Distribution characteristics of size-fractionated chlorophyll a, primary production and new production in the Laizhou Bay, July 1997

The distributions of chlorophyll a concentration, primary production and new productionwere observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there were marked features of spatial zonation in the surveyed area, due to the differences between the geographic environment and the hydrological conditions. Chlorophyll a, primary production and new production were all higher in spring tides than that in neap tides in the Laizhou Bay. The highest values of these parameters were encountered in the central regions of the bay. At most stations, chlorophyll a concentrations at the bottom were higher than that at the surface. The results of size-fractionated chlorophyll a and primary production showed that contributions of nanocombining pi-coplankton ( <20 μm) to total chlorophyll a and primary production were dominant in phytoplankton community biomass and production of the Laizhou Bay. The environmental factors, primary production and new production in the Laizhou Bay are compared with other sea areas.

The size-fractionated chlorophyll a and primary productivity in the Bering Sea during the summer of 2003

Investigations of chlorophyll a and primary productivity were carried out inthe Bering Sea along the BR line and the BS line during the Second Chinese National Arctic ResearchExpedition in the summer of 2003. The results showed that the surface chlorophyll a concentrationswere 0.199～1.170 μg/dm^3, and the average value was 0.723 μg/dm^3 on the BR line. For the BSline, the surface chlorophyll a concentrations were 0.519～4.644 μg/dm^3 (average 1.605 μg/dm^3)and 0.568～14.968 μg/dm^3 (average 5.311 μg/dm^3) during the early and late summer, respectively.The average value in the late summer was much higher than that in the early summer. The high values(more than 4.0 μg/dm^3) occurred at stations of the BS line in the southern Bering Strait. Thechlorophyll a concentrations in the subsurface layer were higher than those in the surface layer.The results of the size-fractionated chlorophyll a showed that the contribution of the picoplanktonto total chlorophyll a was the predominance at the early summer and the contribution of thenetplankton was the predominance at the late summer. The carbon potential primary productivitiesvaried between 0.471 and 1.147 mg/(m^3·h) on the BR line, with average rates of 0.728 mg/(m^3·h).The primary productivities on the BS line were much higher than those of the BR line, ranging from1.227 mg/(m^3·h) at the early summer to 19.046 mg/(m^3·h) at the late summer. The results of thesize-fractionated primary productivity showed that the contribution of the nanoplankton to totalproductivity was the predominance at the early summer and the contribution of the netplankton waspredominance at the late summer. The assimilation number of photosynthesis was 0.45～2.80 mg/(mg·h)in the surveyed stations.

Distribution characteristics of size-fractionated chlorophyll a and primary productivity in Beibu Gu

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Variability of size-fractionated phytoplankton standing stock in the Amundsen Sea during summer

The size-fractionated composition of phytoplankton greatly influences the transfer efficiency of biomass in pelagic food chains and the biological carbon flux from surface waters to the deep sea.To better understand phytoplankton abundance and composition in polynya,ice zone,and open ocean regions of the Amundsen Sea Sector of the Southern Ocean(110°W-150°W),its size-fractionated distribution and vertical structure are reported for January to February 2020.Vertical integrated(0-200 m)chlorophyll(Chl)a concentrations within Amundsen polynya regions are significantly higher than those within ice zone(t test,p<0.01)and open ocean(t test,p<0.01)regions,averaging 372.3±189.0,146.2±152.1,and 49.0±20.8 mg·m^(−2),respectively.High Chl is associated with shallow mixed-layer depths and near-shelf regions,especially at the southern ends of 112°W and 145°W.Netplankton(>20μm)contribute 60%of the total Chl in Amundsen polynya and sea ice areas,and form subsurface chlorophyll maxima(SCM)above the pycnocline in the upper water column,probably because of diatom blooms.Net-,nano-,and picoplankton comprise 39%,32%,and 29%of total Chl in open ocean stations,respectively.The open-ocean SCM migrates deeper and is below the pycnocline.The Amundsen Sea SCM is moderately,positively correlated with the euphotic zone depth and moderately,negatively correlated with column-integrated net-and nanoplankton Chl.

Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring

During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chi a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be found. Chlorophyll a concentration vertically decreased from surface to bottom in the Liaodong Gulf and the Bohai Gulf, while it increased in the Laizhou Bay, the strait and the central region of the Bohai Sea, and the highest value was encountered at the bottom. Size-fractionation results showed that nano - combining pico -plankton ( < 20 μm) predominated in phytoplankton communities of the Bohai Sea during late spring. The average contribution to total Chl a in each station ranged 76% -95 % (mean is 87 %). The contribution of net (> 20 μm), nano - (2- 20 fan) and picoplankton (< 2 μm) was 13% , 63% and 24% to total production, and 9% , 53% and 38% to total Chl a, respectively. It proved the importance of nano - and pico -plankton in phytoplankton communities in the Bohai Sea e-cosystems. In this paper the factors, such as light intensity and zooplankton grazing pressure, governing standing stock and production of phytoplankton in the Bohai Sea were also discussed.

The distribution feature of size-fractionated chlorophyll a and primary productivity in Prydz Bay and its north sea area during the austral summer

The investigation of size-fractionated chlorophyll a and primary productivity were carried out in three longitudinal sections (63°-69°12'S, 70°30'E, 73°E and 75(30'E) at December 18-26, 1998 and January 12-18, 1999 in Prydz Bay and its north sea area, Antarctica. The results showed that surface chlorophyll a concentration were 0. 16 -3. 99 μg dm-3. The high values of chlorophyll a concentration (more than 3.5 μg dm -3) were in Prydz Bay and in the west Ladies Bank. The average chlorophyll a concentration at sub-surface layer was higher than that at surface layer; its concentration at the deeper layers of 50 m decreased with increasing depth and that at 200 m depth was only 0. 01 -0. 95μg dm -3. The results of size-fractionated chlorophyll a showed that the contribution of the netplanktion to total chlorophyll a was 56% , those of the nanoplankton and the picoplankton were 24% and 20% respectively in the surveyed area. The potential primary productivity at the euphotic zone in the surveyed area was 0. 11 - 11. 67 mgC m-3h-1 and average value was 2.00 ±2.80 mgC m h . The in-situ productivity in the bay and the continental shelf was higher and that in the deep-sea area was lower. The assimilation number of photosynthesis was 1.53±1. 11 mgC/(mg Chi a · h). The results of size-fractionated primary productivity show that the contribution of the netplanktion to total productivity was 58% , those of the nanoplankton and the picoplankton were 26% and 16% respectively. The cell abundance of phytoplankton was 1. 6 × 103 - 164. 8 × 103 cell dm-3 in the surface water.

Variability of size-fractionated chlorophyll a in the high-latitude Arctic Ocean in summer 2020

The size structure of phytoplankton has considerable effects on the energy flow and nutrient cycling in themarine ecosystem,and thus is important to marine food web and biological pump.However,its dynamics in the high-latitude Arctic Ocean,particularly ice-covered areas,remain poorly understood.We investigated size-fractionated chlorophyll a(Chl a)and related environmental parameters in the highly ice-covered Arctic Ocean during the summer of 2020,and analyzed the relationship between Chl adistribution and water mass through cluster analysis.Results showed that inorganic nutrients were typically depleted in the upper layer of the Canada Basin region,and that phytoplankton biomass was extremely low(mean=0.05±0.18 mg·m^(−3))in the near-surface layer(upper 25 m).More than 80%of Chl a values were<0.1 mg·m^(−3) in the water column(0-200 m),but high values appeared at the ice edge or in corresponding ice areas on the shelf.Additionally,the mean contribution of both nanoplankton(2-20μm)(41%)and picoplankton(<2μm)(40%)was significantly higher than that of microplankton(20-200μm)(19%).Notably,the typical subsurface chlorophyll maximum(0.1 mg·m^(−3))was found north of 80°N,where the concentration of sea ice reached approximately 100%.The Chl aprofile results showed that the deep chlorophyll maximum of total-,micro-,nano-,and picoplankton was located at depth of 40,39,41,and 38 m,respectively,indicating that nutrients are the primary factor limiting phytoplankton growth in the ice-covered Arctic Ocean during summer.These phenomena suggest that,despite the previous literatures pointing to significant light limitation under the Arctic ice,the primary limiting factor for phytoplankton in summer is still nutrient.

Size-fractionated phytoplankton biomass in autumn of the Changjiang(Yangtze) River Estuary and its adjacent waters after the Three Gorges Dam construction

A cruise was undertaken from 3rd to 8th November 2004 in Changjiang(Yangtze) River Estuary and its adjacent waters to investigate the spatial biomass distribution and size composition of phytoplankton.Chlorophyll-a(Chl-a) concentration ranged 0.42-1.17 μg L-1 and 0.41-10.43 μg L-1 inside and outside the river mouth,with the mean value 0.73 μg L-1 and 1.86 μg L-1,respectively.Compared with the Chl-a concentration in summer of 2004,the mean value was much lower inside,and a little higher outside the river mouth.The maximal Chl-a was 10.43 μg L-1 at station 18(122.67°E,31.25°N),and the region of high Chl-a concentration was observed in the central survey area between 122.5°E and 123.0°E.In the stations located east of 122.5°E,Chl-a concentration was generally high in the upper layers above 5 m due to water stratification.In the survey area,the average Chl-a in sizes of >20 μm and <20 μm was 0.28 μg L-1 and 1.40 μg L-1,respectively.High Chl-a concentration of <20 μm size-fraction indicated that the nanophytoplankton and picophytoplankton contributed the most to the biomass of phytoplankton.Skeletonema costatum,Prorocentrum micans and Scrippsiella trochoidea were the dominant species in surface water.The spatial distribution of cell abundance of phytoplankton was patchy and did not agree well with that of Chl-a,as the cell abundance could not distinguish the differences in shape and size of phytoplankton cells.Nitrate and silicate behaved conservatively,but the former could probably be the limitation factor to algal biomass at offshore stations.The distribution of phosphate scattered considerably,and its relation to the phytoplankton biomass was complicated.

Size-fractionated uranium isotopes in surface waters in the Jiulong Estuary in China

Surface water was collected from the Jiulong Estuary for determination of activity concentrations of uranium isotopes in different size fractions, namely, greater than 53, 10 -53, 2 - 10, 0.4 -2 μm, 10 000 u -0.4 μm and less than 10 000 u fractions by microfihration and cross-flow uhrafiltration technologies. Results indicated that most of the dissolved uranium （ 〈 0.4 μm） exis- ted in the low molecular mass fraction （ 〈 10 000 u）, and the colloidal uranium-238 （10 000 u -0.4 μm） only contributed less than 1% of the dissolved uranium-238. The fractions of colloidal uranium in the dissolved phases decreased with the increasing sa- linity. A positive linear relationship between uranium-238 activities and salinities was observed for the dissolved, colloidal and low molecular mass fractions, indicating a conservative behavior of uranium in the Jiulong Estuary. In the particulate phases （ 〉 0.4 μm）, the partitioning of uranium isotopes among different size fractions was controlled by the partitioning of particle concentrations. In the regions with salinities below 20, the partitioning of uranium-238 among different size fractions was as follows： 10 - 53 μm 〉 2 - 10 μm 〉 0.4 - 2 μm greater than above 53 μm. However, the order at the offshore station with salinities above 30 changed as follows ： 0.4 - 2 μm 〉 10 - 53 μm 〉 2 - 10 μm greater than above 53 μm. The fraction of the 0.4 - 2 μm particles increased at the offshore station, suggesting the increased contribution of the authigenic uranium. The activity ratio of uranium-234 to uranium-238 in the dissolved phases, including the low molecular mass fraction and the colloidal fraction, was larger than unity, showing the occurrence of excess uranium-234. In contrast, the activity ratio of uranium-234 to uranium-238 in all size fractions of the particulate phase was close to the equilibrium value （1.0）. The observed different values of the activity ratio of uranium-234 to uranium-238 in the dissolved phase and the particulate phase were ascribed to the preferential leaching of uranium-234 and the small amount of the leaching particulate uranium. The mass ratio of thorium-232 to uranium-238 also showed different values between the dissolved phase and the particulate phase. Mass ratio of thorium-232 to uranium-238 in the dissolved, colloidal and low molecular mass fractions was less than unity, while those in the different size fractions of particulate phases were larger than unity, reflecting a different behavior between uranium and thorium during their transport into the ocean.

Seasonal export fluxes of size-fractionated particulate derived from polonium-210: A case study in Xiamen Bay

Size-fractionated 210Po and 210Pb, in the size fractions >0.4 μm, >2 μm and >10 μm, were examined to determine the seasonal variability of particulate fluxes in Xiamen Bay. Good correlations between 210Po and particulate organic carbon (POC) or non-Particulate Organic Matter (nPOM) suggested that 210Po can be used to trace the export fluxes of POC and nPOM. Both steady-state (SS) model and nSS model were used to evaluate fluxes of size-fractionated 210Po, results showed that nSS model was better than the SS model in coastal areas. Based on the nSS model, size-fractionated POC fluxes decreased with increasing particle size. For the particle size studied, maximum POC fluxes occurred in autumn, followed by spring, winter, and summer. Fluxes of nPOM were an order of magnitude higher than the corresponding size-fractionated POC fluxes. Differences between size-fractionated nPOM fluxes indicated that hydrodynamic conditions were the main factor regulating transportation of particulate out of the inner Bay. In winter most particulates, including >10 μm particles, were transported under the strongest hydrodynamic conditions. In contrast, only a fraction of the <2 μm particulates were transported from the inner Bay in spring. This study suggested that 210Po is a powerful tracer of seasonal particulate export in coastal seas.

Size-fractionated Chlorophyll α biomass in the northern South China Sea in summer 2014

Spatial distribution of phaeopigment and size-fractionated chlorophyll a(Chl a) concentrations were examined in relation to hydrographic conditions in the northern South China Sea(NSCS) during a survey from 20 August to 12 September, 2014. The total Chl a concentration varied from 0.006 to 1.488 μg/L with a mean value of 0.259±0.247(mean±standard deviation) μg/L. Chl a concentration was generally higher in shallow water(<200 m) than in deep water(>200 m), with mean values of 0.364±0.311 μg/L and 0.206±0.192 μg/L respectively. Vertically, the maximum total Chl a concentration appeared at depths of 30–50 m and gradually decreased below 100 m. The size-fractionated Chl a concentrations of grid stations and time-series stations(SEATS and J4) were determined, with values of pico-(0.7–2 μm), nano-(2–20 μm) and micro- plankton(20–200 μm) ranging from 0.001–0.287(0.093±0.071 μg/L), 0.004–1.149(0.148±0.192 μg/L) and 0.001–0.208(0.023±0.036 μg/L), respectively. Phaeopigment concentrations were determined at specifi c depths at ten stations, except for at station A9, and varied from 0.007 to 0.572(0.127±0.164) μg/L. Nano-and pico-plankton were the major contributors to total phytoplankton biomass, accounting for 50.99%±15.01% and 39.30%±15.41%, respectively, whereas microplankton only accounted for 9.39%±8.66%. The results indicate that the contributions of microplankton to total Chl a biomass were less important than picoplankton or nanoplankton in the surveyed NSCS. Diff erent sized-Chl a had similar spatial patterns, with peak values all observed in subsurface waters(30–50 m). The summer monsoon, Kuroshio waters, Zhujiang(Pearl) River plume, and hydrological conditions are speculated to be the factors controlling the abundance and spatial heterogeneity of Chl a biomass in the NSCS.

Distribution and bioavailability of mercury in size-fractioned atmospheric particles around an ultra-low emission power plant in Southwest China

Ultra-low emission(ULE)technology retrofits significantly impact the particulate-bound mercury(Hg)emissions from coal-fired power plants(CFPPs);however,the distribution and bioavailability of Hg in size-fractioned particulate matter(PM)around the ULE-retrofitted CF-PPs are less understood.Here,total Hg and its chemical speciation in TSP(total suspended particles),PM_(10)(aerodynamic particle diameter≤10μm)and PM_(2.5)(aerodynamic particle diameter≤2.5μm)around a ULE-retrofitted CFPP in Guizhou Province were quantified.Atmospheric PM_(2.5)concentration was higher around this ULE-retrofitted CFPP than that in the intra-regional urban cities,and it had higher mass Hg concentration than other sizefractioned PM.Total Hg concentrations in PM had multifarious sources including CFPP,vehicle exhaust and biomass combustion,while they were significantly higher in autumn and winter than those in other seasons(P<0.05).Regardless of particulate size,atmospheric PM-bound Hg had lower residual fractions(<21%)while higher HCl-soluble fractions(>40%).Mass concentrations of exchangeable,HCl-soluble,elemental,and residual Hg in PM_(2.5)were higher than those in other size-fractioned PM,and were markedly elevated in autumn and winter(P<0.05).In PM_(2.5),HCl-soluble Hg presented a significantly positive relationship with elemental Hg(P<0.05),while residual Hg showed the significantly positive relationships with HCl-soluble Hg and elemental Hg(P<0.01).Overall,these results suggested that atmospheric PM-bound Hg around the ULE-retrofitted CFPP tends to accumulate in finer PM,and has higher bioavailable fractions,while has potential transformation between chemical speciation.

Seasonal variation of size-fractionated phytoplankton in the Pearl River estuary

To investigate the dynamics of phytoplankton size structure in the Pearl River estuary, concentrations of size-fractionated chlorophyll a (Chl a) were determined during four cruises carried out in 2008 and 2010. The distribution of Chl a in this geographical location showed a high degree of temporal variation. Chl a concentrations were highest in autumn, approximately three times higher than those in summer and winter. Microphytoplankton was the dominant contributor, accounting for 66.9% of the Chl a concentration in autumn 2008. In summer and spring 2008, nano-sized cells dominated the phytoplankton population throughout the study region. During the winter cruise, two different areas of water were found, characterized by (1) low salinity and high nutrient content and (2) high salinity and low nutrient content; nano- and picophytoplankton co-dominated the first area, while microphytoplankton dominated the second. It is arguable that grazing could have played a role in determining phytoplankton community size structure in winter. Nutrient concentrations were assumed not to limit phytoplankton growth during the investigation period. Size-differential capacity in competing for the resources available under different hydrodynamic conditions seemed to be the major factor in determining seasonal variation in the structure of the phytoplankton communities. High N:P ratios in the Pearl River estuary had major implications for nutrient pollution control. Our results indicated that studies of phytoplankton size structure provide greater insight into phytoplankton dynamics and are necessary to better manage water quality in the Pearl River estuary.

天然热释光测量技术在多年冻土区天然气水合物勘查中的应用

冻土区天然气水合物形成机理复杂,成因多源,发展多种捕捉微渗漏信息技术,提高勘查成功率是亟需解决的难题。本文首次把天然热释光测量技术应用于冻土区天然气水合物勘查中,利用RGD-6型热释光剂量仪测试了祁连山冻土区土壤样品热释光强度,总结出适用于木里冻土区天然气水合物勘查的加热程序,以及样品取样粒级。试验结果表明,祁连山冻土区土壤样品最佳取样粒级为-60~100目,最佳升温速率应设置为5℃/s,最佳升温区间为50~400℃。根据祁连山冻土区土壤天然热释光强度异常特征,圈定了天然气水合物在地表的异常边界,天然热释光强度异常模式为顶部异常,与烃类异常模式存在良好的对应关系。土壤天然热释光不受微生物的影响,灵敏度高,是一种很有前景的寻找天然气水合物的方法,在今后的冻土区天然气水合物资源勘查过程中可以将这种技术加以推广。

Using Natural Radionuclides to Trace Sources of Suspended Particles in the Lower Reaches of the Yellow River

Natural radionuclides are powerful tools for understanding the sources and fate of suspended particulate matter(SPM).Particulate matter with different particle sizes behaves differently with respect to adsorption and desorption.We analyzed the activi-ties and distribution characteristics of multiple natural radionuclides(238U,226Ra,40K,228Ra,7Be and 210Pbex)on size-fractionated SPM at the Lijin Hydrographic Station(Huanghe or Yellow River)every month over a one-year period.Results showed that medium silt(16–32µm)was the main component.As expected,the activity of each radionuclide decreased with an increase of particle size.We examined the sources of SPM with different particle sizes using activity ratios of 226Ra/238U,228Ra/226Ra,40K/238U and 7Be/210Pbex,and concluded that SPM with different particle sizes originated from different sources.Our results indicate that fine SPM(<32µm)was mainly from the erosion of soil along the lower reaches of the Yellow River,while coarse SPM(>32µm)was mainly derived from resuspension of riverbed sediment.During high runoff periods,the concentration of SPM increased significantly,and the pro-portion of fine particles originating upstream increased.Naturally occurring radioactive isotopes,especially on size-fractionated par-ticles,are therefore seen as useful tracers to understand the sources and behaviors of riverine particles transported from land to sea.

凡纳滨对虾大水面高盐养殖水体叶绿素a的变化及与环境因子的关系

“渔盐一体化”是山东省滨州市凡纳滨对虾(Litopenaeus vannamei)盐田养殖的重要模式。为了解该模式下养殖水体浮游植物的叶绿素a(Chl-a)浓度、粒径结构的变化特征及主要影响因子,于2021年5—7月分别在养殖的初期、中期和收获期,测定高盐组(S=54)和对照组(S=32)养殖水体的分级Chl-a浓度[小型浮游植物(micro Chl-a)、微型浮游植物(nano Chl-a)、微微型浮游植物(pico Chl-a)、总Chl-a浓度]及相关环境参数的日变化和月变化。结果显示,日变化:对于总Chl-a浓度,高盐组无显著日变化(P>0.05),对照组在5月和6月存在显著的日差异(P<0.05)。对于浮游植物粒径结构,高盐组7月的pico Chl-a日变化显著(P<0.05);对照组7月的micro Chl-a和6月的nano Chl-a日变化显著(P<0.05)。月变化:两盐度组pico Chl-a、nano Chl-a和total Chl-a最低值和最高值都分别出现在6月和7月。且7月的总Chl-a显著高于5月和6月(P<0.05)。高盐组水体中nanoChl-a占主要优势,随着养殖的进行粒径结构特性出现了演替,其中,picoChl-a对总Chl-a贡献率由5月的6.43%提高至7月的16.81%,超过了micro Chl-a的贡献率。对照组5月和6月以micro Chl-a占主要优势,分别占59.64%和57.49%,其次是nano Chl-a,分别占35.46%和36.90%,7月以nano Chl-a占主要优势,贡献率达53.09%。冗余分析(RDA)显示,Chl-a浓度与水温显著正相关,nanoChl-a的贡献率随温度升高而增加。高盐组总Chl-a浓度与硅酸盐浓度呈显著正相关,与磷酸盐、溶解有机氮、溶解有机磷浓度呈显著负相关;对照组总Chl-a与溶解有机氮显著正相关,与硅酸盐、亚硝酸盐浓度呈显著负相关。总体来讲,高盐组水体Chl-a浓度日变化较小,浮游植物粒级随养殖进行逐渐趋于小型化,可能与温度升高和较高的有机氮水平有关。

提升某高硫低铜品位铜硫矿铜浮选回收指标试验研究

安徽铜陵某铜硫矿浮选厂处理的原矿含铜0.34%,其中硫化铜占近93%,含硫31.26%,属于高硫低铜硫化矿。选厂铜回收率长期维持在82%~84%,明显低于原矿中硫化铜理论回收率。为提升该矿石中铜的回收,开展磨矿细度优化以及复合酯类捕收剂强化铜浮选的试验研究。结果表明,在磨矿细度-74μm占75%,使用复合酯类捕收剂的条件下,小型闭路试验获得铜精矿铜品位为16.43%,铜回收率达到94.07%的指标,较现场指标分别提高1个和9个百分点;通过对小试和现场产品的粒级组成深入分析,得出现场磨矿细度不足,磨矿产品粒度组成不均匀是造成铜损失在尾矿的关键原因。同时,小试结果证明使用新型复合酯类捕收剂可强化微细粒铜矿物的回收。为选厂在实际生产中提升指标提供了科学的方向和依据。

承压破碎无烟煤气体渗透特性影响因素实验研究

垮落带破碎煤岩体空隙结构演变直接影响垮落带气体渗透特性,进而影响废弃矿井采空区煤层气运移富集规律。利用自主设计研发的第二代破碎煤岩体压实-渗流-CT扫描试验系统,开展5种粒径破碎无烟煤在不同气体压力、轴向应力及空隙率条件下162组渗透实验。结果表明:(1)气体在破碎无烟煤中运移时气体压力、流量随时间一直处于动态变化直至达到吸附平衡,流量、压力恒定。(2)低雷诺数下气体在破碎无烟煤中流动需要拟启动压力梯度,其值处于158.89~1408.64 Pa/m,并随着轴压增大、空隙率减小而增大。(3)破碎无烟煤渗透率处于10^(-12)~10^(-10)m^(2),且渗透率随气体压力、空隙率增加分别呈现对数、指数函数式增长趋势。(4)颗粒粒径越大则相同装料空间内破碎煤样初始空隙越大,更易于气体流动,因此相同空隙率时破碎无烟煤渗透率随粒径的增大而增大;不同粒径颗粒渗透率平均变化幅度均随空隙率减小而减小;然而颗粒粒径越大,减小相同空隙率时破碎无烟煤渗透率变化幅度减小越明显。废弃矿井采空区煤层气地面抽采时,地面钻井应优先布设在垮落带破碎煤岩体连同纵向“高位环形裂隙体”共同构成的“U”型高渗煤层气富集区内。

某废弃冶炼场地土壤不同粒径组分重金属的特征及其对修复策略的启示

颗粒粒径组分对土壤重金属的分布与赋存具有重要影响,而当前对受冶炼活动影响的不同区域间土壤各粒径组分重金属分布的比较研究较少。本研究以某废弃铅冶炼场地为研究对象,选取三个土壤剖面(冶炼固废堆存区、交通区和邻近的农田),对比研究了不同土壤颗粒粒径组分(>150、45~150和<45μm)中重金属的地球化学分布特征及赋存形态。结果显示,冶炼场地与周边农田土壤各粒径组分重金属的分布特征具有明显差异。随着粒径的增大,冶炼固废堆存区土壤重金属的富集因子从0.78增至1.14,这与该区粗粒废渣的堆放与机械混合相关;而农田土壤重金属的富集因子从1.49降至0.60,这与冶炼过程释放富集重金属的细颗粒沉降有关。同时,冶炼场地土壤的较粗组分(>45μm)具有较高的重金属质量负载量(>50%),且废渣颗粒对土壤重金属的贡献显著,故物理分离技术可用于该场地的土壤污染修复。此外,石膏和莫来石可能是该场地受冶炼活动影响土壤的指示矿物。本研究将冶炼活动影响与土壤不同粒径组分重金属的赋存形态相关联,对修复策略具有一定的指导意义。

北京平原地区不同土地利用类型对土壤颗粒组成及其分形特征的影响

选取农田、撂荒草地、人工乔木林、人工灌木林和次生林5种不同土地利用类型土壤颗粒为研究对象,采用Microtrac S3500激光粒度仪测定土壤样品粒径,利用土壤分形学理论和方法,分析不同土地利用类型对土壤颗粒组成及其分形特征的影响。结果表明,土壤粒径在不同土地利用方式下存在显著差异,其中撂荒草地以砂粒为主,农田、人工乔木林、人工灌木林和次生林以粉粒为主;次生林、人工乔木林黏粒体积分数最大,且显著大于其他土地利用类型,撂荒草地最小;次生林、人工乔木林、人工灌木林粉粒体积分数最大,且显著大于农田与撂荒草地;砂粒体积分数则与粉粒相反。土壤分形维数的大小依次为撂荒草地<农田<人工灌木林<次生林<人工乔木林;土壤分形维数与土壤黏粒含量、粉粒含量均呈显著正相关,与土壤砂粒含量呈显著负相关。