HYDROLOGIC EVALUATION OF RESIDENTIAL RAIN GARDENS USING A STORMWATER RUNOFF SIMULATOR

Engineered bioretention cells with underdrains have shown water quality and hydrologic benefits for abating urban stormwater problems. Less is known about the hydrologic performance of residential rain gardens that rely on in situ soil infiltration as the primary mechanism of volume control. Eleven residential rain gardens in Lincoln, Nebraska, were evaluated using a variable-rate stormwater runoff simulator. A volume-based water quality volume (WQV) design storm of 3.0 cm was applied to each rain garden as an SCS Type II runoff hydrograph until the system began overflowing to test the rain gardens for surface and subsurface storage capacity, drawdown rate, ponding depth, and overflow characteristics. Every rain garden tested drained in 30 h or less, with six gardens draining in less than 1 h. Rain garden surface storage capacity was poor, retaining on average only 16% of the WQV. On average, the rain gardens studied could store and infiltrate only 40% of the WQV, with only two gardens able to store and infiltrate greater than 90% of the WQV. On average, 59% of the runoff was captured as subsurface storage. Results of this study indicate that these 2- to 4-year-old rain gardens are limited not by drain times and rates, which often met or exceeded common design recommendations, but rather by inadequate surface storage characteristics. Extrapolating measured surface storage volumes to hypothetical systems with evenly graded depths of 15.2 cm, a minimum local depth recommendation, resulted in only one garden with enough storage to contain the WQV. On average, the extrapolated storage held only 65% of the WQV. It was shown that subsurface storage can make up for a lack of surface storage; the systems studied herein had an average of 2.7 times more subsurface storage than surface storage as a percentage of inflow volume before overflow began

Prevalence and co-infection of Toxoplasma gondii and Neospora caninum in Apodemus sylvaticus in an area relatively free of cats

The protozoan parasite Toxoplasma gondii is prevalent worldwide and can infect a remarkably wide range of hosts despite felids being the only definitive host. As cats play a major role in transmission to secondary mammalian hosts, the interaction between cats and these hosts should be a major factor determining final prevalence in the secondary host. This study investigates the prevalence of T. gondii in a natural population of Apodemus sylvaticus collected from an area with low cat density (<2·5 cats/km2). A surprisingly high prevalence of 40·78% (95% CI: 34·07%–47·79%) was observed despite this. A comparable level of prevalence was observed in a previously published study using the same approaches where a prevalence of 59% (95% CI: 50·13%–67·87%) was observed in a natural population of Mus domesticus from an area with high cat density (>500 cats/km2). Detection of infected foetuses frompregnant dams in both populations suggests that congenital transmission may enable persistence of infection in the absence of cats. The prevalences of the related parasite, Neospora caninum were found to be low in both populations (A. sylvaticus: 3·39% (95% CI: 0·12%–6·66%); M. domesticus: 3·08% (95% CI: 0·11%–6·05%)). These results suggest that cat density may have a lower than expected effect on final prevalence in these ecosystems

Elicitation of Neutralizing Antibodies Directed against CD4-Induced Epitope(s) Using a CD4 Mimetic Cross-Linked to a HIV-1 Envelope Glycoprotein

The identification of HIV-1 envelope glycoprotein (Env) structures that can generate broadly neutralizing antibodies (BNAbs) is pivotal to the development of a successful vaccine against HIV-1 aimed at eliciting effective humoral immune responses. To that end, the production of novel Env structure(s) that might induce BNAbs by presentation of conserved epitopes, which are otherwise occluded, is critical. Here, we focus on a structure that stabilizes Env in a conformation representative of its primary (CD4) receptor-bound state, thereby exposing highly conserved “CD4 induced” (CD4i) epitope(s) known to be important for co-receptor binding and subsequent virus infection. A CD4-mimetic miniprotein, miniCD4 (M64U1-SH), was produced and covalently complexed to recombinant, trimeric gp140 envelope glycoprotein (gp140) using site-specific disulfide linkages. The resulting gp140-miniCD4 (gp140-S-S-M64U1) complex was recognized by CD4i antibodies and the HIV-1 co-receptor, CCR5. The gp140-miniCD4 complex elicited the highest titers of CD4i binding antibodies as well as enhanced neutralizing antibodies against Tier 1 viruses as compared to gp140 protein alone following immunization of rabbits. Neutralization against HIV-27312/V434M and additional serum mapping confirm the specific elicitation of antibodies directed to the CD4i epitope(s). These results demonstrate the utility of structure-based approach in improving immunogenic response against specific region, such as the CD4i epitope(s) here, and its potential role in vaccine application

HYDROLOGIC EVALUATION OF RESIDENTIAL RAIN GARDENS USING A STORMWATER RUNOFF SIMULATOR

Engineered bioretention cells with underdrains have shown water quality and hydrologic benefits for abating urban stormwater problems. Less is known about the hydrologic performance of residential rain gardens that rely on in situ soil infiltration as the primary mechanism of volume control. Eleven residential rain gardens in Lincoln, Nebraska, were evaluated using a variable-rate stormwater runoff simulator. A volume-based water quality volume (WQV) design storm of 3.0 cm was applied to each rain garden as an SCS Type II runoff hydrograph until the system began overflowing to test the rain gardens for surface and subsurface storage capacity, drawdown rate, ponding depth, and overflow characteristics. Every rain garden tested drained in 30 h or less, with six gardens draining in less than 1 h. Rain garden surface storage capacity was poor, retaining on average only 16% of the WQV. On average, the rain gardens studied could store and infiltrate only 40% of the WQV, with only two gardens able to store and infiltrate greater than 90% of the WQV. On average, 59% of the runoff was captured as subsurface storage. Results of this study indicate that these 2- to 4-year-old rain gardens are limited not by drain times and rates, which often met or exceeded common design recommendations, but rather by inadequate surface storage characteristics. Extrapolating measured surface storage volumes to hypothetical systems with evenly graded depths of 15.2 cm, a minimum local depth recommendation, resulted in only one garden with enough storage to contain the WQV. On average, the extrapolated storage held only 65% of the WQV. It was shown that subsurface storage can make up for a lack of surface storage; the systems studied herein had an average of 2.7 times more subsurface storage than surface storage as a percentage of inflow volume before overflow began

Tillage Effects on Soil Quality Indicators and Nematode Abundance in Loessial Soil under Long- Term No-Till Production

Soil quality indicators and nematode abundance were characterized in a loessial soil under long-term conservation tillage to evaluate the effects of no-till, double-disk, chisel, and moldboard plow treatments. Indicators included soil electrical conductivity (EC), soil texture, soil organic matter (SOM), and total particulate organic matter (tPOM). Nematode abundance was positively correlated with EC, silt content, and total POM and negatively correlated with clay content. Clay content was the main source of variation among soil quality indicators and was negatively correlated with nematode abundance and most indicators. The gain in SOM in the no-till system amounted to 10887 kg over the 24 years or 454 kg ha-1 year-1, about half of this difference (45%) resulting from soil erosion in plowed soils. The balance of gain in SOM with no till (249 kg ha-1 year-1) was due to SOM sequestration with no till. No-till management reduced soil erosion, increased SOM, and enhanced soil physical characteristics