A cleaner river: long term use of semipermeable membrane devices demonstrate that concentrations of selected organochlorines and PAHs in the Brisbane River estuary, Queensland have reduced substantially over the past decade

We first used semipermeable membrane devices as samplers to evaluate concentrations of organochlorines and PAHs in the Brisbane River in 1998. Here we revisit this work and repeat the study a decade later in the same season (summer), also taking account of results from a similar study involving PAHs in the summer of 2001-2002. The accumulation of organochlorines and most PAHs in the samplers in the recent assessment was substantially less than in the 1998 deployment, suggesting that the ambient concentrations of these chemicals have decreased considerably over the last decade. In all cases there was high reproducibility of the mass of chemicals accumulated in the sampler. We used performance reference compounds in the later deployment, and assuming that the kinetics were similar in both deployment periods, we estimate that the concentration of dieldrin, the organochlorine found at highest concentrations, decreased from approximately 3.9 ng/L to about 1.4 ng/L. The decrease of most other analytes of interest including DDE and DDD was greater, potentially indicating that dieldrin is still entering the Brisbane River through run-off from urban areas where it was used widely for treatment of termites until 1995. DDT use in Australia ceased in the mid 1980s.     

Occurrence of endocrine-disrupting chemicals in riverine sediments from the Pearl River Delta,China

The endocrine-disrupting chemicals (EDCs) was investigated in 28 riverine sediments from the Pearl River system, China and analyzed by an ultrasonication extraction and GC–MS method. The concentrations of 4-tert-octylphenol (OP), 4-nonylphenol (NP), and bisphenol A (BPA) in the sediments were in the ranges of <2.0–210, 107–16198 and <1.7–430 ng/g dw, respectively. The steroid estrogens estrone (E1) and 17β-estradiol (E2) in the sediments ranged from <1.3 to 10.9 ng/g dw and from <0.9 to 2.6 ng/g dw, respectively. The spatial distribution of these chemicals was related to the discharge of domestic and industrial wastewater along the rivers. The positive correlation between EDCs and total organic carbon indicates that sedimentary organic carbon is an important factor in controlling the distributions of EDCs. Compared with other previous studies, the ZR and DR rivers from the PRD were heavily contaminated by APs and BPA.     

Distribution,sources and ecological risk assessment of PAHs in surface sediments from Guan River Estuary,China

The contamination of surface sediments in Guan River Estuary, China, by polycyclic aromatic hydrocarbons (PAHs) has been fully investigated. Total concentrations of 21 PAHs ranged from 90 to 218 ng/g with an average of 132.7 ng/g, which is relatively low in comparison with other estuaries around the world. PAH concentrations appeared to be positively correlated with clay content and negatively correlated with sediment grain size. Source identification implied that the PAHs originated mainly from pyrolytic sources. However, source patterns may be continuously changed to a petrogenic origin due to the heavy ship traffic and continuous discharge of oily sewage in this area. The PAH levels were also compared with international Sediments Quality Guidelines and Sediments Quality Criteria, and the results indicated low negative effects for most individual PAHs. However, toxic effects related to FLO would occur occasionally in most locations in the estuary.     

Perfluorinated compounds in surficial sediments of the Ganges River and adjacent Sundarban mangrove wetland,India

This study reports the first evidence of the quantification of two dominant perfluorinated compounds (PFCs), namely perfluorooctanesulfate (PFOS) and perfluorooctannoate (PFOA), in surface sediment samples (0–5 cm; n = 13) from the Ganges (Hugli) River including Sundarban wetland, India using HPLC–MS/MS. The concentrations of PFOA exhibited a wide range of concentrations from <0.5 to 14.09 ng/g dry wt, whereas the concentration of PFOS was always below the detection limit of <0.5 ng/g dry wt. A consistent enrichment of PFOA was recorded in all the five sites of Sundarban (mean value 11.61 ± 1.86) whereas it was of moderate concentration or below the detection level in the seven sites along with the lower stretch of the Ganges (Hugli) River estuary (mean value 5.96 ng/g dry wt ± 5.36). Wastewater and untreated effluents are likely the major causes of accumulation of PFCs in sediments. The present paper could be used as baseline study to assess future monitoring programs of the ecosystem.     

Distribution and sources of polycyclic aromatic hydrocarbons in surface sediments of the Hormuz strait,Persian Gulf

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in the sediment from the Hormuz strait, Persian Gulf. The sum of 16 PAHs (ΣPAH) concentrations varied from 72.17 to 277.77 ng g⁻¹ dry weight, with an average value of 131.20 ± 59.29 ng g⁻¹ dry weight. An ecological risk assessment of PAHs, indicated that adverse biological effects caused by acenaphthene and acenaphthylene occasionally may take place in the sediment of Hormuz strait. PAH source identification showed that the PAHs in the sediments come from pyrogenic and mixed origin. Based on classification of pollution levels, sediments from Hormuz strait could be considered as low to moderately polluted with PAHs.     

Enrichment and partitioning of polycyclic aromatic hydrocarbons in the sea surface microlayer and subsurface water along the coast of Xiamen Island,China

Sea microlayer (SML) and subsurface water (SSW) samples were collected around Xiamen Island to study the enrichment and partitioning of polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 93.43 to 411.05 ng L⁻¹ in the SML and 49.29–279.42 ng L⁻¹ in the SSW. Compared with the results of previous studies before pollution control measurements, PAHs levels decreased significantly. The enrichment factors (EFs) of dissolved and particulate PAHs varied from 0.68 to 2.71 and 0.43–3.56. EFs showed the consistent enrichment trends with sites and exhibited different enrichment characteristics between 2 and 3 ring PAHs and 4 ring PAHs. Furthermore, the much higher concentrations of BaP (strong carcinogenicity) were accompanied by higher EFs in the SML samples from the Western Xiamen Harbour, which together indicated the risk of impacts to the fish eggs that usually float on the SML water after exposure to oil spills and combustion, contributed directly by the port and shipping activities.     

Polycyclic aromatic hydrocarbons in the coastal water,surface sediment and mullet Liza klunzingeri from northern part of Hormuz strait (Persian Gulf)

The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in mullet (Liza klunzingeri), water and sediment from northern part of Hormuz strait (Persian Gulf). The concentration levels of total PAHs in L. klunzingeri, water and sediment were 133.99–268.57 ng g⁻¹ dry weight, 3.12–5.88 ng l⁻¹ and 42.29–228.9 ng g⁻¹ dry weight, respectively. Based on isomer ratios, analysis of the PAHs source in the sediment demonstrated that the PAHs come from pyrogenic and petrogenic origin. Risk assessment showed PAHs threshold concentrations to occasionally be exceeded in the study area.     

Sediment PAH: Contrasting levels in the Caspian Sea and Anzali Wetland

A comparative study of 23 PAH congeners in sediment of the Caspian Sea coast and Anzali Wetland was conducted in 2010. Surface sediment was analyzed using chromatography and mass spectrometry. Total PAH concentrations ranged between 212 and 9009 ng g⁻¹ dw. Spatial distribution maps revealed that PAH levels were higher in the coastal areas of the Caspian Sea where oil related activities have been common since 1800’s. Diagnostic ratios analysis indicated that PAHs largely originated from petrogenic processes. PAH toxicity level was assessed using sediment quality guidelines and toxic equivalent concentrations to determine toxic effects on marine organism. Based on these investigations, in our study areas, the probability of toxicity for benthic organisms is “low to medium”. The toxic equivalent concentrations of carcinogenic PAHs varied between 11 and 231 ng TEQ/g; higher total toxic equivalent concentrations values were found in the coastal areas of the Caspian Sea.     

The molecular and isotopic effects of hydrothermal alteration of organic matter in the Paleoproterozoic McArthur River Pb/Zn/Ag ore deposit

The molecular distribution and compound specific stable carbon and hydrogen isotope ratios were measured on solvent extractable hydrocarbons from the Late Paleoproterozoic McArthur River, or “Here's Your Chance” (HYC) Pb/Zn/Ag ore deposit in the Northern Territory of Australia. Five samples were collected from the McArthur River mine on a northeast–southwest transect in order to sample a gradient of hydrothermal alteration. One sample was taken from the unmineralized W-Fold Shale unit immediately below the HYC ore deposit. δD of n-alkanes, branched alkanes and bulk aromatic fractions were measured, and δ¹³C of n-alkanes, polynuclear aromatic hydrocarbons (PAHs) and bulk kerogen were measured to assess the isotopic effects of a varying degree of hydrothermal alteration on different components of HYC organic matter (OM). Relative to n-alkanes in Barney Creek Formation sediments that did not undergo mineralization, HYC n-alkanes are enriched in deuterium (D) by 50–60‰. This is likely to be a result of equilibrium hydrogen exchange during ore genesis with a highly D-enriched fluid that originated in an evaporitic basin. Trends with distance along the sample transect are ambiguous, but from the northernmost to southernmost point, n-alkanes are less D-enriched, and PAHs are less abundant and less ¹³C-enriched. This could be due to decreasing hydrothermal alteration effects, decreasing delivery of highly altered OM by the mineralizing fluid, or both. The carbon isotopic composition of HYC PAHs is inconsistent with a Barney Creek Fm source, but consistent with an origin in the underlying Wollogorang Formation. PAHs are ¹³C-depleted relative to n-alkanes, reflecting a kerogen source that was ¹³C-depleted compared to n-alkanes, typical for Precambrian sediments. PAHs are more ¹³C-depleted with increasing molecular weight and aromaticity, strengthening the case for a negative isotopic effect associated with aromatization in ancient sediments. Together, these data are consistent with a an ore deposition model in which fluids originated in an evaporitic deposit lower in the basin and interacted with metals and OM in the Tawallah Group at temperatures above 250 °C and a depth of ~ 6 km before ascending along a flower structure associated with the Emu Fault and cooling to 200 ± 20 °C before reaching Barney Creek sediments.     

PAHs contamination and bacterial communities in mangrove surface sediments of the Jiulong River Estuary,China

Sixteen sediment samples collected from eight transects in a mangrove swamp of the Jiulong River Estuary, Fujian, China were investigated for their content of polycyclic aromatic hydrocarbons (PAHs) and the biodegradation potential of the indigenous microorganisms. The bacterial community structures in the mangrove sediments and in enrichment cultures were also investigated. The results showed that the total PAHs concentration of mangrove sediments ranged from 280 to 1074 ng g⁻¹ dry weight, that the PAHs composition pattern in the mangrove sediments was dominated by high molecular weight PAH components (4–6 rings), and that Benzo[ghi]perylene and Indeno[1,2,3-cd]pyrene were the most dominant at different stations. Abundant PAH-degrading bacteria were found in all the stations, the values of phenanthrene-degrading bacteria ranged from 5.85 × 10⁴ to 7.80 × 10⁵ CFU g⁻¹ dry weight, fluoranthene-degrading bacteria ranged from 5.25 × 10⁴ to 5.79 × 10⁵ CFU g⁻¹ dry weight, pyrene-degrading bacteria ranged from 3.10 × 10⁴ to 6.97 × 10⁵ CFU g⁻¹ dry weight and the benzo(a)pyrene-degrading bacteria ranged from 5.25 × 10⁴ to 7.26 × 10⁵ CFU g⁻¹ dry weight. DGGE analysis of PCR-amplified 16S rDNA gene fragments confirmed that there was a remarkable shift in the composition of the bacterial community due to the addition of the different model PAH compound phenanthrene (three ring PAH), fluoranthene(four ring PAH), pyrene(four ring PAH) and benzo(a)pyrene(five ring PAH) during enrichment batch culture. Eleven strains were obtained with different morphology and different degradation ability. The presence of common bands for microbial species in the cultures and in the native mangrove sediment DNA indicated that these strains could be potential in situ PAH-degraders.     

Occurrence and phase distribution of polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta,China

The occurrence and phase distribution of polycyclic aromatic hydrocarbons (PAHs) in waters at the eight riverine outlets of the Pearl River Delta (China) were examined based on a monthly sampling program from March 2005 to February 2006. The total concentrations of PAHs in the aqueous phase and suspended particulate matter (SPM) combined ranged from 55.5 to 522 ng/L, at the mid level of the global values in rivers and estuaries. No clear temporal and spatial trends of PAH concentrations were found. However, the concentrations of PAHs associated with SPM coincided with the monthly precipitation of Guangzhou, indicating the importance of atmospheric deposition. The PAHs found in the region were likely derived from a combined pyrolytic and petrogenic origin, as suggested by the molecular indices of PAHs. Normalized partition coefficient (K_oc) between water and SPM was correlated with octanol–water partition coefficient (K_ow) to understand the environmental behavior of PAHs.     

Distribution,origin, and potential toxicological significance of polycyclic aromatic hydrocarbons (PAHs) in sediments of Kaohsiung Harbor,Taiwan

Sediment samples were collected from 12 locations of Kaohsiung Harbor, Taiwan and analyzed for polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations varied from 472 to 16,201 ng g⁻¹ dry weight. The highest PAH concentrations were from the industrial zone docks situated in south Kaohsiung Harbor. Diagnostic ratios showed that the possible source of PAHs in the industrial zone dock could be coal combustion while in the other zones it could be petroleum combustion. The toxic equivalent concentrations (TEQ^carc) of PAHs varied from 55 to 1964 ng TEQ g⁻¹ dry weight. Higher total TEQ^carc values were found at industrial zone docks (from 1404 to 1964 ng TEQ g⁻¹ dry weight). As compared with the US Sediment Quality Guidelines (SQGs), the observed levels of PAHs at industrial zone docks exceeded the effects range low (ERL), and could thus cause acute biological damage. However, the lower levels of PAHs at the other zones would probably not exert adverse biological effects.     

Occurrence of polycyclic aromatic hydrocarbons (PAHs) in seawater from the Western Taiwan Strait,China

Seawater samples (including surface water and bottom water) were collected from the Western Taiwan Strait (WTS) during June 24–25, 2009; polycyclic aromatic hydrocarbons (PAHs) in dissolved phase and particulate phase were analyzed, respectively. The results showed that the total concentrations of PAHs in the dissolved phase and particulate phase were ranged from 12.3 to 58.0 ng L⁻¹, and 10.3–45.5 ng L⁻¹, which showed a low-middle contamination level in the China Seas. The spatial variability of PAHs may be related to the complicated currents of WTS, especially the Min-Zhe coastal current. PAHs diagnostic ratios suggested that PAHs mainly originated from the inputs of pyrolytic (combustion) sources, which might be contributed to land-based atmospheric deposition. The particle-water partition coefficients of individual PAH showed that partitions were not correlated with suspended particulate matter content, dissolved organic carbon or salinity, similar to the Yangtze coastal area.     

Regional distribution of halogenated organophosphate flame retardants in seawater samples from three coastal cities in China

Thirteen samples of seawater were collected from Yellow Sea and East China Sea near Qingdao, Lianyungang, and Xiamen, China. They were analyzed for halogenated organophosphorus flame retardants (OPFRs). The compounds selected for detection were Tris(2-chloroethyl) phosphate (TCEP), Tris(2-chloroisopropyl) phosphate (TCPP), Tris (1,3-dichloro-2-propyl) phosphate (TDCPP), and Tris(2,3-dibromopropyl) phosphate (TDBPP). The total concentrations ranged from 91.87 to 1392 ng/L and the mean concentrations of these four chemicals were 134.44, 84.12, 109.28, and 96.70 ng/L, respectively. TCEP exhibited the highest concentrations, although concentrations of TCPP and TDCPP were also fairly high in Lianyungang and Xiamen. Generally, Lianyungang was the most heavily polluted district, with very high concentrations of TCEP at LYG-2 (550.54 ng/L) and LYG-4 (617.92 ng/L). The main sources of halogenated OPFRs were municipal and industrial effluents of wastewater treatment plants in the nearby economic and industrial zones.     

Characterization and composition of heavy metals and persistent organic pollutants in water and estuarine sediments from Gao-ping River,Taiwan

The objective of this study was to determine the concentrations and possible sources of heavy metals and persistent organic pollutants (POPs) in water and estuarine sediments from Gao-ping River in order to evaluate the environmental quality of aquatic system in southern Taiwan. High concentrations of heavy metals including Cr, Zn, Ni, Cu and As, ranging from 10.7 to 180 mg/kg-dry weight (dw), were detected in sediments from Gao-ping River. When normalized to the principal component analysis (PCA), swinery and electroplating wastewaters were found to be the most important pollution sources for heavy metals. Of various organochlorine pesticide (OCP) residues detected, aldrin and total-hexachlorocyclohexane (HCH) were frequently found in sediments. The total concentrations of OCPs were in the range 0.47–47.4 ng/g-dw. Also, the total-HCH, total-cyclodiene, and total-dichlorodiphenyltrichloroethane (DDT) were in the range 0.37–36.3, 0.21–19.0, and 0.44–1.88 ng/g-dw, respectively. The polychlorinated biphenyl (PCB) concentrations in sediments from Gao-ping River ranged between 0.37 and 5.89 ng/g-dw. The PCB concentrations are positively correlated to the organic contents of the sediment particles. α-HCH was found to be the dominant compound of HCH in the sediments, showing that long-range transport may be the possible source for the contamination of HCH in sediments from Gao-ping River. In summary, trace amounts of POPs in estuarine sediments from Gao-ping River were detected, showing that there still exist a wide variety of POP residues in the river sediments in Taiwan. These POP residues may be mainly from long-range transport and weathered agricultural soils, while heavy metal contamination is primarily from the swinery and industrial wastewaters.     

Ten-year study of cloud-to-ground lightning activity in the Iberian Peninsula

The characteristics (annual and diurnal cycle, polarity, multiplicity and first stroke peak current) of ∼4.3×10⁶ cloud-to-ground flashes recorded in the Iberian Peninsula during the first decade of measurements of the lightning detection network installed in Spain are analyzed. The mean monthly variation shows maximum lightning activity between May and September, while minimum values are observed in January and February. The mean diurnal cycle shows maximum values at 1700 LT and minimum values at around 1000 LT. The average maximum flash density (not corrected for detection efficiency) is 2.1 flashes km⁻² year⁻¹. Maximum lightning activity is associated with mountainous areas. The effect of the Mediterranean Sea is also seen. The percentage of positive flashes is 9%, although this changes over the year from 6.5% in June to 22.6% in January. The average multiplicity is found to be 2.0 for the negative flashes and 1.1 for the positive flashes, and the percentages of single-stroke flashes are 53.6% and 89%, respectively. The monthly distribution of multiplicity for negative flashes peaks in the summer and minimum values are found in the winter. The multiplicity of the positive flashes does not seem to be function of the month. The median (mean) first stroke peak currents are found to be 23.5 kA (27.3 kA) for the negative flashes and 35.3 kA (47.1 kA) for the positive flashes. For both polarities, the peak current is higher in the summer than in the winter. The percentage of positive flashes and the mean peak currents for negative flashes are higher over the sea areas than over land.     

Winter variability of physical processes and sediment-transport events on the Eel River shelf,northern California

A 5-yr data set of near-bed current and suspended-sediment concentration measured within 2 m of the seabed in 60-m water depth has been analyzed to evaluate the interannual variability of physical processes and sediment transport events on the Eel River continental shelf, northern California. This data set encompasses a wide range of shelf conditions with winter events characterized as: Major Flood (1996/97), strong El Niño (1997/98), strong La Niña (1998/99), and Major Storm (1999/00). Data were collected at a site located 25 km north of the Eel River mouth, on the landward edge of the mid-shelf mud deposit. During the winter months sediment resuspension is forced primarily by near-bed oscillatory flows, and sediment transport occurs both as suspended load and as gravity-driven (fluid-mud) flows. Winter conditions that caused periods of increased sediment transport existed on average for 142 d yr⁻¹ over the total record, ranging between 89 d in the Major Flood year (1996/97) and 171 d in the La Niña year (1998/99). Hourly averaged values of significant wave height varied between 0.5 and 10.7 m and hourly averaged values of near-bed orbital velocities ranged between 0 and 125 cm s⁻¹. During the five winters, sediment threshold conditions were exceeded an average of 35% of the time, ranging from 19% in the Major Flood year (1996/97) to 52% in the La Niña year (1998/99). Mean concentration of suspended sediment, measured at 30 cmab, ranged from values close to 0–8 g l⁻¹. Among winters, major sediment flux events exhibited different patterns due to varying combinations of physical processes including river floods, waves, and shelf circulation. Within winters, the major period of sediment flux varied from a 3-d fluid mud event (Major Flood winter) to a 50-d period of persistent southerlies (El Niño winter) and a winter of continuous storm cycles (La Niña winter). Winter-averaged suspended-sediment concentration appeared to vary in response to river discharge, while total sediment flux responded to storm intensity. The net sediment flux appeared to depend on timing of river discharge and shelf conditions. On the Eel River shelf, the mid-shelf mud deposit apparently is not emplaced by deposition from the river plume, but by secondary processes from the inner shelf including off-shelf transport of sediment suspensions and gravity-driven fluid-mud flows. Thus, these inner-shelf processes redistribute sediment supplied by the Eel River (a point source) making the inner shelf a line source of sediment that forms and nourishes the mid-shelf deposit. Large-scale shelf circulation patterns and interannual variability of the physical forcing are also important in determining the locus of the mid-shelf deposit, and both are influenced by climate variations. Post-depositional alteration of the deposit also depends on the subsequent shelf conditions following major floods.     

Spatio-temporal variability of size fractionated phytoplankton on the shelf adjacent to the Ebro river (NW Mediterranean)

The mesoscale distribution and seasonal variation of the size structure of phytoplankton biomass, as measured by chlorophyll a (chl a), was studied in the Ebro shelf area (NW Mediterranean) during three different seasons: autumn, winter and summer. In autumn and summer, when the water column was, respectively, slightly or strongly stratified and nutrient concentrations were low at surface, average total chl a values were 0.31 and 0.29 mg m⁻³, respectively. In winter, the intrusion of nutrients into the photic zone by intense vertical mixing and strong riverine inputs, produced an increase of the total autotrophic biomass (0.76 mg m⁻³). In the three seasons, the main contributor to total chl a was the picoplanktonic (<2 μm) size fraction (42% in winter and around 60% in autumn and summer). The nanophytoplankton (2–20 μm) contribution to total chl a showed the lowest variability amongst seasons (between 29% and 39%). The microplanktonic (>20 μm) chl a size fraction was higher in winter (27%) than in the other seasons (less than 13%). The maximum total chl a concentrations were found at surface in winter, at depths of 40 m in autumn and between 50 and 80 m in summer. The relative contribution of the <2 μm size fraction at these levels of the water column tended to be higher than at other depths in autumn and winter and lower in summer. In autumn and winter, nutrient inputs from Ebro river discharge and mixing processes resulted in an increase on the >2 μm contribution to total chl a in the coastal zone near the Ebro Delta area. In summer, the contribution of the <2 and >2 μm chl a size fractions was homogeneously distributed through the sampling area. In autumn and summer, when deep chl a maxima were observed, the total amount of the autotrophic biomass in the superficial waters (down to 10 m) of most offshore stations was less than 10% of the whole integrated chl a (down to 100 m or to the bottom). In winter, this percentage increased until 20% or 40%. The >2 μm chl a increased linearly with total chl a values. However, the <2 μm chl a showed a similar linear relationship only at total chl a values lower than 1 mg m⁻³ (in autumn and summer) or 2 mg m⁻³ (winter). At higher values of total chl a, the contribution of the <2 μm size fraction remained below an upper limit of roughly 0.5 mg m⁻³. Our results indicate that the picoplankton fraction of phytoplankton may show higher seasonal and mesoscale variability than is usually acknowledged.     

Decoupled warming and monsoon precipitation in East Asia over the last deglaciation

Our understanding of the continental climate development in East Asia is mainly based on loess–paleosol sequences and summer monsoon precipitation reconstructions based on oxygen isotopes (δ¹⁸O) of stalagmites from several Chinese caves. Based on these records, it is thought that East Asian Summer Monsoon (EASM) precipitation generally follows Northern Hemisphere (NH) summer insolation. However, not much is known about the magnitude and timing of deglacial warming on the East Asian continent. In this study we reconstruct continental air temperatures for central China covering the last 34,000 yr, based on the distribution of fossil branched tetraether membrane lipids of soil bacteria in a loess–paleosol sequence from the Mangshan loess plateau. The results indicate that air temperature varied in phase with NH summer insolation, and that the onset of deglacial warming at ~ 19 kyr BP is parallel in timing with other continental records from e.g. Antarctica, southern Africa and South-America. The air temperature increased from ~ 15 °C at the onset of the warming to a maximum of ~ 27 °C in the early Holocene (~ 12 kyr BP), in agreement with the temperature increase inferred from e.g. pollen and phytolith data, and permafrost limits in central China.Comparison of the tetraether membrane lipid-derived temperature record with loess–paleosol proxy records and stalagmite δ¹⁸O records shows that the strengthening of EASM precipitation lagged that of deglacial warming by ca. 3 kyr. Moreover, intense soil formation in the loess deposits, caused by substantial increases in summer monsoon precipitation, only started around 12 kyr BP (ca. 7 kyr lag). Our results thus show that the intensification of EASM precipitation unambiguously lagged deglacial warming and NH summer insolation, and may contribute to a better understanding of the mechanisms controlling ice age terminations.     

Present warming within the context of cooling–warming cycles observed since 1854 in the Bay of Biscay

The warming trend observed during the last decades in the Bay of Biscay is put within the context of sea surface temperature (SST) changes observed in the area since 1854. Macroscopically, two consecutive warming–cooling cycles were detected during this period of time: cooling from 1867 to 1910; warming from 1910 to 1945; cooling from 1945 to 1974; and warming from 1974 to nowadays. Warming rates of 0.17 and 0.22 °C per decade were measured during the warming sub-periods and cooling rates of ?0.14 and ?0.10 °C per decade were measured during the cooling sub-periods. The present warming period is on the same order of magnitude although slightly more intense than the one observed from 1910 to 1945, which is consistent with previous analysis carried for the North Atlantic. Finally, the thermal amplitude defined as the difference between the maximum and minimum annual values has increased since 1974 at a rate of 0.06 °C per decade due to the different increasing rates of the maximum (0.26 °C per decade) and minimum (0.20 °C per decade) SSTs.