Surface Water pH Research Articles

Divergent drivers of carbon dioxide and methane dynamics in an agricultural coastal floodplain: Post-flood hydrological and biological drivers

Many coastal floodplains have been artificially drained for agriculture, altering hydrological connectivity and the delivery of groundwater-derived solutes including carbon dioxide (CO2) and methane (CH4) to surface waters. Here, we investigated the drivers of CO2 and CH4 within the artificial drains of a coastal floodplain under sugarcane plantation and quantify the contribution of groundwater discharge to CO2 and CH4 dynamics over a flood event (290mm of rainfall). High temporal resolution, in situ observations of dissolved CO2 and CH4, carbon stable isotopes of CH4 (δ13C-CH4), and the natural groundwater tracer radon (222Rn) allowed us to quantify CO2, CH4 and groundwater dynamics during the rapid recession of a flood over a five day period. Extreme super-saturation of free CO2 ([CO2*]) up to 2,951μM (25,480% of atmospheric equilibrium) was driven by large groundwater input into the drains (maximum 87cmday−1), caused by a steep hydraulic head in the adjacent water table. Groundwater input sustained between 95 and 124% of the surface [CO2*] flux during the flood recession by delivering high carbonate alkalinity groundwater (DIC=10,533μM, ~pH=7.05) to acidic surface water (pH <4), consequently transforming all groundwater-derived DIC to [CO2*]. In contrast, groundwater was not a major direct driver of CH4 contributing only 14% of total CH4 fluxes. A progressive increase in CH4 concentrations of up to ~2400nMday−1 occurred as a combination of increased substrate availability delivered by post-flood drainage water and longer residence times, which allowed for a biogenic CH4 signal to develop. The progressive enrichment in δ13C-CH4 values (−70‰ to −48‰) and increase in CH4 concentrations (46–2460nM) support coupled production-oxidation, with concentrations and δ13C values remaining higher (2,798nM and -47‰) than pre-flood conditions (534nM and -55‰) three weeks after the flood. Our findings demonstrate how separate processes can drive the aquatic CO2 and CH4 response to a flood event in a drained coastal floodplain, and the key role groundwater had in post-flood [CO2*] evasion to the atmosphere, but not CH4.

Surface water quality monitoring of an agricultural watershed for nonpoint source pollution control

Water pollution is a major environmental problem in the United States. To improve the surface water quality of the 2,493 ha (6,160 ac) Coulee Baton watershed in Louisiana, a collaborative nonpoint source pollution control study was initiated in 2004. Conservation measures and best management practices (BMPs) including cross-fencing of pasturelands (726.9 m [2,385 ft]), irrigation land leveling (12.9 ha [32 ac]), grade stabilization structures (two), irrigation water pipeline (975.4 m [3,200 ft]), and a livestock well covering a total of 92.7 ha (229 ac) of agricultural land, and repair or replacement of 80 septic systems in the watershed were voluntarily implemented by landowners and homeowners. Water samples were collected from seven monitoring sites for 66 rain events from September 24, 2009, to August 9, 2011. Laboratory determinations of water samples included total suspended solids (TSS), total dissolved solids (TDS), total solids (TS), five-day biological oxygen demand (BOD5), nitrate/nitrite-nitrogen (NO3/NO2-N), soluble reactive phosphate (SRP), total phosphorus (TP), total Kjeldahl N (TKN), chloride (Cl), fluoride (Fl), sulfate (SO4), and fecal coliform counts. Surface water temperature, dissolved oxygen (DO), turbidity, conductivity, and pH were determined in the field using YSI Sonde (YSI Incorporated, Yellow Springs, Ohio). For the watershed, DO, BOD5, and TS concentrations and fecal coliform count ranged, respectively, between 1.2 and 14.1 mg L−1 (ppm), 2 and 40.1 mg L−1, 35 and 5,719 mg L−1, and 400 × 106 and 17 × 106 most probable number (MPN) per 100 mL. The months of March, April, June, and September showed, on average, higher concentrations of TS and TDS, fecal coliform count, NO3/NO2-N, and SRP and TP, respectively. As compared to the ongoing BMPs, the post-BMPs, TSS, NO3/NO2-N, SRP, and BOD5 concentrations, on average, were lower by 56.2%, 23.1%, 82.5%, and 27.4%, respectively. Developed land use types and the failed septic systems were identified as major sources of fecal coliform pollution. These results suggest comprehensive strategies are necessary for effective nonpoint source pollution control in agricultural watersheds.

Environmental conditions affect phenolic content and antioxidant capacity of leaves and fruit in wild partridgeberry (Vaccinium vitis-idaea)

Partridgeberry (Vaccinium vitis-idaea L.) is a good source of food and pharmaceutical ingredients, for which cultivation interest is increasing in North America. Nutrition-oriented breeding programs will benefit from an understanding of how the environment affects the biochemical traits of interest in wild populations. Total phenolic content (TPC) and antioxidant capacity (AC) as measured by the ability to capture free radicals were evaluated simultaneously in leaves and fruit of 56 wild populations across Newfoundland and Labrador, Canada. We tested variation in TPC and AC as a function of eight environmental factors, which showed different effects in leaves and fruit. Contrary to our expectations, TPC was not correlated with AC in either leaves or fruit, and mean TPC and AC were higher in fruit than in leaves. We propose a series of environment-based models for the selection of wild populations. Models for fruit involved ecoregion, temperature, and coastal proximity, and explained up to 51% of variation. While leaf models included surface water pH and sensitivity to acid rain, explaining up to 31%. We conclude that wild population selection in the province should target the North Shore Forest ecoregion and warm temperatures for fruit; and regions with low water alkalinity and pH &gt; 6.6 for leaves.

Surface water pH variations and trends in China from 2004 to 2014.

With economic development and the increase of energy consumption, surface water acidification has been a potential environmental concern in China. Here, we analyzed variations and trends in surface water pH of 73 sites from ten river basins in China from 2004 to 2014 with nonparametric Seasonal Kendall test method. Our analysis showed that the variations of surface water pH in China ranged from 6.5 to 9.0 in the past decade (2004-2014), which satisfied the water quality criteria in pH for protection of aquatic ecosystems in China (6.0-9.0) and USA (6.5-9.0). However, significant decreasing trends in surface water pH were found in 31 monitoring sites, which were mainly located in Haihe River, Taihu Lake and Yangtze River, while the pH value showed significant increasing trends in 22 sites, which mainly were located in Songhua River and Pearl River. Our results suggested the increased potential acidification of susceptible water bodies in China. Besides the control policy of sulfur dioxide (SO2) emissions, the emissions of nitrous oxides (NOx) should also be reduced to protect the aquatic systems in China.

Ocean acidification has lethal and sub-lethal effects on larval development of yellowfin tuna, Thunnus albacares

Ocean acidification (OA), the process by which increasing atmospheric CO2 is absorbed by the ocean, lowering the pH of surface waters, has been shown to affect many marine organisms negatively. It has been suggested that organisms from regions with naturally low pH waters, such as upwelling areas, could serve as models for future effects of OA and may be adapted to increased pCO2 levels. In this study, we examined the effects of OA on yellowfin tuna, a highly pelagic species that spawns in the eastern tropical Pacific, an area that includes regions of strong upwelling events. Larvae reared at decreasing pH levels (pH8.1, 7.6, 7.3 and 6.9) showed increasing organ damage in the kidney, liver, pancreas, eye and muscle, which correlated with decreased growth and survival. These findings complement earlier studies on organ damage in Atlantic cod and herring larvae and demonstrate that OA may have detrimental effects on fish larvae, regardless of their pre-exposure to low pH waters.

Diatom communities in the riparian systems associated with Lagos Lagoon, Nigeria I. Seasonal and anthropogenic patterns in Majidun Creek

In this report, we describe the investigation of water samples from Majidun Creek, a riparian system emptying into Lagos Lagoon, over a period of twelve months (February 2010– January 2011). Samples were obtained using a 55 μm plankton net towed at low speed for 10mins. Various physico-chemical parameters were monitored; surface water temperature, PO4-P, transparency, NO3-N, SO4 2- and silicate concentrations. All measured chemical parameters were lower in the rainy season while surface water pH ranged from acidic to alkaline (6.2–8.4), chlorophyll ‘a’ showed its highest value in the dry season. There was a remarkable change in seasonal salinity values while conductivity values ranged between 0.01 and 13.15 (mS/cm) in raining and dry seasons, respectively. Fifteen different orders of diatoms were recorded. The Naviculales dominated the diatom spectrum followed by Cymbellales, Fragillariales, Thalassiophysales, Nitzschiales and Eunotiales. Changes in diatom communities appear to be driven by two factors. The first, and dominant factor, is seasonality based on differences between the rainy and dry seasons which is correlating with peak biodiversity and peak biomass in diatom community structures. Anthropogenic impacts appear to be the second force influencing diatom community structure with areas of high population density, showing alterations in community composition when compared to regions with less human activity. Since most of the monographs used by Nigerian algologists are not indigenous, this paper may assist in solving a part of the diatom identification problems.

Groundwater, Acid and Carbon Dioxide Dynamics Along a Coastal Wetland, Lake and Estuary Continuum

Coastal wetlands are hotspots for biodiversity and biological productivity, yet the hydrology and carbon cycling within these systems remains poorly understood due to their complex nature. By using a novel spatiotemporal approach, this study quantified groundwater discharge and the related inputs of acidity and CO2 along a continuum of a modified coastal acid sulphate soil (CASS) wetland, a coastal lake and an estuary under highly contrasting hydrological conditions. To increase the resolution of spatiotemporal data and advance upon previous methodologies, we relied on automated observations from four simultaneous time-series stations to develop multiple radon mass balance models to estimate groundwater discharge and related groundwater inputs of acidity and dissolved inorganic carbon (DIC), along with surface water to atmosphere CO2 fluxes. Spatial surveys indicated distinct acid hotspots with minimum surface water pH of 2.91 (dry conditions) and 2.67 (flood conditions) near a non-remediated (drained) CASS area. Under flood conditions, groundwater discharge accounted for ∼14.5 % of surface water entering the lake. During the same period, acid discharge from the acid sulphate soil section of the continuum produced ∼4.8 kg H2SO4 ha−1 day−1, a rate much higher than previous studies in similar systems. During baseflow conditions, the low pH water was rapidly buffered within the estuarine lake, with the pH increasing from 4.22 to 6.07 over a distance of ∼250 m. The CO2 evasion rates within the CASS were extremely high, averaging 2163 ± 125 mmol m−2 day−1 in the dry period and 4061 ± 259 mmol m−2 day−1 under flood conditions. Groundwater input of DIC could only account for 0.4 % of this evasion in the dry conditions and ∼5 % during the flood conditions. We demonstrated that by utilising a spatiotemporal (multiple time-series stations) approach, the study was able to isolate distinct zones of differing hydrology and biogeochemistry, whilst providing more reasonable groundwater acid input estimates and air–water CO2 flux estimates than some traditional sampling designs. This study highlights the notion that modified CASS wetlands can release large amounts of CO2 to the atmosphere because of high groundwater acid inputs and extremely low surface water pH.

Porewater CO2–carbonic acid system chemistry in permeable carbonate reef sands

Porewater was collected from highly permeable, carbonate-rich, sandy sediments at two locations on Oahu, Hawai'i, CRIMP-2 on the Kaneohe Bay barrier reef and Ala Wai on a fringing coral reef nearshore to the Ala Wai canal and urban Honolulu. Samples were collected at the sediment–water interface and from porewater wells installed at sediment depths of 2, 4, 6, 8, 12, 16, 20, 30, 40, and 60cm. Total alkalinity and dissolved inorganic carbon were enriched, relative to the overlying water column, and ratios of TA:DIC at the two sites (0.80 and 0.93) suggest that aerobic respiration and sulfate reduction – both coupled with carbonate mineral dissolution – in the oxic and anoxic layers, respectively, are the major controls on the biogeochemistry of the sediment–porewater system. The porewater was approaching thermodynamic saturation with respect to aragonite with increasing depth (Ω=1.2–3.5) and was found to be undersaturated with respect to all phases of magnesian calcite (Ω=0.3–0.9) containing greater than 12mol% MgCO3. In addition to microbial controls on porewater diagenesis, transient physical events in the water column, such as swells and changing bottom current speeds, appear to exert a strong influence on the porewater chemistry due to the highly permeable and porous nature of the sediments. Profiles collected before and after swell events at each location show an apparent flushing of the porewater system, replacing low pH, high DIC interstitial waters with seawater from the overlying water column. Based partially on the results of our porewater analysis, we hypothesize that future changes in surface water DIC and pH resulting from ocean acidification (OA) could have a very significant impact on the dissolution rates of metastable skeletal and abiotic carbonate phases of varying magnesian calcite compositions (Mg-calcite) and aragonite. This is especially important in sandy reef sediments like those of this study, which are greatly influenced by the overlying water column. As the carbonate mineral saturation state of the overlying water column continues to decrease due to OA, an increase in carbonate mineral dissolution is expected and the high advective rate of water exchange between the porewater of sandy sediments and the overlying water column, as observed in this study and others, along with increased rates of dissolution of metastable carbonate phases, could lead to significantly higher future rates of mass transfer of TA and DIC between the sediments and the overlying water column. This may result in a deficit of the CaCO3 balance in some reef ecosystems and a decrease in accretion rates. Analysis of our porewater work in conjuction with previous studies of the porewater chemistry of Kaneohe Bay, Oahu in both siliciclastic-rich and siliciclastic-poor carbonate sediments leads to the conclusion that the porewaters of the former are more strongly buffered with respect to pH than those of the latter due to reverse weathering reactions. Thus carbonate-rich sandy sediments of reefs with little terrestrial influence and aluminosilicate detritus may become more susceptible to calcium carbonate loss due to the enhanced environmental and microbial dissolution of carbonate substrates expected due to OA.

Peat Bogs as Hotspots for Organoarsenical Formation and Persistence.

Peatlands have received significant atmospheric inputs of As and S since the onset of the Industrial Revolution, but the effect of S deposition on the fate of As is largely unknown. It may encompass the formation of As sulfides and organosulfur-bound As, or the indirect stimulation of As biotransformation processes, which are presently not considered as important As immobilization pathways in wetlands. To investigate the immobilization mechanisms of anthropogenically derived As in peatlands subjected to long-term atmospheric pollution, we explored the solid-phase speciation of As, Fe, and S in English peat bogs by X-ray absorption spectroscopy. Additionally, we analyzed the speciation of As in pore- and streamwaters. Linear combination fits of extended X-ray absorption fine structure (EXAFS) data imply that 62-100% (average: 82%) of solid-phase As (Astot: 9-92 mg/kg) was present as organic As(V) and As(III). In agreement with appreciable concentrations of organoarsenicals in surface waters (pH: 4.0-4.4, Eh: 165-190 mV, average Astot: 1.5-129 μg/L), our findings reveal extensive biotransformation of atmospheric As and the enrichment of organoarsenicals in the peat, suggesting that the importance of organometal(loid)s in wetlands subjected to prolonged air pollution is higher than previously assumed.

Removal of dissolved organic matter from algae-polluted surface water by coagulation

Dissolved organic matter (DOM) is ubiquitous in the algae-polluted surface water and it possesses a potential threat to drinking water safety. It is important to investigate the removal efficiency of DOM by coagulation. Polyaluminum chloride a widely used coagulant is applied in the treatment of DOM derived from Minzhu Lake in Chongqing of China. Based on the analysis of dissolved organic carbon, UV254, specific ultraviolet absorbance, and fluorescence excitation-emission matrix spectroscopy, the results indicate that the small proportion of DOM, such as aromatic-like organic substances, is removed with algae and other colloid particles via coagulation, but most of DOM, such as he tryptophan-like and fulvic-like organic substances, is remained in the treated water. Co-flocculation, bridging, adsorption, and entrapment would be the main removal mechanisms of DOM. DOM removal will be slightly improved through optimizing pH of surface water and using a composite coagulant.

Speciation, Size Fractionation and Transport of Trace Elements in the Continuum Soil Water–Mire–Humic Lake–River–Large Oligotrophic Lake of a Subarctic Watershed

The concentration and size fractionation of major and trace elements (TEs) linked to organo-mineral colloids along the landscape gradient soil water–peat mire–humic lakes–river–large oligotrophic lake have been investigated within two watersheds located in the subarctic region (Karelia, Russia) in the summer base-flow period. A large volume of natural waters was filtered in the field using cascade filtration and ultrafiltration (UF) with a progressively decreasing pore size [100, 20, 10, 5, 0.8, 0.4, 0.22, 0.1, 0.046, 0.0066 (100 kDa), 0.0031 (10 kDa) and 0.0014 µm (1 kDa)] followed by multi-elemental ICP-MS and dissolved organic carbon (DOC) analysis. In situ dialysis with 10 and 1 kDa molecular weight cutoff membranes was also conducted. According to the TE distribution among different size fractions in the continuum soil (mire)–humic lake–river–large lake, the following groups of elements could be distinguished: (1) elements significantly bound to the colloidal (1 kDa—0.22 µm) fraction and decreasing the proportion of this fraction from the feeding lake and stream to the terminal oligotrophic lake (Fe, Ti and U); (2) colloidally dominated (>80 %) elements exhibiting similar size fractionation in all studied settings (Y, REEs, Zr, Hf and Th); (3) elements appreciably bound to colloids (20–40 %) in organic-rich soil and bog waters and decreasing their colloidal fraction to approximately 10 % in the oligotrophic lake (Mg, Ca, Sr, Rb and Mo); and (4) elements linked to the colloidal fraction (40–80 %) and not demonstrating any systematic variation between different landscape units (Ni, Co, Cu, Cd, Cr, Mn, Zn and Pb). The in situ dialysis technique produced a similar picture of the colloidal size fractionation with generally lower proportions of elements in the colloidal fraction compared to the UF. Thermodynamic modeling of trace element speciation using available codes demonstrated that complexation with dissolved organic matter and adsorption at the surface of ferric colloids can adequately model the observed colloidal speciation of divalent metals. However, the modeling could not describe the distribution of trivalent and tetravalent hydrolysates (TE3+,4+) among different size fractions and cannot reproduce the experimentally observed proportion of their colloidal forms. Therefore, coprecipitation with organo-ferric colloids should be considered to account for the partitioning of TE3+,4+ between truly dissolved (<1 kDa) and various colloidal fractions. It follows from the results of this study that autochthonous processes of organic matter fractionation, such as (1) transformation of initially allochthonous soil-derived colloids via photo- and biodegradation or (2) new organic ligand production by plankton and periphyton, cannot appreciably affect the distribution of TEs among various size fractions of colloids and particles along the landscape gradient from soil water to terminal lake. Thus, even crucial changes in the environmental conditions, such as the river discharge regime and relative lake versus bog coverage, surface water pH, pCO2 and DOC changes that are likely to occur according to the “extreme” scenario of the climate warming in the Arctic, should not affect the size fractionation and, therefore, the potential aquatic lability and biodisponibility of TEs present as organic (divalent transition metals, alkaline earth metals) and organo-mineral (Fe, Al, insoluble trivalent and tetravalent elements and U) colloids.

Microelement composition of bottom sediments in Mekong River delta, Republic of Vietnam

Mean concentrations of Zn, Cu, Pb, Cd, As, and Hg in water and bottom sediments of Mekong Delta (Socialist Republic of Vietnam) over low-water period of 2013 were evaluated. The space distribution of the chemical composition of bottom sediments shows a tendency toward an increase in the concentrations of the examined microelements toward the sea coastline. The mechanism of those changes was considered and attributed to a release of low-solubility compounds from water and with sorption of microelements on alluvium and sediment particles at the mixing of river and sea water. The value of surface water pH was suggested as an indicator of current and forecasted variations of the concentrations of some microelements in bottom sediments.

Connection between Ocean Acidification and Sound Propagation

Ocean Ambient Noise (OAN) results from both anthropogenic and natural sources. Varied noise sources are&#x0D; dominant in low (LFB: 10 to 500 Hz), medium (MFB: 500 Hz to 25 kHz) and high (HFB:&amp;gt;25 kHz) frequency&#x0D; bands. Mostly, LFB is dominated by anthropogenic sources. MFB that cannot spread over long ranges of sound&#x0D; sources contribute to the OAN. Ocean is an exceptionally noisy place.&#x0D; Ocean acidification (OAc) from rising Carbon dioxide (CO2&#x0D; ) levels will result in decreased sound absorption&#x0D; and therefore, amplified levels of OAN. Carbon dioxide spewed into the atmosphere by burned fossil-fuel&#x0D; which dissolves in the seawater causes more acidic condition in oceans which has strong connection between&#x0D; chemical oceanography and sound propagation. As the ocean becomes more acidic, sound absorption at LFB&#x0D; decreases and acidic oceans would result in significant decreases in ocean sound absorption.&#x0D; In the recent years, the acoustic environment of oceans has reacted to transformations in both natural and&#x0D; anthropogenic impacts. Greenhouse gases concentrations, especially CO2&#x0D; , rises in atmosphere due to industrial&#x0D; revolution. CO2 dissolved in the seawaters deposited in two major forms (carbonate and bicarbonate), which&#x0D; both lead to decrease pH of surface waters. Over the last 400 million years, pH of oceans has been stable&#x0D; around 8.2 globally. Latest investigations suggest that global pH is around 8.1 globally and various general&#x0D; oceanic circulation models (GOCM) calculate that, emissions could reduce ocean pH by a degree between 0.4&#x0D; units (according to moderate approach) and 0.7 units (according to an aggressive one) by the end of this&#x0D; century.&#x0D; This article discusses the CO2 considerations both in the atmosphere and hydrosphere which are directly related&#x0D; with seawater pH and oceans noise levels.

Solar light (hv) and H2O2/hv photo-disinfection of natural alkaline water (pH 8.6) in a compound parabolic collector at different day periods in Sahelian region.

The photo-disinfection of natural alkaline surface water (pH 8.6 ± 0.3) for drinking purposes was carried out under solar radiation treatments. The enteric bacteria studied were the wild total coliforms/Escherichia coli (10(4) CFU/ml) and Salmonella spp. (10(4) CFU/ml) naturally present in the water. The photo-disinfection of a 25-l water sample was carried out in a solar compound parabolic collector (CPC) in the absence and in the presence of hydrogen peroxide (H2O2). The addition of H2O2 (10 mg/L) to the sample water was sufficient to enhance the photo-disinfection and ensure an irreversible lethal action on the wild enteric bacteria contents of the sample. The inactivation kinetic of the system was significantly enhanced compared to the one carried out without H2O2 addition. The effect of the solar radiation parameters on the efficiency of the photo-disinfection were assessed. The pH has increased during the treatment in all the photo-disinfection processes (hv and H2O2/hv). The Salmonella spp strain has shown the best effective inactivate time in alkaline water than the one recorded under acidic or near-neutral conditions. The evolution of some physico-chemical parameters of the water (turbidity, NO2(-), NO3(-), NH4(+), HPO4(2-), and bicarbonate (HCO3(-))) was monitored during the treatment. Finally, the possible mechanistic process involved during the enteric bacteria inactivation was suggested.

Slow-flow habitats as refugia for coastal calcifiers from ocean acidification.

The pH of the oceans' surface water is dropping, termed ocean acidification (OA), and the 0.4 unit reduction in pH by 2100 is projected to negatively impact benthic coastal organisms that produce calcium carbonate "skeletons." Research has focussed on identifying species that are susceptible to OA, but there is an urgent need to discover refuge habitats that will afford protection to vulnerable species. The susceptibility of calcium carbonate skeletons to dissolution by OA depends on the pH at their surface, and this is controlled by the interaction between seawater velocity and organismal metabolism. This perspective considers how seawater velocity modifies the responses of calcifying organisms (seaweed, shellfish, and tropical corals) to OA through its action on controlling diffusion boundary layer thickness and thereby the pH and calcium carbonate saturation state (Ω) at the organisms' surface. Evidence is presented to support the idea that slow-flow habitats, such as wave-sheltered bays or the within canopies of seaweed/seagrass beds, might provide inexpensive refugia from OA for vulnerable coastal calcifiers.

Seasonal lake surface water temperature trends reflected by heterocyst glycolipid-based molecular thermometers

Abstract. It has been demonstrated that the relative distribution of heterocyst glycolipids (HGs) in cultures of N2-fixing heterocystous cyanobacteria is largely controlled by growth temperature, suggesting a potential use of these components in paleoenvironmental studies. Here, we investigated the effect of environmental parameters (e.g., surface water temperatures, oxygen concentrations and pH) on the distribution of HGs in a natural system using water column filtrates collected from Lake Schreventeich (Kiel, Germany) from late July to the end of October 2013. HPLC-ESI/MS (high-performance liquid chromatography coupled to electrospray ionization–mass spectrometry) analysis revealed a dominance of 1-(O-hexose)-3,25-hexacosanediols (HG26 diols) and 1-(O-hexose)-3-keto-25-hexacosanol (HG26 keto-ol) in the solvent-extracted water column filtrates, which were accompanied by minor abundances of 1-(O-hexose)-3,27-octacosanediol (HG28 diol) and 1-(O-hexose)-3-keto-27-octacosanol (HG28 keto-ol) as well as 1-(O-hexose)-3,25,27-octacosanetriol (HG28 triol) and 1-(O-hexose)-3-keto-25,27-octacosanediol (HG28 keto-diol). Fractional abundances of alcoholic and ketonic HGs generally showed strong linear correlations with surface water temperatures and no or only weak linear correlations with both oxygen concentrations and pH. Changes in the distribution of the most abundant diol and keto-ol (e.g., HG26 diol and HG26 keto-ol) were quantitatively expressed as the HDI26 (heterocyst diol index of 26 carbon atoms) with values of this index ranging from 0.89 in mid-August to 0.66 in mid-October. An average HDI26 value of 0.79, which translates into a calculated surface water temperature of 15.8 ± 0.3 °C, was obtained from surface sediments collected from Lake Schreventeich. This temperature – and temperatures obtained from other HG indices (e.g., HDI28 and HTI28) – is similar to the one measured during maximum cyanobacterial productivity in early to mid-September and suggests that HGs preserved in the sediment record of Lake Schreventeich reflect summer surface water temperatures. As N2-fixing heterocystous cyanobacteria are widespread in present-day freshwater and brackish environments, we conclude that the distribution of HGs in sediments may allow for the reconstruction of surface water temperatures of modern and potentially ancient lacustrine settings.

Effects of oceanic circulation and volcanic ash-fall on calcite dissolution in bathyal sediments from the SW Pacific Ocean over the last 550ka

Abstract The effects on calcite dissolution of both oceanic circulation and volcanic ash-fall were evaluated in lower bathyal sediments over the last 550 ka record from core MD 97-2114, recovered on the northern slope (depth of 1936 m, in the Pacific Deep Water, PDW) of the Chatham Rise (east of New Zealand, SW Pacific Ocean). This area has been impacted by changes in glacial/interglacial circulation and ocean chemistry as well as by the explosive volcanic activity of the Taupo Volcanic Zone. Several micro-paleontological dissolution proxies, based on planktonic foraminifera and calcareous nannofossils, were analysed in order to evaluate the calcite dissolution of the deep-sea sediments. These were compared with a couple of proxies of primary productivity (benthic foraminiferal epifaunal/infaunal ratio and δ13Cbenthic foraminifera) and the abundance of volcanic glass. The dissolution proxy data from MD 97-2114 were compared with two nearby ODP sites, ODP 1123 (3290 m deep, bathed by the lower Circumpolar Deep Water, LCDW) and ODP 1125 (1365 m deep, bathed by the Antarctic Intermediate Water, AAIW). The results suggest: (1) the calcite dissolution/preservation cycles at all three core sites show Glacial–Interglacial (G–I) periodicities that match the previously described “Pacific-style” CaCO3 cycles; (2) several short-term dissolution events do not follow this general scheme and occur following tephra deposition. The dissolution related to the tephra deposition seems to have mostly affected calcareous nannofossils, thus we hypothesise that the ash-fall induced a temporary reduction of the surface water pH (below 7.8), which affected the coccolithophores that inhabit the surface waters. (3) Other short-term dissolution events (1000 years) are unrelated to tephra deposition and are possibly driven by the slowing of deep-sea circulation and a reduced Deep Western Boundary Current (DWBC). This lead to the dominance of older, more corrosive Pacific Deep Water (PDW) flowing in to the region, resulting in coeval dissolution episodes at all three core sites (depth range from 1365 to 3290 m).

Ecological dynamics in the riverine aquifers of a gaining and losing river

The effects of river-flow fluctuations on groundwater ecosystems and differences in ecological conditions in aquifers connected to losing, gaining, and alternating river reaches are poorly known. We used monitoring wells at gaining and losing reaches along an alluvial river to identify associations between river and groundwater fluctuations and ecological conditions in riverine aquifers. Groundwater and surface-water pH, temperature, and dissolved O2 (DO) were positively correlated at all sites, and groundwater and surface-water dissolved organic C (DOC) concentrations were positively correlated at 3 sites. Groundwater and surface water in the gaining section were more NO3–-enriched and highly mineralized than in the losing section. These differences reflect the primary water source in each section. The gaining section is dominated by regional groundwater and the losing section by hillslope runoff. The groundwater–surface-water correlations and comparisons between sections indicate that physicochemical conditions in losing-reach aquifers are controlled by surface-water infiltration, and conditions in gaining-reach aquifers are controlled by groundwater inflow from up-gradient aquifers. At some sites, groundwater DOC concentrations were positively correlated with DO concentrations and heterotrophic bacterial densities. These correlations suggest that DOC and DO are depleted simultaneously by aerobic microbial processes and that bacterial populations are DOC-limited, which may in turn limit invertebrate abundance. DOC concentrations, bacterial densities, and invertebrate density and taxon richness varied in response to river flow, groundwater levels, and time since floods at some sites. Patterns of river–aquifer exchange and hydrology–groundwater-ecology relationships are prerequisites for identifying the river-flow requirements for healthy groundwater ecosystems.

Seawater inundation of coastal floodplain sediments: Short-term changes in surface water and sediment geochemistry

Coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea-level rise due to their low elevation and proximity to the coastline. Intact soil cores from a levee, acid-sulfate soil scald and four backswamp sites on a coastal floodplain in eastern Australia were inundated with artificial seawater treatments (0%, 50% and 100%) for 14days to examine the short term consequences for surface water and floodplain sediment geochemistry. All sites displayed an initial decrease in surface water pH following inundation with 50% and 100% seawater. In addition, higher concentrations of trace metals (Al, Fe, Mn, Ni and Zn) were observed in most sites inundated with 50% or 100% seawater. This was generally attributed to competitive exchange and desorption of trace metals from sediments due to the higher ionic strength of the seawater solutions and upward diffusive flux of metals from the sediments to surface waters. At one backswamp site, reductive processes had established by day 7, which also resulted in elevated Fe2+ concentrations in the overlying surface waters. Transmission electron microscopy (TEM) identified the presence of poorly crystalline ferrihydrite and schwertmannite, and goethite and jarosite. These meta-stable Fe(III) minerals can act as a source of metals for desorption and can also be readily reduced and act as a source of Fe2+ to surface waters. Importantly, inundation with either 50% or 100% seawater resulted in a similar magnitude of acidity and trace metal mobilisation. The data suggest that an inundation event of ~0.2m depth with either 50% or 100% seawater could cause a pulse mobilisation of up to 64.8 and 9.1kgha−1 of Fe and Al, respectively — quantities of similar magnitude to previous estimates of annual drainage fluxes from similar backswamps. This study suggests that the short term inundation of coastal floodplain sediments by either brackish water or seawater will result in rapid declines in surface water quality as a result of increased liberation of acidity and trace metals.

EVALUATION OF LANDFILL LEACHATE POLLUTION: FINDINGS FROM A MONITORING STUDY AT MUNICIPAL WASTE LANDFILL

The monitoring that was carried out at the landfill specialized in leachate, groundwater and surface water. There were 6 sampling sites. The observed parameters were pH, BOD5, CODCr, conductivity. Leachate reached the high values in all observed parameters. Groundwater samples were collected at two monitoring wells and the sampling site (A, B, C). Surface water was collected from two sampling sites (D, E). The pH showed slightly acid values at all sampling points. The pH of surface water was slightly acid to neutral. Both BOD5 and CODCr values remained stable over the reporting period. The average conductivity value at sampling points D, E remained constant. In line with the Czech National Standard CSN 75 7221 “Classification of Surface Water Quality” sampling point D belongs to II Water Quality Class – slightly polluted water and sampling site E to Class I water quality – unpolluted water. The authors believe that the fluctuations occurring with regard to the values of certain samples were not caused by the operation of the landfill itself, but were a result of the intense agricultural activity nearby the landfill.