Xiying Hao

Distribution of sulfamethazine, chlortetracycline and tylosin in manure and soil of Canadian feedlots after subtherapeutic use in cattle

Feedlots are potential point sources for the flow of antibiotics into the environment due to common use of antibiotics such as sulfamethazine, chlortetracycline and tylosin. Hence soils and manures originating from a grassland control, an experimental and a commercial feedlot were analyzed and mass balances were calculated for these antibiotics. Up to 9990 microg kg(-1) sulfamethazine and 401microg kg(-1) chlortetracycline on a dry matter basis were determined in feedlot manure. Soil concentrations were two orders of magnitude smaller. This corresponds to 7-40% of the calculated residual amount. In the commercial feedlot chlortetracycline was found down to soil depths of -40 cm; sulfamethazine was still detectable 1 year after medication. Sulfamethazine and chlortetracycline were additionally determined in manure of a control treatment in the experimental feedlot where cattle never received antibiotics. This was attributed to runoff from upslope pens. Consequently, antibiotics partially persist within feedlots and may be dislocated into the surrounding environment by vertical transport and runoff.

Trace element changes in soil after long-term cattle manure applications.

Manure application supplies plant nutrients, but also leads to trace element accumulation in soil. This study investigated total and EDTA-extractable B, Cd, Co, Cu and Zn in soil after 25 annual manure applications. The residual effect of 14 annual manure applications followed by 11 yr with no applications was also investigated. Manure was applied at 0, 30, 60 and 90 Mg ha(-1) yr(-1) (wet weight) under rainfed (treatments Mr0, Mr30, Mr60, and Mr90) and at 0, 60, 120 and 180 Mg ha(-1) yr(-1) under irrigated conditions (Mi0, Mi60, Mi120, and Mi180). The manure applications had no significant effect on soil B, Cd and Co content under both rainfed and irrigated conditions, but significantly increased total Cu and Zn content under irrigated conditions with Zn in Mi120 and Mi180 reaching the lower maximum concentration (MAC) level set by the European Community. Manure application also significantly increased EDTA-extractable Cd and Zn content in soil. Up to 27% of the total Cd (0.156 mg kg(-1)) and 21% of total Zn (38 mg kg(-1)) are found in EDTA-extractable form (Mi180 at 0-15 cm). EDTA-extractable Cd and Zn content was also significantly elevated in the irrigated residual plots due to the higher manure rates used. Thus, the impacts of cattle manure application on trace elements in soil are long lasting. Elevated Cd and Zn are a concern as other studies have linked them with certain types of cancers and human illnesses.

Bioaugmentation with an anaerobic fungus in a two-stage process for biohydrogen and biogas production using corn silage and cattail

Bioaugmentation with an anaerobic fungus, Piromyces rhizinflata YM600, was evaluated in an anaerobic two-stage system digesting corn silage and cattail. Comparable methane yields of 328.8±16.8mLg(-1)VS and 295.4±14.5mLg(-1)VS and hydrogen yields of 59.4±4.1mLg(-1)VS and 55.6±6.7mLg(-1)VS were obtained for unaugmented and bioaugmented corn silage, respectively. Similar CH4 yields of 101.0±4.8mLg(-1)VS and 104±19.1mLg(-1)VS and a low H2 yield (<1mLg(-1)VS) were obtained for unaugmented and bioaugmented cattail, respectively. However, bioaugmentation resulted in an initial increase in CH4 and H2 production rates and also increased volatile fatty acid degradation rate for both substrates. Our study demonstrates the potential of bioaugmentation with anaerobic fungus for improving the digestibility of lignocellulose substrates for biogas and biohydrogen production.

Land-use type and temperature affect gross nitrogen transformation rates in Chinese and Canadian soils

Land-use type affects gross nitrogen transformation and this information is particularly lacking under varied low temperature conditions. In this study, the effects of land-use type (forest vs. grassland) and temperature (10 vs. 15°C) on gross N transformation rates under aerobic conditions were investigated using the 15N isotope pool dilution technique in the laboratory. Soils were collected from forest and grassland sites in China and Canada. The results showed that gross N mineralization and immobilization rates were significantly higher in forest soils than in grassland soils, while the reverse was true for gross nitrification rates. The higher TC and lower SOCw concentrations in the Chinese soils relative to the Canadian soils were related to the greater gross N mineralization rates and lower gross N immobilization rates in Chinese soils. The greater gross N mineralization rates and lower gross N immobilization rates resulted in much higher inorganic N accumulation and that may increase the risk of NO3− leaching in the Chinese soils. Increasing temperature significantly increased gross nitrification rates in grassland soils and gross N immobilization rates in forest soils, suggesting that grassland soils maybe more vulnerable to N loss through NO3− leaching or denitrification (when conditions for denitrification exist) and that conversion of grassland to forest soils may exert less negative effects on the environment by promoting the retention of N and decreasing the production of NO3− and subsequently the risk of NO3− leaching under increasing temperature by global warming.

Anaerobic digestion of specified risk materials with cattle manure for biogas production.

Biogas production from anaerobic digestion (AD) of specified risk materials (SRM) co-digested with cattle manure was assessed in a 3 x 2 factorial design. SRM replaced manure at 0 (control), 10% or 25% (w/w) as the substrate fed to six 2-L biodigesters maintained at 37 degrees C or 55 degrees C. Digesters were fed substrate (30 g L(-1) total volatile solids) at 6-d intervals for 90 d, with a retention time of 30 d. Keratin (<20mg) was added to each digester to model the degradation of beta-sheet rich proteins. Methane production was measured daily, and effluent was collected at feeding to monitor SRM degradation using real-time PCR analysis of bovine-specific DNA fragments. Compared with control, methane production increased by 83% or 161% (P<0.05) with 10% or 25% SRM at 37 degrees C, and by 45% and 87%, respectively, at 55 degrees C (P<0.05). Bovine DNA degradation over 6d was higher (P<0.05) at 37 degrees C as compared to 55 degrees C. Dry matter degradation of keratin at 37 degrees C decreased with increasing SRM concentration (P<0.05), whereas at 55 degrees C no difference between treatments was observed (P>0.05). Inclusion of SRM increases the production of methane during the anaerobic digestion of manure and may offer a means of deriving economic value from the disposal of SRM.

Effects of pre-exposure to ultraviolet-B radiation on responses of tomato (Lycopersicon esculentum cv. New Yorker) to ozone in ambient and elevated carbon dioxide.

Patterns of environmental change in the biosphere include concurrent and sequential combinations of increasing ultraviolet (UV-B) and ozone (O(3)) at increasing carbon dioxide (CO(2)) levels; long-term changes are resulting mainly from stratospheric O(3) depletion, greater tropospheric O(3) photochemical synthesis, and increasing CO(2) emissions. Effects of selected combinations were evaluated in tomato (Lycopersicon esculentum cv. New Yorker) seedlings using sequential exposures to enhanced UV-B radiation and O(3) in differential CO(2) concentrations. Ambient (7.2 kJ m(-2 )day(-1)) or enhanced (13.1 kJ m(-2) day(-1)) UV-B fluences and ambient (380 microl l(-1)) or elevated (600 microl l(-1)) CO(2) were imposed for 19 days before exposure to 3-day simulated O(3) episodes with peak concentrations of 0.00, 0.08, 0.16 or 0.24 microl l(-1) O(3) in ambient or elevated CO(2). CO(2) enrichment increased dry mass, leaf area, specific leaf weight, chlorophyll concentration and UV-absorbing compounds per unit leaf area. Exposure to enhanced UV-B increased leaf chlorophyll and UV-absorbing compounds but decreased leaf area and root/shoot ratio. O(3) exposure generally inhibited growth and leaf photosynthesis and did not affect UV-absorbing compounds. The highest dose of O(3) eliminated the stimulating effect of CO(2) enrichment after ambient UV-B pre-exposure on leaf photosynthesis. Pre-exposure to enhanced UV-B mitigated O(3) damage to leaf photosynthesis at elevated CO(2).

Effects of age of cattle, turning technology and compost environment on disappearance of bone from mortality compost.

As residual bones in mortality compost negatively impact subsequent tillage, two studies were performed. For the first study, windrows of mature cattle or calves were placed on a base of barley straw and covered with beef manure. Windrows were divided into two sections and turned at 3-month intervals. Approximately 5000 kg of finished compost per windrow was passed through a 6mm trommel screen, with bones collected and weighed. Bone weight was 0.66% of mature cattle compost and 0.38% of calf compost on a dry matter basis, but did not differ after adjustment for weights of compost ingredients. In a subsequent study, four windrows were constructed containing mortalities, straw and beef manure (STATC) or straw, manure and slaughter waste (STATW). Also, straw, beef manure and slaughter waste was added to an 850 L rolling drum composter (DRUMW). Fresh bovine long-bones from calves were collected, weighed and embedded in the compost. Bones were retrieved and weighed when windrows were turned, or with DRUMW, after 8 weeks. Temperatures achieved followed the order STATW>STATC>DRUMW (p<0.05). Rate of bone disappearance followed a pattern identical to temperature, with the weight of bones in STATW declining by 53.7% during 7 weeks of composting. For STATC, temperatures were uniform over three composting periods, but bone disappearance was improved (p<0.05) when compost dry matter was lower (46%), as compared to 58%. Using a ratio of five parts manure to one part mortalities, results of this study demonstrated that residual bone was <1% of cured cattle compost and may be reduced by maintaining a high compost temperature and moisture content.

Open-Air Windrows for Winter Disposal of Frozen Cattle Mortalities: Effects of Ambient Temperature and Mortality Layering

After imposition of fees for disposal of cattle carcasses by the rendering industry, on-farm methods of mortality disposal are being investigated. Three open-air mortality compost windrows were constructed in January (JAN) and February (FEB) of 2004 in the cold, semiarid climate of southern Alberta, Canada. Windrow A included a base of barley straw a minimum of 46 cm thick, a layer of cattle mortalities (n=12) and a layer of stockpiled manure (minimum of 46 cm) covering the mortalities. Windrows B and C also had a bottom layer of barley straw, with windrow B containing 9 mortalities in 2 layers and windrow C containing 12 mortalities in 3 layers. Due to ambient temperatures > 0°C, carcasses (range 236 to 673 kg) were frozen at the time of windrow construction. Type ‘T’ thermocouples were embedded at the base of B and C windrows and temperatures within 120 cm of the surface were measured using a stainless steel dial probe. Windrows were turned 3 times at 3 mo intervals. Samples were collected from initial compost amendments and prior to each turning for determination of dry matter (DM), organic matter (OM), N, C and coliform bacteria. Ambient temperature was 13°C higher (P < 0.05) for the initial heating of FEB as compared to JAN compost, although the rate of compost temperature decline did not differ between replicates in this period. Days at maximum temperature did not differ between replicates and maximum temperatures in all windrows exceeded 55°C. After 3 heating periods and 9 mo, flesh was not evident and only fragments of bones (max wt. 740 g) were found. Results of this study demonstrate that ambient temperatures < 0°C and frozen mortalities provide no barrier to the use of open-air windrows for disposal of cattle mortalities. As well, stacking up to 3 layers of full-sized cattle mortalities in a windrow did not affect temperature profiles, residual flesh or bone, or analyses of the finished compost. Under the climatic conditions of southern Alberta, layering mortalities would reduce space requirements for large-animal mortality composting in a feedlot setting.

Influence of increasing temperature and nitrogen input on greenhouse gas emissions from a desert steppe soil in Inner Mongolia

We investigated the effect of increasing soil temperature and nitrogen on greenhouse gas (GHG) emissions [carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)] from a desert steppe soil in Inner Mongolia, China. Two temperature levels (heating versus no heating) and two nitrogen (N) fertilizer application levels (0 and 100 kg N ha−1 year−1) were examined in a complete randomized design with six replications. The GHG surface fluxes and their concentrations in soil (0 to 50 cm) were collected bi-weekly from June 2006 to November 2007. Carbon dioxide and N2O emissions were not affected by heating or N treatment, but compared with other seasons, CO2 was higher in summer [average of 29.6 versus 8.6 mg carbon (C) m−2 h−1 over all other seasons] and N2O was lower in winter (average of 2.6 versus 4.0 mg N m−2 h−1 over all other seasons). Desert steppe soil is a CH4 sink with the highest rate of consumption occurring in summer. Heating decreased CH4 consumption only in the summer. Increasing surface soil temperature by 1.3°C or applying 100 kg ha−1 year−1 N fertilizer had no effect on the overall GHG emissions. Seasonal variability in GHG emission reflected changes in temperature and soil moisture content. At an average CH4 consumption rate of 31.65 µg C m−2 h−1, the 30.73 million ha of desert steppe soil in Inner Mongolia can consume (sequestrate) about 85 × 106 kg CH4-C, an offset equivalent to 711 × 106 kg CO2-C emissions annually. Thus, desert steppe soil should be considered an important CH4 sink and its potential in reducing GHG emission and mitigating climate change warrants further investigation.

Microbial communities and greenhouse gas emissions associated with the biodegradation of specified risk material in compost

Provided that infectious prions (PrP(Sc)) are inactivated, composting of specified risk material (SRM) may be a viable alternative to rendering and landfilling. In this study, bacterial and fungal communities as well as greenhouse gas emissions associated with the degradation of SRM were examined in laboratory composters over two 14 day composting cycles. Chicken feathers were mixed into compost to enrich for microbial communities involved in the degradation of keratin and other recalcitrant proteins such as prions. Feathers altered the composition of bacterial and fungal communities primarily during the first cycle. The bacterial genera Saccharomonospora, Thermobifida, Thermoactinomycetaceae, Thiohalospira, Pseudomonas, Actinomadura, and Enterobacter, and the fungal genera Dothideomycetes, Cladosporium, Chaetomium, and Trichaptum were identified as candidates involved in SRM degradation. Feathers increased (P<0.05) headspace concentrations of CH4 primarily during the early stages of the first cycle and N2O during the second. Although inclusion of feathers in compost increases greenhouse gas emissions, it may promote the establishment of microbial communities that are more adept at degrading SRM and recalcitrant proteins such as keratin and PrP(Sc).