Copper and zinc speciation in the solution of a soil-sludge mixture

Only a small fraction of the transition metals content in sludge-amended soils is soluble, and yet this fraction is a major contributor to the mobility and bioavailability of the metals. The chemical species of zinc (Zn) and copper (Cu) in the soluble fractions of soil-sludge mixtures were characterized with respect to their charge, molecular weight, and stoichiometry using ion exchange resin and gel chromatography procedures. The change in the metals' species with time after sludge application was followed for 100 d. Copper in the water extracts of the sludge-sand mixtures was found almost exclusively in low molecular weight (below 1000 Da) complexes. Higher molecular weight (around 2500 Da) dissolved organic carbon (DOC) was present in the extracts as well, but this DOC fraction exhibited little complexation. Copper was present in the extracts mainly as negatively charged species throughout the incubation period, and zinc tended to form zwitter ions. As incubation progressed, the relative content of positively charged Zn in solution increased. Complexation capacity of DOC in sludge water extract, extrapolated to infinite dilution, was 8.75 mM Ca g(-1) DOC. When the complexation capacity of the extract is near saturation, a mean Cu-DOC complex can be defined. It consists of 1.9 Cu atoms attached to DOC species containing 5.6 C atoms. Thus, the organic Cu complexes consist primarily of about two Cu ions attached to DOC species containing only five or six C atoms. Amino acids and small peptides or polycarboxylic acids, such as citric acid, thus may be important complexing agents of the metal.     

Local Environmental Investments and Sustainable Development: the evaluation of environmental projects in Scotland supported by the European Agriculture Guidance and Guarantee Fund

In the UK for the period 1994-99, a broad range of environmental projects were given financial support through the European Agriculture Guidance and Guarantee Fund under the Objective 1 and Objective 5b programmes. This paper is concerned with the ex-post evaluation of these projects set within a Sustainable Development framework. The aim was to identify project types or characteristics that offered the greatest return on investment. A classification of six broad project types was adopted. The evaluation revealed that there were significant differences between individual projects with respect to the type and scale, and temporal and social distribution of the benefits they delivered. In particular, as well as delivering environmental and economic benefits, many projects made a significant contribution to the development of human and social capital. The paper concludes that it is possible to improve the basis for future project selection in order to maximise the returns on environmental investments in the context of sustainable development.     

A Proactive Approach Can Make Site Remediation Less Expensive

Without any incentive to clean up a contaminated site, remediation is often delayed until the site owner is compelled to act by regulatory agencies. In such a context, the selected technology is typically the one that will reach the remediation goals as quickly as possible. Unfortunately, this criterion is often met by overly expensive technologies, resulting in high and sometimes unaffordable total remediation costs, leading to a remediation with a negative net benefit. This study examines the effects of time constraint and benefit value on the optimal remediation strategy for a diesel-contaminated site. This strategy is developed using the technico-economic model METEORS, which takes into account the technology’s effectiveness, the uncertainty of the level of contamination, and the possibility of reducing this uncertainty through either an additional characterization (before selecting and applying a technology) or the monitoring of the remediation technology (during its use). Results of simulations with both economic and temporal constraints support a proactive approach to site remediation.     

DEVELOPING COMPETITION FOR WATER IN THE URBANIZING AREAS OF COLORADO1

ABSTRACT: Rapid population growth in the metropolitan area of Denver, Colorado, is causing conflicts over water use. Two cities, Thomton and Westminster, have begun condemnation proceedings against three irrigation companies to secure agricultural water rights for municipal use. This is the first condemnation proceeding against irrigation water rights for municipal use. Should the suit succeed, over 30,000 acres of presently irrigated land will lose its water supply. There are about four hundred landowners in the area; two hundred of these are commercial farmers, including truck, dairy and specialty farms. Total agricultural production amounts to about $8 million per year. About 561 jobs related to agriculture will disappear along with about $4 million in not income. Only 6.4 percent of the farmland along the Front Range is irrigated. Continued urban growth will put pressure on the water supply of much of this land. The interested parties of the region should cooperate to lessen the impact of urban growth on agricultural lands and water by forming a metropolitan water district. Such a district could share costs of development of additional municipal water and develop systems where municipalities would recycle waste water back to the irrigated lands.     

Matrix based fertilizers reduce nitrogen and phosphorus leaching in three soils

We compared the efficacy of matrix based fertilizers (MBFs) formulated to reduce NO3-, NH4+, and total phosphorus (TP) leaching, with Osmocoate 14-14-14, a conventional commercial slow release fertilizer (SRF) and an unamended control in three different soil textures in a greenhouse column study. The MBFs covered a range of inorganic N and P in compounds that are relatively loosely bound (MBF 1) to more moderately bound (MBF 2) and more tightly bound compounds (MBF 3) mixed with Al(SO4)3H2O and/or Fe2(SO4)3 and with high ionic exchange compounds starch, chitosan and lignin. When N and P are released, the chemicals containing these nutrients in the MBF bind N and P to a Al(SO4)3H2O and/or Fe2(SO4)3 starch-chitosan-lignin matrix. One milligram (8000 spores) of Glomus intradices was added to all formulations to enhance nutrient uptake. In all three soil textures the SRF leachate contained a higher amount of NH4+, NO3- and TP than leachate from all other fertilizers. In all three soils there were no consistent differences in the amount of NH4+, NO3- and TP in the MBF leachates compared to the control leachate. Plants growing in soils receiving SRF had greater shoot, root and total biomass than all MBFs regardless of Al(SO4)3H2O or Fe2(SO4)3 additions. Arbuscular mycorrhizal infection in plant roots did not consistently differ among plants growing in soil receiving SRF, MBFs and control treatments. Although the MBFs resulted in less plant growth in this experiment they may be applied to soils growing plants in areas that are at high risk for nutrient leaching to surface waters.     

Economic simulation modeling of reprocessing alternatives for corn masa byproducts

Increasing production of corn masa for tortillas, chips, and related snack foods is resulting in large quantities of organic residuals requiring environmentally sound management. These byproduct streams appear suitable for use as livestock feed material, thus eliminating landfilling costs. Possibilities for developing livestock feed include direct shipping to livestock feeding facilities, blending prior to shipping, extrusion processing, pellet mill processing, and dehydration. To assess the viability of these options for reprocessing masa byproducts as livestock feed materials, an economic model was developed and applied to each of these alternatives. Through a series of simulation runs with this model, it was determined that direct shipping was by far the most inexpensive means of recycling masa processing residuals (10–57 $/Mg). Other alternatives examined in increasing order of costs included blending prior to shipping, extrusion, pellet mill processing (3–15, 5–18, and 4–18 times greater than direct shipping, respectively), while dehydration was clearly cost-prohibitive (33–81 times greater). Bagged feed was slightly more expensive to produce than bulk feed (1.1 times greater), and reprocessing costs increased as delivery distance increased, due to increased labor, equipment, and fuel costs, but decreased as byproduct generation rate increased, due to the development of the economies of scale. Alternately, based on a tipping fee of 50 $/Mg, the total estimated cost to landfill ranged from 65 to 112 $/Mg. Based on this cost analysis, direct shipping and feeding to livestock is the recycling option of choice for masa processing byproducts. Although specific details of process configurations and associated costs will vary, similar results are likely for other high moisture food processing residuals destined for utilization as livestock feed or components thereof.