Natural acid ecosystem

In acid precipitation, the dominant strong acid anion is commonly sulfate. SO2, when entering the soil, is rapidly oxidized to SO3, and is therefore equivalent to an input of sulfuric acid. Sooner or later, the SO2 absorbed by plants also becomes S04 and enters the soil. Sulfur deposition therefore increases the sulfate concentration of the soil solution. In most natural acid ecosystems this anion is rare. 

This region is situated in the Malaysian peninsula, and the islands of Indonesia and New Guinea. The predominant ecosystems are Wet Equatorial Tropical Forest with Ferrasols. In accordance with the very intensive biogeochemical cycling (Cb < 0.1) and natural acid features of the soils, all components of ecosystems are very sensitive to actual and potential acidic deposition (Bashkin and Park, 1998). 

The primary purpose of the acid rain NOx emission reduction program is to reduce the adverse effects of acidic deposition on natural resources, ecosystems, visibility, materials, and public health by substantially reducing annual emissions of NOx- NOx emissions are a principal acidic deposition precursor. Although sulfate deposition is considered to be the major contributor to long-term aquatic acidification, nitric acidic deposition plays a dominant role in the "acid pulses" associated with the fish kills observed during the springtime meltdown of the snowpack in sensitive watersheds. 

These reactions can take place in both directions depending upon temperature, acidity, and the presence of other ions. Notice that when hydrogen ions (H ) are formed, they tend to make natural aquatic ecosystems slightly acidic. 

A variety of models have been developed to study acid deposition. Sulfuric acid is formed relatively slowly in the atmosphere, so its concentrations are beUeved to be more uniform than o2one, especially in and around cities. Also, the impacts are viewed as more regional in nature. This allows an even coarser hori2ontal resolution, on the order of 80 to 100 km, to be used in acid deposition models. Atmospheric models of acid deposition have been used to determine where reductions in sulfur dioxide emissions would be most effective. Many of the ecosystems that are most sensitive to damage from acid deposition are located in the northeastern United States and southeastern Canada. Early acid deposition models helped to estabUsh that sulfuric acid and its precursors are transported over long distances, eg, from the Ohio River Valley to New England (86—88). Models have also been used to show that sulfuric acid deposition is nearly linear in response to changing levels of emissions of sulfur dioxide (89). 

Ecological Effects studies to determine the nature or extent of air pollution and acid deposition to ecosystems. 

Why Do We Need to Know This Material Chapter 9 developed the concepts of chemical equilibria in gaseous systems this chapter extends those ideas to aqueous systems, which are important throughout chemistry and biology. Equilibria between acids, bases, and water in plant and animal cells are vital for the survival of individual organisms. To sustain human societies and protect our ecosystems, we also need these ideas to understand the acidity of rain, natural waters such as lakes and rivers, and municipal water supplies. 

In addition to climate change, the increased atmospheric concentration of C02 is likely to have wide-spread ecological effects in various environments, since C02 is a physiologically active gas, in plants as well as animals. The acidic nature of C02 will also lead to changes in the chemistry of the ocean s surface, which is in equilibrium with the atmosphere. Once the shift in the oceanic chemical balance becomes significant, it will affect ecosystems. It has been shown, for example, that doubling C02 concentration in the atmosphere will reduce the rate of calcium carbonate deposition in coral reefs by 30-40% (Langdon et al., 2000). 

Zinc ligands are soluble in neutral and acidic solutions, so that zinc is readily transported in most natural waters (USEPA 1980, 1987), but zinc oxide, the compound most commonly used in industry, has a low solubility in most solvents (Elinder 1986). Zinc mobility in aquatic ecosystems is a function of the composition of suspended and bed sediments, dissolved and particulate iron and manganese concentrations, pH, salinity, concentrations of complexing ligands, and the concentration of zinc (USEPA 1980). In freshwater, zinc is most soluble at low pH and low alkalinity 10 mg Zn/L of solution at pH 6 that declines to 6.5 at pH 7, 0.65 at pH 8, and 0.01 mg/L at pH 9 (Spear 1981). Dissolved zinc rarely exceeds 40 pg/L in Canadian rivers and lakes higher concentrations are usually associated with zinc-enriched ore deposits and anthropogenic activities. Marine... 

The maximum critical load for nitrogen acidity represents a case of no S deposition. The value of CLmaxN not only takes into account the nitrogen sinks summarized as CLminN, but consider also deposition-dependent denitrification as a denitrification fraction /de. Both sulfur and nitrogen contribute to acidification, but one equivalent of S contributes, in general, more to excess acidity than one equivalent of N, since nitrogen is also an important nutrient, which is deficient in the most natural ecosystems. 

Consequently, risk assessment process is the obligatory continuation of the process of quantitative calculation and mapping of critical loads of sulfur, nitrogen and acidity at various natural and agricultural ecosystems. This is connected with numerous uncertainties a priori included in the computer algorithm for CL calculations ... 

This study aims to calculate the critical loads of acidity, eutrophication and heavy metal (Pb, Cd) compounds in the vast area of Eurasia along the natural gas pipeline Yamal-West and quantitatively estimate the environmental risk at the surrounding ecosystems. The relevant research was conducted during 1994-2000 for total pipeline length (>3,000 km) including 21 gas pumping stations, from the northernmost part at the Yamal peninsula (north of West Siberia) up to the central western part of European Russia. 

The calculated values of critical loads for acid forming species of sulfur, and eutrophication and acid forming species of nitrogen, as well as species of heavy metals (Pb and Cd) characterize the sustainability of natural ecosystems surrounding the main... 

The calculation of exceedances testifies to the absence of excessive input of acidity for ecosystems surrounding the main natural gas pipeline Yamal-West Europe (Figure 6). 

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