Kara Lenorovitz

Environmental Geology Seminar

Agricultural Pollutants

Calamari, Davide; et al., 1991. Role of Plant Biomass in the Global Environmental Partitioning of Chlorinated Hydrocarbons. Environmental Science and Technology 25: 1489-1495.

Plants play a key role in global organochlorine contamination by bioaccumulating and transferring volatile contaminants between foliage and the atmosphere. Calamari, et al. globally sampled vegetation and analyzed organochlorine content to estimate tropospheric contamination and the global circulation of these estrogen mimicking chemicals. Foliar concentrations agreed well with previously measured atmospheric concentrations of hexachlorobenzenes (HCB), dichloro diphenyl trichloroethane (DDT) and hexachlorocyclohexanes (HCH). The distribution of compounds varied based on residence times and current uses. The more volatile chemicals, HCBs, were distributed ubiquitously, but showed slightly higher concentrations near the poles. This "cold condensation" effect results from an inverse relationship between temperature and concentration. Areas of lower temperatures, such as the poles and high elevation mountains, serve as sinks for highly volatile compounds. Less volatile molecules, such as DDTs, travel shorter distances in the atmosphere and are more concentrated near the equator. However, volatility alone could not predict global distribution patterns for DDT and HCH, which are in current use. Nonetheless, plant foliage did serve as an effective terrestrial monitor of global atmospheric contamination.

Calamari et al. present clear and interesting research concerning global organochlorine distribution. Unfortunately, my lack of statistical knowledge concerning C50 values and probits limited my understanding and ability to critique some of their findings. Statistics aside, however, this paper was well written and provided convincing evidence for global distillation and the need for accurate global pesticide use records.

Kucklick, John R.; et al., 1994. Organochlorines in the Water and Biota of Lake Baikal, Siberia. Environmental Science and Technology 28: 31-37.

While several studies have focused on organochlorine contamination in high latitude lakes in North America and Europe, few have investigated contamination in Asia. Kucklick et al measured organochlorine contamination in the Lake Baikal water column and food chain, and compared their results to representative studies in North America and Europe. Lake Baikal is a long, deep, rift lake with few trophic links located in central Siberia. The lake lacks significant local organochlorine sources and receives the majority of its pollution from atmospheric deposition. Kucklick et al sampled tissue from pelagic sculpin, omul and the Baikal seal, and collected water samples at three different sites along the length of the lake. The water and all of the animal tissue tested contained hexachlorohexane (HCH), dichloro diphenyl trichloroethane (DDT), polychlorinated biphenyl (PCB), toxaphene and chlordane at concentrations similar to concentrations found in other northern lake studies. In contrast to other study lakes, DDT concentrations in Lake Baikal were greater than its constituent breakdown products DDE and DDD. Also, PCBs and DDTs were more concentrated in the southern end of Lake Baikal. These findings may have resulted from a local source. While the United States and Canada have banned some of these chemicals, DDT, toxaphene and HCH are actively used in Asia and many developing countries. Kucklick et al noted that the organochlorine concentrations in the omul, sculpin and seal were directly related to their solubility in lipid phases. Unfortunately, this relationship has dire consequences for predators and human populations dependent on Lake Baikal as a food source.

Kucklick et al present a strong study that serves as a good counterpart to investigations in the United States and Europe. The paper was interesting, but the data presentation was challenging to interpret and the text focused heavily on procedures. The research could have been better substantiated by broader sampling and greater replication.

Larsson, Per; Okla, Lennart; Woin, Per, 1990. Atmospheric Transport of Persistent Pollutants Governs Uptake by Holarctic Terrestrial Biota. Envrionmental Science and Technology 24: 1599-1601.

The atmosphere readily transports chlorinated hydrocarbons globally and delivers them to industrialized, developing and remote areas via wet and dry deposition. Cold temperatures greatly enhance this deposition of volatile organic pollutants. Therefore, arctic regions receive a greater proportion of chlorinated hydrocarbon contamination then regions at lower latitudes. Larsson et al. examined the relationship between atmospheric deposition of pollutants and uptake by the herbivorous vole, the predacious shrew and the predacious dragonfly. Concentration data elucidated a positive correlation between atmospheric deposition of PCB and DDT and concentrations in the herbivorous vole. Shrew pesticide uptake showed a direct relationship with PCB, DDT and lindane deposition, while dragonfly uptake correlated only with DDT and lindane. Larsson et al. explained the differences between the organisms were probably due to differing exposures and abilities to metabolize these organochlorine pollutants.

This brief paper adequately demonstrates a positive correlation between atmospheric deposition and uptake by terrestrial biota. However, the paper could have been strengthened by the presentation of more data. Furthermore, Larsson et al. fall short of acknowledging the magnitude of their findings concerning global pesticide contamination.

Loganathan, Bomanna G., 1994. Global Organochlorine Contamination Trends: An Overview. Ambio 23: 187-191.

Loganathan reviews the trends of global organochlorine contamination by focusing on research in terrestrial, aquatic and oceanic ecosystems. Atmospheric transport stands out as one of the greatest factors in the global persistence of organochlorine pesticides. In terrestrial ecosystems, human PCB concentrations are increasing in developing countries and show no sign of decreasing in industrialized nations. Conversely, DDT body burdens are decreasing in industrialized nations while increasing in the Third World. Current researchers have employed plant foliage, and peat, soil and ice cores to monitor atmospheric transport of pesticides. Several studies on freshwater riverine fish indicate a disappearance of chemical contaminants corresponding with local bans. However, closed aquatic systems suffer from rapid and persistent contamination. Higher trophic levels carry the greatest contaminant burden due to magnified exposure and very slow metabolic breakdown. As might be expected, oceans serve as the "ultimate repository" for many of the less volatile organochlorine compounds. Despite the ban on DDT in many industrialized countries, oceanic DDT levels show no clear decline. Meanwhile, volatile organochlorine compound concentrations have remained steady in air masses above northern and southern oceans. Loganathan calls for long term investigations into the behavior of organochlorines in order to better understand and limit their dispersal.

Loganathan presents a well supported review of the current literature concerned with global organochlorine contamination. At the same time, the author also makes astute suggestions for possible further research and international policy decisions. His introduction is well written, intriguing and clear. However, his method of leaping from one study to the next leaves the reader hoping that the common threads of the studies could be neatly tied together. Nonetheless, Loganathan effectively advocates for a long-term global investigation of organochlorine concentration, distribution and behaviors in all representative environments. Furthermore, he takes a bold and much needed stance concerning international pesticide policy.

Simonich, Staci L.; Hites, Ronald A., 1995. Global Distribution of Persistent Organochlorine Compounds. Science 269: 1851-1854.

Simonich and Hites mapped the global distribution of twenty different pesticides by determining their concentrations in tree bark samples collected worldwide. Relative to other vegetative structures, tree bark covers a large surface area, is a persistent structure and contains a high concentration of lipids. These characters, in combination with the worldwide distribution of trees, make tree bark an excellent scavenger of atmospheric lipophilic organic pollutants. The authors expected the global distribution of pesticides to be governed by the global distillation effect, where more volatile compounds are more readily distilled and concentrated in higher latitudes. Almost all of the 20 pesticides, including those banned in industrialized countries, were found to be globally ubiquitous. Tree bark from developed countries and agricultural areas contained the highest pesticide concentrations. However, low, measurable concentrations of organochlorine compounds contaminated even remote areas. Hexachlorocyclohexanes (HCH), the endosulfans and a form of DDE were the most prevalent organochlorine contaminants. For the most volatile organochlorine pesticides, concentrations increased directly with increasing latitude; boreal and arctic regions were more contaminated than equatorial regions. Conversely, less volatile compounds showed little correlation with latitude. In addition to volatility, the authors concluded that chemical persistence and location and level of use control the global distribution of organochlorine pesticides.

Simonich and Hites present a clear assessment of current global organochlorine distribution, while also providing convincing evidence for global distillation. The addition of another figure showing volatility and global distribution would strengthen their arguments for a dependence on volatility. Furthermore, current pesticide use records would have added the missing element to their investigation. Overall, Simonich and Hites present clear, concise research while drawing attention to the need for an understanding of global organochlorine behavior.

Smith, William H.; et al., 1993. Trace Organochlorine Contamination of the Forest Floor of the White Mountain National Forest, New Hampshire. Environmental Science and Technology 27: 2244-2246.

Smith et al. Examined forest floor PCB and DDT contamination levels in and around the Hubbard Brook Experimental Forest in order to ascertain trace organic contamination of remote New England forests. Many atmospheric pollutants have been delivered to regions distant from pollution sources via atmospheric deposition. Contamination levels in forest floors may serve as an effective monitor for atmospheric pollution. Mean contamination loading for PCBs approximated 2.6 kg/ha, while DDT loading approximated 0.9 kg/ha. Unlike many other findings, DDT was more prevalent in the forest floor samples than the breakdown products DDE and DDD. The authors found no correlation between contamination levels and species composition, elevation, forest age, soil type, aspect or disturbance. Smith et al. suggest that forest soils are exposed directly, via atmospheric deposition, and indirectly, via canopy washoff, stemflow and litterfall, to atmospheric contamination. These characteristics, combined with their ability to retain persistent organic chemicals in their organic matter, make forest soils good candidates for atmospheric pollution monitoring.

Smith et al. present a thorough article in a few pages. While their writing style was very effective and concise, their paper could have been improved by better data presentation. Furthermore, the assumptions of long range transport to the experimental forest could have been better substantiated. Overall, I am intrigued to follow their research beyond this preliminary study.

Wania, Frank; Mackay, Donald, 1993. Global Fractionation and Cold Condensation of Low Volatility Organochlorine Compounds in Polar Regions. Ambio 22: 10-17.

Wania and Mackay compiled pesticide concentration data for Arctic and Antarctic air, snow and biota in an attempt to understand the chemical behavior of these pollutants in cold, arctic regions. In general, organochlorine contaminants show a relatively heterogeneous distribution in the Arctic, despite the lack of a nearby source. However, atmospheric concentration data suggest that the "most volatile constituents were preferentially transported to the Arctic". Deposition data, derived from ice cores, water samples and plant tissue, agree with this pattern. Researchers found more volatile compounds in higher concentrations at higher latitudes. Moreover, higher chlorinated congeners, which are heavier and less volatile, were found at higher concentrations in atmospheric fallout. The less chlorinated compounds, which tend to be more volatile, remained in the atmosphere longer. This discrepancy explains why more volatile compounds dominate contaminants in arctic areas distant from pollution sources. Animal tissue concentrations also displayed direct correlation between volatility and latitude. From these patterns, Wania and Mackay propose that in addition to relative location of pesticide emissions and transport pathways, the physical and chemical properties of these compounds contribute significantly to spatial distribution patterns. More specifically, temperature and volatility may be the most important factors determining pollutant composition and concentration in polar environments.

Wania and Mackay weave from the literature a convincing argument for global distillation, and call attention to the need to understand organochlorine behavior. The fate of the Inuit culture and the sensitive polar environment receive the attention they deserve. The authors carry their interest in organochlorine distribution to the need for international policy concerning volatile chemical use.

Welch, Harold E.; et al., 1991. Brown Snow: A Long Range Transport Event in the Canadian Arctic. Environmental Science and Technology 25: 280-286.

Welch et al. witnessed a long-range transport event that deposited four thousand tons of pesticide contaminated soil dust in the Keewatin District of the Canadian Arctic, leaving behind a distinct layer of brown snow. The authors analyzed contaminant levels, characterized soil particles and examined pollutants in sediment cores from two nearby lakes in an attempt to pinpoint the source of the brown snow. The brown snow contained substantial levels of both banned and common widely used pesticides including; lindane, pentachloranisole (PCA), PCBs, chlorobenzenes, polychlorinated camphenes (PCCs), chlordanes and DDTs. The brown snow pesticide concentrations fell within previously observed ranges, and corresponded well with contaminant levels in nearby lake sediments. When characterizing the soil dust, the authors found a mean particle size of approximately 1 um, and a composition consisting dominantly of illite and soot particles. Welch et al. combined this evidence with a back trajectory of the weather event which deposited the brown snow, to identify Asia as the most probable source of the contaminants. Furthermore, the authors estimated this single event may have been responsible for ten percent of the yearly contaminant deposition in the Keewatin area.

Welch et al. aptly employed several modern analytical techniques to investigate the mystery behind the brown snow. While their investigation was unable to definitively link the deposition event with its source, this study lead the way in investigations of this kind. Perhaps this type of investigation will lead to the ability to accurately identify pollution sources, and ultimately, help establish and enforce international pollution and pesticide restrictions.