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Bibliographical Research

2.7. Sediment quality assessment

Surficial sediment contamination due to various anthropogenic activities has been a cause of serious concern in recent times. Primary contaminants possessing critical issues to the global sediment flux constitute various nutrients and heavy metals, accumulated due to heavy dis- charge of effluents (majorly industrial, agricultural and domestic wastewater) into the aquatic ecosystem (Syvitski et al. 2005; Ouyang et al. 2006; Zhang et al. 2007b; Azhar et al.

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2015; Dhamodharan et al. 2019). These nutrients and heavy metals have typical characteris- tics of being persistent and thus, do not deteriorate or decompose with time, thereby making them toxic when concentrations exceed permissible limits. Furthermore, these compounds have less mobility in water columns. Therefore, their continuous accumulation in the natural water systems forces them to precipitate on the waterbody's sediment column. This makes the sediment columns of the water bodies potential sources of heavy metals, where they can be released back into the water columns or the aquatic flora and fauna via natural or anthro- pogenic ways, thus joining the food-chain system (Yin et al. 2011; Dhamodharan et al. 2019).

Additionally, lakes and wetlands play pivotal roles in providing nutrients to living organ- isms. Therefore, their bottom sediments are sensitive indicators to determine the pollution loadings as they act as both sources and sinks for the contaminants in an aquatic environment (Varol 2011; Yin et al. 2011). This necessitates their continuous monitoring and assessment.

Various aspects covering the pollution of sediments have been studied in the recent past.

A detailed literature review is inevitable to understand better the studies carried out on sed- iment contamination. Hence, following the procedure of scientific bibliometric analyses, as described in Section 2.6, the following keywords were entered in Scopus:

TITLE-ABS-KEY ("sediment contamination”) AND TITLE-ABS-KEY (“heavy metals” OR


Since the primary contaminants contributing to the sediment contamination in a natural aquatic ecosystem are nutrients and heavy metals, we restricted our search to these two pa- rameters. Similar procedures were adopted for extracting the final set of published literature (a total of 428 articles were finally extracted and subjected to analyses). Only in this case, the subject areas were limited to Environmental Science, Agricultural and Biological Sciences, Earth and Planetary Sciences, and Engineering. The results obtained are discussed in the fol- lowing sub-sections.

2.7.1. An overview of the literature sample

The 428 articles considered for the final analyses were arranged to their year of publication, as shown in Fig. 2. 11a. It was observed that the majority of the works have been carried out in the 2010s, i.e., from 2010 onwards. This indicates the growing popularity among research- ers worldwide in the domain of sediment contamination. This domain is also relatively fresher, as much emphasis had not been given to this particular domain in the past. Hence, a broad scope of research in this domain is believed to impact sediment contamination dynam- ics significantly.




Fig. 2. 11. An overview of literature sample related to sediment contamination; (a) Yearly publications, and (b) Classification of documents based on the respective subject areas (Data extracted from the Sco- pus database).

0 5 10 15 20 25 30 35

1975 1980 1985 1990 1995 2000 2005 2010 2015 2020

Number of Published articles

Year of Publication

Environmental Science


Agricultural and Biological

Sciences 23%

Earth and Planetary Sciences


Engineering 2%

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Furthermore, the articles have been divided as per the subject areas under the scope of this thesis. It was observed that more than half of the articles fell under the Environmental Science sphere, followed by Agricultural and Biological Sciences, Earth and Planetary Sciences (Fig. 2. 11b). This is suggestive of the dominance of Environmental Science in the domain of sediment contamination domain.

2.7.2. Journal Sources

Details of the journal sources actively involved in publishing articles related to sediment con- tamination are shown in Fig. 2. 12 and Table 2. 6. Journals having published at least five arti- cles and having a minimum of 20 citations have been considered for the analyses. This re- sulted in 21 out of a cumulative of 148 journals. It was observed that Marine Pollution Bulletin, Environmental Monitoring and Assessment, Science of the Total Environment, Environmental Science and Pollution Research, and Chemosphere are the most productive, with at least 15 publications in this domain of research. However, when it comes to the journals having the maximum impact, Environmental Monitoring and Assessment (13.68), Environmental Earth Sciences (13.61), Environmental Geochemistry and Health (10.46), Ecotoxicology and Environ- mental Safety (6.57), and Environmental Geology (5.67) displayed the highest average normal- ized citation scores. Thus, it may be stated that the journal of Environmental Monitoring and Assessment is both highly productive and possesses the highest impact, thus having a signifi- cant contribution to the research in the domain of sediment contamination.

Fig. 2. 12. Journal sources in the domain of sediment contamination.


Table 2. 6. Journals actively publishing articles related to sediment contamination.

Source Docu-


Cita- tions

Avg. Ci- tations


Cita- tions



Cita- tions

Marine Pollution Bulletin 36 1804 50 44.15 1.23

Environmental Monitoring and Assess-

ment 27 802 30 369.42 13.68

Science of the Total Environment 23 916 40 34.36 1.49

Environmental Science and Pollution

Research 18 302 17 22.74 1.26

Chemosphere 17 1066 63 32.03 1.88

Ecotoxicology and Environmental Safety 13 402 31 85.43 6.57 Environmental Geochemistry and

Health 13 199 15 135.95 10.46

Environmental Geology 9 267 30 51.01 5.67

Journal of Great Lakes Research 9 287 32 6.52 0.72

Journal of Soils and Sediments 9 126 14 5.42 0.60

Environmental Earth Sciences 8 132 17 108.90 13.61

Water, Air, and Soil Pollution 8 235 29 7.37 0.92

Estuarine, Coastal and Shelf Science 7 362 52 9.12 1.30

Marine Environmental Research 7 309 44 10.41 1.49

Archives of Environmental Contamina-

tion and Toxicology 6 87 15 4.37 0.73

Catena 6 113 19 6.45 1.08

Environmental Pollution 6 298 50 6.48 1.08

International Journal of Environmental

Science and Technology 5 54 11 2.67 0.53

Lakes and Reservoirs: Research and

Management 5 183 37 4.20 0.84

Soil and Sediment Contamination 5 84 17 3.13 0.63

Water Research 5 205 41 6.05 1.21

2.7.3. Co-occurrence of keywords

For the keyword analyses, a criterion minimum of 10 occurrences was set. This resulted in 14 out of a total of 1099 registered keywords. However, specific keywords were repetitive, which were omitted from the list. The final list contained 12 keywords, the details of which may be seen through Fig. 2. 13 and Table 2. 7.

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Fig. 2. 13. Analysis of author keywords.

Table 2. 7. Details of occurrences of author keywords.

Keyword Occurrences

heavy metals 129

sediment contamination 75

sediment 44

metals 31

pollution 19

enrichment factor 15

trace metals 15

water quality 15

contamination 12

geoaccumulation index 12

risk assessment 11

mercury 10

It was observed that both Table 2. 7 and Fig. 2. 13 displayed consistent results, with terms like “heavy metals”, “sediment contamination”, and “sediment” being the most frequently used, as is evident from the nodal size of the map. Based on the different clusters of author key- words, certain vital conclusions can be made, as follows:

Sediment contamination is associated with water quality: This is evident from the fact that the term “water quality” lies in the same cluster as “mercury”, “metals”, “pollution”, and


“sediment”, Also, it shares a reasonable intra-cluster association with “heavy metals” and

“sediment contamination”.

Works on sediment indices: Indices are the easiest and the most convenient method of an- alysing any dataset. Like water quality indices, certain sediment factors and indices help assess an aquatic ecosystem's sediment quality in continuous monitoring programs. These include the Enrichment factor and the Geo-accumulation index. The use of these keywords suggests comprehensive monitoring programs being carried out to understanding sedi- ment contamination lately.

Assessing the risks associated with the sediment column: The third kind of study involves assessing different risks related to sediment contamination. These risks are primarily of two types; (a) human health risks and (b) ecological risks. The human health risks associ- ated with the sediment column are primarily due to their exposure to different conditions and levels. In contrast, ecological risks are related to the impact of one or more elements on the ecology of a particular study area.

More studies on heavy metals compared to nutrients: It was observed that the quantum of studies on sediment contamination relating to heavy metals is much higher as compared to nutrient contamination. This may be attributed to more significant impacts of heavy metals on the aquatic ecology in contrast to nutrient contamination.

2.7.4. Co-authorship analysis

A minimum criterion was set for conducting the co-authorship analyses; authors should have at least three documents and 30 citations under their name. 22 authors out of a total of 1700 met the threshold limit, the details of whom are listed in Table 2. 8. A detailed classification of the researchers working on sediment contamination worldwide is shown in Fig. 2. 14. The 22 authors have been categorized into six independent clusters, based on their relative close- ness in research, for example, cluster 2 containing Capello M., Cutroneo L., and Vagge G. Table 2. 8 shows that Karbassi A.R. is the most productive researcher, followed by Zhang L., Delvalls T.A., and Wildi W. All these researchers are among the most productive with more than 3 ar- ticles to their name.

However, when it comes to the most influential authors, Liu L., Zhang L., and Liu J. are among the top influential researchers with average normalized citation scores of more than 2.00. Thus, it may be concluded that Zhang L. is among the most productive and influential researchers in the domain of sediment contamination. All the authors were also found to be highly collaborative, as is visualized from the density of the nodal connectors (Fig. 2. 14).

Bibliographical Research Chapter | 2 Indian Institute of Technology Guwahati Page | 49 Fig. 2. 14. Co-authorship mapping in the domain of sediment contamination.


Table 2. 8. Co-authorship details in the sediment contamination research.

Author Documents Citations Avg. Cita- tions

Norm. Cita- tions

Avg. Norm.


Karbassi A.R. 6 308 51 9.77 1.63

Zhang L. 5 540 108 16.04 3.21

Delvalls T.A. 4 226 57 5.39 1.35

Wildi W. 4 273 68 6.40 1.60

Abessa D.M.S. 3 140 47 3.85 1.28

Capello M. 3 30 10 2.67 0.89

Cutroneo L. 3 30 10 2.67 0.89

Forja J.M. 3 154 51 3.95 1.32

Goretti E. 3 70 23 4.27 1.42

Ismail A. 3 71 24 2.85 0.95

Johnston E.L. 3 55 18 2.17 0.72

Liu J. 3 175 58 6.76 2.25

Liu L. 3 171 57 10.80 3.60

Loizeau J.-L. 3 215 72 4.91 1.64

Martin C.W. 3 146 49 4.01 1.34

Marvin C. 3 84 28 1.98 0.66

Marvin C.H. 3 124 41 1.98 0.66

Painter S. 3 160 53 2.99 1.00

Pereira P. 3 32 11 2.12 0.71

Riba I. 3 145 48 3.06 1.02

Selvaggi R. 3 70 23 4.27 1.42

Vagge G. 3 30 10 2.67 0.89

2.7.5. Articles’ citations

The most influential articles in the sediment contamination domain were analysed in VOSViewer; the mapping result is shown in Fig. 2. 15. Only the articles with a minimum of 100 citations were considered for the analyses, resulting in 23 out of 428 filtered articles.

The most cited article was Schnoor et al. (1995), who demonstrated the use of vegetation in improving the quality of soils and sediments from hazardous wastes. The authors pre- sented the various aspects of phytoremediation, including its pros and cons. It is also the most influential article, with an average normalized citation score of 9.68. Loska & Wiechuła (2003) and Singh et al. (2005c) provided insights into pollution source identification using multivar- iate statistical techniques. Other research articles primarily focused on the factors and indices for heavy metal contamination in the sediment columns of different water bodies (Zhang et

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al. 2007a; Christophoridis et al. 2009; Zahra et al. 2014a). Also, it was observed that relatively newer articles have a higher average normalized impact score, thus indicating the significance of their research in a lesser duration (Table 2. 9).

Fig. 2. 15. Science mapping of the most influential publications in the domain of sediment contamina- tion.

Table 2. 9. List of highly cited publications in the domain of sediment contamination.

Document Citations Norm. Citations

Schnoor et al. (1995) 746 9.68

Loska and Wiechuła (2003) 523 6.60

Zhang et al. (2007a) 337 6.71

Zahra et al. (2014b) 292 7.33

Long and Chapman (1985) 283 1.74

Christophoridis et al. (2009) 231 5.68

Zheng et al. (2008) 213 3.89

Miller (1997) 198 5.22

Dauer et al. (2000a) 189 3.02

Karbassi et al. (2008) 189 3.45

Fernandes et al. (2007) 161 3.21

Yang et al. (2012) 158 5.60

Huang et al. (2017) 146 8.80

Maltby et al. (1995) 145 1.88

Cearreta et al. (2000a) 139 2.22

Singh et al. (2005b) 126 4.21

Borg and Jonsson (1996) 106 2.73

Wildi et al. (2004) 106 2.29


Dauvalter and Rognerud (2001) 105 2.69

Warren (1981) 104 1.00

Brady et al. (2015) 103 5.37

Hu et al. (2013) 101 3.85

Romano et al. (2004) 101 2.18

2.7.6. Countries active in sediment contamination research domain

A detailed analysis of the countries actively participating in the research on sediment con- tamination has been carried out in VOSViewer. Countries that have produced at least 10 arti- cles and possessing 30 citations have been considered for the analysis. 14 countries out of a total of 81 countries met the threshold limit. Fig. 2. 16 provides the scientific mapping of the countries involved, while Table 2. 10 provides the details, including all the statistical and re- search computations. Interestingly, all 14 countries have been classified into four independ- ent clusters based on the relative closeness of their respective research domain (Fig. 2. 16).

Fig. 2. 16. Countries active in the domain of sediment contamination.

The major contributing country in this particular domain has been the United States, fol- lowed by China, Italy, France, Australia, Spain, and Canada. All these countries have at least 20 published works under their name, thereby making them the most productive. However, when it comes to the most impactful countries, China, India, United States, Spain, and Iran have the highest average normalized scores (more than 1.00).

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Table 2. 10. List of countries proactive in research on sediment contamination.

Country Documents Citations Avg. Cita- tions

Norm. Cita- tions

Avg. Norm.


United States 59 2935 50 68.83 1.17

China 38 1773 47 65.08 1.71

Italy 36 614 17 35.09 0.97

France 24 563 23 18.87 0.79

Australia 22 556 25 16.27 0.74

Spain 21 830 40 23.03 1.10

Canada 21 720 34 12.94 0.62

United Kingdom 19 613 32 14.20 0.75

India 18 444 25 23.54 1.31

Germany 17 420 25 14.11 0.83

Brazil 17 250 15 13.40 0.79

Poland 16 727 45 15.59 0.97

Portugal 15 436 29 13.82 0.92

Iran 14 414 30 14.76 1.05

2.7.7. Qualitative Discussion related to sediment contamination – Current research topics

The sediment contamination studies have come a long way from the studies that used to be carried out during the initial days. A pattern-wise distribution of the related studies has been presented here through the following points.

a. Assessing the spatial distribution of contamination levels in bottom sediments

From the late-1970s till the mid-1990s, studies suggested a more comprehensive approach in determining the spatial distribution of various contaminants, especially heavy metals in the bottom sediments of both freshwater and marine environment (Griggs & Johnson 1978;

Hiraizumi et al. 1978; Fallon & Horvath 1985; Schults et al. 1987; Fuge et al. 1989; Chan-Won et al. 1990; Fuller et al. 1990; Lewandowski & Szczepanska 1993; Borovec 1994; Dauvalter 1994; Joksas 1994). Various factors such as grain size distribution of the sediment column hydrological aspects were associated with the pattern of heavy metal distribution (Hiraizumi et al. 1978; Hoover 1988; Roper et al. 1988; Marron 1989). The pattern then shifted from simply finding out the spatial distribution to source identification through the use of various statistical and data-reduction techniques (DelValls et al. 1998; Galvez-Cloutier & Dubé 1998b), understanding the toxicity assay (Gupta & Karuppiah 1996; Hartwell et al. 1998), and determining their elemental composition (Galvez-Cloutier & Dubé 1998a).


b. Associations between macrobenthic communities

As the years progressed and with the arrival of the 21st century, the focus shifted to correlat- ing the various aspects of sediment contamination, such as water pollution, watershed man- agement, anthropogenic activities monitoring, etc. (Camusso et al. 2000; Cearreta et al.

2000b; Dauer et al. 2000b; Lau 2000; Lau & Chu 2000; Martin 2000). Furthermore, attempts were made to establish a significant correlation between different ecological components, such as plant-sediment (Dauer et al. 2000b; St-Cyr & Campbell 2000; Marín-Guirao et al. 2005;

Carter et al. 2006; Apitz et al. 2007; Ozdilek et al. 2007), fish-sediment (Isidori et al. 2004; Diz 2005; Hallare et al. 2005; Mayer et al. 2008; Cooper et al. 2009) and water-sediment (Dauer et al. 2000b; Dauvin 2008; Poté et al. 2008; Zheng et al. 2008; Teodorović 2009).

c. Indexing approach to assessing sediment quality

With increasing contamination levels of the sediment columns of the aquatic ecosystems, con- tinuous monitoring programs became inevitable to understand the spatio-temporal variabil- ity. This resulted in massive datasets, which eventually became difficult to infer. Hence, re- searchers worldwide postulated different indices, which made the readability easy and saved considerable time. Some of the significant indices include the Geoaccumulation index (Igeo), contamination factor (CF), pollution load index (PLI), etc. Various studies have been carried out in the recent past incorporating these indices in determining the pollution levels of the sediment columns of different aquatic ecosystems (Calace et al. 2008; Christophoridis et al.

2009; Sheela et al. 2012; Ferati et al. 2015; El Azhari et al. 2016; Alves et al. 2018; Dietrich et al. 2018; Reis et al. 2019; Siddiqui & Pandey 2019; Ustaoğlu & Tepe 2019; Arienzo et al. 2020;

Dharmendra et al. 2020; Samanta et al. 2020; Yeh et al. 2020).

d. Speciation and risk assessment studies

Various aspects covering the pollution of sediments have been studied in the past. These in- clude spatial distribution of the contaminants, health risk assessment and pollution source identification through various statistical tools such as factor analysis, cluster analysis, corre- lation analysis and geostatistical analysis employing GIS (Maas et al. 2010; Sun et al. 2010;

Mohamed et al. 2014; Luo et al. 2015; Qing et al. 2015; Liu et al. 2016; Chen & Lu 2018). It has been observed that an unpolluted environment makes the heavy metals get attached to the sediment columns in the form of silicates and minerals. However, anthropogenic conditions force these heavy metals to occur in the form of liable fractions such as oxides, carbonates, sulphides, hydroxides, etc. (Pandey et al. 2015). Thus, various sequential extraction proce- dures (SEP) for surficial sediment have been developed and accepted widely for determining the speciation of heavy metals and the form in which they are present. Various forms in which

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the heavy metals may be present in the environmental conditions include exchangeable frac- tion (F1), bound to carbonate fraction (F2), bound to Fe/Mn Oxides (F3), bound to organic matter/ sulphate (F4) and residual fraction (F5) (Tessier et al. 1979; Sutherland 2010). How- ever, various complications and human errors persist while performing these experiments, as a result of which total metal concentrations usually assess the pollution status of a partic- ular water body (Duodu et al. 2016; Villanueva & Ibarra 2016; Vu et al. 2017). Studies per- taining to various risks associated with sediment contamination have also been conducted.

This includes both human health risks due to increasing exposure levels and potential ecolog- ical risks, which provides an idea regarding the cumulative effects of various heavy metals on the overall ecology of the surrounding ecosystem (Li et al. 2017; Soliman et al. 2018; Hamza et al. 2019; Huang et al. 2019; Rasool & Xiao 2019; Tokatli 2019; Bąk et al. 2020; Islam et al.

2020c; Khaled et al. 2020; Varol 2020a; Yeh et al. 2020; Zhu et al. 2020).

2.8. Anthropogenic influences on aquatic ecology and their model-