Toward the improvement of total nitrogen deposition budgets in the United States.

Frameworks for limiting ecosystem exposure to excess nutrients and acidity require accurate and complete deposition budgets of reactive nitrogen (Nr). While much progress has been made in developing total Nr deposition budgets for the U.S., current budgets remain limited by key data and knowledge gaps. Analysis of National Atmospheric Deposition Program Total Deposition (NADP/TDep) data illustrates several aspects of current Nr deposition that motivate additional research. Averaged across the continental U.S., dry deposition contributes slightly more (55%) to total deposition than wet deposition and is the dominant process (>90%) over broad areas of the Southwest and other arid regions of the West. Lack of dry deposition measurements imposes a reliance on models, resulting in a much higher degree of uncertainty relative to wet deposition which is routinely measured. As nitrogen oxide (NOx) emissions continue to decline, reduced forms of inorganic nitrogen (NHx = NH3 + NH4+) now contribute >50% of total Nr deposition over large areas of the U.S. Expanded monitoring and additional process-level research are needed to better understand NHx deposition, its contribution to total Nr deposition budgets, and the processes by which reduced N deposits to ecosystems. Urban and suburban areas are hotspots where routine monitoring of oxidized and reduced Nr deposition is needed. Finally, deposition budgets have incomplete information about the speciation of atmospheric nitrogen; monitoring networks do not capture important forms of Nr such as organic nitrogen. Building on these themes, we detail the state of the science of Nr deposition budgets in the U.S. and highlight research priorities to improve deposition budgets in terms of monitoring and flux measurements, leaf- to regional-scale modeling, source apportionment, and characterization of deposition trends and patterns.

Case study of the effects of atmospheric aerosols and regional haze on agriculture: an opportunity to enhance crop yields in China through emission controls?

The effect of atmospheric aerosols and regional haze from air pollution on the yields of rice and winter wheat grown in China is assessed. The assessment is based on estimates of aerosol optical depths over China, the effect of these optical depths on the solar irradiance reaching the earth's surface, and the response of rice and winter wheat grown in Nanjing to the change in solar irradiance. Two sets of aerosol optical depths are presented: one based on a coupled, regional climate/air quality model simulation and the other inferred from solar radiation measurements made over a 12-year period at meteorological stations in China. The model-estimated optical depths are significantly smaller than those derived from observations, perhaps because of errors in one or both sets of optical depths or because the data from the meteorological stations has been affected by local pollution. Radiative transfer calculations using the smaller, model-estimated aerosol optical depths indicate that the so-called "direct effect" of regional haze results in an approximately 5-30% reduction in the solar irradiance reaching some of China's most productive agricultural regions. Crop-response model simulations suggest an approximately 1:1 relationship between a percentage increase (decrease) in total surface solar irradiance and a percentage increase (decrease) in the yields of rice and wheat. Collectively, these calculations suggest that regional haze in China is currently depressing optimal yields of approximately 70% of the crops grown in China by at least 5-30%. Reducing the severity of regional haze in China through air pollution control could potentially result in a significant increase in crop yields and help the nation meet its growing food demands in the coming decades.

Upper gastrointestinal bleeding following renal transplantation.

Upper gastrointestinal bleeding has been shown to be a common complication of renal transplantation and one which carries a significant risk of mortality. In a retrospective review of 200 consecutive renal transplants in 194 patients, we found an incidence of only 6 per cent and a mortality rate of 8.3 per cent. Allograft survival in this group of patients was 58 per cent. These results are the product of careful preoperative evaluation, close attention to the patients for early signs of bleeding, and aggressive diagnostic and therapeutic intervention at the first evidence of bleeding. We also report an association of hypercalcemia with post-transplant upper gastrointestinal bleeding, with cessation of bleeding after parathyroidectomy.

Pseudallescheria boydii (Petriellidium boydii) infection of the orbit.

A 10-year-old male developed a chronic orbital infection following penetrating trauma and retention of an orbital foreign body. Diagnosis of infection with Pseudallescheria boydii (Petriellidium boydii) was made by fungal smear and culture. Sensitivity tests indicated the organism was resistant to amphotericin B. Surgical debridement of the inferior orbit and removal of the foreign body was followed by a six-week course of intravenous miconazole. The patient has shown no signs of recurrence in a two-year follow-up period. To our knowledge, this is the first reported case of orbital infection with Pseudallescheria boydii, although the organism has been reported in cornea, ocular, and peri-orbital sinus infections.

Hypercalcemia-induced upper gastrointestinal bleeding after renal transplantation.

Hypercalcemia is common in patients after renal transplantation and may stimulate gastrin hypersecretion with associated peptic disease. We report on 2 patients with hypercalcemia and life-threatening gastrointestinal hemorrhage controlled by subtotal parathyroidectomy. Retrospective review of our last 10 patients with gastrointestinal hemorrhage revealed that all of those with normal renal function had elevated serum calcium levels. Because of the increased mortality associated with gastrointestinal hemorrhage in renal transplant patients (43%), patients prone to development of hypercalcemia may benefit from early subtotal parathyroidectomy.

Occult lead intoxication in patients with gout and kidney disease.

Ten patients with gout, hypertension, and mild to moderate renal insufficiency were studied for possible lead nephropathy by measuring stimulated urinary lead excretion. Seven had a history of lead exposure, 5 from illegal alcohol and 2 from industrial sources. Occult lead was assessed by 24 h urine collection measurements over a 72 h period after intramuscular administration of calcium disodium EDTA. Two patients with a history of lead exposure excreted 707 and 687 micrograms Pb/72 h, respectively, and a 3rd excreted 506 micrograms Pb/72 h. The remainder had a normal response, with mean urinary lead excretion of 251 +/- 42 micrograms Pb/72 h. Since we were unable to demonstrate that lead was important to the pathogenesis of the renal we were unable to demonstrate that lead was important to the pathogenesis of the renal failure in 7 patients despite a positive history of lead exposure in 2, we suggest that factors other than lead may be the cause of renal failure in most patients with gout and renal disease.