CHAPTER ONE 1.1. Introduction Environmental sedimentology represents a relatively new sub disciplineof the earth sciences and, as such, the boundaries of the field are not clearlydefined. Herein we define environmental sedimentology as ‘the study of theeffects of both man and environmental change upon active surface sedimentarysystems’.
Consequently, environmental sedimentology can be regarded as thestudy of how both natural and anthropogenic inputs and events modify the productionand accumulation of the physical and biogenic constituents of recentsedimentary deposits. The field of environmental sedimentology has evolvedgradually over the past two decades, largely owing to an increased recognition ofthe influence that anthropogenic activities are exerting upon sedimentproduction and cycling. Studies in these areas reflect a need to address issuesof sedimentological change driven by environmental or land-use modification orcontamination (Perry and Taylor, 2007). Thecomposition of sediments that accumulate within individual sedimentaryenvironments is primarily a reflection of three main factors: 1- thesediment source;2- theprocesses of sediment transport and deposition, which determine whethersediment is retained or transported through a specific environment.3- the chemicalprocesses operating within the sediment or water column, for example, carbonateand evaporate precipitation, chemical diagenesis.
Thesediments in environment are originated from range wide sources are natural andanthropogenic. In terms of the initial supply of sediment into a sedimentarysystem, three basic sediment types can be delineated. These are: (i) detritalminerals, (ii) biogenic or organic sediments and (iii) anthropogenic particlesand compounds.1. Detrital minerals Detritalminerals, such as quartz and feldspar, along with heavy minerals, form aprimary component of many terrestrial and marine sediments.
These minerals areinitially released by weathering processes and are progressively eroded andtransported into, and through, a range of sedimentary environments. As aresult, initial mineralogical composition of the bedrock often influences therelative abundance of the individual minerals that are released. Suspendedsediments in the different tributaries have distinct mineralogical and magneticsignatures that demonstrate variations in the relative importance of different rockunits as sources for fluvial sediment. In reality, these detrital mineralsrarely undergo a simple source to sink transport route, but instead are subjectto numerous phases of weathering, transport, deposition, storage, lithification,reworking and redeposition (Perry and Taylor, 2007). 2.Biogenic and organic sediments Inaddition to detrital minerals, significant amounts of sediment are derived fromthe remains of skeletal carbonate-secreting organisms. These form across a widerange of marine environments (Schlager 2003), although marked latitudinalvariations occur both in the types and rates of biogenic sediment production(Lees 1975; Carannante et al. 1988).
Organic inputs, derived from plant material, can alsocontribute abundant material to sediment substrates.3. Anthropogenic particles and compounds Increasingly important in manysedimentary systems are inputs of anthropogenically sourced sediments. thesecontain on sediment grains that generated from anthorogenic origin (e.g.building material, industry) and sedimentary materials that have been heavilyimpacted by anthropogenic activity. In this environment, besides that theextrinsic sources such as soil and vegetation sources, sediment is sourced fromvehicle wear, building material, combustion particles and industrial material. Allof this material has chemical and mineralogical properties distinct from natural sediment grains and, as a consequence,interacts with the environment in a different manner.
Another significantcomponent of modern sediment, mostly absent from pre-industrial age sediments,are contaminants. Contaminants insediments have different forms including metals, inorganic elements, nutrients,organic compounds and radionuclides, and the major sources of thesecontaminants. Contaminant sources to sediments in the environment may be ofparticulate, dissolved or gaseous form, but for most contaminants theparticulate form is dominant (Horowitz, 1991; Perry and Taylor, 2007; Loganathan, 2013). 1.2. Sediments in urban environment Theurban environment is one that is of increasing importance globally, withimplications for both hydrological and sedimentological systems. Humanactivities played the role in the formation and characteristics of urban soils (Yangand Zhang 2015).
The focus on studying urban soils has progressively beenincreasing (Burghardt et al. 2015). The reasons being that in the past, only asmall proportion of the population lived in towns and most cities were small inmagnitude. Today, this situation is markedly different.
In 2000, about 47% ofthe world’s population lived in urban areas, and by 2050, that figure isprojected to be about 66% (Burghardt et al. 2015; Tume et al, 2017). The term urbansediment is commonly used and is used in a range of different contexts throughoutthe literature. In the past urban sediments has been a term commonlyused to refer to sediment accumulation on street surfaces. The study of urbansediments from the perspective of environmental sedimentology is a young one.Research into urban particulates originated out of concern for pollution andhuman health (Perry and Taylor, 2007). Guet al, 2016 stated that human activities related to economy and industry areusually more concentrated in cities, thus resulting that urban areas have alsobecame the geographic focus of resource consumption and chemical emissions,leading to problems such as environmental pollution. This is an important issuein developed and developing countries (Micó et al.
2006; Acosta et al. 2011; Liet al. 2013). The diversity of urban soils varies from soils that have stillremained unaffected from human impact to soils composed entirely of technogenicmaterials that do not occur naturally without human input (Norra, 2014). Similarly,the levels of contamination found in soils of urban systems vary from almostundiscernible to extremely high levels. There is also a wide range of bothorganic and inorganic contaminants found in urban soils. Currently, the metalsof most concern in urban soils includes lead (Pb), arsenic (As), barium (Ba),cadmium (Cd), cooper (Cu), mercury (Hg), nickel (Ni), and zinc (Zn) (Levin etal.
2017). All these potentially toxic elements (PTEs) may originate from manydifferent sources such as road-deposited sediment (RDS), industrial discharges(fossil fuel, agrochemical, mining, and smelters), aquatic urban sediments. andother activities (Tume et al, 2017).
Sediment and contaminant sources Sediments within urban environmentsoriginate from a wide range of sources, both natural and anthropogenic, where sedimentsources to subaerial environments (road-deposited sediments) and subaqueousenvironments (rivers, canals/docks and lakes). 1.2.1.
1. Road-deposited sediment (RDS) Compared with sediment in naturalenvironments, road-deposited sediment (RDS) has a wide, and diverse, range ofsources. Sources are either intrinsic to the road surface, which arepredominantly anthropogenic in nature, or extrinsic, which are predominantlynaturally derived are shown in Fig (1). Intrinsic sources include vehicleexhaust emissions, vehicle tyre and body wear, brake-lining material, buildingand construction material, road salt, road paint and pedestrian debris. (Murakami et al. 2005; Perry and Taylor 2007, Hopkeet al. 1980; de Miguel et al.
1997; Charlesworth et al. 2003; Sutherland 2003; Plazaet al, 2017). Extrinsic sources are soil material, plant and leaf litter, andatmospheric deposition. Pollutant levels in RDS have been studiedin different countries for heavy metals (Fergusson and Ryan 1984; Sutherlandand Tolosa 2000; Ho et al. 2003; Zafra-Mejía et al. 2013), polycyclic aromatichydrocarbons (Boonyatumanond et al. 2007; García-Flores et al.
2016), andnutrients (Vaze and Chiew 2004; Wakida et al. 2014). In urban areas, RDScontain high concentrations of heavy metals, and also, these areas play an importantrole on the accumulation of RDS, especially in areas with commercial andindustrial land use (Zhao et al. 2017). Road-deposited sediments have beenidentified as significant contributors to water and air pollution, because thesmall particles that are contained in RDS can be re-suspended by the wind ortraffic or transported to water bodies by storm water runoff (Sartor et al. Fig.
(1): Schematic illustration of the sources ofroad-deposited sediments (adapted from Taylor, 2007).1974; Thorpe and Harrison 2008). Harrison et al.(2012) stated that these latter particles contribute equally to the mass ofRDS. Road-deposited sediments have been identified also as a source ofpolycyclic aromatic hydrocarbons (PAH) in storm water (Brown and Peake 2006; Hwangand Foster 2006). Moreover, Hoffman et al.
(1984) calculated that 36%of PAH areintroduced to the environment by urban runoff. Heavymetals and hydrocarbons are considered to be the major contaminants in RDS. Heavymetal concentration has been widely used as an environmental pollutionindicator since the 1970s because of its effects on human health (Hamilton etal. 1984; Ubwa et al. 2013).
Some authors have reported that one of the mainfactors that determine heavy metal concentrations in RDS is land use. Theirfindings suggested that areas with residential and industrial land use havehigher concentrations of heavy metals than commercial areas (Sartor et al.1974; Herngren et al. 2006; Zhu et al. 2008; Duong and Lee 2011). In contrast, someother studies have reported that RDS from commercial land use had higherconcentrations of heavy metals and have associated these levels to trafficdensity (Ellis and Revitt 1982; Viklander 1998).
Zafra et al. (2016) identifiedthree physical factors involved in the accumulation of heavy metals in RDS. Thesefactors are climatic (rainfall, previous dry period, wind, and atmosphericdeposition), anthropogenic (land use, vehicles, and street cleaning), andmorphometric (particle size, trees, physical characteristics of the basin androofs).
They also stated that these physical factors can be associated with oneor more processes such as deposition, removal, interception, and suspension. Anothermain pollutant in RDS is total petroleum hydrocarbons (TPH). They are themeasurable gross quantity of petroleum-based hydrocarbons without identifyingtheir components individually (ATSDR 1999); it is also a term used to expressthe total concentration of nonpolar petroleum hydrocarbons in soil (Saari etal. 2008). TPH are also known as silica gel-treated n-hexane extractablematerial (SGTHEM), which is the remnant compound after the silica gel cleanupof hexane extracted material.
Petroleum hydrocarbons enter the environment byaccidents, leaks, spills, or by-products of domestic, commercial, andindustrial activities. TPH can become a risk to human health and to theenvironment (Yuan et al. 2007; Li et al.
2012). They can get into the humanbody through breathing, eating, or coming into direct contact with contaminatedsoil, water, or food, and can affect human health, depending on the compoundspresent in the different fractions of TPH (e.g., toluene, benzene). TPH foundin the soil are able to move to groundwater, where they can evaporate,dissolve, or move away to another area (McLinn and Rehm 1997; Sharma et al.
2000;Teng et al. 2013). The presence of TPH in different environmental matrices has beenstudied: soils (Adeniyi and Oyedeji 2001; Teng et al. 2013; Plaza et al, 2017), marine sediments (Botello et al.1991), biota (Fowler et al. 1993), and water (Reddy and Quinn 1999), but only afew studies have been conducted in RDS.
Also,the traffic emissions are significant sources for road deposited sediments(RDS), where traffic emissions are a significant contributor of diffusepollution loads on urban surfaces and subsequent mobilization and transporttowards the water bodies, aquifers and aquatic ecosystems, posing problems forreceiving water quality (Revitt et al. 2014; Shorshani et al. 2015). Part ofair pollutants deposits on surfaces by dry and wet processes, becoming availableto be entrained by the water runoff during rainfall events (Shorshani et al.
2015; Ferreira et al, 2016). Trafficpollutants can have distinct sources. They can be emitted by vehicles enginesthrough internal combustion, by tyre, clutch and brake wear, fuel evaporation,and road wear. Exhaust emissions are composed by carbon dioxide (CO2), carbonmonoxide (CO), nitrogen oxides (NOx/NO and NO2), volatile organic compounds(VOCs), particulate matter (PM), nitrous oxide (N2O), ammonia (NH3), persistentorganic pollutants (POPs) including polycyclic aromatic hydrocarbons (PAHs),and metals. Nonexhaust emissions are sources of particulate material (PM),which include inorganic species, trace metals and carbonaceous compounds (Shorshaniet al. 2015). Heavy metal ions are ubiquitous in modern industrialised environmentsand a matter of concern due to their toxicity and persistence that make themparticularly hazardous (Burges et al. 2015; Adamcová et al.
2016). Ofparticular concern are the processes of remobilisation and movement to thesoils and into the food chain, thereby reaching humans and causing chronic oracute diseases (Kadi 2009; Brevik and Sauer 2015). Roads can be major sourcesof heavy metals (Kadi 2009; Pant and Harrison 2013, Ferreira et al, 2016). Kadi(2009) states that the trace metal pollution sourced from the roads, where itsnearby agriculture soils, increasing their bio-accessibility. Paved road dustis the major source of air-born metal to the atmosphere (Kadi 2009; Pant andHarrison 2013), originated from exhaust pipe emissions, tyre wear, brake wear,road dust and surface wear (Pant and Harrison 2013). Road traffic isa key contributor of Ba, Zn and Pb (Lin et al, 2005 and Perez et al, 2010)found Cu, Sb, Ba, Mn and Zn in Barcelona (Spain). Tailpipe emissions are contributing to fine and ultrafine particles through non-exhaustemissions (Kumar et al.
2013). It is estimated that almost 90%of the total emissionsfrom road traffic will be originated by non-exhaust sources by the end of thisdecade (Rexeis andHausberger 2009). Brake and tyre wear, road surface abrasion,wear and tear/corrosion of other vehicle components such as the clutch, andresuspension of road surface dusts are different emissions types for non-exhaustPM (Pant and Harrison 2013).
Non-exhaust emissions are characterized by theirinherent toxicity including the tendency to act as carriers of heavy metals andcarcinogenic components (Hjortenkrans et al. 2007; Johansson et al. 2009).
Theyhave potential acute and chronic human health implications (Crosby et al.2014). Nonexhaust emissions are typically characterised by trace metals (e.g.Cu, Zn, Ba, Sb, Mn), known to vary with fleet composition, with heavy dutyvehicles being reported as having higher emissions (Grieshop et al. 2006;Mancilla and Mendoza 2012).
The profile of trace metal concentrations in nonexhaustPM is found to be unique for every region and varies with traffic volume andpattern, vehicle fleet characteristics, driving patterns and the climate andgeology setting for the region (Omstedt et al. 2005; Duong and Lee 2011). Sources of nonexhaust emissions present a widevariability given the diversity of tyre and break or road surface types andcomposition, many times manufacturer dependent, making it very difficult torelate source profiles to fleet composition (Pant and Harrison 2013). The relationshipbetween non-exhaust emissions and traffic characteristics is nonlinear, butseveral authors state that a relation with increase vehicle speed (Hussein etal. 2008; Mathissen et al.
2011). Rainfall rates are affected on the sedimentsemissions, were non exhaust emissions are greater than exhaust emissions, thesedue to its are low and the wash-off of the road is reduced (Amato et al.2010b). Emissions from traffic represent a substantial fraction of primary PMwithin urban areas (Charron et al.
2007). According to control regulations ledto reduce in exhaust emissions, but nonexhaust emissions from road vehicles arestill persistent. In several European cities, total emissions are an indicatorof exhaust and sources of exhaust, (Querol et al.
2004). Quantification ofnonexhaust particles and attribution to specific sources is difficult. Thorpeand Harrison (2008) stated that the quantification depends upon the use ofchemical tracers, which are seldom characterized. 126.96.36.199.
River, canal, dock and lake sediments Therange of sediment sources for rivers and canals is greater than that for RDS,in that as well as the input of RDS into river sediments, upstream anddownstream input of channel associated material is a major contributor to theseurban aquatic sediments. Collins & Walling, 2002 showedthat the sediment in the urban river sections was sourced from channel bankerosion (18–33%), uncultivated topsoil (4–7%), cultivated topsoil (20–45%), road-depositedsediment (19–22%) and sewage input (14–18%). The high contribution of urban sources(up to 40% sewage and RDS) illustrates the marked contrast of urban sedimentsto those in non-urbanized catchments.
This is in general agreement with Nelson& Booth (2002), who found that as well as landslides and channel bank erosion,15% of sediment in an urbanized catchment was from road surface erosion.Further such studies are required before a full appreciation of the relativecontribution of sediment and contaminant sources to urban rivers can be gained.As well as contaminant input from road runoff, increased levels of nutrients(especially phosphorus) and micro-organic pollutants (e.g.
pharmaceuticalproducts) are sourced from sewage treatment works (Owens & Walling 2002;Warren et al. 2003). Industrial processes are source for metal contaminants tourban rivers (Walling et al. 2003; Perry and Taylor, 2007). Comparedwith rivers, which receive sediment from a wide area, canal sediment iscommonly dominated by material that is more locally derived, as a result of thelimited transport of sediment in canals.
Industrial sources or sewage andnatural material are eroded from road surfaces and nearby land. canal and dock systems that have significantwater inputs from rivers, however, can have a significant sediment source fromoutside the system. For example, Qu & Kelderman (2001) showed thatsediment, and associated contaminants, in the Delft canals, The Netherlands, havebeen derived predominantly from the River Rhine, with the remainder coming fromurban and industrial sources. Urban docks and canals also commonly receive highlevels of organic matter, discharged from combined sewer overflows, andcontaminants derived from boat traffic, for example hydrocarbons and tributyltin (e.
g. Wetzel & Van Vleet 2003). Within urban lakes, sediment sourcesare generally a combination of both eroded soil materials from the surrounding catchmentand anthropogenic material from the urban environment. Atmospheric deposition mayalso be an important source of particulates and associated contaminants,especially for lakes with no direct river input (Charlesworth & Foster1999). Sediments deposited within lake systems are probably highly catchmentspecific and observations made cannot readily be applied to other urbancatchments (Charlesworth & Foster 1999). Aquatic systems have inputs ofheavy metals, that derived from natural and anthropogenic sources, it isdistributed between different compartments of ecosystems such as water andsediment. Estimates of the mobility and bioavailability are required tounderstand the risk posed to the environment by metals in sediments.
Riversediments is a major sink for heavy metals in the aquatic system, the chemicalprocesses such as precipitation, adsorption, and chelation used to remove themetals from the water. Sediments have different retention and leachingcapacities for metals owing to variation in properties. The metals entering or leaving the waterderived from the fine sediments, which it often referred to as suspendedparticulate matter (SPM). The particle size affected on The adsorption ofmetals from the water phase (Gibbs 1977; Horowitz and Elrick 1987; Ganne et al.
2006; Strom et al. 2011),