Modeling the impacts of temperature and precipitation changes on soil CO2 fluxes from a Switchgrass stand recently converted from cropland

Switchgrass(Panicum virgatum L.) is a perennial C_4 grass native to North America and successfully adapted to diverse environmental conditions. It offers the potential to reduce soil surface carbon dioxide(CO_2) fluxes and mitigate climate change. However, information on how these CO_2 fluxes respond to changing climate is still lacking. In this study, CO_2 fluxes were monitored continuously from 2011 through 2014 using high frequency measurements from Switchgrass land seeded in 2008 on an experimental site that has been previously used for soybean(Glycine max L.) in South Dakota, USA. DAYCENT, a process-based model, was used to simulate CO_2 fluxes. An improved methodology CPTE[Combining Parameter estimation(PEST) with "Trial and Error" method] was used to calibrate DAYCENT. The calibrated DAYCENT model was used for simulating future CO_2 emissions based on different climate change scenarios. This study showed that:(i) the measured soil CO_2 fluxes from Switchgrass land were higher for 2012 which was a drought year, and these fluxes when simulated using DAYCENT for long-term(2015–2070) provided a pattern of polynomial curve;(ii) the simulated CO_2 fluxes provided different patterns with temperature and precipitation changes in a long-term,(iii) the future CO_2 fluxes from Switchgrass land under different changing climate scenarios were not significantly different, therefore, it can be concluded that Switchgrass grown for longer durations could reduce changes in CO_2 fluxes from soil as a result of temperature and precipitation changes to some extent.     

Introduced trout sever trophic connections in watersheds: consequences for a declining amphibian

Trophic linkages between terrestrial and aquatic ecosystems are increasingly recognized as important yet poorly known features of food webs. Here we describe research to understand the dynamics of lake food webs in relation to a native riparian amphibian and its interaction with introduced trout. The mountain yellow-legged frog Rana muscosa is endemic to alpine watersheds of the Sierra Nevada Mountains and the Transverse Ranges of California, but it has declined to a small fraction of its historical distribution and abundance. Although remaining frogs and introduced trout feed in different habitats of alpine lakes, our stable-isotope analyses clearly show that the same resource base of benthic invertebrates sustains their growth. During one period, insect emergence from naturally fishless lakes was nearly 20-fold higher compared to adjacent lakes with trout, showing that fish reduce availability of aquatic prey to amphibious and terrestrial consumers. Although trout cannot prey on adult frogs due to gape limitation, foraging post-metamorphic frogs are 10 times more abundant in the absence of trout, suggesting an important role for competition for prey by trout in highly unproductive alpine watersheds. Most Sierran lakes contain fish, and those that do not are usually small isolated ponds; in our study, these two lake types supported the lowest densities of post-metamorphic frogs, and these frogs were less reliant on local, benthic sources of productivity. Since Rana muscosa was formerly the most abundant vertebrate in the Sierra Nevada, the reduction in energy flow from lake benthos to this consumer due to fish introductions may have had negative consequences for its numerous terrestrial predators, many of which have also declined. We suggest that disruptions of trophic connections between aquatic and terrestrial food webs are an important but poorly understood consequence of fish introduction to many thousands of montane lakes and streams worldwide and may contribute to declines of native consumers in riparian habitats.     

Persistence,variance and toxic levels of organochlorine pesticides in fluvial sediments and the role of black carbon in their retention

The present study assesses the persistence and variation of organochlorine pesticides (OCPs) and their regulation by total organic carbon (TOC) and black carbon (BC) in freshwater sediment. Sediment samples from the Yamuna River, a major tributary of the Ganges (one of the most populated and intensively used rivers in Asia), had high levels of Σ₂₀OCPs (21.41 to 139.95 ng g^?1). β-Hexachlorocyclohexane (β-HCH) was the most predominant component. ΣHCH and Σdichloro-diphenyl-trichloroethane (DDT) constituted ~86 % of Σ₂₀OCPs. Isomer ratios indicated fresh usage of lindane, DDT and technical-grade HCH. Toxicological comparison with freshwater sediment quality guidelines showed γ-HCH and DDT at high levels of concern. β-HCH, α-HCH, endrin, heptachlor epoxide, dichloro-diphenyl-dichloroethane (DDD), dichloro-diphenyl-dichloroethylene and chlordane were above some of the guideline levels. TOC and BC had mean concentrations of 1.37?±?0.51 % and 0.46?±?0.23 mg g^?1, respectively. BC constituted 1.25 to 10.56 % of TOC. We observed low to moderate correlations of BC with isomers of HCH, p,p′-DDT and methoxychlor while of TOC with Σ₂₀OCPs, γ-HCH, endosulfan sulfate and methoxychlor. Principal component analysis enabled correlating and clustering of various OCPs, BC and TOC. OCP distribution was related with pH, electrical conductivity, soil moisture and finer fractions of sediment. OCPs with similarity in properties that determine their interactions with carbonaceous components of sediment clustered together. A number of factors may, thus, be involved in the regulation of interactive forces between BC and OCPs. BC in this study may be more important than TOC in the retention of some OCPs into fluvial sediments, thereby reducing their bioavailability. The finding is probably the first of its kind to report and emphasises the role of BC in the persistence of OCPs in fluvial sediments.     

Cross-sectional biomonitoring study of pesticide exposures in Queensland,Australia, using pooled urine samples

A range of pesticides are available in Australia for use in agricultural and domestic settings to control pests, including organophosphate and pyrethroid insecticides, herbicides, and insect repellents, such as N,N-diethyl-meta-toluamide (DEET). The aim of this study was to provide a cost-effective preliminary assessment of background exposure to a range of pesticides among a convenience sample of Australian residents. De-identified urine specimens stratified by age and sex were obtained from a community-based pathology laboratory and pooled (n = 24 pools of 100 specimens). Concentrations of urinary pesticide biomarkers were quantified using solid-phase extraction coupled with isotope dilution high-performance liquid chromatography–tandem mass spectrometry. Geometric mean biomarker concentrations ranged from <0.1 to 36.8 ng/mL for organophosphate insecticides, <0.1 to 5.5 ng/mL for pyrethroid insecticides, and <0.1 to 8.51 ng/mL for all other biomarkers with the exception of the DEET metabolite 3-diethylcarbamoyl benzoic acid (4.23 to 850 ng/mL). We observed no association between age and concentration for most biomarkers measured but noted a “U-shaped” trend for five organophosphate metabolites, with the highest concentrations observed in the youngest and oldest age strata, perhaps related to age-specific differences in behavior or physiology. The fact that concentrations of specific and non-specific metabolites of the organophosphate insecticide chlorpyrifos were higher than reported in USA and Canada may relate to differences in registered applications among countries. Additional biomonitoring programs of the general population and focusing on vulnerable populations would improve the exposure assessment and the monitoring of temporal exposure trends as usage patterns of pesticide products in Australia change over time.     

Determination of heavy metals in bee honey with connected and not connected metal wires using inductively coupled plasma atomic emission spectrometry (ICP–AES)

Two honey samples are taken from two parts of the same honeycomb: one that contacts to the surface of the wire and the other taken from the surface that does not contact the wires. Heavy metal contents of these two samples were determined by inductively coupled plasma atomic emission spectrometry). The Mo, Cd, Cr, Fe, Mn, Ni and Zn contents of the honey in contact with wire is higher when compared to the other. Especially, Fe and Zn contents of honey in contact with wire is much higher than the non-contact one. These values are, respectively, 190.21 and 112.76 ppm. Besides, Ni content of honey in contact with wire is approximately 50% higher.     

Physicochemical properties and mineral contents of seven different date fruit (Phoenix dactylifera L.) varieties growing from Saudi Arabia

The date (Phoenix dactylifera L.) fruits (Soukari, Soulag, Barhi, Khulas, Rozaiz, Soughi and Monaif) were evaluated with respect to some physical and chemical properties. While crude protein contents of fruits change between 1.51 % (Soulag) to 2.41 % (Soughi), crude fibre contents ranged between 1.91 % (Soukari) to 3.90 % (Barhi). Vitamin C contents of date samples changed between 971.82 mg/kg (Soughi) to 1,453.15 mg/kg (Barhi). Antioxidant activity of date fruits ranged from 80.07 IC₅₀ (Soukari) to 81.21 IC₅₀ (Soulag). The highest phenolic content was found in Khulas with a mean value of 198 mg GAE/100 g. Energy values of date fruits ranged from 3,725 kcal/kg (Soulag) to 3,870 kcal/kg (Soukari). Sucrose contents of date fruits changed between 1.02 % (Soulag) to 55.71 % (Soukari). Mineral contents of several date fruits were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). Date samples contain potassium at a range between 7,468 mg/kg (Khulas) to 9,619 mg/kg (Soulag). Phosphorus contents of fruits were found between 1,848 mg/kg (Soulag) to 3,066 mg/kg (Rozaiz) and followed by magnesium and calcium. The highest Zn (9.33 mg/kg), Cu (4.27 mg/kg) and Mn (3.26 mg/kg) were found in Rozaiz, Soukari and Barhi samples, respectively.     

Development of database of real-world diesel vehicle emission factors for China

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China,NO_x emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT (Computer Programmer to calculate Emissions from Road Transport) and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5 (Highway Vehicle Particulate Emission Modeling Software) models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent, which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-basedmodels will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.     

Seepage from deep bedded and poultry litter systems

Abstract

The work reported indicates that there could be a potential of ground water pollution by NO₃‐N from turkey facilities built on both sandy and clay soils. At four different depths (30.54, 61.08, 91.62, and 122.16 cm), the NO₃‐N levels for the clay soil were 1572, 497, 66, and 28 ppm, and those for the sandy soil were 293, 425, 324, and 164 ppm, respectively. No significant P increases were observed but there did exist a significant increase of K in the topsoil for both clay and sandy turkey structures. The results show that swine hoop houses with less than three or four years of age may not pose a threat to groundwater pollution due to the leaching of nutrients. The only dairy feedlot sampled in this study, although it has been used for more than 20 years, did not show leaching of NO₃‐N and P. However, it did show a significantly elevated concentration of potassium in the topsoil, as compared to the background sample. More sites should be investigated to verify this.     

Chemistry of Dissolved Organic Carbon at Bear Brook Watershed, Maine: Stream Water Response to (NH4)2SO4 Additions

This study was conducted to determine the response of stream water DOC and organic acidity to increased inputs of ammonium sulfate to a whole catchment. Precipitation, throughfall, soil solutions (from Spodosols) and stream waters were characterized for DOC concentrations and fractions (hydrophobic acids and neutrals, hydrophilic acids, bases, and neutrals) in both the control (East Bear) and the treatment (West Bear) catchments of Bear Brook Watershed, Maine (BBWM), a northern hardwood forest. In all solutions except precipitation, DOC was composed primarily of organic acids, with hydrophobic acids dominating (> 60% of DOC) in forest floor leachates (5000 mol C L-1), and a balance of hydrophobic and hydrophilic acids in deep B horizons and stream waters ( 150 mol C L-1). Stream waters had higher concentrations of DOC during storm or snowmelt events (high discharge), often reaching 300 to 400 mol C L-1. Forest floor leachate C was rapidly attenuated by the mineral soils under all flow conditions, indicating how important mineral soil sorption of DOC was in reducing the loss of C via surface water from BBWM. No differences occurred between control and treatment streams for concentration or composition of DOC due to treatment from 1989 through 1994. In 1995, West Bear Brook had much lower concentrations of DOC than East Bear for the first time. However, this occurred during a year of record low runoff, suggesting that hydrology may have affected export of C. Average annual export of DOC from the catchments was similar (1000 to 2000 mol C ha-1 yr-1). Organic anions in streamwaters increased slightly during high flow events (e.g., East Bear had means of 15 and 19 eq L-1 organic anions during base flow and high discharge in 1995). Treatment of West Bear caused a decrease in organic anions, both in concentration and contribution to overall anion composition (organic anions during high discharge as a percentage of total anions decreased from about 8 to 4% for 1987-89 and 1993-95 samples, respectively). This was probably due to decreased solution pH (greater protonation of organics) and higher concentrations of inorganic anions. Overall, there were no clear, detectable changes in stream water DOC, with only minor changes in organic anions, as a result of treatment with ammonium sulfate.