High-density Treatment Research Articles

Infographic: Half-dose photodynamic therapy versus high-density subthreshold micropulse laser treatment in patients with chronic central serous chorioretinopathy: the PLACE trial.

Infographic: Half-dose photodynamic therapy versus high-density subthreshold micropulse laser treatment in patients with chronic central serous chorioretinopathy: the PLACE trial.

Density and row spacing of short-season cotton suitable for machine picking in the cotton region of Yellow River Basin.

To determine the suitable planting density and row spacing of short-season cotton suitable for machine picking in the Yellow River Basin of China, we conducted a two-year field experiment in Dezhou during 2018-2019. The experiment followed a split-plot design, with planting density (82500 plants·hm-2 and 112500 plants·hm-2) as the main plots and row spacing (equal row spacing of 76 cm, wide-narrow row spacing of 66 cm+10 cm, equal row spacing of 60 cm) as the subplots. We examined the effects of planting density and row spacing on growth and development, canopy structure, seed cotton yield and fiber quality of short-season cotton. The results showed that plant height and LAI under high density treatment were significantly greater than those under low density treatment. The transmittance of the bottom layer was significantly lower than under low density treatment. Plant height under 76 cm equal row spacing was significantly higher than that under 60 cm equal row spacing, while that under wide-narrow row spacing (66 cm +10 cm) was significantly smaller than that under 60 cm equal row spacing in peak bolling stage. The effects of row spacing on LAI varied between the two years, densities, and growth stages. On the whole, the LAI under the wide-narrow row spacing (66 cm+10 cm) was higher, with the curve declining gently after the peak, and it was higher than that in the two cases of equal row spacing in the harvest time. The change in transmittance of the bottom layer presented the opposite trend. Density, row spacing, and their interaction had significant effects on seed cotton yield and its components. In both years, seed cotton yield was the highest (3832 kg·hm-2 in 2018, 3235 kg·hm-2 in 2019) under wide-narrow row spacing (66 cm+10 cm), and it was more stable at high densities. Fiber quality was less affected by density and row spacing. To sum up, the optimal density and row spacing of short-season cotton were as follows: density with 112500 plants·hm-2 and wide-narrow row spacing (66 cm+10 cm).

How herbivores reshape a macroalgal community on a Little Cayman coral reef: The role of herbivore type and density

Many coral reefs throughout the world continue to decline in health and resilience. In the Caribbean, much of this decline has been attributed to increases in algal cover due to the loss of herbivores such as herbivorous fishes, especially large parrotfish, and the sea urchin Diadema antillarum. In recent years, the combination of protections and natural recovery has helped these herbivores, particularly parrotfishes, to recover in some areas. This recovery has led to questions about how different herbivores affect both the overall benthic cover of macroalgae and the specific composition of algal communities. Toward that end, we designed a caging experiment in Little Cayman to manipulate density and type of grazers. Treatments included full cages (1.27 cm wire mesh) with 4 D. antillarum/m2 added, full cages with 1 D. antillarum/m2, lidless cages (fences) open to herbivorous fishes without D. antillarum, full cages (herbivore exclosures) that excluded most fishes and urchins and open cageless controls. Benthic cover was quantified to assess differences in percent cover and community structure of macroalgae and benthic invertebrates throughout the 5-month study. As the experiment proceeded, both percent algal cover and algal community structure in the full herbivore exclosures, treatments open to fishes (open plots and fences), and treatments with D. antillarum (both densities) diverged. No changes were observed in percent cover of corals or other benthic invertebrates. Overall, reductions in percent algal cover were greater in the high density (4/m2) D. antillarum treatment compared to the low density (1/m2) D. antillarum treatment or those treatments where fishes were allowed access. As expected, greater densities of sea urchins reduced algal cover more quickly. However, these high density treatments also affected the D. antillarum themselves. The condition of the urchins (assessed as ratio of mass to test diameter) at the conclusion of the experiment declined in the 4 D. antillarum/m2 treatment compared to urchins in the 1 D. antillarum/m2 treatment and natural populations. Moreover, high densities of D. antillarum were better able to reduce the abundance of the brown macroalgae Lobophora spp. and Dictyota spp. compared to natural assemblages of herbivorous fishes. These findings suggest that these different types of herbivores, i.e., fishes and D. antillarum, exert different pressures on available algae. Their relative abundances will likely dictate macroalgal community structure on Caribbean coral reefs, and thus the suitability of a reef for the settlement of vital sessile organisms, especially corals.

The effects of stocking density and artifical substrate on production of pacific white shrimp Litopenaeus vannamei and water quality dynamics in greenhouse-based biofloc systems

Inland shrimp aquaculture has increased in popularity in recent years as a means of providing fresh seafood to consumers away from the coasts. With adequate marketing,fresh shrimp fetch relatively high prices and can give farmers a means of diversifying, production. In temperate regions such as Kentucky, low-cost high tunnel greenhouses may be used to extend the growing season of warm-weather crops, including tropical animals such as penaeid shrimp. To optimize investments, inland producers are constantly exploring methods to increase overall production. A 100 day-long study examined the effects of stocking density and artificial substrates on water quality, stable isotope dynamics, and production of Litopenaeus vannamei using biofloc-based aquaculture systems in greenhouses. Four treatments were compared: High Density Substrate (HD/S), High Density No-Substrate (HD/NS), Low, Density Substrate (LD/S), and Low Density No-Substrate (LD/NS). Four high tunnel greenhouses each contained four 10.9 m3 tanks. The experiment was blocked by location such that one replicate from each treatment was randomly assigned within each greenhouse to account for potential environmental variation. Each tank was outfitted with a settling chamber for solids filtration, and 13.1 m2 of polypropylene, construction safety fencing was used as substrate in the substrate-containing tanks. Shrimp were stocked into the experimental systems at 2.71 g mean weight; high density treatments were stocked with 300 shrimp/m3, while low density treatments were stocked with 200 shrimp/m3. Water temperatures were significantly lower over the course of the entire study within substrate treatments. pH throughout the study was significantly lower within substrate treatments and high density treatments. Stable isotope data indicated that very little of the carbon and nitrogen in shrimp tissues was likely sourced from biofloc and periphyton material. Low density treatments had significantly lower FCRs than high density treatments. However, the addition of substrate in the HD/S treatment resulted in significantly more efficient shrimp FCR than was observed in the HD/NS treatment. The HD/S treatment also had significantly higher, shrimp biomass than all other treatments. High density treatments had significantly higher FCR and lower survival than low density treatments. This study demonstrates that artificial substrates can reduce some of the negative effects of high shrimp stocking density, with significant improvements in FCR and biomass production. Although it is important to note the implications for water quality, adding substrate to facilitate high density shrimp culture in high tunnel greenhouses can facilitate higher stocking density without compromising the size of the animals

Short-Term Stress Response of Juvenile Rainbow Trout Subjected to Two Different Rearing Densities

Juvenile rainbow trout Oncorhynchus mykiss were subjected to one of four treatments in a two-by-two experimental design: 1) fed at a density of 1.8 g/m3, 2) Fasted at 1.8 g/m3, 3) fed at 30.1 g/m3, and 4) fasted at 30.1 g/m3. Blood glucose and hematocrit were measured at 4, 6, 48, 168, and 336 hours after placement in one of the two rearing densities, with relative fin lengths and organosomatic indices recorded at 336 hours. Glucose levels over time were not significantly different among the density and feeding treatments. Hematocrit levels over time were also not significantly different. Total lengths, weight, hepatosomatic index, viscerosomatic index, and any of the relative fin lengths were not significantly different between the high and low densities. However, the hepatosomatic index was significantly greater in the fed fish compared to those fasted. The splenosomatic index was significantly greater in the higher density treatment. These results likely indicate no short-term stress response to the higher rearing density used in this short-term experiment and no interaction between starvation and density-related stressors.

Effects of two categorically differing emergent wetland plants on evapotranspiration

AbstractAlthough wetlands are an important component of many landscapes, emergent plants have had variable impacts on wetland hydrology. In the present study, similar to what others have done with emergent plants, we investigated the impacts of black willow (Salix nigra Marshall) and Pennsylvania smartweed (Persicaria pensylvanica L.) on water loss from standing water relative to water loss with no emergent plants from 2018 to 2020. Pans were established with soil and standing water for three replications of five treatments: open water control, low population density black willow, high density black willow, low density smartweed, and high density smartweed. Each week during the growing season water levels, water temperature, leaf area index, and height were recorded. Pans were then refilled to the standard level. The assumption was that open water was just evaporation and the increase in water loss in the presence of plants was due to transpiration. Thus, we could partition water loss between evaporation and transpiration by calculating the difference between pans without plants and pans with plants. This difference is the transpiration by the plants. Water temperature was measured to check on any possible shading effect. Open water evaporation was lower than black willow and smartweed evapotranspiration. Mean increases in water use relative to the control were 37% for smartweed and 66% for black willow. These differences were even more dramatic when calculated for only the last 2 years. Smartweed increased water use by 40% and black willow by 92%. Because pans with plants had lower maximum daily water temperatures than those of the control in the summer, the increased water loss with plants was largely due to transpiration. Smartweed transpired more than willows. The willow root system and leaf area greatly increased after the first year, resulting in more water loss and lower summer water temperature. Low and high density treatments did not differ significantly for any metrics gathered, with few exceptions. This evapotranspiration information addresses wetland water balance questions and is useful for process‐based models.

Stress response of juvenile rainbow trout reared at three densities

High rearing densities (kg of fish per rearing unit volume) can impact fish health and growth. This study evaluated the stress levels (as indicated by blood glucose) and growth of juvenile Shasta strain rainbow trout (Oncorhynchus mykiss) reared at three densities in 1.8-m diameter circular tanks for 111 days. Initial and final rearing densities for each treatment were: low (4.48 and 47.56 kg/m3), medium (5.96 and 60.60 kg/m3), and high (7.49 and 72.42 kg/m3). Throughout the experiment, blood glucose levels from individual fish were not significantly different among the three density treatments. At the end of the experiment, total tank weights and gain were significantly greater in the high-density treatment than the medium-density treatment, which in turn was significantly greater than the low-density treatment. However, percent gain was significantly greater in the low-density treatment. Feed conversion ratio was significantly lower in the high-density treatment compared to the low-density treatment, with the ratio in the medium-density treatment similar to the other two treatments. The results of this study indicate that higher rearing densities do not negatively impact juvenile Shasta strain rainbow trout stress or hatchery rearing performance.

Brown trout density effects on the macroinvertebrate and biofilm communities of headwater streams: a cage experiment

Salmo trutta is a key species of headwater streams that is able to influence the structure of these ecosystems through predation. Populations of this species are being threatened by climate change and hydrological alteration. In order to understand how their disappearance would affect the ecosystem structure of headwater streams, we used cage experiments to analyse different biofilm and macroinvertebrate structural parameters and the biodiversity of their communities under different trout densities. Due to a heavy rain event, our experiment was destroyed on the 10th day, but the role of trout as stream ecosystemic structure drivers was observed, as multiple parameters were modulated by their presence or absence. In the high-density treatments, a significant reduction in the biomass of macroinvertebrate families that fed on biofilms was observed due to direct predation on them, which caused the biofilms to be more autotrophic. A decrease in brown trout population densities could cause cascading trophic effects on the ecosystem structure of headwater streams

Сочетание криогенной деформации и электроимпульсной обработки как способ получения ультрамелкозернистых металлов

The data of a comparative analysis of the structure and hardness of pure metals with a face-centered cubic lattice – aluminum, nickel and copper, subjected to complex thermomechanical treatment (TMT), including isothermal cryogenic rolling at liquid nitrogen temperature and subsequent high-density electropulse treatment (EPT) were presented. The main stages, features and advantages of TMT, which first ensure strong work hardening of the processed material due to deformation at low temperatures and then its ultra-fast contact electropulse heating up to a specified temperature, were considered. A multi-level analysis of the metals structure evolution due to TMT was carried out using modern methods of scanning electron microscopy and X-ray diffractometry, recording a wide range of its linear and angular parameters. The kinetics and nature of the processes of the metals structure evolution under cryogenic rolling and EPT, their driving forces and controlling factors, as well as general patterns and temperature intervals of activation of the deformation structure recovery and recrystallization influenced by an electric pulse are identified and discussed. Based on the results of the analysis of the structural and mechanical behaviour of metals, it was concluded that the combination of severe plastic cryogenic deformation and a single-step treatment with ultrashort alternating current pulses is an effective way to obtain semi-finished products with controlled parameters of their structure and properties, including high-strength ultrafine-grain rolled products. At that the phenomenology and nature of the strengthening/softening of metals during cryogenic rolling and subsequent electropulsing are similar to those observed under cold rolling and furnace annealing.

Effect of stocking density on the growth, body composition, and blood parameters of cage-reared Gangetic mystus catfish (Mystus cavasius)

Suitable stocking density of Gulsa tengra (Mystus cavasius) was observed by measuring growth performance, production, and survival in nylon net cages for 120 days in Chalan Beel floodplain ecosystem. Fry of Gulsha tengra (5.55 ± 0.49 g in weight) were stocked into 6 × 3 × 2-m (36 m3) floating net cages with treatments: T1-50, T2-100, T3-150, and T4-200 fry/m3 (in triplicates). The stocked fry was fed twice daily with commercial floating pellet containing 32 % protein at the rate of 5 % /fish body weight during the first 2 months and then reduced to 3 % for the next 2 months. The highest weight gain was observed in the lowest density treatment, T1 (18.70 ± 1.37 g) and the lowest (8.66 ± 0.99 g) in highest density treatment, T4 (all tests for significance were performed at a 5 % level). The rate of survival varied from 86.6 % and 95.8 %, with T1 resulting in the significantly highest survival. A better feed conversion ratio was also observed in T1 (1.75 ± 0.26). Significantly higher protein (16.86 ± 0.36) and fat (2.78 ± 0.02) contents were recorded in the fish body composition in T1. Water quality parameters (temperature: 26.0 ± 1.0 °C, pH: 7.2 ± 0.2, DO: 6.4 ± 0.1 mg/l, NH3-N: 0.002 ± 0.001) recorded throughout the study period were within the suitable range for fish culture. The highest red (119.0 ± 4.85 ×106 µl) and white blood cell (233.2 ± 16.02 ×103 µl), hemoglobin (5.65 ± 0.30 g/dl), total protein (5.50 ± 0.03 g/dl), albumin (1.82 ± 0.06 g/dl), and globulin (3.65 ± 0.15 g/dl) were also observed in T1 indicating optimum condition. Total and net production per cage were the highest in T1 with approximately 50 % increase (88.31 ± 6.72 and 59.27 ± 5.79 kg, respectively) compared to T4. The net income and benefit–cost ratio was increased by approximately 42 % and 30 %, respectively, in T1. Thus, this study recommended an optimal stocking density of 50 fish/m3 for Gulsha tengra to achieve a profitable and robust yield in cage culture.

Higher sowing density of pearl millet increases productivity and water use efficiency in high evaporative demand seasons.

Pearlmillet is themain subsistence crop for smallholder farmers systemswhere it is grown at low plant density. Intensifying pearl millet cultivation could boost productivity although it may have trade-offs. Increasing planting density would indeed increase the leaf area and the related water budget, whereas a denser canopy could create a more favorable canopymicroclimate to the benefit of the water use efficiency (WUE) of the crops. The first aim of this work was to test the yield response of popular pearlmillet varieties to an increased density and to assess possible genotypic variation in this response. The second aim was to measure the water use and the WUE of the crop in different densities. To this end we designed several field and lysimetric experiments To increase the robustness of the results, these trials were carried out in India and Senegal, using two independent sets of genotypes adapted to both sites. In the field, the higher sowing density significantly increased yield in all genotypes when trials were carried out in high evaporative demand conditions. There was no genotype x density interaction in these trials, suggesting no genotypic variation in the response to density increase. The high-density treatment also decreased the vapor pressure deficit (VPD) in the canopies, both in the field and in the lysimeter experiments. In the lysimeter trials, although the higher density treatment increased water use, the resulting increase in biomass was proportionally higher, hence increasingWUE of the crops in all genotypes under high density. The increase in yield under high density was closely related to the increase in WUE, although this link was more tight in the high- than in the low evaporative demand seasons. This confirmed a strong environmental effect on the response to density of all genotypes tested. Although they did not open a scope for breeding density tolerant cultivars, these results highlight the possibility to improve pearl millet yield by increasing the density, targeting specifically areas facing high evaporative demand.

Using mulching to reduce soil surface temperature to facilitate grass production

Ecosystems in semi-arid and arid Southern Africa experience high temperatures which translate to extremely hot soil surface temperatures. High soil surface temperatures lead to a decrease in seed germination and consequently less plant cover in these areas. To facilitate maintenance of optimum plant cover, soil surface temperature should be moderated with appropriate mitigation techniques. Temperature variations in low (kg.0.5 m−3) and high density (1 kg m−3) brush packing treatments were compared to bare soil. We also measured the grass productivity (g.m−2) against the effect of temperature in the three treatments. iButtons® were used to log soil surface temperature every hour for seven months. Daily and nightly temperatures of the hottest months were compared amongst the three treatments. Mid-day temperatures, corresponding to peak heat stress were also compared between the three treatments. There was a significant difference (p < 0.01) in soil surface temperature between the three treatments. The high density treatment was the most buffered against temperature variation, when compared to the bare soil. Grass production was generally higher in the high density treatment. Productivity can be increased by mulching the soil with brush packing as this will improve soil surface conditions such as moderating abrupt changes in temperatures to assist plant growth.

Effects of the density of extruded pellets on starch digestion kinetics, rumen fermentation, fiber digestibilityand enteric methane production in dairy cows.

Dynamics of starch digestion in dairy cows fed extruded pellets differing in physical functional properties were investigated by measuring starch digestibility, post-prandial rumen fermentation patterns, and post-prandial duodenal starch appearance. Additionally, starch digestion effects on neutral detergent fiber (NDF) digestibility and methane (CH4 ) emission were studied. Pure barley was extruded to produce three treatments having pellets of either low-density (LD), medium-density (MD)or high-density (HD). The experiment was conducted in a 3 × 3 Latin square design using three lactating Danish Holstein cows fitted with ruminal, duodenaland ileal cannulas. After the allocation of experimental concentrate directly into the rumen through the rumen cannula, cows were fed a basal diet low in starch. Eight samples were collected on equal time intervals (9 h) from duodenal digesta, ileal digestaand feces (grab sample) to determine digestibility. For post-prandial rumen fermentation patterns, four sample sets of rumen dorsal, medialand ventral fluid were taken from each cow, whereas for post-prandial duodenal starch appearance, 14 samples of duodenal chyme were obtained from each cow relative to morning feeding of experimental concentrate at 07:00 h. Ruminal, small intestinal, hindgutand total tract digestibility of starch did not differ among treatments. Similarly, NDF digestibility and CH4 emission also remained unaffected by treatments. However, compared with the LD and MD treatments, the HD treatment showed higher acetate: propionate ratio at all positions in the rumen and a higher post-prandial duodenal starch appearance. This indicates lower ruminal starch degradation (RSD) and higher starch flow into the small intestine for HD treatment. In conclusion, the current study indicates that pellets' physical properties can manipulate RSD, where pellets with high densityand fluid stability can partly shift starch digestion from the rumen to the small intestine. Indeed, further investigations are needed.

Phenotypic and Differential Gene Expression Analyses of Phase Transition in Oedaleus asiaticus under High-Density Population Stress.

The high-density-dependent phase change from solitary to gregarious individuals in locusts is a typical example of phenotypic plasticity. However, the underlying molecular mechanism is not clear. In this study, first, Oedaleus asiaticus were treated with high-density population stress and then analyzed by Illumina sequencing on days 1, 3, 5, and 7 of the body color change to identify the stage-specific differentially expressed genes (DEGs). The KEGG pathway enrichment analysis of the identified DEGs revealed their role in metabolic pathways. Furthermore, the expression patterns of the nine key DEGs were studied in detail; this showed that the material change in locusts began on the third day of the high-density treatment, with the number of DEGs being the largest, indicating the importance of this period in the phase transition. In addition, the phenotypic change involved several key genes of important regulatory pathways, possibly working in a complex network. Phenotypic plasticity in locusts is multifactorial, involving multilevel material network interactions. This study improves the mechanistic understanding of phenotypic variation in insects at the genetic level.

Benthivorous fish cause a shift from a clear water state established by combining​ phosphorus immobilization and submerged macrophytes to a turbid state: A mesocosm study

Both chemical phosphorus (P) immobilization and submerged macrophytes are widely used in lake restorations to reduce internal phosphorus loading. Their combined effects seem much stronger than used alone. However, benthivorous fish populations recover fast and they may thus counteract the restoration effects. We conducted a mesocosm experiment with three densities of crucian carp ( Carassius auratus gibelio ) to study the effects of benthivorous fish on the combined effects of lanthanum (La) modified bentonite and submerged macrophyte Vallisneria denseserrulata in lake restoration: control (fish-free), low-density (45 g m −2 ) and high-density (83 g m −2 ). Crucian carp increased the concentrations of total phosphorus, total nitrogen, total suspended solids, and chlorophyll a and deteriorated the light climate in the water column compared with the controls. The porewater soluble reactive phosphorus concentrations in the deep sediment were two times higher in the high-density treatment than in the control group and the low-density treatment. Crucian carp increased the mobile phosphorus (mainly the NaOH-OP) in the 0–2 cm sediment, likely due to the dilution of La in the surface sediment as caused by accelerated downward transportation of La, and at the same time La-bound P (part of the HCl-P fraction) was mixed deeper into the sediment with increasing fish density. In the high-density mesocosms, plant biomass and density were reduced by 37% and 51%, respectively, which is another possible mechanism for the water quality deterioration. We conclude that it is important to control benthivorous fish when conducting lake restoration by combining phosphorus immobilization and submerged macrophytes. • Benthivorous fish dampened the combined effects of Phoslock® and macrophytes. • High-density benthivorous fish increased porewater SRP concentrations. • Benthivorous fish increased the mobile P (mainly NaOH-OP) in the surface sediment. • Benthivorous fish hampered the growth of submerged macrophytes.

Alloying regulation mechanism toward microstructure evolution of Sn-bi-based solder joint under current stress

Sn–Bi-based solder alloys have triggered substantial concern in development of low-temperature interconnecting materials of multi-level packaging electronic devices. However, with the high-density current treatment, dramatic atom migration occurs in Sn–Bi-based solder joint, which accelerates the evolution of solder joint microstructure, including the aggregation of Bi phase and the excessive growth of interfacial intermetallic compound (IMC). In this work, Sb element shows a unique influence mechanism on the electromigration (EM) resistance of Sn-Bi-based solder joint. Doped Sb in Sn58Bi-1Sb (SB-Sb) solder massive precipitate as Sn-Sb and Bi-Sb nano precipitations under current stress. These nano precipitates show the ability to capture the migrating atoms, inhibit the migration of Bi atoms and Sn atoms, and enhance the EM resistance of solder joint. Importantly, Bi twin crystal structure is observed in Sn-Bi-Sb solder for the first time. The variation of twins' phase orientations in different positions of solder joint is associated with atomic migration paths induced by the current stress and would eliminate the overgrowth of the Bi rich phase and IMCs. The presented study provides the valuable insights into the regulates mechanism of alloy elements on atom migration in Sn-Bi-based solder joint.

Plant density effects on quinoa yield, leaf anatomy, ultrastructure and gas exchange

AbstractTo study the impact of plant density onChenopodium quinoa(c.v. CICA-17) achene yield and its relationship with morphology, leaf anatomy and gas exchange in the absence of water stress, field trials were conducted at 1995 m asl in Northwestern Argentina. Two plant densities were evaluated; low density (LD) 7.2 plants/m (120 240 pl/ha) and high density (HD) 27.9 plants/m (465 930 pl/ha). HD treatment caused light competition, inducing morphological and anatomical changes in Quinoa plants. Plants grown under HD conditions showed decreases in plant height and stem diameter, lower stomatal dimensions and densities, and thinner leaf blades. Compensation strategies such as increases in specific leaf area and a higher number chloroplasts per palisade cell were observed, nevertheless these changes did not fully compensate C absorption and gas exchange limitations, therefore limiting the uptake of N and P and resulting in a 53.2% lower yield of HD compared to LD. Considering the ability of quinoa plants to change its morphology and anatomy, further studies with intermediate plant densities are necessary in order to determine if it is possible to achieve higher yields and to increase the efficiency in the use of the resources.

Effects of Contaminated Soil on the Survival and Growth Performance of European (Populus tremula L.) and Hybrid Aspen (Populus tremula L. × Populus tremuloides Michx.) Clones Based on Stand Density.

This study was conducted to assess the survival rates, growth, and chlorophyll fluorescence (Fv/Fm) of four hybrid aspen (14, 191, 27, 291) and two European aspen (R3 and R4) clones cultivated in creosote- and diesel oil-contaminated soil treatments under three different plant densities: one plant per pot (low density), two plants per pot (medium density), and six plants per pot (high density) over a period of two years and three months. Evaluating the survival, growth, and Fv/Fm values of different plants is a prerequisite for phytoremediation to remediate polluted soils for ecological restoration and soil health. The results revealed that contaminated soils affected all plants’ survival rates and growth. However, plants grown in the creosote-contaminated soil displayed a 99% survival rate, whereas plants cultivated in the diesel-contaminated soil showed a 22–59% survival rate. Low plant density resulted in a higher survival rate and growth than in the other two density treatments. In contrast, the medium- and high-density treatments did not affect the plant survival rate and growth to a greater extent, particularly in contaminated soil treatments. The effects of clonal variation on the survival rate, growth, and Fv/Fm values were evident in all treatments. The results suggested that hybrid aspen clones 14 and 291, and European aspen clone R3 were suitable candidates for the phytoremediation experiment, as they demonstrated reasonable survival rates, growth, and Fv/Fm values across all treatments. A superior survival rate for clone 291, height and diameter growth, and stem dry biomass production for clone 14 were observed in all soil treatments. Overall, a reasonable survival rate (~75%) and Fv/Fm value (>0.75) for all plants in all treatments, indicating European aspen and hybrid aspen have considerable potential for phytoremediation experiments. As the experiment was set up for a limited period, this study deserves further research to verify the growth potential of different hybrid aspen and European aspen clones in different soil and density treatment for the effective phytoremediation process to remediate the contaminated soil.

The Effects of Providing Outdoor Access to Broilers in the Tropics on Their Behaviour and Stress Responses.

Simple SummaryThe effects of outdoor access for broilers have been tested under temperate conditions, where free-range systems have begun to be widely used. However, under tropical conditions, where the birds may be heat-stressed outside, the benefits of providing a free-range area may be less evident. We compared whether access to an outdoor area improved behavior and several physiological welfare indicators of broilers at two stocking densities in a tropical environment. There were no major effects of outdoor access on broiler behavior, except that resting was reduced by providing outdoor access to older birds and those at low stocking densities inside. However, outdoor access increased heterophil numbers in summer, but not in winter, which may indicate heat stress. We concluded that the effects of outdoor access on the welfare of broilers in the tropics are dependent on season and stocking density.The effects of outdoor access, stocking density, and age on broiler behavior, stress, and health indicators in a tropical climate were assessed over two seasons, winter and summer. Two hundred and forty Cobb500 male chickens were allocated to one of four treatments, with six replicates of ten birds in each: low stocking density indoors with outdoor access (LO); high stocking density indoors with outdoor access (HO); low stocking density indoors without outdoor access (LI); and high stocking density indoors without outdoor access (HI). Scan sampling was used to record their behavior both indoors and outdoors. At 28 and 42 days old, blood samples were obtained to determine the heterophil to lymphocyte (H/L) ratio. At 42 days old, chickens were culled and inspected for footpad dermatitis (FPD), and bone quality was examined. Their spleens and bursas of Fabricius were collected and weighed, relative to carcass weight (RW). A factorial analysis was used to test the effects of season (winter or summer), outdoor access (with or without), stocking density (low: 5 animals/m2 or high: 10 animals/m2), and age (28 or 42 days) on the behavior and stress and health indicators. There were no major effects of providing outdoor access on behavior, except that resting was reduced by providing outdoor access to older birds and those at low stocking densities inside. Resting was also greater in indoor and high-density treatments during winter. The bursa of Fabricius was heavier in summer in outdoor birds. The tibia bones were shorter in the outdoor birds. Heterophil numbers were greater in the outdoor treatments in summer but not in winter. These results indicate that outdoor access can increase activity in some situations, and potentially increase bone strength, but it may also increase the risk of stress, particularly heat stress in summer.

Health risk assessment of gaseous elemental mercury (GEM) in Mexico City.

Emissions of gaseous elemental mercury (GEM or Hg0) from different sources in urban areas are important subjects for environmental investigations. In this study, atmospheric Hg measurements were conducted to investigate air pollution in the urban environment by carrying out several mobile surveys in Mexico City. This work presents atmospheric concentrations of GEM in terms of diurnal variation trends and comparisons with criteria for pollutant concentrations such as CO, SO2, NO2, PM2.5, and PM10. The concentration of GEM was measured during the pre-rainy period by using a high-resolution active air sampler, the Lumex RA 915 M mercury analyzer. In comparison with those for other cities worldwide, the GEM concentrations were similar or slightly elevated, and they ranged from 0.20 to 30.23 ng m−3. However, the GEM concentration was significantly lower than those in contaminated areas, such as fluorescent lamp factory locations and gold mining zones. The GEM concentrations recorded in Mexico City did not exceed the WHO atmospheric limit of 200 ng m−3. We performed statistical correlation analysis which suggests equivalent sources between Hg and other atmospheric pollutants, mainly NO2 and SO2, emitted from urban combustion and industrial plants. The atmospheric Hg emissions are basically controlled by sunlight radiation, as well as having a direct relationship with meteorological parameters. The area of the city studied herein is characterized by high traffic density, cement production, and municipal solid waste (MSW) treatment, which constantly release GEM into the atmosphere. In this study, we included the simulation with the HYSPLIT dispersion model from three potential areas of GEM release. Emissions from industrial corridors and volcanic plumes localized outside the urban area contribute to the pollution of Mexico City and mainly affect the northern area during specific periods and climate conditions. Using the USEPA model, we assessed the human health risk resulting from exposure to inhaled GEM among residents of Mexico City. The results of the health risk assessment indicated no significant noncarcinogenic risk (hazard quotient (HQ) < 1) or consequent adverse effects for children and adults living in the sampling area over the study period. GEM emissions inventory data is necessary to improve our knowledge about the Hg contribution and effect in urban megacity areas with the objective to develop public safe policy and implementing the Minamata Convention.Supplementary informationThe online version contains supplementary material available at 10.1007/s10661-022-10107-7.