Southern Cross GeoScience

Root metabolic response of rice (Oryza sativa L.) genotypes with contrasting tolerance to zinc deficiency and bicarbonate excess

Michael T. Rose et al. — Thu, 23 May 2013 21:48:42 PDT

Plants are routinely subjected to multiple environmental stresses that constrain growth. Zinc (Zn) deficiency and high bicarbonate are two examples that co-occur in many soils used for rice production. Here, the utility of metabolomics in diagnosing the effect of each stress alone and in combination on rice root function is demonstrated, with potential stress tolerance indicators identified through the use of contrasting genotypes. Responses to the dual stress of combined Zn deficiency and bicarbonate excess included greater root solute leakage, reduced dry matter production, lower monosaccharide accumulation and increased concentrations of hydrogen peroxide, phenolics, peroxidase and N-rich metabolites in roots. Both hydrogen peroxide concentration and root solute leakage were correlated with higher levels of citrate, allantoin and stigmasterol. Zn stress resulted in lower levels of the tricarboxylic acid (TCA) cycle intermediate succinate and the aromatic amino acid tyrosine. Bicarbonate stress reduced shoot iron (Fe) concentrations, which was reflected by lower Fe-dependent ascorbate peroxidase activity. Bicarbonate stress also favoured the accumulation of the TCA cycle intermediates malate, fumarate and succinate, along with the non-polar amino acid tyrosine. Genotypic differentiation revealed constitutively higher levels of d-gluconate, 2-oxoglutarate and two unidentified compounds in the Zn-efficient line RIL46 than the Zn-inefficient cultivar IR74, suggesting a possible role for these metabolites in overcoming oxidative stress or improving metal re-distribution.

Trace element reactivity in FeS-rich estuarine sediments: influence of formation environment and acid sulfate soil drainage

Bree Morgan et al. — Thu, 23 May 2013 20:47:55 PDT

Iron monosulfides (FeS) precipitate during benthic mineralisation of organic C and are well known to have a strong influence on trace element bioavailability in sediments. In this study we investigate the reactivity of trace elements (As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Zn) in sediments containing abundant and persistent FeS stores, collected from a south-western Australian estuarine system. Our objective was to explore the influence of sediment formation conditions on trace element reactivity by investigating sediments collected from different environments, including estuarine, riverine and acid sulfate soil influenced sites, within a single estuarine system. In general, we found a higher degree of reactivity (defined by 1 mol/L HCl extractions) for Cd, Mn, Pb and Zn, compared with a lower reactivity of As, Co, Cr, Cu, Mo and Ni. Moderate to strong correlations (R² > 0.4, P < 0.05) were observed between AVS and reactive Cd, Co, Mn, Mo, Ni, Pb and Zn within many of the formation environments. In contrast, correlations between AVS and As, Cr and Cu were generally poor (not significant, R² < 0.4, P > 0.05). Based on their reactivity and correlations with AVS, it appears that interactions (sorption, co-precipitation) between FeS and Cd, Mn, Pb and Zn in many of the sediments from this study are probable. Our data also demonstrate that drainage from acid sulfate soils (ASS) can be a source of trace elements at specific sites. A principal components analysis of our reactive (1 mol/L HCl extractable) trace element data clearly distinguished sites receiving ASS drainage from the other non-impacted sites, by a high contribution from Fe–Co–Mn–Ni along the first principal axis, and contributions from higher S–As/lower reactive Pb along the second axis. This demonstrates that trace element reactivity in sediments may provide a geochemical signature for sites receiving ASS drainage.

Barium distributions in teeth reveal early-life dietary transitions in primates

Christine Austin et al. — Thu, 23 May 2013 19:32:01 PDT

Early-life dietary transitions reflect fundamental aspects of primate evolution and are important determinants of health in contemporary human populations. Weaning is critical to developmental and reproductive rates; early weaning can have detrimental health effects but enables shorter inter-birth intervals, which influences population growth. Uncovering early-life dietary history in fossils is hampered by the absence of prospectively validated biomarkers that are not modified during fossilization. Here we show that large dietary shifts in early life manifest as compositional variations in dental tissues. Teeth from human children and captive macaques, with prospectively recorded diet histories, demonstrate that barium (Ba) distributions accurately reflect dietary transitions from the introduction of mother’s milk through the weaning process. We also document dietary transitions in a Middle Palaeolithic juvenile Neanderthal, which shows a pattern of exclusive breastfeeding for seven months, followed by seven months of supplementation. After this point, Ba levels in enamel returned to baseline prenatal levels, indicating an abrupt cessation of breastfeeding at 1.2 years of age. Integration of Ba spatial distributions and histological mapping of tooth formation enables novel studies of the evolution of human life history, dietary ontogeny in wild primates, and human health investigations through accurate reconstructions of breastfeeding history.

Water quality changes in Lake McKenzie, Fraser Island, Australia: a Palaeolimnological approach

Sarah C. Hembrow et al. — Mon, 20 May 2013 23:49:12 PDT

Surface water resources are highly valued for their ecological services and functions. However, their quality is under threat from anthropogenic activities and climate change. A detailed understanding of natural aquatic conditions and variability is rare. This is particularly the case in Australia where the variable climate produces significant ecological changes within natural thresholds and few long-term environmental data sets exist. Palaeoecology represents a means to identify natural fluctuations of aquatic ecosystems and provide long-term data for effective environmental management. This study uses a palaeoecological approach to identify biological and sediment changes in Lake McKenzie, Fraser Island, Australia. A sediment core was extracted from the lake and the fossil diatom assemblage and sediment particle size analysed. Inferred environmental changes were detected throughout the core that pre-date European impacts. The likely causes of these changes are climatic oscillations. Further dating is required to establish a detailed chronological record and identify the timing of detected environmental change at Lake McKenzie.

Environmental system analysis for river pollution control

Jasmine Diwakar et al. — Mon, 20 May 2013 23:33:37 PDT

This paper presents a new tool, developed with the aim of assessing the environmental impact from industrial effluents and sewage systems in Hanumante River and to recommend the finest procedures to control water pollution so as to improve the water quality of Hanumante River using environmental system analysis. Hanumante River is heavily polluted due to inefficient management resulting in water-associated problems. The time horizon for this study is from 2000 to 2030, yearly, and the spatial boundary is considered to be Hanumante River, Bhaktapur, Nepal. The stakeholder, function, and scenario analyses are employed as three tools for study. The participation of main stakeholders aids in resolving their various conflicting interests in Hanumante River, thus creating a common understanding about the crisis under study. A complete functional analysis illustrates various functions fulfilled by the river and their associated services. Based on the interests of the stakeholders and their priorities, two alternatives resulting in four scenarios are identified and ranked against four selected criteria. A combination of improved industrial technology and efficient municipal waste management gives the best solution to the pollution problem in Hanumante River. Different alternative themes have corresponding effects on the selected criteria. The choice is in the hands of the decision makers of Bhaktapur City. The outcome of this paper will ultimately help decision and policy makers to analyze the environmental impact of river systems and find efficient and better-quality decision making for water resource management incorporating the knowledge and experiences of various stakeholders.

Sulfate radical-induced degradation of 2,4,6-trichlorophenol: a de novo formation of chlorinated compounds

Lei Xu et al. — Wed, 15 May 2013 22:54:58 PDT

The degradation of 2,4,6-trichlorophenol (TCP) by sulfate radical generated via Co(II)-mediated activation of peroxymonosulfate (PMS) was examined. The influencing factors, such as substrate concentration and pH were investigated. The initial pH and its adjustment orders significantly affected the TCP degradation and mineralization. Several chlorinated products were detected, as well as some carboxylic acids, such as glycolic acid and oxalic acid. Many polychlorinated (chlorine atom number ⩾3) aromatics (e.g. 2,4,5-trichlorophenol, 2,3,4,6-tetrachlorophenol, 2,3,5,6-tetrachloro-1,4-benzenediol) and even their ring-opening products (e.g. 2,4-dichloro-5-oxo-2-hexenedioic acid, 1,1,3,3-tetrachloro-2-propanone) were identified, indicating a de novo formation mechanism of organohalogens may be involved in TCP degradation. The released chlorine atoms from TCP and/or dichloride radicals activated by sulfate radicals played an important role. This finding may have significant scientific and technical implications for utilizing Co/PMS reagent to detoxify chlorinated pollutants.

Mechanism and kinetics of dark iron redox transformations in previously photolyzed acidic natural organic matter solutions

Shikha Garg et al. — Wed, 15 May 2013 17:02:38 PDT

Stable organic species produced on irradiation of Suwannee River Fulvic Acid (SRFA) are shown to be important oxidants of Fe(II) in aqueous solutions at acidic pH, with rate constants substantially larger than those for oxygenation of Fe(II) under the same conditions. These Fe(II)-oxidizing species, which are formed during photolysis by superoxide-mediated oxidation of reduced organic moieties that are present intrinsically in SRFA, are long-lived in the dark but prone to rapid oxidation by singlet oxygen (¹O₂) under irradiated conditions. The intrinsic reduced organic species are able to reduce Fe(III) at acidic pH. Although the exact identities of the organic Fe(II) oxidant and the organic Fe(III) reductant are unclear, their behavior is consistent with that expected of semiquinone and hydroquinone-like moieties respectively. A kinetic model is developed that adequately describes all aspects of the experimental data obtained, and which is capable of predicting dark Fe(II) oxidation rates and Fe(III) reduction rates in the presence of previously photolyzed natural organic matter.

Quantifying retained acidity in acid sulfate soil materials: an evaluation of routine methods

Chamindra Vithana et al. — Tue, 07 May 2013 19:31:31 PDT

Retained Acidity is an important aspect of acid sulfate soil (ASS) but techniques for the quantification of this property have not yet been systematically assessed. In this study, the utility of routine techniques for quantifying the Retained Acidity fraction will be examined. The relatively insoluble minerals such as jarosite and schwertmannite are major contributors to Retained Acidity in ASS. Known quantities of synthetic and natural jarosites and schwertmannite will be added to two non-acid sulfate soil samples plus to one quartz sand sample. By using SNAS in the chromium suite and SRAS in the SPOCAS suite (Ahern et al. 2004), the Retained Acidity fraction of the spiked samples will be assessed. The method introduced by Li et al. (2007) and the acidified ammonium oxalate method (Regenspurg et al. 2004) will be undertaken to recover the added jarosite and schwertmannite, respectively. The mineralogy of the samples will be characterized by X-ray diffraction (XRD). In the second part of this study, the potential interference from

Effects of catchment and riparian landscape setting on water chemistry and seasonal evolution of water quality in the upper Han river basin, China

Siyue Li et al. — Sun, 05 May 2013 22:30:51 PDT

Six-year (2005–2010) evolution of water chemistry (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Ca²⁺and Mg²⁺) and their interactions with morphological properties (i.e., slope and area), land cover, and hydrological seasonality were examined to identify controlling factors and processes governing patterns of stream water quality in the upper Han River, China. Correlation analysis and stepwise multiple regression models revealed significant correlations between ions (i.e., Cl⁻, SO₄²⁻, Na⁺ and K⁺) and land cover (i.e., vegetation and bare land) over the entire catchment in both high- and low-flow periods, and in the buffer zone the correlation was much more stronger in the low-flow period. Catchment with steeper slope (>15°) was negatively correlated with major ions, largely due to multicollinearity of basin characteristics. Land cover within the buffer zone explained slightly less of major elements than at catchment scale in the rainy season, whereas in the dry season, land cover along the river networks in particular this within 100 m riparian zone much better explained major elements rather than this over the entire catchment. Anthropogenic land uses (i.e., urban and agriculture) however could not explain water chemical variables, albeit EC, TDS, anthropogenic markers (Cl⁻, NO₃⁻, SO₄²), Na⁺, K⁺ and Ca²⁺ significantly increased during 2005–2010, which was corroborated by principal component analyses (PCA) that indicated anthropogenic inputs. Observations demonstrated much higher solute concentrations in the industrial-polluted river. Our results suggested that seasonal evolution of water quality in combined with spatial analysis at multiple scales should be a vital part of identifying the controls on spatio-temporal patterns of water quality.

AMS dating of ancient plant residues from experimental stone tools: a pilot study

Andrea Yates et al. — Sun, 05 May 2013 21:59:08 PDT

Residue analyses on stone artefacts have contributed to resolving functional questions in stone tool research. Although identifying the function of tools through the analysis of their micro-residues is possible, the establishment of a sound numerical chronology for stone tools lacking a clear stratigraphic sequence, such as surface scatters, remains a challenge. While radiocarbon dating of blood residue on stone artefacts has been published previously (Loy 1987, 1990, 1993; Loy et al., 1990; Nelson et al.1986), this paper reports on an experiment designed to assess the possibility of directly dating residues on stone artefacts by accelerator mass spectrometry (AMS) based radiocarbon measurements. Innovative with this approach is (1) the use of mid and late Holocene pre-dated plant material (wood and peat), processed with contemporarily manufactured stone flakes under controlled laboratory conditions and (2) the use of very small carbon masses (less than 22 μg) for radiocarbon dating. The ¹⁴C results of the wood residues are in excellent agreement with the original sample, whereas the ¹⁴C results of the peat residues yield a wider age variation as expected due to the inhomogeneity of the material, but nevertheless, provided dates within an expected age range. Preliminary results demonstrate the feasibility of dating very small amounts of plant residue on lithics directly when contaminants are confined.

Sequential reduction–oxidation for photocatalytic degradation of tetrabromobisphenol A: kinetics and intermediates

Yaoguang Guo et al. — Thu, 02 May 2013 23:28:38 PDT

C Br bond cleavage is considered as a key step to reduce their toxicities and increase degradation rates for most brominated organic pollutants. Here a sequential reduction/oxidation strategy (i.e. debromination followed by photocatalytic oxidation) for photocatalytic degradation of tetrabromobisphenol A (TBBPA), one of the most frequently used brominated flame retardants, was proposed on the basis of kinetic analysis and intermediates identification. The results demonstrated that the rates of debromination and even photodegradation of TBBPA strongly depended on the atmospheres, initial TBBPA concentrations, pH of the reaction solution, hydrogen donors, and electron acceptors. These kinetic data and byproducts identification obtained by GC–MS measurement indicated that reductive debromination reaction by photo-induced electrons dominated under N2-saturated condition, while oxidation reaction by photoexcited holes or hydroxyl radicals played a leading role when air was saturated. It also suggested that the reaction might be further optimized for pretreatment of TBBPA-contaminated wastewater by a twostage reductive debromination/subsequent oxidative decomposition process in the UV-TiO2 system by changing the reaction atmospheres.

A critical evaluation of Retained Acidity (AR) estimating methods in Acid Base Account (ABA) approach for Acid Sulfate Soils (ASS)

Chamindra Vithana et al. — Thu, 02 May 2013 22:43:47 PDT

Understanding the behaviour of schwertmannite and jarosite in acid sulfate soils

Chamindra Vithana et al. — Thu, 02 May 2013 22:38:35 PDT

Readily available acidity in schwertmannite

Chamindra Vithana et al. — Thu, 02 May 2013 22:11:19 PDT

Schwertmannite and jarosite are considered as less soluble ironhydroxy sulfate minerals which are present in highly acidic environments (pH < 3). These minerals release acidity in the long run as they weather by hydrolysis [1]. However, 1M KCl extraction of soil samples (Clarence and Quartz) spiked with those two minerals showed that schwertmannite has some acidity that may be readily available.

Assessing heavy metal pollution in the water level fluctuation zone of China’s Three Gorges Reservoir using geochemical and soil microbial approaches

Chen Ye et al. — Thu, 02 May 2013 21:51:39 PDT

The water level fluctuation zone (WLFZ) in the Three Gorges Reservoir is located in the intersection of terrestrial and aquatic ecosystems, and assessing heavy metal pollution in the drown zone is critical for ecological remediation and water conservation. In this study, soils were collected in June and September 2009 in natural recovery area and revegetation area of the WLFZ, and geochemical approaches including geoaccumulation index (I _geo) and factor analysis and soil microbial community structure were applied to assess the spatial variability and evaluate the influence of revegetation on metals in the WLFZ. Geochemical approaches demonstrated the moderate pollutant of Cd, the slight pollutant of Hg, and four types of pollutant sources including industrial and domestic wastewater, natural rock weathering, traffic exhaust, and crustal materials in the WLFZ. Our results also demonstrated significantly lower concentrations for elements of As, Cd, Pb, Zn, and Mn in the revegetation area. Moreover, soil microbial community structure failed to monitor the heavy metal pollution in such a relatively clean area. Our results suggest that revegetation plays an important role in controlling heavy metal pollution in the WLFZ of the Three Gorges Reservoir, China.

Daily CO2 partial pressure and CO2 outgassing in the upper Yangtze River basin: a case study of the Longchuan River, China

Siyue Li et al. — Wed, 01 May 2013 20:38:12 PDT

Rivers have been under sampled to investigate carbon degassing, especially in the tropical and sub-tropical regions. An unprecedented high-temporal-resolution (daily) sampling during July 2008–August 2009 was conducted in the Longchuan River of the upper Yangtze basin, a subtropical monsoon river in China, to reveal the daily-to-seasonal dynamics of the partial pressure of CO₂ (pCO₂) and CO₂ degassing flux from the river using Henry’s constant and CO₂SYS. The pCO₂ levels ranged from 230 to 8300 μatm with an average of 1230 μatm and obvious daily and seasonal variations. More than 92% samples were supersaturated with CO₂ in contrast to the atmospheric equilibrium (380 μatm). pCO₂ values in the river water in the wet season were relatively low, except in the flooding event in November, due to a dilution effect by heavy rainfall. In contrast, the pCO₂ levels in the dry season were much higher, due to lower pH resulted from anthropogenic activities. Net CO₂ degassing and pCO₂ were strongly correlated with dissolved nitrogen, but weakly with water temperature, dissolved inorganic carbon and water discharge, and uncorrelated with particulate nutrients and biogenic elements. The estimated water-to-air CO₂ degassing flux in the Longchuan River was about 27 mol/m²/yr, with the upper limit of 50 mol/m²/yr. Our study also indicated that among the carbon remobilized from land to water, around 7% (2800 t C/yr) of the total carbon was emitted to the atmosphere, 42% (17,000 t C/yr) deposited in the river-reservoirs system and 51% (21,000 t C/yr) exported further downstream. High spatial and temporal resolution of estimates of CO₂ emission from the world large rivers is required due to extremely heterogeneous catchment characteristics and anthropogenic activities in space and time.

Basin ecosystem management in the upper Han River for the South to North Water Division Project, China

Siyue Li et al. — Wed, 01 May 2013 20:32:19 PDT

China implemented the South to North Water Division Project (SNWDP) in 2002, and the three-route (i.e., East, Middle, and West) Project is capable of transferring a total of 41.3 billion m³ of water annually from the water rich Yangtze River to the drought Northern China. The upper Han River basin is the water source area of the SNWDP’s Middle Route, thus its aquatic ecosystem and water quality is of great concern. Field surveys and estimated soil erosion concerned with morphological properties from digital terrain model and land use/land cover were conducted and water quality variables were examined in April and October 2006 respectively in order to determine the major eco-environmental consequences such as land use and soil erosion, water pollution and building of hydropower dams in the basin. Hydroclimatologic data from Ankang and Danjiangkou demonstrated temperature rise of 0.29°C/10 a, and significantly decreases of precipitation and runoff (78×10⁸ m³/10 a) in the recent 30 years. The upper Han River catchment with an erosion intensity of 1980-4400 t/km²/yr, transported 3×10⁸ t/yr of soils to the river, and 40% of the riparian zone in some sub catchment was cultivated though the entire basin had a vegetated coverage of 77%. Moreover, chemical oxygen demand (COD) and nitrogen were the major pollutants in the upper Han River with considerably increases in the past 40 years, which would be further exaggerated by dam construction and global warming. Ultimately, corresponding strategies including proper land use, water pollution control, ecologically sustainable management for hydropower station and establishment of eco-environmental monitoring network were introduced for maintaining a scientifically sound aquatic ecosystem and satisfactory water quality in the upper Han River for the interbasin water transfer project.

Interaction of landscape setting and stream flow seasonality on nitrogen concentrations in a subtropical river, China

Siyue Li et al. — Wed, 01 May 2013 20:19:24 PDT

The upper Han River, with a drainage area of 95, 200 km², has a dominant vegetated land use of forests and shrubs with a total coverage of 81.3%, and agricultural lands, mostly along the riverine network, account for 14% of the total basin area. In this study, water samples were collected in 42 sites during the time period of 2005–2006 in the river, and nitrate-nitrogen and ammonium-nitrogen were determined in situ. Consequently, multivariate statistics analyses were conducted to investigate the interactive influence of landscape setting and stream flow seasonality on nitrogen concentration in river waters. In the high flow period, nitrogen concentrations (NH4+–N andNO3−–N) in stream water were significantly correlated with forest coverage and bare land at the catchment level, and with respect to the riparian zones of 100, 200, 500, 1000-m width they were only significantly correlated with bare land. In the low flow period, nitrogen concentrations were respectively correlated with vegetation and bare land regardless of varying scale landscape settings, and additionallyNH4+–N was significantly related to agricultural land in riparian zones of 500 and 1000-m width. Nevertheless, nitrogen could be predicted using bare land in the high flow period and in the low flow period vegetation was also a critical variable in particular forNH4+–N. Generally, nitrogen was better predictable by land use in the high flow period rather than low flow period, and land use composition within an entire catchment rather than this in the riparian zone was a better predictor of nitrogen concentrations in rivers. Thus, the interaction between landscape setting and water flow seasonality played an important role in regulating nitrogen concentrations in the subtropical river.

China’s huge investment on water facilities: an effective adaptation to climate change, natural disasters, and food security

Siyue Li — Wed, 01 May 2013 19:49:58 PDT

China’s huge investment on water infrastructure for sustainable water use, followed by recently frequent natural disasters, caused worldwide concerns, i.e., continuously published by Nature and Science. Most researchers emphasized challenges on this investment; yet, we argue that the 2011-plan, targeting reservoirs, wells, irrigation systems, inter-basin water transfer projects, is the most effective adaptation to climate change, drought and flooding, as well as food security. This provides a good case of water management and development, particularly for the current uneven water resources and food security by climate change.

Uncertainties of carbon emission from hydroelectric reservoirs

Siyue Li et al. — Wed, 01 May 2013 19:44:04 PDT

Anthropogenic greenhouse gas (GHG) emissions have substantially contributed to intensification of heavy precipitation and thus the risk of flood occurrence, and this anthropogenic climate change is now likely to continue for many centuries. Thus, precise quantification of human-induced GHG emissions is urgently required for modeling future global warming and precipitation changes, which is strongly linked to flood disasters. Recently, GHG evasion from hydroelectric reservoirs was estimated to be 48 Tg C as CO2 and 3 Tg C as CH4 annually, lower than earlier estimate (published in Nature Geoscience; 2011). Here, we analyzed the uncertainties of GHG emissions from hydroelectric reservoirs, that is, reservoir surface area, data paucity and carbon emission relating to ecological zone, and argued that GHG evasion from global hydroelectric reservoirs has been largely under-estimated. Our study hopes to improve the quantification for future researches.