Spatio-temporal variation of dissolved inorganic nutrients related to hydrodynamics and land use in the mangrove-fringed Segara Anakan Lagoon, Java, Indonesia

Segara Anakan is a mangrove-fringed lagoon in Java, Indonesia, which is affected by human activities in the lagoon and its hinterland. Nutrient and sediment input from the Citanduy River which drains an agriculture-dominated hinterland is thought to be an important factor for ecosystem degradation. From dry and rainy season investigations of dissolved inorganic nutrients between May 2004 and August 2006 we infer that the nutrient inventory of Segara Anakan is controlled by a complex mixture of anthropogenic and natural sources and processes. Maximum inputs into the western lagoon were supplied by the Citanduy during the rainy season while tidal exchange with the Indian Ocean dominated in the eastern lagoon with little freshwater input. During the dry season recycling in mangroves appeared to be an additional source of nutrients to the lagoon. Despite an extremely high population density and intensive agriculture in the hinterland nutrient pollution and eutrophication in the lagoon were low to moderate on a global scale. It is probably due to the short residence time of water in the shallow lagoon which indicates that major part of the land-derived nutrient input is rapidly exported to the sea. Although Segara Anakan is a highly perturbed system for decades, it appears that still natural processes exert major control on the nutrient inventory of the lagoon.     

Status, diversity and distribution patterns of mangrove vegetation in the Segara Anakan lagoon, Java, Indonesia

In the Segara Anakan lagoon, Java, 21 tree species and 5 understorey genera have been identified. Average tree density is 0.80 ± 0.99 Ind./m2 with 48.71% seedlings and an average basal area of 9.86 ± 10.54 cm2/m2. Tree density and diversity are high in the eastern part of the lagoon, located near the city of Cilacap. There, the dominant tree species are Aegiceras corniculatum, Nypa fruticans and Rhizophora apiculata, of which the two latter are characteristic for mature forests. By contrast, understorey species and the pioneer species (Avicennia alba, Aegiceras corniculatum and Sonneratia caseolaris) dominate the central lagoon where several rivers discharge. Compared to former studies, seedling density and tree diameter in the central lagoon has declined considerably and tree species dominance has changed. The high sedimentation rates and deforestation are likely to prevent the formation of a mature forest there. Tree communities are more equilibrated in the eastern lagoon which points to a more stable and less disturbed mangrove forest.     

Land use and land cover change affecting habitat distribution in the Segara Anakan lagoon, Java, Indonesia

This study quantifies and spatially characterizes land use and land cover changes in the Segara Anakan lagoon (SAL), Java, Indonesia, from 1987–2006. Classification of four satellite (SPOT) images from the years 1987, 1995, 2004 and 2006 and field ground truth data from 2004 and 2005 were used for map generation. The results show major changes in the western area of the SAL, with large area increases of rice fields, dry land agriculture, aquaculture and rural areas, and decreases in mangrove cover, mud flat and lagoon area. In the eastern area, minor decreases in mangrove area and increase in aquaculture, rural and industrial areas were also observed. Changes are due to the filling of the lagoon with riverine sediments derived from the hinterland and to mangrove conversion and resources exploitation. The results of this study provide basic information which is required for developing measures towards a sustainable management and conservation of the SAL.     

Conflicts between stakeholder groups affecting the ecology and economy of the Segara Anakan region

This study analyses how the conflict potential between different stakeholder groups is affecting the ecology and economy of the Segara Anakan region, a mangrove-fringed lagoon in central Java, Indonesia. The lagoon’s increasing sedimentation/silting up and the area’s expanding population has led to various interest groups conflicting with one another over how the resources of the lagoon and its surrounding area are to be utilized. Conflicts arise between occupational and ethnic groups in the lagoon’s bordering villages in the context of a transformation from fisheries to wetland agriculture. Land and mangrove use is therefore a cause for conflict between multiple groups, including Javanese fishermen, Sundanese farmers from Central and West Java and external shrimp farm owners. A result of the “Segara Anakan Development Project”—an 8-year undertaking that began in 1996—is that the lagoon was frequently dredged. Due to the dredging and resulting contamination of the land, a regional clash was triggered between Sundanese farmers and Javanese fishers. Our study reveals that the conflict potential between the various interest groups in the Segara Anakan Lagoon area could be reduced if the scarcity of natural resources were alleviated. Religious aspects also play a large role in marine resource utilization. Recognizing that the human utilization of natural resources is strongly symbolic and thereby culturally defined, we unravel the resource conflicts in our study area and offer some strategic approaches towards more sustainable outcomes.     

Spatio-temporal variation of macrobenthic communities in the mangrove-fringed Segara Anakan lagoon, Indonesia, affected by anthropogenic activities

The benthic macrofauna of the Segara Anakan lagoon, Java, Indonesia and its fringing mangroves were investigated between May 2004 and August 2006. This lagoon has been affected by various human activities for decades, in particular fishing, effluents from agriculture and industry, and illegal deforestation. In total, 163 taxa were identified, including 127 species occurring in the mangrove forest and 59 species in the subtidal. Mean density of macrobenthos was 2.5-fold higher in the central (881.8 ± 1,151.3 ind. m^?2) than in the eastern mangrove site (356.3 ± 218.8 ind. m^?2). Community structures differed significantly between these sites and showed a serial shift during the investigation period. Gastropods dominated the community in the central mangrove location, whereas sipunculids, polychaetes and gastropods had similar densities in the eastern site. Differences in community composition were best explained by three sediment properties: pore water salinity, δ¹³C_org, and C_org/N. It is suggested that small-scale heterogeneity of food availability and quality is a main factor determining the small-scale variability of the community composition. Compared to other Indo-West Pacific mangroves, species richness and densities are high. However, the dominance of specific taxa, especially of opportunistic species and the comparably low species richness in the subtidal of the lagoon may be attributed to the high sediment input by rivers in the central part and to the large-scale cutting of mangroves. Continuous tree logging will probably lead to a further spread of two fast growing understorey plants and thus to an increase of uniform swamp sites and a decrease of micro-habitats for benthic macrofauna. To our knowledge, this is the first detailed study on the spatio-temporal variation of benthic macrofauna in mangroves of Indonesia.     

Development of an environment-friendly feeding management for pond-reared fish species in the Segara Anakan Lagoon, Java, Indonesia

Inefficient feeding practices for producing fish in captivity create environmental problems. Therefore, the feed input should be reduced to a level that does not result in negative impacts of fish production. Reducing feed input can be done by periodic feed deprivation which does not necessarily decrease the fish production. This study was designed to investigate the effect of repeated unfed–fed cycles on the growth and feed utilization of the orange-spotted grouper Epinephelus coioides raised in floating net cages in estuarine ponds. The trial was conducted in the north east of Segara Anakan, Java, Indonesia. The fish were purchased from local fishermen and mean fish body weight was 53.2 g. After acclimation in the cages for 2 weeks, 500 fish were randomly assigned to four feeding groups. The groups included: fish fed daily as a control (C); fish not fed every Monday and Thursday and fed on Tuesday and Wednesday, then on Friday, Saturday and Sunday (T1); fish unfed every Sunday, Monday and Thursday and fed on Tuesday and Wednesday, then on Friday and Saturday (T2). The experiment ran for 10 weeks. The results showed that reducing feed input by repeating unfed–fed cycles induced compensatory growth of the fish. Application of this feeding regime provides flexibility in feeding management and may reduce organic discharge into the environment. Reduction of organic pollution should help the sustainable use and conservation of the Segara Anakan ecosystem.     

Widening the scope: linking coastal sedimentation with watershed dynamics in Java,Indonesia

Watershed processes and their effects on coasts are shaped by numerous interacting natural and societal factors. The knowledge of these factors and processes is often limited. This makes the field prone to politicisations with debates, research, and interventions being confined to a few selected factors. Debates on the causes of high river sediment loads and coastal sedimentation in Java have focussed on rainfed agriculture on peasants’ private lands, while other drivers have been neglected. This has undermined the effectiveness of watershed management. This paper links the sedimentation of the Segara Anakan lagoon on Java’s south coast with landscape characteristics and transformations in its catchment. Three-fourths of the lagoon have silted up since 1857/60. This is the result of a much broader range of drivers than commonly assumed to date. In addition to rainfed agriculture on peasants’ private lands, these drivers include coffee cultivation, timber extraction, plantation development, and in-migration in the late nineteenth and early twentieth century; erosion on contested state forest and plantation lands; state forest management practices; slope cuts to enlarge agricultural fields; agriculture in riparian zones; erosion from roads, trails, and settlements; river channel and floodplain modifications; and volcanic eruptions. The choice and expectations of societal responses aimed at reducing river sediment loads and coastal sedimentation hence need to be reconsidered, and related debates and research agendas must be broadened.

     

长江口南北支水沙特性观测研究

利用2009和2010年洪枯季、大小潮长江口南北支长时间序列的水沙盐观测资料,系统分析了近期南北支的水沙盐时空分布特征及南北支之间的关系,探讨了北支水沙盐倒灌,特别是泥沙倒灌对南支水域悬沙浓度的影响。分析结果表明:北支盐度和悬沙浓度年际、季节性及大小潮差异明显,一般大潮大于小潮,枯季大于洪季,平水年大于丰水年;南支受径流影响大,悬沙浓度均值在0.2kg/m3左右,盐度在0.25‰左右,南支悬沙浓度和盐度的大小均较北支小一个量级,其变化较北支复杂,尤其是在落潮时段盐度和悬沙浓度短时间内明显增加。北支作为河口唯一受潮汐控制的分支,水沙盐倒灌南支,倒灌期间南支悬沙浓度增加,洪季大潮有微弱沙量倒灌,悬沙浓度有0.05kg/m3的增幅,枯季大潮泥沙倒灌尤甚,南支悬沙浓度长时间维持在0.25kg/m3左右,最高可达0.62kg/m3。如上游径流量减小显著,则北支泥沙和盐水倒灌对南支的影响会增大。     

Changes in Vegetation Cover and Socio-Economic Transitions in a Coastal Lagoon (Kalametiya, Sri Lanka), As Observed by Teledetection and Ground Truthing, Can be Attributed to an Upstream Irrigation Scheme

According to some non-scholarly reports, Kalametiya lagoon (dry zone of southern Sri Lanka, formerly 8.9 km², now 7.5 km²) had been a moderately or high salinity water body and a very important centre of prawn fishery until the late 1960s. Most of the lagoon area had remained open water until then. An upstream irrigation project, the Udawalawa irrigation scheme, came into operation in 1967, increasing the freshwater inflow to the lagoon. The flora, fauna and water quality of the lagoon was reported to have changed since then.The lagoon now is a shallow coastal water body with low salinity water. More than 75% of the lagoon is covered by freshwater species or mangrove species characteristic for water with a low salinity: Eichhornia crassipes, Typha latifolia resp. Sonneratia caseolaris. There is actually no commercially important fishery in the lagoon.The present study was carried out to assess scientifically the said changes in the vegetation within a GIS, using aerial photographs taken in 1956 and 1994 and IRS IC, PAN+LISS III satellite images of 1997 in combination with ground surveys and information from a questionnaire-based survey.It appeared from this work that the aerial cover by Sonneratia caseolaris has increased by more than 30 times over the period from 1956 to the recent dates. Also, the lagoon area with open water has been drastically reduced during the same period as a result of spreading of freshwater and low salinity plant species. The results strongly suggest that the locally reported changes (fisheries decline, water salinity decrease) can be corroborated by the observed profound changes in plant cover and that upstream water works may have had strong impacts on this ecosystem, thus causing these changes.This study couples data obtained from retrospective aerial photograph series, from spaceborne imaging, from actual ground surveys and from questionnaires amongst elderly people to reconstruct decadal environmental change, thus attempting to fill the gap of lacking historical environmental data.     

Use of multitracers for the study of water mixing in the Paraíba do Sul River estuary

Multitracers were used to study water mixing in the Paraíba do Sul River estuary region in August 2007 (dry season) and March 2008 (rainy season) and to evaluate the reach of the river plume in the direction of the open ocean. Two sampling campaigns were carried out, each in a different season. Based on these results, it was possible to conclude that the multitracers used in this study (salinity, Si, Ba and U, as well as the radium isotopes ²²³Ra, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra) presented satisfactory results toward defining the plume reach and determining the residence time and water-mixing processes in the estuary. A strong correlation was observed between tracers and the distance to the coast. During the low river water discharge period, the riverine water took about 10 days to reach open ocean waters (salinity ∼ 35). During the rainy period this value decreased to 6 days. Based on the radium results, it was possible to calculate diffusion coefficients (K_h) of 23 km² d⁻¹ and 38 km² d⁻¹ for ²²⁴Ra and ²²³Ra, respectively, during the dry season (winter). Values of 65 km² d⁻¹ and 68 km² d⁻¹ for ²²³Ra and ²²⁴Ra, respectively, were found for the rainy period (summer).     

洞庭湖三口河系地区水环境演变趋势研究

三口河系是联系长江与洞庭湖的纽带，是洞庭湖区重要的组成部分。近年来，随着气候变化和人类活动影响加剧，江湖关系演变呈现出新的特征，三口河系地区水环境问题也日益突出。通过对该地区代表站南咀站和杨家垱站长系列水文水质资料监测数据的深入分析，从年际与年内两个尺度，系统探讨了三口河系地区水环境演变趋势。结果表明：洞庭湖三口河系地区水质在年际时间尺度上呈现逐渐恶化的趋势；年内TN、高锰酸钾指数表现为丰水期小，枯水期大，而TP表现为丰水期大，枯水期小的演变规律。然后从影响水量与水质两方面的因素，分析了该地区水环境演变的驱动机制，最后从水利工程的建设、面源污染控制以及法律法规与节水宣传等方面，初步构建了洞庭湖三口河系地区水环境调控策略     

River use profile of the Central Niger Delta based on traditional eco-livelihood knowledge (TELK)

The Central Niger Delta is made up of a network of rivers and creeks that constitute the inland surface waters. These surface waters have historically influenced settlement patterns and are of diverse use to residents of the Central Niger Delta. Surface water like many ecological system are complex, whose complexity has been associated with seasonal variability. Traditional knowledge (TK), traditional ecological knowledge (TEK) and the traditional eco-livelihood knowledge (TELK) of residents of four rural communities in the Central Niger Delta have been explored in developing a river use profile of rural communities of the Central Niger Delta. A questionnaire survey has been carried out in four communities, two each from the Otuoke and Kolo Creeks. The result shows that river use varies across seasons and affected by: physico-chemical water quality and characteristics of surface water; the hydrological characteristics; the biological/ecological characteristics; cultural use and demand; need for development projects; and access to this vital resource. Fishing constitute one of the major livelihood source in the Central Niger Delta and the TELK of fishers in the sample communities have specifically been explored to understanding fishing patterns across seasons. The five seasons identified from this study are: flood season; flood recession season; dry season; early rainy season; and rainy season. Therefore, the thesis of this paper is that there is the need to balance the current usage of surface water in the developing world such as the Central Niger Delta with the demand for development as well as future use if development is to meet the criteria for equitable development. The river use profile could be a promising tool in planning for equitable development.

Inverse modeling of Asian Rn flux using surface air Rn concentration

When used with an atmospheric transport model, the ²²²Rn flux distribution estimated in our previous study using soil transport theory caused underestimation of atmospheric ²²²Rn concentrations as compared with measurements in East Asia. In this study, we applied a Bayesian synthesis inverse method to produce revised estimates of the annual ²²²Rn flux density in Asia by using atmospheric ²²²Rn concentrations measured at seven sites in East Asia. The Bayesian synthesis inverse method requires a prior estimate of the flux distribution and its uncertainties. The atmospheric transport model MM5/HIRAT and our previous estimate of the ²²²Rn flux distribution as the prior value were used to generate new flux estimates for the eastern half of the Eurasian continent dividing into 10 regions.The ²²²Rn flux densities estimated using the Bayesian inversion technique were generally higher than the prior flux densities. The area-weighted average ²²²Rn flux density for Asia was estimated to be 33.0 mBq m⁻² s⁻¹, which is substantially higher than the prior value (16.7 mBq m⁻² s⁻¹). The estimated ²²²Rn flux densities decrease with increasing latitude as follows: Southeast Asia (36.7 mBq m⁻² s⁻¹); East Asia (28.6 mBq m⁻² s⁻¹) including China, Korean Peninsula and Japan; and Siberia (14.1 mBq m⁻² s⁻¹). Increase of the newly estimated fluxes in Southeast Asia, China, Japan, and the southern part of Eastern Siberia from the prior ones contributed most significantly to improved agreement of the model-calculated concentrations with the atmospheric measurements. The sensitivity analysis of prior flux errors and effects of locally exhaled ²²²Rn showed that the estimated fluxes in Northern and Central China, Korea, Japan, and the southern part of Eastern Siberia were robust, but that in Central Asia had a large uncertainty.     

长江口南槽中段枯季水沙输运特征研究

根据2015年1月7日至14日在长江口南槽中段主槽内获得的流速和悬沙观测资料,运用机制分解法分析了从大潮到小潮连续变化过程中南槽中段的水沙输运机制,通过小波分析方法探讨了悬沙浓度和流速的周期性对悬沙输运的影响。研究结果表明:(1)在一个大小潮周期过程中各潮周期的单宽净输水以向海为主,斯托克斯余流和欧拉余流的强度由大潮到小潮呈减小趋势;(2)各潮周期的单宽净输沙以向陆为主,与净输水方向相反,输沙强度从大潮至小潮呈现"小-大-小"的变化特征,该特征的产生与潮泵效应输沙的剧烈潮周期变化有关,平流输沙、潮泵效应输沙与垂向净环流输沙项是影响潮周期净输沙的主要成分;(3)小波分析表明,悬沙浓度和流速具有多个时间周期的变化,它们与水位的联合作用导致瞬时输沙率具有2个明显的时间周期变化。     

重庆市绵雨的分类与指标及其时空分布规律

按时间(季节)差异将重庆市绵雨划分为：春绵雨、初夏绵雨、盛夏绵雨、秋绵雨和冬绵雨5种。提出了重庆市绵雨的单站指标、区域指标和分区指标，进而全面分析了各季节绵雨的发生情况，揭示了重庆绵雨的时空分布规律。从季节来看，以秋绵雨最为突出，发生频率达77．9％，初夏次之，为59．6％，其它季节在30％左右；重绵雨和严重绵雨主要发生在秋季和初夏；其区域分布特征是，春季以东南部较多，盛夏分布差异相对较小，初夏、秋季和冬季都是西部和东南部多，东北部少。分别划分了各季节绵雨的分布类型变化趋势。     

Farming adaptation to environmental change in coastal Bangladesh: shrimp culture versus crop diversification

Farming in coastal Bangladesh includes rice/shrimp and rice/non-rice cropping systems. The former has been highly profitable but has exacerbated salinization of soil and water. We evaluate the relative profitability, riskiness, and sustainability of the two cropping systems, using data from two coastal villages in Khulna District. Shrimp cultivation was initially very rewarding. However, over 12–15 years, the cropping system experienced declining profitability, increased salinity, and adverse impacts on rice cropping and the local environment. From 2009, farmers adapted the system by changing the pond (gher) infrastructure, adopting delayed planting of a saline-tolerant rice cultivar, flushing out accumulated salt with freshwater during rice cropping, and allowing the soil to dry out after harvesting rice. The budgeting results show that with current management practices, the rice/shrimp system is economically more viable (higher returns to land and labour and less risky) than the rice/non-rice system. Soil analyses showed that while salinity was higher in the gher during the dry season, it was significantly reduced in the wet season and was very similar between the two systems (1–2 dS/m). Hence, as well as being more profitable and less risky, the rice/shrimp system may well be more sustainable than previously observed.     

Drought frequency in the Volta Basin of West Africa

According to various reports, climate change is responsible for the change in rainfall amount and pattern accompanied by the various degrees of extreme events in Sahelian West Africa in recent years. Other reports also suggest that there has been a “recovery” of the rainy season (Nicholson 2005). In this study, temporal characteristics of meteorological droughts in the Volta basin, a semi-arid region in West Africa, are investigated in order to provide a guide for sustainable water resource management. For this purpose, drought intensity, areal extent and recurrence frequency is analysed using the standardised precipitation index (SPI) for a time series between 1961 and 2005 from 52 meteorology stations across the Volta basin. Using this analysis the severity of the historical droughts of 1961, 1970, 1983, 1992 and 2001 that occurred in the region are assessed and their intensity, areal extent and return periods are obtained. The drought intensity is lower than −2.0 over nearly 75% of the region, meaning that a major part of the region was under extreme drought conditions during this year. The drought of 1983/1984 has a probability of occurrence of up to 0.1 from records spanning 44 years. The areal extent of extreme drought conditions is about 90% during this drought period.     

Exploring the fate,transport and risk of Perfluorooctane Sulfonate (PFOS) in a coastal region of China using a multimedia model

Perfluorooctane Sulfonate (PFOS) and related substances have been widely applied in both industrial processes and domestic products in China. Exploring the environmental fate and transport of PFOS using modeling methods provides an important link between emission and multimedia diffusion which forms a vital part in the human health risk assessment and chemical management for these substances. In this study, the gridded fugacity based BETR model was modified to make it more suitable to model transfer processes of PFOS in a coastal region, including changes to PFOS partition coefficients to reflect the influence of water salinity on its sorption behavior. The fate and transport of PFOS in the Bohai coastal region of China were simulated under steady state with the modified version of the model. Spatially distributed emissions of PFOS and related substances in 2010 were estimated and used in these simulations. Four different emission scenarios were investigated, in which a range of half-lives for PFOS related substances were considered. Concentrations of PFOS in air, vegetation, soil, fresh water, fresh water sediment and coastal water were derived from the model under the steady-state assumption. The median modeled PFOS concentrations in fresh water, fresh water sediment and soil were 7.20 ng/L, 0.39 ng/g and 0.21 ng/g, respectively, under Emission Scenario 2 (which assumed all PFOS related substances immediately degrade to PFOS) for the whole region, while the maximum concentrations were 47.10 ng/L, 4.98 ng/g and 2.49 ng/g, respectively. Measured concentration data for PFOS in the Bohai coastal region around the year of 2010 were collected from the literature. The reliability of the model results was evaluated by comparing the range of modeled concentrations with the measured data, which generally matched well for the main compartments. Fate and transfer fluxes were derived from the model based on the calculated inventory within the compartments, transfer fluxes between compartments and advection fluxes between sub-regions. It showed that soil and costal water were likely to be the most important sinks of PFOS in the Bohai costal region, in which more than 90% of PFOS was stored. Flows of fresh water were the driving force for spatial transport of PFOS in this region. Influences of the seasonal change of fresh water fluxes on the model results were also analyzed. When only seasonal changes of the fresh water flow rates were considered, concentrations of PFOS in winter and spring were predicted to be higher than that under annual average conditions, while the concentrations in summer and autumn were lower. For PFOS fluxes entering the sea, opposite conclusions were drawn compared to the concentrations. Environmental risks from the presence of PFOS in fresh water were assessed for this region through comparison with available water quality criteria values. The predicted concentrations of PFOS in the Bohai coastal region provided by the model were lower than the water quality criteria published by the United States Environmental Protection Agency and Chinese researchers, while the concentrations in more than 80% of the sampling locations exceeded the European Union Water Framework Directive Environmental Quality Standards values. Seasonal variations of flow rate might cause a significant increase in environmental risks.     

Fate,distribution, and contrasting temporal trends of perfluoroalkyl substances (PFASs) in Lake Ontario,Canada

Lake Ontario water and sediment collected from tributary, nearshore, and open lake sites were analyzed for perfluoroalkyl substances (PFASs), namely perfluoroalkyl carboxylic acids (PFCAs, F(CF₂)_nCO₂⁻; n = 6-11,13) and perfluoroalkane sulfonic acids (PFSAs, F(CF₂)_nSO₃⁻; n = 6,8,10). Survey results of surface sediment and water indicated that shorter chained PFASs were predominant in and near urban/industrial area watersheds, while longer chained PFASs were predominant in fine-grained sediment from major depositional basins. Niagara River suspended solids (1981–2006) demonstrated temporal trends that may have been influenced by recent changes in North American production and use of PFASs. Perfluorooctane sulfonate (PFOS) reached a peak concentration in 2001 of 1.1 ng/g, followed by a decrease from 2001 to 2006 (half-life = 9 years). Perfluorooctanoic acid (PFOA) increased from 2001 to 2006 (doubling time = 2 years) reaching a peak concentration of 0.80 ng/g. In contrast, three sediment cores from western, central, and eastern Lake Ontario showed increasing temporal trends to surface sediment for all PFASs. PFOA and PFOS concentrations increased from 1988 to 2004 (doubling time = ~ 4 years) in the western Lake Ontario core. The observed variations in temporal trends from different environmental compartments may be a result of the physico-chemical properties of PFASs, ongoing emissions, and the environmental transformation and degradation of PFAS precursor compounds.