Managing agricultural emissions to the atmosphere: state of the science, fate and mitigation, and identifying research gaps.

The impact of agriculture on regional air quality creates significant challenges to sustainability of food supplies and to the quality of national resources. Agricultural emissions to the atmosphere can lead to many nuisances, such as smog, haze, or offensive odors. They can also create more serious effects on human or environmental health, such as those posed by pesticides and other toxic industrial pollutants. It is recognized that deterioration of the atmosphere is undesirable, but the short- and long-term impacts of specific agricultural activities on air quality are not well known or understood. These concerns led to the organization of the 2009 American Chemical Society Symposium titled . An outcome of this symposium is this special collection of 14 research papers focusing on various issues associated with production agriculture and its effect on air quality. Topics included emissions from animal feeding operations, odors, volatile organic compounds, pesticides, mitigation, modeling, and risk assessment. These papers provide new research insights, identify gaps in current knowledge, and recommend important future research directions. As the scientific community gains a better understanding of the relationships between anthropogenic activities and their effects on environmental systems, technological advances should enable a reduction in adverse consequences on the environment.

Thermodynamic, spectroscopic, and computational evidence for the irreversible conversion of beta- to alpha-endosulfan.

Previous studies have provided unequivocal evidence for the symmetry of beta-endosulfan and the corresponding asymmetry of alpha-endosulfan; the conversion of beta-endosulfan to alpha-endosulfan was identified. In this study, evidence from differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) experiments combined with computational chemistry calculations was used to propose a molecular mechanism for the corresponding conformational changes that occur in this process. DSC and NMR data of mixtures indicated that both isomers can influence the conformer populations in the solid, solution, and vapor phase. Computational chemistry demonstrated that the relative S==O configuration between alpha- and beta-isomers can be the intermediate state through which the conformations of alpha- and beta-isomers affect each other. Furthermore, calculations for mixtures indicated that the asymmetrical conformation of the sulfite in alpha-endosulfan can induce asymmetry in beta-endosulfan, and conversion to alpha-endosulfan occurs from this transition state.

Hydrolysis of chlorpyrifos in natural waters of the Chesapeake Bay.

Chlorpyrifos is the most widely used insecticide in the Chesapeake Bay region. Recent studies show that this organophospate chemical is consistently present in the air, rain and surface waters of the Chesapeake Bay region, suggesting a long environmental half-life. Hydrolytic degradation of chlorpyrifos is likely a dominant removal process, but existing hydrolysis data do not reflect conditions in the Chesapeake Bay. In this project, hydrolysis rates of chlorpyrifos were measured in sterilized, ambient water from the mouth of four Chesapeake Bay tributaries ranging in salinity from 0 to 17 ppt. The measured hydrolysis half-lives varied from 24 d in the Patuxent River to 126 d in the Susquehanna River. These results indicate that pH alone cannot be used as a single parameter to predict hydrolysis under field conditions. The influence of copper concentration, and other water constituents, need to be further evaluated as they may emerge as independent predictors to assess the fate of pesticides in natural systems.

Pesticides and amphibian population declines in California, USA.

Several species of anuran amphibians have undergone drastic population declines in the western United States over the last 10 to 15 years. In California, the most severe declines are in the Sierra Mountains east of the Central Valley and downwind of the intensely agricultural San Joaquin Valley. In contrast, coastal and more northern populations across from the less agrarian Sacramento Valley are stable or declining less precipitously. In this article, we provide evidence that pesticides are instrumental in declines of these species. Using Hyla regilla as a sentinel species, we found that cholinesterase (ChE) activity in tadpoles was depressed in mountainous areas east of the Central Valley compared with sites along the coast or north of the Valley. Cholinesterase was also lower in areas where ranid population status was poor or moderate compared with areas with good ranid status. Up to 50% of the sampled population in areas with reduced ChE had detectable organophosphorus residues, with concentrations as high as 190 ppb wet weight. In addition, up to 86% of some populations had measurable endosulfan concentrations and 40% had detectable 4,4'-dichlorodiphenyldichloroethylene, 4,4'-DDT, and 2,4'-DDT residues.

Runoff loss of pesticides and soil: a comparison between vegetative mulch and plastic mulch in vegetable production systems.

Current vegetable production systems use polyethylene (plastic) mulch and require multiple applications of agrochemicals. During rain events, runoff from vegetable production is enhanced because 50 to 75% of the field is covered with an impervious surface. This study was conducted to quantify off-site movement of soil and pesticides with runoff from tomato (Lycopersicon esculentum Mill.) plots containing polyethylene mulch and a vegetative mulch, hairy vetch (Vicia villosa Roth). Side-by-side field plots were instrumented with automated flow meters and samplers to measure and collect runoff, which was filtered, extracted, and analyzed to determine soil and pesticide loss. Seasonal losses of two to four times more water and at least three times as much sediment were observed from plots with polyethvlene mulch (55.4 to 146 L m(-2) and 247 to 535 g m(-2), respectively) versus plots with hairy vetch residue (13.7 to 75.7 L m(-2) and 32.8 to 118 g m(-2), respectively). Geometric means (+/-standard deviation) of total pesticide loads for chlorothalonil (tetrachloroisophthalonitrile) and alpha-and beta-endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro6,9-methano-2,4,3-benzodioxathiepin 3-oxide) for a runoff event were 19, 6, and 9 times greater from polyethylene (800+/-4.6, 17.6+/-3.9, and 39.1+/-4.9 microg m(-2), respectively) than from hairy vetch mulch plots (42+/-6.0, 2.8+/-5.0, and 4.3+/-4.6 microg m(-2), respectively) due to greater concentrations and larger runoff volumes. The increased runoff volume, soil loss, and off-site loading of pesticides measured in runoff from the polyethylene mulch suggests that this management practice is less sustainable and may have a harmful effect on the environment.

Fate of dietary perchlorate in lactating dairy cows: Relevance to animal health and levels in the milk supply.

Perchlorate is a goitrogenic anion that competitively inhibits the sodium iodide transporter and has been detected in forages and in commercial milk throughout the U.S. The fate of perchlorate and its effect on animal health were studied in lactating cows, ruminally infused with perchlorate for 5 weeks. Milk perchlorate levels were highly correlated with perchlorate intake, but milk iodine was unaffected, and there were no demonstrable health effects. We provide evidence that up to 80% of dietary perchlorate was metabolized, most likely in the rumen, which would provide cattle with a degree of refractoriness to perchlorate. Data presented are important for assessing the environmental impact on perchlorate concentrations in milk and potential for relevance to human health.

Acetylcholinesterase activity in grass shrimp and aqueous pesticide levels from South Florida drainage canals.

Freshwater drainage canals in South Florida are utilized to manage water in agricultural, urban, and water conservation areas and, as a result, collect urban and agricultural storm runoff that is discharged into the Atlantic Ocean and Gulf of Mexico. Pesticides in this runoff may be toxic to the biota inhabiting these waters. This study evaluated the effects of contaminants in South Florida canals draining into Biscayne Bay on the estuarine grass shrimp (Palaemonetes intermedius), a representative invertebrate species. Results of surface water analysis for pesticides indicated that eight pesticides out of 52 analyzed were detected. The herbicide metolachlor was found at all nine sites in the five canals sampled at concentrations up to 119 ng/L. Atrazine was detected at seven sites at concentrations up to 29 ng/L. Three organophosphate insecticides (chlorpyrifos, malathion, diazinon) were detected at three sites in two canals (Military and North). Grass shrimp from these three sites showed significantly reduced levels of the acetylcholinesterase enzyme as compared to control shrimp. These two canals are similar in the land use areas drained--urban and suburban and agriculture. The results suggest that monitoring organisms for AChE levels can be a means of detecting exposure to organophosphorus pesticide contamination.

Biochemical factors involved in the FSH action on amino acid transport in immature rat testes.

Testes of 15-day-old rats preincubated and incubated during different times with various doses of FSH (0.2; 2.0 and 20.0 mU/ml) in Krebs-Ringer bicarbonate (KRb) buffer increase the uptake of [14C] methylaminoisobutyric acid and [14C] aminoisobutyric acid. The basal and FSH stimulated amino acid transport occurs at absolute lower levels when the protein or glycoprotein synthesis is inhibited by cycloheximide (350 mumol/l) or tunicamycin (12 mumol/l) or when the microtubules are depolymerized with colchicine (1.2 mumol/l). However, the proportional increase of amino acid transport produced by FSH was maintained. The blockage of the voltage-dependent Ca++ channels with verapamil or the competitive inhibition of the bivalent ion channels by Co++ or Ni++ nullified the stimulatory action of FSH on the amino acid transport. Also quinine, that blocks the ATP dependent K+ channels, abolished the FSH action. It was concluded that in immature rat testes FSH stimulates amino acid transport through a mechanism involving voltage-dependent Ca++ channels and ATP-sensitive K+ channel.

Collection of nonpolar organic compounds from ambient air using polyurethane foam-granular adsorbent sandwich cartridges.

Glass cartridges containing 6-10 g of Tenax-GC or 15 g of XAD-2 resin packed between two slices of polyurethane foam (PUF) were used in a General Metal Works PS-1 high-volume sampler to collect chlorobenzenes (CBs) containing three to six chlorine atoms, hexachlorocyclohexanes (HCHs), and two-ring aromatic hydrocarbons from 35-385 m3 of air. Laboratory experiments were run by vaporizing known quantities of analytes into a clean airstream for sampling by the PS-1 system at 20 degrees C. Collection efficiencies, determined from mass balance of the quantities introduced and recovered, ranged from 70 to 120% for individual compounds and averaged 93% overall. Penetration of analytes to backup adsorbent traps showed an inverse correlation to vapor pressure. The method was used to collect the above compounds from urban and rural air.

Electrophysiological changes of Sertoli cells produced by the acute administration of amino acid and FSH.

Electrophysiological studies were carried out using seminiferous tubules of "Sertoli cell enriched testes" of rats irradiated in utero. Sertoli cells were inserted with glass microelectrodes in a superfusion chamber continuously perfused with KRb buffer. The topical application of FSH (4.0 mU/ml) produced a biphasic effect characterized by a rapid hyperpolarization (less than 3 s) followed by depolarization. The depolarizing effect of FSH was prolonged and potentiated in the presence of 5 mmol/l alpha-methylamino-isobutyric acid in the bath medium of the superfusion chamber. Verapamil, at a dose (250 mumol/l) that nullified the stimulatory action of FSH in the amino acid transport, suppressed the depolarizing effect of FSH. It was concluded that in immature rat testes FSH produces electrophysiological changes that mediate the stimulatory action of the amino acid transport.