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Ecohydrological interfaces comprise liquid–solid interfaces such as the stream–sediment interface, gas–solid interfaces such as the soil–atmosphere interface, liquid–liquid interfaces such as a thermocline in a lake, or gas–liquid interfaces such as the lake–atmosphere interface. The interface at which heat as a tracer is mostly applied is the sediment–water interface at streams, lakes, and seas. It is important to note the underlying difference between heat transport and solute transport in porous media. Temperature differences can be used to identify patterns of groundwater exfiltration over large areas. Thermal infrared imaging reveals the temperature distribution of surfaces and allows the determination of the skin temperature of water bodies but not temperatures in a water body itself. Similar to streambed temperature mapping, the thermal patterns observed along the cable can provide a qualitative indicator of groundwater discharge.

We present the first nitrogen footprint model for a developing country: Tanzania. Nitrogen (N) is a crucial element for agriculture and human nutrition, but in excess it can cause serious environmental damage. The Sub-Saharan African nation of Tanzania faces a two-sided nitrogen problem: while there is not enough soil nitrogen to produce adequate food, excess nitrogen that escapes into the environment causes a cascade of ecological and human health problems. To identify, quantify, and contribute to solving these problems, this paper presents a nitrogen footprint tool for Tanzania. This nitrogen footprint tool is a concept originally designed for the United States of America (USA) and other developed countries. It uses personal resource consumption data to calculate a per-capita nitrogen footprint. The Tanzania N footprint tool is a version adapted to reflect the low-input, integrated agricultural system of Tanzania. This is reflected by calculating two sets of virtual N factors to describe N losses during food production: one for fertilized farms and one for unfertilized farms. Soil mining factors are also calculated for the first time to address the amount of N removed from the soil to produce food. The average per-capita nitrogen footprint of Tanzania is 10 kg N yr−1. 88% of this footprint is due to food consumption and production, while only 12% of the footprint is due to energy use. Although 91% of farms in Tanzania are unfertilized, the large contribution of fertilized farms to N losses causes unfertilized farms to make up just 83% of the food production N footprint. In a developing country like Tanzania, the main audiences for the N footprint tool are community leaders, planners, and developers who can impact decision-making and use the calculator to plan positive changes for nitrogen sustainability in the developing world.

The United States’ legal strategy for addressing climate change in recent years has relied on authority from existing legislation. This has led to measures on a number of different greenhouse gases, notably carbon dioxide, methane and hydrofluorocarbons. However, one greenhouse gas has been largely forgotten: nitrous oxide. Nitrous oxide is the third most abundantly emitted greenhouse gas in the U.S. and worldwide, as well as the largest remaining threat to the stratospheric ozone layer. In addition, the nitrogen atoms in nitrous oxide are part of the highly fluid nitrogen cycle where nitrogen atoms transform readily among different chemical forms, each with a unique environmental and human health impact – a process known as the nitrogen cascade. While the science of the nitrogen cascade has been explored for over a decade, there has been little work on the legal implications of this phenomenon. And yet the nitrogen cascade expands the legal options available for controlling nitrous oxide. This paper studies these options in a U.S. context and explores the environmental and economic impacts of enacting them. We determine that the Clean Air Act, and in particular its broad authority for controlling ozone depleting substances, is the most promising legal pathway for regulating nitrous oxide across all major sources. Invoking such authority could generate significant climate and stratospheric ozone benefits over 2015–2030, equivalent to taking 12 million cars permanently off the road, and 100 million chlorofluorocarbon-laden refrigerators out of service. The economic benefits could sum to over $700 billion over 2015–2030, with every $1.00 spent on abating emissions leading to $4.10 in societal benefits. The bulk of these benefits would come from reductions in other forms of nitrogen pollution such as ammonia and nitrate, highlighting the important and multiple co-benefits that could be achieved by abating nitrous oxide emissions. With the Paris Climate Agreement callin

The global nitrogen (N) cycle at the beginning of the 21st century has been shown to be strongly influenced by the inputs of reactive nitrogen (Nr) from human activities, including combustion-related NOx, industrial and agricultural N fixation, estimated to be 220 Tg N yr−1 in 2010, which is approximately equal to the sum of biological N fixation in unmanaged terrestrial and marine ecosystems. According to current projections, changes in climate and land use during the 21st century will increase both biological and anthropogenic fixation, bringing the total to approximately 600 Tg N yr−1 by around 2100. The fraction contributed directly by human activities is unlikely to increase substantially if increases in nitrogen use efficiency in agriculture are achieved and control measures on combustion-related emissions implemented. Some N-cycling processes emerge as particularly sensitive to climate change. One of the largest responses to climate in the processing of Nr is the emission to the atmosphere of NH3, which is estimated to increase from 65 Tg N yr−1 in 2008 to 93 Tg N yr−1 in 2100 assuming a change in global surface temperature of 5 °C in the absence of increased anthropogenic activity. With changes in emissions in response to increased demand for animal products the combined effect would be to increase NH3 emissions to 135 Tg N yr−1. Another major change is the effect of climate changes on aerosol composition and specifically the increased sublimation of NH4NO3 close to the ground to form HNO3 and NH3 in a warmer climate, which deposit more rapidly to terrestrial surfaces than aerosols. Inorganic aerosols over the polluted regions especially in Europe and North America were dominated by (NH4)2SO4 in the 1970s to 1980s, and large reductions in emissions of SO2 have removed most of the SO42− from the atmosphere in these regions. Inorganic aerosols from anthropogenic emissions are now dominated by NH4NO3, a volatile aerosol which contributes substantially to PM10 a

It is now clear that the nitrogen problem is one of the most pressing environmental issues that we face. But in spite of the enormity of our influence on the N cycle and consequent implications for the environment and for human well-being, there is surprisingly little attention paid to the issue. While biodiversity loss and climate change have spawned huge budgets to create national and multidisciplinary programs, global organizations, political and media attention, the N challenge remains much less apparent in our thinking and actions. This is because we are educated with the important role that N plays with regard to food security. This paper aims to contribute to the understanding of the N challenge, and to provide options for decreasing the negative impacts of excess N.

The United States (US) is among the global hotspots of nitrogen (N) deposition and assessing the temporal trends of wet N deposition is relevant to quantify the effectiveness of existing N regulation policies and its consequent environmental effects. This study analyzed changes in observed wet deposition of dissolved inorganic N (DIN = ammonium + nitrate) in the US between 1985 and 2012 by applying a Mann–Kendall test and Regional Kendall test. Current wet DIN deposition (2011–2012) data were used to gain insight in the current pattern of N deposition. Wet DIN deposition generally decreased going from Midwest > Northeast > South > West region with a national mean rate of 3.5 kg N ha-1 yr-1. Ammonium dominated wet DIN deposition in the Midwest, South and West regions, whereas nitrate and ammonium both contributed a half in the Northeast region. Wet DIN deposition showed no significant change at the national scale between 1985 and 2012, but profound changes occurred in its components. Wet ammonium deposition showed a significant increasing trend at national scale (0.013 kg N ha-1 yr-2), with the highest increase in the Midwest and eastern part of the South region. Inversely, wet nitrate deposition decreased significantly at national scale (-0.014 kg N ha-1 yr-2), with the largest reduction in the Northeast region. Overall, ratios of ammonium versus nitrate in wet deposition showed a significant increase in all the four regions, resulting in a transition of the dominant N species from nitrate to ammonium. Distinct magnitudes, trends and patterns of wet ammonium and nitrate deposition suggest the needs to control N emissions by species and regions to avoid negative effects of N deposition on ecosystem health and function in the US.

In this paper we use nitrogen (N) footprints as indicators of potential environmental impacts of food production in Austria. These footprints trace the losses of reactive nitrogen (Nr), i.e. N compounds that are generally accessible to biota, in connection to the chain of food production and consumption. While necessary for food production, Nr is known for its negative environmental impacts. The N footprints presented here describe Nr losses but do not link to effects directly. In deriving N footprints, Nr lost along the production chain needs to be quantified, expressed as "virtual nitrogen factors" (VNF). We calculated specific VNF for Austrian production conditions for a set of eight broad food categories (poultry, pork, beef, milk, vegetables & fruit, potatoes, legumes, cereals). The life-cycle oriented nitrogen footprints for the respective food groups were replenished by assessing Nr losses related to energy needs and to food consumption. The results demonstrate that in general, animal based products are less nitrogen-efficient than plant based products. For meat, footprints range from 64 g N per kg (pork) to 134 g N per kg (beef). For vegetable products, footprints are between 5 g N per kg (potatoes) and 22 g N per kg (legumes). The detailed ranking of food products is different when relating nitrogen footprints to either simple mass of food, or protein content. Vegetables & fruit cause only 9 g N per kg, but 740 g N per kg protein, which is even higher than pork (616 g N per kg protein) or poultry (449 g N per kg protein). These differences clearly show that taking into account protein and other aspects of food quality may be crucial for a proper assessment of dietary choices. The total N footprint per Austrian inhabitant is dominated by food production and consumption (85%) but also includes other activities linked to fixing nitrogen from the atmosphere (notably combustion). The average N footprint is 19.8 kg N per year per Austrian inhabitant, which is on

The human alteration of the nitrogen cycle has evolved from minimal in the mid-19th century to extensive in the present time. The consequences to human and environmental health are significant. While much attention has been given to the extent and impacts of the alteration, little attention has been given to those entities (i.e., consumers, institutions) that use the resources that result in extensive reactive nitrogen (Nr) creation. One strategy for assessment is the use of nitrogen footprint tools. A nitrogen footprint is generally defined as the total amount of Nr released to the environment as a result of an entity's consumption patterns. This paper reviews a number of nitrogen footprint tools (N-Calculator, N-Institution, N-Label, N-Neutrality, N-Indicator) that are designed to provide that attention. It reviews N-footprint tools for consumers as a function of the country that they live in (N-Calculator, N-Indicator) and the products they buy (N-Label), for the institutions that people work in and are educated in (N-Institution), and for events and decision-making regarding offsets (N-Neutrality). N footprint tools provide a framework for people to make decisions about their resource use and show them how offsets can be coupled with behavior change to decrease consumer/institution contributions to N-related problems.

Human activities affect the impact of the nitrogen cycle on both the environment and climate. The rate of anthropogenic nitrogen fixation from atmospheric N2 may serve as an indicator to the magnitude of this impact, acknowledging that relationship to be effect-dependent and non-linear. Building on the set of Representative Concentration Pathway (RCP) scenarios developed for climate change research, we estimate anthropogenic industrial nitrogen fixation throughout the 21st century. Assigning characteristic key drivers to the four underlying scenarios we arrive at nitrogen fixation rates for agricultural use of 80 to 172 Tg N/yr by 2100, which is slightly less to almost twice as much compared with the fixation rate for the year 2000. We use the following key drivers of change, varying between scenarios: population growth, consumption of animal protein, agricultural efficiency improvement and additional biofuel production. Further anthropogenic nitrogen fixation for production of materials such as explosives or plastics and from combustion are projected to remain considerably smaller than that related to agriculture. While variation among the four scenarios is considerable, our interpretation of scenarios constrains the option space: several of the factors enhancing the anthropogenic impact on the nitrogen cycle may occur concurrently, but never all of them. A scenario that is specifically targeted towards limiting greenhouse gas emissions ends up as the potentially largest contributor to nitrogen fixation, as a result of large amounts of biofuels required and the fertilizer used to produce it. Other published data on nitrogen fixation towards 2100 indicate that our high estimates based on the RCP approach are rather conservative. Even the most optimistic scenario estimates that nitrogen fixation rate will remain substantially in excess of an estimate of sustainable boundaries by 2100.

Although over 78% of the atmosphere is composed of nitrogen, it exists in its chemically and biologically unusable gaseous form. Haber discovered how ammonia, a chemically reactive, highly usable form of nitrogen, could be synthesized by reacting atmospheric dinitrogen with hydrogen in the presence of iron at high pressures and temperatures.

The N fertilizer accessibility and use situations have arisen primarily from a suite of national and international policies in agriculture and environmental sectors. There is currently closer interaction among these sectors in Europe and to some extent in the US that strive to balance food production and pollution concerns. When we look to the future, can countries that are beginning to intensify their agricultural production learn from the experiences of others? Are there measures that can be taken to stave off serious environmental problems before they occur? Where environmental problems do exist, how can future policies be crafted to solve these problems while ensuring food security and boosting economies? Effective policies that focus on food security and rural development must ensure sufficient infrastructure that provide access to fertilizers and other inputs and to deliver products to the national and international markets. Provision of financial assistance and knowledge through education, research and extension are also critical. Effective uptake of improved agricultural production will also probably initially require some type of subsidy for fertilizers or crop price supports. Such infrastructure and services requires an active involvement of the government. Developing countries should not refrain from supporting fertilizer use because of fear of environmental pollution. There is currently a higher risk of degrading the agricultural production potential of the land through soil degradation due to insufficient fertilizer use. Nevertheless, there needs to be an awareness of the potential environmental effects so that regulations can be put in place at the appropriate time. Such environmental concerns should now be addressed in many parts of Asia but are probably a couple of decades away in much of SSA. In areas where environmental problems due to excessive N use exist, future policies must be carefully constructed to ensure that past environmental gains are p

Interstitial water samples and sediments were collected from Woods Lake to evaluate Pb profile stability and distribution between the solid and aqueous phases. The pH of the lake at the time was 5.0. A simple equation was developed to describe the distribution coefficient for Pb, based on the sample moisture content and analyte concentrations in bulk sediment and pore water. In Woods Lake, the lead distribution coefficient values ranged from 67 000 to 670 000 ml/g. The affinity of Pb for the solid phase was further demonstrated by inverting a sediment core and leaving it for ten months in situ. The Pb profile was found to have remained intact over the same depth, albeit inverted, as in the surrounding sediment. Geochemical modelling demonstrates that Pb solids, that may reasonably be expected to precipitate, were all undersaturated by several orders of magnitude with respect to the interstitial water. This indicates that Pb was sorbed to, rather than precipitated in, the Woods Lake sediment., Interstitial water samples and sediments were collected from Woods Lake to evaluate Pb profile stability and distribution between the solid and aqueous phases. The pH of the lake at the time was 5.0. A simple equation was developed to describe the distribution coefficient for Pb, based on the sample moisture content and analyte concentrations in bulk sediment and pore water. In Woods Lake, the lead distribution coefficient values ranged from 67 000 to 670 000 ml/g. The affinity of Pb for the solid phase was further demonstrated by inverting a sediment core and leaving it for ten months in situ. The Pb profile was found to have remained intact over the same depth, albeit inverted, as in the surrounding sediment. Geochemical modelling demonstrates that Pb solids, that may reasonably be expected to precipitate, were all undersaturated by several orders of magnitude with respect to the interstitial water. This indicates that Pb was sorbed to, rather than precipitated in, the Woods Lake sediment.