Sediment acidification

Taylor, E.J., E.M. Rees, and D. Pascoe. 1994. Mortality and drift-related response of the freshwater amphipod Gammarus pulex (L.) exposed to natural sediments, acidification and copper. Aquat. Toxicol. 29 83-101. 

A parameterized model that includes the reversal of cation exchange and subsequent neutralization of released H+ is under development, but an estimate of the effects of sediment acidification (sediment cation or alkalinity deficit) on rate of recovery can be made by using the equations in Model 3 if the following assumptions are made. 

Finally, there is a potential for inhibition of sulfate reduction by sediment acidification in highly impacted sites. In the first two years of experimental acidification of Little Rock Lake there is no evidence of decreased pH in porewater 1 cm below the interface. It is not clear, however, whether sediment acidification will occur with further increases in acid loadings to the lake. Rudd et al. (fi) showed that porewaters from lakes Hovattn and little Hovattn were acidic at fall turnover and postulated that this may occur by oxidation of reduced sulfur compounds. Although sediments from 223 showed no evidence of acidification after 10 years of experimental lake acidification, the pH of porewater from Lake 114 declined by > 0.5 units after just three years of experimental acidification (fi). 

Relative to the impact of yeast on beer appearance and flavour as discussed above, information is scarce on the impact of bacteria on beer appearance and flavour. Bacteria mainly cause turbidity, sediments, acidification, off-flavour formation and ropiness (Sakamoto Konings, 2003 Suzuki, 2011 Suzuki et al., 2008). Suzuki (2011) and Vriesekoop, Krahl, Hucker, and Menz (2012) recently sununarised the positive and negative influences of bacteria on flavour and off-flavour in recent reviews, which form the basis of this section. Interested readers are referred to these articles for further details. 

Munthe J, Hultberg H, Lee Y-H, Parkman H, I verfeldt A, Renberg I. 1995a. Trends of mercury and methylmercury in deposition, run-off water and sediments in relation to experimental manipulations and acidification. Water Air Soil PoUut 85(2) 743-748. 

Pretreatment is necessary for the treatment of the food industry wastewater. Pretreatment options such as flow equalization and neutralization, screening, FOG separation, acidification, coagulation-flocculation, sedimentation, and DAF are available. Selecting the appropriate technology depends on the wastewater characteristics. 

Dickman, M. Fortescue, J. 1984. Rates of lake acidification inferred from sediment diatoms for eight lakes located north of Sudbury. Verhandlungen Internationale Vereinigung fuer Theoretische und Angewandte Limnologie, 22, 345-1356. 

The Critical concentrations with respect to the soil organisms should be related to a low effect level on the most sensitive species. The effects on the process of metabolism and other processes within the organisms should be considered and also the diversity of the species, which is most sensitive to the heavy metals, has to be accounted. Critical limits must refer to the chronic or accumulated effects. For assessment of the critical concentrations in crops and in drinking water, human-toxicological information is required. In general, for establishing critical loads we should also account the additive effects of the different metals and combination effect between the acidification and biogeochemical mobilization of the heavy metals in soils and bottom sediments. 

Of particular concern are the impacts of seawater acidification on biocalcification and the burial rates of sedimentary carbon. Carbonate ion concentrations in the surface waters have already declined by 16%. Thus, it is not surprising that the abundance of tropical/subtropic planktonic foraminiferan species appears to have declined since the 1960s. This information was obtained by studying the rapidly accumulating sediments of the Santa Barbara Basins off the coast of California. 

The last include wet and dry deposition of particles and solutes and gas exchange across the air-sea interface. Because of proximity to source, coastal waters tend to be more polluted than the open ocean. A notable exception is the worldwide acidification of surface waters caused by CO2 emissions. Of all the coastal waters, estuaries tend to be the most impacted. This is due to high rates of pollutant loading and to natural processes that act to concentrate these pollutants in the local sediments and biota. This is most unfortunate as estuarine waters support the world s largest fisheries and are where recreation is concentrated. 

Johnston AE, Goulding KWT, Poulton PR (1986) Soil acidification during more than 100 years under permanent grassland and woodland at Rothamsted. Soil Use Manage 2 3-10 Kahn SU (1982) Bound pesticides residues in soil and plant. Residue Rev 84 1-25 Kan AT, Chen W, Tomson MB (2000) Desorption kinetics from neutral hydrophobic organic compounds from field contaminated sediment. Environ Pollution 108 81-89 Kang SH, Xing BS (2005) Phenanthrene sorption to sequentially extracted soil humic acids and humans. Environ Sci Technol 39 134-140... 

Hydrogen sulfide is introduced into an ice-cooled solution of 0.2 mol of a 1,2-diketone and 0.02 mol of piperidine in 30 ml of dimethylformamide for 1 -4 hours. Elemental sulfur is precipitated during the introduction of hydrogen sulfide. The mixture is acidified with dilute hydrochloric acid the sediment is filtered with suction and dissolved in warm methanol the undissolved sulfur is separated, and the product is isolated by evaporation of the methanol and purified by crystallization. If the product after the acidification is liquid it is isolated by ether extraction and distillation after drying of the ether extract with sodium sulfate. Yield of benzoin from benzil after 1 hour of treatment with hydrogen sulfide is quantitative. 

This chapter summarizes water chemistry changes and effects of acidification on biogeochemical processes. We focus on major ions and nutrients, discuss internal alkalinity generation and sediment ion-exchange processes, and present preliminary recovery models. Results for trace and minor metals and other chemical constituents are presented elsewhere (2-4). 

Lake level could also influence silica levels. For example, the decline in lake level resulted in a large loss of surface area and decreased the amount of contact between lake water and sandy littoral areas that contain weath-erable silicate minerals. Rates of weathering are usually enhanced by acidification and would help to explain the interbasin differences observed at pH 4.7. However, weathering rates of LRL sediment are unknown (see Sediment Processes section). In addition, although the differences between the basins were significant, they were small (0.01-0.03 mg of Si02 per liter) and may be accounted for by small differences in hydrological factors. 

The pore-water profiles also indicate a possible treatment effect. In the treatment basin before acidification to pH 4.7, much higher levels of ANC (alkalinity) and higher pH were found in the pore water just 1-2 cm below the sediment-water interface (59). In contrast, pore-water pH profiles obtained in the same site in the summers of 1990 and 1991 show pH < 5.0 in the upper 5-10 cm of sediment. Corresponding profiles for a site in the reference basin did not show such a depression (Figure 6a ref. 4). 

The initial sediment alkalinity deficit (at the end of acidification or the beginning of recovery) is equal to the difference between the preacidification base-cation content of the water column and that measured at the end of acidification. This deficit can be treated as if it were a component of the water-column alkalinity. In other words, total alkalinity at the beginning of recovery, [ALK]T0, is equal to the sum of water-column alkalinity at that time, [ALK]0, and the difference between preacidification base-cation concentration and that at the beginning of recovery (t = 0). 

The alkalinity produced at the sediment-water interface by sulfate reduction will be distributed between the water column and sediment compartments in proportion to their alkalinity deficit. At the end of acidification in LRL, both the water column and the sediments (expressed in terms of excess cations in the water) had initial alkalinity deficits of 50 me-quiv/m3, and therefore generated alkalinity was assumed to be distributed equally. In other words, for every 2 mequiv of alkalinity produced, 1 mequiv contributes to water-column alkalinity and 1 mequiv to sediment alkalinity. 

Mass-balance calculations for the first 3 years of acid additions indicate that the principal IAG processes are sulfate reduction and cation production. Specifically, one-third of the total sulfate input (added acid and deposition) was neutralized by in-lake processes. Increased sulfate reduction consumed slightly more than one-sixth and production of cations neutralized somewhat less than one-sixth of the acid added. Of the remaining sulfate, one-third was lost by outflow, and one-third decreased lake alkalinity. Laboratory determinations suggest that sediment-exchange processes occurring in only the top 2 cm of surficial sediments can account for the observed increase in water-column cations. Acidification of the near-surface sediments (with partial loss of exchangeable cations) will slow recovery because of the need to exchange the sediment-bound H+ and neutralize it by other processes. Reactor-based models that include the primary IAG processes predict that... 

---