Particles in Surface Waters

In the foregoing discussions it has been implicit that advection and the Fickian mixing processes of diffusion and dispersion are responsible for the transport of dissolved chemicals. It is not necessary, however, for a chemical to be dissolved to be transported by these fluid processes chemicals that are adsorbed onto the surfaces of particles or absorbed into particles can also be readily transported by these processes. 

No matter what their origin, particles affect the transport of pollutants that are sorbed. Most of the discussion about advection and dispersion of dissolved chemicals in surface waters can also be applied to chemicals sorbed to suspended particles, provided that the time required for particles to settle out of the water is much longer than the time required for advection or mixing. 

The movement of particles, both as suspended sediment and as bed load, is of great importance to the evolution of river channels. The meandering of rivers (see Fig. 2-1) is an example of the physical effects of particle transport (Henderson, 1966 Reid and Wood, 1976). 

Suspended particles in surface waters are eventually either transported out of the water body (e.g., carried to the ocean by a river) or deposited on the bottom of the water body by settling. Settling is especially important in relatively quiescent waters, such as lakes, which typically have a relatively short life span (as measured in geologic terms) because they tend to fill in with 

To illustrate particle diffusion, consider a tall water-filled volume in which particles have settled until a steady-state vertical concentration profile has been attained. Under this steady-state condition, the downward flux density of particles must equal the upward flux density of particles at every depth. The downward flux density can be expressed as 

---

The role of transition metal oxide/hydroxide minerals such as Fe and Mn oxides in redox reactions in soils and aqueous sediments is pronounced (Stumm and Morgan, 1980 Oscarson et al., 1981a). These oxides occur widely as suspended particles in surface waters and as coatings on soils and sediments (Taylor and McKenzie, 1966). 

Zhuang, G. and Duce, R.A. (1993) The adsorption of dissolved iron on marine aerosol particles in surface waters of the open ocean. Deep Sea Res., 40, 1413-1429. 

High water velocities can result in erosion or corrosion due to the abrasive action of particles in the water and the breakdown of the protective film which normally forms on the inside surface of the pipe. Erosion can also result from the formation of flash steam and from cavitation caused by turbulence. Publishing data on limiting water velocities are in conclusive. Table 27.9 summarizes the available information. 

Endosulfan enters air, water, and soil when it is manufactured or used as a pesticide. Endosulfan is often applied to crops using sprayers. Some endosulfan in the air may travel long distances before it lands on crops, soil, or water. Endosulfan on crops usually breaks down within a few weeks. Endosulfan released to soil attaches to soil particles. Endosulfan found near hazardous waste sites is usually found in soil. Some endosulfan in soil evaporates into air, and some endosulfan in soil breaks down. However, it may stay in soil for several years before it all breaks down. Rainwater can wash endosulfan that is attached to soil particles into surface water. Endosulfan does not dissolve easily in water. Most endosulfan in surface water is attached to soil particles floating in the water or attached to soil at the bottom. The small amounts of endosulfan that dissolve in water break down over time. Depending on the conditions in the water, endosulfan may break down within 1 day or it may take several months. Some endosulfan in surface water evaporates into air and breaks down. Because it does not dissolve easily in water, only very small amounts of endosulfan are found in groundwater (water below the soil surface for example, well water). Animals that live in endosulfan-contaminated waters can build up endosulfan in their bodies. The amount of endosulfan in their bodies may be several times greater than in the surrounding water. More information on the chemical and physical properties of endosulfan can be found in Chapter 3. More information on its occurrence and fate in the environment can be found in Chapter 5. 

Figure 3. Time series of nitrate (Slagle and Heimerdinger 1991) and dissolved, particulate, and total in surface water at 47°N, 20°W (Atlantic Ocean) in April-May 1989. activity calculated as 0.0686 salinity (Chen et al. 1986). The production of biogenic particles during the bloom enhances the scavenging of Th, resulting in growing disequilibrium with time due to sinking of particles.

Kharkar DP, Thomson J, Turekian KK, Forster WO (1976) Uranium and thorium series nuclides in plankton from the Caribbean. Limnol Oceanogr 21 294-299 Krishnaswami S, Lai D, Somayajulu BLK, Weiss R, Craig H (1976) Large-volume in situ filtration of deep Pacific waters mineralogical and radioisotope studies. Earth Planet Sci Lett 32 420-429 Livingston HD, Cochran JK (1987) Determination of transuranic and thorium isotopes in ocean water in solution and in filterable particles. J Radioanal Nucl Chem 115 299-308 Masque P, Sanchez-Cabeza JA, Braach JM, Palacios E, Canals M (2002) Balance and residence times of °Pb and 4 o in surface waters of the northwestern Mediterranean Sea. Cont Shelf Res 22 2127-2146 Matsumoto E (1975) Th-234-U-238 radioactive disequilibrium in the surface layer of the oceans. Geochim Cosmochim Acta 39 205-212... 

Krishnaswami S, Sarin MM, Somayajulu BLK (1981) Chemical and radiochemical investigations of surface and deep particles of the In an Ocean. Earth Planet Sci Lett 54 81-96 Kroirfeld J, Vogel JC (1991) Uranium Isotopes in surface waters from southern Africa. Earth Planet Sci Lett 105 191-195... 

The sizes of charged and neutral particles were measured as a function of increasing temperature (Fig. 18) [178]. The thermal collapse of the PVCL particles turned out to be a more or less continuous process, regardless of particle charge and the presence or absence of amphiphilic grafts. The PEO chains bound to the particle surfaces had only a minor effect on the transition temperature. The sizes of the particles in cold water varied from sample... 

In general, silver concentrations in surface waters of the United States decreased between 1970-74 and 1975-79, although concentrations increased in the north Atlantic, Southeast, and lower Mississippi basins (USPHS 1990). About 30 to 70% of the silver in surface waters may be ascribed to suspended particles (Smith and Carson 1977), depending on water hardness or salinity. For example, sediments added to solutions containing 2 pg Ag/L had 74.9 mg Ag/kg DW sediment after 24 h in freshwater, 14.2 mg/kg DW at 1.5% salinity and 6.9 mg/kg DW at 2.3% salinity (Sanders and Abbe 1987). Riverine transport of silver to the ocean is considerable suspended materials in the Susquehanna River, Pennsylvania — that contained as much as 25 mg silver/kg — resulted in an estimated transport of 4.5 metric tons of silver to the ocean each year (USEPA 1980). The most recent measurements of silver in rivers, lakes, and estuaries using clean techniques show levels of about 0.01 pg/L for pristine, nonpolluted areas and 0.01 to 0.1 pg/L in urban and industrialized areas (Ratte 1999). 

Surfactants and their biotransformation products enter surface waters primarily through discharges from wastewater treatment plants (WWTPs). Depending on their physicochemical properties, surface-active substances may partition between the dissolved phase and the solid phase through adsorption onto suspended particles and sediments [1,2]. Several environmental studies have been dedicated to the assessment of the contribution of surfactant residues in effluents to the total load of surfactants in receiving waters. This contribution reviews the relevant literature describing the presence of linear alkylbenzene sulfonates (LASs) and in particular of their degradation products in surface waters and sediments (Table 6.3.1). 

The solid-water interface, mostly established by the particles in natural waters and soils, plays a commanding role in regulating the concentrations of most dissolved reactive trace elements in soil and natural water systems and in the coupling of various hydrogeochemical cycles (Fig. 1.1). Usually the concentrations of most trace elements (M or mol kg-1) are much larger in solid or surface phases than in the water phase. Thus, the capacity of particles to bind trace elements (ion exchange, adsorption) must be considered in addition to the effect of solute complex formers in influencing the speciation of the trace metals. 

---