Manipulating nutrient limitation using modified local soils: A case study at Lake Taihu (China)

The effect of geo-engineering materials of chitosan modified local soil (MLS) on nutrient limitation was studied in comparable whole ponds in Lake Taihu in October 2013. After 20 kg MLS were sprayed onto the whole water pond (400 m2), the chlorophyll-a (Chl-a) concentration was decreased from 42 to 18 µg L-1 within 2 hours and remained below 20 µg L-1 in the following 15 months, while the average Chl-a was 36 µg L-1 in the control pond throughout the experiment. In situ nutrient addition bioassay experiments indicated that the nutrient limitation was shifted from nitrogen (N) and phosphorus (P) co-limitation to P limitation after MLS treatment from October 2013 to March 2014 compared to the control pond. In the cyanobacterial bloom season of June 2014, N and P co-limitation remained and N was the primary limiting nutrient and P was a secondary one in the control pond, because phytoplankton biomass (as Chl-a) showed significant increase by N addition and further increase by N+P additions, while both N and P became the limiting nutrient for phytoplankton growth on the basis that only combining N and P additions showed significant Chl-a stimulation in the treatment pond. In the next summer (June 2014), a cyanobacteria-dominated state still remained in the control pond but chlorophytes, bacillariophytes and cyanophytes distributed equally and submerged vegetation was largely restored in the treatment pond. Meanwhile, the upper limiting concentration of DIN was enhanced from 0.8 to 1.5 mg L-1 and SRP from 0.1 to 0.3 mg L-1 compared to the control pond. This study indicates that nutrient limitation can be manipulated by using MLS technology

Quantifying methane emissions from rice fields in the Taihu Lake region, China by coupling a detailed soil database with biogeochemical model

As China has approximately 22% of the world's rice paddies, the regional quantification of CH<sub>4</sub> emissions from these paddies is important in determining their contribution to the global greenhouse gas effect. This paper reports the use of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying CH<sub>4</sub> emissions from rice fields in the Taihu Lake region of China. For this application, the DNDC model was linked to a 1:50 000 soil database derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980s–1990s. The simulated results showed that the 2.3 Mha of paddy rice fields in the Taihu Lake region emitted the equivalent of 5.7 Tg C from 1982–2000, with the average CH<sub>4</sub> flux ranging from 114 to 138 kg C ha<sup>−1</sup> y<sup>−1</sup>. As for soil subgroups, the highest emission rate (660 kg C ha<sup>−1</sup> y<sup>−1</sup>) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest emission rate (91 kg C ha<sup>−1</sup> y<sup>−1</sup>) was associated with degleyed paddy soils accounting for about 18% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a CH<sub>4</sub> flux of 106 kg C ha<sup>−1</sup> y<sup>−1</sup>. On a regional basis, the annual averaged CH<sub>4</sub> flux in the Taihu Lake plain soil region and alluvial plain soil region were higher than that in the low mountainous and hilly soil region and the polder soil region. The model simulation was conducted with two databases using polygons or counties as the basic units. The county-based database contained soil information coarser than the polygon system built based on the 1:50 000 soil database. The modeled results with the two databases found similar spatial patterns of CH<sub>4</sub> emissions in the Taihu Lake region. However, discrepancies exist between the results from the two methods. The total CH<sub>4</sub> emissions generated from the polygon-based database is 2.6 times the minimum CH<sub>4</sub> emissions generated from the county-based database, and is 0.98 times the maximum CH<sub>4</sub> emissions generated from the county-based database. The average value of the relative deviation ranged from −20% to 98% for most counties, which indicates that a more precise soil database is necessary to better simulate CH<sub>4</sub> emissions from rice fields in the Taihu Lake region using the DNDC model

Phosphate capture by ultrathin MgAl layered double hydroxide nanoparticles

Capture of phosphorus from runoff and wastewater is of high priority in order to reclaim phosphorus for food security and to prevent water pollution. Here we report an environmentally friendly method to synthesize ultrathin MgAl layered double hydroxide (LDH) nanoparticles for phosphorus adsorption. Fast co-precipitation of magnesium and aluminum at 25-80 °C in the presence of urea resulted in the desired LDH with variable admixtures of amorphous aluminum hydroxide (16-38%) quantified from solid state 27Al MAS NMR. Freshly synthesized particles appeared as exfoliated single layers that upon drying stacked to form particles with thickness of 3 to 5 nm (four to six LDH layers) and lateral sizes of ~30 nm, as seen by XRD, SEM, TEM, and AFM. Phosphate adsorption on LDH nanoparticles synthesized at room temperature (LDHnsU25) was very fast and reaction reached equilibrium within 15 min at pH 8.5. The freeze-dried LDHns-U25 nanoparticles exhibited phosphate sorption capacity of 98±15 mg P g-1, which is 55% higher than conventional LDH. Phosphate was bound to LDH electrostatically and via inner-sphere surface complexation as evidenced from a combination of 31P MAS NMR spectroscopy, surface potential measurements, IR spectroscopy, and ionic strength effects on phosphate sorption. This study demonstrates that urea-facilitated synthesis of LDH nanoparticles provides fast and high capacity phosphate sorbents with potentials for phosphate recovery from waste waters

Characteristic Aroma Compounds in Two New Vitis vinifera Cultivars (Table Grapes) and Impact of Vintage and Greenhouse Cultivation

‘Zaoheibao’ (a red tetraploid hybrid) and ‘Wuhecuibao’ (a white triploid hybrid) grapes have beenobtained from Guibao♀ (diploid, Vitis vinifera) × Zaomeigui♂ (diploid, V. vinifera) and Guibao♀ (diploid,V. vinifera) × Wuhebaijixin♂ (triploid, V. vinifera) respectively. Aroma characterisation of the twonew table grape cultivars was firstly done by the investigation of volatile compounds. The influence ofgreenhouse cultivation and vintage on berry aroma was studied as well. The results showed that linalool,decanal, β-damascenone, hexanal and (E)-2-hexenal were the main volatile compounds of the two cultivars,which meant that the floral, fruity and sweet odour were prominent, followed by the herbaceous aroma.Greenhouse cultivation enhanced herbaceous odour in both ‘Wuhecuibao’ and ‘Zaoheibao’ berries,and reduced the floral aroma, contributed mainly by β-damascenone, in ‘Wuhecuibao’, and the sweetaroma, represented mainly by linalool, in ‘Zaoheibao’. The concentrations of the main aroma compoundswere greatly affected by vintage and the intensity of sensorial perception was correspondingly changed,but varietal odour attributes were not significantly altered. These results will not only help promote thecultivation and popularisation of these cultivars, but also will provide valuable data for the use of thesecultivars in future breeding

Cadmium, lead, and arsenic contamination in paddy soils of a mining area and their exposure effects on human HEPG2 and keratinocyte cell-lines

A mining district in south China shows significant metal(loid) contamination in paddy fields. In the soils, average Pb, Cd and As concentrations were 460.1, 11.7 and 35.1 mg kg−1 respectively, which were higher than the environmental quality standard for agricultural soils in China (GB15618-1995) and UK Clea Soil Guideline Value. The average contents of Pb, Cd and As in rice were 5.24, 1.1 and 0.7 mg kg−1 respectively, which were about 25, 4.5 or 2.5 times greater than the limit values of the maximum safe contaminant concentration standard in food of China (GB 2762-2012), and about 25, 10 or 1 times greater than the limit values of FAO/WHO standard. The elevated contents of Pb, Cd and As detected in soils around the factories, indicated that their spatial distribution was influenced by anthropogenic activity, while greater concentrations of Cd in rice appeared in the northwest region of the factories, indicating that the spatial distribution of heavy metals was also affected by natural factors. As human exposure around mining districts is mainly through oral intake of food and dermal contact, the effects of these metals on the viability and MT protein of HepG2 and KERTr cells were investigated. The cell viability decreased with increasing metal concentrations. Co-exposure to heavy metals (Pb+Cd) increased the metals (Pb or Cd)-mediated MT protein induction in both human HepG2 and KERTr cells. Increased levels of MT protein will lead to greater risk of carcinogenic manifestations, and it is likely that chronic exposure to metals may increase the risk to human health. Nevertheless, when co-exposure to two or more metals occur (such as As+Pb), they may have an antagonistic effect thus reducing the toxic effects of each other

Vortex Images and q-Elementary Functions

In the present paper problem of vortex images in annular domain between two coaxial cylinders is solved by the q-elementary functions. We show that all images are determined completely as poles of the q-logarithmic function, where dimensionless parameter $q = r^2_2/r^2_1$ is given by square ratio of the cylinder radii. Resulting solution for the complex potential is represented in terms of the Jackson q-exponential function. By composing pairs of q-exponents to the first Jacobi theta function and conformal mapping to a rectangular domain we link our solution with result of Johnson and McDonald. We found that one vortex cannot remain at rest except at the geometric mean distance, but must orbit the cylinders with constant angular velocity related to q-harmonic series. Vortex images in two particular geometries in the $q \to \infty$ limit are studied.Comment: 17 page

Enhanced chitosan flocculation for microalgae harvesting using electrolysis

Harvesting microalgae from water and wastewater streams is important for both environmental remediation and recycling of both algal material and associated nutrients. Chitosan is widely used as an environmentally friendly flocculant in this process. Charge neutralization is a key operating mechanism for chitosan flocculation in microalgae harvesting. Alkaline conditions have been conventionally used to modify chitosan to create an increase in charge neutralization. However, it is often difficult to operate the chemical processes needed for this method, which also pose environmental risks. In this study, a simple and environmentally safe method to increase chitosan charge neutralization using electrolysis was proposed and tested in the harvest of microalgae. The results demonstrate that the electrolysis produced a charging effect on the chitosan and exhibited a significant positive relationship with current intensity (r2 = 0.91, P < 0.05). When the electrolysis was operated at 0.2, 0.4, and 0.6 A, the charge neutralization of chitosan increased by 2.05, 4.99, and 10.86 mV/mg, respectively. As the charge neutralization increased, chitosan flocculation yielded a higher microalgae harvesting efficiency at a lower chitosan dosage. One of the possible mechanisms for the increased charge neutralization ability is the deacetylation of the acetyl groups caused by electrolysis. This idea needs further study that includes identifying a chitosan structure change. This study proposed a novel strategy for modifying chitosan and its derivatives for enhancing flocculation in microalgae-based engineering