AFFECTED ENVIRONMENT - BIOTA

The overtly toxic materials present in the hydrosphere include biocides, industrial solvents, by-products of the petroleum industry, and heavy metals. Materials in the first three classes, most notably chlorinated hydrocarbons such as DDT and the PCBs, undergo only slow microbial degradation and are present in sufficient concentration in many aquatic environments to severely affect the biota. In favorable cases metals may be removed by deposition as in-... 

Environmental Problems—This section describes N Reactor operational activities that affected the environment. The affected environs are groundwater contamination (radionuclides, volatile organics, polychlorinated biphenyls (PCB), metals, and other Inorganics) soil contamination (surface and vadose zone contamination from radionuclides and organic compounds) biota contamination (flora [vegetation] and fauna [animals] from radionuclide uptake by plants or Ingestion by animals) and evaluated radiation at the Columbia River (unshielded sediments In the 1301-N Liquid Waste Disposal Facility). 

This section provides a description of environmental problems at the 100-N site linked to N Reactor operations. The operational activities affecting the environment are described first, followed by an assessment of the affected environments (groundwater, soil, and biota). The net effect of N Reactor operations on the environment is also included. 

Mercury is a toxic substance that, through human and natural activities, cycles through the atmosphere, hydrosphere, and ecosphere affecting the health of both humans and wildlife. It enters the environment naturally through erosion, fire, and volcanic processes, as well as a result of human industrial practices. The human activities such as combustion, smelting, and mining have elevated global mercury levels to approximately three times those found before industrialization. Once released, mercury persists in the environment where it circulates between air, water, sediments, and biota in various forms. Mercury is present everywhere in the environment. The level of Hg in air varies from 0.5 ng/m3 to 10 ig/m3. 

Moreover, both river induced up-welling and river discharge of nutrients create a fertile environment which enhances the primary production of organic matter in off-shore direction of estuaries. It can be predicted from these observations that heterogeneous reactions between dissolved and both mineral phase and biota will be predominant in estuaries and coastal zones. These reactions will primarily affect those elements and compounds which are located at the particulate surface. The determination of surface properties of particles appear to be an important key to understand the interactions of trace elements and organic compounds between particulate and dissolved phases in estuarine and coastal systems. 

The solubility of biogenic silica also is affected by its aluminum content. Van Bennekom et al. (1991) reported that the Al/Si atomic ratio in siliceous material collected from various marine environments varied from 0.6 X 10 to 7 X 10, with a corresponding change in silica solubility from 1,080 pM to 660 pM. The amount of aluminum incorporated into siliceous skeletons during growth appears to be dependent on the Al/Si ratio in the surrounding water as well as the particular species of siliceous biota. 

Using traditional methods of whole-water analysis, concentrations of these HCs are usually underestimated. Indeed, by these methods HCs may not even be detected, although they may occur on sediment at concentrations likely to have toxic effects on biota. The conventional approach for determining the concentration of HCs on suspended sediment is to analyze a whole-water sample and a filtered water sample and to assume that the difference between the two represents the fraction sorbed to suspended sediment. The major problem with this approach is that the amount of suspended sediment and associated contaminant in the whole-water sample may not be sufficient to produce a detection by whole-water analysis methods. This is particularly true if the suspended sediment concentration in the sample is small, as is generally the case for springs relative to surface water. For example, if a sample contains 50 mg/L of suspended sediment, and the sediment contains 300 pg/kg of polychlorinated biphenyls (PCBs) (a concentration likely to adversely affect biota health (Environment Canada, 1998)), the concentration of PCBs in the whole-water sample will be 0.015 pg/L. This concentration is well below most laboratory method detection limits—for example, the USGS National... 

The solubility of an organic compound in water is one of the key factors that affects its environmental behavior (.1—3). The aqueous solubility is a fundamental parameter in assessing the extent of dissolution of environmentally important substances and their persistence in an aquatic environment. The extent to which aquatic biota is exposed to a toxicant is largely controlled by the aqueous solubility. In addition, these solubilities are of thermodynamic interest in elucidating the nature of these highly nonideal solutions (1,2). 

However, as the material leaves the pipe and enters the ecosystem, it is almost immediately affected by both the biotic and abiotic components of the receiving system. All of the substrate and medium heterogeneity as well as the inherent temporal and spatial characteristics of the biota affect the incoming material. In addition to the state of the system at the time of pollution, the history of the environment as contained in the genetic makeup of the populations plus additional stressors in the past or present all impact the chemical-ecosystem interaction. The goal of the exposure analyses is to quantify the occurrence and availability of the stressor within the ecosystem. 

Birds are the most visible biota affected by oil spills, especially in the aquatic environment. Oil contaminates feathers when the birds come into contact with slicks on water or shorelines. For sea birds, this is particularly dangerous because when their feathers are oily, their insulation and buoyancy properties are decreased. Once oiled, a bird rapidly loses its body heat, especially at sea and this may cause death. Oiled sea birds may stay on land where their temperature loss is not as great. In doing so, however, they are away from their source of food and may die of starvation. 

The physical-chemical form of actinides entering terrestrial and freshwater environments from nuclear facilities may be different from refractory fallout of nuclear explosions. Source material possessing chemical characteristics different from refractory fallout can be expected to behave differently when released to the terrestrial and aquatic environments. Reaction of actinides with environmental media may also affect their availability to biota and long-term behavior in ecosystems. 

The retention or removal of ions, molecules, and compounds in the weathering and soil environment depends on the nature, strength, and abundance of the proton donors. The biota directly or indirectly affects the production of the proton donors. 

Biota. Biota are another means of dispersal of contaminants in the environment. When the material is biomagnified, such as the case with mirex, DDT, and PCB s and to a lesser extent with more polar compounds, botanical and zoological life can be affected and, as well, serve as a mode of dispersal. Chemical residues from the production plant have been found in fish in Spring Creek resulting in a warning by PA DER to avoid eating the fish. 

Zinc is an essential nutrient that is present in all organisms. Although biota appears to be a minor reservoir of zinc relative to soils and sediments, microbial decomposition of biota in water can produce ligands, such as humic acids, that can affect the mobility of zinc in the aquatic environment through zinc precipitation and adsorption (Callahan et al. 1979). 

Exposure has been defined as the concentration of toxic materials in space and time at the interface with target populations (Travis et aL, 1983). The respective parameters required for environmental hazard assessments relate to the spatial and temporal abundance of the contaminants in the various compartments of the ecosystem and hence their bioavailability. Reference environmental descriptions must include the biota exposed to the released chemicals and the hydrological, topographical, geological and meteorological characteristics of the environment that affect the transport and transformation of the contaminants. The key step in exposure assessment is the use of transport and transformation models to quantify the movement of contaminants from the source through the environment to the target populations. 

---