DNRA: A short-circuit in biological N-cycling to conserve nitrogen in terrestrial ecosystems

Mechanism and optimization of electrochemical system for simultaneous removal of nitrate and ammonia

Groundwater is the essential and predominant source of drinking and irrigation water supplies in most arid and semiarid regions, particularly in Loess Plateau of China. The threat to groundwater quality by nitrate pollution has always been of considerable concern in loess regions. In this paper, correspondence analysis, stoichiometric analysis, ratios of major ions and some qualitative analysis are employed to discuss the spatial variability of nitrate (NO3
 −), identification of NO3
 − pollution sources and its potential pollution paths based on 112 water samples in Tongchuan region on the middle edge of Loess Plateau of China. Results indicate that the NO3
 − concentrations ranged from 0.25 to 173 mg/L, 20.54% of water samples exceeded the Standards for Drinking Water Quality from China (≤44 mg/L), and 15.18% of samples exceeded the Guidelines for Drinking Water Quality from World Health Organization (≤50 mg/L); the water samples with high NO3
 − concentrations primarily concentrated in river valleys, and the types were mainly pore waters and individual surface waters. Sewage or manure from livestock effluent was the primary sources of NO3
 − in some surface waters, pore water samples with high NO3
 − were closely related to agricultural input or a mixing process. Groundwater recharges from surface water and vertical infiltration in river valleys with shallow groundwater depth were considered as the potential pollution paths for NO3
 − ions in the study area based on nitrate nitrogen distribution in soil profile. Driven by concentration difference and local seepage system, these NO3
 − ions diffused around and groundwater buried in great depth was consequently polluted. Therefore, river valleys should be listed as the prior protection areas in loess regions; in addition, the time lag between land use changes and groundwater quality response should also be paid attention to in nitrate pollution prevention, particularly in the thick unsaturated zones.

Identification of nitrate pollution sources of groundwater and analysis of potential pollution paths in loess regions: a case study in Tongchuan region, China

Effect of thermal intensity and initial moisture content on heat and moisture transfer in unsaturated soil

NH4+-N/NO3--N ratio controlling nitrogen transformation accompanied with NO2--N accumulation in the oxic-anoxic transition zone.

Understanding the hydrologic control of N cycle: Effect of water filled pore space on heterotrophic nitrification, denitrification and dissimilatory nitrate reduction to ammonium mechanisms in unsaturated soils.

Experimental and Simulation Studies on Nitrogen Dynamics in Unsaturated and Saturated Soil Using HYDRUS-2D

The vertical transport of nitrates from fertilizer application and wastewater irrigation through the subsurface and saturated zone is of major concern to assess the vulnerability of groundwater contamination. The present study addresses the transport of nitrogenous fertilizers such as ammonium and nitrate in the presence of organic carbon (acetate) in a one-dimensional soil column under saturated conditions, considering the effect of adsorption and biotransformation. The soil had a neutral pH range and was classified as loamy sand, with a 0.89% organic carbon content. Batch studies revealed that sorption occurred in the order of ammonium > acetate > nitrate following a Freundlich isotherm model. Mixed heterotrophic native soil bacteria for aerobic nitrification and anoxic denitrification were developed, and the growth kinetic parameters were simulated using a Haldane inhibition model for nitrification and a Monod inhibition model for denitrification. Results from biotransformation studies suggeste...

C. Mekala

Papers

Understanding the hydrologic control of N cycle: Effect of water filled pore space on heterotrophic nitrification, denitrification and dissimilatory nitrate reduction to ammonium mechanisms in unsaturated soils.

Experimental and Simulation Studies on Nitrogen Dynamics in Unsaturated and Saturated Soil Using HYDRUS-2D

Transport of ammonium and nitrate in saturated porous media incorporating physiobiotransformations and bioclogging

Understanding nitrogen and carbon biogeotransformations and transport dynamics in saturated soil columns