Natural and Post-Urbanization Signatures of Hypoxia in Two Basins of Puget Sound: Historical Reconstruction of Redox Sensitive Metals and Organic Matter Inputs

Hypoxia has been observed in Hood Canal, Puget Sound, WA, USA since the 1970s. Four long sediment cores were collected in 2005 and age-dated to resolve natural and post-urbanization signatures of hypoxia and organic matter (OM) sources in two contrasting basins of Puget Sound: Main Basin and Hood Canal. Paleoecological indicators used for sediment reconstructions included pollen, stable carbon and nitrogen isotopes (??¹³C and ??¹⁵N), biomarkers of terrestrial OM (TOM), biogenic silica (BSi), and redox-sensitive metals (RSM). The sedimentary reconstructions illustrated a gradient in RSM enrichment factors as Hood Canal > Main Basin, southern > northern cores, and pre-1900s > 1900?C2005. The urbanization of Puget Sound watersheds during the 1900s was reflected as shifts in all the paleoecological signatures. Pollen distributions shifted from predominantly old growth conifer to successional alder, dominant OM signatures recorded a decrease in the proportion of marine OM (MOM) concomitant with an increase in the proportion of TOM, and the weight % of BSi decreased. However, these shifts were not coincidental with an overall increase in the enrichment of RSM or ??¹⁵N signatures indicative of cultural eutrophication. The increased percentage of TOM was independently verified by both the elemental ratios and lignin yields. In addition, isotopic signatures, BSi, and RSMs all suggest that OM shifts may be due to a reduction in primary productivity rather than an increase in OM regeneration in the water column or at the sediment/water interface. Therefore, the reconstructions suggested the Hood Canal has been under a more oxygenated ??stance?? during the twentieth century compared to prior periods. However, these 2005 cores and their resolutions do not encompass the period of high resolution water column measurements that showed short-lived hypoxia events and fish kills in Hood Canal during the early twenty-first century. The decoupling between the increased watershed-scale anthropogenic alterations recorded in the OM signatures and the relatively depleted RSM during the twentieth century suggests that physical processes, such as deep-water ventilation, may be responsible for the historical variation in oxygen levels. Specifically, climate oscillations may influence the ventilation and/or productivity of deep water in Puget Sound and particularly their least mixed regions.     

Patterns of estuarine use by juvenile English sole (Parophrys vetulus) and Dungeness crab (Cancer magister)

Extensive trawl surveys were conducted in two large estuaries (Grays Harbor and Willapa Bay) on the Washington coast during 1983–1987, and in adjacent areas of the open coast. These surveys have shown that both English sole and Dungeness crab rely heavily on these estuaries as nursery areas, although the pattern of utilization differs substantially. Juvenile migration patterns can show substantial interannual variability and can only be delineated by concurrent surveys in both coastal and estuarine areas, conducted over a period of several years. English sole eggs and Dungeness crab larvae are released in coastal waters. Larvae of both species transform to the benthic stage in both coastal and estuarine areas, but most English sole eventually migrate into the estuaries during the first year of life, even if initial settlement is along the open coast. By the time English sole have attained a length of 55 mm (TL), most of them are found in estuaries. English sole begin emigrating from the estuaries at about 75 mm, and few remain there during the second year of life. In contrast, Dungeness crab appear to remain in the area of initial settlement throughout the first year of life. Growth is substantially faster in estuaries where 0+ crab reach a mean size of about 40 mm carapace width (CW) by September, with those off the coast are only about 14 mm CW. Juveniles remain in the area of settlement over their first winter but, in contrast to English sole, most coastal 1+ crab immigrate to estuaries to join siblings that settled there the previous year. By September of the second year, crab at about 100 mm CW emigrate to the open coast where they reach maturity. Advantages to juvenile stages that reside in estuaries are discussed in terms of accelerated growth at higher temperatures and potentially greater food supplies than found nearshore along the coast.     

Small Spatial Scale Variation in Fish Assemblage Structure in the Vicinity of the Northwestern Gulf of Mexico Hypoxic Zone

Seasonal hypoxia [dissolved oxygen (DO)?≤?2 mg?l^?1] occurs over large regions of the northwestern Gulf of Mexico continental shelf during the summer months (June–August) as a result of nutrient enrichment from the Mississippi–Atchafalaya River system. We characterized the community structure of mobile fishes and invertebrates (i.e., nekton) in and around the hypoxic zone using 3 years of bottom trawl and hydrographic data. Species richness and total abundance were lowest in anoxic waters (DO?≤?1 mg?l^?1) and increased at intermediate DO levels (2–4 mg?l^?1). Species were primarily structured as a benthic assemblage dominated by Atlantic croaker (Micropogonias undulatus) and sand and silver seatrout (Cynoscion spp.), and a pelagic assemblage dominated by Atlantic bumper (Chloroscombrus chrysurus). Of the environmental variables examined, bottom DO and distance to the edge of the hypoxic zone were most strongly correlated with assemblage structure, while temperature and depth were important in some years. Hypoxia altered the spatial distribution of both assemblages, but these effects were more severe for the benthic assemblage than for the pelagic assemblage. Brown shrimp, the primary target of the commercial shrimp trawl fishery during the summer, occurred in both assemblages, but was more abundant within the benthic assemblage. Given the similarity of the demersal nekton community described here to that taken as bycatch in the shrimp fishery, our results suggest that hypoxia-induced changes in spatial dynamics have the potential to influence harvest and bycatch interactions in and around the Gulf hypoxic zone.     

Swimming behavior of Dungeness crab,Cancer magister Dana,megalopae in still and moving water

In the Grays Harbor estuary, juvenile Dungeness crab (Cancer magister Dana) are found at higher densities in epibenthic shell deposits compared to open mud flat. Differences in predation rate between habitats have been suggested to be due to habitat preference and differential survival. Megalopae preferred shell over open space in still-water conditions. However, it is not known whether megalopae are able to select shell in flowing water since larval preference is known to differ between still and flowing water. Here we report the first experimental study of swimming behavior of Dungeness crab megalopae in a range of current velocities (0–40 cm s^?1) equivalent to natural flow in Grays Harbor estuary. Experiments were conducted in daylight using a recirculating flume. Megalopae swimming speeds ranged from 8.5 cm s^?1 (8 body lengths s^?1) in still water to 44.8 cm s^?1 (44 body lengths s^?1) at flow speeds of 40 cm s^?1, Neither swimming behavior nor sheltering behavior in shells showed any flow-related pattern. Megalopae spent a large proportion of time swimming against the current and made headway upstream against all current velocities tested. The results suggest that Dungeness crab megalopae are able to maneuver and actively search for settlement sites under current velocities found in natural habitats, including intertidal shell deposits, and support the hypothesis of active selection of shell by megalopae.     

Seismotectonic and seismological aspects of the Mostaganem (Western Algeria) May 22, 2014 (Mw 4.9) seismic event

On Thursday, 22 of May 2014, at 6 h 22 min 0.3.3 s (GMT?+?1) a moderate-sized earthquake struck the Mostaganem, Western Algeria, region. The main shock, recorded by many international and national seismological stations, was preceded by a foreshock, 3 hours before, on May 22, 2014 (Ml?=?4.1) at 3 h 57 min 41.4 s and followed by four well-felt aftershocks (M?>?3.0) that lasted about 1 year. The main shock did not cause loss of lives but serious panic among the population was reported. The main shock, however, caused cracks in walls and roofs, sometimes destroyed, the old non-engineered and precarious adobe dweller corresponding to I₀?=?VI–VII (Msk scale). We used accelerograph records to (i) determine the epicenter location (longitude?=?0.3537 E, latitude?=?35.8598 N, (ii) perform waveforms inversion to calculate the earthquake parameters. The obtained results are, respectively, the seismic moment (M₀)?=?2.71 E + 16, the Mw?=?4.9 and the focal depth?=?6 km. The obtained focal mechanism solution shows reverse faulting with small right lateral component with the following nodal plans: NP1, strike?=?193.5, dip?=?49.5, slip?=?57.6 and NP2, strike?=?57.8, dip?=?50, slip?=?122.1. On the other hand, the seismotectonic framework of the Dahra area exhibits a serie of NE-SW trending “en echelon” faulted folds that may be active as suggested by this study.     

Juvenile Winter Flounder (<Emphasis Type="Italic">Pseudopleuronectes americanus</Emphasis>) and Summer Flounder (<Emphasis Type="Italic">Paralichthys dentatus</Emphasis>) Utilization of Southern New England Nurseries: Comparisons Among Estuarine,Tidal River,and Coastal Lagoon Shallow-Water Habitats

This study evaluated the relative importance of the Narragansett Bay estuary (RI and MA, USA), and associated tidal rivers and coastal lagoons, as nurseries for juvenile winter flounder, Pseudopleuronectes americanus, and summer flounder, Paralichthys dentatus. Winter flounder (WF) and summer flounder (SF) abundance and growth were measured from May to October (2009–2013) and served as indicators for the use and quality of shallow-water habitats (water depth <1.5–3.0 m). These bioindicators were then analyzed with respect to physiochemical conditions to determine the mechanisms underlying intraspecific habitat selection. WF and SF abundances were greatest in late May and June (maximum monthly mean?=?4.9 and 0.55 flounder/m² for WF and SF, respectively) and were significantly higher in the tidal rivers relative to the bay and lagoons. Habitat-related patterns in WF and SF abundance were primarily governed by their preferences for oligohaline (0.1–5 ppt) and mesohaline (6–18 ppt) waters, but also their respective avoidance of hypoxic conditions (<4 mg DO/L) and warm water temperatures (>25 °C). Flounder habitat usage was also positively related to sediment organic content, which may be due to these substrates having sufficiently high prey densities. WF growth rates (mean?=?0.25?±?0.14 mm/day) were negatively correlated with the abundance of conspecifics, whereas SF growth (mean?=?1.39?±?0.46 mm/day) was positively related to temperature and salinity. Also, contrary to expectations, flounder occupied habitats that offered no ostensible advantage in intraspecific growth rates. WF and SF exposed to low salinities in certain rivers likely experienced increased osmoregulatory costs, thereby reducing energy for somatic growth. Low-salinity habitats, however, may benefit flounder by providing refugia from predation or reduced competition with other estuarine fishes and macroinvertebrates. Examining WF and SF abundance and growth across each species’ broader geographic distribution revealed that southern New England habitats may constitute functionally significant nurseries. These results also indicated that juvenile SF have a geographic range extending further north than previously recognized.     

Temperature Dependence of Oxygen Dynamics and Community Metabolism in a Shallow Mediterranean Macroalgal Meadow (Caulerpa prolifera)

Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. High-frequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3?mmol?O₂?m^?2?day^?1, respectively. The higher GPP and CR were calculated for the same day, when daily averaged water temperature was 28.3?°C, and resulted in a negative NEP of ?56.4?mmol?O₂?m^?2?day^?1. The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39?% °C^?1 (±0.14?% °C^?1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semi-enclosed bays.     

Petrogenesis of the Nesryin gabbroic intrusion in SW Sinai, Egypt: new contributions from mineralogy, geochemistry, Nd and Sr isotopes

The Wadi Nesryin gabbroic intrusion is part of the Neoproterozoic Pan-African basement cropping out in southern Western Sinai of Egypt. The intrusion comprises hornblende gabbro, pyroxene–hornblende gabbro, diorite and appinitic varieties. It exhibits chilled margins against the older rocks represented by fine-grained gabbro and dolerite and belongs to what is known throughout Egypt as the “younger gabbro suite”. Mineralogy, mineral chemistry and whole rock geochemistry indicate that these rocks were derived from tholeiitic magmas with minor calc-alkaline affinity. They have chemical signatures of subduction related arc rocks formed at an active convergent plate margin. They were formed by 15–30% of partial melting of a garnet lherzolite and to a minor extent of spinel-garnet lherzolite sources, modified by fluids related to a subducting slab. Pressure estimates using the amphibole geobarometer indicate that the gabbroic rocks crystallized at pressures between 2.8 and 5.6 kbar (average?=?4.3 kbar). Diorites record lower formation pressures between 1.8 and 3.7 kbar (average?=?3.0 kbar). The temperature estimates calculated by several geothermometers yielded crystallization temperatures ranging from 674°C to 961°C, with an average of about 817°C. The whole rock Rb–Sr isochron age of the Nesryin gabbroic intrusion is 617?±?19 Ma with initial ⁸⁷Sr/⁸⁶Sr?=?0.70322?±?0.00004. This age indicates that the mafic–ultramafic plutons in the Pan-African belt in southern Sinai belong to the Egyptian younger gabbros and not to the older metagabbro–diorite complexes or ophiolitic suites. The rocks have low ⁸⁷Sr/⁸⁶Sr initial ratios ranging from 0.703141 to 0.703338 and negative ? Sr ranging from ?6.34 to ?9.14. The initial ¹⁴³Nd/¹⁴⁴Nd ratios range from 0.511944 to 0.512145 with positive and high ? Nd values (1.93 to 5.86) reflecting a mantle contribution in their petrogenesis.     

Hydrogeologic and hydraulic characterization of aquifer and nonaquifer layers in a lateritic terrain (West Bengal,India)

The hydrogeologic and hydraulic characteristics of a lateritic terrain in West Bengal, India, were investigated. Test drilling was conducted at ten sites and grain-size distribution curves (GSDCs) were prepared for 275 geologic samples. Performance evaluation of eight grain-size-analysis (GSA) methods was carried out to estimate the hydraulic conductivity (K) of subsurface formations. Finally, the GSA results were validated against pumping-test data. The GSDCs indicated that shallow aquifer layers are coarser than the deeper aquifer layers (uniformity coefficient 0.19–11.4). Stratigraphy analysis revealed that both shallow and deep aquifers of varying thickness exist at depths 9–40 and 40–79 m, respectively. The mean K estimates by the GSA methods are 3.62–292.86 m/day for shallow aquifer layers and 0.97–209.93 m/day for the deeper aquifer layers, suggesting significant aquifer heterogeneity. Pumping-test data indicated that the deeper aquifers are leaky confined with transmissivity 122.69–693.79 m²/day, storage coefficient 1.01?×?10^?7–2.13?×?10^?4 and leakance 2.01?×?10^?7–34.56?×?10^?2 day^?1. Although the K values yielded by the GSA methods are generally larger than those obtained from the pumping tests, the Slichter, Harleman and US Bureau Reclamation (USBR) GSA methods yielded reasonable values at most of the sites (1–3 times higher than K estimates by the pumping-test method). In conclusion, more reliable aquifers exist at deeper depths that can be tapped for dependable water supply. GSA methods such as Slichter, Harleman and USBR can be used for the preliminary assessment of K in lateritic terrains in the absence of reliable field methods.     

Timing of the Yuchiling giant porphyry Mo system, and implications for ore genesis

The Yuchiling Mo deposit is a recently discovered giant porphyry system in the East Qinling Mo belt, China. Its apparent causative intrusion, i.e., the Yuchiling granite porphyry, is the youngest intrusion (phase 4) of the Heyu multiphase granite batholith, which was emplaced between 143 and 135 Ma. New robust constraints on the formation of the Yuchiling porphyry Mo system are provided by combined zircon U–Pb, biotite ⁴⁰Ar/³⁹Ar, and molybdenite Re–Os dating. Zircon grains from the Mo-mineralized granite porphyry yield weighted ²⁰⁶Pb/²³⁸U age of 134.0?±?1.4 Ma (n?=?19, 2σ error, MSWD?=?0.30). Magmatic biotite from the same sample yield a ⁴⁰Ar/³⁹Ar plateau age of 135.1?±?1.4 Ma (2σ error), and an inverse isochron age of 135.6?±?2.0 Ma (n?=?7, 2σ error, MSWD?=?10.8), which are effectively coincident with the zircon U–Pb age within analytical error. Three pulses of mineralization can be deduced from the molybdenite Re–Os ages, namely: ～141, ～137, and ～134 Ma, which agree well with the zircon U–Pb ages of granitic phases 1, 2, and the Yuchiling porphyry (phase 4), respectively. These well-constrained temporal correlations indicate that Mo mineralization was caused by pulses of granitic magmatism, and that the ore-forming magmatic-hydrothermal activity responsible for the Yuchiling porphyry Mo system lasted about 8 Ma. The Yuchiling Mo deposit represents a unique style of porphyry Mo system formed in a post-collision setting, and associated with F-rich, high-K calc-alkaline intrusions, which differ from convergent margin-associated porphyry Mo deposits.     

Mineralogy, conditions of crystallization and melt generation of epidote-bearing porphyries from the Middle Urals, Russian federation

Epidote-bearing porphyritic dikes (whole rock analysis: SiO₂?=?55–65 wt. %, MgO <2.1 wt. %, K₂O <2.5 wt. %, Al₂O₃ >17 wt. %, Na₂O + K₂O?=?5.7–9.4 wt. %) situated in the continental margin zone, the Middle Urals, Russian Federation have been dated using SHRIMP U-Pb zircon techniques and give a Middle Devonian age of 388?±?2 Ma and 389?±?6 Ma. The porphyries contain phenocrysts of magmatic epidote (Ps?=?17–25 %), Ca- and Mn-rich (CaO >9 wt. %; MnO >6 wt. %) almandine garnet, Al-rich (Al₂O₃?=?12–16 wt. %) amphibole, titanite, plagioclase, biotite, muscovite, apatite, and quartz. 60 to 70 % groundmass of the porphyritic dikes consists of fine-grained albite, quartz, and K-feldspar. A variety of thermobarometric estimations, plus comparison with published experimental data indicate that the phenocryst assemblage was stable between 5 and 11 kbar and 690 to 800 °C. Oxygen fugacity was close to or greater than logfo₂ = Ni-NiO + 1. Later stage formation of the quartz-feldspar groundmass took place at hypabyssal conditions, corresponding to 1 to 2 kbar and 660 to 690 °C. The porphyritic dikes are metaluminous to slightly peraluminous (ACNK?=?0.7–1.17). They are enriched in REE and depleted Nb and Ti. They show features typical of subduction-related magmas. Chemical composition and isotopic ratios of ⁸⁶Sr/⁸⁷Sr_i?=?0.709–0.720 suggest that both mantle- and deep crustal-derived materials were involved in their petrogenesis.     

Temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the Lochaber Ring Dyke Complex, North Queensland, Australia: insights from in situ U–Pb and Hf-isotope analysis of zircon

An existing model for the temporal and genetic relationships between the Kidston gold-bearing Breccia Pipe and the nearby Lochaber Ring Dyke Complex has been evaluated using in situ U–Pb and Hf-isotope analyses of zircon grains. The Oak River Granodiorite, the host rock to the Kidston Breccia Pipe, has 1,551?±?6 Ma old zircon cores overgrown by 417.7?±?2.2 Ma rims. The Black Cap Diorite and Lochaber Granite within the Lochaber Ring Dyke Complex have crystallisation ages of 350.7?±?1.3 and 337.9?±?2.6 Ma respectively. The gold-rich Median Dyke within the Kidston Breccia Pipe has a crystallisation age of 335.7?±?4.2 Ma, and thus is temporally related to the Lochaber Granite. However, zircon grains from the Median Dyke have less radiogenic Hf-isotope compositions (? _Hf from ?7.8 to ?15.8) than those from the Black Cap Diorite ?_Hf?=?0.4 to ?7.2) and the Lochaber Granite (? _Hf?=??1.0 to ?7.5), but within the range defined by zircons from the Oak River Granodiorite ? _Hf?=??8.0 to ?29.2). The Hf-isotope data thus rule out the proposed fractional crystallisation relationship between the Kidston gold-bearing rocks and the Lochaber Ring Dyke Complex. The Kidston Median Dyke may have been produced by mixing between Lochaber Granite magmas and magmas derived by remelting of the Oak River Granodiorite, which was itself derived from Proterozoic crust. There is no evidence for a juvenile component in the Lochaber Ring Dyke Complex or the Median Dyke. The gold enrichment in the Kidston rocks thus may reflect the multi-stage reworking of the Proterozoic crust, which ultimately produced the Carboniferous felsic magmas.     

Patterns in use of estuarine habitat by juvenile English sole (Pleuronectes vetulus) in four Eastern North Pacific estuaries

English sole (Pleuronectes vetulus) is one of a few commercially important marine fishes on the Pacific coast of North America that use estuarine areas as nurseries for juvenile stages. Trawl surveys of four United States Pacific Northwest estuaries were conducted to determine spatial patterns of juvenile English sole residence in estuaries during 1998–2000. Additional data from 1983–1988 were also analyzed. Two size classes of juvenile English sole were identified during surveys, with densities of small (Total length [TL] <50 mm) sole ranging from 0 to 11,300 fish ha^?1 across all sites, and densities of large (TL 50–150 mm) sole ranging from 0 to 33,000 fish ha^?1 across all sites. Principal components analysis of static habitat data collected at each trawl survey site was used to define habitat types within each estuary, and discriminant function analysis was used to test the resulting classification scheme. Both small and large cohort English sole used lower side channel locations at significantly higher densities than other estuarine areas. Small English sole also showed significant relationships with both bottom temperature and depth. These patterns in habitat use were consistent across all estuaries and indicate that English sole used shallow depth areas surrounded by extensive tidal flats, where temperatures were optimal for growth. The analysis also suggested a carrying capacity may exist for large English sole in nursery estuaries.     

Coastal Habitat Use and Residency of Juvenile Atlantic Sharpnose Sharks (Rhizoprionodon terraenovae)

Coastal habitat use and residency of a coastal bay by juvenile Atlantic sharpnose sharks, Rhizoprionodon terraenovae, were examined by acoustic monitoring, gillnet sampling, and conventional tag–recapture. Acoustic monitoring data were used to define the residency and movement patterns of sharks within Crooked Island Sound, Florida. Over 3 years, sharks were monitored for periods of 1–37 days, with individuals regularly moving in and out of the study site. Individual sharks were continuously present within the study site for periods of 1–35 days. Patterns of movement could not be correlated with time of day. Home range sizes were typically small (average?=?1.29 km²) and did not vary on a yearly basis. Gillnet sampling revealed that juvenile Atlantic sharpnose sharks were present in all habitat types found within Crooked Island Sound, and peaks in abundance varied depending on month within a year. Although telemetry data showed that most individuals remained within the study site for short periods of time before emigrating, conventional tag–recapture data indicates some individuals return to Crooked Island Sound after extended absences (maximum length?=?1,352 days). Although conventional shark nursery theory suggests small sharks remain in shallow coastal waters to avoid predation, juvenile Atlantic sharpnose sharks frequently exited from protected areas and appear to move through deeper waters to adjacent coastal bays and estuaries. Given the high productivity exhibited by this species, the benefit gained through a nursery that reduces predation may be limited for this species.     

Calculating groundwater mixing ratios in groundwater-inrushing aquifers based on environmental stable isotopes (D, 18O) and hydrogeochemistry

Conventional hydrogeochemical data and environmental stable isotopes are used to identify the recharge sources and the water–rock interactions in the groundwater-flowing direction within the multilayer groundwater system of the Sulin coal-mining district in the north Anhui province in China. δD and δ ¹⁸O of groundwater in the mining district decrease along the groundwater-flowing direction in the recharge areas, yet in the runoff or discharge areas, they rise and fall along average δ values (δ ¹⁸O = ?8.68 ‰, δD = ?67.4 ‰), which are lower than average δ values of local atmospheric precipitation (δ ¹⁸O = ?7.80 ‰, δD = ?52.4 ‰). Principal component analysis is used to analyze the conventional hydrogeochemical data (K⁺ + Na⁺, Mg²⁺, Ca²⁺, Cl^?, SO₄ ^2?, HCO₃ ^?, CO₃ ^2?) in the groundwater. The first and second principal components have large variance contributions, and represent “pyrite oxidation or groundwater hardening” and “desulfurization or cation exchange and adsorption,” respectively. From conventional hydrogeochemical data and environmental stable isotopes, it is demonstrated that groundwater of the Sulin coal-mining district is characterized by a mixing type, which is confirmed by three recharge end-members: fresh groundwater, leaching groundwater, and retained groundwater. By means of a sample dot-encompassed triangle in the scatter diagram of load scores for Component 1–Component 2, whose vertexes stand for the three end-members, a model for calculating groundwater mixing ratio is established and applied successfully to the evaluation and management of groundwater hazards in the coal-mining districts.     

Thermochemistry of monazite-(La) and dissakisite-(La): implications for monazite and allanite stability in metapelites

Thermochemical properties have been either measured or estimated for synthetic monazite, LaPO₄, and dissakisite, CaLaMgAl₂(SiO₄)₃OH, the Mg-equivalent of allanite. A dissakisite formation enthalpy of ?6,976.5 ± 10.0 kJ mol^?1 was derived from high-temperature drop-solution measurements in lead borate at 975 K. A third-law entropy value of 104.9 ± 1.6 J mol^?1 K^?1 was retrieved from low-temperature heat capacity (C _p) measured on synthetic LaPO₄ with an adiabatic calorimeter in the 30–300 K range. The C _p values of lanthanum phases were measured in the 143–723 K range by differential scanning calorimetry. In this study, La(OH)₃ appeared as suitable for drop solution in lead borate and represents an attractive alternative to La₂O₃. Pseudo-sections were calculated with the THERIAK-DOMINO software using the thermochemical data retrieved here for a simplified metapelitic composition (La = ∑REE + Y) and considering monazite and Fe-free epidotes along the dissakisite-clinozoïsite join, as the only REE-bearing minerals. Calculation shows a stability window for dissakisite-clinozoïsite epidotes (T between 250 and 550°C and P between 1 and 16 kbar), included in a wide monazite field. The P–T extension of this stability window depends on the bulk-rock Ca-content. Assuming that synthetic LaPO₄ and dissakisite-(La) are good analogues of natural monazite and allanite, these results are consistent with the REE-mineralogy sequence observed in metapelites, where (1) monazite is found to be stable below 250°C, (2) around 250–450°C, depending on the pressure, allanite forms at the expense of monazite and (3) towards amphibolite conditions, monazite reappears at the expense of allanite.     

Fluoride sorption and desorption on soils located in the surroundings of an aluminium smelter in Galicia (NW Spain)

Aluminium smelters are major sources of F emission to the environment. We studied, in laboratory experiments, the sorption and desorption of fluoride on organic and mineral horizons of soils located within 2 km from one of these factories, situated in the northern coast of Galicia (NW Spain). The soils, developed from granite, are acid (pH H₂O 3.9–5.5), rich in organic matter (4–16 % C in the A horizon) and most A horizons have high Al saturation in the exchange complex. All samples showed a notable F sorption, between 1,066 and 1,589 mg kg^?1, after adding 200 mg F L^?1, which accounts for 53–80 % of F added. The sorption was slightly higher in the A horizons than in the respective organic horizons (differences of up to 194 mg kg^?1). The fluoride sorption upon addition of 200 mg F L^?1 correlated significantly (p < 0.05) with soil pH in water (r = ?0.77), iron extracted by acid ammonium oxalate (r = 0.68), aluminium plus iron extracted by acid ammonium oxalate (r = 0.63), exchange aluminium (r = 0.52) and clay percentage in soil (r = 0.76). The F sorption fitted to both Langmuir and Freundlich models. Desorbed F accounted for only 12–22 % of sorbed fluoride and correlated (p < 0.05) negatively with non-crystalline (extracted by acid ammonium oxalate) Fe (r = ?0.51) and clay content (r = ?0.74) and positively with organic matter (r = 0.69) and with the effective cation exchange capacity of the soil (r = 0.50).     

Spatio-Temporal Patterns of Submerged Macrophytes in Three Hydrologically Altered Mediterranean Coastal Lagoons

Rice cultivation in the Ebro Delta (Catalonia, Spain) has inverted the natural hydrological cycles of coastal lagoons and decreased water salinities for over 150 years. Adjustments in the water management practices—in terms of source and amount of freshwater inputs—have resulted in changes in the diversity, distribution and productivity of submerged angiosperms. Between the 1970s and late 1980s, a massive decline of the aquatic vegetation occurred in the Encanyissada–Clot and Tancada lagoons, but little information on the status is available after the recovery of macrophytes in the 1990s. Here, we evaluate the influence of salinity regimes resulting from current water management practices on the composition, distribution, seasonal abundance and flowering rates of submersed macrophytes, as well as on the occurrence of epiphyte and drift macroalgae blooms in three coastal lagoons. Our results show that Ruppia cirrhosa is the dominant species in the Encanyissada lagoon (185.97?±?29.74 g?DW?m^?2?year^?1; 12–27?‰ salinity) and the only plant species found in the Tancada lagoon (53.26?±?10.94 g?DW?m²?year^?1; 16–28?‰ salinity). Flowering of R. cirrhosa (up to 1,011?±?121 flowers?m^?2) was only observed within the Encanyissada and suggests that mesohaline summer conditions may favor these events. In contrast, low salinities in Clot lagoon (～3–12?‰) favor the development of Potamogeton pectinatus (130.53?±?13.79 g?DW?m²?year^?1) with intersperse R. cirrhosa (8.58?±?1.71 g?DW?m^?2) and mixed stands of P. pectinatus and Najas marina (up to ～57 g?DW?m^?2?year^?1) in some reduced areas. The peak biomasses observed during the study are 88 to 95 % lower than maximum values reported in the literature at similar salinities, and there is also little or no recovery in some areas compared to last reports more than 20 years ago. The main management actions to restore the natural diversity and productivity of submersed angiosperms, such as the recovering of the seagrass Zostera noltii, should be the increase of salinity during the period of rice cultivation, by reducing freshwater inputs and increasing flushing connections with the bays.     

Carbon dioxide in Postojna Cave (Slovenia): spatial distribution,seasonal dynamics and evaluation of plausible sources and sinks

The CO₂ concentration of the air in Postojna Cave (400–7900 ppm) is found to be induced by CO₂ sources (human respiration contributing?~?20,000–58,000 ppm per breath, outgassing of dripwater and water seeping from the vadose zone/epikarst with a pCO₂ values of 5000–29,000 ppm, and underground Pivka River having pCO₂ at 2344–4266 ppm) and CO₂ dilution (inflow of outside air with a CO₂ concentration of?~?400 ppm). Measurements show that sinking Pivka River has the lowest CO₂ concentration among plausible CO₂ sources but still continuously exceeds the surrounding cave air CO₂ concentration. During the winter months, intensive ventilation reduces the cave air CO₂ concentration to outside levels (~?400 ppm), even in the centre of the cave system. CO₂ dilution is less pronounced in summer (CO_2(min)?≈?800 ppm), since the ventilation rate is not as strong as in winter and the outside air that enters the cave through breathing holes and fractures is enriched with soil CO₂. During spring and autumn, the daily alternation of the ventilation regime with a smaller rate of air exchange results in yearly cave air CO₂ peaks of up to?~?2400 ppm. Some dead-end passages can be much less affected by ventilation, resulting in a cave air CO₂ concentration of up to 7900 ppm. The strongest diurnal CO₂ peaks due to human respiration were recorded during the spring holidays (increase of up to 1300 ppm day^?1), compared to considerably smaller summer peaks despite peak visits (increase of?~?600 ppm day^?1).     

Zircon U-Pb age, geochemical, and Sr-Nd-Pb isotopic constraints on the origin of alkaline intrusions in eastern Shandong Province, China

Alkaline intrusions in the eastern Shandong Province consist of quartz monzonite and granite. U-Pb zircon ages, geochemical data, and Sr-Nd-Pb isotopic data for these rocks are reported in the present paper. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U-Pb zircon analyses yielded consistent ages ranging from 114.3?±?0.3 to 122.3?±?0.4 Ma for six samples of the felsic rocks. The felsic rocks are characterised by a wide range of chemical compositions (SiO₂?=?55.14–77.63 wt. %, MgO?=?0.09–4.64 wt. %, Fe₂O₃?=?0.56–7.6 wt. %, CaO?=?0.40–5.2 wt. %), light rare earth elements (LREEs) and large ion lithophile elements (LILEs) (i.e., Rb, Pb, U) enrichment, as well as significant rare earth elements (HREEs) and heavy field strength (HFSEs) (Nb, Ta, P and Ti) depletion, various and high (⁸⁷Sr/⁸⁶Sr) _i ranging from 0.7066 to 0.7087, low ε _Nd (t) values from ?14.1 to ?17.1, high neodymium model ages (T_DM1?=?1.56–2.38Ga, T_DM2?=?2.02–2.25Ga), ²⁰⁶Pb/²⁰⁴Pb?=?17.12–17.16, ²⁰⁷Pb/²⁰⁴Pb?=?15.44–15.51, and ²⁰⁸Pb/²⁰⁴Pb?=?37.55–37.72. The results suggested that these rocks were derived from an enriched crustal source. In addition, the alkaline rocks also evolved as the result of the fractionation of potassium feldspar, plagioclase, +/? ilmenite or rutile and apatite. However, the alkaline rocks were not affected by crustal contamination. Moreover, the generation of the alkaline rocks can be attributed to the structural collapse of the Sulu organic belt due to various processes.