Bentonite, biotite, illite, kaolin, vermiculite and zeolite were acidified or alkalized with hydrochloric acid or sodium hydroxide at concentrations of 0.1, 1.0 and 5.0 mole dm−3 at room temperature for two weeks. In acid treatments, dissolution of Al prevailed over Si and the opposite was observed in alkali treatments. The XRD patterns showed severe alteration of the crystal structure after acid treatments, whereas sharpening of the XRD peaks after alkali treatments was observed. Illite and kaolin were most resistant to acid attack. with a few exceptions, the surface areas of the minerals computed from both water and nitrogen adsorption isotherms increased with acid and alkali treatments. with increasing reagent concentration, the nitrogen surface area increased faster than the water surface area. well-defined trends were not noted in either changes of average water or nitrogen adsorption energies or in relative amounts of adsorption sites, indicating that the effects of acid and alkali attack are controlled by the individual character of the minerals.

Bentonite, biotite, illite, kaolin, vermiculite and zeolite were treated with 0.1, 1.0 and 5.0 mol. dm−3 HCl or NaOH. Suspensions of Na homoionic forms of the initial and the treated minerals were back titrated with 0.1 mol. dm−3 NaOH. From back-titration data variable surface charge, QV, vs. pH dependencies and apparent surface dissociation constant distribution functions were estimated. Variable charge vs. pH curves were scaled against cation exchange capacity at pH 7.2 to obtain actual charge, QA, vs. pH plots. In general both treatments led to an increase of QV, while the QA value increased and decreased depending on the mineral and the treatment. Products of 5 mol dm−3 NaOH action on zeolite and of 1 and 5 mol. dm−3 NaOH on kaolin apparently developed a positive surface charge below pH ∼3.7 and below ∼4.3, respectively.

The heterogeneity of charge-generating surface groups was observed in natural minerals. During acid treatment, the number of weakly-acidic surface functional groups increased while the number of groups of stronger acidic character decreased. The opposite was found for alkaline treatment: the number of surface groups of intermediate acidity increased and that of low acidity decreased.

Bentonite, biotite, illite, kaolin, muscovite, vermiculite and zeolite were acidified or alkalized with HCl orNaOH of concentrations 0.0, 0.1, 1.0 and 5.0 mole dm−3 at room temperature for 2 weeks and converted into Ca homoionic forms. Low-temperature nitrogen and room-temperature water-vapor adsorption-desorption isotherms were used to characterize the mineral pores of radii between 1 and 30 nm. Nanopore volumes, size distributions, average radii and fractal dimensions were calculated. Values calculated from the nitrogen isotherms differed from those derived from water-vapor data. With an increase of the acid-treatment concentration, the pore volumes measured using both adsorption techniques increased markedly for all minerals. The pore radii measured from nitrogen isotherms appeared to decrease for all minerals except zeolite, while the pore radius calculated from water-vapor data increased in most cases. The fractal dimension measured from water vapor isotherms decreased in all cases indicating smoothing of the mineral surfaces and decrease in pore complexity. No well defined trends in any of the pore parameters listed above were noted under alkaline treatment. In the reaction of each mineral with acid and alkali treatments, the individual character of the mineral and the presence of impurities seems important.

Ocean warming and acidification are expected to influence the biology of the ecologically and economically important red king crab, Paralithodes camtschaticus. We investigated transcriptome responses of adult, larval and juvenile red king crab to assess sensitivity to reduced pH and elevated temperature. In adults, gill tissue (but not heart or cuticle) responded to reduced pH by differentially regulating many genes involved in metabolic, membrane and cuticular processes, but not ionic or acid/base regulation. In larval crabs, we found little evidence for a strong transcriptomic response to pH, but did observe large differences in the transcriptomes of newly hatched and one-week old larvae. In juvenile crabs, we found that there was a strong transcriptomic response to temperature across all pH conditions, but that only extreme low pH caused transcriptomic shifts. Most of the genes in juveniles that were differentially expressed were for cuticular and calcification processes. While inferences regarding the specific biological responses associated with changes in gene expression are likely to change as resources for red king crab genomics enabled studies continue to improve (i.e. better assemblies and annotation), our inferences about general sensitivities to temperature and pH across the life stages of red king crab are robust and unlikely to shift. Overall, our data suggest that red king crab are more sensitive to warming than acidification, and that responses to acidification at the transcriptomic level occur at different levels of pH across life stages, with juveniles being less pH sensitive than adults.

A commercial drinkable yogurt with and without 4% of added trehalose (as cell protectant) was spray-dried obtaining a powder with low water activity (aw). Total bacterial count in the powder was between 8.48–8.90 log cfu/g. The dried yogurt was stored: (i) at 38 °C and aw = 0.33; (ii) at 38 °C in hermetically sealed flasks (aw = 0.21/0.22); (iii) in a cyclic temperature chamber (10–20 °C) in hermetically sealed flasks (aw = 0.21/0.22). Whole milk was then fermented by adding an inoculum of spray-dried yogurt after storage under these different conditions. The kinetics of acidification showed the presence of a lag time which was strongly dependent on storage conditions. The data was fitted with a logistic type equation from which the lag time was calculated. To evaluate structural differences among samples, Fourier Transform Infrared spectra (FTIR) were recorded. Partial Least Squares (PLS) models enabled a good correlation between lag time of fermentation and FTIR spectra. The lag time for yogurt powder stored at aw about 0.21/0.22 and cyclic temperature 10–20 °C remained approximately constant over the 12 weeks of storage, while all the other conditions resulted in a dramatic increase. The addition of trehalose had a small influence on lag time and, therefore, as a protectant of lactobacilli.

In practice, obtaining radiocarbon (14C) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting 14C content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on 14C content of sedimentary OM, we examine the variability in 14C content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (RinseHCl) and HCl fumigation (FumeHCl)], we demonstrate that the two acid-treatments can affect 14C content differentially. Our findings suggest that, for low-carbonate samples, RinseHCl affects the Fm values due to loss of young labile organic carbon (OC). FumeHCl makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during RinseHCl, causing the Fm values of remaining OC to increase. FumeHCl can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix.

Echinoderms are vulnerable to ocean acidification because of their high magnesium calcite skeletons. Here, skeletal Mg/Ca ratios were examined within and between individuals of 20 Antarctic echinoderms representative of the asteroids, ophiuroids and echinoids. The highest mean Mg/Ca ratios occurred in the discs and arms (0.111 and 0.110, respectively) of brittle-stars and the lowest in the spines (0.010) of cidaroid sea urchins. Many taxa (11 of 14 species) from the collection sites showed no intraspecific differences in Mg/Ca ratios between given skeletal components. Exceptions were the spines of two regular sea urchins and the skeletal ossicles of the combined arms and disc of a brittle-star. The relationship between skeletal magnesium content and latitude was further evaluated and an inverse correlation was found between Antarctic echinoderm taxa skeletal magnesium content and latitude across 62° to 76°, indicating that the relationship occurs over relatively narrow latitudes. Upon examination of an even narrower range (70–76° latitude), a region where the mineralogy of echinoderm skeletons has not been investigated, the predicted inverse relationship between Mg/Ca ratio and latitude was still observed in sea-stars, but not in brittle-stars or sea urchins.

Efficient phosphorus (P) recycling from rural and urban areas is becoming an increasing issue due to the scarcity of natural P deposits. Based on a life cycle assessment (LCA), we analyzed the environmental performance of 17 different P supply and recycling approaches from urban wastes, biosolids and slaughterhouse wastes compared with the two conventional inorganic fertilizers phosphate rock and triple superphosphate. The results show that many recycled P fertilizers (RPFs; e.g., digestates from urban organic wastes, biosolids and their ashes, meat and bone meal (MBM) and its recycling products) are competitive in terms of LCA results compared with conventional P fertilizers. For each of the P recycling sources, one or more treatment options were identified, which have more favorable LCA results than the conventional references. For sewage sludge, we found that direct application of the stabilized biosolids, and incineration with application of the ash showed the lowest LCA impacts per kg P; their treatments even generated net credits from added values. The same applies for the anaerobic digestion treatment of urban organic wastes. For MBM, low environmental impacts were identified for each of the analyzed treatment options, especially for anaerobic digestion, incineration, feeding with application of manure and direct application. Similarly, low environmental impacts and net credits were found for directly applied biomass ash. Some organically based RPFs demonstrate added values, i.e., as nitrogen and potassium fertilizer effect, energy gains during the treatment, or a humus sequestration potential. If these added values are considered in the LCAs, 11 out of 17 RPFs will have advantageous effects for the majority of addressed impact categories.

The study aimed to unravel the interaction between ocean acidification and solar ultraviolet radiation (UVR) in Chaetoceros curvisetus. Chaetoceros curvisetus cells were acclimated to high CO2 (HC, 1000 ppmv) and low CO2 concentration (control, LC, 380 ppmv) for 14 days. Cell density, specific growth rate and chlorophyll were measured. The acclimated cells were then exposed to PAB (photosynthetically active radiation (PAR) + UV-A + UV-B), PA (PAR + UV-A) or P (PAR) for 60 min. Photochemical efficiency (ΦPSII), relative electron transport rate (rETR) and the recovery of ΦPSII were determined. HC induced higher cell density and specific growth rate compared with LC. However, no difference was found in chlorophyll between HC and LC. Moreover, ΦPSII and rETRs were higher under HC than LC in response to solar UVR. P exposure led to faster recovery of ΦPSII, both under HC and LC, than PA and PAB exposure. It appeared that harmful effects of UVR on C. curvisetus could be counteracted by ocean acidification simulated by high CO2 when the effect of climate change is not beyond the tolerance of cells.

A life-cycle assessment (LCA) was carried out to compare the environmental performance of different organic cropping systems with and without digestion of slurry and crop residues. The aims of the present study are: (1) to compare the environmental performance of organic farming dairy systems with the currently prevalent animal housing systems [solid farmyard manure (FYM) versus liquid slurry] as the main reference systems; (2) to analyze the effect of the implementation of a biogas digestion system on the consumption of fossil fuels and production of electrical energy; (3) to quantify the effects of the implementation of a biogas digestion system on the environment; and (4) to compare the obtained net energy yields with other means of obtaining energy by using the farmland area. The considered impact categories are greenhouse gas (GHG) balances, acidification, eutrophication and groundwater pollution. LCA results indicated that total emissions in systems based on FYM are much higher than in liquid slurry systems for most of the considered impact categories. The benefits of digestion of stable wastes in comparison with the reference system without digestion are mainly (1) the net reduction of the emissions of GHG and (2) energy recovery from produced biogas, while the disadvantages can be higher emissions of NH3 after spreading. The effects of additional biogas digestion of biomass such as crop residues (e.g., straw of peas and cereals) and cover crops are: (1) an optimization of the N-cycle and therewith higher yields; (2) higher energy production per unit arable land; (3) a further reduction of the GHG balance; but (4) higher N-related environmental burdens like eutrophication and acidification. The offsets of fossil fuel emissions were the largest GHG sink in most of the biogas digestion systems. The inclusion of a biogas plant into organic cropping systems and the use of the available wastes for production of energy largely increased the overall productivity of the farming system and matched very well the basic principles of organic farming such as a high self-sufficiency of the cropping system and reducing as much as possible the environmental impact of farming.

The pH-dependent behaviour of soluble protein aggregates produced by the pre-heating of reconstituted skim milk at 90 °C for 10 min was studied, in order to understand the role of these aggregates in acid gelation of heated milk. The following milk samples were prepared: (1) control (unheated reconstituted milk, pH 6·5); (2) milk heat-treated at pH 6·5 (mHtd6·5) and (3) milk heat-treated at pH 7·2 (mHtd7·2). They were centrifuged and the supernatants (SPNT 1) pH-adjusted to yield a series of pH values ranging from 6·5 or 7·2 to 4·6 using HCl at 20 °C or GDL at 20 and 38 °C. pH-Adjusted SPNTs 1 were re-centrifuged. The resulting supernatants (SPNTs 2) were analysed by OD (at 600 and 280 nm) and SDS-PAGE in order to characterise proteins still soluble as a function of pH. Particle size in SPNTs 1 was analysed by Steric Exclusion Chromatography. The OD600 nm revealed that during acidification soluble casein in both control and heat-treated samples exhibits variations in its optical properties or size as previously shown with micellar casein. In heat-treated samples, soluble casein and heat-induced covalent soluble aggregates precipitate at the same pH value. A progressive acidification of the soluble phase did not separate them. Increasing the temperature of acidification from 20 to 38 °C resulted in an increase in the precipitation pH of the proteins. However choice of acidifier did not have a significant effect on OD profiles. The soluble covalent aggregates from mHtd7·2 were smaller, more numerous, and had a higher content of κ-casein than mHtd6·5. Both types of aggregates began to precipitate at the same pH value but precipitation occurred over a narrower pH-range for soluble aggregates prepared from mHtd7·2. This may explain the higher gelation pH of mHtd7·2 compared with mHtd6·5.

Using the epilithic diatoms as indicators of environmental conditions, 10 lakes in the High Tatra Mountains were characterised with regard to their stage of acidification. The diatom communities were diverse; 210 taxa were found, including 27 species of north and alpine preference. On the basis of cluster analysis, two groups of lakes were distinguished. The first group included shallow, moderately acidified lakes (Dlugi and Zmarzly Gasienicowy lakes), where acidophilous organisms prevailed, with Achnanthes marginulata being the most numerous. The structure of the diatom community in Dlugi lake was stable over 4 years of observations and did not show any progress in acidification. The second group included mostly very deep, non-acidified lakes where circumneutral organisms prevailed, and among them Achnanthes minutissima was dominant in most cases. The diatom community structures mostly confirmed the status of the lakes studied as judged from their water chemistry.

Water chemistry and macroinvertebrates of four high mountain lakes (alt. 1657-1784 m) were investigated. The lakes areultraoligotrophic with naturally slightly acidic water. In three lakes these water level changed substantially during the year while in one it remained constant. Moreover, trophic status was higher in one than in the other three. Oligochaeta and Chironomidae dominated the invertebrate fauna of all lakes. Benthic faunal composition depended mainly on ecological factors such as substrate, trophic status, and hydroperiod. It appears that anthropogenic acidification has so far not affected faunal composition.

This study focuses on the effect of acidic water and aqueous aluminium on the monogenean ectoparasite Gyrodactylus salaris, infecting Atlantic salmon (Salmo salar) parr. G. salaris-infected salmon were exposed to various combinations of acidity and aluminium concentrations. The most pronounced effect was the elimination of parasites after 4 days when 202 μg Al/l was added to the water. The effect of aluminium was concentration dependent, but was relatively independent of pH (5·2, 5·6 and 5·9). At the lowest pH of 5·0 the effect of aluminium was enhanced. Acidic aluminium-poor water had no or minor effects on the G. salaris infections except at pH 5·0 where all parasites were eliminated within 9 days. The G. salaris populations increased exponentially in untreated control water. The results show for the first time that aqueous aluminium can, to a limited extent, have a positive effect on fish health. This study emphasizes that basic knowledge about abiotic environmental factors is of importance in order to understand the population dynamics, range extension and dispersal of ectoparasites such as G. salaris. Finally, our results suggest that aluminium treatment could form an effective disinfection method against ectoparasites in hatcheries and laboratories, as well as complementing the controversial rotenone treatments used against natural populations of G. salaris.

Contemporary phytoplankton and palaeolimnological studies were made of the algal response to acidification and liming in three lakes in Hälsingland, central Sweden (Njupfatet, Sjösjön, Djuptjärn). Surveys and experimental studies of the phytoplankton response to liming were undertaken at Njupfatet, together with an experiment designed to determine the possible role of lake sediments as an inoculum for any new species arriving in the water column. Liming had little quantitative or qualitative effect on the phytoplankton diversity at Njupfatet, but did result in the loss of the dominant contributor to algal biomass, Merismopedia tenuissima. None of the four new species recorded in the lake following liming was hatched from the sediment inoculum experiment. A freeze core from Njupfatet was dated by 210Pb and carbonaceous fly-ash particle profiles were also determined for Njupfatet and Sjösjön, which provided an approximate chronology for the latter lake. Diatom analyses were made of the three lakes and pH and dissolved organic carbon inferred using weighted averaging methodology. Njupfatet had no planktonic diatoms over the last 200–300 years, and was dominated by benthic diatoms, but the diatom-inferred pH suggests that the lake was acidified to pH < 5 prior to liming in 1989. Both Djuptjärn and Sjösjön were dominated by planktonic diatoms, and were acidifying from (c. 1970) prior to liming, Sjösjön from pH 6 to ∼ 5 and Djuptjärn from 6·5 to ∼ 5·5. These pH inferences suggest that at least some lakes in this region are susceptible to atmospheric acidification. The response of the diatoms to liming is discussed, in particular the rapid expansion at Njupfatet, of Cyclotella glomerata a diatom which was also present in Sjösjön for a period prior to acidification, and at other lakes in south-west Sweden. Possible reasons for the expansion of this small centric diatom are discussed.

Two sediment cores from acid lake Store Hovvatn were analysed for chironomid head capsule remains over a sequence spanning from about 1730 A.D. to the late 1970s. Up to 30 taxa were identified from one (0.5 cm) level in the cores. Principal component analysis of taxon relative abundances showed a gradient corresponding more or less to the sediment sample chronology. Redundancy analysis with some chemostratigraphical variables, and with pH values inferred from diatoms, indicated that chironomid community change could be explained as a response to acidification. However, most of the taxa that declined or disappearedup-core are known to occur in acid lakes and pH sensitivity per se does not seem to explain the response of individualspecies. The relative abundance of Orthocladiinae increased up-core and the long term change may be conceived in terms of a retarded productivity or oligotrophication. The most conspicuous change in the chironomid community appears to coincide with decreasing aluminium concentrations in the sediments and may indicate toxic effects from labile aluminium in the water column.

A description is given of the hydrological regime and associated surface water quality recorded at a multi-disciplinary long-term investigation into the effects of acid precipitation and afforestation. The study catchment at Loch Dee is situated on the margins of the Loch Doon granite complex in SW Scotland. Annual rainfall is in excess of 2200 mm. The three main tributary burns exhibit a rapid response to rainfall with a high percentage of direct runoff. The loch with an average volume of 3650 M1 and a contributing catchment area of 15·6 km2 has an average turn-over of approximately forty days but this has varied from 15 to 100 days. Local physical variations are shown to influence both hydrological response and surface water quality. Generally stream water during spate conditions reflects rainfall chemistry. Occasionally, however, moderately acid rainfall containing large concentrations of sea salts has produced highly acidic runoff through a process of ion-exchange within the surface horizons of the soils. The quality of base flows shows a spatial variation which reflects various lithologies to the extent that pH values ranging from 4·9 to 6·9 have been observed.

As part of the joint British-Scandinavian Surface Waters Acidification Programme, the Institute of Hydrology is establishing catchment studies in Scotland. Data from these catchment studies are being used to develop a range of models for investigating short-term and long-term changes in catchment acidity. Information on the modelling techniques available at the Institute of Hydrology is presented together with applications of the models to catchments in Scotland.

The nature of soil-water interactions is discussed in the context of both soil formation and drainage water chemistry. The interacting factors regulating drainage water chemistry are then briefly considered, including soil type and parent material, soil atmosphere CO2 concentration, hydrological pathways, soluble salts, topography, climate and biotic effects. Based upon these factors, some sites in NE Scotland thought to be highly susceptible to water acidification are examined, and the low pH of their waters is confirmed. The acidity trends of two superficially similar streams apparently less at risk are compared, and the differences explained in terms of sub-surface soil characteristics. The possible impacts of both afforestation and of acidifying pollutants on water pH are considered briefly where appropriate.