Differences in Evaporation Between a Floating Pan and Class A Pan on Land1

Abstract: Research was conducted to develop a method for obtaining floating pan evaporation rates in a small (less than 10,000 m²) wetland, lagoon, or pond. Floating pan and land pan evaporation data were collected from March 1 to August 31, 2005, at a small natural wetland located in the alluvium of the Canadian River near Norman, Oklahoma, at the U.S. Geological Survey Norman Landfill Toxic Substances Hydrology Research Site. Floating pan evaporation rates were compared with evaporation rates from a nearby standard Class A evaporation pan on land. Floating pan evaporation rates were significantly less than land pan evaporation rates for the entire period and on a monthly basis. Results indicated that the use of a floating evaporation pan in a small free‐water surface better simulates actual physical conditions on the water surface that control evaporation. Floating pan to land pan ratios were 0.82 for March, 0.87 for April, 0.85 for May, 0.85 for June, 0.79 for July, and 0.69 for August.     

Effects of Cutrine-Plus® algaecide and predators on wood frog (Lithobates sylvaticus) tadpole survival and growth

Copper contamination is increasing in many aquatic ecosystems. One mode by which copper can be introduced into aquatic ecosystems is as an algaecide, such as Cutrine-Plus®. Using a mesocosm experiment, we examined the effects of Cutrine-Plus® on wood frog (Lithobates sylvaticus) tadpoles. In addition, we examined how the presence of a nonnative predator the Western mosquitofish (Gambusia affinis) may interact with exposure to Cutrine-Plus®. Exposure to our low and high Cutrine-Plus® treatments had a strong negative effect on the wood frog tadpoles, and survivorship was greatly decreased in the low treatment, and no tadpoles survived in the high treatment. Additionally, the tadpoles that survived the low treatment were significantly smaller than those in the control treatment. Mosquitofish had no effect on the survivorship or growth of wood frog tadpoles, and mosquitofish presence did not have a significant interaction with the Cutrine-Plus® treatments. Cutrine-Plus® clearly had a negative effect on wood frog tadpoles at the concentrations used in our experiment, which were at and below the label-recommended dosages, suggesting that the use of Cutrine-Plus® in natural ponds may have negative consequences for wood frog populations and possibly other amphibians.     

粉尘在巷道中的紊流传递分析

建立的粉尘在巷道中的传递方程是一个二维平流扩散输运方程。在巷道顶底板为吸收壁的条件下，导出了粉尘浓度分布函数。传统的工业沉降室沉降效率公式（横向混合模型）只是论文所列方程的一个特例。降低紊流强度和减小紊流扩散系数和纵向弥散系数均可提高沉降效率     

Recharge processes drive sulfate reduction in an alluvial aquifer contaminated with landfill leachate

Natural attenuation of contaminants in groundwater depends on an adequate supply of electron acceptors to stimulate biodegradation. In an alluvial aquifer contaminated with leachate from an unlined municipal landfill, the mechanism of recharge infiltration was investigated as a source of electron acceptors. Water samples were collected monthly at closely spaced intervals in the top 2 m of the saturated zone from a leachate-contaminated well and an uncontaminated well, and analyzed for delta(18)O, delta(2)H, non-volatile dissolved organic carbon (NVDOC), SO(4)(2-), NO(3)(-) and Cl(-). Monthly recharge amounts were quantified using the offset of the delta(18)O or delta(2)H from the local meteoric water line as a parameter to distinguish water types, as evaporation and methanogenesis caused isotopic enrichment in waters from different sources. Presence of dissolved SO(4)(2-) in the top 1 to 2 m of the saturated zone was associated with recharge; SO(4)(2-) averaged 2.2 mM, with maximum concentrations of 15 mM. Nitrate was observed near the water table at the contaminated site at concentrations up to 4.6 mM. Temporal monitoring of delta(2)H and SO(4)(2-) showed that vertical transport of recharge carried SO(4)(2-) to depths up to 1.75 m below the water table, supplying an additional electron acceptor to the predominantly methanogenic leachate plume. Measurements of delta(34)S in SO(4)(2-) indicated both SO(4)(2-) reduction and sulfide oxidation were occurring in the aquifer. Depth-integrated net SO(4)(2-) reduction rates, calculated using the natural Cl(-) gradient as a conservative tracer, ranged from 7.5x10(-3) to 0.61 mM.d(-1) (over various depth intervals from 0.45 to 1.75 m). Sulfate reduction occurred at both the contaminated and uncontaminated sites; however, median SO(4)(2-) reduction rates were higher at the contaminated site. Although estimated SO(4)(2-) reduction rates are relatively high, significant decreases in NVDOC were not observed at the contaminated site. Organic compounds more labile than the leachate NVDOC may be present in the root zone, and SO(4)(2-) reduction may be coupled to methane oxidation. The results show that sulfur (and possibly nitrogen) redox processes within the top 2 m of the aquifer are directly related to recharge timing and seasonal water level changes in the aquifer. The results suggest that SO(4)(2-) reduction associated with the infiltration of recharge may be a significant factor affecting natural attenuation of contaminants in alluvial aquifers.     

重力作用下尘粒运动的数值解法

提出了重力作用下尘粒运动的数值解法。依据尘粒的重力、浮力及所受到的阻力推出了尘粒自然沉降时的运动方程。当尘粒的运动在斯托克斯领域内时采用理论公式求解其运动轨迹,当尘粒的运动进入非斯托克斯领域内时,提出了修正斯托克斯公式的方法以达到用理论公式来近似模拟该领域内的尘粒自然沉降运动     

Using slow-release permanganate candles to remove TCE from a low permeable aquifer at a former landfill

Past disposal of industrial solvents into unregulated landfills is a significant source of groundwater contamination. In 2009, we began investigating a former unregulated landfill with known trichloroethene (TCE) contamination. Our objective was to pinpoint the location of the plume and treat the TCE using in situ chemical oxidation (ISCO). We accomplished this by using electrical resistivity imaging (ERI) to survey the landfill and map the subsurface lithology. We then used the ERI survey maps to guide direct push groundwater sampling. A TCE plume (100-600 μg L⁻¹) was identified in a low permeable silty-clay aquifer (K_h = 0.5 m d⁻¹) that was within 6 m of ground surface. To treat the TCE, we manufactured slow-release potassium permanganate candles (SRPCs) that were 91.4 cm long and either 5.1 cm or 7.6 cm in dia. For comparison, we inserted equal masses of SRPCs (7.6-cm versus 5.1-cm dia) into the low permeable aquifer in staggered rows that intersected the TCE plume. The 5.1-cm dia candles were inserted using direct push rods while the 7.6-cm SRPCs were placed in 10 permanent wells. Pneumatic circulators that emitted small air bubbles were placed below the 7.6-cm SRPCs in the second year. Results 15 months after installation showed significant TCE reductions in the 7.6-cm candle treatment zone (67-85%) and between 10% and 66% decrease in wells impacted by the direct push candles. These results support using slow-release permanganate candles as a means of treating chlorinated solvents in low permeable aquifers.     

Sinks for nitrogen inputs in terrestrial ecosystems: a meta-analysis of 15N tracer field studies

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthesize information about total ecosystem N retention (i.e., total ecosystem 15N recovery in plant and soil pools) across natural systems and N partitioning among ecosystem pools. The greatest recoveries of ecosystem 15N tracer occurred in shrublands (mean, 89.5%) and wetlands (84.8%) followed by forests (74.9%) and grasslands (51.8%). In the short term (< 1 week after 15N tracer application), total ecosystem 15N recovery was negatively correlated with fine-root and soil 15N natural abundance, and organic soil C and N concentration but was positively correlated with mean annual temperature and mineral soil C:N. In the longer term (3-18 months after 15N tracer application), total ecosystem 15N retention was negatively correlated with foliar natural-abundance 15N but was positively correlated with mineral soil C and N concentration and C:N, showing that plant and soil natural-abundance 15N and soil C:N are good indicators of total ecosystem N retention. Foliar N concentration was not significantly related to ecosystem 15N tracer recovery, suggesting that plant N status is not a good predictor of total ecosystem N retention. Because the largest ecosystem sinks for 15N tracer were below ground in forests, shrublands, and grasslands, we conclude that growth enhancement and potential for increased C storage in aboveground biomass from atmospheric N deposition is likely to be modest in these ecosystems. Total ecosystem 15N recovery decreased with N fertilization, with an apparent threshold fertilization rate of 46 kg N x ha(-1) x yr(-1) above which most ecosystems showed net losses of applied 15N tracer in response to N fertilizer addition.