Carbon cycle variability in tropical Atlantic across two Early Eocene hyperthermals

Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically light carbon to the ocean-atmosphere system.They serve as ancient analogs for understanding how the oceanic carbonate system and surface-ocean ecosystem would respond to ongoing and future climate change.Here,we present a continuous carbonate record across the Eocene Thermal Maximum 2(ETM2 or H1,ca.54.1 Ma)and H2(ca.54 Ma)events from an expanded section at Ocean Drilling Program Site 1258 in tropical Atlantic.The abundant calcareous nannofossils and moderate carbonate content throughout the studied interval suggest this record was deposited above the calcite compensation depth(CCD),but below the lysocline and under the influence of terrestrial dilution.An Earth system model cGENIE is used to simulate the carbon cycle dynamics across the ETM2 and H2 to offer insights on the mechanism of the rapid warming and subsequent recovery in climate and ecosystem.The model suggests moderate changes in ocean pH(0.1–0.2 unit)for the two scenarios,biogenic methane from a rechargeable methane capacitor and organic matter oxidation from thawing of the permafrost.These pH changes are consistent with a recent independent pH estimate across the ETM2 using boron isotopes.The carbon emission flux during the ETM2 is at least an order of magnitude smaller than that during the Paleocene–Eocene Thermal Maximum(PETM)(0.015–0.05 Pg C yr^(-1)vs.0.3–1.7 Pg C yr^(-1)).The comparable pre-and post-event carbonate contents suggest the lysocline did not over deepen following the ETM2 at this tropical Atlantic site,indicating spatial heterogeneity in the carbonate system due to strong dilution influence from terrestrial weathering and riverine discharge at Site 1258.

Influence of surface properties and antecedent environmental conditions on particulate-associated metals in surface runoff

Particulate-associated trace metals have been regarded as an important pollution source for urban surface runoff.Cd,Pb,Cu,Zn and total solids(TS)washed off two different surfaces(low-elevated facade and road surfaces)under two kinds of antecedent environmental conditions(dry and snow-melting)were determined in this study.Wet-vacuuming sweeping(WVS)and surface washing(SW)methods,representing the maximum pollution potential and common rainfall-induced wash-off condition respectively,were used to collect the particulate matters.The result shows that the wash-off concentrations of trace metals were found in the order of Cd(2.28±2.08 mg/l)<Pb(435.85±412.61 mg/l)<Cu(0.93±0.61 mg/l)<Zn(2.52±2.30 mg/l).The snow-melting process had a considerable influence on the wash-off concentrations of the trace metals on both road and facade surfaces.It reduced >38% and >79% of metals and TS concentrations in the facade surface and road surface runoff respectively.The wash-off concentrations of Cd,Cu,and Zn on the road surface 45e780% higher than those on the facade surfaces.The sensitivity analysis based on the Bayesian network indicates that the wash-off concentrations of metals were mainly dependent on the antecedent environmental conditions or the surface properties while the sampling methods had a minor influence.Therefore,to accurately model the pollutant migration in the surface runoff requires an improving method considering different surfaces and antecedent environment conditions.

Measuring performance of low impact development practices for the surface runoff management

Continuous urbanization over the last few years has led to the increase in impervious surfaces and stormwater runoff.Low Impact Development(LID)is currently receiving increased attention as a promising strategy for surface runoff management.To analyze the performance of LID practices for surface runoff management,a longterm hydrological modeling from 2001 to 2015 along with a cost-effectiveness analysis were carried out on a campus in Dresden,Germany.Seven LID practices and six precipitation scenarios were designed and simulated in a Storm Water Management Model(SWMM).A cost-effectiveness analysis was conducted by calculating the lifecycle costs and runoff removal rate of LID practices.Results demonstrated that the LID practices significantly contributed to surface runoff mitigation in the study area.The LID performance was primarily affected by the length of the precipitation scenarios and LID implementing schemes.The runoff removal rate of the LID practices fluctuated significantly when the rainfall scenario was shorter than 12 months.When the rainfall scenario exceeded 1 year the effects on the runoff removal rate was constant.The combination of an infiltration trench,permeable pavement,and rain barrel(IT+PP+RB),was the best runoff control capacity with a removal rate ranging from 23.2% to 27.4%.Whereas,the rain barrel was the most cost-effective LID option with a costeffectiveness(C/E)ratio ranged from 0.34 to 0.41.The modeling method was improved in this study by conducting long-term hydrological simulations with different durations rather than short-term simulations with single storms.In general,the methods and results of this study provided additional improvements and guidance for decision-making process regarding the implementation of appropriate LID practices.