The Appearance of a “Fresh” Surface on 596 Scheila as a Consequence of the 2010 Impact Event

Dust emission was detected on main-belt asteroid 596 Scheila in 2010 December and was attributed to the collision of a few-tens-of-meters projectile on the surface of the asteroid. In such an impact, the ejected material from the collided body is expected to mainly come from its fresh, unweathered subsurface. Therefore, it is expected that the surface of 596 was partially or entirely refreshed during the 2010 impact. By combining spectra of 596 from the literature and our own observations, we show that the 2010 impact event resulted in a significant slope change in the near-infrared (0.8–2.5 μm) spectrum of the asteroid, from moderately red (T type) before the impact to red (D type) after the impact. This provides evidence that red carbonaceous asteroids become less red with time due to space weathering, in agreement with predictions derived from laboratory experiments on the primitive Tagish Lake meteorite, which is spectrally similar to 596. This discovery provides the very first telescopic confirmation of the expected weathering trend of asteroids spectrally analog to Tagish Lake and/or anhydrous chondritic porous interplanetary dust particles. Our results also suggest that the population of implanted objects from the outer solar system is much larger than previously estimated in the main belt, but many of these objects are hidden below their space-weathered surfaces.

Controls on the epilimnetic phosphorus concentration in small temperate lakes

Phosphorus (P) is one of the key limiting nutrients for algal growth in most fresh surface waters. Understanding the determinants of P accumulation in the water column of lakes of...

[FE1091] Regulations Governing the Usage of Reclaimed Water as an Alternative Water Source for Agricultural Irrigation in Florida

Fresh water is becoming increasing scarce as the world population grows rapidly. Reclaimed water from alternative sources can be used to help offset the demand for fresh surface water and groundwater in agriculture. To ensure that pathogenic or trace chemical constituents in reclaimed water do not pose a threat to human health and the environment, state and federal governments impose regulations governing reclaimed water use. This fact sheet documents the rules and regulations governing the use of reclaimed water from alternative water sources in Florida agriculture. Target audiences include growers exploring alternative water use for agriculture, non-core professionals, core professionals, and the public.

Rethinking water and crops management in the irrigated district of Diyar-Al-Hujjej (Tunisia)

In Diyar-Al-Hujjej irrigated area, aquifer’s over-exploitation, sea intrusion and abandonment of irrigated areas and wells were took place. A yield decrease for all crops was observed. Average aquifer water electrical conductivity (EC) jumps from 4 dS/m to 6.6 dS/m between 1969 and 2017. A fresh surface water transfer over more than 100 km was launched in 1998 to safeguard this irrigated area but this fresh water supply is not stable, it varies from one year to another (about 1,900,000 m3 in 2015 and only 60,000 m3 in 2018) while annual cops water requirements of the perimeter is about 2,500,000 m3. An adaptation by farmers to this new situation of saline and water stress was observed. The follow-up surveys of the farmer’s practices showed that: (i) new crops with high added-value grown during the rainy season were introduced in association with dry season crops (strawberry-pepper association), (ii) rainfed crops, fallow and water blending are common practices, and (iii) growing of rainy season crops in the aim to reduce water supply. The instability of fresh surface water volume transferred constitutes the main threat for this perimeter. The use of aquifer salt water must be stopped; it is the cause of the large quantities of salts supplied (over 13,000 kg / ha) and also of the low annual net income achieved. Net revenue was less than 2,000 US $/ha under salt water and reached even 8,000 US $/ha when sufficient surface water is available. An agrarian reform policy must be applied for this perimeter; only crops whose water requirements are partially met by rain should be grown. Introduction of another more sustainable water source should be initiated (as desalination) even at private farm level.

The climate sensitivity of northern Greenland fjords is amplified through sea-ice damming

Record-high air temperatures were observed over Greenland in the summer of 2019 and melting of the northern Greenland Ice Sheet was particularly extensive. Here we show, through direct measurements, that near surface ocean temperatures in Sherard Osborn Fjord, northern Greenland, reached 4 °C in August 2019, while in the neighboring Petermann Fjord, they never exceeded 0 °C. We show that this disparity in temperature between the two fjords occurred because thick multi-year sea ice at the entrance of Sherard Osborn Fjord trapped the surface waters inside the fjord, which led to the formation of a warm and fresh surface layer. These results suggest that the presence of multi-year sea ice increases the sensitivity of Greenland fjords abutting the Arctic Ocean to climate warming, with potential consequences for the long-term stability of the northern sector of the Greenland Ice Sheet.

Effects of Temperature and pH on the Egg Production and Hatching Success of a Common Korean Copepod

The recent accelerated ocean acidification and global warming caused by increased atmospheric carbon dioxide may have an impact on the physiology and ecology of marine animals. This study was conducted to determine the egg production rate (EPR) and hatching success (EHS) of Acartia ohtsukai in response to the combined effects of an increase in temperature and a lower pH. Acartiaohtsukai with fresh surface seawater were collected in the northwestern Yeoja Bay of Korea in September 2017. The temperature and pH conditions applied included two different pH levels (representing the present: 7.9 and the future: 7.6) and three temperature values (26 °C, 28 °C, and 30 °C). In the pH 7.9, EPR significantly increased with increased temperature, but in pH 7.6, it significantly decreased as the temperature increased. EHS was lower in pH 7.6 than in pH 7.9. These results suggest that changes in the marine environment due to global warming and ocean acidification may affect Acartia populations and cause overall fluctuations in copepods of the genus Acartia.

Occurrence of a Likely Tuff Bed between the Middle and Upper Siwaliks, Taunsa area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan

A likely tuff bed lies along the gradational contact of the Middle and Upper Siwaliks in eastern Sulaiman Range, Taunsa area of Dera Ghazi Khan district, Pakistan. This tuffaceous unit is 0.5–3 m thick and extends for 10 km along the north-south strike in the eastern limb of the Zindapir anticline. It is greyish white to white on fresh surface, fine-grained to silty at the bottom and clayey at the top and thus shows a fining upward grain-size grading. The lower part of the ash bed shows a prominent lamination defined by megascopically visible abundant biotite, while the central and upper parts are so fine-grained that the individual minerals cannot be seen in hand sample. Unlike the lower well-laminated part, the central and upper parts are crudely laminated to apparently massive. The bulk samples analysed with X-ray diffraction consist of quartz, feldspar (plagioclase), biotite, clays, calcite and some ore mineral likely spinel, while the clay-size fractions contain illite, chlorite, biotite and probably their mixed-layered varieties. The colour, texture, presence of abundant biotite and stratigraphic position of the Taunsa tuff correlate with those reported from Potwar plateau and from Kashmir basin. However, the apparent absence of smectite from the XRD pattern makes the Taunsa ash bed different from both Potwar and Kashmir tuffs. The present stratigraphic position of the tuff bed corresponds to shallow diagenetic zone, while the absence of smectite in the tuff and crystallinity of illite suggest that the tuff is probably derived upon reworking from a deeper diagenetic zone belonging to a lower stratigraphic level. The Eocene or other older pre-Siwalik units in Pakistan may have or had some primary ashfall deposits as reported in the northwestern Himalayas of India. This older volcanic ash may have been reworked to its present site of occurrence along the gradational contact of the Middle and the Upper Siwaliks in Taunsa area of Dera Ghazi Khan. However, the primary source of the Taunsa tuff may belong more likely to Chagai arc in Pakistan than to Dacht-e-Nawar volcanic complex in Afghanistan.

Occurrence of a Likely Tuff Bed between the Middle and Upper Siwaliks, Taunsa area, Dera Ghazi Khan, Eastern Sulaiman Range, Pakistan

A likely tuff bed lies along the gradational contact of the Middle and Upper Siwaliks in eastern Sulaiman Range, Taunsa area of Dera Ghazi Khan district, Pakistan. This tuffaceous unit is 0.5–3 m thick and extends for 10 km along the north-south strike in the eastern limb of the Zindapir anticline. It is greyish white to white on fresh surface, fine-grained to silty at the bottom and clayey at the top and thus shows a fining upward grain-size grading. The lower part of the ash bed shows a prominent lamination defined by megascopically visible abundant biotite, while the central and upper parts are so fine-grained that the individual minerals cannot be seen in hand sample. Unlike the lower well-laminated part, the central and upper parts are crudely laminated to apparently massive. The bulk samples analysed with X-ray diffraction consist of quartz, feldspar (plagioclase), biotite, clays, calcite and some ore mineral likely spinel, while the clay-size fractions contain illite, chlorite, biotite and probably their mixed-layered varieties. The colour, texture, presence of abundant biotite and stratigraphic position of the Taunsa tuff correlate with those reported from Potwar plateau and from Kashmir basin. However, the apparent absence of smectite from the XRD pattern makes the Taunsa ash bed different from both Potwar and Kashmir tuffs. The present stratigraphic position of the tuff bed corresponds to shallow diagenetic zone, while the absence of smectite in the tuff and crystallinity of illite suggest that the tuff is probably derived upon reworking from a deeper diagenetic zone belonging to a lower stratigraphic level. The Eocene or other older pre-Siwalik units in Pakistan may have or had some primary ashfall deposits as reported in the northwestern Himalayas of India. This older volcanic ash may have been reworked to its present site of occurrence along the gradational contact of the Middle and the Upper Siwaliks in Taunsa area of Dera Ghazi Khan. However, the primary source of the Taunsa tuff may belong more likely to Chagai arc in Pakistan than to Dacht-e-Nawar volcanic complex in Afghanistan.