Konstantinos C. Makris

Controlling the fate of roxarsone and inorganic arsenic in poultry litter

A growing body of literature reports 3-nitro-4-hydroxyphenylarsonic acid (roxarsone) degradation in poultry litter (PL) to the more toxic inorganic arsenic (As). Aluminum-based drinking-water treatment residuals (WTR) present a low-cost amendment technology to reduce As availability in PL, similar to the use of alum to reduce phosphorus availability. Batch experiments investigated the effectiveness of WTR in removing roxarsone and inorganic As species from PL aqueous suspensions. Incubation experiments with WTR-amended PL evaluated the effects of WTR application rates (2.5-15% by weight) and incubation time (up to 32 d) at two incubation temperatures (23 and 35 degrees C) on As availability in PL. Batch PL aqueous experiments showed the high affinity of As(V), As(III), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), and roxarsone for the WTR. The 10% WTR amendment rate decreased As availability in PL by half of that of the unamended (no WTR) PL-incubated samples. The reduction in dissolved As concentrations during incubation of WTR-amended PL samples was kinetically limited, being complete within 13 d. Parallel reductions in roxarsone, As(V), and DMA concentrations were observed with liquid chromatography-inductively coupled plasma mass spectrometry, whereas As(III) and MMA concentrations were always <5% of dissolved As. Incubation temperature did not significantly (p > 0.05) influence dissolved As concentrations in the WTR-amended PL. Potential formation of a copper-containing roxarsone metabolite was considered in PL aqueous suspensions with the aid of electrospray mass spectrometry. Further experiments in the field are necessary to ensure that sorbed As is stable in WTR-amended PL.

Chaotropic effects on 2,4,6-trinitrotoluene uptake by wheat (Triticum aestivum)

Previous research in our laboratory investigated the effectiveness of a common agrochemical, urea used as a chaotropic agent to facilitate 2,4,6-trinitrotoluene (TNT) removal by vetiver grass (Vetiveria zizanioides L.). Chaotropic agents disrupt water structure, increasing solubilization of hydrophobic compounds (TNT), and enhancing plant TNT uptake. Our findings showed that urea significantly enhanced TNT uptake kinetics by vetiver. We hypothesized that the beneficial effect of urea on the overall TNT uptake by vetiver grass was not plant-specific. We explored this hypothesis by testing the ability of wheat (Triticum aestivum L.) in removing TNT from aqueous media in the presence of urea. Results showed that untreated (no urea) wheat exhibited a slow, kinetically limited TNT uptake that was nearly half of the urea-treated wheat TNT capacity (250xa0mgxa0kg−1). Chaotropic effects of urea were illustrated by the significant (Pxa0<xa00.001) increase in the TNT second-order reaction rate constants over those of the untreated (no urea) controls. Plant TNT speciation showed that TNT and several of its metabolites were detected in both root and shoot compartments of the plant, allowing for 110 and 36% recovery for the untreated and 0.1% urea treated plants. The lower % recovery of the urea-treated plants was attributed to a number of unknown polar TNT metabolites.

Chapter 34 Current trends and future directions in environmental geochemistry research

Abstract Increasing population growth and rapid industrialization with passing time have augmented the rate of deterioration of the environment, which is having a clear negative impact on human and ecological health. Although considerable research is now being undertaken in critical areas such as global change, environmental quality, and ecological protection, more collaborative, inter-disciplinary research is needed in order to ensure long-term environmental sustainability. A thorough understanding of the geochemistry of the earths intrinsic processes is needed to develop a comprehensive, holistic model for the protection of the environment to ensure long-term sustainability in a global scale. This chapter briefly discusses some of the more salient current trends in environmental geochemistry research and a few of the many potential future directions of research in this area, often in close collaboration with experts in other scientific disciplines and policy makers geared towards maintaining earth system sustainability.