Nutrient flux in storm water runoff and baseflow from managed turf

The urban landscape is comprised of many land uses, none more intensively managed than turfgrass; however, quantification of nutrient losses from specific land uses within urban watersheds, specifically golf courses is limited. Nitrate (NO(3)-N) and dissolved reactive phosphorus (DRP) were measured on a golf course in Austin, TX, USA from April 1, 1998 to March 31, 2003. NO(3)-N and DRP concentrations measured in storm flow were significantly greater exiting the course compared to those entering the course. Significant differences were also measured in baseflow NO(3)-N concentrations. The measured loading from the course was 4.0kg NO(3)-Nha(-1)yr(-1) (11% of applied) and 0.66kg DRPha(-1)yr(-1) (8% of applied). The resulting concentrations contributed by the course were 1.2mgL(-1) NO(3)-N and 0.2mgL(-1) DRP. At these levels, NO(3)-N poses minimal environmental risk. However, the DRP concentration is twice the recommended level to guard against eutrophication.     

Growth and biochemical parameters of Cicer arietinum L. grown on amended fly ash

Growth and metal accumulation were investigated in two Cicer arietinum L. varieties (var. CSG-8962 and var. C-235) when grown in various combinations of fly ash (FA) amended with garden soil (GS), press mud (PM) or saw dust (SD). In addition, the levels of photosynthetic pigments, nitrate reductase (NR) activity, cysteine, non-protein thiols (NP-SH), and ascorbic acid were studied. FA amended with GS or PM led to a 5–10 times increase in biomass compared to FA control and was most pronounced in the less metal tolerant variety CSG-8962. Amendment of FA with either GS or PM only moderately increased the contents of some essential metals whereas the non-essential Cd and Cr remained similar or decreased slightly compared to FA control. FA combined with either GS or PM increased the amount of photosynthetic pigments and was largely absent when SD was added to FA. Improved nitrogen availability led to increased nitrate reductase (NR) activity with all amendments but less so with SD. Metal stress indicating parameters were generally reduced (cysteine and non-protein thiols) or unchanged (ascorbic acid). In conclusion, of the tested ameliorants both GS and PM greatly improved growth of C. arietinum making FA a suitable component of plant growth substrates.     

Nitrate reduction by green rusts modified with trace metals

A kinetic study of nitrate reduction by green rust (GR), a group of layered Fe(II)-Fe(III) hydroxide solids, was performed using a batch reactor system. The reduction rate of nitrate by GRs was affected by the anion content in the interlayer of GRs. GR containing F^- (GR-F) showed the fastest reduction rate while GR-SO₄ showed 9 times slower reaction rate than GR-F. The addition of 1 mM Pt or Cu to GR that contained 85 mM Fe(II) improved the reduction kinetics of nitrate by up to 200 times. Pt was an effective activating agent for all GRs. The sequential step reaction model that we proposed appropriately simulated the experimental data. The fastest nitrate reduction by GR-F with Pt was achieved at pH 9 among 7.5 to 11. At that condition, 1 mM nitrate transformed completely into ammonium within 23 min.     

Electrochemical removal of nitrate using ZVI packed bed bipolar electrolytic cell

The present study investigates the performance of the zero valent iron (ZVI, Fe⁰) packed bed bipolar electrolytic cell for nitrate removal. The packing mixture consists of ZVI as electronically conducting material and silica sand as non-conducting material between main cathode and anode electrodes. In the continuous column experiments for the simulated groundwater (initial nitrate and electrical conductivity of about 30 mg L⁻¹ as N and 300 μS cm⁻¹, respectively), above 99% of nitrate was removed at the applied potential of 600 V with the main anode placed on the bottom of reactor. The influx nitrate was converted to ammonia (20% to maximum 60%) and nitrite (always less than 0.5 mg L⁻¹ as N in the effluent). The optimum packing ratio (v/v) of silica sand to ZVI was found to be 1:1-2:1. Magnetite was observed on the surface of the used ZVI as corrosion product. The reduction at the lower part of the reactor in acidic condition and adsorption at the upper part of the reactor in alkaline condition are the major mechanism of nitrate removal.     

Forensic Applications of Nitrogen and Oxygen Isotopes in Tracing Nitrate Sources in Urban Environments

Ground and surface waters in urban areas are susceptible to nitrate contamination from septic systems, leaking sewer lines, and fertilizer applications. Source identification is a primary step toward a successful remediation plan in affected areas. In this respect, nitrogen and oxygen isotope ratios of nitrate, in conjunction with hydrologic data and water chemistry, have proven valuable in urban studies from Austin, Texas, and Tacoma, Washington. In Austin, stream water was sampled during stremflow and baseflow conditions to assess surface and subsurface sources of nitrate, respectively. In Tacoma, well waters were sampled in adjacent sewered and un-sewered areas to determine if locally high nitrate concentrations were caused by septic systems in the un-sewered areas. In both studies, sewage was identified as a nitrate source and mixing between sewage and other sources of nitrate was apparent. In addition to source identification, combined nitrogen and oxygen isotopes were important in determining the significance of denitrification, which can complicate source assessment by reducing nitrate concentrations and increasing i 15 N values. The two studies illustrate the value of nitrogen and oxygen isotopes of nitrate for forensic applications in urba areas.     

Electrocatalytic reduction of nitrate using Pd-Cu modified carbon nanotube membranes

● Pd-Cu modified CNT membranes were prepared successfully by electrodeposition method. ● The deposition voltage and deposition time were optimized for Pd-Cu co-deposition. ● NO₃⁻-N was removed efficiently from water by Pd-Cu modified CNT membranes. ● The presence of dissolved oxygen did not affect the nitrate reduction performance. ● Mass transfer rate was promoted significantly with the increase in membrane flux. Excessive nitrate in water is harmful to the ecological environment and human health. Electrocatalytic reduction is a promising technology for nitrate removal. Herein, a Pd-Cu modified carbon nanotube membrane was fabricated with an electrodeposition method and used to reduce nitrate in a flow-through electrochemical reactor. The optimal potential and duration for codeposition of Pd and Cu were −0.7 V and 5 min, respectively, according to linear scan voltammetry results. The membrane obtained with a Pd:Cu ratio of 1:1 exhibited a relatively high nitrate removal efficiency and N₂ selectivity. Nitrate was almost completely reduced (~99 %) by the membrane at potentials lower than −1.2 V. However, −0.8 V was the optimal potential for nitrate reduction in terms of both nitrate removal efficiency and product selectivity. The nitrate removal efficiency was 56.2 %, and the N₂ selectivity was 23.8 % for the Pd:Cu=1:1 membrane operated at −0.8 V. Nitrate removal was enhanced under acidic conditions, while N₂ selectivity was decreased. The concentrations of Cl⁻ ions and dissolved oxygen showed little effect on nitrate reduction. The mass transfer rate constant was greatly improved by 6.6 times from 1.14 × 10⁻³ m/h at a membrane flux of 1 L/(m²·h) to 8.71 × 10⁻³ m/h at a membrane flux of 15 L/(m²·h), which resulted in a significant increase in the nitrate removal rate from 13.6 to 133.5 mg/(m²·h). These findings show that the Pd-Cu modified CNT membrane is an efficient material for nitrate reduction.     

水处理用活性炭改性研究

研究了锆（Zr）和十六烷基三甲基氯化铵（CTAC）联合改性活性炭的制备,并考察Zr-CTAC改性活性炭对水中硝酸盐和磷酸盐的吸附作用及相关吸附机制,着重论述了锆（Zr）和十六烷基三甲基氯化铵联合改性活性炭（Zr-CTAC-AC）对水中硝酸盐和磷酸盐的吸附去除作用,结果表明Zr-CTAC-AC对水中硝酸盐和磷酸盐均具备较好的吸附去除能力。     

Two-stage Sequential Electrochemical Treatment of Nitrate Brine Wastes

Nitrates in concentrated brines can be electrochemically reduced in the cathodic chamber of a split-cell electrochemical reactor with formation of ammonium (and small amounts of nitrite). Fortunately, ammonium may be electrochemically oxidized to nitrogen gas in the anodic reaction chamber if a coupled sequential process is used. The presence of chloride in the brine waste is an important consideration in oxidative electrochemical processes, however, because it cycles through oxidized and reduced states at the electrode surfaces and in the bulk solution. Electrochemical oxidation converts chloride ions to “active chlorine” species with additional oxidizing capability (chlorine, hypochlorous acid and hypochlorite – essentially bleach), as well as to chlorates, depending on the reaction conditions. The production of these active species improves treatment performance in the ammonium oxidation phase since oxidation is no longer limited to the electrode surface. However, the process must be engineered to minimize loss of process efficiency due to parasitic side reactions (chloramines and chlorate). In this study, two-stage batch electrolysis was conducted using a three-electrode (copper anode, platinum-coated titanium cathode, silver/silver chloride reference) electrochemical cell, with the anodic and cathodic chambers separated by a Nafion 117 membrane. Treatment of nitrate and ammonium was tested with and without the presence of chloride in the waste. No significant difference was observed in cathodic nitrate reduction with chloride present or absent. However, the presence of chloride in the solution favored overall soluble nitrogen elimination upon oxidation. Increasing applied current increased production of undesirable byproducts (especially chlorate).     

Informing common pool resource problems: a survey of preference for catchment management strategies amongst farmers and the general public in the Ythan river catchment

In principle the protection of environmental resources is in every ones interest, yet it is evident that this is not what often occurs. In some cases there is an identifiable person or corporation, whose environmental impact can be tractably regulated either politically or via market forces. In other cases there is cumulative impact on a commonly held or "common pool" resource, from a variety of users, making establishing rights and responsibilities for resource management more difficult. The water of the Ythan catchment is one such 'Common Pool Resource' (CPR). An intensively farmed catchment also sustaining a sizable population, the consequent nitrate inputs to the water are believed to be the cause of algal matting at the estuary mouth, an internationally designated wildlife reserve. This led to its designation as Scotland's first Nitrate Vulnerable Zone (NVZ). Supported by the EU Life Environment fund, the Ythan Project attempted to foster co-operation between farmers and the wider community of the Ythan catchment to protect and restore the river environment. Throughout the project surveys were undertaken concerning the popularity of the Ythan Project's voluntary approach compared with more individualist or state-organised approaches. Taking CPR theory as a framework, key findings from those surveys are presented and discussed as to their implications for organisational intervention in CPR problems.     

Testing the Hydrological Landscape Unit Classification System and Other Terrain Analysis Measures for Predicting Low-Flow Nitrate and Chloride in Watersheds

Elevated nitrate concentrations in streamwater are a major environmental management problem. While land use exerts a large control on stream nitrate, hydrology often plays an equally important role. To date, predictions of low-flow nitrate in ungauged watersheds have been poor because of the difficulty in describing the uniqueness of watershed hydrology over large areas. Clearly, hydrologic response varies depending on the states and stocks of water, flow pathways, and residence times. How to capture the dominant hydrological controls that combine with land use to define streamwater nitrate concentration is a major research challenge. This paper tests the new Hydrologic Landscape Regions (HLRs) watershed classification scheme of Wolock and others (Environmental Management 34:S71-S88, 2004) to address the question: Can HLRs be used as a way to predict low-flow nitrate? We also test a number of other indexes including inverse-distance weighting of land use and the well-known topographic index (TI) to address the question: How do other terrain and land use measures compare to HLR in terms of their ability to predict low-flow nitrate concentration? We test this for 76 watersheds in western Oregon using the U.S. Environmental Protection Agency’s Environmental Monitoring and Assessment Program and Regional Environmental Monitoring and Assessment Program data. We found that HLRs did not significantly improve nitrate predictions beyond the standard TI and land-use metrics. Using TI and inverse-distance weighting did not improve nitrate predictions; the best models were the percentage land use—elevation models. We did, however, see an improvement of chloride predictions using HLRs, TI, and inverse-distance weighting; adding HLRs and TI significantly improved model predictions and the best models used inverse-distance weighting and elevation. One interesting result of this study is elevation consistently predicted nitrate better than TI or the hydrologic classification scheme.