Distributions and risk assessment of heavy metals in solid waste in lead-zinc mining areas and across the soil, water body, sediment and agricultural product ecosystem in their surrounding areas

To identify the root causes of heavy metal contamination in soils as well as prevent and control such contamination from its sources,this study explored the accumulation patterns and ecological risks of heavy metals like Cd and Pb in solid waste in mining areas and across the water body,sediment,soil and agricultural product ecosystem surrounding the mining areas.Focusing on the residual solid waste samples in lead-zinc deposits in a certain area of Guizhou Province,along with samples of topsoils,irrigation water,river sediments,and crops from surrounding areas.This study analyzed the distributions of eight heavy metals,i.e.,Cd,As,Cr,Hg,Pb,Zn,Cu,and Ni,in the samples through field surveys and sample tests.Furthermore,this study assessed the contamination levels and ecological risks of heavy metals in soils,sediments,and agricultural products using methods such as the single-factor index,Nemerow composite index,and potential ecological risk assessment.The results indicate that heavy metals in the solid waste samples all exhibited concentrations exceeding their risk screening values,with 60%greater than their risk intervention values.The soils and sediments demonstrate slight and moderate comprehensive ecological risks of heavy metals.The single-factor potential ecological risks of heavy metals in both the soil and sediment samples decreased in the order of Hg,Cd,Pb,As,Cu,Zn,Cr,and Ni,suggesting the same sources of heavy metals in the soils and sediments.Most of the agricultural product samples exhibited over-limit concentrations of heavy metals dominated by Cd,Pb,Ni,and Cr,excluding Hg and As.The agricultural product assessment using the Nemerow composite index reveals that 35%of the agricultural product samples reached the heavy metal contamination level,implying that the agricultural products from farmland around the solid waste dumps have been contaminated with heavy metals.The eight heavy metals in the soil,sediment,and agricultural product samples manifested high coefficients of variation(CVs),indicating pronounced spatial variability.This suggests that their concentrations in soils,sediments,and agricultural products are significantly influenced by human mining activities.Additionally,the agricultural products exhibit strong transport and accumulation capacities for Cd,Cu,and Zn.

Seasonal Dynamics of Nitrogen and Phosphorus in Water and Sediment of A Multi-level Ditch System in Sanjiang Plain,Northeast China

The multi-level ditch system developed in the Sanjiang Plain,Northeast China has sped up water drainage process hence transferred more pollutants from farmlands into the rivers of this region.Understanding the seasonal dynamics of nitrogen (N) and phosphorus (P) transportation in the ditch system and the role of different ditch size is thus crucial for water pollution control of the rivers in the Sanjiang Plain.In this study,an investigation was conducted in the Nongjiang watershed of the Sanjiang Plain to study the nutrient variation and the correlation between water and sediments in the ditch system in terms of ditch level.Water and sediments samples were collected in each ditch level in growing season at regular intervals (once per month),and TN,NO 3--N,NH 4+-N,TP,and PO 4 3--P were analyzed.The results show that nutrient contents in water were higher in June and July,especially in July,the contents of TN and TP were 3.21mg/L and 0.84mg/L in field ditch,4.04mg/L and 1.06mg/L in lateral ditch,2.46mg/L and 0.70mg/L in branch ditch,1.92mg/L and 0.63mg/L in main ditch,respectively.In August and September,the nutrient contents in the water were relatively lower.The peak value of nutrient in ditch water had been moving from the field ditch to the main ditch over time,showing a remarkable impact of ditch system on river water environment.The nutrient transfer in ditch sediments could only be found in rainfall season.Nutrient contents in ditch sediment had effect on that in ditch water,but nutrients in ditch water and sediments had different origination.Ditch management in terms of the key fac-tors is hence very important for protecting river water environment.

The diffusive fluxes of inorganic nitrogen across the intertidal sediment-water interface of the Changjiang Estuary in China

Ammonium and nitrate concentrations were analyzed in near-bottom water and pore water collected from ten stations of the intertidal flat of the Changjiang Estuary during April, July, November and February. The magnitudes of the benthic exchange fluxes were determined on the basis of concentration gradients of ammonium and nitrate at the near-bottom water and interstitial water interface in combination with calculations of a modified Fick＇ s first law. Ammonium fluxes varied from - 5.05 to 1.43 μg/（ cm^2·d） and were greatly regulated by the production of ammonium in surface sediments, while nitrate fluxes ranged from - 0. 38 to 1.36 μg/ （ cm^2·d） and were dominated by nitrate concentrations in the tidal water. It was found that ammonium was mainly released from sediments into water columns at most of stations whereas nitrate was mostly diffused from overlying waters to intertidal sediments. In total, 823.75 t/a ammonium-N was passed from intertidal sediments to water while about 521.90 t/a nitrate-N was removed from overlying waters to intertidal sediments. This suggests that intertidal sediments had the significant influence on modulating inorganic nitrogen in the tidal water.

The Research and Application of BP Neural Networks in River-basin Water and Sediment

Based on the basic principles of BP artificial neural network model and the fundamental law of water and sediment yield in a river basin, a BP neural network model is developed by using observed data, with rainfall conditions serving as affecting factors. The model has satisfactory performance of learning and generalization and can be also used to assess the influence of human activities on water and sediment yield in a river basin. The model is applied to compute the runoff and sediment transmission at Xingshan, Bixi and Shunlixia stations. Comparison between the results from the model and the observed data shows that the model is basically reasonable and reliable.

Spatial variations of bacterial community composition in sediments of the Jiaozhou Bay,China

Spatial variations of sediment microbes pose a great challenge for the estimation of anthropogenic influence on biogeochemical processes,yet remain very unclear in coastal ecosystems.Surface sediments in 9 stations from the eutrophic Jiaozhou Bay,China,were sampled,DNA was extracted within the sediments,and the 16 S rDNA was sequenced with the Illumina Hiseq sequencing.Results reveal considerable heterogeneity of sediment bacteria in the Jiaozhou Bay,of which Proteobacteria and Bacteroidetes accounted for over 75%.Bacterial alpha-diversity indices decreased generally from the outside to the inner part of the bay and from the offshore to the nearshore area.Bacterial community structures of S3,S4,S7,and S8 clustered,those of S5,S13,and S14 grouped together,while those of S6 and S10 were distinct from each other and from those of the other stations.Major class Gammaproteobacteria were more abundant at the stations with mesoeutrophic to eutrophic levels(S4,S5,S8,and S10)and less abundant at oligotrophic stations(S6,S13,and S14),while Deltaproteobacteria had an opposite distribution pattern.Overall,bacterial community composition transitioned from being Xanthomonadales-dominant at S4 and S8 to being unidentifedGammaproteobacteria-dominant at S5,S6,S13,and S14,while in other stations there were comparable orders.The biogeochemical processes correspondingly changed from being nitrogen cycling-dominant at S4 and S8 to being sulfur cycling-dominant at S5,S6,S13,and S14.The bacterial distribution patterns were especially affected by the factors(dissolved organic phosphorus,DOP)in the overlying seawater due to the habitat status of P-insu fficiency in the bay.Both orders Xanthomonadales and Alteromonadales could serve as bioindicators of anthropogenic pollution to different pollution types.At last,divergent distribution patterns of individual bacterial populations in the bay were revealed,the influential environmental gradients were clarified,and the uncertainty of microbes was reduced,helping to predict environmental functions in coastal areas.

Numerical Study on Seasonal Transportation of the Suspended Sediments in the Modern Yellow River Mouth Effected by the Artificial Water and Sediment Regulation

Since 2002, an artificial water and sediment regulation(AWSR) has been carried out, which largely reduced water and sediment discharged from the Yellow River into the Bohai Sea. Although the sediment transport in the Yellow River Mouth(YRM) has been observed and modeled intensively since AWSR, but preferentially for the non-storm conditions. In this study, a three-dimensional current-wave-sediment coupled model, DHI-MIKE numerical model, was used to examine the seasonal suspended-sediment transport in the YRM after the AWSR. Results show that the seasonal distribution of suspended-sediments in the YRM is dominated by wind and wave rather than river input. The major transport pathway of suspended-sediments is from the western Laizhou Bay to the Bohai Strait during the winter monsoon, especially in storm events. In addition, about 66% of the river sediments deposit within 30 km of the YRM, which is smaller than previous estimations. It suggests that the YRM has been eroded in recent decades.

1986-2018年黄土丘陵区典型小流域不同水文年水沙变化

[目的]探讨黄土丘陵区罗玉沟典型小流域水沙变化趋势以及不同水文年径流输沙对水土流失治理的响应差异,量化降水和人类活动对流域水沙影响的相对贡献,以期为黄土丘陵第三副区流域水土流失治理和水资源管理提供参考。[方法]基于罗玉沟流域1986—2018年的降雨、径流、输沙等数据,采用Mann-Kendall检验法、累积距平法及双累积曲线法分析流域水沙变化趋势及驱动因素。[结果]1986—2018年罗玉沟流域河流由常流河转变为季节性河流,干河日数显著上升(p<0.01),2000年以来干河日数多在300 d以上;同期,罗玉沟流域径流输沙显著下降(p<0.05),与基准期1986—1993年相比,1994—2007年减水减沙率分别为61.9%,44.3%,2008—2018年径流输沙分别减少67.5%,76.4%;在2008—2018年平水年和枯水年间罗玉沟流域输沙模数分别为(1 080.0±107.5) t/km^(2),(167.8±111.4) t/km^(2),而在暴雨频发丰水年,输沙模数仍接近4 000 t/km^(2);流域产流产沙能力降低,水沙关系发生改变,相同径流条件下输沙量减少,即流域径流含沙量水平降低,开始变清;相比降雨变化而言,人类活动是流域水沙变化的主导因素,1994—2007年人类活动对减水减沙的贡献率分别为83.3%和79.5%,而2008—2018年人类活动的贡献率分别为91.8%,94.4%,表明流域水沙变化受人类活动影响越来越大,其中,坡改梯及退耕还林还草工程是主要影响因素。[结论]因沟道治理工程建设不足,罗玉沟流域在丰水年因沟道重力侵蚀导致流域输沙仍然剧烈,因此,需要加强沟道治理进一步减少流域水土流失。

降雨-波浪-水位对库岸崩滑泥沙空间分布影响

库岸崩滑对库区含沙量有显著影响,掌握崩滑泥沙与水文因素的关系有助于分析库区泥沙的淤积过程和输移规律.通过降雨-波浪-水位多因素耦合模型试验分析了崩滑泥沙在不同水文因素作用下的空间分布规律.结果表明,降雨能减弱含沙量的变化幅度,促使悬移质泥沙颗粒细化.降雨后含沙量平均变异系数降幅为22%,极细砂粒含量降幅为53%.波浪可加大离岸方向库区含沙量,同时降低此方向含沙量变异系数.波浪作用下离岸方向的平均含沙量增幅为78%,含沙量平均变异系数降幅为67%.水位升高促使离岸方向和水深方向的含沙量降低,悬移质泥沙颗粒粗化.离岸方向和水深方向的平均含沙量在水位升高时降幅分别为14%和20%,极细砂粒含量增幅为15%.

赫章土法炼锌区水-沉积物重金属污染的时空变化特征

对赫章土法炼锌区河流水体和沉积物重金属污染状况及时空变化特征进行了研究。结果表明,水体和沉积物受到多种重金属污染:地表水体中Pb、Zn、Cd的均值分别为137.19×10-3、1 919.38×10-3、14.21×10-3 mg.L-1,分别是地表水环境质量标准Ⅲ类水质标准的2.74、1.91、2.84倍;沉积物中Cu、Pb、Zn和Cd的均值分别为702.79、3 242.8、5 427.6、32.19 mg.kg-1,分别是土壤环境质量标准三级标准的1.76、6.49、10.86、32倍。水体和沉积物中Cu、Pb、Zn和Cd沿河流总体呈无规律性的变化,受炼锌废渣堆和铅锌选矿厂影响的地点,水体和沉积物重金属含量均较高,污染严重。近10年来,炼锌区河流水体和沉积物重金属污染仍然很严重,水体重金属污染呈加重特征,沉积物中Pb、Zn污染呈减轻趋势,Cd和Cu污染则加重。

2007-2017年府谷-龙门段河道冲淤特征及其动力机制

[目的]河道演变是水流、泥沙与河床边界相互作用的结果,对水利工程的安全、洪涝灾害的防控有显著的影响。黄河中游府谷-龙门段位于晋陕峡谷地带,以黄土高原沟壑侵蚀地貌为主,流经的黄土高原地区是黄河泥沙的主要来源,因此研究该河段的河道冲淤特征及影响因素对控制黄河中游水土流失有重要意义。[方法]基于府谷、吴堡、龙门3个典型水文站径流泥沙及河道断面数据,分析了2007-2017年府谷-龙门段河道冲淤特征及相关影响因素。[结果](1)近11年来府谷-龙门段河道整体表现为冲刷,其中府谷-吴堡段表现为河道冲刷量逐渐减小,吴堡-龙门段表现为河道冲刷逐年加剧。(2)府谷-吴堡段呈水减沙增的趋势,吴堡-龙门段整体表现为水多沙少,两河段河道冲淤量与水流含沙量变化同步。(3)府谷-吴堡段悬移质泥沙中值粒径呈增加趋势,河道冲刷变缓;吴堡-龙门段悬移质泥沙中值粒径呈减小趋势,加剧河道侵蚀。(4)府谷站入黄泥沙量增加,河道侵蚀力降低,河道冲刷变缓;吴堡站入黄泥沙量减少,河道侵蚀力增强,河道处于冲刷的状态。[结论]径流泥沙的变化在很大程度上影响了府谷-龙门段河道冲淤。在生态环境有所改善的背景下,研究该河段河道冲淤特征及动力机制对进一步减少中游地区水土流失、预防中下游洪涝灾害具有重要的意义。

分层小水库沉积物-水界面热交换时空变化特征

通过对分层小水库沉积物和上覆水温度剖面的7次监测,计算沉积物-水界面的热交换通量,探讨沉积物与水之间热量交换的时空变化特征。结果表明:沉积物-水界面热交换通量具有明显的季节变化,在春夏季库水升温分层以及秋季降温混合时期由库水向沉积物传递热量;冬季由沉积物向库水释放热量。浅水区水温的日变化促使沉积物-水热交换具有明显日变化特征。库区内由于水深不同,热交换特征也存在空间差异,与坝前相比,水库中心水深较浅,春季热交换方向转变的时间早;水库中心夏季由水传向沉积物的最大热通量(106. 6 W/m2)高于坝前深水区(23. 8 W/m2)。夏季当水体透明度较高时,沉积物直接接受太阳辐射引起热交换方向改变为由沉积物向水传递。

南方主要河流水沙变化及人类活动的影响

为了解我国南方河流的水沙变化及主要成因,利用Mann-Kendall检验法和水文量累积曲线法,分析了南方主要河流代表站径流量和输沙量的变化特征,探讨了影响南方河流水沙变化的主要因素。结果表明,长江、珠江、钱塘江和闽江等南方河流代表站年径流量都没有显著的变化态势;除钱塘江代表站外年输沙量都有显著减少趋势;钱塘江2016—2020年为平水平沙期,2011—2020年为平水多沙期,其他河流2016—2020年和2011—2020年均为平水少沙期;影响南方河流水沙变化的人类活动包括水库拦沙、水土保持措施、河道采砂、流域过度建设等,其中水库拦沙是南方河流减沙的主要措施,水土保持措施在南方河流减沙过程中发挥了重要作用,河道采砂对河道减沙也发挥了一定的作用。

羊信江流域水沙变化特征及其影响因素

为深入研究水沙变化对流域生态修复和经济可持续发展的影响,利用Mann-Kendall非参数趋势检验法、Pettitt突变检验法、Spearman秩相关系数法、累积量斜率变化率比较法对赣江上游羊信江流域1964—2020年的降雨量、径流量和输沙量的变化特征及其贡献率进行分析,确定影响流域输沙量变化的主要因素。结果表明:①羊信江流域在1964—2020年年降雨量和年径流量无显著变化,年输沙量呈显著增加趋势;②降雨量、径流量及输沙量年内分配不均,均多集中在汛期(3—6月份);③年降雨量、年径流量均未发生显著突变,年输沙量在1995年发生显著突变(P<0.01);④降雨和人类活动对输沙量增加的贡献率分别为-0.35%、100.35%。以稀土矿开采、脐橙种植、跨河公路修建为主的人类活动是导致羊信江流域水土流失的重要原因。研究成果对流域种植结构调整及矿产资源绿色开放具有重要的指导意义。

冲刷及整治工程叠加作用下武汉河段滩槽调整特征与成因

大型水库的修建引起了坝下游的滩槽调整,进而对河势、航运、防洪及生态等产生显著影响。为探究滩槽调整的驱动机制,采用1952—2022年水沙和1959—2021年地形观测资料,以长江武汉河段为例,分析了床沙组成、来水来沙及整治工程等因素的影响。研究表明:①武汉河段枯水河槽冲刷量占全河槽冲刷量的90.4%,断面趋向窄深化,河相系数减小。不同江心洲及汊道冲淤出现差异性调整,2001—2021年,铁板洲和白沙洲洲体面积分别减少了63.1%和61.5%,潜洲和天兴洲洲体面积分别增大了212.3%和14.5%;2013年后,铁板洲左右汊均冲,天兴洲汊道左淤右冲。②来沙量锐减,河床以0.125 mm≤d<0.25 mm的细沙居多,抗冲性较弱,是冲刷加剧的先决条件;三峡水库的削峰补枯作用加剧了枯水倾向汊河的冲刷幅度;整治工程改变了滩槽冲淤的横向分布,是江心洲差异性调整的主导因素,也是天兴洲保持左淤右冲的重要原因。③三峡水库蓄水前,洲滩之间演变联动性强;三峡水库蓄水后,来沙减少和中水期时间延长导致洲滩冲刷萎缩,洲滩之间演变联动性变弱;整治工程实施后,工程保持了心滩稳定且其缓流滞沙效应提高了抗冲性,心滩淤长的同时限制了边滩发育,叠加来沙进一步减少,边滩之间、心滩之间演变联动性进一步变弱,边滩与心滩之间演变联动性再次增强。

黄河北干流水沙时空变化特征及协调性分析

为了解黄河北干流河段径流和输沙的时空变化规律及趋势,基于2002—2021年黄河北干流水沙数据,采用Mann-Kendall检验、突变点检验、小波分析、水沙关系协调性分析等方法,对黄河北干流河段的头道拐、龙门、潼关3个水文站2002—2021年的水沙时空变化特征进行了分析。结果表明:黄河北干流河段的输沙年内不均匀程度和集中度均大于径流,并且年内特征变化更加显著;各站径流集中期主要出现在9月,而输沙集中期主要在8月和9月;流域内水沙变化的显著突变年份多发生在2005年和2017年,可能与近年大型水利工程的调控影响相关;3个水文站水沙序列主要时间尺度对应的周期分别为13、10、9 a;黄河北干流的水沙不协调性在2008年之前主要表现为水少沙多,而在2008年之后则表现为水多沙少,其中头道拐的来沙系数始终小于0.009,一直处于水多沙少的状态。总体上,研究期内黄河北干流河段径流量在不断上升,而输沙量明显减少,且随着时间的推移水多沙少的趋势愈发显著。

水沙变化条件下不同边界弯曲河道演变特征研究

弯曲河道具有迂回曲折的外形和蜿蜒蠕动的动态特征,其形成、发展和演变是受多种因素综合影响的复杂过程。为研究水沙变化条件下弯曲河流的河道演变特征,采用自然模型法在室内水槽中塑造出相对自然的弯曲河道,设置有、无护岸措施两种工况进行模型试验。结果表明:在有护岸措施条件下,河道纵剖面上游段冲刷下切、下游段变化不大,河道整体比降呈减小趋势,河道深泓弯曲度减小,其演变响应特性对含沙量的变化更敏感;在无护岸措施条件下,河道滩槽演变调整作用较强,纵剖面呈整体式下切,且下游段纵剖面下切幅度较上游段大,河道深泓弯曲度逐渐增大,其演变响应特性对流量的变化更敏感。弯曲河道发生演变的实质是变化的水沙条件与河道形态调整之间相互适应的过程,演变的最终趋势是河道的形态结构与水沙条件达到相互协调的平衡状态。

鄱阳湖流域水沙变化及出湖水沙模拟研究

自20世纪50年代以来,鄱阳湖流域气候发生显著变化,人类活动日益频繁,降水、产流能力和产沙能力都发生了明显变化。基于鄱阳湖流域“五河”入湖控制站以及湖口水文站数据,运用Mann-Kendall检验法和双累积曲线法确定了年输沙量突变时间点,再利用累积量斜率变化分析法量化降水、产流能力和产沙能力对鄱阳湖入湖沙量的影响;在此基础上,提出了变分模态分解、LSTM神经网络和完全逐步抽样技术等多方法耦合的水沙模拟模型及其评价方法,并建立了研究区域鄱阳湖湖口站水沙模拟模型。研究结果表明:不论是“五河”入湖沙量变化,还是湖区泥沙淤积量变化,以降水变化为代表的气候变化因素对其影响较小,主要影响还是来自人类活动因素;但在具体的变化规律上却存在差异,人类活动对入湖沙量的贡献率呈上升趋势,但对同期鄱阳湖湖区淤积沙量的影响贡献率则呈现先降后升的趋势。水沙模拟分析表明,湖口站出湖月径流量、出湖月输沙量的模拟过程与实测过程较为吻合,取得了较高模拟精度,湖口、星子站水位对模拟精度的提升贡献较小。

长江中游荆江河段河道深泓纵剖面时空演变规律

深泓线的演变规律对于揭示冲积河流河床演变与河势调整具有重要意义。为探明三峡水库蓄水运用后荆江河段深泓纵剖面的变化规律,基于2002—2020年173个观测断面的深泓高程资料,对比分析18年内深泓线高程的时空变化,并结合来水来沙情况剖析其变化原因。结果表明,2002年以来荆江河段河道深泓纵剖面普遍冲刷下切,2008年之后深泓高程下切幅度进一步加大,但在来水来沙较多时会出现回淤现象。2002—2020年上荆江枝城至新厂河段平均冲刷深度达4.62 m,下荆江河道冲淤交替频繁,然而上荆江相对冲淤强度为10%,小于下荆江,其主要原因是枝江河段河床组成为粗沙和卵石,在一定程度上限制冲刷的发展,下段为沙质河床,较易受到冲刷。

局部淤堵排水管道水力冲击特性的CFD模拟研究

在市政排水管道中,长时间运行会导致排水管道发生局部淤堵,降低过流能力,对排水管道正常运行产生影响.本文针对存在局部淤堵的圆形截面排水管道构建了水汽两相流数值模型,利用CFD手段模拟研究了非恒定入流边界下的局部淤堵排水管道水力特性,量化分析了不同初始条件下淤积或障碍物的受力情况.结果分析表明:在干管初始条件下,冲击瞬间障碍物受力达到最大值,该冲击力可用射流公式近似计算,相对误差小于10%;而在湿管条件下,水流对于障碍物的冲击力相较干管有显著下降.此外在湿管条件下,障碍物受水流冲击的强度还与初始条件下障碍物的淹没条件密切相关.

石羊河流域不同时间尺度水沙变化研究

全球气候变暖和人类活动的双重作用,导致河流水沙状况发生变化。分析降水、输沙变化和人类活动的水沙效应,可为流域水资源管理提供决策依据。文章以石羊河流域杂木寺和九条岭两个水文站1956—2016年水沙数据为基础,采用Mann-Kendall法、双累积曲线、滑动t检验等方法分析流域年降水、水沙变化趋势及突变年份,利用累积量斜率变化率比较法分析水沙变化的驱动因素,研究结果表明:(1)杂木寺年输沙量呈下降趋势,降水量年际变化较大,但总体下降趋势较显著;九条岭水文站年输沙量呈波动上升趋势,降水量年际变化较大,但总体上升趋势较显著。(2)杂木寺站降水量和输沙量的突变年份分别为2007年、2012年;九条岭站降水量和输沙量的突变年份为1966年、2005年。(3)对流域水沙变化的驱动力分析发现,杂木寺站降水变化和人类活动对输沙量的贡献率分别为13.8%和86.2%(1973—2011年),2.73%和97.77%(2021—2016年)。九条岭站降水变化和人类活动对输沙减少的贡献率分别为6.63%和93.37%。分析水沙变化规律及原因,可为流域水土保持及灌溉等地区决策提供更加有力的支撑。