Abstract  Responsible for 6% of U.S. greenhouse gas (GHG) production, agricultural land use has significant potential to reduce these emissions and capture additional carbon in the soil. Many different activities have been proposed for such mitigation, but assessments of the biophysical potential have been limited and have not provided direct comparison among the many options. We present an in-depth review of the scientific literature, with a side-by-side comparison of net biophysical GHG mitigation potential for 42 different agricultural land management activities in the United States, many of which are likely applicable in other regions. Twenty of these activities are likely to be beneficial for GHG mitigation and have sufficient research to support this conclusion. Limited research leads to uncertainty for 15 other activities that may have positive mitigation potential, and the remaining activities have small or negative GHG mitigation potential or life-cycle GHG concerns. While we have sufficient information to move forward in implementing a number of activities, there are some high-priority research needs that will help clarify problematic uncertainties.

Abstract  This article addresses different land use change scenarios, as well as uncertainty issues related to parameters and concerning how co-product credits are accounted for in the life-cycle modeling of rapeseed oil (RO). A comprehensive assessment of different land use change scenarios (rapeseed cultivation in former agricultural land and grassland) and agricultural practices has been conducted, which results in different carbon stock change values. RO GHG intensity and GHG emission implications when RO displaces petroleum diesel have been assessed in terms of probability distributions using a substitution method, three allocation approaches and ignoring co-product credits. The net GHG balance of rapeseed oil is strongly influenced by soil carbon stock variations due to land use change and by the magnitude of nitrous oxide emissions from cultivated soil. Depending on prior land use, GHG emissions may comply with the European renewable energy directive target of 35% GHG emission savings (arable land converted to rapeseed cultivation) or, conversely, may completely offset carbon gains attributed to rapeseed oil production for several decades (conversion of grassland).

Abstract  Jatropha curcas L. will be cultivated in large parts of the central highlands of Chiapas (Mexico) so that its seeds can be extracted for biofuel. Little is known how the cultivation of J. curcas, which contains phorbolesters, might affect soil processes. Soil was sampled at five locations and amended with leaves of J. curcas while dynamics of ammonium (NH(4)(+)), nitrite (NO(2)(-)) and nitrate (NO(3)(-)) and emissions of carbon dioxide (CO(2)), methane (CH(4)) and nitrous oxide (N(2)O), well known greenhouse gasses, were monitored. If we considered no priming effect, then between 12 and 31% of the C added with Jatropha leaves mineralized within 56 days. However, the concentration of mineral N (sum of NH(4)(+), NO(2)(-) and NO(3)(-)) did not increase in the Jatropha-amended soils compared to the unamended soils. The mean CO(2) emission rate increased significantly 3.7 times when Jatropha leaves were added to the different soils. The N(2)O emission was low in the unamended soil and remained <5 mu g N(2)O-N kg(-1). Application off. curcas leaves increased the N(2)O emission rate significantly in two soils, but not in the other three. Oxidation of CH(4) occurred in each of the unamended soils with the fastest decrease generally found within the first day. Application of Jatropha leaves had no significant effect on oxidation of CH(4), except in one soil. It was found that application of Jatropha leaves did increase emission of CO(2), did not affect the soil mineral N content and had only an increasing effect on emission of N(2)O and oxidation of CH(4) in some soils. (C) 2010 Elsevier B.V. All rights reserved.

Abstract  Production of biochar (the carbon (C)-rich solid formed by pyrolysis of biomass) and its storage in soils have been suggested as a means of abating climate change by sequestering carbon, while simultaneously providing energy and increasing crop yields. Substantial uncertainties exist, however, regarding the impact, capacity and sustainability of biochar at the global level. In this paper we estimate the maximum sustainable technical potential of biochar to mitigate climate change. Annual net emissions of carbon dioxide (CO(2)), methane and nitrous oxide could be reduced by a maximum of 1.8 Pg CO(2)-C equivalent (CO(2)-C(e)) per year (12% of current anthropogenic CO(2)-C(e) emissions; 1 Pg=1 Gt), and total net emissions over the course of a century by 130 Pg CO(2)-C(e), without endangering food security, habitat or soil conservation. Biochar has a larger climate-change mitigation potential than combustion of the same sustainably procured biomass for bioenergy, except when fertile soils are amended while coal is the fuel being offset.

Abstract  The environmental impacts of remediation of a chloroethene-contaminated site were evaluated using life cycle assessment (LCA). The compared remediation options are (i) in situ bioremediation by enhanced reductive dechlorination (ERD), (ii) in situ thermal desorption (ISTD), and (iii) excavation of the contaminated soil followed by off-site treatment and disposal. The results showed that choosing the ERD option will reduce the life-cycle impacts of remediation remarkably compared to choosing either ISTD or excavation, which are more energy-demanding. In addition to the secondary impacts of remediation, this study includes assessment of local toxic impacts (the primary impact) related to the on-site contaminant leaching to groundwater and subsequent human exposure via drinking water. The primary human toxic impacts were high for ERD due to the formation and leaching of chlorinated degradation products, especially vinyl chloride during remediation. However, the secondary human toxic impacts of ISTD and excavation are likely to be even higher, particularly due to upstream impacts from steel production. The newly launched model, USEtox, was applied for characterization of primary and secondary toxic impacts and combined with a site-dependent fate model of the leaching of chlorinated ethenes from the fractured clay till site.

Abstract  The relationship between forests and human nutrition is not yet well understood. A better understanding of this relationship is vital at a time when the majority of new land for agriculture is being cleared from forests. We use Demographic Health Survey data on food consumption for children from 21 African countries and Global Land Cover Facility tree cover data to examine the relationship between tree cover and three key indicators of nutritional quality of children's diets: dietary diversity, fruit and vegetable consumption, and animal source food consumption. Our main findings can be summarized as follows: there is a statistically significant positive relationship between tree cover and dietary diversity; fruit and vegetable consumption increases with tree cover until a peak of 45% tree cover and then declines; and there is no relationship between animal source food consumption and tree cover. Overall our findings suggest that children in Africa who live in areas with more tree cover have more diverse and nutritious diets. (C) 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

Abstract  We tested the scaling effects of proximate desertification drivers (i.e. soil erosion, bush encroachment and grazing pressure) on soil nutrients in northeastern Tanzania. We analyzed nutrient concentrations in the desertified and non-degraded benchmark. For the desertified landscapes we analyzed nutrient concentrations at the coarse (landscape), medium (micro-landscape) and sampling unit (fine scale) levels. Further, for the desertified micro-landscapes, we used the differences in total nutrient concentrations to identify moderately dysfunctional and dysfunctional micro-landscapes. The desertified micro-landscapes had an overall lower soil organic matter, total nitrogen and exchangeable phosphorus, and soil water, but had elevated cation exchange capacity and soluble bases compared with the benchmark. Different intensities of desertification processes, mediated by the three proximate desertification drivers, produced varied amounts of nutrients Corresponding with moderately dysfunctional and dysfunctional micro-landscapes, The dysfunctional micro-landscapes had the lowest nutrient availability. The effects of proximate desertification drivers on pooled nutrients were scale-independent. For individual nutrients only pH, soil water and Mg++ showed scaling effects at the coarse OF medium scales for soil erosion, while for grazing pressure pH, soil water, CEC, Na+, Mg2++ and Ca2++, showed scale dependence. The scaling effects were interlinked with landscape processes that operated simultaneously and interactively with different drivers. (c) 2008 Elsevier Ltd. All rights reserved.

Abstract  Landscape-level variables operating at multiple spatial scales likely influence wetland amphibian assemblages but have not been investigated in detail. We examined the significance of habitat loss and fragmentation, as well as selected within-wetland conditions, affecting amphibian assemblages in twenty-one glacial marshes. Wetlands were located within urban and agricultural regions of central and southwestern Minnesota, USA and were distributed across two ecoregions: tallgrass prairie and northern hardwood forest. We surveyed amphibian assemblages and used a geographic information system to quantify land-use variables at three scales: 500, 1000, and 2500 m. Ten species of amphibians were detected, the most abundant being Rana pipiens, Ambystoma tigrinum, and Bufo americanus. Amphibian species richness was lower with greater wetland isolation and road density at all spatial scales in both ecoregions. Amphibian species richness also had a negative relationship with the proportion of urban land-use at all spatial scales in the hardwood forest ecoregion, and species richness was greater in wetlands with fish and Ambystoma tigrinum. These biotic relationships are less consistent and more difficult to interpret than are land-use relationships. The data presented here suggest that decreases in landscape connectivity via fragmentation and habitat loss can affect amphibian assemblages, and reversing those landscape changes should be an important part of a regional conservation strategy.

Abstract  Simulations have shown that it should be possible (within a relatively short time frame) to profitably synthesize high-purity carbon-neutral ethanol, gasoline, jet fuel, propylene, and many other hydrocarbons, in volumes that cannot be matched by any other renewable avenue, from captured CO2, water, and cheap off-peak low-carbon energy, notably form wind farms. The process, dubbed Wind Fuels, requires no biomass, and it is expected to solve the grid stability and energy storage challenges of wind energy. The process is based largely on the commercially proven technologies of wind energy, water electrolysis, and Fischer Tropsch Synthesis (FTS) chemistry. Wind energy is used to electrolyze water into hydrogen and oxygen. Some of the hydrogen is used in a process, the so-called reverse water gas shift (RWGS) reaction, that reduces CO2 to carbon monoxide (CO) and water. The CO and the balance of the hydrogen are fed into an FT reactor, similar to that commonly used to produce fuels and chemicals from coal or natural gas. Improved sub-processes have been simulated in detail, and key experiments will soon be carried out to help optimize process conditions. Conversion efficiencies (from input electrical to output chemical) are expected to approach 60%. Putting renewable hydrogen into liquid fuels solves the distribution and storage problems that have beset utilization of hydrogen in vehicles. Converting CO2 into fuels can eliminate the need for CO2 sequestration and reduce global CO2 emissions by 40% by mid-century. The amount of water needed for the renewable FTS (UTS) process is an order of magnitude less than needed for biofuels. The atmosphere will eventually provide an unlimited source for CO2, though initially the CO2 would come from ammonia plants, biofuel refineries, cement factories, fossil power plants, and ore refineries. When the input energy is from off-peak wind and reasonable monetary credit is included for climate benefit, Wind Fuels could compete when petroleum is as low as $45/bbl.

Abstract  A common goal of water and energy management is to maximize the supply of one while minimizing the use of the other, so it is important to understand the relationship between water use and energy production. A larger proportion of horizontal wells and an increasing number of hydraulically fractured well bores are being completed in the United States, and consequently increasing water demand by oil and gas operations. Management, planning, and regulatory decisions for water, oil, and gas are largely made at the state-level; therefore, it is necessary to aggregate water use and energy production data at the state-scale. The purpose of this paper is to quantify annual volumes of water used for completion of oil and gas wells, coproduced during oil and gas production, injected via underground injection program wells, and used in water flooding operations. Data from well completion reports, and tax commission records were synthesized to arrive at these estimates for Oklahoma. Hydraulic fracturing required a median fluid volume of 11,350 m(3) per horizontal well in Oklahoma. Median fluid volume (~15,774 m(3)) and volume per perforated interval (15.73 m(3) m(-1)) were highest for Woodford Shale horizontal wells. State-scale annual water use for oil and gas well completions was estimated to be up to 16.3 Mm(3) in 2011 or less than 1% of statewide freshwater use. Statewide annual produced water volumes ranged from 128.5 to 146.6 Mm(3), with gas wells yielding an estimated 72.4% of the total coproduced water. Volumes of water injected into underground injection control program wells ranged from 206.8 to 305.4 Mm(3), which indicates that water flooding operations may use up to 167.0 Mm(3) per year. State-scale water use estimates for Oklahoma could be improved by requiring oil and gas operators to supplement well completion reports with water use and water production data. Reporting of oil and gas production data by well using a unique identifier (i.e., API number) would also allow for refinement of produced water quantity information. Reporting of wastewater disposal and water flooding volumes could be used to further develop state-scale water accounting and best management practices.

Abstract  To quantify the consequences of erosion and vegetation restoration on ecosystem C dynamics (a key element in understanding the terrestrial C cycle), field measurements were collected since 1959 at two experimental sites set up on highly disturbed barren land in South China. One site had received vegetation restoration (the restored site) while the other received no planting and remained barren (the barren site). The Erosion-Deposition Carbon Model (EDCM) was used to simulate the ecosystem C dynamics at both sites. The on-site observations in 2007 showed that soil organic C (SOC) storage in the top 80-cm soil layer at the barren site was 50.3 +/- 3.5 Mg C ha(-1), half that of the restored site. The SOC and surface soil loss by erosion at the restored site from 1959 to 2007 was 3.7 Mg C ha(-1) and 2.2 cm, respectively-one-third and one-eighth that of the barren site. The on-site C sequestration in SOC and vegetation at the restored site was 0.67 and 2.5 Mg C ha(-1) yr(-1), respectively, from 1959 to 2007, driven largely by tree growth and high atmospheric N deposition in the study area. Simulated findings suggested that higher N deposition resulted in higher on-site SOC storage in the soil profile (with SOC in the top 20-cm layer increasing more significantly), and higher on-site ecosystem C sequestration as long as N saturation was not reached. Lacking human-induced vegetation recovery, the barren site remained as barren land from 1959 to 2007 and the on-site C decrease was 0.28 Mg C ha(-1) yr(-1). Our study clearly indicated that vegetation restoration and burial by soil erosion provide a large potential C sink in terrestrial ecosystems.

Abstract  Salts are frequently a major constituent of waste waters produced during oil and gas production. These produced waters or brines must be treated and/or disposed and provide a daily challenge for operators and resource managers. Some elements of salts are regulated with water quality criteria established for the protection of aquatic wildlife, e.g. chloride (Cl-), which has an acute standard of 860 mg/L and a chronic standard of 230 mg/L However, data for establishing such standards has only recently been studied for other components of produced water, such as bicarbonate (HCO3-), which has acute median lethal concentrations (LC50s) ranging from 699 to >8000 mg/L and effects on chronic toxicity from 430 to 657 mg/L While Cl- is an ion of considerable importance in multiple geographical regions, knowledge about the effects of hardness (calcium and magnesium) on its toxicity and about mechanisms of toxicity is not well understood. A multiple-approach design that combines studies of both individuals and populations, conducted both in the laboratory and the field, was used to study toxic effects of bicarbonate (as NaHCO3). This approach allowed interpretations about mechanisms related to growth effects at the individual level that could affect populations in the wild. However, additional mechanistic data for HCO3- related to the interactions of calcium (Ca2+) precipitation at the microenvironment of the gill would dramatically increase the scientific knowledge base about how NaHCO3 might affect aquatic life. Studies of the effects of mixtures of multiple salts present in produced waters and more chronic effect studies would give a better picture of the overall potential toxicity of these ions. Organic constituents in hydraulic fracturing fluids, flowback waters, etc. are a concern because of their carcinogenic properties and this paper is not meant to minimize the importance of maintaining vigilance with respect to potential organic contamination. Published by Elsevier B.V.

Abstract  From the perspective of the biorefinery, the inherent heterogeneity of mixed-species feedstocks increases the apparent risk associated with their use due to the difficulty in predicting processing characteristics, potential yields and digestibility. These materials often contain species from different botanical classifications, which could affect pretreatment efficiency and Saccharification yields. For this study, we evaluated the impact of ammonia fiber expansion (AFEX (TM)(1)) pretreatment conditions on hydrolysis sugar yields for five early successional old-field treatment replicates, each comprised of a different mixture of annual forb and grass species. Yields from these samples were also compared to a late successional old field sample and to corn stover that had been pretreated at the same conditions. Relatively high sugar yields were obtained for four of the five early successional feedstocks when pretreated at the same conditions: 2.0 g NH3:g DM; 0.5 g H2O:g DM; 100 degrees C; 30 min. It was found that glucan digestibility was strongly inversely correlated to the total lignin content; however this was not true of the xylan digestibility. The mixed-species feedstocks that had a higher grass content tended to also have a higher structural sugar content and were more digestible than forb-dominated feedstocks, thereby resulting in higher saccharification yields. Also, the grass-dominated mixed-species feedstocks were as digestible as corn stover (similar to 80% total sugar yields). However, due to its higher structural sugar content, corn stover had higher total glucose and xylose yields (580 g/kg biomass) compared to the mixed-species feedstocks, which ranged from 290 to 470 g/kg biomass. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Duckweed, a small floating aquatic plant, is a novel bioenergy crop with great potential to accumulate starch. Three factors involved in the growth and starch accumulation of duckweed were investigated in the field: population, harvesting frequency and nutrient supply. Under identical conditions, Landoltia S3 had the highest maximum growth rate at 30.35 g/m(2)/week; Lemna P1 had the highest N and P absorption rates at 0.622 gN/m(2)/week and 0.135 gP/m(2)/week, respectively; Landoltia OT had the highest starch accumulation rate at 3.88 g/m(2)/week. The protein and P contents in each population decreased as the growth rate slowed. Different harvesting frequencies resulted in different growth rates. However, their biomass had almost the same composition. The addition of 15, 30 and 45 ppm NH4+-N inhibited the growth of duckweed. The addition of CaO or microelements dramatically increased duckweed growth. By adding microelements, duckweed could grow in cold weather for an increased time period. With pond water and no sediment supply, duckweed reached the highest starch content of 52.9% with the lowest growth rate, which was the highest starch content in duckweed in the field in literatures. Starch content was negatively correlated with the growth rate, protein and P contents, which suggests that a high growth rate and high starch content in duckweed could hardly be acquired simultaneously. According to this systemic study, an operation process for harvesting high starch duckweed was proposed, paving the way for the large scale exploitation and application of duckweed in bioenergy and feed. (C) 2013 Elsevier B.V. All rights reserved.

Abstract  HEEP COPYRIGHT: BIOL ABS. NOTE HUMAN

Abstract  We quantify the impact of land-use change, determined by our growing demand for food and biofuel production, on isoprene emissions and subsequent atmospheric oxidant chemistry in 2015 and 2030, relative to 1990, ignoring compound climate change effects over that period. We estimate isoprene emissions from an ensemble (n = 1000) of land-use change realizations from 1990-2050, broadly guided by the IPCC AR4/SRES scenarios A1 and B1. We also superimpose land-use change required to address projected biofuel usage using two scenarios: (1) assuming that world governments make no changes to biofuel policy after 2009, and (2) assuming that world governments develop biofuel policy with the aim of keeping equivalent atmospheric CO2 at 450 ppm. We present the median and interquartile range (IQR) statistics of the ensemble and show that land-use change between -1.50 x 10(12) m(2) to +6.06 x 10(12) m(2) was found to drive changes in the global isoprene burden of -3.5 to +2.8 Tgyr(-1) in 2015 and -7.7 to +6.4 Tgyr(-1) in 2030. We use land-use change realizations corresponding to the median and IQR of these emission estimates to drive the GEOS-Chem global 3-D chemistry transport model to investigate the perturbation to global and regional surface concentrations of isoprene, nitrogen oxides (NO+NO2), and the atmospheric concentration and deposition of ozone (O-3). We show that across subcontinental regions the monthly surface O-3 increases by 0.1-0.8 ppb, relative to a zero land-use change calculation, driven by increases (decreases) in surface isoprene in high (low) NOx environments. At the local scale (4 degrees x 5 degrees) we find that surface O-3 increases by 5-12 ppb over temperate North America, China and boreal Eurasia, driven by large increases in isoprene emissions from short-rotation coppice crop cultivation for biofuel production.

Abstract  Sequestering atmospheric CO2 is necessitated by its present concentration of 385 ppm and increasing at the rate of 2 ppm y(-1). Increase in atmospheric emission of CO2 with the attendant global warming and environmental degradation are driven by global energy demand. In comparison with the emission of 300 Pg C between 1850 and 2000, total emission during the 21(st) century is estimated at 950 to 2195 Pg, with an annual rate of emission of 20 to 35 Pg C y(-1). Reduction of CO2 atmospheric loading can be achieved by biological, chemical and technological options through either reducing or sequestering emissions. This article describes technological options of sequestering atmospheric CO2 into other global pools. Geologic sequestration involves underground storage of industrially emitted CO2 into the geosphere for long-term and secure storage. Liquefied CO2 is injected about 1000 m below the ground surface either in stable porous rocks, oil wells, coal beds, or saline aquifers. Co-injecting CO2 along with H2S and SO2 is also possible. Over time, the trapped CO2 reacts with minerals to form carbonates, enhances oil recovery, or displaces coal bed methane. Deep injection of CO2 under the ocean creates a CO2 lake which eventually penetrates into the sediments. Iron fertilization is another technique of enhancing the C pool in marine biota, notably phytoplankton. The so-called "biological pumping'' is based on the "iron hypothesis'' of transferring C to the ocean floor. Terrestrial C sequestration is based on the natural process of photosynthesis. Transfer of CO2 into the biotic pool and soil C pool via humification and formation of secondary carbonates has numerous ancillary benefits through enhancement of ecosystem services. Soil C sequestration is essential to improving soil quality, increasing use efficiency of agronomic input, and advancing world food security. It is also needed to improve water quality by filtration and denaturing of pollutants, and enhancing biodiversity by saving land for nature conservancy. Soil C sequestration is a low hanging fruit, and a bridge to the future until low-C or no-C fuel sources take effect.

Abstract  The Environmental Protection Agency (EPA) is promulgating today's final rule, the Stage 2 Disinfectants and Disinfection Byproducts Rule (DBPR), to provide for increased protection against the potential risks for cancer and reproductive and developmental health effects associated with disinfection byproducts (DBPs). The final Stage 2 DBPR contains maximum contaminant level goals for chloroform, monochloroacetic acid and trichloroacetic acid; National Primary Drinking Water Regulations, which consist of maximum contaminant levels (MCLs) and monitoring, reporting, and public notification requirements for total trihalomethanes (TTHM) and haloacetic acids (HAA5); and revisions to the reduced monitoring requirements for bromate. This document also specifies the best available technologies for the final MCLs. EPA is also approving additional analytical methods for the determination of disinfectants and DBPs in drinking water. EPA believes the Stage 2 DBPR will reduce the potential risks of cancer and reproductive and developmental health effects associated with DBPs by reducing peak and average levels of DBPs in drinking water supplies. The Stage 2 DBPR applies to public water systems (PWSs) that are community water systems (CWSs) or nontransient noncommunity water systems (NTNCWs) that add a primary or residual disinfectant other than ultraviolet light or deliver water that has been treated with a primary or residual disinfectant other than ultraviolet light. This rule also makes minor corrections to drinking water regulations, specifically the Public Notification tables. New endnotes were added to these tables in recent rulemakings; however, the corresponding footnote numbering in the tables was not changed. In addition, this rule makes a minor correction to the Stage 1 Disinfectants and Disinfection Byproducts Rule by replacing a sentence that was inadvertently removed.

Abstract  The supply chain of a product is essential for understanding its environmental impacts. As parts of agricultural product supply chains, land use (LU) and land use change (LUC) are considered to be major contributors to global CO2 emissions. Nevertheless, LU and LUC (LULUC) are rarely included in GHG estimations for food and feedstuffs. Here we propose a method which can be used to derive emissions from LU and LUC on a regional level. Emissions are distributed over an accounting period chosen to match the physically occurring carbon fluxes. As fluxes from soil organic carbon persist for years or even for decades after a LUC episode, depending on the climatic conditions of the region, we apply 10 and 20 years as suitable accounting periods for tropical and temperate climate zones, respectively. We compare the proposed method with two other methods proposed in the literature. Using two types of feedstuffs (Brazilian soybean-meal and Austrian barley) as examples, we find that the other two methods produce mostly lower emission estimates in the case of Brazilian soybeans, and higher estimates for Austrian barley. We conclude that these differences are caused mainly by different accounting periods and by a (non)consideration of regional specificities. While analysing life cycles necessarily entails a well supported but still arbitrary setting of such system boundaries, we argue that the methodology presented here better reflects actually occurring carbon fluxes that we understand to be the foundation of any environmental product assessment. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  Linking hydrologic interactions with global carbon cycling will reduce the uncertainty associated with scaling-up empirical studies and facilitate the incorporation of terrestrial-aquatic linkages within global and regional change models. Much of the uncertainty in estimates of carbon fluxes associated with precipitation and hydrologic transport results from the extensive spatial and temporal heterogeneity in both intrinsic functioning and anthropogenic modification of hydrological cycles. To better understand this variation we developed a landscape ecological approach to coupled hydrologic-carbon cycling that merges local mechanisms with multiple-scale spatial heterogeneity. This spatially explicit framework is applied to examine variability in hydrologic influences on carbon cycling along a continental scale water availability gradient with an explicit consideration of human sources of variability. Hydrologic variation is an important component of the uncertainty in carbon cycling; accounting for this variation will improve understanding of current conditions and projections of future ecosystem responses to global change.

Abstract  Imidacloprid is one of the most widely used insecticides in the world. Its concentration in surface water exceeds the water quality norms in many parts of the Netherlands. Several studies have demonstrated harmful effects of this neonicotinoid to a wide range of non-target species. Therefore we expected that surface water pollution with imidacloprid would negatively impact aquatic ecosystems. Availability of extensive monitoring data on the abundance of aquatic macro-invertebrate species, and on imidacloprid concentrations in surface water in the Netherlands enabled us to test this hypothesis. Our regression analysis showed a significant negative relationship (P<0.001) between macro-invertebrate abundance and imidacloprid concentration for all species pooled. A significant negative relationship was also found for the orders Amphipoda, Basommatophora, Diptera, Ephemeroptera and Isopoda, and for several species separately. The order Odonata had a negative relationship very close to the significance threshold of 0.05 (P = 0.051). However, in accordance with previous research, a positive relationship was found for the order Actinedida. We used the monitoring field data to test whether the existing three water quality norms for imidacloprid in the Netherlands are protective in real conditions. Our data show that macrofauna abundance drops sharply between 13 and 67 ng l(-1). For aquatic ecosystem protection, two of the norms are not protective at all while the strictest norm of 13 ng l(-1) (MTR) seems somewhat protective. In addition to the existing experimental evidence on the negative effects of imidacloprid on invertebrate life, our study, based on data from large-scale field monitoring during multiple years, shows that serious concern about the far-reaching consequences of the abundant use of imidacloprid for aquatic ecosystems is justified.

Abstract  Soil C sequestration may mitigate increasing atmospheric carbon dioxide concentrations. This study was conducted to assess chemical and physical fractions of total organic C (TOC) and total N (TN) as affected by land use, N fertilizer source, and rotation. Particulate organic matter (POM) and non-hydrolyzable C (NHC) fractions were measured in Drummer (fine-silty, mixed, superactive, mesic Typic Endoaquoll) silty clay loam and Raub (fine-silty, mixed, superactive, mesic Aquic Argiudoll) silt loam soil series during two growing seasons. Agroecosystems evaluated were continuous corn (Zea mays L.) (CC) and corn grown in rotation with soybean [Glycine max. (L.) Merr.] (CS) both with urea-ammonium nitrate (UAN), CC with either spring or fall liquid swine manure (CCSM and CCFM, respectively), soybean in rotation with CSUAN (SC), and restored prairie grass (PG). In general, CCFM exhibited the largest soil C and N pools. In corn-soybean rotations, the TOC declined roughly 10% following SC but increased a comparable amount following CSUAN. The 2-yr corn-soybean rotation (SC and CSUAN) had a similar overall effect as CCUAN on TOC (ranging from 22 to 24 g C kg(-1) soil). When compared with CCUAN, PG soils were enriched in TOC, fine POM-C and NHC but not in N pools, reflecting soil C and N dynamics dominated by fine root turnover without fertilization and tillage. Comparison of soil C pools between treatments that differed in TOC revealed that newly sequestered C was preferentially allocated into POM supporting this fraction as an indicator of management effect on C sequestration.

Abstract  In recent years the challenge of reducing the reliance on petroleum and natural gas with the energy produced by agricultural crops has received a renewed interest. However, many scientists have expressed serious reservations about the real benefit of a widespread diffusion of crops grown for energy feedstocks. While a diversification of energy portfolio is strongly needed, one of the greatest scientific challenge for the near future is to identify land use options that minimize negative impact on food prices and greenhouse gases emissions. The objective of this article is to discuss the following topics: (i) competition for land: bioenergy versus food; (ii) bioenergy crops and nitrogen cycling; (iii) plant traits to be targeted for improving land and nitrogen use efficiency; and (iv) the debated role of legumes. Because fertile land, suitable for food production, is a dwindling resource, the production of feedstocks for biofuels should be enhanced by exploiting favourable plant characteristics in marginal land areas. We point out that a rethinking of the concept of marginal land is necessary: not only areas poorly suited to grain crops production owing to low soil fertility, but also land unsuited to produce food owing to food safety reasons. Yet, whether a land area is marginal or not should be evaluated not only from the economic standpoint, but also from the ecological and environmental points of view. Moreover, grain crops residues should be exploited for bioenergy production providing that well devised height of cuttings assure the maintenance of soil organic matter. The main message of this review is that bioenergy should be seen as a complementary product of food and feed production, to be attained by optimized land and nitrogen use. Emphasis is given to the contribution that dedicated perennial lignocellulosic crops might provide in sustainable bioenergy production.

Abstract  Climatologists now state with a high degree of certainty that global climate change is real, is advancing more rapidly than expected, and is caused by human activities, especially through fossil fuel combustion and deforestation. Environmental public health researchers, in assessing future projections for Earth's climate, have concluded that, on balance, adverse health outcomes will predominate under these changed conditions. The number of pathways through which climate change can affect the health of populations makes this environmental hazard one of the most perilous and intricate challenges that we face in this century. By contrast, the potential health co-benefits from departing from our current fossil fuel-based economy may offer some of the most beneficial health opportunities in over a century.

Abstract  A mass balance procedure was used to determine rates of nitrate depletion in the riparian zone and stream channel of a small New Zealand headwater stream. In all 12 surveys the majority of nitrate loss (56–100%) occurred in riparian organic soils, despite these soils occupying only 12% of the stream's border. This disproportionate role of the organic soils in depleting nitrate was due to two factors. Firstly, they were located at the base of hollows and consequently a disproportionately high percentage (37–81%) of the groundwater flowed through them in its passage to the stream. Secondly, they were anoxic and high in both denitrifying enzyme concentration and available carbon. Direct estimates ofin situ denitrification rate for organic soils near the upslope edge (338 mg N m−2 h−1) were much higher than average values estimated for the organic soils as a whole (0.3–2.1 mg N m−2 h−1) and suggested that areas of these soils were limited in their denitrification activity by the supply of nitrate. The capacity of these soils to regulate nitrate flux was therefore under-utilized. The majority of stream channel nitrate depletion was apparently due to plant uptake, with estimates of thein situ denitrification rate of stream sediments being less than 15% of the stream channel nitrate depletion rate estimated by mass balance. This study has shown that catchment hydrology can interact in a variety of ways with the biological processes responsible for nitrate depletion in riparian and stream ecosystems thereby having a strong influence on nitrate flux. This reinforces the view that those seeking to understand the functioning of these ecosystems need to consider hydrological phenomena.