Underground River System Research Articles

Controlling factors of underground river system of karst region in Pacitan Regency, East Java

One of the interesting karst areas is the Pegunungan Sewu, because of the existence of an underground river system that developed below it. The underground river system of Bribin in Gunung Kidul, Yogyakarta is one of the evidence found by previous researchers. In Pacitan District there are karst landscapes that have not been widely studied. Pacitan karst area is in the eastern part of the karst area of Pegunungan Sewu. As the characteristics of the karst region in general, in the Pacitan karst region, there are small hills, vertical hole, closed depressions, rough and pointed surface outcrops, stalactites and stalagmites, and the presence of muddy and water sources. The Pacitan karst area is similar to the Gunung Kidul karst area which has an underground river system. However, the development of underground river systems from these two regions is thought to be different. The purpose of this study is to analyze typical and the controlling factors that influence the development of underground river systems in the Pacitan karst area, East Java. This research was conducted using VES (Vertical Electrical Sounding). The results showed that the typical underground river system that develops in the area of research is more shallow than in Gunung Kidul and suspected to be in the Vadose and it is controlled by the movement of water from the incoming surface through rock fractures.

Sources of Nitrate in Groundwater and Its Environmental Effects in Karst Trough Valleys: A Case Study of an Underground River System in the Longfeng Trough Valley, Chongqing

Water samples from the two underground rivers (Fenghuang River and Longju River) and samples of the dry and wet deposition of atmospheric dissolved inorganic nitrogen were taken from the Longfeng karst trough valley located in the Zhongliang mountain in the suburbs of Chongqing from May 2017 to April 2018. Anions, cations, δ15 N(NO3-), δ18 O(NO3-), δ18 O(H2O), and δ13C(DIC) isotope data were used to investigate the NO3- source and its environmental effects. The results showed:① The hydrochemistry of the two underground rivers is of the type HCO3-Ca. The NO3- concentration varied from 17.58 to 32.58 mg·L-1, with an average of 24.02 mg·L-1, and was slightly higher in rainy season than the dry season, revealing that the underground rivers were polluted. ② The δ15 N(NO3-) value ranged from -3.14‰ to 12.67‰, with an average value of 7.45‰. The δ18 O(NO3-) value ranged from -0.77‰ to 12.05‰ with an average value of 2.90‰, and was higher in the dry season than the rainy season, indicating that animal excreta and domestic sewage were main NO3- sources throughout the year. In addition, rainfall, fertilizer, and soil nitrogen were the NO3- sources during the rainy season. There are no significant differences between the NO3- sources of the two underground rivers, and nitrification is the main nitrogen conversion process. ③ The molar ratio of (Ca2++Mg2+)/HCO3- varied from 0.65 to 0.82. That of the Fenghuang River was 0.75 and that of the Longju River was 0.70. The δ13C(DIC) value ranged from -12.46‰ to -9.20‰, with a mean of -11.10‰ in the Longju River and -10.72‰ in the Fenghuang River. These values indicated that the HNO3 derived from the nitrification of NH4+ was involved in the weathering of carbonate rocks. ④ HNO3 dissolved carbonate rocks and aggravated the chemical weathering of carbonate rock in the basin, contributing 8% of the DIC in groundwater, and 9% and 7% in Fenghuang River and Longju River, respectively.

Reassignment of 'Triplophysa' jiarongensis (Cypriniformes: Nemacheilidae) to Oreonectes Günther, 1868.

Specimens identified as Oreonectes jiarongensis (Cypriniformes: Nemacheilidae) were collected from a karst cave in Jiarong Town and Banzhai Township, Libo County, Guizhou, China. Several lines of morphological and molecular evidence suggested that this species was similar to species of Oreonectes Günther 1868 and not closely related to species of Triplophysa Rendal, 1933. The anterior and posterior nostrils of 'Triplophysa' jiarongensis were separated by a short distance, and there was no secondary sexual dimorphism in male specimens. The Bayesian phylogenetic analysis based on cytochrome b recovered 'T.' jiarongensis in a well-supported clade with Oreonectes daqikongensis, O. shuilongensis, O. furcocaudalis and O. platycephalus, sister to the Triplophysa clade. In addition, the genetic distances between 'T.' jiarongensis and species of Oreonectes were low (O. daqikongensis: 0.114; O. shuilongensis: 0.106; O. platycephalus: 0.180), while distances to species of Triplophysa were higher (T. dorsalis: 0.233; T. yarkandensis: 0.282). Therefore, we reassign 'T.' jiarongensis to Oreonectes. Based on this result, it is now clear that species of both Oreonectes and Triplophysa inhabit the same underground river system in Guizhou. However, as species of Oreonectes are only known from the southern part of Guizhou, it may be that O. jiarongensis inhabits the most northerly part of the range of this genus.

Groundwater Flooding due to Tropical Cyclone Cempaka in Ngreneng Karst Window, Gunungsewu Karst Area, Indonesia

Tropical Cyclone Cempaka occurred on November 27, 2017 in the Indian Ocean, just south of Central Java. This incident induced high rainfall leading to flash floods in the southern part of Central Java, including Gunungsewu Karst Area. The highest rainfall recorded on November 28, 2017, in this area was 239 mm/day (Automatic Rainfall Recorder/ARR Station in Pindul Cave) and 341 mm/day (ARR Station in Tepus). The extreme rainfall also caused groundwater flood in Ngreneng Karst Window. This study aimed to analyze the mechanism of this flood. The results of the analysis showed that it was caused by water filling up the conduit passage in the entire Bribin-Baron underground river system. The flow of the conduit pushed the diffuse flow into the surface fast, and the water that came out of Ngreneng Karst Window was thereby clear. The inundation lasted for ten days and submerged up to 26.4 ha of the study area.

Transport of polycyclic aromatic hydrocarbons in a highly vulnerable karst underground river system of southwest China.

The concentration and fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated in a karst underground river system in southwest China. Groundwater, particles, and sediments from underground river, topsoil, and surface water were monitored, allowing establishment of a conceptual model of PAH transport at the watershed scale. The results showed that PAHs could be transported from the surface to the subsurface through two migration pathways, which were slow-flowing water in the karst fissure and fast-flowing water in conduits. During rainfall events, increasing PAH levels (concentrations and fluxes) at the underground river exit indicated that hydrodynamic force could facilitate PAH transport. The PAHs in water were dominated by dissolved PAHs, accounting for 58.7% of total, especially in the freely dissolved phase, in which SPM-associated PAHs accounted for 41.3% of the total PAHs. Low molecular weight PAHs dominated transport and were mainly transported in dissolved form, whereas high molecular weight PAHs were dominated by SPM-associated transport during the rainfall events. A significantly positive correlation was observed between two-ring and three-ring freely dissolved PAHs and dissolved organic carbon (p < 0.01), respectively. Moreover, PAHs with four to five rings were relatively more abundant in the dissolved organic matter (DOM) associated phase than in the freely dissolved phase, suggesting a major role of DOM in their transport during rainfall events. The trend of PAH fluxes suggested that particle-facilitated transport was another dominant cause of PAH mobilization.

Nitrate-Nitrogen Pollution Sources of an Underground River in Karst Agricultural Area Using 15N and 18O Isotope Technique

The objectives of this study were to reveal the sources of nitrate and the ratio of karst in an agricultural basin based on a 15N and 18O isotope technique and quantitative calculation of the IsoSource model. From May to October 2017, six sampling points in the Qingmuguan river basin, Chongqing, were monitored every 24 d. Results showed that there was a great risk of nitrate pollution in the underground river system, because most NO3--N concentrations of the sampling points exceeded the threshold. Spatially, NO3--N concentrations in the underground river increased from upstream to downstream. Temporally, NO3--N concentrations of Fishpond and Yankou Ponor upstream and Jiangjia Spring downstream were impacted by agricultural fertilizer from May to June and fluctuated from June to September due to precipitation. With decreased agricultural activities, NO3--N concentrations gradually decreased after September. NO3--N concentrations were high in midstream soil water. Daluchi, in the middle and lower reaches, maintained relatively low NO3--N concentrations with stable fluctuations. Dual 15N and 18O isotopic compositions suggested that the upstream nitrates were derived from soil organic nitrogen and a mixture of manure and sewage. The midstream nitrates originated from soil organic nitrogen and NH4+ from fertilizer and rain. Nitrates in the middle and lower reaches were derived from the mixing of manure and sewage, soil organic nitrogen, and NH4+ from fertilizer and rain. Jiangjia Spring, the outlet of the underground river, was seriously polluted by nitrates. It is believed that soil organic nitrogen, NH4+ in fertilizer and rain, the mixing of manure and sewage, and NO3- in precipitation were the main nitrate sources in the outlet. Nitrate source contribution of the outlet was calculated with the IsoSource model. The calculation results showed that manure and sewage, soil organic nitrogen, NH4+ in fertilizer and rain, and NO3- in precipitation contributed 46.4%, 32.6%, 18.6%, and 2.4%, respectively.

Sources and contamination characteristics of PAHs in environmental media in a karst underground river system (southern China)

The aim of this study was to determine the sources and contamination characteristics of polycyclic aromatic hydrocarbons (PAHs) in various environmental media in a karst underground river system. For this purpose, air, underground river water, sediment, and soil samples were collected from a typical underground river in southern China in the dry and wet seasons of 2013–2014, and the compositional spectra, distribution, and ratio characteristics of 16 PAHs were determined for comparative analysis. The results show that three 2–3-ring PAHs (naphthalene, phenanthrene, and fluoranthene) mainly occur in air and underground river water. In sediments and soils, 4–6-ring PAHs are the main components. The PAH concentrations in the air in the wet season are clearly greater than those in the dry season, while it is the opposite in the underground water. Seasonal differences in the concentration of PAHs in the sediments and soils are minor. The concentrations of PAHs in the environmental media overall showed variation in the following order: upstream < midstream < downstream, and this is related to pollutant discharge, adsorption, etc. The main source of PAHs in the upstream area is the combustion of grass, wood, and coal, while it is petroleum in the midstream area, and combustion of grass, wood, coal, and petroleum near the outlet of the underground river. It is necessary to change the energy structure in the study area, improve the efficiency of environmental protection facilities, reduce the emission in vehicle exhaust, and control pollution by PAHs at their sources.

Paleogeomorphology restoration and the controlling effects of paleogeomorphology on karst reservoirs: a case study of an ordovician-aged section in Tahe oilfield, Tarim Basin, China

The Tarim Basin is the largest petroliferous basin in northwestern China and contains the Tahe oilfield, the highest hydrocarbon enrichment in the entire basin. Paleogeomorphology has important controlling effects on carbonate reservoir development. Using core data, thin sections and drilling, logging and seismic data, paleokarst was identified and analyzed. The paleogeomorphology of the top low-middle Ordovician was recovered following a comprehensive utilization of the impression and residual thickness methods in combination with unconformity identification. Based on the filling thickness and residual thickness, the karst paleogeomorphic units were classified, and their controlling effects on reservoirs analyzed. The second-order paleogeomorphic units primarily include four types: karst highland, karst gentle⁃slope, karst steep⁃slope and karst basin. The karst gentle⁃slope and karst steep⁃slope are further classified quantitatively into third-order paleogeomorphic units (monadnock, tableland, karst terrace and trench). The results show that the development of the karst reservoir differed in different geomorphic units. In the karst gentle slope, the favorable areas for karst reservoir development are the karst terrace, tableland, monadnock, and the ends and flanks of trench. In the karst steep⁃slope, the karst terrace and tableland are favorable areas. In the vertical vadose and phreatic zones of the gentle-slope region, a large number of caves and underground river systems developed, but in the steep-slope region, only a small number of shafts and isolated caves are observed. This study plays an important role in oil and gas exploration and development.

Perunutan aliran sungai bawah tanah dalam rangka pengembangan sumber daya air daerah karst

Tracer technique is widely known as one of the methods used to find the relationship between the cave or underground river system in karst areas of South Blitar. In karst area of south blitar karst areas a number of water sources such as springs, underground river, and some streams out into the South Sea trace connections amongtracing the flow of underground river using tracer technique has been implemented with the aim to obtain data and information on flow systems around Umbul Tuk caves, so that water resources can be further developed as a value-added utilization of raw water supply in Blitar. Testing was conducted using artificial tracer material in the form of common salt NaCl and measurements were performed using a measuring instrument electrical conductivity (EC ). The measurement results indicate the existence of an underground river channel that connects Rowo with Umbul Tuk, with a flow rate of Umbul Tuk canal towards the South Sea of 360 l/s (March 2012), which has the potential to be exploited. Utilization of this flow, in addition to the needs of local people, and potentially also for fulfilling the needs of the new tourism in Pangi coast of the South Sea, which at present is still not developed.

The effects of agricultural activities and atmospheric acid deposition on carbonate weathering in a small karstic agricultural catchment, Southwest China

In order to quantify the sources and fluxes of DIC, the effects of the use of N-fertilizers and acid deposition on carbonate weathering have been quantified by hydrochemistry and δ13CDIC of groundwater in Qingmuguan underground river system (QURS) – a small karstic agricultural catchment of Southwest China. The results show that: (1) the significant temporal variations for major element concentrations and δ13CDIC of groundwater in different months were observed, especially, of which the groundwater showed significant high concentrations of DIC, Ca2+, Mg2+, NO3−, SO42− and δ13CDIC in rainy season and fertilizing period in the QURS; (2) the contributions of carbonate dissolution by carbonic acid to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 68.5 % and 81.0 %, respectively. While the contributions of carbonate dissolution by nitric acid originated from the use of N-fertilizers and atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 11.1 % and 6.7 %, respectively, and the contributions of carbonate dissolution by sulphuric acid originated from the atmospheric acid deposition to total concentrations of (Ca2++Mg2+) and HCO3− of groundwater in different months averaged 20.4 % and 12.3 %, respectively; (3) the δ13CDIC increased obviously with (Ca2++Mg2+)/HCO3− of groundwater in the rainy season and fertilizing period indicated that the use of N-fertilizers and atmospheric acid deposition should be responsible for the elevated the δ13CDIC and the molar ratio of (Ca2++Mg2+)/HCO3− of groundwater in the QURS.Key words: carbonate weathering, karst groundwater, agricultural activities, atmospheric acid deposition, Qingmuguan, Southwest China.

Comparison on the Hydrogeochemical Characteristics of Typical Karst Groundwater System in Southwest China, a Case of Qingmuguan and Laolongdong in Chongqing

To study the hydrogeochemical characteristics of southwestern typical karst underground river influenced by different land-use types and human activities, underground rivers of Qingmuguan and Laolongdong, which have similar geological background in Chongqing, were contrastively analyzed from the scale of monthly and rainfall event variation. By the means of independent t-test and principal component analysis(PCA), the results showed that ions of Ca2+, HCO3-, Mg2+, K+, NO3-, Na+, SO42-, Cl- and conductivity were distinctly different at the outlet of the two observed underground rivers, Jiangjia spring and Laolongdong. Compared with Laolongdong, Jiangjia spring showed larger monthly variation range and mean concentrations of K+, NO3-, but ions of Na+, SO42-, Cl- showed an opposite trend. Water-rock interaction played an important role in the hydrogeochemical characteristics and variations of two observed karst underground rivers. Qingmuguan underground river was mainly affected by agricultural activities, while Laolongdong underground river was dominantly influenced by urban and industrial activities. Owing to the difference in manner and intensity of human activities, the two observed karst underground river systems responded differently during a single rainfall event. The variation of water chemical indicators that highly corresponded to discharge at Jiangjia spring were relatively disordered at Laolongdong. It was shown that the hydrogeochemical characteristic of Qingmuguan was primarily influenced by soil erosion and agricultural activities, followed by water-rock interaction, while the hydrochemical characteristic of Laolongdong was dominantly influenced by water-rock interaction, followed by urban activities, industrial activities and soil erosion.

Characterization of recharge and flow behaviour of different water sources in Gunung Kidul and its impact on water quality based on hydrochemical and physico-chemical monitoring

Karst aquifers are important water resources but highly vulnerable due to their heterogeneous and complex characteristics. Various hydrological aspects (recharge, flow behaviour) have to be known in detail to develop a sustainable concept for water collection, distribution and treatment. In the karst area of Gunung Sewu (Java, Indonesia) such a concept was to be implemented within a German–Indonesian joint IWRM project. The basic hydrogeological conditions and water quality aspects were characterized on a regional scale through hydrochemical monitoring of springs, wells, subsurface and surface rivers. More detailed information about the recharge, flow and storage behaviour was obtained from high resolution monitoring of T, EC and discharge in one large underground river system. The water quality is well below any guideline values with regard to inorganic pollutants during dry season. During rainy season, dissolved Al concentrations are frequently above the Indonesian guideline value. Slow matrix flow is the most important recharge component during dry season, thus assuring the year-round water availability in the subsurface karst. During rainy season, quick infiltration of the surface water is a dominant recharge component. Rapid response of discharge, T and EC to heavy rain suggests the presence of point recharge that feeds a highly karstfied conduit system with fast conduit flow and short transit time of water. The strong variations in discharge and hydrochemistry are particularly challenging for technical water usage and treatment facilities. Piston flow is indicated to be the third important flow component and is induced by heavy rainfall.

Polycyclic aromatic hydrocarbon contamination in a highly vulnerable underground river system in Chongqing, Southwest China

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were investigated in the water, sediment and topsoil of the Laolongdong underground river system (LURS) of Chongqing, Southwest China. The total concentrations of PAHs ranged from 81.5 to 8089ng/L in water, from 58.2 to 1070ng/g in sediment, and from 277 to 3301ng/g in topsoil. These levels of PAHs are relatively low compared to other karst areas. Low molecular weight (LMW) PAHs were dominant in water, sediment, topsoil samples, and high molecular weight (HMW) PAHs were more common in topsoil and sediment. The high levels of LMW PAHs in groundwater and sediment suggested relatively recent local sources of PAHs that were transported into the aquifer via wastewater discharge and surface water leakage. The similar composition of PAHs in topsoil and sediment samples suggested that the sediment originated from topsoil and that PAHs in sediment and topsoil had similar origins. The source of PAHs contamination was diagnosed by using PAH isomer ratios and a principal component analysis (PCA) method. The results indicated that PAHs mainly originated from vehicles, coal combustion and petrogenic sources. Significant correlations of PAHs with total organic carbon (TOC) in topsoil and sediment indicated that TOC was an important factor affecting PAHs content.

Pathways and hydrography in the Mesoamerican Barrier Reef System Part 2: Water masses and thermohaline structure

Hydrographic data from two oceanographic cruises conducted during March 2006 and January/February 2007 are used to investigate the thermohaline structure related to the observed circulation along the Mesoamerican Barrier Reef System (MBRS). From our observations we identify three water masses in the MBRS: the Caribbean Surface Water (CSW), North Atlantic Subtropical Underwater (SUW), and Tropical Atlantic Central Water (TACW). Little vertical structure in temperature is observed in the upper 100m of the water column, but important differences are observed in the salinity distribution both horizontally and with depth. Freshwater inputs to the system from the mainland can be traced in the surface layer, with two possible sources: one from surface rivers located along the southern portion of the MBRS, and the other originating from an underground river system located along the northern portion of the MBRS. The thermohaline structure in the MBRS reflects the dynamics of the observed circulation. Uplifted isopycnals along most of the central and northern coastline of the MBRS reflect the effects of the strong geostrophic circulation flowing northward, i.e. the Yucatan Current. To the south along the MBRS, much weaker velocities are observed, with the Honduras Gyre dominating the flow in this region as presented during January/February 2007. These two regions are separated by onshore and divergent alongshore flow associated with the impingement of the Cayman Current on the shore and the MBRS.

Hexachloro benzene in the Nanshan Karst systems, China

Karst areas have much higher ecological vulnerability and are easy to be contaminated with hexachlorinated benzene (HCB) which is introduced as health risk pollutants. HCB concentrations were used to understand the transport of HCB conducted in the Nanshan karst system, China. Water, sediments from the underground river and water, sediments and soil from the surface systems were collected monthly in 2011 - 2012 and HCB were analyzed. The levels of HCB were 19.9 ng L-1 in underground waters and 11.6 ng g-1 in underground sediments while 99.1 ng L-1 in surface waters and 110.5 ng g-1 in surface sediments and 2.8 ng g-1 in soils. Seasonal variations were found in concentrations of HCB both in the waters and the sediments. HCB concentrations varied from 7.8 ng L-1 in winter to 86.9 ng L-1 in spring in the groundwaters and 0.3 ng g-1 in autumn to 36.7 ng g-1 in spring in the underground sediments. HCB concentrations varied from 38.6 ng L-1 in autumn to 1019.8 ng L-1 in spring in the surface waters, 0.7 ng g-1 in autumn to 133.4 ng g-1 in spring in the surface sediments and 2.5 ng g-1 in autumn to 17.4 ng g-1 in winter in soil. The substantial seasonal variation found between underground system and surface system which indicate that the surface systems play major role for the transport and contamination of HCB in the underground river systems due to karst features.Bangladesh J. Sci. Ind. Res. 50(2), 109-116, 2015

Hydrogeochemical processes and vulnerability of a typical karst underground river system, southwest China

This study presents an investigation of the hydrogeochemical processes and potential vulnerability of a typical underground river system in southwest China. Physical and chemical data were collected from both traditional manual sampling and continuous automatic monitoring. Analysis of high-frequency monitoring data from the outlet spring, Jiangjiaquan spring (JJQ), of the underground river system suggests the existence of several physico-chemical processes with distinctive characteristic response to storm events. Due to the impacts of sources and migration influencing factors, seasonal variations of major chemical components of the outlet spring are much different. For the entire karst watershed, spatial variability of surface and subsurface water geochemistry was significantly influenced by land use and lithologic characteristics. Principal component analysis (PCA) reveals that agricultural activities, water-rock interactions and soil erosion are potential influencing factors and the main sources for the chemical composition of JJQ spring. Nutrients from agricultural activities can be brought into the underground river by ways of diffuse recharge from leaching of soils, as well as focused recharge from surface flow via sinkholes. Water-rock interactions in the karst aquifer provide the evidence of diffuse recharge that contributed to groundwater quality. Soil erosion mainly causes focused recharge of contaminated water with particulate matters including iron, manganese and aluminum that carried into the underground river from sinkholes via surface flow.

Karst conduit hydro-gradient nonlinear variation feature study: case study of Zhaidi karst underground river

Through the analysis of monitoring data with a time interval of 10 min during the rainy season of 2012, for three points of G37, zk8 and zk7 which are located on the main conduit of Zhaidi karst underground river system, the variation features of water level and hydraulic gradient are studied and the relations are established between gradient and water level or amplitude. (1) It is first discovered that there are different function relations such as linear, parabola and inverse parabola between the G37’s water level and the hydraulic gradients of different conduit part. (2) The peak delay times for water level curves are <50 min and the maximum conducting speed of water press is faster than 13,020 m/h. (3) The upstream and downstream karst conduits have corresponding enlarging and shrinking amplitude function by the coefficients of 1.899/km and 0.125/km. (4) The gradient I variation is still linear to the level difference ΔH made by nine rainstorms. The conclusion and the methods of this paper have significance on the study of the regulation and storage capacity and groundwater resources evaluation of karst underground-river system.

The influence of light attenuation on the biogeomorphology of a marine karst cave: A case study of Puerto Princesa Underground River, Palawan, the Philippines

Karst caves are unique biogeomorphological systems. Cave walls offer habitat for microorganisms which in-turn have a geomorphological role via their involvement in rock weathering, erosion and mineralisation. The attenuation of light with distance into caves is known to affect ecology, but the implications of this for biogeomorphological processes and forms have seldom been examined. Here we describe a semi-quantitative microscopy study comparing the extent, structure, and thickness of biocover and depth of endolithic penetration for samples of rock from the Puerto Princesa Underground River system in Palawan, the Philippines, which is a natural UNESCO World Heritage Site.Organic growth at the entrance of the cave was abundant (100% occurrence) and complex, dominated by phototrophic organisms (green microalgae, diatoms, cyanobacteria, mosses and lichens). Thickness of this layer was 0.28±0.18mm with active endolith penetration into the limestone (mean depth=0.13±0.03mm). In contrast, phototrophs were rare 50m into the cave and biofilm cover was significantly thinner (0.01±0.01mm, p<0.000) and spatially patchy (33% occurrence). Endolithic penetration here was also shallower (<0.01mm, p<0.000) and non-uniform. Biofilm was found 250m into the cave, but with a complete absence of phototrophs and no evidence of endolithic bioerosion.We attribute these findings to light-induced stress gradients, showing that the influence of light on phototroph abundance has knock-on consequences for the development of limestone morphological features. In marine caves this includes notches, which were most well-developed at the sheltered cave entrance of our study site, and for which variability in formation rates between locations is currently poorly understood.

Fecal sterols, seasonal variability, and probable sources along the ring of cenotes, Yucatan, Mexico

Rapid development in Yucatan has had a dramatic impact on the environment, especially the water supply. Groundwater is the only source of water in Yucatan, since surface water is virtually absent due to the karstic nature of the soil. The ring of cenotes (RC) is a geological feature which functions as a source of water and as nodes in the underground river system that canalizes water towards the coast. Numerous productive and domestic activities take place around the RC in the absence of wastewater treatment or sewage systems. Consequently, a number of researchers have hypothesized that pollutants could migrate from the land surface to the underlying aquifer and, eventually, to the coast. Therefore, the present study investigates the relationship among sources of fecal sterols and their levels in cenotes, using the expected levels of fecal sterols obtained by a spatial analysis of the sources and a Pollution Source Index. Accordingly, expected levels are compared with the detected levels of fecal sterols in 5 areas around the RC. Regarding levels, observed during a sampling campaign carried out along the RC during September 2011 (rainy season) and May 2012 (dry season), varied from low to high concentrations of sterols (0.5–2396.42μgg−1) and fecal sterols (0.3–1690.18μgg−1). These concentrations showed no relationship between neighboring cenotes, where similar fecal sterol concentrations or gradients were expected. When comparing expected fecal sterols levels with the detected ones, only two of the five analyzed areas concur, suggesting that no clear relationship exists among sources and fecal sterols levels at the regional scale. Multivariate analysis showed that fecal sterols were associated with sterols and fine grain particulates during the rainy season, which suggests co-transport. During the dry season, fecal sterols associated with fine grain particulate and organic matter, which indicates a change to a deposition phenomenon. These findings indicate that defining a relationship among sources and fecal sterols levels is highly difficult and this could be the result of the absorption or migration through an intricate conduit, crack, or fracture karst system. Nevertheless, the “source-levels approach”, used in this study, was consistent for the northeast edge and the middle western part of the RC. New and more extensive research should be done to assess the environmental fate of fecal sterols, especially considering the intricate karstic system and its compound retention capacity.

Sources and transports of organochlorine pesticides in the Nanshan underground river, China

Karst areas have much higher ecological vulnerability and are prone to be contaminated. Organochlorine pesticides (OCPs) were detected in waters and sediment from the two sites of the karst Nanshan underground river system, China, to understand the sources and transport of OCPs in the underground river systems. Obviously, seasonal variations were found both in the waters and the sediments. Detected OCPs ranged from 61 to 936 ng L−1 in the groundwaters and 51–3,842.0 ng g−1 in the underground sediments, respectively. OCPs in groundwaters were mixture of younger and older residues from commercial sources. The maximum OCPs in the sediments of the underground river were historically older residues from commercial sources. The sources of OCPs in the waters and sediments of the underground river indicated that the surface systems play an important role in OCPs transport and pollution in the underground river. Karst features were liable for the transport behavior.