The recovery of ammonia and hydrogen sulfide from ground-level area sources using dynamic isolation flux chambers: bench-scale studies

Controlled bench-scale laboratory experiments were conducted to evaluate the recovery of ammonia (NH3) and hydrogen sulfide (H2S) from dynamic isolation flux chambers. H2S (80-4000 ppb) and NH3 (5000-40,000 ppb) samples were diffused through the flux chamber to simulate ground level area source emissions while measuring the inlet and outlet flux chamber concentrations simultaneously. Results showed that the recovery of H2S during a 30-min sampling time was almost complete for concentrations >2000 ppb. At the lowest concentration of 80 ppb, 92.55% of the H2S could be recovered during the given sampling period. NH3 emissions exhibited similar behavior between concentrations of 5000-40,000 ppb. Within the 30-min sampling period, 92.62% of the 5000-ppb NH3 sample could be recovered. Complete recovery was achieved for concentrations >40,000 ppb. Predictive equations were developed for gas adsorption. From these equations, the maximum difference between chamber inlet and outlet concentrations of NH3 or H2S was predicted to be 7.5% at the lowest concentration used for either gas. In the calculation of emission factors for NH3 and H2S, no adsorption correction factor is recommended for concentrations >37,500 ppb and 2100 ppb for NH3 and H2S, respectively. The reported differences in outlet and inlet concentration above these ranges are outside the fullscale sensitivity of the gas sensing equipment. The use of 46-90 m of Teflon tubing with the flux chambers has apparently no effect on gas adsorption, because recovery was completed almost instantaneously at the beginning of the tests.     

Assessment of soil erosion under rainfed sugarcane in KwaZulu‐Natal,South Africa

Soil erosion from agricultural land use runoff is a major threat to the sustainability of soil composition and water resource integrity. Sugarcane is an important cash and food security crop in South Africa, subjected to an intensive soil erosion, and consequently, severe land degradation. This study aimed to investigate soil erosion and associated soil and cover factors under rainfed sugarcane, in a small catchment, KwaZulu‐Natal, South Africa. Three replicated runoff plots were installed at different slope positions (down, mid and upslope) within cultivated sugarcane fields to monitor soil erosion during the 2016–2017 rainy season. On average, annual runoff (RF) was significantly greater from 10 m² plots with 1163.77 ± 2.63 l/m/year compared to 1 m² plots. However, sediment concentration (SC) was significantly lower in 10 m² (0.34 ± 0.04 g/l) compared to 1 m² (6.94 ± 0.24 g/l) plots. The annual soil losses (SL) calculated from 12 rainfall events was 58.36 ± 0.77 and 8.84 ± 0.20 t/ha from 1 m² and 10 m² plots, respectively. The 1 m² plot, SL (2.4 ± 1.41 ton/ha/year) in the upslope experienced 33% more loss than the midslope and 50% more loss than the downslope position. SL was relatively lower from the 10 m² plots than the 1 m² plots, which is explained by high sediment deposition at the greater plot scale. SL was negatively correlated with the soil organic carbon stocks (r = ?0.82) and soil surface cover (r = ?0.55). RF decreased with the increase of slope gradient (r = ?0.88) and soil infiltration rate (r = ?0.87). There were considerable soil losses from cultivated sugarcane fields with low organic matter. These findings suggest that to mitigate soil erosion, soil organic carbon stocks and vegetation cover needs to be increased through appropriate land management practices, particularly in cultivated areas with steep gradients.     

Protective clothing for pesticide operators: part I – selection of a reference test chemical for penetration testing

A systematic approach was taken to develop a database for protective clothing for pesticide operators; results are reported as a two-part series. Part I describes the research studies that led to identification of a pesticide formulation that could serve as a reference test chemical for further testing. Measurement of pesticide penetration was conducted using different types of pesticide formulations. Six fabrics were tested using 10 formulations at different concentrations. Three formulations were subsequently selected for further testing. Analysis of the data indicated that, when compared with other formulations, mean percent penetration of 5% Prowl 3.3 EC [emulsifiable concentrate diluted to 5% active ingredient (pendimethalin)] is either similar to or higher than most test chemicals. Those results led to choosing 5% Prowl 3.3 EC as a reference test liquid. Part II of the study, published as a separate paper, includes data on a wide range of textile materials.     

The adoption of a Climate Disaster Resilience Index in Chennai,India

Results derived from the Climate Disaster Resilience Index (CDRI)—consisting of five dimensions (economic, institutional, natural, physical, and social), 25 parameters, and 125 variables—reflect the abilities of people and institutions to respond to potential climate‐related disasters in Chennai, India. The findings of this assessment, applied in the 10 administrative zones of the city, reveal that communities living in the northern and older parts of Chennai have lower overall resilience as compared to the flourishing areas (vis‐à‐vis economic growth and population) along the urban fringes. The higher resilience of communities along the urban fringes suggests that urbanisation may not necessarily lead to a deterioration of basic urban services, such as electricity, housing, and water. This indication is confirmed by a strong statistical correlation between physical resilience and population growth in Chennai. The identification of the resilience of different urban areas of Chennai has the potential to support future planning decisions on the city's scheduled expansion.     

Role of climate and competitors in limiting fitness across range edges of an annual plant

It is often assumed that the geographic distributions of species match their climatic tolerances, but this assumption is not frequently tested. Moreover, few studies examine the relative importance of abiotic and biotic factors for limiting species ranges. We combined multiple approaches to assess the extent to which fitness of a widespread native annual legume, Chamaecrista fasciculata, decreases at and beyond its northern and western range edges, and how this is influenced by the presence of neighbors. First, we examined plant fitness and the effect of neighbors in natural populations at different geographic range locations for three years. Fitness decreased toward the northern range edge, but not the western edge. Neighbor removal had a consistently positive effect on seedpod production across all years and sites. Second, we established experimental populations at sites within the range, and at and beyond the northern and western range edges. We tracked individual fitness and recorded seedling recruitment in the following year (a complete generation) to estimate population growth rate. Individual fitness and population growth declined to near zero beyond both range edges, indicating that C. fasciculata with its present genetic composition will not establish in these regions, given conditions currently. We also carried out a neighbor removal treatment. Consistent with the natural populations, neighbors reduced seedpod production of reproductive adults. However, neighbors also increased early-season survival, and this positive effect early in life history resulted in a net positive effect of neighbors on lifetime fitness at most range locations. Our data show that the population growth rate of C. fasciculata includes values above replacement, and populations are well adapted to conditions up to the edge of the range, whereas the severely compromised fitness at sites beyond the edge precludes immediate establishment of populations and thereby impedes adaptation to these conditions.     

An overview of BORIS: Bioavailability of Radionuclides in Soils

The ability to predict the consequences of an accidental release of radionuclides relies mainly on the level of understanding of the mechanisms involved in radionuclide interactions with different components of agricultural and natural ecosystems and their formalisation into predictive models. Numerous studies and databases on contaminated agricultural and natural areas have been obtained, but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from incomplete knowledge about radionuclide interactions with the soil matrix, soil moisture, and biological elements in the soil and additional pollutants, which may be found in such soils. In the 5th European Framework Programme entitled Bioavailability of Radionuclides in Soils (BORIS), we investigated the role of the abiotic (soil components and soil structure) and biological elements (organic compounds, plants, mycorrhiza, and microbes) in radionuclide sorption/desorption in soils and radionuclide uptake/release by plants. Because of the importance of their radioisotopes, the bioavailability of three elements, caesium, strontium, and technetium has been followed. The role of one additional non-radioactive pollutant (copper) has been scrutinised in some cases. Role of microorganisms (e.g., K(d) for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (e.g., changes in plant physiology affect radionuclide uptake by plants), and the presence of mycorrhizal fungi (e.g., interferes with the uptake of radionuclides by plants) have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST and BIORUR, specifically modelling radionuclide sorption/desorption from soil matrices and radionuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance its prediction ability by introducing the concept of bioavailability factor for radionuclides.     

Hydraulic management of a soil moisture controlled SDI wastewater dispersal system in an Alabama Black Belt soil

Rural areas represent approximately 95% of the 14000 km(2) Alabama Black Belt, an area of widespread Vertisols dominated by clayey, smectitic, shrink-swell soils. These soils are unsuitable for conventional onsite wastewater treatment systems (OWTS) which are nevertheless widely used in this region. In order to provide an alternative wastewater dosing system, an experimental field moisture controlled subsurface drip irrigation (SDI) system was designed and installed as a field trial. The experimental system that integrates a seasonal cropping system was evaluated for two years on a 500-m(2) Houston clay site in west central Alabama from August 2006 to June 2008. The SDI system was designed to start hydraulic dosing only when field moisture was below field capacity. Hydraulic dosing rates fluctuated as expected with higher dosing rates during warm seasons with near zero or zero dosing rates during cold seasons. Lower hydraulic dosing in winter creates the need for at least a two-month waste storage structure which is an insurmountable challenge for rural homeowners. An estimated 30% of dosed water percolated below 45-cm depth during the first summer which included a 30-year historic drought. This massive volume of percolation was presumably the result of preferential flow stimulated by dry weather clay soil cracking. Although water percolation is necessary for OWTS, this massive water percolation loss indicated that this experimental system is not able to effective control soil moisture within its monitoring zone as designed. Overall findings of this study indicated that soil moisture controlled SDI wastewater dosing is not suitable as a standalone system in these Vertisols. However, the experimental soil moisture control system functioned as designed, demonstrating that soil moisture controlled SDI wastewater dosing may find application as a supplement to other wastewater disposal methods that can function during cold seasons.     

New expansions in old clades: population genetics and phylogeny of Gnatholepis species (Teleostei: Gobioidei) in the Pacific

Species of the reef goby genus Gnatholepis exhibit enormous geographic ranges with little evidence of population segregation detectable based on mitochondrial DNA. To determine if genetic differentiation is evident with more rapidly evolving markers, seven microsatellite loci were screened from the species Gnatholepis anjerensis and G. scapulostigma and population segregation was tested among fish from across the South Pacific. Both AMOVA and pairwise F _ST analyses showed that, in concordance with previous mitochondrial results, most genetic variance occurs within individual populations, as population differentiation is evident only over the largest distances (>3,700 km). This result is contrasted with previous studies demonstrating that despite their relatively long larval periods, some gobiid fishes exhibit population differentiation on small (<100 km) geographic scales. Coalescence analysis showed that current Pacific populations of these species originated in the Pleistocene, presumably related to sea level fluctuations associated with episodes of glaciation. However, rate analysis based on a phylogeny of Gnatholepis species indicates that the species themselves are much older, consistent with a complex history of rapid, short-term population contractions and expansions, with corresponding rapid dispersal.