpapers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Using the current hot paper thresholds established by ESI as a benchmark, nine of the water quality papers, representing 1.1% of the water quality publications, were identified as hot papers in the analysis.

The authors of the water quality papers cite themselves less than the average self-citation rate. Four hundred seventeen (417) of the 10,234 cites are author self-cites. This 4.1% author self-citation rate is below the accepted range of 10-30% author self-citation rate.

Highly Cited Water Quality Publications

The 800 water quality papers reviewed for this analysis covered 12 of the 22 ESI fields of research. The distribution of the papers among these 12 fields and the number of citations by field are presented in Table 1.

Table 1. Water Quality Papers by ESI Fields

No. of Citations

ESI Field

No. of EPA Water Quality Papers

Average Cites/Paper

8,092

Environment/Ecology

581

13.93

500

Pharmacology & Toxicology

40

12.50

432

Engineering

47

9.19

320

Biology & Biochemistry

32

10.00

310

Microbiology

23

13.48

215

Chemistry

33

6.52

170

Plant & Animal Science

29

5.86

99

Multidisciplinary

4

24.75

47

Geosciences

5

9.40

36

Agricultural Sciences

3

12.00

8

Clinical Medicine

2

4.00

5

Physics

1

5.00

Total =
10,234

 

Total =
800

 

12.79

There were 114 (14.2% of the papers analyzed) highly cited EPA water quality papers in 10 of the 12 fieldsEnvironment/Ecology, Engineering, Pharmacology & Toxicology, Biology & Biochemistry, Microbiology, Chemistry, Multidisciplinary, Plant & Animal Science, Geosciences, and Agricultural Scienceswhen using the ESI criteria for the top 10% of papers. Table 2 shows the number of EPA papers in those 10 fields that met the top 10% threshold in ESI.

Twelve (1.5%) of the papers analyzed qualified as highly cited when using the ESI criteria for the top 1% of papers (see Table 3). These papers were categorized in the fields of Environment/ Ecology and Engineering. The citations for these papers are presented in Tables 4 and 5. Three of the 800 papers (0.38%) met the 0.1% threshold, which is nearly four times the number expected, and two of the 800 papers (0.25%) met the 0.01% threshold for very highly cited papers, which is nearly 25 times the number expected. The citations for the papers that met the 0.1% and the 0.01% thresholds for very highly cited papers are provided in Tables 6 and 7, respectively.

Table 2. Number of Highly Cited Water Quality Papers by Field (top 10%)


No. of Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

4,647

Environment/Ecology

69

67.35

11.88%

349

Engineering

18

19.39

38.30%

293

Pharmacology & Toxicology

7

41.86

17.50%

155

Biology & Biochemistry

1

155.00

3.13%

149

Microbiology

3

49.67

13.04%

88

Chemistry

6

14.67

18.18%

85

Multidisciplinary

3

28.33

75.00%

57

Plant & Animal Science

5

11.40

17.24%

30

Geosciences

1

30.00

20.00%

10

Agricultural Sciences

1

10.00

33.33%

Total =
5,863

 

Total =
114


51.43

 

Table 3. Number of Highly Cited Water Quality Papers by Field (top 1%)


No. of Citations

ESI Field

No. of Papers

Average Cites/Paper

% of EPA Papers in Field

2,191

Environment/Ecology

9

243.44

1.55%

148

Engineering

3

49.33

6.38%

Total =
2,339

 

Total =
12


194.92

 

Table 4. Citations of Highly Cited Water Quality Papers in the Field of Environment/Ecology (top 1%)

No. of Cites

First Author

Paper

792

Van den Berg M

Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives 1998;106(12):775-792.

323

Daughton CG

Pharmaceuticals and personal care products in the environment: agents of subtle change? Environmental Health Perspectives 1999;107(Suppl 6):907-938.

304

Howarth RW

Regional nitrogen budgets and riverine N&P fluxes for the drainages to the North Atlantic Ocean: natural and human influences. Biogeochemistry 1996;35(1):75-139.

230

Folmar LC

Vitellogenin induction and reduced serum testosterone concentrations in feral male carp (Cyprinus carpio) captured near a major metropolitan sewage treatment plant. Environmental Health Perspectives 1996;104(10):1096-1101.

170

Poff NL

Functional-organization of stream fish assemblages in relation to hydrological variability. Ecology 1995;76(2):606-627.

130

Boynton WR

Inputs, transformations, and transport of nitrogen and phosphorus in Chesapeake Bay and selected tributaries. Estuaries 1995;18(1B):285-314.

128

Ankley GT

Technical basis and proposal for deriving sediment quality criteria for metals. Environmental Toxicology and Chemistry 1996;15(12):2056-2066.

111

Erickson RJ

The effects of water chemistry on the toxicity of copper to fathead minnows. Environmental Toxicology and Chemistry 1996;15(2):181-193.

3

Lackey RT

Economic growth and salmon recovery: an irreconcilable conflict? Fisheries 2005;30(3):30-32.

Table 5. Citations of Highly Cited Water Quality Papers in the Field of Engineering (top 1%)


No. of Cites

First Author

Paper

57

Jaworski NA

Atmospheric deposition of nitrogen oxides onto the landscape contributes to coastal eutrophication in the northeast United States. Environmental Science & Technology 1997;31(7):1995-2004.

50

Ankley GT

Effects of light-intensity on the phototoxicity of fluoranthene to a benthic macroinvertebrate. Environmental Science & Technology 1995;29(11):2828-2833.

41

Montgomery DR

Process domains and the river continuum. Journal of the American Water Resources Association 1999;35(2):397-410.

Table 6. Citations of Very Highly Cited Water Quality Papers (top 0.1%)


Field

No. of Cites

First Author

Paper

Environment/Ecology

792

Van den Berg M

Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives 1998;106(12):775-792.

 

323

Daughton CG

Pharmaceuticals and personal care products in the environment: agents of subtle change? Environmental Health Perspectives 1999;107(Suppl 6):907-938.

 

304

Howarth RW

Regional nitrogen budgets and riverine N&P fluxes for the drainages to the North Atlantic Ocean: natural and human influences. Biogeochemistry 1996;35(1):75-139.

Table 7. Citations of Very Highly Cited Water Quality Papers (top 0.01%)


Field

No. of Cites

First Author

Paper

Environment/Ecology

792

Van den Berg M

Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives 1998;106(12):775-792.

 

323

Daughton CG

Pharmaceuticals and personal care products in the environment: agents of subtle change? Environmental Health Perspectives 1999;107(Suppl 6):907-938.

Ratio of Actual Cites to Expected Citation Rates

The expected citation rate is the average number of cites that a paper published in the same journal in the same year and of the same document type (article, review, editorial, etc.) has received from the year of publication to the present. Using the ESI average citation rates for papers published by field as the benchmark, in 10 of the 12 fields in which the EPA water quality papers were published, the ratio of actual to expected cites is greater than 1, indicating that the EPA papers are more highly cited than the average papers in those fields (see Table 8).

Table 8. Ratio of Actual Cites to Expected Cites for Water Quality Papers by Field


ESI Field

Total Cites

Expected Cite Rate

Ratio

Multidisciplinary

99

16.67

5.94

Engineering

432

121.31

3.56

Agricultural Sciences

36

12.51

2.88

Environment/Ecology

8,092

4,511.15

1.79

Geosciences

47

26.78

1.76

Physics

5

3.32

1.51

Plant & Animal Science

170

118.87

1.43

Pharmacology & Toxicology

500

359.62

1.39

Chemistry

215

187.34

1.15

Microbiology

310

284.98

1.09

Clinical Medicine

8

8.86

0.90

Biology & Biochemistry

320

392.86

0.81

JCR Benchmarks

The Impact Factor is a well known metric in citation analysis. It is a measure of the frequency with which the average article in a journal has been cited in a particular year. The Impact Factor helps evaluate a journals relative importance, especially when compared to others in the same field. The Impact Factor is calculated by dividing the number of citations in the current year to articles published in the 2 previous years by the total number of articles published in the 2 previous years.

Table 9 indicates the number of water quality papers published in the top 10% of journals, based on the JCR Impact Factor. One-hundred six (106) of the 800 papers were published in the top 10% of journals, representing 13.2% of EPAs water quality papers. This exceeds the expected number of 80 papers (10%) published in the top 10% of high impact journals.

Table 9. Water Quality Papers in Top 10% of Journals by JCR Impact Factor


EPA Water Quality Papers in that Journal

Journal

Impact Factor (IF)

JCR IF Rank

20

Environmental Science & Technology

3.557

540

14

Environmental Health Perspectives

3.929

439

14

Limnology and Oceanography

3.024

737

10

Applied and Environmental Microbiology

3.810

470

6

Ecological Applications

3.287

623

5

Analytical Chemistry

5.450

243

5

Ecology

4.104

394

5

Toxicological Sciences

3.391

591

5

Journal of Chromatography A

3.359

602

3

TRAC-Trends in Analytical Chemistry

3.888

452

2

Nature

32.182

9

2

Proceedings of the National Academy of Sciences of the United States of America

10.452

88

2

Electrophoresis

3.743

482

2

Ecosystems

3.283

624

2

Remote Sensing of Environment

3.185

666

2

Bioscience

3.041

730

1

Lancet

21.713

20

1

Progress in Nuclear Magnetic Resonance Spectroscopy

6.885

175

1

Molecular Ecology

4.375

351

1

Drug Metabolism and Disposition

3.836

461

1

Journal of the American Society for Mass Spectrometry

3.760

479

1

Proceedings of the Royal Society of London Series B-Biological Sciences

3.653

509

1

Frontiers in Ecology and the Environment

3.362

600

Total = 106

     

Immediacy Index

The journal Immediacy Index is a measure of how quickly the average article in a journal is cited. It indicates how often articles published in a journal are cited within the year they are published. The Immediacy Index is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

Table 10 indicates the number of EPA water quality papers published in the top 10% of journals, based on the JCR Immediacy Index. Ninety-one (91) of the 800 papers appear in the top 10% of journals, representing 11.4% of EPAs water quality papers. This exceeds the expected number of 80 papers (10%) published in the top 10% of high impact journals.

Table 10. Water Quality Papers in Top 10% of Journals by JCR Immediacy Index


EPA Water Quality Papers in that Journal

Journal

Immediacy Index (II)

JCR II Rank

20

Environmental Science & Technology

0.623

617

14

Environmental Health Perspectives

1.202

202

6

Ecological Applications

0.747

466

6

Freshwater Biology

0.664

558

5

Analytical Chemistry

0.885

346

5

Hydrobiologia

0.681

532

5

Ecology

0.590

676

4

Ecotoxicology

1.450

151

3

Journal of Geophysical Research

0.617

630

3

TRAC-Trends in Analytical Chemistry

0.583

681

2

Nature

6.089

5

2

Ecosystems

2.048

76

2

Proceedings of the National Academy of Sciences of the United States of America

1.923

89

2

Bioscience

0.863

356

2

Electrophoresis

0.575

697

1

Lancet

5.017

12

1

Journal of Paleolimnology

1.581

132

1

Ambio

1.435

156

1

Climatic Change

1.235

195

1

Journal of Oceanography

0.692

519

1

Molecular Ecology

0.674

545

1

Progress in Nuclear Magnetic Resonance Spectroscopy

0.667

551

1

Drug Metabolism and Disposition

0.590

676

1

X-Ray Spectrometry

0.580

685

1

Journal of the American Society for Mass Spectrometry

0.575

697

Total = 91

 

 

 

Hot Papers

ESI establishes citation thresholds for hot papers, which are selected from the highly cited papers in different fields, but the time frame for citing and cited papers is much shorterpapers must be cited within 2 years of publication and the citations must occur in a 2-month time period. Papers are assigned to 2-month periods and thresholds are set for each period and field to select 0.1% of papers. There were no hot papers identified for the most recently completed 2-month period (i.e., September-October 2005), but there were nine hot papers identified from previous periods.

Using the current hot paper thresholds established by ESI as a benchmark, nine of the water quality papers, representing 1.1% of the water quality publications, were identified in the fields of Environment/Ecology and Multidisciplinary. The hot papers are listed in Table 11.

Table 11. Hot Papers Identified Using Current ESI Thresholds

Field

ESI Hot Papers Threshold

No. of Cites in 2-Month Period

 

Paper

Environment/ Ecology

7

9 cites in March-April 2003

Angradi TR, et al. Vegetation type and the intertidal macroinvertebrate fauna of a brackish marsh: Phragmites vs. Spartina. Wetlands 2001;21(1):75-92.

7

20 cites in November-December 2000

Van den Berg M, et al. Toxic equivalency factors (TEFs) for PCBs, PCDDs, PCDFs for humans and wildlife. Environmental Health Perspectives 1998;106(12):775-792.

8

13 cites in December 1996

Berry WJ, et al. Predicting the toxicity of metal-spiked laboratory sediments using acid-volatile sulfide and interstitial water normalizations. Environmental Toxicology and Chemistry 1996;15(12):2067-2079.

8

11 cites in December 1996

Hansen DJ, et al. Chronic effect of cadmium in sediments on colonization by benthic marine organisms: an evaluation of the role of interstitial cadmium and acid-volatile sulfide in biological availability. Environmental Toxicology and Chemistry 1996;15(12):2126-2137.

8

10 cites in December 1996

Hansen DJ, et al. Predicting the toxicity of metal-contaminated field sediments using interstitial concentration of metals and acid-volatile sulfide normalizations. Environmental Toxicology and Chemistry 1996;15(12):2080-2094.

7

10 cites in November-December 1996

Pesch CE, et al. The role of acid volatile sulfide and interstitial water metal concentrations in determining bioavailability of cadmium and nickel from contaminated sediments to the marine polychaete Neanthes arenaceodentata. Environmental Toxicology and Chemistry 1995;14(1):129-141.

8

9 cites in December 1996

Liber K, et al. Effects of acid-volatile sulfide on zinc bioavailability and toxicity to benthic macroinvertebrates: a spiked-sediment field experiment. Environmental Toxicology and Chemistry 1996;15(12):2113-2125.

Environment/ Ecology

6

6 cites in July-August 1997

Howarth RW. Regional nitrogen budgets and riverine N&P fluxes for the drainages to the North Atlantic Ocean: natural and human influences. Biogeochemistry 1996;35(1):75-139.

Multidisciplinary

6

7 cites in October-November 2001

Steidinger KA, Rublee PA. Heteroduplex mobility assay-guided sequence discovery: elucidation of the small subunit (18S) rDNA sequences of Pfiesteria piscicida and related dinoflagellates from complex algal culture and environmental sample DNA pools. Proceedings of the National Academy of Sciences of the United States of America 2000; 97(8):4303-4308.

Author Self-Citation

Self-citations are journal article references to articles from that same author (i.e., the first author). Because higher author self-citation rates can inflate the number of citations, the author self-citation rate was calculated for the water quality papers. Of the 10,234 total cites, 417 are author self-citesa 4.1% author self-citation rate. Garfield and Sher2 found that authors working in research-based disciplines tend to cite themselves on the average of 20% of the time. MacRoberts and MacRoberts3 claim that approximately 10% to 30% of all the citations listed fall into the category of author self-citation. Therefore, the 4.1% self-cite rate for the water quality papers is below the expected range for author self-citation.

1 Thomson's Web of Science provides access to current and retrospective multidisciplinary information from approximately 8,500 of the most prestigious, high impact research journals in the world. Web of Science also provides cited reference searching.

2 Garfield E, Sher IH. New factors in the evaluation of scientific literature through citation indexing. American Documentation 1963;18(July):195-201.

3 MacRoberts MH, MacRoberts BR. Problems of citation analysis: a critical review. Journal of the American Society of Information Science 1989;40(5):342-349.

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